Improved heat storage

Abstract

A thermal storage body (10) for an energy storage system, the thermal storage body (10) comprising an inner container (40) housing a thermal energy storage body (14) and an outer container (50) surrounding the inner container (40), the inner and outer containers (40, 50) being separated by a vacuum region (11) extending therebetween.

Description

[Technical field]

[0001] The present invention relates to a thermal store for an energy storage system and to an energy storage system comprising a thermal store. The present invention also relates to an electrical installation for a building comprising an energy storage system. [Background technology]

[0002] The rise of renewable electricity generation requires a more flexible electricity demand to ensure a good match between generation and demand. In many countries, the demand for heat is the largest amount of energy needed, so thermal stores that are electrically heated before being used can greatly increase demand flexibility.

[0003] A practical heat store requires a sensible (i.e. non-phase-changing) heat store, which can be either solid or liquid. Solid sensible heat stores use a material that remains solid when heat is added (or removed), so that thermal energy is stored only by temperature change. In the case of liquid sensible heat stores, energy is stored in the liquid material by temperature change. In either case, the solid or liquid material does not undergo a phase change. Water stores are one of the most popular types of liquid sensible heat stores, and at high temperatures, molten salts are used as liquid sensible heat stores in concentrated solar power plants.

[0004] Water has one of the highest heat capacities per unit weight, at 4.2 J / kg K, but the temperature band is narrow and can be used economically before requiring expensive pressure vessels. Solid materials have lower heat capacities (e.g. basalt at 0.8 J / kg K or steel at just 0.45 J / kg K) but can generally be heated to higher temperatures, e.g. above 200°C and even up to 400°C in some cases.

[0005] A dry core boiler is a thermal storage device that has been used in homes to provide hot water for wet heating systems or for domestic use such as showers and baths. A dry core boiler contains multiple dense bricks held in close proximity to an electric heater. Electricity is passed through the heater during off-peak hours and used to heat the bricks to high temperatures, which can be as high as 650 or 700°C. The bricks are surrounded by high temperature insulation to minimize heat loss. When hot water is needed, a fan blows air over the top of the bricks, heating the air to a high temperature. This heated air is then passed through a heat exchanger that is outside the hot space. The heat exchanger transfers heat from the hot air to the water. The air is then channeled back into the hot space where it is heated again. This design of the thermal storage system separates the water circuit from the heat storage material using air as the working fluid.

[0006] Dry core boilers have several disadvantageous features. The first is that heat losses at these high temperatures and small sizes are significant. This is even when high temperature insulation such as microporous insulation is used. The second disadvantageous feature is that high temperature insulation is expensive, and if losses are reduced by thickening the insulation, the cost of insulation becomes substantial. The third disadvantageous feature is that air at atmospheric pressure has a low heat capacity, so when it is heated to high temperatures, its density drops by a factor of three, further reducing its heat capacity. This results in large volumes of air flowing through the bricks and heat exchangers when high power output is required. Dry core boilers also need to be assembled on-site by an engineer and cannot be easily moved without disassembly and reassembly.

[0007] Recently, in US Patent Publication 2005 / 0133963, the inventors proposed a heat storage material made of a metal (e.g., aluminum alloy) / rock composite, which has high thermal conductivity and high energy density. It is easy to heat using an embedded electric heater, and the heat can be removed by a steel coil heat exchanger embedded in the metal / rock material. Other solid sensible heat storage materials that have been proposed include cast iron or refractory materials, such as ferric oxide and concrete.

[0008] An example of an improvement to the dry core boiler was proposed in the late 1960s and early 1970s, which involved direct heat exchange from the hot core to a water / steam circuit. An example of this is disclosed in US Pat. No. 5,399,363, which focuses on providing a system for controlling water temperature and quality, as well as a method for extracting heat directly from the hot core using water / steam. From a practical standpoint, the proposed invention as detailed was difficult to make work safely and nearly impossible to certify. In particular, US Pat. No. 5,399,363 proposes a system in which the saturation pressure of the steam controls the water level in the supply vessel. As heat is extracted from the system, the steam pressure drops and the water level in the supply vessel rises, allowing water to be supplied at atmospheric pressure to pipes located in the hot core. This water then boils and turns to steam, increasing the pressure while lowering the water level in the supply vessel.

[0009] Some key issues with this system are that the flow is very unstable. When water is added to the hot pipe, it can boil and go through different boiling regimes with very different heat transfer rates. This can cause a sudden increase in steam volume and a sudden change in pressure. The effects of these pressure surges have almost certainly caused the system to be unstable and therefore unmanageable. It also does not respond well to sudden changes in load and is unlikely to provide high power output because it needs to produce significant heat transfer in a short period of time. Additionally, failure modes can be dangerous because the system requires too much water in the heating circuit and the system is limited to small pressure differentials due to the concomitant height of the water column. Small pressure differentials impractically require large pipe diameters for the steam to flow and large areas for heat exchange to occur.

[0010] It is an additional advantage to distribute the heat stores in discrete locations around a typical electricity distribution network (including the grid), where the demand for the stored heat is needed, for example in a heat network for a home or a commercial establishment or for a block of apartments. This is because it is much easier and cheaper to transport electricity than heat. However, storing high-temperature heat in small volumes has an efficiency penalty due to heat losses. High temperature differences deliver high heat fluxes through standard types of insulation. The proportion of losses in small volumes is significant compared to the stored energy, and these heat losses are typically as high as 70% per 24 hours. It is therefore desirable to provide a system that limits the heat losses to, for example, less than 10% per 24 hours.

[0011] Vacuum insulation uses very little space, but can reduce heat transfer from inside the container to very low levels. Vacuum insulation has been used for decades in cryogenic liquid applications where liquids (e.g., liquid nitrogen) need to be stored at very low temperatures for long periods of time. However, vacuum insulation techniques known in the art rely on achieving and maintaining a vacuum pressure, which is generally not achievable in domestic equipment. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] International Publication No. 2020 / 217045 [Patent Document 2] UK Patent Application Publication No. 1323522 Summary of the Invention

[0013] The present application has identified a need for an improved thermal storage (and related systems) that overcomes, or at least mitigates, problems associated with the prior art. According to a first aspect of the present invention there is provided a thermal store for an energy storage system comprising an inner container housing a thermal energy store (e.g. a thermal mass) and an outer container surrounding the inner container, the inner and outer containers being separated by a vacuum region extending between them.

[0014] In this way, a high temperature thermal store can be provided using a (e.g. solid) thermal store surrounded by vacuum insulation, providing the opportunity for a low cost thermal store with low heat loss even though the thermal storage occurs at medium to high temperatures.

[0015] In one embodiment, the vacuum region has a vacuum pressure (eg, a partial vacuum pressure). In one embodiment, the vacuum pressure is between 0.05 mbar and 1 mbar. In one embodiment, the thermal reservoir comprises a vacuum pump (eg, an integral vacuum pump) operable to maintain a vacuum pressure (eg, a partial vacuum pressure) in the vacuum region.

[0016] In one embodiment, the vacuum pump maintains the vacuum pressure at a level between 0.05 mbar and 1 mbar. In one embodiment, the thermal store includes a sensor operable to measure a parameter (e.g. pressure and / or temperature (e.g. surface temperature)) at one or more locations within the thermal store, and the vacuum pump is configured to operate whenever the sensor indicates that the parameter reaches a predetermined value (e.g. pressure drops below / temperature rises above). In this way, the thermal store is provided with vacuum insulation and requires only intermittent operation of the vacuum pump.

[0017] In one embodiment, the thermal store further includes an integral vacuum valve operable to connect a vacuum pump to the vacuum zone. In one embodiment, the thermal store is further provided with insulation within the vacuum area, in this way the vacuum level required to achieve the desired degree of insulation can be reduced.

[0018] In one embodiment, the insulation is wrapped around the outer wall of the inner container (e.g., substantially covers the outer surface of the inner container), in this way the insulation can function as a microporous insulator only in the direction perpendicular to the side of the inner container.

[0019] In one embodiment, the insulation comprises a multi-layer insulation of n layers. In one embodiment, each layer of the multi-layer insulation includes a reflective layer and a spacer layer. In one embodiment, n > 50 (such as n > 100, such as n > 150).

[0020] In one embodiment, n is about 200 (eg, n is approximately 200). In one embodiment, the insulation comprises at least 10 layers of multilayer insulation per 100 degrees Celsius temperature difference across the vacuum region (i.e., n>50 when the temperature difference is 500 degrees Celsius), at least 20 layers of multilayer insulation per 100 degrees Celsius temperature difference across the vacuum region (i.e., n>100 when the temperature difference is 500 degrees Celsius), or at least 40 layers of multilayer insulation per 100 degrees Celsius temperature difference across the vacuum region (i.e., n>200 when the temperature difference is 500 degrees Celsius). That is, in one embodiment, ΔT / n≦10, in another embodiment, ΔT / n≦5, and in another embodiment, ΔT / n≦2.5, where ΔT is the temperature across the vacuum region in degrees Celsius (i.e., the temperature difference between the inner wall of the outer container and the opposing outer wall of the inner container).

[0021] In one embodiment, the average (mean) spacing between the reflective layer and the spacer layer in each layer of the multi-layer insulation is less than 1 mm (eg, less than 0.5 mm, such as less than 0.2 mm).

[0022] In one embodiment, the average spacing between the reflective layer and the spacer layer in each layer of the multi-layer insulation varies from layer to layer. In one embodiment, the spacing between the reflective layer and the spacer layer in each layer of the multi-layer insulation is between 1 mm and 0.01 mm.

[0023] In one embodiment, the reflective layer is a reflective metal sheet (eg, an aluminum sheet). In one embodiment, the spacer layer is a thin fiberglass layer or a thin ceramic fiber (eg, ceramic fiber paper) layer.

[0024] In one embodiment, the thermal store includes one or more heating elements (eg, electric heating elements) operable to act as a heat source for input to the thermal energy store. In one embodiment, the electric heating body comprises an electric heating coil means (eg an electric heating coil).

[0025] In one embodiment, the thermal reservoir includes one or more heat exchangers (eg, direct heat exchangers) operable to receive a heat transfer fluid. In one embodiment, the heat transfer fluid is water.

[0026] In one series of embodiments, the thermal energy storage body is a solid state storage body. In one embodiment, one or more heating elements (eg, electric heating elements (eg, electric heating coil means)) are embedded in the solid reservoir.

[0027] In one embodiment, the one or more heat exchangers are embedded in the solid reservoir. In one embodiment, the thermal energy storage body comprises a solid body comprising a solid thermally conductive matrix having a solid thermal filler material embedded therein, the solid thermally conductive matrix forming a thermally conductive pathway to the solid thermal filler material dispersed within the solid thermally conductive matrix.

[0028] In one embodiment, one or more heating elements (eg, electric heating elements (eg, electric heating coil means)) are embedded in a solid thermally conductive matrix. In one embodiment, the one or more heat exchangers are embedded in a solid thermally conductive matrix.

[0029] In one embodiment, the thermal store is in the form of a thermal energy store that heats up to a temperature above 300° C. (eg, and maintains this temperature until the release phase). In another set of embodiments, the thermal energy store is a fluid (eg liquid) store that includes a chamber for receiving a thermal storage fluid (eg a thermal storage liquid).

[0030] In one embodiment, one or more heating elements (eg, electric heating elements (eg, electric heating coil means)) extend into the chamber. In one embodiment, the one or more heat exchangers extend into the chamber.

[0031] In one series of embodiments, the inner container is suspended within the outer container. In one embodiment, the inner container is suspended by a (eg, single) neck connector (eg, a structurally loaded neck connector) that connects the upper section of the inner container to the upper section of the outer container.

[0032] In one embodiment, no part of the inner container touches the outer container. In one embodiment, the neck connector supports the weight of the inner container and the thermal energy storage body.

[0033] In one embodiment, the neck connector includes a central chamber that houses supply lines for the thermal energy storage body, such as supply lines for one or more heating elements (e.g., electrical cables for one or more electric heating elements) and fluid transport pipes for one or more heat exchangers (e.g., inlet and outlet pipes).

[0034] In one embodiment, the outer container (eg, an upper section of the outer container) includes a (eg, first) aperture (eg, a sealable aperture) for receiving an end (eg, an upper end) of the neck connector.

[0035] In one embodiment, the inner container (eg, an upper section of the inner container) includes a (eg, second) aperture (eg, a sealable aperture) for receiving an end (eg, a lower end) of the neck connector.

[0036] In one embodiment, the neck connector further includes an inner (eg, lower) neck plate coupled to the inner container. In one embodiment, the neck connector further includes an outer (eg, upper) neck plate coupled to the outer container.

[0037] In another set of embodiments, the inner container is supported by a (eg, single) neck connector (eg, a structurally loaded neck connector) that connects the lower section of the inner container to the lower section of the outer container.

[0038] In one embodiment, no part of the inner container touches the outer container. In one embodiment, the neck connector supports the weight of the inner container and the thermal energy storage body.

[0039] In one embodiment, the neck connector includes a central chamber that houses supply lines for the thermal energy storage body, such as supply lines for one or more heating elements (e.g., electrical cables for one or more electric heating elements) and fluid transport pipes for one or more heat exchangers (e.g., inlet and outlet pipes).

[0040] In one embodiment, the outer container (eg, a lower section of the outer container) includes a (eg, first) aperture (eg, a sealable aperture) for receiving an end (eg, a lower end) of the neck connector.

[0041] In one embodiment, the inner container (eg, a lower section of the inner container) includes a (eg, second) aperture (eg, a sealable aperture) for receiving an end (eg, an upper end) of the neck connector.

[0042] In one embodiment, the neck connector further includes an inner (eg, upper) neck plate coupled to the inner container. In one embodiment, the neck connector further includes an outer (eg, lower) neck plate coupled to the outer container.

[0043] In one embodiment, the outer container has an interface for engaging a transport device. In one embodiment, the interface includes one or more sockets disposed on the outer container, the one or more sockets configured to receive shipping bolts (eg, shipping threaded bolts) disposed on the transportation device.

[0044] In one embodiment, the interface includes multiple sockets (eg, three or more sockets). In one embodiment, the multiple sockets are evenly spaced around the outer container.

[0045] In one embodiment, the thermal storage body further includes one or more spreader plates movable between an inoperative position and a deployed position, where in the deployed position the spreader plates are operable to inhibit movement of the inner container relative to the outer container.

[0046] In one embodiment, the spreader plates are engaged by a shipping bolt and move from an inoperative position to a deployed position when the shipping bolt is fully inserted into one or more sockets.

[0047] In the case of a thermal storage body including insulation provided in a vacuum region (e.g., n-layer multi-layer insulation provided in a vacuum region), the spreader plate may be operable in the deployed position to compress the insulation against the inner container (e.g., compress the n-layer multi-layer insulation) to inhibit movement of the inner container relative to the outer container.

[0048] In one embodiment, the one or more sockets include a pair of sockets disposed on opposing lateral sides of the outer container. In one embodiment, the thermal storage body includes a pair of spreader plates disposed on opposite lateral sides of the outer vessel.

[0049] In one embodiment, the thermal store further comprises a sealing member (eg, a sealing bolt) operable to seal the one or more sockets in the non-transport mode. In one embodiment, the spreader plate is free to move horizontally but is constrained vertically (e.g., by one or more straps attached to the outer container) so that the spreader plate remains substantially aligned with the socket.

[0050] In one embodiment, the inner container comprises a two-part structure (eg, an upper inner container structure and a lower inner container structure). In one embodiment, the outer container comprises a two-part structure (eg, an upper outer container structure and a lower outer container structure).

[0051] In one embodiment, the thermal storage body further includes an internal brace disposed within the vacuum region, the internal brace configured to engage an inner surface of the outer vessel and resist compression of the outer vessel.

[0052] In this manner, a vacuum insulated container with a relatively thin outer container wall may be provided with the ability to withstand compressive forces generated by negative pressure within the container and / or to resist external pressures / influences.

[0053] In one embodiment, the inner surface of the outer container has a generally cylindrical profile. In one embodiment, the internal brace has a generally annular profile when viewed along a longitudinal axis of the internal brace.

[0054] In one embodiment, no portion of the internal brace contacts the inner vessel. In one embodiment, the internal brace is configured (eg, during manufacture) to be slidably insertable into a vacuum region.

[0055] In one embodiment, the internal brace is manufactured from a single piece (eg, a one-piece section). In one embodiment, the internal brace is a radially (eg, circumferentially) expandable brace (eg, expandable between a radially contracted configuration and a radially expanded configuration).

[0056] In one embodiment, the radially expandable brace is biased (eg, resiliently biased) into the expanded configuration. In one embodiment, the radially expandable brace is configured to preload (tension) the inner surface of the outer container (i.e., the inner surface of the outer container is continuously tensioned).

[0057] In an alternative embodiment, the internal brace (e.g., a brace that is radially expandable to a radially expanded configuration) may fit snugly within the inner surface of the outer container (e.g., with only the inner surface of the outer container being under tension in response to a compressive displacement of the inner surface of the outer container).

[0058] In one embodiment, the radially expandable brace includes a radially expandable cage structure. In one embodiment, the radially expandable brace is a torsion brace configured to be urged to expand radially when under tension (e.g., urged to expand radially when a torsion is applied in a first direction and urged to contract radially when a torsion is applied in a second, opposite direction).

[0059] In one embodiment, the torsion brace includes a cage or coil structure. In one embodiment, the torsion brace includes a helical coil structure. In one embodiment, the helical coil structure is a substantially continuous helical coil structure or a structure including a series of connected helical coil sections (e.g., helical coil sections connected in series by torsional transfer connections (e.g., coiled or non-coiled torsional transfer connections)).

[0060] In one embodiment, the torsion brace imparts a twist to the inner surface of the outer container (eg, inserted into the vacuum region in a twisted configuration or twisted after insertion into the vacuum region).

[0061] In one embodiment, the vacuum insulated container includes an additional internal brace disposed within the inner container, the additional internal brace configured to engage an inner surface of the inner container and resist compression of the inner container (e.g., during manufacturing and while testing the inner container).

[0062] In one embodiment, the further internal brace is according to any embodiment of the internal brace of the first definition defined above (eg a torsion brace including a helical coil structure). According to a second aspect of the present invention there is provided an energy storage system comprising a thermal store according to the first aspect of the present invention (eg according to any embodiment of the first aspect of the present invention).

[0063] According to a third aspect of the present invention, there is provided an energy storage system comprising a thermal energy store (e.g. a thermal mass), a primary circuit (e.g. a steam circuit) comprising a first heat transfer fluid, an evaporator heat exchanger stage configured to receive thermal energy from the thermal energy store and evaporate the first heat transfer fluid in liquid form into a gas stream, a condenser heat exchanger stage configured to condense the gas stream received from the evaporator heat exchanger stage, and a secondary circuit (e.g. a non-steam circuit) comprising a second heat transfer fluid, the secondary circuit configured to receive thermal energy from the primary circuit via the condenser heat exchanger stage and supply the received thermal energy to a heating system (e.g. a hot water / central heating system).

[0064] In one embodiment, the first heat transfer fluid is water (eg, pure water). In one embodiment, the second heat transfer fluid is water (eg, water and antifreeze). In one embodiment, the secondary circuit is configured to maintain the second heat transfer fluid as a liquid throughout all stages.

[0065] In one embodiment, the primary circuit includes a pressure increasing device (e.g., an injector pump) operable to pressurize fluid received from the condenser heat exchanger stage and deliver the fluid at increased pressure to the evaporator heat exchanger stage. In this manner, a water / steam system may be provided with a pump that injects water at high pressure into the evaporator heat exchanger stage, where the steam is condensed in the condenser heat exchanger stage, after which the water is pumped back at high pressure.

[0066] In one embodiment, the pressure output of the pressure increase device is above atmospheric pressure (eg at least 0.5 bar, such as at least 1 bar, such as at least 2 bar). In one embodiment, the pressure increase device is a positive displacement device.

[0067] In one embodiment, the pressure increase device is a variable flow device (eg, a variable flow pump). In one embodiment, the pressure boost device is a variable speed positive displacement pump. In this way, the mass flow of the first heat transfer fluid is proportional to the velocity, regardless of the delivery pressure.

[0068] In one embodiment, the flow rate of a pressure boost device (eg, a variable flow pump) is varied to achieve a target temperature located within the energy storage system. In one embodiment, the location is a location in a secondary circuit.

[0069] In one embodiment, the location is between the heating system and the condenser heat exchanger stage (eg, the temperature of the second heat transfer fluid as it exits the condenser heat exchanger stage). In one embodiment, the primary circuit further includes a desuperheater operable to cool (eg, and partially condense) gas flowing from the evaporator heat exchanger stage to the condenser heat exchanger stage.

[0070] In one embodiment, the desuperheater includes an outlet operable to spray a fluid (eg, a first heat transfer fluid) onto gas flowing from the evaporator heat exchanger stage to the condenser heat exchanger stage.

[0071] In one embodiment, the desuperheater is operable to divert a portion of the first heat transfer fluid flowing from the pressure increase device to the evaporator heat exchanger stage. In one embodiment, the desuperheater includes a selectively connectable flow path including a desuperheater valve positioned between the pressure increase device and the evaporator heat exchanger stage, and a pipe carrying the first heat transfer fluid stream from the desuperheater valve to an outlet between the evaporator heat exchanger stage and the condenser heat exchanger stage.

[0072] In one embodiment, the desuperheater includes a permanently connected flow path including a fine pipe positioned between the pressure booster and the evaporator heat exchanger stage. In one embodiment, the primary circuit further includes a reservoir.

[0073] In one embodiment, the reservoir is positioned between the condenser heat exchanger stage and the pressure increase device. In one embodiment, the reservoir is sized such that excess first heat transfer fluid in the primary circuit is minimized when the energy storage system is operating at full power.

[0074] In one embodiment, the first heat transfer fluid condensed by the condenser heat exchanger stage flows under gravity into the reservoir. In one embodiment, the first heat transfer fluid flows under gravity from the reservoir to the pressure increase device.

[0075] In one embodiment, the primary circuit includes a high pressure pipe extending between the pressure boost device and the evaporator heat exchanger stage. In one embodiment, the high pressure pipe has a section that extends above the height of the reservoir (e.g., a section that extends between the desuperheat valve, if present, and the evaporator heat exchanger stage), in this way, the first heat transfer fluid entering the reservoir can only flow towards the evaporator heat exchanger stage when the pressure increase device is operable.

[0076] In one embodiment, the primary circuit includes a shutoff valve that prevents flow from the reservoir to the evaporator heat exchanger stage. In one embodiment, the energy storage system is configured to heat the thermal energy storage body to a temperature of greater than 100°C (e.g., greater than 200°C, such as greater than 300°C, such as greater than 400°C, such as greater than 500°C, such as greater than 600°C).

[0077] In one embodiment, the energy storage system is configured to heat the thermal energy store to a temperature of more than 100°C (e.g., to a temperature of more than 200°C, such as to a temperature of more than 300°C, such as to a temperature of more than 400°C, such as to a temperature of more than 500°C, such as to a temperature of more than 600°C) and less than 700°C.

[0078] In one embodiment, the energy storage system is configured to heat the thermal energy store to a temperature in the range of 100-600° C. (eg, in the range of 200-500° C.). In one embodiment, the evaporator heat exchanger stage includes a pipe circuit extending through or around the thermal energy storage body, where the pipe circuit has an inlet (e.g., a water inlet) and an outlet (e.g., a steam outlet). In the case of a pipe circuit embedded in the solid storage body, the inlet and outlet correspond to the points where the pipe circuit enters and exits the solid storage body.

[0079] In one embodiment, the primary circuit (e.g. pressure booster and / or evaporator heat exchanger stage) is configured to generate a gas flow of the first heat transfer fluid at the outlet, the gas flow velocity being at least 100 km / h (e.g. at least 200 km / h, e.g. at least 300 km / h). Advantageously, this high velocity gas (e.g. steam) output allows the use of a pipe circuit with small pipes, generating large pressure drops and high heat transfer rates, while also minimizing the volume of fluid in the pipe circuit, thereby increasing safety. Furthermore, when the volume of the pipe circuit is below 2 liters, the certification and maintenance regime is very simple, which is economically attractive for the customer.

[0080] In one embodiment, the primary circuit (eg, a pressure boost device) is configured to supply a first heat transfer fluid to the inlet at a predetermined maximum injection rate P. In one embodiment, the pipe circuit has an effective internal cross-sectional area A. In a single pipe circuit, the effective internal cross-sectional area A is the average cross-sectional area of ​​a single pipe. In a pipe circuit containing multiple parallel pipes, the effective internal cross-sectional area A is the combined average cross-sectional area of ​​the multiple pipes.

[0081] In one embodiment, the ratio of the effective internal cross-sectional area A of the pipe circuit to the predetermined maximum injection rate P (i.e., A / P) is less than 20 (e.g., less than 16, e.g., less than 12). Thus, for every 1 g / s of liquid injected, the effective internal cross-sectional area A of the pipe circuit is less than 20 mm 2 Less than (e.g. 16mm 2 Less than, for example, 12 mm 2 (less than 200 mm2) i.e., for a predetermined maximum injection rate P of 10 g / s, the effective internal cross-sectional area A of the pipe circuit is 200 mm2 2 Less than (e.g. 160mm 2 Less than, for example, 120 mm 2 (less than)

[0082] In one embodiment, the effective length of the pipe circuit is greater than 5m (eg greater than 7m, such as greater than 10m). In one embodiment, the effective internal cross-sectional area of ​​the pipe circuit is 500 mm2 Less than (e.g. 250mm 2 Less than, for example, 150 mm 2) It is.

[0083] In one embodiment, the internal volume of the pipe circuit is less than 2 liters. In one embodiment, the primary circuit (e.g., pressure booster) is configured to vary the inlet pressure with respect to the temperature of the thermal energy store (e.g., to reduce the inlet pressure (e.g., proportional to the decrease in temperature) if the temperature of the thermal energy store drops below a predetermined maximum temperature). In this way, undesirable overloading of the evaporator heat exchanger stage when the temperature of the energy store drops below the peak temperature can be avoided.

[0084] In one embodiment, the condensing heat exchanger stage is a plate heat exchanger. In one embodiment, the secondary circuit includes a diverter valve operable when activated to divert the flow of the second heat transfer fluid away from the heating system (eg, to bypass the heating system).

[0085] In one embodiment, the secondary circuit includes a circulation pump. In one embodiment, the circulation pump is provided between the condenser heat exchanger stage and the diverter valve (eg, between the condenser heat exchanger stage and the expander).

[0086] In one embodiment, the secondary circuit is pressurized (eg, to about 1 bar). In one embodiment, the secondary circuit includes an expander (eg, an expansion vessel) operable to maintain a predetermined level of pressurization within the secondary circuit.

[0087] In one embodiment, the energy storage system is further capable of operating in a power outage mode (eg, when the power supply to the system is interrupted). In one embodiment, the secondary circuit further includes a backup power source (e.g., a battery) configured to maintain operation of the secondary circuit circulation pump in a power failure mode until all of the vapor phase of the first heat transfer fluid in the primary circuit is safely condensed. In this manner, the need to vent vapor during shutdown is advantageously avoided.

[0088] In one embodiment, the secondary circuit includes a buffer reservoir. In one embodiment, the buffer reservoir is operable to hold a sufficient mass of the second heat transfer fluid to absorb all of the heat from the heat transfer fluid in the primary circuit when condensing.

[0089] In one embodiment, the pressure boost device is inoperable in a power failure mode. In one embodiment, the energy storage system includes one or more heating elements (eg, electric heating elements) operable during the charging phase of the energy storage system to serve as a heat input to the thermal energy storage.

[0090] In one embodiment, the electric heating body comprises an electric heating coil means (eg an electric heating coil). In one embodiment, the thermal energy storage body is a solid state storage body. In one embodiment, one or more heating elements (eg, electric heating elements (eg, electric heating coil means)) are embedded in the solid reservoir.

[0091] In one embodiment, the evaporator heat exchanger stage includes a direct heat exchanger. In one embodiment, the evaporator heat exchanger stage (eg, a direct heat exchanger) is embedded in the solid reservoir.

[0092] In one embodiment, the thermal energy storage body includes a solid body including a solid thermally conductive matrix in which a solid thermal filler material is embedded, the solid thermally conductive matrix forming a thermally conductive pathway to the solid thermal filler material dispersed within the solid thermally conductive matrix.

[0093] In one embodiment, one or more heating elements (e.g., electric heating elements (e.g., electric heating coil means)) are embedded in a solid thermally conductive matrix and are operable to serve as a heat input during the charging phase of the energy storage system.

[0094] In one embodiment, the evaporator heat exchanger stage (eg, a direct heat exchanger) is embedded in a solid thermally conductive matrix. In one embodiment, the energy storage system is operable during a charging mode in which heat is transferred to a thermal energy storage body (eg, by passing an electrical current through a heating body).

[0095] In one embodiment, the energy storage system is operable during a discharge mode to transfer heat from the thermal energy storage body to a first heat transfer fluid via an evaporator heat exchanger stage, and to transfer thermal energy from the first transfer fluid to a secondary circuit via a condenser heat exchanger stage.

[0096] In one embodiment the thermal energy store is part of a thermal store according to the first, ninth, eleventh or thirteenth aspect of the invention (e.g. according to an embodiment of any of the first, ninth, eleventh or thirteenth aspect of the invention) and / or comprises a vacuum insulated container according to the sixth or fifteenth aspect of the invention (e.g. according to an embodiment of any of the sixth or fifteenth aspect of the invention).

[0097] According to a fourth aspect of the present invention, there is provided a method of operating an energy storage system comprising a thermal energy store (e.g. a thermal mass), a primary circuit (e.g. a steam circuit) comprising a first heat transfer fluid, an evaporator heat exchanger stage configured to receive thermal energy from the thermal energy store and evaporate the first heat transfer fluid in liquid form to form a gas stream, a condenser heat exchanger stage configured to condense the gas stream received from the evaporator heat exchanger stage, and a secondary circuit (e.g. a non-steam circuit) comprising a second heat transfer fluid, the secondary circuit receiving thermal energy from the primary circuit via the condenser heat exchanger stage and configured to supply the received thermal energy to a heating system (e.g. a hot water / central heating system). and, in a discharge mode, evaporating a liquid phase of a first heat transfer fluid in an evaporator heat exchanger stage to form a gaseous flow of a first heat transfer fluid, passing the gaseous flow of the first heat transfer fluid from the thermal energy storage to a condenser heat exchanger stage, and condensing the gaseous flow of the first heat transfer fluid in the condenser heat exchanger stage to transfer thermal energy from the heat transfer fluid to a second heat transfer fluid in the secondary circuit.

[0098] In one embodiment, the primary circuit includes a pressure increasing device (eg, an injector pump) operable to pressurize fluid received from the condenser heat exchanger stage and deliver the fluid at an elevated pressure to the evaporator heat exchanger stage.

[0099] In one embodiment, the pressure output of the pressure increase device is above atmospheric pressure (eg at least 0.5 bar, such as at least 1 bar, such as at least 2 bar). In one embodiment, the secondary circuit includes a circulation pump connected to a backup power source (e.g., a battery), and the method further includes, in a power failure mode, ceasing operation of the pressure increase device in the primary circuit, and maintaining operation of the circulation pump of the secondary circuit using the backup power source until all of the vapor phase of the first heat transfer fluid in the primary circuit is safely condensed.

[0100] In one embodiment, the secondary circuit includes a buffer reservoir operable to hold a sufficient mass of the second heat transfer fluid to absorb all of the heat from the heat transfer fluid in the primary circuit when condensed.

[0101] In one embodiment, the evaporator heat exchanger stage comprises a pipe circuit extending through or around the thermal energy storage body, the pipe circuit having an inlet and an outlet, wherein the evaporation step in discharge mode comprises generating a gaseous flow of the first heat transfer fluid at the outlet at a velocity of at least 100 km / hr (e.g. at least 200 km / hr, e.g. at least 300 km / hr).

[0102] In one embodiment, the energy storage system is an energy storage system according to the third aspect of the invention (eg according to any embodiment of the third aspect of the invention). According to a fifth aspect of the present invention there is provided an electrical installation for a building (e.g. accommodation or workspace within a building), the electrical installation comprising: an electricity supply to the building (e.g. a network grid supply) having a maximum rated current draw; an energy storage system comprising a thermal energy store (e.g. a thermal mass), one or more electric heating devices operable to draw current from the supply of electricity and supply thermal energy to the thermal energy store, and a heat exchanger operable to transfer thermal energy from the thermal energy store to a heat transfer fluid (e.g. a heat transfer fluid of (or thermally coupled to) the building's hot water / central heating system); a control arrangement comprising a controller, a sensor operable to measure the current drawn from the supply, one or more current control devices each operable by the controller to control an amount of current sent to the one or more electric heating devices, wherein the controller is operative to operate the one or more current control devices to limit a total current sent to the energy storage system (e.g. to the one or more electric heating devices) to less than the maximum rated current draw.

[0103] In one embodiment, the one or more current control devices are operable to reduce the amount of current sent to the one or more electric heating devices to a value less than the maximum current drawn by the electric heating device at the supply voltage.

[0104] In one embodiment, the energy storage system includes a plurality of heating circuits each including a respective electric heating device, and the controller is operative to operate one or more current control devices to limit a total current sent to the plurality of electric heating devices to less than a maximum rated current draw.

[0105] In one embodiment, the one or more current control devices are operable to isolate the electric heating device from the supply (eg, to isolate one of the heating circuits). In one embodiment, the multiple heating circuits include a variable power (eg, variable current) heating circuit and one or more fixed power (eg, fixed current) heating circuits.

[0106] In one embodiment, the energy storage system further includes one or more additional electrical devices capable of drawing current from the supply. In one embodiment, the one or more additional electric devices include a fluid heating device operable by the controller to draw current from a supply of electrical power and provide heat to (e.g., directly to) the heat transfer fluid (e.g., as the heat transfer fluid flows from the energy storage system to a building's hot water / central heating system). In this manner, the energy storage system may provide a boost at the start-up of operation of the hot water / central heating system (e.g., a condition in which the heat output of the energy storage exceeds the maximum output of the thermal energy store) or may supplement the heat output of the energy store when it falls below a threshold level (e.g., the temperature of the thermal energy store falls below an ideal level).

[0107] In one embodiment, one or more additional electrical devices are provided in one or more of the multiple circuits. In one embodiment, one or more of the multiple circuits can be switched from charging a thermal energy store to directly heating a heat transfer fluid (e.g. directly supplying heat to a building's hot water / domestic centralized water circuit).

[0108] In one embodiment, the energy storage system is located outside the building or in / adjacent to a garage associated with the building. In one embodiment, the one or more additional electric devices include charging equipment for electric vehicles (e.g., in one or more of the heating circuits). In this manner, the energy storage system can provide heat to a domestic water circuit as well as one or more EV chargers, and can provide bi-directional vehicle-to-grid or vehicle-to-home power.

[0109] In one embodiment, the supply includes a network fuse. In one embodiment, the energy storage system is connected between the network fuse and a supply to the building (eg, a network supply).

[0110] In one embodiment, the sensor is operable to measure the current drawn from the supply at a point upstream of the network fuse. In one embodiment, the sensor is operable to measure the current drawn from the supply at a point between the network fuse and the energy storage system.

[0111] In one embodiment, the total (e.g. combined) current draw capacity of the one or more electric heating devices at the maximum expected supply voltage is at least 110% (e.g. at least 120%, such as at least 130%, such as at least 140%) of the maximum current draw of the supply (e.g. network fuse rating). In this way, the impact of voltage drop in the supply on the performance of the one or more heating devices may be substantially minimized.

[0112] In one embodiment, the controller serves to operate one or more current control devices to limit the total current sent to the energy storage system to no more than 90% of the maximum rated current draw (e.g., to minimize the risk of blowing a network fuse).

[0113] In one embodiment, the supply is a single phase supply. In one embodiment, the supply is a multi-phase (eg, three-phase) supply. In one embodiment, the energy storage system is an energy storage system according to the second, third, seventh, tenth, twelfth, fourteenth or sixteenth aspect of the invention (e.g. according to an embodiment of any of the second, third, seventh, tenth, twelfth, fourteenth or sixteenth aspect of the invention).

[0114] According to a sixth aspect of the present invention, there is provided a vacuum insulated container comprising an inner container, an outer container surrounding the inner container, the inner container and the outer container being separated by a vacuum region extending therebetween, and an internal brace disposed within the vacuum region, the internal brace configured to engage an inner surface of the outer container and resist compression of the outer container.

[0115] In this manner, a vacuum insulated container with a relatively thin outer container wall may be capable of withstanding compressive forces generated by negative pressure within the container and / or resisting external pressures / influences. In one embodiment, the inner surface of the outer container has a generally cylindrical profile.

[0116] In one embodiment, the internal brace has a generally annular profile when viewed along a longitudinal axis of the internal brace. In one embodiment, no portion of the internal brace contacts the inner vessel.

[0117] In one embodiment, the internal brace is configured (eg, during manufacture) to be slidably insertable into a vacuum region. In one embodiment, the internal brace is manufactured from a single piece (eg, a one-piece section).

[0118] In one embodiment, the internal brace is a radially (eg, circumferentially) expandable brace (eg, expandable between a radially contracted configuration and a radially expanded configuration).

[0119] In one embodiment, the radially expandable brace is biased (eg, resiliently biased) into the expanded configuration. In one embodiment, the radially expandable brace is preloaded to apply tension to the inner surface of the outer container (ie, the inner surface of the outer container is continuously in tension).

[0120] In an alternative embodiment, the internal brace (e.g., a brace that is radially expandable to a radially expanded configuration) may fit snugly within the inner surface of the outer container (e.g., with only the inner surface of the outer container being under tension in response to a compressive displacement of the inner surface of the outer container).

[0121] In one embodiment, the radially expandable brace includes a radially expandable cage structure. In one embodiment, the radially expandable brace is a torsion brace configured to be urged to expand radially when under tension (e.g., urged to expand radially when a torsion is applied in a first direction and urged to contract radially when a torsion is applied in a second, opposite direction).

[0122] In one embodiment, the torsion brace includes a cage or coil structure. In one embodiment, the torsion brace includes a helical coil structure. In one embodiment, the helical coil structure is a substantially continuous helical coil structure or a structure including a series of connected helical coil sections (e.g., helical coil sections connected in series by torsional transfer connections (e.g., coil or non-coil torsional transfer connections)).

[0123] In one embodiment, the torsion brace imparts a twist to the inner surface of the outer container (eg, inserted into the vacuum region in a twisted configuration or twisted after insertion into the vacuum region).

[0124] In one embodiment, the vacuum insulated container includes an additional internal brace disposed within the inner container, the additional internal brace configured to engage an inner surface of the inner container and resist compression of the inner container (e.g., during manufacturing and while testing the inner container).

[0125] In one embodiment, the further internal brace is according to any of the embodiments of the internal brace of the first definition defined above. In one embodiment, the vacuum region has a vacuum pressure (eg, a partial vacuum pressure).

[0126] In one embodiment, the vacuum pressure is between 0.05 mbar and 1 mbar. In one embodiment, the vacuum insulated vessel includes a vacuum pump (eg, an integral vacuum pump) operable to maintain a vacuum pressure (eg, a partial vacuum pressure) in the vacuum region.

[0127] In one embodiment, the vacuum pump maintains the vacuum pressure at a level between 0.05 mbar and 1 mbar. In one embodiment, the vacuum insulated container includes a sensor operable to measure a parameter (e.g., pressure and / or temperature (e.g., surface temperature)) at one or more locations of the vacuum insulated container, and the vacuum pump is configured to operate whenever the sensor indicates that the parameter reaches a predetermined value (e.g., pressure drops below / temperature rises above). In this manner, the vacuum insulated container comprises vacuum insulation requiring only intermittent operation of the vacuum pump.

[0128] In one embodiment, the vacuum insulated vessel further includes an integrated vacuum valve operable to connect a vacuum pump to the vacuum zone. In one embodiment, the vacuum insulated container is further provided with insulation within the vacuum region, in this manner the vacuum level required to achieve a desired degree of insulation may be reduced.

[0129] In one embodiment, the insulation material is wrapped around the outer wall of the inner container (e.g., substantially covers the outer surface of the inner container), in this way the insulation material can function as a microporous insulator only in the direction perpendicular to the side of the inner container.

[0130] In one embodiment, the insulation comprises a multi-layer insulation of n layers. In one embodiment, each layer of the multi-layer insulation includes a reflective layer and a spacer layer. In one embodiment, n > 50 (such as n > 100, such as n > 150).

[0131] In one embodiment, n is about 200 (eg, n is approximately 200). In one embodiment, the insulation comprises at least 10 layers of multilayer insulation per 100 degrees Celsius temperature difference across the vacuum region (i.e., n>50 when the temperature difference is 500 degrees Celsius), at least 20 layers of multilayer insulation per 100 degrees Celsius temperature difference across the vacuum region (i.e., n>100 when the temperature difference is 500 degrees Celsius), or at least 40 layers of multilayer insulation per 100 degrees Celsius temperature difference across the vacuum region (i.e., n>200 when the temperature difference is 500 degrees Celsius). That is, in one embodiment, ΔT / n≦10, in another embodiment, ΔT / n≦5, and in another embodiment, ΔT / n≦2.5, where ΔT is the temperature across the vacuum region in degrees Celsius (i.e., the temperature difference between the inner wall of the outer container and the opposing outer wall of the inner container).

[0132] In one embodiment, the average spacing between the reflective layer and the spacer layer in each layer of the multi-layer insulation is less than 1 mm (eg, less than 0.5 mm, such as less than 0.2 mm). In one embodiment, the average spacing between the reflective layer and the spacer layer in each layer of the multi-layer insulation varies from layer to layer.

[0133] In one embodiment, the spacing between the reflective layer and the spacer layer in each layer of the multi-layer insulation is between 1 mm and 0.01 mm. In one embodiment, the reflective layer is a reflective metal sheet (eg, an aluminum sheet).

[0134] In one embodiment, the spacer layer is a thin fiberglass layer or a thin ceramic fiber (eg, ceramic fiber paper) layer. According to a seventh aspect of the present invention, there is provided an energy storage system comprising a vacuum insulated container according to the sixth aspect of the present invention (eg according to any embodiment of the sixth aspect of the present invention).

[0135] According to an eighth aspect of the present invention there is provided a vacuum insulated pipe comprising an inner pipe section, an outer pipe section surrounding the inner pipe section, the inner pipe section and the outer pipe section being separated by a vacuum region extending therebetween, and an internal brace provided within the vacuum region, the internal brace configured to engage an inner surface of the outer pipe section and to resist compression of the outer pipe section.

[0136] In one embodiment, the inner surface of the outer pipe section has a generally cylindrical profile. In one embodiment, the internal brace has a generally annular profile when viewed along a longitudinal axis of the internal brace.

[0137] In one embodiment, no portion of the internal brace contacts the inner pipe section. In one embodiment, the internal brace is configured (eg, during manufacture) to be slidably insertable into a vacuum region.

[0138] In one embodiment, the internal brace is manufactured from a single piece (eg, a one-piece section). In one embodiment, the internal brace is a radially (eg, circumferentially) expandable brace (eg, expandable between a radially contracted configuration and a radially expanded configuration).

[0139] In one embodiment, the radially expandable brace is biased (eg, resiliently biased) into the expanded configuration. In one embodiment, the radially expandable brace is preloaded to tension the inner surface of the outer pipe section (i.e., the inner surface of the outer pipe section is continuously tensioned).

[0140] In an alternative embodiment, the internal brace (e.g., a brace that is radially expandable to a radially expanded configuration) may fit snugly against the inner surface of the outer pipe section (e.g., with only the inner surface of the outer pipe section being in tension in response to a compressive displacement of the inner surface of the outer pipe section).

[0141] In one embodiment, the radially expandable brace includes a radially expandable cage structure. In one embodiment, the radially expandable brace is a torsion brace configured to be urged to expand radially when under tension (e.g., urged to expand radially when a torsion is applied in a first direction and urged to contract radially when a torsion is applied in a second, opposite direction).

[0142] In one embodiment, the torsion brace includes a cage or coil structure. In one embodiment, the torsion brace includes a helical coil structure. In one embodiment, the helical coil structure is a substantially continuous helical coil structure or a structure including a series of connected helical coil sections (e.g., helical coil sections connected in series by torsional transfer connections (e.g., coil or non-coil torsional transfer connections)).

[0143] In one embodiment, the torsion brace applies tension to the inner surface of the outer pipe section (eg, inserted into the vacuum area in a twisted form, or twisted after insertion into the vacuum area).

[0144] In one embodiment, the vacuum region has a vacuum pressure (eg, a partial vacuum pressure). In one embodiment, the vacuum pressure is between 0.05 mbar and 1 mbar. In one embodiment, the vacuum insulated pipe includes a vacuum pump (eg, an integral vacuum pump) operable to maintain a vacuum pressure (eg, a partial vacuum pressure) in the vacuum region.

[0145] In one embodiment, the vacuum pump maintains the vacuum pressure at a level between 0.05 mbar and 1 mbar. In one embodiment, the vacuum insulated pipe includes a sensor operable to measure a parameter (e.g., pressure and / or temperature (e.g., surface temperature)) at one or more locations within the vacuum insulated pipe, and the vacuum pump is configured to operate whenever the sensor indicates that the parameter reaches a predetermined value (e.g., pressure drops below / temperature rises above). In this manner, the vacuum insulated pipe is provided with vacuum insulation and requires only intermittent operation of the vacuum pump.

[0146] In one embodiment, the vacuum insulated pipe further includes an integrated vacuum valve operable to connect a vacuum pump to the vacuum zone. In one embodiment, the vacuum insulated pipe is further provided with insulation within the vacuum area, in this way the vacuum level required to achieve a desired degree of insulation can be reduced.

[0147] In one embodiment, the insulation is wrapped around the outer wall of the inner pipe section (e.g., substantially covering the outer surface of the inner pipe section), in this way the insulation can function as a microporous insulator only in the direction perpendicular to the side of the inner pipe section.

[0148] In one embodiment, the insulation comprises a multi-layer insulation of n layers. In one embodiment, each layer of the multi-layer insulation includes a reflective layer and a spacer layer. In one embodiment, n > 50 (such as n > 100, such as n > 150).

[0149] In one embodiment, n is approximately 200 (eg, n is approximately 200). In one embodiment, the insulation comprises at least 10 layers of multilayer insulation per 100 degrees Celsius temperature difference across the vacuum region (i.e., n>50 when the temperature difference is 500 degrees Celsius), at least 20 layers of multilayer insulation per 100 degrees Celsius temperature difference across the vacuum region (i.e., n>100 when the temperature difference is 500 degrees Celsius), or at least 40 layers of multilayer insulation per 100 degrees Celsius temperature difference across the vacuum region (i.e., n>200 when the temperature difference is 500 degrees Celsius). That is, in one embodiment, ΔT / n≦10, in another embodiment, ΔT / n≦5, and in another embodiment, ΔT / n≦2.5, where ΔT is the temperature across the vacuum region in degrees Celsius (i.e., the temperature difference between the inner wall of the outer container and the opposing outer wall of the inner container).

[0150] In one embodiment, the average spacing between the reflective layer and the spacer layer in each layer of the multi-layer insulation is less than 1 mm (eg, less than 0.5 mm, such as less than 0.2 mm). In one embodiment, the average spacing between the reflective layer and the spacer layer in each layer of the multi-layer insulation varies from layer to layer.

[0151] In one embodiment, the spacing between the reflective layer and the spacer layer in each layer of the multi-layer insulation is between 1 mm and 0.01 mm. In one embodiment, the reflective layer is a reflective metal sheet (eg, an aluminum sheet).

[0152] In one embodiment, the spacer layer is a thin fiberglass layer or a thin ceramic fiber (eg, ceramic fiber paper) layer. In one embodiment, the outer pipe section includes one or more expansion regions.

[0153] In one embodiment, the vacuum insulated pipe further includes one or more external supports operable to support the outer pipe section (eg, adjacent one or more expansion regions).

[0154] In one embodiment, the one or more external supports are configured to slidably engage the outer pipe section (eg, by an external rolling (eg roller) bearing). In one embodiment, the vacuum insulated pipe further includes one or more internal supports (eg, adjacent one or more expansion regions) operable to support the inner pipe section.

[0155] In one embodiment, the one or more internal supports are configured to slidably engage the inner pipe section (eg, by means of an internal rolling (eg roller) bearing). According to a ninth aspect of the present invention, there is provided a thermal storage body (e.g. a hot water tank) comprising a container (e.g. an insulated container) defining a chamber for storing heated water, a primary water (e.g. hot water) outlet line operable to receive water (e.g. hot water) from an upper region of the chamber and discharge the received water from the container during a discharge mode, a water inlet line operable to introduce water to a lower region of the chamber (e.g. to refill the container) during a discharge mode, a secondary water (e.g. warm water) outlet line operable to receive water (e.g. warm water) from the lower region of the chamber and discharge the received water from the container during the discharge mode, and a mixing stage (mixing valve) operable to mix the water (e.g. warm water) received from the secondary outlet line with the water (e.g. hot water) received from the primary water outlet line to provide an output flow (e.g. an output flow at a predetermined water temperature).

[0156] In this way a thermal reservoir is provided in which debris (e.g. mineral debris, e.g. limescale deposits) is flushed from the chamber during discharge mode and entrained in the output flow from the vessel. Advantageously, this means that cleaning of the vessel can be achieved without the need for filters or collectors, thereby reducing the need for regular maintenance.

[0157] In one embodiment, the water inlet line is operable to introduce cold water (eg water from the mains) to the lower region of the chamber. In one embodiment, the secondary water outlet line includes a water inlet (eg, a warm water inlet) located at the base of the chamber.

[0158] In one embodiment, the water inlet is provided at approximately the level of the inner surface of the base portion of the chamber. In one embodiment, the water inlet is provided at the lowest region of the base portion of the chamber. In one embodiment, the water inlet is located at a central (eg, central lowest) position within the base portion of the chamber.

[0159] In one embodiment, the secondary water outlet line comprises a secondary water outlet pipe means (eg, a secondary water outlet pipe). In one embodiment the secondary water outflow pipe means extends through the base of the vessel.

[0160] In one embodiment, the water inlet line includes a water outlet (eg, a cold water outlet) located in a lower region of the chamber. In one embodiment, the water outlet is positioned higher than the water inlet within the room.

[0161] In one embodiment, the water outlet includes a diffuser operable to disperse water (eg, disperse water (eg, cold water) laterally (eg, in multiple lateral directions)). In one embodiment, the water inlet line comprises a water inlet pipe means (eg a water inlet pipe).

[0162] In one embodiment the water inlet pipe means extends through the base of the vessel and into the lower portion of the chamber. In one embodiment, the water inlet line and the secondary water outlet line extend through a single aperture in the base of the vessel.

[0163] In one embodiment the water inlet pipe means includes a first passage defining a first longitudinal axis and the secondary water pipe means includes a second passage defining a second longitudinal axis. In one embodiment, the first and second longitudinal axes are substantially aligned (eg, coaxial).

[0164] In one embodiment the water inlet pipe means extends through (eg longitudinally through) the second passage of the secondary water pipe means, or vice versa. In one embodiment, the thermal store is further configured to add (eg, selectively add) an additional stream of water to the output flow (eg, at a point either downstream or upstream of the mixing stage).

[0165] In one embodiment, the thermal storage body is further configured to add (e.g., selectively add) cold water (e.g., cold water poured from a water inlet line) to the output flow (e.g., at a point either downstream or upstream of the mixing stage).

[0166] In one embodiment, the thermal storage further includes a second mixing stage (e.g., a second mixing valve) operable to selectively mix cold water (e.g., poured from the water inlet line) with the output flow from the first defined mixing stage.

[0167] In one embodiment, the container is an inner container and the thermal storage further comprises an outer container surrounding the inner container, the inner container and the outer container being separated by a vacuum region extending therebetween.

[0168] In one embodiment, at least one (eg, each) of the water inlet line and the secondary water outlet line extends through the base of the inner vessel. In one embodiment, at least one (eg, each) of the water inlet line and the secondary water outlet line extends through the base of the outer vessel.

[0169] In one embodiment, the primary water outflow line extends through the base of the inner vessel. In one embodiment, the primary water outflow line extends through the base of the outer vessel. In one embodiment, the primary water outlet line comprises a primary water outlet pipe means (eg, a primary water outlet pipe).

[0170] In one embodiment, the primary water outlet line extends through a single aperture in the base of the vessel (eg, the same single aperture as the water inlet line and the secondary water outlet line). In one embodiment, the primary water outlet line defines a third longitudinal axis.

[0171] In one embodiment, the third longitudinal axis and one or more (eg, each) of the first and second axes are substantially aligned (eg, coaxial). In one embodiment, the primary water outlet line forms part of the hot water dispenser module.

[0172] In one embodiment, the hot water dispenser module includes an outer sleeve extending through a base of the inner container and a base of the outer container, the outer sleeve defining a sleeve chamber, and a primary water contour line extending through the sleeve chamber (e.g., an outlet on the exterior of the outer container).

[0173] In one embodiment, the sleeve chamber is sealed at its upper end to prevent ingress of water into the sleeve chamber. In one embodiment, the hot water dispenser module extends through a single aperture in the base of the vessel (eg, the same single aperture as the water inlet line and the secondary water outlet line).

[0174] In one embodiment, the hot water dispenser module defines a fourth longitudinal axis. In one embodiment, the fourth longitudinal axis and one or more (eg, each) of the first and second axes are substantially aligned (eg, coaxial).

[0175] In one embodiment, the thermal storage further includes an external heating stage operable to heat incoming water at a location external to the vessel, and a heated water inlet line operable to introduce water heated by the heating stage into the vessel during the charging mode.

[0176] In one embodiment, the heated water inlet line extends through the base of the vessel. In one embodiment, the heated water inlet line extends through a central region of the base of the vessel.

[0177] In one embodiment, the thermal store includes a pump for conveying water to the heating stage and / or the heated water inlet line. In one embodiment, the heated water inlet line includes a heated water outlet located at the base of the vessel.

[0178] In one embodiment, the heated water inlet line comprises a heated water inlet pipe means (eg a heated water inlet pipe). In one embodiment the heated water inlet pipe means extends through the base of the vessel.

[0179] In one embodiment, the lower end of the primary water outlet line extends through the base of the vessel. In one embodiment, the heated water inlet line and the heated water outlet line extend through a single aperture in the base of the vessel (e.g., through the same single aperture as the water inlet line / secondary water outlet line and / or the primary water outlet line).

[0180] In one embodiment, the lower end of the heated water outlet line functions as a heated water inlet during charging mode (whereby water heated by the heating stage is directed up the primary water output line to the upper region of the vessel).

[0181] In one embodiment, the heated water inlet line is parallel to the lower end of the heated water outlet line. In one embodiment, the heated water inlet is positioned to introduce received heated water into the lower section of the chamber.

[0182] In one embodiment the heating water inlet pipe means includes a first passage defining a first longitudinal axis and the primary water outlet pipe means includes a second passage defining a second longitudinal axis.

[0183] In one embodiment, the first and second longitudinal axes are substantially aligned (eg, coaxial). In one embodiment the primary water outlet pipe means extends through (eg longitudinally through) the second passage of the heated water inlet pipe means, or vice versa.

[0184] In one embodiment, the heating stage includes an electric heater. In one embodiment, the heating stage includes a heat exchanger. In one embodiment, the thermal store further includes a descaler stage (eg, an electronic or magnetic descaler).

[0185] In one embodiment, a descaler stage is provided upstream of the heating stage (eg, between the pump and the heating stage). In one embodiment, the heating stage is operable to heat the water received from the descaler stage after a predetermined period of time (eg, at least 1-20 seconds after exposure to the descaler stage).

[0186] In one embodiment, the heating stage is operable to receive water processed by the descaler stage 1 to 600 seconds after exposure of the water to the descaler stage (e.g., 2 to 600 seconds after exposure of the water to the descaler stage, e.g., 10 to 600 seconds after exposure of the water to the descaler stage, e.g., 20 to 600 seconds after exposure of the water to the descaler stage).

[0187] In one embodiment, the heating stage is operable to receive water that has been treated by the descaler stage shortly (eg, immediately after) a predetermined period of time has elapsed.

[0188] In one embodiment, the heating stage is operable to heat the water received from the descaler stage within 1 to 600 seconds of exposure to the descaler stage. In one embodiment, the predetermined period is achieved by a slow flow rate between the descaler stage and the heating stage.

[0189] In one embodiment, the heated water outlet line forms part of the hot water dispenser module. In one embodiment, the vessel is a thermally stratified tank.

[0190] In one embodiment, the thermal storage body may include any of the features of the first, sixth, eleventh, thirteenth or fifteenth aspects of the invention (e.g. according to an embodiment of any of the first, sixth, eleventh, thirteenth or fifteenth aspects of the invention).

[0191] According to a tenth aspect of the present invention there is provided an energy storage system comprising a thermal store according to the ninth aspect of the present invention (eg according to any embodiment of the ninth aspect of the present invention).

[0192] According to an eleventh aspect of the present invention, there is provided a thermal storage body (e.g. a hot water tank) comprising a container defining a chamber for storing a heated liquid (e.g. heated water or oil), a heated liquid (e.g. hot water) outlet line operable to receive heated liquid (e.g. hot water) from an upper region of the container and to discharge the heated liquid from the container during a discharge mode, an external heating stage operable to heat the incoming liquid at a location external to the container, and a heated liquid (e.g. hot water) inlet line operable to introduce liquid heated by the heating stage into the container during a charge mode.

[0193] In this way, a thermal reservoir is provided in which heating is accomplished entirely outside the container, thereby eliminating the need to install and subsequently maintain heating elements within the container. In one embodiment, the heating liquid inlet line extends through the base of the vessel.

[0194] In one embodiment, the thermal storage is operable during a discharge mode to introduce liquid (e.g., chilled liquid) into the vessel (e.g., to refill the vessel) and during a charge mode to convey liquid from the tank (e.g., liquid (e.g., chilled liquid) from a lower region of the tank) to a heating stage (e.g., for heating before being returned to the vessel via a heated liquid inlet line).

[0195] In one embodiment, the heating liquid inlet line extends through a central region of the base of the vessel. In one embodiment, the thermal store includes a pump for conveying liquid to the heating stage and / or the heating liquid inlet line.

[0196] In one embodiment, the heating liquid inlet line includes a heating liquid inlet located at the base of the vessel. In one embodiment, the heating liquid inlet line comprises a heating liquid inlet pipe means (eg a heating liquid inlet pipe).

[0197] In one embodiment the heating liquid inlet pipe means extends through the base of the vessel. In one embodiment, the lower end of the heating liquid outlet line extends through the base of the vessel.

[0198] In one embodiment, the heating liquid inlet line and the heating liquid outlet line extend through a single aperture in the base of the vessel. In one embodiment, the lower end of the heating liquid outlet line functions as a heating liquid inlet during the charging mode (whereby liquid heated by the heating stage is directed up the heating liquid output line to the upper region of the vessel).

[0199] In one embodiment, the heating liquid inlet line is provided parallel to the lower end of the heating liquid outlet line. In one embodiment, the heating liquid inlet is positioned to introduce received heating liquid into the lower section of the chamber.

[0200] In one embodiment, the heating liquid outlet line comprises a heating liquid outlet pipe means (eg a heating liquid outlet pipe). In one embodiment the heating liquid inlet pipe means includes a first passage defining a first longitudinal axis and the heating liquid outlet pipe means includes a second passage defining a second longitudinal axis.

[0201] In one embodiment, the first and second longitudinal axes are substantially aligned (eg, coaxial). In one embodiment the heating liquid outlet pipe means extends through (eg longitudinally through) the second passage of the heating liquid inlet pipe means, or vice versa.

[0202] In one embodiment, the heating stage includes an electric heater. In one embodiment, the heating stage includes a heat exchanger. When the heating liquid is water, in one embodiment the thermal store further comprises a descaler stage (eg an electronic or magnetic descaler).

[0203] In one embodiment, the descaler stage is provided upstream of the heating stage (eg, between the pump and the heating stage). In one embodiment, the heating stage is operable to heat the water received from the descaler stage after a predetermined period of time (eg, at least 1-20 seconds after exposure to the descaler stage).

[0204] In one embodiment, the heating stage is operable to receive water that has been treated by the descaler stage shortly (eg, immediately after) a predetermined period of time has elapsed.

[0205] In one embodiment, the heating stage is operable to receive water processed by the descaler stage 1 to 600 seconds after exposure of the water to the descaler stage (e.g., 2 to 600 seconds after exposure of the water to the descaler stage, e.g., 10 to 600 seconds after exposure of the water to the descaler stage, e.g., 20 to 600 seconds after exposure of the water to the descaler stage).

[0206] In one embodiment, the predetermined period of time may be achieved by a slow flow rate between the descaler stage and the heating stage. In one embodiment, the container is an inner container and the thermal storage further comprises an outer container surrounding the inner container, the inner container and the outer container being separated by a vacuum region extending therebetween.

[0207] In one embodiment, the external heating stage is operable to heat the incoming liquid at a location external to the outer vessel. In one embodiment, the heated liquid inlet line is operable to introduce liquid heated by the heating stage into the inner vessel during the charging mode.

[0208] In one embodiment, the heating liquid inlet line extends through the base of the inner vessel. In one embodiment, the heating liquid inlet line extends through the base of the outer vessel. In one embodiment, the vessel is a thermally stratified tank.

[0209] In an embodiment, the thermal storage body may comprise any of the features of the first, sixth, ninth, thirteenth or fifteenth aspects of the invention (e.g. according to an embodiment of any of the first, sixth, ninth, thirteenth or fifteenth aspects of the invention).

[0210] According to a twelfth aspect of the present invention there is provided an energy storage system comprising a thermal store according to the eleventh aspect of the present invention (eg according to any embodiment of the eleventh aspect of the present invention).

[0211] According to a thirteenth aspect of the present invention, there is provided a vacuum insulated thermal storage body (e.g. a vacuum insulated hot water tank) comprising an inner container defining a chamber for storing a heated liquid (e.g. heated water or oil), an outer container surrounding the inner container, the inner container and the outer container being separated by a vacuum region extending therebetween, and a heated liquid (e.g. hot water) dispenser module comprising an outer sleeve extending through a base of the inner container and a base of the outer container, the outer sleeve defining a sleeve chamber, and a heated liquid (e.g. hot water) outlet line extending through the sleeve chamber (e.g. to an outlet outside the outer container).

[0212] Advantageously, by providing a heated liquid dispenser module, multiple components mounted within the module can be inserted through apertures in the container, thereby simplifying manufacturing and subsequent maintenance.

[0213] In one embodiment, the sleeve chamber is sealed at its upper end to prevent ingress of liquid into the sleeve chamber. In one embodiment, the heating liquid outlet line comprises a heating liquid outlet pipe means (eg a heating liquid outlet pipe).

[0214] In one embodiment, the sleeve chamber is configured to provide a layer of insulation (eg, an air gap) around the heated liquid outlet line. In one embodiment, the sleeve chamber is open to the atmosphere at its lower end.

[0215] In one embodiment, the outer sleeve includes a single sleeve element that extends from within the inner container to the base of the outer container, hi another embodiment, the outer sleeve may include multiple connected elements.

[0216] In one embodiment, the sleeve chamber has a generally cylindrical inner profile. In one embodiment, the outer sleeve has a generally cylindrical outer profile.

[0217] In one embodiment, the heated liquid dispenser module includes one or more temperature sensors disposed within the sleeve chamber (e.g., spaced from the heated liquid outflow line) operable to measure the temperature of the heated liquid in the inner container.

[0218] In one embodiment, the heated liquid dispenser module includes a plurality of temperature sensors (e.g., provided at different heights along the module) at different heights within the inner vessel that are operable to measure the temperature of the heated liquid within the inner vessel.

[0219] In one embodiment, the weight of the inner container is at least partially supported (eg, substantially supported) by the outer sleeve. In one embodiment, the inner vessel is a thermally stratified tank.

[0220] In one embodiment, the vacuum insulated thermal storage body may include any of the features of the first, sixth, ninth, eleventh or fifteenth aspects of the invention (e.g. according to an embodiment of any of the first, sixth, ninth, eleventh or fifteenth aspects of the invention).

[0221] According to a fourteenth aspect of the present invention there is provided an energy storage system comprising a vacuum insulated thermal store according to the thirteenth aspect of the present invention (eg according to any embodiment of the thirteenth aspect of the present invention).

[0222] According to a fifteenth aspect of the present invention, there is provided a vacuum insulated container comprising an inner container housing a thermal energy storage body and an outer container surrounding the inner container, the inner container and the outer container being separated by a vacuum region extending therebetween, wherein the inner container is connected to the outer container via an inner neck portion, the inner neck portion including an outer neck portion and a tapered inner neck portion connecting the outer neck portion to the inner container.

[0223] In this manner, a neck portion is provided which distributes bending loads in a controlled manner, thereby allowing a thinner material (eg, thinner steel) to be used to form the neck portion.

[0224] In one embodiment, the inner neck portion includes a central chamber (e.g., a central conduit) that houses supply lines for the thermal energy storage body (e.g., supply lines for one or more heating elements (e.g., electrical cables for one or more electric heating elements) and / or fluid transport pipes (e.g., inlet and outlet pipes)).

[0225] In one embodiment, no part of the inner container touches the outer container. In one set of embodiments, the inner neck portion is provided at an upper end of the inner container (e.g., the inner upper neck portion). In this set of embodiments, the outer neck portion is an upper neck portion and the tapered inner neck portion is a tapered lower neck portion.

[0226] In another set of embodiments, the inner neck portion is provided at a lower end of the inner container (e.g., an inner lower neck portion). In this set of embodiments, the outer neck portion is a lower neck portion and the tapered inner neck portion is a tapered upper neck portion.

[0227] In one embodiment, the inner neck portion connects the outer section of the inner container to the outer section of the outer container (eg, via a connecting plate). In one embodiment, the internal neck portion is provided to the inner container (eg, attached to or integrally formed with the inner container).

[0228] In one embodiment, the inner neck portion is connected (eg, welded) to the outer end of the inner container. In one embodiment, the outer neck portion is generally cylindrical.

[0229] In one embodiment, the tapered inner neck portion has an outermost tapered section that is inclined at a deeper taper angle than the corresponding taper angle of the innermost section of the tapered inner neck portion.

[0230] In one embodiment, the tapered inner neck portion has a concave curved profile (eg, the angle of inclination relative to the vertical increases with increasing distance from the base of the tapered neck portion).

[0231] For purposes of this disclosure, the taper angle is the acute angle measured from vertical (i.e., the smaller the angle value, the steeper the taper). In one embodiment, the inner neck portion meets the inner container at a tapered shoulder section of the inner container.

[0232] In one embodiment, the tapered shoulder section has a convex curved profile (eg, the angle of inclination relative to the vertical increases as the distance from the tapered neck portion increases).

[0233] In one embodiment, the inner neck portion is connected to the outer container via a connector plate. In one embodiment, the outer container includes an exterior neck portion.

[0234] In one embodiment, the exterior neck portion includes a tapered neck portion (eg, a tapered interior neck portion). In one embodiment, the exterior neck portion includes an outer neck portion (eg, in addition to a tapered inner neck portion).

[0235] In one embodiment, the outer neck portion of the exterior neck portion is generally cylindrical. In one embodiment, the tapered inner neck portion of the outer neck portion has an outermost tapered section that is inclined at a deeper taper angle than the corresponding taper angle of the innermost section of the tapered inner neck portion.

[0236] In one embodiment, the tapered neck portion of the outer neck portion has a concave curved profile (eg, the angle of inclination relative to the vertical increases as the distance from the base of the tapered neck portion increases).

[0237] In one embodiment, the outer neck portion meets the outer container at a tapered shoulder section of the outer container. In one embodiment, the inner container further includes a barrier (e.g., a membrane) configured to physically separate the thermal energy storage from the inner neck portion (e.g., such that heat loss through the inner neck portion includes a thermal path that extends through the barrier and along substantially the entire length of the inner neck portion). This may be particularly useful when the inner neck portion is provided at a lower end of the inner container (e.g., the inner lower neck portion) to maximize the thermal efficiency of the neck design.

[0238] In one embodiment, the barrier presents a convex barrier surface to the thermal energy store (eg, to maximize separation between the thermal energy medium and the internal neck portion). In one series of embodiments, the inner container is suspended within the outer container.

[0239] In one embodiment, the inner container is suspended via a (eg, single) internal neck portion (eg, a structurally loaded internal neck portion) that connects the upper section of the inner container to the upper section of the outer container.

[0240] In one embodiment, the inner neck portion supports the weight of the inner container and the thermal energy storage body. In one embodiment, the outer container (eg, an upper section of the outer container) includes a (eg, first) aperture (eg, a sealable aperture) for receiving an end (eg, an upper end) of the inner neck portion.

[0241] In another set of embodiments, the inner container is supported via a (eg, single) internal neck portion (eg, a structurally loaded internal neck portion) connecting the lower section of the inner container to the lower section of the outer container.

[0242] In one embodiment, the inner neck portion supports the weight of the inner container and the thermal energy storage body. In one embodiment, the outer container (eg, a lower section of the outer container) includes a (eg, first) aperture (eg, a sealable aperture) for receiving an end (eg, a lower end) of the inner neck portion.

[0243] In one embodiment, the vacuum insulated container may include any of the features of the first, sixth, ninth, eleventh or thirteenth aspects of the invention (e.g. according to an embodiment of any of the first, sixth, ninth, eleventh or thirteenth aspects of the invention).

[0244] According to a sixteenth aspect of the present invention there is provided an energy storage system comprising a vacuum insulated container according to the fifteenth aspect of the present invention (eg according to any embodiment of the fifteenth aspect of the present invention).

[0245] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0246] [Figure 1a] 1 is a schematic diagram of a thermal storage body according to a first embodiment of the present invention; [Figure 1b] FIG. 1b is a schematic diagram of the insulation used in the thermal storage body of FIG. [Diagram 2] FIG. 3 is a schematic diagram of a thermal storage body according to a second embodiment of the invention; [Diagram 3] FIG. 3 is a schematic diagram of the operation of a vacuum system used in the thermal store of FIGS. [Figure 3c] 3a and 3b are a pair of flow diagrams illustrating the operation of the vacuum system of FIG. 3a and FIG. 3b in two different modes of operation. [Figure 4]FIG. 3 is an enlarged view of a transport system used in the thermal store of FIGS. 1a and 2; [Figure 5i] FIG. 1b shows a method of assembling the thermal storage body of FIG. [Figure 5ii] FIG. 1b shows a method of assembling the thermal storage body of FIG. [Figure 5iii] FIG. 1b shows a method of assembling the thermal storage body of FIG. [Figure 5iv] FIG. 1b shows a method of assembling the thermal storage body of FIG. [Figure 5v] FIG. 1b shows a method of assembling the thermal storage body of FIG. [Figure 5vi] FIG. 1b shows a method of assembling the thermal storage body of FIG. [Figure 5vii] FIG. 1b shows a method of assembling the thermal storage body of FIG. [Figure 5viii] FIG. 1b shows a method of assembling the thermal storage body of FIG. [Figure 6] A graph of pore size vs. thermal conductivity for conventional microporous insulation. [Figure 7] Schematic diagram of an electrical installation for a building according to a further embodiment of the present invention. [Figure 8] Schematic diagram of an electrical installation for a building according to a further embodiment of the present invention. [Figure 9] Schematic diagram of an electrical installation for a building according to a further embodiment of the present invention. [Figure 10] Schematic diagram of an electrical installation for a building according to a further embodiment of the present invention. [Figure 11] 2 is a schematic diagram of an energy storage system according to a further embodiment of the present invention. [Figure 12] FIG. 11 is a schematic diagram of an energy storage system according to a further embodiment of the invention, for use with the electrical installation of FIG. 8 or FIG. 10 . [Figure 13a] FIG. 13 is a schematic diagram of a first thermal storage body for use in the energy storage system of FIG. 11 or FIG. 12. [Figure 13b] FIG. 13 is a schematic diagram of a second thermal storage body for use in the energy storage system of FIG. 11 or FIG. 12. [Figure 14]Schematic diagram of the energy storage system of FIG. 12 in combination with the thermal store of FIG. 13a. [Figure 15a] 1 is a schematic cross-sectional view of a vacuum vessel according to the prior art; [Figure 15b] 1 is a schematic cross-sectional view of a vacuum vessel according to an embodiment of the present invention; [Figure 15c] Schematic diagram of the characteristics of a helical coil. [Figure 15d] Schematic diagram of the stages of the vacuum vessel construction of FIG. 15b. [Figure 15e] 4 is a schematic cross-sectional view of a vacuum vessel according to a further embodiment of the present invention; [Figure 16a] 4 is a schematic cross-sectional view of a vacuum coated pipe according to a further embodiment of the present invention; [Figure 16b] 4 is a schematic cross-sectional view of a modified vacuum coated pipe according to another embodiment of the present invention; [Figure 17] 5A and 5B show schematic cross-sectional views of a thermal storage body according to a further embodiment of the invention; [Figure 18a] 1 is a schematic cross-sectional view of a hot water storage body according to an embodiment of the present invention; [Figure 18b] 4 is a schematic cross-sectional view of a hot water storage body according to a further embodiment of the present invention; [Figure 18c] 3 is a schematic cross-sectional view of a hot water storage body according to another embodiment of the present invention; [Figure 19a] 4 is a schematic cross-sectional view of a hot water storage body according to yet another embodiment of the present invention. [Figure 19b] 3 is a schematic cross-sectional view of a hot water storage body according to another embodiment of the present invention; [Figure 20a] 4 is a schematic cross-sectional view of a hot water storage body according to a further embodiment of the present invention; [Figure 20b] A diagram showing the operation of the hot water storage body of Figure 20a. [Figure 20c] A diagram showing the operation of the hot water storage body of Figure 20a. [Figure 20d] A diagram showing the operation of the hot water storage body of Figure 20a. [Figure 21] 1A-1C show examples of neck configurations for use with the vacuum vessel of the present invention. [Figure 22]FIG. 2 illustrates detailed geometric configuration of one embodiment of a neck structure for use with the vacuum vessel of the present invention. [Figure 23] 4 is a schematic cross-sectional view of a vacuum vessel according to a further embodiment of the present invention; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0247] FIG. 1a shows a vacuum insulated heat store 10, including an inner container 40 and an outer container 50, in which the inner container 40 contains a solid sensible heat storage material 14, in which an electric heater 6 and a heat exchanger 13 are embedded, respectively. The electric heater 6 is connected to a controller (not shown) via an electric wire 5. The sensible heat storage material 14 is contained in the inner container 40, which includes a lower inner container 41 and an upper inner container 42. The outer container 50 includes a lower outer container 51 and an upper outer container 52. A neck connector 60 includes a lower neck plate 63 element that is attached to a neck tube 62, which in turn is attached to an upper neck plate 61. The inner container 40 is attached to the outer container 50 by the neck connector 60. The weight of the inner container 40 and the sensible heat storage material 14 is suspended from the outer container 50 by the neck connector 60. The inner container 40, the outer container 50 and the neck connector 60 form a vacuum space 11. A total of n (where n=50-200) layers of multi-layer insulation (“MLI”) 12 are wrapped around inner vessel 40 and partially fills vacuum space 11 .

[0248] The vacuum is created by an integral vacuum system 20 which is connected to an outer vessel 50. The outer vessel 50 also has several fittings attached, which form the transport interface system 30.

[0249] The solid sensible heat storage material 14 may be heated to a temperature above 200° C. by any of one or more embedded electric heating bodies 6. Heat may be extracted from the solid sensible heat storage material 14 by passing a working fluid into a heat exchanger 13 via pipe 7 and out of the heat exchanger 13 via pipe 8, where the working fluid entering the heat exchanger 13 is cooler than the sensible heat storage material 14.

[0250] The neck tube 62 defines a central chamber 45 which houses supply lines for one or more heating elements 6 (e.g. electrical cables for one or more electric heating elements) and fluid transport pipes 7&8 (e.g. inlet and outlet pipes) for one or more heat exchangers 13.

[0251] All major components, except for the solid sensible heat storage material 14 and the multi-layer insulation 12, are preferably made from a suitable metal or alloy. The proposed invention involves creating a vacuum vessel that includes inner and outer concentric vessels with a number of layers of MLI, and the enclosed volume is capable of holding a vacuum of 0.05 mbar to 1 mbar, a vacuum level that is insufficient for conventional MLI insulation technology to function.

[0252] To date, vacuum insulation has only been used in very limited ways for high temperature applications, which have mainly focused on using a vacuum in combination with low-cost microporous bulk packing materials, such as perlite, in an evacuated space. However, perlite and other bulk packing materials are not suitable for thermal heat stores that use cyclical temperatures. When the inner container is heated, it expands and crushes the soft perlite bulk packing material. On cooling, the container contracts and some of the perlite falls into the gaps created by the heating cycle before being crushed again in the next heating cycle. This means that the perlite packs into the lower part of the vacuum space over time, and the insulation does not function properly.

[0253] There is a range of microporous insulation that can be supplied as moulded panels and attached to the inner or outer container within the evacuated volume. Although this avoids the loosening and dropping problem, attaching moulded panels to the cylindrical container is a complex and expensive process. Furthermore, there is a risk of the microporous material becoming detached during transport.

[0254] The solid sensible heat storage material is cast in situ while the inner vessel is assembled. The material may be a metal-rock composite (e.g. an aluminium matrix with embedded solid thermal filler material) as described in US Pat. No. 5,399,633. The inner vessel is encased with MLI. The reflective layers are separated from each other by spacer layers. The reflective layers may be aluminium and the spacer layers may be a thin glass fibre matt or paper.

[0255] The solid sensible heat storage material can be heated to 200° C. or higher. For higher temperature applications, the MLI can be made from multiple thin aluminum foil sheets (e.g., approximately 0.007 mm) and simply attached to the inner container by wrapping thin fiberglass paper (e.g., approximately 0.006-0.012 mm) separating the aluminum layers.

[0256] The MLI is wound tightly enough so that the interlayer spacing (defined as the distance from the reflective layer to the spacer layer) has an average spacing distance of less than 0.2 mm. The number of reflective layers can be greater than 50 and as many as 200 layers. The interlayer spacing can typically vary from 1 mm to 0.01 mm.

[0257] The radiant energy emitted from a black body per unit time is proportional to the fourth power of the absolute temperature, and using the Stefan-Boltzmann law, q = σT 4 A (In the ceremony q = heat transfer per unit time (W) σ=5.6703 10 -8 (W / m 2 K 4 )-Stefan-Boltzmann constant T = absolute temperature in Kelvin (K) A = area of ​​radiator (m 2 ) is) It can be expressed as:

[0258] T 4Because of the term, the Stefan-Boltzmann constant is a small number, but when the temperature difference between two surfaces is large, radiative heat transfer can be significant. Reducing the temperature difference between two surfaces by adding a layer between the surfaces reduces radiative heat transfer.

[0259] By placing n equidistant blackbody spacers, the radiative heat transfer is reduced by 1-1 / (n+1). With n=9 spacers, the radiative heat transfer is reduced by 90%. If the spacer is reflective and not an ideal black body, heat transfer can be further reduced by the emissivity of the surface. The radiant energy emitted per unit time is now:

[0260] q=εσT 4 A (In the formula, ε=Surface emissivity(-) is) By definition, a black body has an emissivity of 1, while aluminum foil's emissivity would be 0.05. This means that a black body absorbs 100% of the incident radiation, while aluminum foil absorbs just 5% and reflects 95% of it. MLI utilizes highly reflective layers separated by thin non-conductive layers. 20 layers of reflective foil with an emissivity of 0.05 would reduce radiative heat transfer by 99.8%.

[0261] The mean free path is a measure of how far an atom / molecule can travel before colliding with another atom / molecule. As air pressure is reduced, the mean free path increases because the number of atoms / molecules per unit volume, i.e., air density, decreases. Now the atoms / molecules have further to move, so they can conduct heat more easily, even though there are fewer of them. As a result, gas heat conduction remains broadly constant until the air pressure becomes very low.

[0262] The distance between the inner and outer walls of a conventional MLI vacuum insulated cryocontainer is only about 20 mm. If the mean free path is greater than 20 mm, gas conduction will begin to drop rapidly. At 0.0001 mbar, the mean free path is increased to 1000 mm, and thermal conductivity is nearly eliminated. Further reduction in pressure provides little value, as it has minimal effect on thermal conductivity. This is why vacuum insulated containers with MLI are delivered with a vacuum in the region of 0.0001 mbar. It can also be seen that at 0.01 mbar, with a mean free path of 10 mm in a 20 mm gap, gas conduction is high.

[0263] Microporous insulation works by using materials that have low solids conductivity and are full of very small pores or voids. These pores are much smaller than the mean free path, artificially limiting the distance that atoms / molecules can travel.

[0264] Generally, the smaller the pore size, the weaker the vacuum that can be used. For example, fumed silica has a very small pore size (0.001-0.05 mm) and works with just 1 mbar vacuum, which is 10,000x higher than MLI vacuum. Perlite has a pore size (0.02-0.1 mm) 20x larger than fumed silica, so it requires a better vacuum (20x lower), usually below 0.05 mbar.

[0265] As mentioned above, the use of additional spacing layers (more than 20) goes against common sense as it is clear that there is little benefit to the reduction of radiative heat transfer. However, when additional layers are added (e.g. n≧50) and tightly wound with a small average spacing, this allows the reflective and spacer layers to act like microporous insulation by restricting the distance that air molecules can travel in a direction perpendicular to the vessel. In a direction tangential to the vessel, the molecules can travel a longer distance "between" the two layers. This is different from microporous insulation, which has a fairly uniform three-dimensional nature. The use of multiple MLI layers to inhibit gas conduction means that the MLI can function as an effective insulator at vacuum levels where conventional MLIs normally do not function.

[0266] The use of the MLI also means that there is limited risk of the insulation becoming detached during transport. The inner container can expand and contract with each thermal cycle, with limited risk of the MLI becoming detached or being damaged by contact with the outer container.

[0267] The use of a much larger number of layers n increases safety in the event of total vacuum loss. If fewer MLI layers were used with higher quality vacuum levels (lower pressure), the outer casing could reach temperatures that were dangerous to touch or would damage attached tools if vacuum was lost. By using a gentler vacuum and more MLI layers, the vacuum-free insulation performance is better, thereby lowering the peak temperature that the outer casing can reach.

[0268] An added benefit of being able to operate efficiently at moderate vacuums (0.05 mbar to 1 mbar) is that this vacuum level only requires low cost vacuum pumps. This includes rotary plunger pumps, piston pumps, scroll pumps, screw pumps, rotary vane pumps, rotary piston pumps, roots pumps and sorption pumps.

[0269] In particular, oil lubricated rotary vane pumps are capable of achieving this level of vacuum. These pumps are produced at very high capacity and low cost for use in the HVAC (Heating, Ventilation and Air Conditioning) industry to remove refrigerant from heat pumps / air conditioning units / refrigerators. Ideally, the vacuum pump is a single or two stage oil lubricated rotary vane pump.

[0270] The proposed version of the invention has a vacuum insulated store provided with a vacuum pump 27 permanently connected to the evacuated space via an automatic valve 22. This means that the vacuum can be "re-pulled" on demand, including at installation.

[0271] With the vacuum insulated container provided with an integrated vacuum pump, it is possible to re-apply the vacuum at any stage. The quality of the vacuum can be deduced from the temperature difference between the inner and outer shell. Once a pre-set level is reached (i.e. the outer shell is warmer than it should be), the vacuum pump can be engaged until it drops below this level. This also means that the required vacuum level can be maintained over a period of several decades, as long as the vacuum pump is functional.

[0272] This has several advantages. I. Pulling the required vacuum can take days for the molecules to "de-gas" from the surface and be removed from the vacuum space. The large number of MLI layers means that the amount of surface that is de-gassed is much greater than in a normal container. Having an integrated vacuum pump means that the process can be carried out at the end user's site for as long as required.

[0273] II. Heat can be used to speed up this process, but it takes time and energy to heat and then cool the store using the heat store. With an integrated vacuum pump, this process can be carried out over time while using the vacuum insulated heat store.

[0274] III. The vessel may be shipped pre-filled with a solid storage medium and, as shown in one embodiment of the present invention, it may be preferable to use stabilizing bolts, which means that the vacuum will need to be re-pulled when installed on-site.

[0275] IV. A lower level of quality control is used during manufacturing. In a hard vacuum it is important that all surfaces are clean and free of oil and other materials that can outgas. Many low carbon steels contain hydrogen in their structure after manufacturing which can outgas over time. The ability to use any grade of low carbon steel is advantageous from a cost and quality control standpoint.

[0276] A single stage rotary vane pump can "theoretically" reach 0.04 mbar when the pump is pulling against a blanked-off hole, and a two stage can reach 0.004 mbar. The mean free path of air is 2.4 mm at 0.04 mbar and 24 mm at 0.004 mbar. This vacuum level is more than sufficient for the present application, but the connection to the evacuated space will have a large effect on whether this level of vacuum can be achieved with this type of pump.

[0277] Molecular flow creates a much higher flow resistance and reduces the effectiveness of the vacuum pump. When the length-to-diameter ratio of the inlet pipe to the vacuum pump is below the mean free path, the flow falls into the molecular flow regime. At a vacuum of 0.004 mbar, molecular flow becomes a significant factor when the pipe is less than 24 mm internal diameter. The length of the pipe also influences when molecular flow occurs. Molecular flow can reduce the achievable vacuum by a factor of 10 or even 100. This means that the theoretical vacuum that can be drawn by a single stage pump will be 0.04 mbar, but with long pipe connections the actual vacuum that can be drawn will increase to at least 4 mbar.

[0278] There are several problems with the current designs of vacuum pumps and the connecting hoses that connect the evacuated space to the pump. They have an inlet port to which a stainless steel flexible hose can be clamped. The other end of the hose can be clamped to a valve that connects to the evacuated space. The pump is normally switched on and once there is a reasonable vacuum in the flexible pipe the valve can be opened.

[0279] Flexible steel pipes are susceptible to damage and are expensive in large diameters, as are large diameter vacuum valves. As a result, when pulling a vacuum, the flexible connecting pipes are usually quite small (<30mm). The inlet ports to small vacuum pumps have small internal diameters (8-20mm) to accommodate the small diameter flexible pipes.

[0280] At a pressure of 0.2 millibars, a 40 mm internal diameter pipe 1 m long will allow 100 times more flow than a comparable 12 mm internal diameter pipe. In practice, low cost vacuum pumps cannot achieve the desired performance due to flow constraints around inherent valves and piping.

[0281] With reference to FIG. 3, it is a further feature of the invention that in one embodiment, an integral vacuum pump 27 can be connected to the vacuum space 11 via a large diameter pipe 25, preferably a solid (non-flexible) pipe, where the pump 27 and the vacuum space 11 are separated by a large diameter valve 22, which can preferably be automatically operated. The vacuum pump 27 can be further modified such that the inlet port 28 to the vacuum pump 27 is enlarged to an area similar to that of the large diameter pipe 25. In a further embodiment, the pipe 25 and attachment to the vacuum pump 27 are sufficient to support the pump 27 so that its weight is supported by the pipe 25. The inner diameter of the pipe can be at least 40 mm, preferably greater than 50 mm. The length of the pipe can be less than 1.0 m, preferably less than 0.5 m, to the modified inlet of the vacuum pump.

[0282] Using solid pipes is more reliable than flexible pipes and can be welded to the vessel during manufacture. Solid pipes have the risk of tolerance stacking errors in how they connect to the vacuum pump. These are eliminated by attaching the vacuum pump to the solid pipe, which is adequately supported by the solid pipe. Modifications to the inlet port to the vacuum pump provide additional options to enhance performance and provide structural attachment points to the solid pipe.

[0283] The inner and outer containers 40, 50 are only connected at the neck connector 60. If the inner container 40 with the solid thermal storage medium is not restrained during transport, it places high stresses on the neck connector 60 making it susceptible to damage during transport. Forces as high as 3g can be experienced during normal road transport. If the neck connector 60 was designed to be subjected to these stresses, it would require more material to resist these stresses than is required for normal operation. The neck connector 60 is typically steel and if a thicker section is used, the thermal conductivity in this area will be high leading to higher heat losses, which is undesirable.

[0284] The usual practice for cryogenic vacuum vessels is to have a cylindrical stub welded to the inner shell at the end opposite the neck, located within a second cylindrical member welded to the outer shell. So when the vessel is stationary there is no direct contact between the stub and the second cylinder. However, when there is relative movement between the inner and outer shells, the inner stub contacts the second cylindrical member restricting the movement and therefore stressing the neck. The downside of the stub's proximity is that it creates a heat dissipation path that may bypass the insulation. Furthermore, the vessel needs to be assembled with the inner vessel in alignment with the center of gravity. Since the solid thermal mass dominates the center of gravity, this may mean that the inner vessel, when oriented correctly (due to the center of gravity), will not be geometrically aligned with the outer vessel. If the vessel is not geometrically aligned, it is very difficult to use the stub approach, since the stub and cylinder usually need to be welded prior to assembly. This results in the conventional approach having higher heat losses when used in conjunction with a solid thermal mass in the inner vessel and being unfeasible to install.

[0285] 4, in one embodiment, the invention involves adding two or more (e.g. three or more) sockets (e.g. threaded sockets) 31 to the outer container 50. These sockets 31 allow structural shipping bolts (e.g. threaded bolts) 35 to be inserted and locked in place, thereby securely restraining the inner container 40. The use of individual shipping bolts 35 means that any misalignment between the inner container 40 and the outer container 50 can be accommodated.

[0286] This constraint means that high loads at the neck connector 60 are significantly reduced. In the preferred embodiment, having four equally spaced sockets 31 / transport bolts 35, the thermal store 10 can be transported in an orientation such that two of the transport bolts 35 are aligned with the orientation of the transport vehicle. In this way, when transported, for example, in a lorry, the braking and acceleration loads are directly under the axis of one of the pairs of fixing members. When installed on site, the transport bolts are removed and the sockets 31 are sealed by threaded sealing bolts 34. As the thermal store 10 has an integrated vacuum pump 27, loss of vacuum during transport is not an issue.

[0287] Spreader plates or pads 32 may be provided within the outer container 50 to protect the MLI layer 12 attached to the inner container. These spreader plates 32 may be used to distribute the load and ensure that no damage occurs to the MLI layer 12 wrapped around the inner container 40. Because the spreader plates 32 do not penetrate or damage the MLI, there are no additional thermal bridges.

[0288] FIG. 1b shows a cross section of n-layer multi-layer insulation (MLI) 12 positioned in the vacuum space 11 between the outer vessel 50 and the inner vessel 40. Each of the n-layer multi-layer insulation 12 includes a reflective layer 12a and a spacer layer 12b, where the layer 12 is wrapped around the outer wall of the inner vessel 40 (e.g., substantially covering the outer surface of the inner vessel). The insulation includes 200 layers of multi-layer insulation, where each layer of the multi-layer insulation includes a reflective layer and a spacer layer. There is preferably a gap between the n=200 layers and the outer vessel 50. The wrapping method may be circumferential, longitudinal, or any combination thereof (e.g., spiral). The layers 12 may be in the form of a tape or a sheet. A layer 12 may overlap a previous layer, but generally the layers should be built up uniformly over the entire surface of the inner vessel 40. The spacer layer 12b is preferably slightly wider than the reflective layer 12a. Multiple layers 12 may be added simultaneously.

[0289] Generally, the insulation should include at least 10 layers of multi-layer insulation per 100 degrees Celsius temperature difference across the vacuum region. The spacing between the reflective and spacer layers of each layer of multi-layer insulation is between 1 mm and 0.01 mm. The reflective layer 12a is a reflective metal sheet (e.g., aluminum sheet) or, for lower temperature applications, a sheet of metallized plastic or Mylar®. The spacer layer 12b can be a thin fiberglass layer or a thin ceramic fiber (e.g., ceramic fiber paper) layer, or, for lower temperature applications, a sheet of paper.

[0290] FIG. 2 shows an alternative vacuum insulated thermal store 10' based on the thermal store 10 (common features are numbered accordingly), in which the electric heating body 6 is replaced by a radiant heating element 18 mounted in a heat transfer pipe 17. The radiant heating element 18 is surrounded by, but not in close physical contact with, the heat transfer pipe 17, which may be made of a metal alloy or a high-temperature ceramic, such as quartz. Quartz has the advantage that it can be operated at higher temperatures (up to 950C) than most metal alloys and is widely transparent to infrared light, allowing the radiant heating energy to pass through the quartz to the sensible heat storage material 14'. The radiant heating element 18 is powered by an electric heating wire 5' connected to a controller (not shown). The advantage of this approach is that the radiant heating element 18 can be easily pulled out of the heat transfer pipe 17 and replaced, in contrast to the case of FIG. 1a, in which the electric heating body 6 is embedded in the sensible heat storage material 14.

[0291] Figures 3a and 3b show an integrated vacuum system 20, 20' including a valve actuator 21 connected to a vacuum valve 22 by a valve stem 24. When closed as shown in Figure 3a, the vacuum valve 22 rests on a valve seat 23. A pipe 25 connects the vacuum tight space 11 to a vacuum pump 27 via a modified inlet port 28. The pipe 25 is rigidly connected to an outer vessel 50, which also supports the vacuum pump 27. Figure 3b shows the vacuum valve 22 open, with the vacuum valve 22 not blocking the pipe 25.

[0292] FIG. 3c shows some examples of control logic for the integrated vacuum system 20. The vacuum pump 27 is operated intermittently, only when necessary, to minimize heat loss from the core to the environment. The state of the vacuum pump 27 is either ON or OFF. The vacuum pump 27 is normally always running for a preset period of time before the vacuum valve 22 is opened by the valve actuator 21. In this way, a vacuum is established on both sides of the vacuum valve 22 so that no air enters the vacuum tight space 11 when it is open. Furthermore, the force on the vacuum valve 22 is very low, lowering the power requirements of the valve actuator 21.

[0293] Optionally, the vacuum pump 27 can be operated in two modes (see: main program and continuous operation). When operating in the "main program", the vacuum pump 27 is switched on for a predetermined duration at set time intervals. - The vacuum pump 27 is switched on if the input variables are out of range. See: This is observed by the acquisition loop - Input variables can be for example surface T or vacuum level (e.g. [if T>30DegC or p>1.0mBarG]: switch on) - The duration that the pump is switched on is set (by t1). See: This is controlled by the vacuum loop. - The time between the END of one call to a program and the beginning of the next (START) can be set to any value.

[0294] When operating in "continuous operation", the vacuum pump 27 will start once started The input variables are sampled continuously at a rate determined by 1 / t3. The vacuum pump 27 is switched on if the input variables are out of range The vacuum pump 27 is switched off only if the input variables are within range Once the vacuum pump 27 is switched on, t2 seconds elapse between input variable samplings. For simplicity, typically t3=t2.

[0295] Figure 4 shows the shipping interface system 30 including sockets 31 securely attached to the outer vessel 50. In Figure 4b, shipping bolts 35 are threaded into the sockets 31 to press against the spreader plate 32, compressing the multi-layer insulation 12 against the inner vessel 40 and inhibiting movement of the inner vessel 40. Figure 4a shows the system in a non-shipping mode with the shipping bolts 35 removed and replaced with sealing bolts 34.

[0296] The spreader plate 32 is attached to straps 33, which are in turn attached to the outer container 50. The spreader plate 32 is free to move horizontally, but is restrained by the straps 33 so that the spreader plate 32 stays in place over the sockets 31.

[0297] Figures 5i to 5vii show the assembly process of the vacuum insulation thermal store 10, and Figure 5viii shows the vacuum insulation thermal store 10 configured for transportation. FIG. 5i shows the lower inner container portion 41 of the inner container 40. FIG.

[0298] FIG. 5ii shows the same lower inner vessel part 41 in which the solid sensible heat storage material 14, the heating elements 6 and wires 5, and the heat exchanger 13 are installed. FIG. 5iii shows the inner vessel top 42 attached to the lower neck plate 63 .

[0299] FIG. 5 iv shows the assembled inner container 40 with the inner container lower part 41 attached to the inner container upper part 42 , and the inner container upper part 42 attached to the lower neck plate 63 of the neck connector 60 .

[0300] Figure 5v shows the inner container 40 wrapped in n layers of multi-layer insulation 12. The inner container 40 may be supported by a neck connector 60 during the wrapping process. FIG. 5vi shows the inner vessel 40 with the multi-layer insulation 12 and neck connector 60 lowered into the outer vessel lower part 51.

[0301] FIG. 5vii shows the finished container, with the outer container lower part 51 and the outer container upper part 52 attached to the upper neck plate 61 . Figure 5viii shows the same container but with the shipping bolts 35 in place and ready for shipping.

[0302] FIG. 6 shows the relationship between pore size below 10 mm and thermal conductivity at different vacuum pressures. 7 shows an electrical installation 110 for a building having a domestic power supply 115, the electrical installation 110 including a power feed 111 (e.g. a network grid feed) associated with a network fuse 114, a thermal storage system 112, and control circuitry 110a. The network fuse 114 is a conventional fuse owned by the network and limits the amount of current drawn from the power feed 111.

[0303] The control circuit 110a includes a current sensor 116 which is connected via sensor wiring 117 to an overall controller 118, a pair of on / off current controllers 120 and a variable current controller 121. The overall controller 118 controls the variable current controller 121 as well as the on / off current controller 120 via control wiring 117 to ensure that the current drawn through the network fuse 114 remains within preset limits.

[0304] As shown, power supply 111 is connected via control circuit 110a to three electric heating devices 130 operable as electrical resistors (each provided in a separate heating circuit 129a-c) to provide heat to a thermal storage system 112 which in turn provides heat to a building's hot water / central heating system (not shown). Two of the electric heating devices 130 (provided in heating circuits 129a and 129b) are switched on or off by an on / off current controller 120, while the remaining electric heating device 130 (provided in heating circuit 129c) is controlled by a variable current controller 121.

[0305] The heat storage system 112 provides heat to a domestic heating circuit, which may be a hot water heating circuit. The heat storage system may have a preset target flow temperature, for example 65° C. or 70° C., as in the case of a gas or oil boiler, in the hot water heating circuit.

[0306] An advantage of using the variable current controller 121 and the on / off current controller 120 is that the current drawn through the network fuse 114 can be maximized over a wide current range. For example, the on / off current controller 120 can step up the current demand in increments of 32 A, while the variable current controller 121 can vary the current from 0 to 32 A. For a home with a 100 A power supply, the variable current controller 121 clearly provides more flexibility to maximize charging capacity.

[0307] A variable controller is not essential as multiple circuits can be used to get good granularity i.e. 8 x 16A on / off gives 16A or 2 x 8A steps, 7 x 16A gives the same result in 8A steps. Examples of different current ratings and steps are shown below.

[0308] Figure 7 One variable 32A and two on / off 32A circuits - giving 0 to 96A Figure 8 One variable 16A, one on / off 16A circuit, one on / off 32A-giving 0~64A Figure 9. One on / off 16A and two on / off 32A-16A steps provide 0-80A Figure 10. One variable 32A and two on / off 32A circuits - giving 0 to 96A The electricity distribution network (grid) specifies upper and lower acceptable voltage limits for the supplies that connect homes to the network. In order for network operators to stay within the terms of their licence they must ensure that this supply stays within the specified range, and this voltage is generally wide. In the UK it must be between 216V and 253V with a nominal supply voltage of 230V.

[0309] This wide voltage range creates a problem for thermal stores heated by electrical resistance heaters. With ohmic resistance, the power dissipated is proportional to the voltage across the electric heating device. If the system is designed for maximum power at 253V, the supplied voltage drops to 216V and the system draws only 73% of the designed power. Similarly, if the system is designed for maximum power at 216V, at 253V it draws 137% of the designed power.

[0310] One feature of the present invention is to design an electrical installation 110 with fixed ohmic electric heating devices 130 where, taken as a whole, the main fuse rating is exceeded for the network fuse 114 when all of the electric heating devices 130 are used at the maximum allowable voltage. It is not unusual to design a device that can exceed the safety protection and limits of the main power supply fuse in normal use. The system actively controls the current to the elements to keep it within acceptable limits. The advantage of this approach is that even when the voltage is at the minimum acceptable, the unit can still draw the same amount of current, e.g., 90A.

[0311] In one embodiment, the combined current draw capability of the electric heating devices 130 is at least 120% of the rated household power supply when all electric heating devices are operated at the grid voltage ceiling, i.e., 20% above the maximum current that can be drawn in the home. In this way, the impact of supply voltage drops on the performance of one or more heating devices can be substantially minimized.

[0312] Furthermore, to maximise the use of existing infrastructure, it is desirable to be able to charge the system at close to 100% of the household fuse rating, preferably around 90% of the household fuse rating. In the UK this means that if the household fuse is rated at 100A then the system will charge at 90A. Therefore if the system is designed for the higher voltage (253V) it will charge too slowly when the voltage is low. If the system is designed for the lower voltage (216V) it will draw too much current and the household fuse will blow when the voltage is high.

[0313] Additionally, most domestic electrical circuits have a variety of other devices connected to them that may be in use at any one time. As mentioned above, when heating the thermal storage system 112, it is desirable to maximise the utilisation of any electrical connections. This means that the control circuit 110a needs to be operable to ensure that the total current through the network fuses (i.e. the total current drawn by the heating circuits 129a-c and the domestic power supply 115) is kept strictly within the fuse limits.

[0314] The current sensor may take the form of a current clamp 116, where if other loads are switched on or off the control circuit 110a may vary the combined current drawn by the heating circuits 129a-c up or down accordingly.

[0315] In practice, the heat output of the thermal storage system 112 may vary with temperature. The hotter the mass, the greater the temperature difference and the greater the amount of power that can be extracted. Conversely, as the temperature of the thermal storage medium decreases, the maximum power output decreases until it is below a required minimum threshold. Having a thermal storage system with a variable heat output is undesirable for consumers. One solution is to restrict the unit to operate below a certain minimum temperature, i.e. to treat the thermal storage medium as "empty" when the power output is below a certain minimum output, even when usable heat is stored. In cold weather conditions, if the stored heat is insufficient, this may mean that the homeowner has to switch to direct electric heating, which is undesirable since the unit has stored usable thermal energy. A solution may be to switch on the charging circuit to the thermal storage mass and keep it running. If the charging rate is the same as the discharging rate, it is not different from direct electric heating of the home. The thermal storage mass does not change temperature and the electrical input is equal to the thermal output. However, if the charge rate is less than the discharge rate, as this relates to the temperature of the thermal mass, the temperature of the thermal mass will slowly decrease along with the power output from the unit, and as mentioned above, a decrease in heat output is undesirable.

[0316] A feature of most home heating is that a high power output (e.g. 30 kW) is only required at start-up to rapidly heat the water in the home heating circuit. As the temperature of the house increases, the required power output generally drops to a lower level (e.g. 5-10 kW). This means that it may be possible to provide the correct power output to the house from a lower temperature thermal storage mass. The homeowner can use the additional stored energy in the unit that would otherwise be treated as "empty". However, when operating within this temperature range, the demand for a high power output cannot be met.

[0317] FIG. 8 shows an electrical installation 110' based on the electrical installation 110 (common features are numbered accordingly), where each of the three heating circuits 129a-c' further includes an additional electric heating device 131, and all three heating circuits are each controlled by a variable current controller 121'.

[0318] As shown, an additional switch 123 is added between the variable current controller 121' and the electric heating device 130' of each heating circuit. The additional switch 123 may alter the flow of power between the electric heating device 130' and the additional electric heating devices 131. The three additional electric heating devices 131 may be part of the domestic heating circuit 113 and act as resistors to directly heat water in the circuit.

[0319] The overall controller 118' controls the variable current controller 121' and the switch 123 via control wiring 117' to ensure that the current drawn through the network fuse 114 remains within pre-set limits. The overall controller 118' is also connected by control wiring 117' to the heating circuit 113 and controls the supply of power to the additional electric heating device 131 to ensure that the target heat output is provided to the home as long as the current drawn is below the limit of the network fuse 114'.

[0320] As an example, a control routine may be executed to measure the temperature of the thermal storage system 112'. When the thermal storage temperature falls below a critical value and the system provides heat to the home heating system, the control circuit 110a' switches to boost mode. In boost mode, the flow to the home heating circuit is monitored, and if the temperature of the flow drops below the target output temperature, the control circuit switches power using the switch 123 to the additional electric heating device 131 (which may be positioned, for example, directly in the home hot water circuit). Since all the electric heating devices in 110' have variable power supplies, the controller may increase the power dissipated by the additional electric heating device 123 until the target output temperature for the home heating circuit is reached or until the current sensor 116' registers that the entire home system has reached a preset current limit. For example, if the network fuse 114' is rated at 100 A, a preset limit of 90 A may be set. If an occupant requires an additional 20A in the house to switch on one or more other electrical devices in the house, the maximum current that can be drawn by the charging circuit 110' is limited to 70A and the current drawn by the electric heating device 131 is limited. The control circuit 110a' allows the thermal storage system 112' to continue to provide heating energy to the building's hot water / central heating system, supplemented by direct electric heating.

[0321] In an alternative embodiment, the control circuit 110a' may be set to provide supplemental power by the additional electric heat device 131 whenever the system is outputting heat and if the temperature of the flow to the home heating system (e.g. hot water / central heating system in a building) falls below the target flow temperature. This alternative embodiment ensures that the unit not only provides a higher heat output on start-up, but also allows it to continue to supplement power output even when the heat storage temperature drops. The control circuit 110a' may also be set to only provide supplemental power if a pre-set signal is received, e.g. related to the price of electricity, i.e. supplemental power may only be provided if the price of electricity falls below a specified level.

[0322] In this way, a heat storage system is provided, in which one or more of the heating circuits can be switched from charging the heat storage system to direct heating of the water circuit by additional electrical elements in the water heating circuit. Preferably, direct electrical power is only added to the water circuit on demand to achieve the target output temperature of the system. This means that if the heat storage system can provide enough power for the house, for example when the house is at the target temperature, no additional electrical energy is required when a lower level of power is required. However, if full power is required in this situation, it can also be met by supplementing the power output directly from the heat storage medium.

[0323] This has the advantage that the homeowner can access the additional energy stored in the unit and at the same time only need to add a minimal amount of direct electric heating. For example, a 20 kW power feed to a home heating system and a thermal storage unit with a 30 kW heat output could be operated down to a level where the direct heat output from the thermal storage medium was only 10 kW, but still have the capacity to deliver 30 kW of heat energy on demand.

[0324] As mentioned above, in further embodiments, an additional electrical element may be used to provide more power than is needed directly to the water at start-up, helping to quickly raise the temperature of the water in the circuit so that heat is provided to the home more immediately. Furthermore, there may be a requirement to keep part of the heating circuit at a certain temperature even when heat is not needed by the home, and it may be simpler to use the same additional heating element to provide this low level of heat, rather than using a thermal storage mass to provide this heat.

[0325] In a home, the largest energy requirement is space heating, followed by hot water and charging electric vehicles (EVs). Most other individual loads in the home have small energy requirements in comparison, but they can draw large amounts of power for short periods of time. For example, a kettle switched on at the same time as an oven uses 10kW of a 20kW supply. In the future, it seems likely that homes will have more than one electric vehicle (EV), so managing the electrical loads could be important. When installing an EV charger, significant effort needs to be undertaken to provide the correct power connections to the EV charger. A thermal storage unit located outside the home has all the necessary wiring and controls to provide power to one or more EV chargers.

[0326] FIG. 9 shows a charging circuit 110″ based on the electrical installation 110 (common features are labelled accordingly) in which the variable current controller 121 is replaced by a further on / off current controller 120′ (thereby relying on the timing of switching to control the current supply to the heating circuit 129c″), and two further switches 123′ are added to the first and second heating circuits 129a″, 129b″ between two of the automated on / off current controllers 120′ and the multiple electric heating devices 130″. The further switches 123′ can redirect the flow of power between the electric heating devices 130″ and the electric vehicle charger 140. Each of the two electric vehicle chargers 140 can charge an individual vehicle.

[0327] The overall controller 118'' controls the on / off current controller 120' and the switch 123' to ensure that the current drawn through the network fuse 114'' stays within preset limits. The overall controller 118'' may switch power to an electric vehicle charger 140 or to an electric heating device 130'' within the thermal storage body.

[0328] As an example, a control routine may be executed that is set so that charging occurs during a preset daily period, such as between 0000 and 0600. The overall controller 118" registers that there have been electric vehicles connected to each of the electric vehicle chargers 140, as well as the charging status of each vehicle. The overall controller 118" may also register the amount of energy stored in the thermal storage system 112" and may use methods to predict home heating loads based on historical data based on external temperature as well as other conditions. The overall controller 118" may also implement several control strategies. It may be set to prioritize electric vehicle charging over home heating, with any remaining capacity being sent to the thermal storage system 112" via the electric heating device 130", ensuring that both systems are fully charged by the end of any given period. The overall controller 118" monitors the current sensor 116" to ensure that the current drawn through the network fuse 114" remains within preset limits. The overall controller 118" may prioritize charging of the electric vehicles over the thermal storage system 112" for any number of reasons, such as if desired by an operator. For example, if only one of the electric vehicle chargers 140 is operable to stay within the preset limits through the network fuse 114" (due to additional residential power demands), the overall controller 118" will prioritize charging of one electric vehicle. Once this electric vehicle requires less charge than the second electric vehicle, the overall controller 118" may charge the two electric vehicles in some alternating manner until both are fully charged. Only when both electric vehicles are fully charged does the overall controller 118" switch on one of the electric heating devices 130".

[0329] An alternating charging strategy may involve charging an electric vehicle as soon as it is connected to the electric vehicle charger 140, while only supplying power to the thermal storage system 112'' during a preset daily period, for example, 0000-0600. In another charging strategy, a preset signal related to the price of electricity may be received by the entire controller 118'', i.e., power is supplied only if the price of electricity falls below a specified level.

[0330] FIG. 10 shows a charging circuit 110''' based on electrical equipment 110'' (common features are numbered accordingly) in which the on / off current controller 120' associated with the third heating circuit 129c''' is replaced by a variable current controller 121'', and the first and second heating circuits 129a''', 129b''' are connected via a switch 123'' to an additional electric heating device 131' which can operate in the same way as the additional electric heating device 131 of the system of FIG. 8.

[0331] A switch 123'' can redirect the flow of power between the electric heating device 130''' and either the electric vehicle charger 140' or the additional electric heating device 131'. Each of the two electric vehicle chargers 140' can charge a respective electric vehicle. The two additional electric heating devices 131' are part of the domestic heating circuit 113'.

[0332] The charging strategy may include charging the electric vehicle as soon as the car charger 140' is plugged in, while only providing power to the thermal storage system 112''' at a set diurnal period, e.g., 0000-0600, where direct "boost" heating of the domestic hot water circuit by the additional electric heating device 131' is prioritized over the electric vehicle charger. In this case, if the domestic hot water circuit requires additional heat, the controller 118''' switches charging from the electric vehicle with the lowest charging requirement to the additional electric heating device 131'. If the temperature of the domestic hot water flow remains below the target temperature, the overall controller 118''' stops charging the second electric vehicle 140' charger and provides power to both the additional electric heating device 131'.

[0333] In this way, a thermal storage system is provided in which one or more of the heating circuits can be switched from charging the thermal storage system to charging the EV. As an example, a thermal storage system may have one variable 16A charge supply, one on / off 16A circuit and three on / off 32A circuits. The same unit may also supply 3x32A car chargers and 1x16A car charger using the on / off circuits.

[0334] The control circuit 110a can bring power to the various EV chargers whilst ensuring they are below the home supply rating, i.e. turning them on and off on demand using the same logic as that of electric heaters. This has the added benefit that the home owner or network operator can decide when to allow the units to charge and the control unit to switch them on and off.

[0335] Additionally, if the unit communicates with an EV that is plugged into the controller, the system can optimize charging for the needs of both the thermal store as well as the EV. For example, a home with 100 kWh storage and 2 x 50 kWh EVs plugged in could require anywhere between 0 and 200 kWh of energy, depending on the state of charge of the various devices. By having multiple charging points, multiple vehicles can remain plugged in at the same time, even when some are fully charged, providing two-way power: vehicle-grid or vehicle-home. An added benefit of multiple charging points is that charging can be offered to visitors even when the homeowner's EV is plugged in.

[0336] Finally, a combined controller that can switch power between an electric heater and an electric vehicle charging port is also highly desirable, as a single control unit can safely manage the interaction of the two largest potential electrical loads in a home - heating and electric vehicle charging.

[0337] FIG. 11 shows an energy storage system 200 including a primary circuit (steam circuit) 201 with a first heat transfer fluid (e.g. pure water), a thermal energy storage body 202, an evaporator heat exchanger 242, a condenser heat exchanger 241, a secondary circuit (non-steam circuit) 203 with a second heat transfer fluid (e.g. water with antifreeze), and a heating system 243 (e.g. a domestic heating circuit with a radiator).

[0338] The thermal energy store 202 includes a heat transfer medium 210 forming a heat transfer core, surrounded by insulation 211, including one or more electric heaters 206 supplied by electrical cables 205, and surrounding an evaporator heat exchanger 242 in intimate or direct contact with the block 210 and connected to a high pressure water pipe 207 and a steam pipe 208. The system also includes a low pressure water pipe 222 supplied from the condenser heat exchanger 241, a reservoir 231, a pressure boost pump 230, and control lines 290. The pressure boost pump 230 is supplied with electricity from a variable speed drive 263 via electrical cables 267. The pressure boost pump 230 is connected to a transfer pipe 234 and to both the desuperheating pipe 233 and the high pressure water pipe 207 via a desuperheating valve 232.

[0339] The thermal medium 210 may be a solid sensible heat material (e.g., an aluminum matrix with a solid thermal filler material embedded therein). During operation, the thermal medium 210 is heated by the electric element 206 to a temperature above 200° C. The thermal medium maximum temperature is likely to be below 700° C.

[0340] During operation, the pressure boost pump 230 is fed with water from the reservoir 231. The water pressure is increased by the pump 230 and injected into the transfer pipe 234 leading to the desuperheat valve 232. The desuperheat valve allows a small flow to enter the desuperheat pipe 233 to join the steam pipe 208 where the water flow evaporates into the steam flow, thereby cooling it. The majority of the flow passes from the desuperheat valve 232 into the high pressure water pipe 207 and then into the evaporator heat exchanger 242 where the water is boiled and converted into steam, taking heat from the block 210. The steam leaves the evaporator heat exchanger 242 via the steam pipe 208 and is cooled by the water flow from the desuperheat pipe 233 before entering the condenser heat exchanger 241. The steam is condensed in the condenser heat exchanger 241 by the cooling provided by the flow in the secondary circuit pipes 275 and 277. The reservoir 231 is optimally sized so that excess water is minimal when the system is running at full power. It may be preferable to add a float switch (not shown) to the reservoir 231 to ensure that the pressure rise pump 230 is only switched on when there is enough water in the reservoir 231 to supply the pressure rise pump 230.

[0341] Condensed water in the condenser heat exchanger 241 flows into the reservoir 231. The reservoir 231 is preferably in a position relative to the pressure rise pump 230 such that water from the reservoir is fed to the pump under gravity. The high pressure water pipe 207 preferably has a loop passing above the height of the reservoir so that the water contained in the reservoir can only flow if the pressure rise pump 230 is operable to prevent any siphoning. As an alternative option, a shut-off valve (not shown) is fitted to the high pressure water pipe 207 to close the pipe when the system is not running, ensuring that water cannot flow into the evaporator heat exchanger 242.

[0342] The pressure lift pump 230 is ideally a small positive displacement pump with a variable speed drive. The advantage of a positive displacement pump is that the mass flow of water is proportional to the speed, regardless of the delivery pressure. The flow rate of the pressure lift pump is varied to achieve a target temperature in the pipe 279, monitored by control line 290. If the temperature of the water in the pipe 279 rises above the target temperature, the speed of the pressure lift pump 230 is reduced, and vice versa. As an example, the target operating temperature in the pipe 279 may be 65°C.

[0343] There is an additional benefit from operating the water / steam system with a pump that can inject higher pressures. Keeping the internal volume of the evaporator heat exchanger 242 low is important as it reduces the amount of water that can be stored within the heat exchanger. If the volume is kept below 2 liters, the unit is considered very low risk from a certification standpoint.

[0344] The evaporator heat exchanger 242 may be made from a single section of pipe that is coiled to form a pipe circuit with a single inlet 242A and outlet 242B. Preferably, a single pipe is used, but multiple pipes are an option. Because the coils are evenly distributed within the heat transfer medium 210, the distance the heat needs to travel (to reach the pipe) is kept short. For larger block applications, sizing means longer to have more evenly distributed pipes. If the steam flow rate is high, the pipes preferably do not have sharp bends or sudden changes of direction. Injecting the water at high pressure means that a significant pressure drop may be allowed as the water, and therefore the steam, passes through the pipe. Increasing the pressure drop increases the heat transfer from the pipe to the water, but may generate a higher steam flow rate. The usual pipe design philosophy for steam would be to keep the steam velocity at the outlet 242B below 70km / hr. In this case, the advantage of a large pressure drop may mean that in some applications a pipe diameter (with a constant cross-sectional area) is selected to achieve a steam velocity at outlet 242B that is higher than 100 km / hr, 200 km / hr or even 300 km / hr at full power.

[0345] Since the steam velocity at the outlet 242B depends on the injector flow rate, the ratio of the effective internal cross-sectional area A of the pipe circuit to a predetermined maximum injection rate P (i.e., A / P) may be designed to be less than a predetermined value. For example, in one embodiment, A / P may be less than 20 (e.g., less than 16, e.g., less than 12). Thus, for every 1 g / s of water injected into the pipe at the maximum injection rate, the pipe cross-sectional area is reduced by 20 mm 2 Less than 16mm 2 Less than or even 12 mm 2 For example, at 10 g / s, the internal cross-sectional area of ​​the pipe is 200 mm 2 Less than 160mm 2 Less than or even 120mm 2 is less than.

[0346] The condenser heat exchanger 241 may be a plate heat exchanger. Another advantage of higher injection pressure and positive displacement pumps is that they can operate with pressure surges in the pipes. When injecting water into a high temperature pipe, the water boils and runs in a different boiling regime. This can lead to a sudden increase in steam volume and a sudden change in pressure. With a pump that is relatively insensitive to the delivery pressure, it is easy to maintain control with simple changes in mass flow that produce changes that closely resemble the heat output. The effect of pressure surges does not have any significant feedback that the control system needs to manage. If the high pressure pump 230 is replaced by something like a centrifugal circulation pump that operates at a lower pressure, the feedback from pressure surges will have a significant effect on the mass flow rate, making it difficult to manage the control system. The pump can also be damaged by pressure surges with the flow through the pump reversed.

[0347] Finally, the desuperheater 232 described below also requires a pressure drop to operate reliably, simplifying designs with higher operating pressures. The secondary circuit 203 includes pipes 270, 271, 272, 273, 274, 275, 276, 278 and 279. The circulation pump 254 is supplied from the battery system 262 via the electric cable 266, which is supplied with mains electricity via the electric cable 265. Other components include the buffer storage 255, the diverter valve 251, the pressure relief valve 253 and the expansion vessel 252. The heating system 243 and the condenser heat exchanger 241 are connected via the secondary circuit 203. The heating system 243 may have a flow control valve to restrict the flow of water. If there is a flow control valve in the circuit, it is necessary to install the diverter valve 251 in the circuit. The heating system 243 is for space heating (e.g. central heating system) or for providing hot water or both. The condenser heat exchanger 241 transfers heat from the thermal energy storage 202 to the secondary circuit 203.

[0348] In operation, the water in the secondary circuit 203 may be water or a mixture of water and antifreeze, but for simplicity will be referred to as water in this description. The circuit is preferably pressurized and maintained at this pressure by an expansion tank 252 connected to the piping circuit via pipe 270. The advantage of pressurization is that the water temperature can be raised to above 100°C without boiling. The heated water flows from the condenser heat exchanger 241 via pipe 279 to the circulation pump 254.

[0349] The circulation pump 254 increases the water pressure before the water enters pipe 278. The water enters the diverter valve 251 and passes to pipe 271 and the heating system 243, or passes to pipe 273 and bypasses the heating system 243, or a combination of some passing through the heating system 243 and some bypassing through pipe 273. The diverter valve 251 allows flow into pipe 273 if pressure in the circuit increases. This occurs when a flow control valve (not shown) restricts the flow through the heating system 243. The diverter valve 251 ensures that there is always flow through the condenser heat exchanger 241 when the circulation pump 254 is running.

[0350] Water leaving heating system 243 in pipe 272 is cooled by the heating load. Any water joining from pipe 273 is at or near the target operating temperature. As a result, when the heat load decreases, the return temperature in pipe 274 tends to rise closer to the operating temperature. Pressure relief valve 253 is installed between pipe 274 and pipe 276 with a pressure relief setting that is above the normal operating pressure provided by expansion vessel 252.

[0351] Return water in pipe 276 enters buffer reservoir 255 and exits buffer reservoir 255 into pipe 275. Buffer reservoir 255 tends to be at or below the operating temperature of the system, except at shutdown, when the temperature of buffer reservoir 255 rises. The water in pipe 275 enters condenser heat exchanger 241 and is heated to near the target operating temperature. As mentioned above, the speed of pressure boost pump 230 is varied to ensure that the heat extracted from thermal energy store 202 matches the heat load.

[0352] The flow rates between the two pumps 230, 254 are very different. For each kW of power required, the pressure rise pump 230 needs to process approximately 0.4 g of water per second. For 30 kW of power, this equates to 12.5 g of water per second. For the same 12.5 g of water per second through the pressure rise pump 230, the circulation pump 254 circulates 700 grams of water per second in the secondary circuit, i.e. 50x times more water flows. These two pumps therefore have very different purposes and operating conditions.

[0353] The pressure lift pump 230 may have a preset maximum flow rate that is related to the temperature of the heat transfer medium 210. When the temperature of the heat transfer medium 210 drops, the amount of water that can be evaporated per second by the evaporator heat exchanger 242 decreases below the normal operating range. If the pressure lift pump 230 were to operate at full speed in this scenario, the evaporator heat exchanger 242 would slowly become flooded or the reservoir 231 would become empty. A controller for the pressure lift pump 230 may limit the water injection rate of the pressure lift pump to a preset level that ensures that the evaporator heat exchanger 242 does not become flooded. These preset flow rates may be related to the temperature of the heat transfer medium 210.

[0354] The present invention addresses several different situations that may arise during shutdown under different circumstances: The system operates at a total thermal power of 30 kW, with the pressure rise pump 230 injecting 12.5 g / s of water. The operating temperature of the water in the secondary circuit is 75° C. The heat carrier is at 350° C. and 150 g of water in the condenser heat exchanger 241 evaporates at any one time. When the heat load is switched off, a signal is sent via control line 291 to the battery system 262 to keep powering the circulation pump 254 for a set period of time. A further signal is sent via control line 292 to the VSD controller 263 to switch off the power to the pressure rise pump 230. In this way, water is not further injected into the high pressure water pipe.

[0355] When the heating load is stopped, the flow control valve (if installed) in the heating system 243 may close and the diverter valve 251 opens to allow the flow to bypass the heating system 243. When the heating system 243 is bypassed, there is no heat load. Therefore, as the steam still in the evaporator heat exchanger 242 evaporates, it condenses and significantly raises the water temperature in the secondary circuit above the normal operating temperature of 75°C. If there is insufficient thermal mass in the pipes, the water will start to boil and the pressure relief valve 253 will open. This is obviously undesirable since switching off the heating load is a normal occurrence. To prevent this from happening, it is necessary to add sufficient thermal mass to the system in the form of a buffer reservoir 255, which holds a certain mass of water sufficient to absorb all the heat from the condensation of the steam. Preferably, the size of the buffer reservoir 255 is sufficient to store the energy from the condensed steam from the total mass of pure water in the steam circuit. As the steam condenses, the temperature in pipes 279, 278, 273, 274, 276 and 275 increases as the temperature of the water in buffer reservoir 255 increases, in this case from the normal operating temperature of 75° C. to 95° C. The secondary circuit 203 is pressurized by expansion vessel 252 to 1 bar gauge so there is no risk of boiling.

[0356] When the system is restarted immediately after being shut down, the water temperature in the pipes leaving the buffer storage 255 is all at 95° C. As mentioned above, the pressure rise pump 230 is set to start injecting water when the water temperature in the pipes 279 drops below the operating temperature - in this case 75° C. This means that when a heat load is added to the system, the pressure rise pump 230 will not engage until the system is effectively "reset", i.e., the water in the buffer storage 255 and pipes 279, 278, 271, 272, 274, 276 and 275 all drop below normal operating temperature again before the pressure rise pump 230 starts injecting water to extract heat from the hot core. In this way, the system is designed to safely condense all of the steam generated by the thermal energy storage 202, while being able to be safely shut down repeatedly from full power, without having to vent any steam from the primary steam circuit 201.

[0357] A less common event could be a power outage, so the circulation pump 254 has no power to circulate the water. In this scenario, there is a risk that the primary steam circuit 201 will need to bleed steam to avoid high pressure. To avoid this, the system is fitted with a battery system 262, which means that even if there is a power shortage, the circulation pump 254 can continue to run until all the steam is safely condensed. Note that in a power shortage, since there is no power supply to the pressure rise pump 230, this is no different to a normal shutdown from full power, in that the heat from condensation ends up in the piping and buffer reservoir 255.

[0358] The final failure mode to consider is either failure of the circulation pump 254 or loss of water in the secondary circuit. In this situation, if it occurs at full power, there may be insufficient thermal mass in the condenser heat exchanger 241 to condense the steam sufficiently. In this scenario, pressure will build up in the steam pipes 208 and 225 until the steam pressure relief valve 227 opens and vents the steam via the relief pipe 226 to a safe space, e.g., a drain hole. In this way, the steam can be safely managed even if the secondary circulation system fails completely. The failure modes suggested, i.e., pump or secondary piping fluid leakage, require attendance by a service engineer. Refilling the drained reservoir 231 with pure water is part of the necessary visit to repair the system.

[0359] Thus, an energy storage system 200 is proposed that has a thermal energy store 202 that extracts heat via steam but is able to safely manage all potential failure modes.

[0360] The desuperheat valve 232 allows a percentage of high pressure water to be injected upstream of the condenser heat exchanger 241 to reduce the temperature of the steam entering the condenser heat exchanger 241. If the thermal core 210 is at 500°C, it is possible for the steam leaving the core to be at or near this temperature. From a safety and practical standpoint, this high temperature is undesirable. Low cost brazed heat exchangers are not designed to manage these temperatures. Hot pipes can cause combustion. The desuperheat valve 232 and desuperheat pipe 233 can be replaced with a small diameter pipe. This can be designed so that under full flow conditions some water will transfer to the steam pipe. If there is excess water, this will remove any superheat from the steam flow and allow saturated steam and water to enter the condenser heat exchanger 241. The steam temperature should be less than 200°C, preferably less than 150°C.

[0361] FIG. 12 shows an embodiment in which an additional electric heating device 131 from the charging circuit 110' of FIG. 8 is added to the energy storage system 200 of FIG. In this example, an electric heating device 131 is added to the buffer reservoir 255 and can take the form of a simple electric heating coil of the type used as an immersion heater in hot water tanks.

[0362] FIG. 13a shows a further embodiment of a vacuum insulated thermal store 10″ based on the thermal store 10 (common features are numbered accordingly) for use in the energy storage system 200 of FIG.

[0363] As shown, the thermal mass 10″ includes a solid sensible heat storage material 14″ (e.g., an aluminum matrix with a solid thermal filler material embedded therein) in which a heat exchanger 13″ and a heat source 6″ are embedded. The heat source 6″ is connected by wires to a controller 118 (not shown). The sensible heat storage material 14″ is contained in an inner container 40″ and connected to an outer container 50″ by a neck connector 60″ to form a vacuum tight space 11″. As with the thermal mass 10 of FIG. 1a, 50-200 layers of multi-layer insulation (not shown) are wrapped around the inner container 40″ to partially fill the vacuum tight space 11″.

[0364] The vacuum is created by an integral vacuum system 20'' which is connected to an outer vessel 60''. The outer vessel 60'' is also fitted with several fittings, these being a transport system 30''.

[0365] Extending downwardly into the thermal energy store 202" between the solid sensible heat storage material 14" is a coiled tube which forms the heat exchanger 13" and is made of a suitable material such as stainless steel. The two ends of the tube 13" are connected to pipes 7" and 8". In the illustrated arrangement for the heat exchanger 13", there is one downward spiral coil pipe with a straight return. The tube is bonded to the solid sensible heat storage material 14", which is particularly applicable when the storage block material is metal.

[0366] The solid sensible heat storage material 14" may be heated to temperatures above 200°C by one or more embedded electric heating bodies 6". Heat may be extracted from the solid sensible heat storage material 14" by passing a working fluid through a heat exchanger 13" via pipe 7" and out of the heat exchanger 13" via pipe 8", where the working fluid entering the heat exchanger 13" is cooler than the sensible heat storage material 14". The working fluid may be, for example, pure water.

[0367] In operation, a working fluid, for example water 2, is stored in the reservoir 231 (as shown in cross section with water level in FIG. 13a) and is pumped into the inlet pipe 8" by the pressure rise pump 230. The water boils to steam in the heat exchanger 13" and leaves via outlet pipe 7". The steam enters the condenser heat exchanger 241 where it is cooled by a secondary stream entering via pipe 275. The secondary stream is heated by the condensing steam and leaves the condenser heat exchanger 241 via pipe 279 at a higher temperature. The steam condenses to water in the condenser heat exchanger 241 and flows back to the reservoir 231 before flowing back into the pressure rise pump 230.

[0368] Between pipes 8″ and 7″ is the desuperheating pipeline 233, which injects water into pipe 7″ to reduce the steam temperature. A variable orifice valve could be used to control the mass flow rate of water injected into pipe 7″ and in turn the level of desuperheating, but an alternative is a simple pipe, i.e. the desuperheating pipeline 233″, which does not require any moving parts. The desired level of desuperheating can be set by adjusting the geometry with respect to length and inner diameter only. This makes it possible to tailor (within the functional tolerances) the required desuperheating (mass flow rate of water injected into pipe 7″) over the entire operating range. The speed of desuperheating is achieved by matching the head loss in the pipe. If properly designed, over the entire operating range the mass flow through the desuperheating pipeline 233 follows the water injection into pipe 7″ without undershoot (overcooling) or overshoot (undercooling).

[0369] Apart from the solid sensible heat storage material 14" and the multi-layer insulation 12", all major components are preferably made from a suitable metal or alloy, such as steel. FIG. 13b shows an embodiment of a non-vacuum insulated thermal store 10''' based on the thermal store 10'' (common features are numbered accordingly) for use in the energy storage system 200 of FIG. 11, without the outer container 50'' and the integrated vacuum system 20''. The inner container 40''' may be surrounded by conventional insulation.

[0370] Figure 14 shows how the energy storage system 200 of Figure 11 can be combined with the vacuum insulated thermal store 10 of Figure 1a. A number of electric thermal masses 6 are shown. A high pressure water pipe 207 connects to an inlet pipe 7 and then to a heat exchanger 13. An outlet pipe 8 from the heat exchanger 13 connects with a steam pipe 208.

[0371] FIG. 15a shows a prior art vacuum vessel 410, including an outer vessel 450 that encloses a region of vacuum 403. The outer vessel 450 has additional reinforcing ribs 402 welded to the outer shell (cylindrical portion) of the vessel. Thin-walled vacuum vessels generally fail by buckling along the parallel-walled shell. Failure occurs at a lower buckling load if the shell is long relative to its diameter. The shell can be strengthened by welding reinforcing ribs 402 to the outside of the shell. These ribs shorten the effective length of the shell, and R equally spaced ribs reduce the effective length by 1 / (R+1). The resistance to buckling scales as the cube of R, so a small number of ribs significantly increases the critical buckling load.

[0372] FIG. 15b shows a vacuum vessel 400 including an outer vessel 450 and an inner vessel 440 connected by a neckpiece 460 and enclosing an area of ​​vacuum 403. The outer vessel 450 includes a cylindrical outer shell 450a with upper and lower domed portions 450b. As shown, the outer shell 450a is reinforced by an internal helical coil 404 that is welded to the outer vessel 450 at fastening points 405 and 406. More than two fastening points can be used so that there are multiple points where the coil is fastened to the inside of the outer vessel 450. The helical coil 404 has the same effect as welding 14 reinforcing ribs to a vessel of the same thickness. Increasing the number of coil turns increases the effective number of ribs, R. The cross section of the coil can be round, square, or annular (pipe). This design has several advantages.

[0373] When the diameter of the outer shell is large, the wall thickness of the outer shell may be thin. - The use of multiple coil turns reduces the thickness required for each coil turn, which means there is more available space between the inner and outer shells for adding insulation (e.g. MLI).

[0374] - The coils hold the outer shell round and reduce ovality, especially when preloaded, which may reduce the requirements for fixation when welding to the end domes.

[0375] - During manufacture, the coil is preloaded and allowed to slide into place internally, meaning that the outer wall of the outer shell remains cylindrical. - The coils may be preloaded to introduce tension into the outer cylindrical section when unloaded, which may aid in structural stability.

[0376] - The coil structure is stabilized by the outer shell and therefore this is an efficient structure. - The helical coil can be made of low-cost carbon steel even if the outer vessel is made of a more expensive material such as stainless steel.

[0377] The welding effort required is minimized compared to the installation of external ribs. - The coil is in a vacuum so there is no corrosion. Figure 15c i-iii) shows a prior art spring. When a helical spring is under axial load, as shown in i), the diameter of the spring remains constant. When a torque is applied to the helical spring in the direction of the helix, the diameter of the spring decreases, as shown in ii). When a torque is applied against the direction of the helix, the diameter of the spring increases, as shown in iii).

[0378] Figures 15d i)-iii) show how the vacuum vessel 450 is assembled. Figure 15d i) shows a portion of the outer vessel 451 with the helical coil 404 twisted (torqued in the same direction as the helix) to reduce the outer diameter of the coil. The coil is lowered into the shell while held in this reduced diameter state. Figure 15d ii) shows the same vessel 450 with the torque removed or reduced to the point where the end of the helical coil 404 contacts the inner wall of the portion of the outer vessel 451. In Figure 15d iii) the ends of the coil are welded within the portion of the outer vessel at points 405 and 406 and the torque is removed. The helical coil can be installed in a slack state or in a pre-torqued state. When pre-torqued, the outer cylindrical section is left in tension while the helical coil is compressed. When left in a compressed state, friction may hold the helical coil in place and no welding may be necessary to attach the helical coil to the container 450.

[0379] FIG. 15e shows a vacuum vessel 400' based on the vacuum vessel 400, including an outer vessel 450' and an inner vessel 440' connected by a neckpiece 460' and surrounding an evacuated region 403'. The outer vessel 450' includes a cylindrical outer shell 450a' with upper and lower dome-shaped portions 450b', and the inner vessel 440' includes a cylindrical outer shell 440a with upper and lower dome-shaped portions 440b. The outer shell 450a' is reinforced by an internal helical coil 404a, and the inner shell 440a is reinforced by an internal helical coil 404b. The inner vessel 440' is in tension during use from vacuum and is generally thin-walled compared to the outer vessel. However, during manufacture, it is necessary to test that the welds on the inner vessel are leak-tight using helium gas. The simplest way to perform this inspection is to pull a vacuum on the inner vessel 440' and inspect the welds for leaks by blowing helium onto them. When a leak path is presented, the helium is transferred to the inner vessel 440' and to a sensor (not shown). Because the inner vessel may not have the mechanical strength to support a vacuum, the addition of the coil 404b serves to stabilize the inner vessel under external pressure loads to prevent buckling. Therefore, the coil 404b remains in the inner vessel 440' after the inspection is performed. In many cases, the addition of this coil 404b provides the simplest and lowest cost solution for inspection / checking for weld integrity.

[0380] FIG. 16a shows a vacuum insulated pipe 300 including an outer pipe 350, an inner pipe 340 wrapped in n layers of MLI 312. The area between the outer pipe 350 and the inner pipe 340 forms a space 303, which is a vacuum. The outer pipe 350 may be in sections 310, each section 310 supported internally by a helical coil 304, which may be inserted prior to assembly. The helical coil 304 is welded to the inside of the outer pipe 350 at fastening points 305 and 306. The helical coil may be preloaded so that the outer pipe 350 is in radial tension. More than one fastening point may be used so that there are multiple points where the coil is fastened to the inside of the outer pipe 350.

[0381] When transporting hot or cold liquids, the outer pipe 350 may remain close to the surroundings. As a result, it is preferred if the thermal expansion or contraction of the inner pipe 340 upon heating or cooling is limited. If there is thermal expansion or contraction, this needs to be allowed for by using expansion areas (e.g. expansion joints or bellows).

[0382] 16b shows a vacuum insulated pipe 300' that includes an outer pipe 350, an inner pipe 340 encased in an MLI 312. The area between the outer pipe 350 and the inner pipe 340 forms a space 303, which is a vacuum. The outer pipe 350 may enter into sections 310, and each section 310 may have an expansion area in the form of half a bellows arrangement 324, 325 at each end.

[0383] The outer pipe 350 is supported on the outer support 320 and outer rollers 321. The weight of the inner pipe 340 and fluid is supported by n layers of MLI through the inner support 322 and inner rollers 323. When assembling the pipes, each bellows section 324, 325 is welded, swaged or rolled to form a vacuum tight seal. The bellows sections allow each outer section of the pipe to expand or contract slightly as the ambient conditions change. The inner pipe 340 can expand and contract by moving on the rollers 323. The outer pipe 350 can expand or contract and moves on the rollers 321.

[0384] An advantage of the present invention is that it is possible to make large diameter thin walled pipes, which means that features such as flexible bellows can be formed. The outer material can be stainless steel, which protects the inner pipe from both corrosion and damage.

[0385] As described in this patent, the pipe may be wrapped with n layers of MLI. Alternatively, other insulation materials may be used, such as microporous insulation. As previously described herein, a vacuum may be drawn by a vacuum device to the vacuum level of the MLI. Alternatively, if a different material is used for the insulation, a vacuum may be drawn to a different vacuum level.

[0386] 17 shows a vacuum insulated thermal store 500 including an inner vessel 540 and an outer vessel 550, the inner vessel 540 defining a chamber 515 containing a liquid sensible heat storage material 514 (e.g., water) and including a heating element 506, an inlet pipe 510, a diffuser 571, an outlet pipe 570, and a sealed sensor tube 513 including a plurality of thermocouples 572. The heating element 506 and the plurality of thermocouples 572 are connected to a controller (not shown) via electrical wires 505. A lower neck connector 560 extends through the base portions 540a, 550a of the inner and outer vessels 540, 550, respectively, and includes an optional inner neck plate element 563, which is attached to a neck tube 562, which is in turn attached to an outer neck plate 561. The weight of the inner vessel 540 and the liquid sensible heat storage material 514 is supported from the outer vessel 550 by the neck connector 560. The inner container 540, the outer container 550, and the neck connector 560 form a vacuum space 511. A total of n layers (where n is at least 10 layers per 100 degrees Celsius temperature difference between ambient and peak operating temperature) of multi-layer insulation ("MLI") 512 are wrapped around the inner container 540 to partially fill the vacuum space 511. A coiled support structure 504 located between the outer container 550 and the MLI 512 supports the outer container 550.

[0387] The vacuum is created by an integrated vacuum system 520, which is connected to an outer vessel 550 and functions in a manner similar to the integrated vacuum system 20 detailed above with reference to Figures 1-3. The outer vessel 550 also includes a transport interface system 530.

[0388] The liquid sensible heat storage material 514 may be heated by one or more electric heating bodies 506. Liquid may be drawn from the inner vessel 540 via outlet pipe 570. Liquid is automatically added via inlet pipe 510 as water is drawn off. A diffuser 571 may be used to allow stratification and reduce mixing within the liquid sensible heat storage material 514. When storing hot liquid, the diffuser 571 may typically be located in the lower section 540c of the inner vessel 540, with the outlet pipe 570 drawing liquid from the higher section 540b of the inner vessel 540.

[0389] The neck tube 562 defines a central chamber 545 that houses the supply lines for one or more heating elements 506 (e.g. electrical cables for one or more electric heating elements), the supply lines for the thermocouples 572 (e.g. electrical cables for multiple thermocouples), the thermocouple tube 513 and the inlet / outlet pipes 510 and 570. The central chamber 545 is located at the bottom of the vessel, since the hot liquid store can be thermally stratified. This means that all of the connections are located in the area that is the coldest and therefore closest to the surroundings, thereby reducing heat loss. For cold liquid stores (e.g. stores at below ambient temperature), the central chamber 545 may be located at the top of the vessel.

[0390] The transport system 530 includes an outer plug 532 and an inner plug 531. The outer plug 532 is a tube welded to the outer container 550. The inner plug 531 is a tube or rod welded to the inner container 540, which extends through the MLI 512 and is partially surrounded by the outer plug 532. The outer plug 532 restrains the movement of the inner plug 531 in a direction perpendicular to the tube axis, but does not touch the inner plug 531 in normal use. This means that when side loads are applied to the inner container 540 during transport, any movement due to contact is restrained, but minimal heat transfer occurs at rest. The loads are usually much lower when transporting containers suitable for liquids, since the containers can be filled when in their final position. With cast-in-place solid storage media, the loads on the inner container are usually much higher and may require improved support structures as previously described.

[0391] A further advantage of the transport system 530 is that it may provide permanent support if the container is stored in a horizontal orientation. In this situation, the gap between the two bungs may be smaller and bearing material may be added to one or more of the surfaces. This allows for the expansion and contraction of the inner container 540 as it heats and cools relative to the outer container 550.

[0392] In operation, the heater 506 heats the adjacent liquid, which rises under buoyancy. When the reservoir is at a constant temperature, this heating method tends to raise the reservoir temperature uniformly throughout. The only area that remains cold is the volume of liquid below the heater 506.

[0393] FIG. 18 a ) shows a self-cleaning vacuum insulated hot water tank 600 based on the vacuum insulated heat store 500 of FIG. 17 , including a self-cleaning module 680 . The vacuum insulated hot water tank 600 includes an inner vessel 640 and an outer vessel 650, the inner vessel 640 defining a stratification chamber 615 for storing hot water 614 in a thermally stratified state. By managing stratification, the volume of usable hot water available from the tank can be maximized for a given heat input. Consider the heating of a fixed volume of water V by a defined amount of heat H. This heat is defined by uniformly increasing the temperature of V from 15C to 30C. The same amount of heat H therefore increases V / 2 from 15C to 45C, while the remaining V / 2 remains at 15C. When the usable water is considered to be water above 40C, the addition of stratification increases the amount of usable hot water from 0 to V / 2. It can therefore be seen that by managing stratification, the amount of usable water available from the hot water tank can be maximized. Thermodynamic mixing, which breaks the stratification, has the opposite effect, decreasing the volume of usable hot water available. It is therefore important to maintain stratification once achieved.

[0394] As shown, the vacuum insulated hot water tank 600 includes an electric heating element 606, a cold water inlet pipe 610, a diffuser 671, a primary hot water outlet pipe 670, and a sealed sensor tube 613 containing a plurality of thermocouples 672. The electric heating element 606 and the plurality of thermocouples 672 are connected to a controller (not shown) via electrical wires 605. A lower neck connector 660 extends through the base portions 640a, 650a of the inner and outer vessels 640, 650, respectively, and includes an optional inner neck plate element 663, which is attached to a neck tube 662, which is in turn attached to an outer neck plate 661. The weight of the inner vessel 640 and stored hot water 614 is supported from the outer vessel 650 by the neck connector 660. The inner vessel 640, the outer vessel 650, and the neck connector 660 form a vacuum space 611. A total of n (where n is at least 10 layers per 100 degrees Celsius temperature difference between ambient and peak operating temperature, e.g., n is at least 50 layers total) layers of multi-layer insulation ("MLI") 612 are wrapped around the inner vessel 640 and partially fill the vacuum space 611. A coiled support structure 604 located between the outer vessel 650 and the MLI 612 supports the outer vessel 650.

[0395] The vacuum is created by an integrated vacuum system 620 that is connected to the outer vessel 650 and functions in a manner similar to the integrated vacuum system 20 detailed above. The outer vessel 650 also includes a transport interface system 630.

[0396] Water 614 may be heated by one or more electric heating elements 606 and may be drawn from the inner vessel 640 via a hot outlet pipe 670. Water (e.g., cold water) is automatically added via the inlet pipe 610 as hot water is drawn off. A diffuser 671 may be used to allow stratification and reduce mixing within the inner vessel 640. The diffuser 671 is located in the lower section 640c of the inner vessel 640, and the hot outlet pipe 670 draws hot water from the upper section 640b of the inner vessel 640.

[0397] The neck tube 662 defines a central chamber 645 which houses the supply lines for one or more heating elements 606 (e.g. electrical cables for one or more electric heating elements), the supply lines for multiple thermocouples 672 (e.g. electrical cables for multiple thermocouples), the thermocouple tube 613, and the inlet / outlet pipes 610 and 670. The central chamber 645 is located at the bottom of the vessel so that the hot liquid mass can be thermally stratified. This means that all of the connections are located in the area that is the coldest and therefore closest to the surroundings, thereby reducing heat loss.

[0398] Delivery system 630 includes outer plug 632 and inner plug 631. Outer plug 632 is a tube welded to outer container 650. Inner plug 631 is a tube or rod welded to inner container 640, which extends through MLI 612 and is partially surrounded by outer plug 632. Outer plug 632 restrains movement of inner plug 631 in a direction perpendicular to the tube axis, but does not touch inner plug 631 in normal use.

[0399] The self-cleaning module 680 includes a secondary outlet line (warm water pipe 682) which is connected to a mixing valve 681. As shown, the warm pipe 682 is connected through the central chamber 645 and operates to provide the tank with a "self-cleaning" capability, allowing loose limescale and debris to be removed from the tank. In a conventional tank, the hot water outlet feeds a mixing valve where it is mixed with water from the cold mains. The mixing valve blends the hot and cold water, either in a fixed ratio, for example 1:5, or thermostatically, to reduce the temperature to a pre-set level. In the UK the outlet from the mixing valve is typically set at around 50°C.

[0400] In this embodiment, the mixing valve 681 is fed from a warm pipe 682 with a warm pipe inlet 603 located at the base 640a of the inner vessel 640. Cold water is added to the hot water tank 640 via a diffuser 671 located near the warm pipe inlet 603. When hot water is pumped from the top of the tank via the hot outlet pipe 670, cold water enters the tank and replaces it via the inlet pipe 610 and the diffuser 671. At the same time, if the water entering the mixing valve 681 via the hot outlet pipe 670 is above a pre-set temperature, the mixer 681 adds water to the mixing valve 681 via the warm pipe inlet 603 / warm pipe 682. This flow in the warm pipe 682 entrains loose mineral particles (e.g. lime scale) that would otherwise settle to the bottom of the tank. In general, the higher the tank temperature, the larger the warm flow from 682 required to balance it, and the better the self-cleaning effect. Hot water at the correct outlet temperature leaves mixing valve 681 via pipe 687 with debris entrained in the flow.

[0401] This self-cleaning capability is applicable to all hot water tanks, not just vacuum insulated tanks. Advantageously, by providing a self-cleaning action during the discharge phase, debris such as limescale can be flushed from the tank and easily exited via a connected domestic hot water outlet (e.g. shower or hot water tap / drink). This avoids the need for a filter / debris settling area that can get clogged and / or require regular servicing.

[0402] FIG. 18b shows a further embodiment of a self-cleaning vacuum insulated hot water tank 600' based on hot water tank 600 (common features are labelled accordingly) in which an additional mixing valve 691' has been added in series with the mixing valve 681'. There is a potential safety issue in feeding the mixing valve 681' from the warm pipe 682' which may result in an excessively high hot water outlet temperature. If the entire tank is hot, any hot water initially pumped from the tank via the mixing valve 681' will be fed by hot water from both the warm pipe 682' and the hot outlet pipe 670'. This means that at start-up there may be a temporary event where the output from the mixing valve exceeds a pre-set level. For long runs of pipe this is not an issue as heat losses will cool the initial hot water flow. However, if the hot water tap is located close to the hot water tank it may be dangerous as the initial water flow may exceed the safety temperature. This may be solved by having two mixing valves in series as shown. The first mixing valve 681' is fed from a hot outlet pipe 670' and a warm pipe 682'. An outlet pipe 687' from the first mixing valve 681' feeds a second mixing valve 691' to be mixed with water from the cold mains from the cold inlet pipe 610' via a connector pipe 692'. The output from the second mixing valve 691' ensures that the hot water output via pipe 694' never reaches an unsafely high temperature, with a permanent supply of cold water. If the output from the first mixing valve 681' falls below a pre-set temperature, the second mixing valve 691' will not function, allowing the flow to exit via pipe 694'.

[0403] Having two mixing valves 681' and 691' provides an additional level of safety and allows the hot water tank to operate at a higher temperature than normal, for example 85° C. The mixing valves 681' and 691' may be set to the same pre-set output temperature or may be set to different temperatures.

[0404] FIG. 18c shows a further embodiment of a self-cleaning vacuum insulated hot water tank 600″ based on the hot water tank 600′ (common features are labelled accordingly) in which a cold inlet pipe 610″ is located concentrically within the warm pipe 682″. In this way, flow into and out of the tank is symmetrical, which can be beneficial to minimise mixing within the tank if stratification is desired.

[0405] FIG. 19a) shows a further embodiment of a vacuum insulated hot water tank 700 based on the hot water tank 600'. The vacuum insulated hot water tank 700 includes an inner vessel 740 and an outer vessel 750, with the inner vessel 740 defining a stratification chamber 715 for storing hot water 714, a "cold" inlet pipe 710, a diffuser 771, a hot outlet pipe 770, and a sealed sensor tube 713 including a plurality of thermocouples 772, in a state where the hot water is thermally stratified by an electric heating element 706. The electric heating element 706 and the plurality of thermocouples 772 are connected to a controller (not shown) via electrical wires 705. A lower neck connector 760 extends through each of the base portions 740a, 750a of the inner and outer vessels 740, 750, and includes an optional inner neck plate element 763, which is attached to a neck tube 762, which is in turn attached to an outer neck plate 761. The weight of the inner vessel 740 and the stored hot water 714 is supported from the outer vessel 750 by the neck connector 760. The inner container 740, the outer container 750, and the neck connector 760 form a vacuum space 711. A total of n (where n is at least 10 layers per 100 degrees Celsius temperature difference between ambient and peak operating temperature, e.g., n is at least 50 layers total) layers of multi-layer insulation ("MLI") 712 are wrapped around the inner container 740 to partially fill the vacuum space 711. A coiled support structure 704 located between the outer container 750 and the MLI 712 supports the outer container 750.

[0406] The vacuum is created by an integral vacuum system 720 that is connected to the outer vessel 750 and functions in a manner similar to the integral vacuum system 20 detailed above. The outer vessel 750 also includes a transport interface system 730.

[0407] As in the previous embodiment, water 714 may be heated by one or more electric heating elements 706 and may be drawn from the inner vessel 740 via a hot outlet pipe 770. Water (e.g., cold water) is automatically added via the inlet pipe 710 as hot water is drawn off. To allow for stratification and reduce mixing within the inner vessel 740, a diffuser 771 is located in the lower section 740c of the inner vessel 740, and the hot outlet pipe 770 draws hot water from the upper section 740b of the inner vessel 740.

[0408] Delivery system 730 includes outer plug 732 and inner plug 731. Outer plug 732 is a tube welded to outer container 750. Inner plug 731 is a tube or rod welded to inner container 740, which extends through MLI 712 and is partially surrounded by outer plug 732. Outer plug 732 restrains movement of inner plug 731 in a direction perpendicular to the tube axis, but does not touch inner plug 731 in normal use.

[0409] The hot water tank 700 has a self-cleaning function as described in Figures 18a)-18c) provided by a self-cleaning module 780 and includes a secondary outlet line (warm pipe 782) connected to a mixing valve 781. Hot water at the correct outlet temperature leaves the mixing valve 781 via pipe 787 with debris being entrained in the flow.

[0410] Apart from this self-cleaning function, it is desirable to maintain stratification within the hot water tank and to minimize heat loss. When stratification is maintained, cold water is added to the bottom of the tank whenever hot water is removed from the top of the tank. Because cold water has a higher density than hot water under otherwise equal conditions, the tank will naturally tend to stratify.

[0411] By having a hot exit pipe at the top of the tank that passes through the tank wall, you create a heat loss path through the insulation. Most tanks are kept hot or partially hot so hot water is available on demand. A hot exit pipe from the top of the tank creates a permanent heat dissipation path that can be significant and equal in magnitude to the heat loss from the entire tank through the insulation. Therefore, from a heat loss standpoint, it is much better to avoid this. One option is to have the hot water pipe pass through the tank and exit the tank through the base as shown in Figures 18a-c). The problem with hot water being pumped from the top of the tank through a tube and exiting the bottom of the tank is that the hot water leaving there will transfer heat to the cold water at the bottom of the tank. This heat transfer naturally creates a convection system that breaks up the stratification in the tank.

[0412] It is easy to remove hot water from the bottom of the tank via pipes, but at the same time it has the consequence that it is not easy to maintain stratification in the tank. If stratification is maintained, the heat losses will be lower because the lowest temperature is at the bottom of the tank and any heat flow along the pipes will be absorbed by the cold water. This cold water is replenished each time hot water is pumped from the tank.

[0413] Additionally, it is important to know the temperature profile within the hot water tank in order to determine how and when the user will input / output heat from the tank. Measuring the temperature at different heights within the tank can be accomplished by placing a sensor on the exterior of the tank. In this form, the sensor accurately measures the temperature but is not easily replaceable if the tank is insulated with, for example, solid polyurethane foam. It is clearly preferable to have a sensing method that can be replaced but still accurately measures the water temperature.

[0414] A simultaneous solution to solve the two problems described is shown in FIG. 19a), where a hot water outlet pipe 770 draws water from the upper region 740b of the tank and is mounted in a hot water dispenser module 713 that includes an outer sleeve / sensor pipe 713a that is open to the atmosphere at the base and sealed to the hot water outlet pipe 770 near the top. The outer sleeve 713a defines a sleeve chamber 713b that has sufficient internal volume into which a thermocouple 772 can be inserted to measure the temperature of the wall of the outer sleeve 713a and therefore the water temperature at each level of the hot water tank. The thermocouple is not in contact with the hot water outlet pipe 770. In this way, the hot water outlet pipe 770 is insulated (by air) from the water in the tank and does not break the stratification in use. At the same time, space is provided within the outer sleeve 713a to accommodate multiple thermocouples. A self-cleaning arrangement similar to that shown in Figures 18a-c) may also be installed, where the tank is vacuum insulated but functions just like a conventionally insulated tank.

[0415] As shown, the neck tube 762 defines a central chamber 745 that houses the hot water dispenser module 713 along with inlet / outlet pipes 710 and 782 and supply lines for one or more heating elements 706 (e.g., electrical cables for one or more electric heating elements).

[0416] Fig. 19b) shows an arrangement 700' based on the hot water tank 700 (common features numbered accordingly), where all of the pipes are combined to create a four-pipe concentric arrangement, which combines the self-cleaning feature with an insulated hot outlet pipe and replaceable thermocouple. This arrangement can be used with either vacuum insulated or conventional insulated hot water tanks. It should be noted that for vacuum insulated tanks, this is an added benefit, since the number of holes that need to go through the evacuated space is minimized. The internal and external temperatures of a vacuum insulated tank can be very different, and thermal expansion needs to be managed. Minimizing the number of feedthroughs makes the assembly of the vessel simpler and cheaper.

[0417] As shown, the hot water dispenser module 713' includes an outer sleeve 713a' that defines a sleeve chamber 713b' configured to accommodate both the hot water outlet pipe 770' and a replaceable thermocouple 772' that is placed against the inner wall of the outer sleeve 713a' and does not touch the outer wall of the hot outlet pipe 770'. The hot water dispenser module 713' is located within the cold inlet pipe 710' for a portion of its length, and a diffuser 771' is attached to the exterior of the hot water dispenser module 713'. Thus, a portion of the cold inlet pipe 710' is located within the warm pipe 782'.

[0418] FIG. 20a) shows an embodiment of a hot water tank 700″ that is based on the four concentric pipe embodiment from FIG. 19b) (common features are numbered accordingly) but where the heating of the water occurs with an external heating module 795 from either an indirect heat source, such as a heat pump or boiler, or a direct heat source, such as an electric immersion heater. Furthermore, this embodiment allows the water in the hot water tank to be heated from the bottom up of the tank, i.e., the coldest water first, or from the top down, or both simultaneously, ideally while maintaining temperature stratification within the tank.

[0419] The hot water tank 700 ″ includes connecting pipes 759 , 789 , 764 , 769 , water pumps 784 and 765 , optional electronic magnetic descalers 785 , 766 , an electric heater 768 , and heat exchangers 786 , 767 .

[0420] FIG. 20b) shows the operation of the external heating module 795 during the charging phase, where hot water is added to the top of the tank, thereby heating the upper portion of the tank. During operation, cold water from the bottom of the tank is pumped through the diffuser 771″ and flows in the reverse direction through the cold inlet pipe 710″ to the water pump 765 via the connecting pipe 764. The water pump 765 pumps the water through an optional electronic / magnetic descaler 766 before entering an optional heat exchanger 767 and an electric heater 768. The optional heat exchanger may be connected to a heat source such as a heat pump or boiler. The electric heater may be used to provide all the heat or to supplement heat up to a pre-set temperature. Hot water is pumped to the top of the hot water tank via the connecting pipe 769 and the hot outlet pipe 770″. Note that in this mode of operation, the hot water travels in the hot outlet pipe 770″ in the opposite direction to the direction in which the hot water is pumped from the hot water tank. Similarly, water pumped through cold inlet pipe 710" travels in the opposite direction to the direction hot water is pumped from the tank. A warm pipe 782" could also feed the pump, but there is a risk that limescale debris could enter the pump or block filters within the pump when pumped from the bottom of the tank. Therefore, a cold inlet pipe 710" is used.

[0421] The supply of heat can be provided at the same time that hot water is pumped from the hot water tank, with part of the hot water coming from the heater and the remaining demand coming from the hot outlet pipe 770″. When heating hot water tanks with electric elements, it is common for limescale to form, especially in "hard water" areas. The amount of limescale that accumulates increases with temperature. Limescale that builds up on the elements tends to make them run hotter and permanently fail, so it is preferable to avoid / minimize limescale formation for component life. Electronic descalers apply an electromagnetic field to the pipes carrying the water to reduce the amount of limescale that forms. Magnetic descalers can have a similar effect.

[0422] These types of descalers are generally installed on the cold water inlet pipe to the property. Installation in this location has several disadvantages: The descaler is in operation all the time. It is used on all water entering the property, not just the water that is being heated. The effect of these descalers on limescale formation is time-limited. If cold water enters the hot water tank and this is not heated immediately, the effect is limited. This is probably why the effect of these devices is reported in the literature with various conflicting conclusions. After study, it is apparent that locating the optional descaler immediately upstream of the electric heater 768" ensures maximum impact of treatment. Treatment should occur a minimum of 1-20 seconds before the water is heated, and no more than 10 minutes (e.g., 1-600 seconds before the water is heated, e.g., 2-600 seconds before the water is heated, e.g., 10-600 seconds before the water is heated, e.g., 20-600 seconds before the water is heated). The electronic descaler only needs to operate when the heater is operational, so there is no power requirement when there is no heat requirement. Operation time is limited. Since electronic (or magnetic) descalers are installed and used in this way, it is possible to use higher power arrangements. Installing and using these electronic (or magnetic) descalers in this way tends to significantly reduce the formation of limescale, producing a deposit in the water rather than on the surface. This is why such descaling arrangements are used in conjunction with "self-cleaning" hot water tanks, since the majority of limescale is fine "dust" rather than larger particles, and this fine dust can be easily removed via a connected domestic hot water outlet (e.g. shower or hot water tap / drink). Electronic and magnetic descalers are poorly understood and have a diverse history. It has been discovered by the inventors that the effect of the descaler on the water is time limited in some applications. This means that if the water passes through the descaler and is left there for a period of time (hours to days) before heating, the effect of the descaler will be minimal. Similarly, if the water is heated immediately after passing through the descaler, the effect will also be reduced, which is why a time delay between treatment and heating is preferred. The descaler pulls dissolved CO2 out of the solution as tiny bubbles.When the water is heated and its solubility is reduced, this results in calcium carbonate forming in the water as fine granules around these tiny bubbles, rather than on the heated surfaces as tends to happen with untreated water. Scaling on surfaces is significantly reduced, occurring mostly as a fine suspension.

[0423] The location of the descaler is important since most homeowners install this device on the cold incoming water supply to the home. If the homeowner has a combi boiler, this is an effective strategy. If the homeowner has a hot water tank, it is much less effective. The cold water is pumped into the tank and remains there for a period of several hours before being heated. This embodiment of the invention only applies to descaling water that is just about to be heated. It has been found that there is an optimal minimum time between when the water is treated and when it is heated, which is related to the strength of the descaler and the diameter of the pipe. This is preferably at least 1-10 seconds, but not more than 10 minutes (e.g. 1-600 seconds before the water is heated, e.g. 2-600 seconds before the water is heated, e.g. 10-600 seconds before the water is heated, e.g. 20-600 seconds before the water is heated). In this location, the descaler has the greatest impact in reducing limescale formation on and around the heating element. Furthermore, this approach tends to form the limescale as a fine suspension, so in combination with the self-cleaning concept means it is particularly effective at keeping the tank clean. Normal limescale formation produces large, thick flakes on the surface which are not well suited to this removal process and can cause problems elsewhere in the piping.

[0424] FIG. 20c) illustrates the operation of the external heating module 795 during the charging phase to heat the water in the lower section of the tank. During operation, cold water from the bottom of the tank is pumped through the diffuser 771″ and flows through the cold inlet pipe 710″ and in the reverse direction via the connecting pipe 759 to the water pump 784. The pump 784 sends the water through an optional electronic / magnetic descaler 785 before entering the heat exchanger 786 where it is heated by water from a primary heat source such as a boiler powered by natural gas or a heat pump or some other similar device. Warm water is pumped into the bottom of the hot water tank via the connecting pipe 789 and the warm pipe 782″. Note that in this mode of operation, the warm water travels in the opposite direction to the direction in which it is pumped out of the unit to the mixer valve. Similarly, the water pumped through the cold pipe 710″ travels in a different reverse direction than when hot water is pumped out of the unit and fresh cold water enters. A warm pipe 782" could also be used to feed the pump, but there is a risk that limescale will get into the pump or block the filter in the pump when pumped from the bottom of the tank. Therefore, a cold pipe 710" is used.

[0425] The heat supply can be provided at the same time that hot water is pumped from the hot water tank. This configuration allows the heat pump or boiler to operate in a mode with high efficiency since the heat pump always heats the coldest water first.

[0426] FIG. 20d shows the external heating module 795 in self-cleaning mode during the discharge phase. Hot water is pumped from the hot water tank via the outlet pipe 794″ from the mixing valve 791″. The mixing valve 791″ is supplied with cold water from the inlet pipe 710″ via the connecting pipe 792″ and from the outlet pipe 787″ supplied from the mixing valve 781″. The mixing valve 791″ pumps cold water only if the water in the outlet pipe 787″ is above a pre-set temperature. The mixing valve 781″ is supplied from the warm pipe 782″ and the hot outlet pipe 770″. Cold water flows into the hot water tank via the pipe 710″ and the diffuser 771″. When discharging hot water, there must always be a flow of cold water in this direction, even if some cold water is pumped to supply the mixing valve 791″.

[0427] Figure 21i) shows a proposed "neck region" 800 based on the neck connector 60 of the vacuum insulated thermal store 10 shown in Figure la. The neck region 800 comprises an inner vessel top 842 and an outer vessel top 852 separated by a vacuum space 811, and a neck connector 860 comprising a lower neck plate 863 element attached to a neck tube 862, which in turn is attached to an upper neck plate 861. The inner vessel part 842 is attached to the outer vessel part 852 by the neck connector 860.

[0428] Both the inner vessel top 842 and the outer vessel top 852 are typically made from semi-elliptical heads. They are pressed components where the height of the dome is equal to half the radius. These types of domes are widely used in pressure vessels and provide a compromise between low height and thin thickness.

[0429] In this embodiment, the neck tube 862 is attached to two thick plates 861 and 863, which are then welded to the domes 842 and 852. Since the thickness of the plates can be substantial, significant welding may be required to join the plates to the thin domes and tubes, as large fillets are required to avoid large stress concentrations. The result is a rigid structure that is still subject to high bending stresses at this neck connector 860 when lateral loads are applied to the inner container. Significant loads may occur during shipping.

[0430] The vacuum between the upper inner vessel 842 and the upper outer vessel 852 places a load on the upper outer vessel 852, which is in compression, and the upper inner vessel 842, which is in tension. The upper inner vessel 842 must also support the weight of any thermal mass, and acts to transfer this weight to the outer vessel 852 via the neck.

[0431] FIG. 21ii) shows an improved neck configuration 800'. The upper inner container includes an inner neck portion 840 including a lower concave tapered dome-shaped neck portion 843 and an upper tubular neck portion 844, the lower tapered dome-shaped neck portion 843 being connected to a convex shoulder region 842a of the inner container 842' (portions 843 and 842a together form a convex-concave dome portion 845). The upper outer container 852' includes an outer neck portion 850 including a concave tapered dome-shaped neck portion 853 being connected to a convex shoulder region 852a of the outer container 852' (portions 853 and 852a together form a convex-concave dome portion 855). The two containers are joined with a modified neck plate 861'. The convex-concave sections can be produced by spinning or pressing. The tubular neck portion 844 is generally a separate piece that can be welded to the concave tapered domed neck portion 843, with both portions having similar material thickness. The tubular neck portion can be part of the same piece, for example, made by spinning, but this is a more complicated process depending on the length of the tubular neck portion. Having similar material thickness minimizes stress concentrations to aid in welding. The concave dome design allows for optimized stress distribution within the portion, which in turn allows for a significant reduction in thickness.

[0432] In terms of material required, using this approach can reduce the total mass by 50% compared to the conventional approach used in FIG. 21i). Additionally, the tubular neck portion 844 provides a longer path for heat to travel, thus reducing heat loss. In combination with the thinner walls and therefore reduced cross-sectional area, this approach reduces the total heat loss by more than a factor of 4x.

[0433] Figure 21iii) shows a further embodiment of the neck form 800”. This is similar to 800’, but the upper outer container includes an upper tubular neck portion 870. This lengthens the tubular neck portion 844’ of the inner neck portion 840’. The two containers are joined by a modified neck plate 861”. The extension provided by the tubular section 870 creates a longer conduction path, reducing heat loss beyond that provided by 800’.

[0434] Figure 22 shows an improved neck form 800’. The convex-concave dome portion 845 formed by portions 843 and 842a is generally described by a composite curve, but in its simplest form can be considered to be made of a convex section and a concave section, which intersect at a tangent. The vertical height of the convex-concave dome portion formed by portions 843 and 842a is A1. The width is B1. The point of inflection occurring between the convex section and the concave section is marked I1 and is located by the positions (C1, D1). This parameterization (A1, B1, C1 & D1) is appropriately selected when explaining cases of combinations of height-to-diameter and, importantly, axial compression (buckling) and circular bending loads corresponding to the shape / profile. Note that in the case of a pressure vessel where the load is purely internal pressure, height-to-diameter is the only important quantity, as in the case of a simple semi-elliptical dome portion.

[0435] In one embodiment, it may be convenient to use profiles that are approximately equal for the convex and concave sections. In this case, the design is constrained by A1 / B1, and the location I1 is fixed by choosing C1 / B1 = 0.5 and D1 / A1 = 0.5. It is preferable to have A1 / B1 of the same magnitude that enables constraints on both height and weight. The design preferably has 0.3 < A1 / B1 < 1.0, but may be constrained to 0.1 < A1 / B1 < 1.0.

[0436] In practice, any number of composite curves (e.g., elliptical or circular) can be used for the convex and concave sections, and the overall shape can be set using I1 as a control point. In this case, the design is constrained by the values of C1 / B1 and D1 / A1. The design should ideally have 0.25 < C1 / B1 < 0.75, but may be relaxed to 0.35 < C1 / B1 < 0.65 if it is difficult to achieve the end profile. The design should also ideally have 0.25 < D1 / A1 < 0.75, but may be relaxed to 0.35 < D1 / A1 < 0.65 if it is difficult to achieve the end profile.

[0437] The considerations of geometric shapes also apply to the convex-concave dome portion 855. In the case of equal profiles, the design is constrained by A2 / B2, and the point I2 is fixed by selecting C2 / B2 = 0.5 and D2 / A2 = 0.5. It is preferable to have A2 / B2 of the same magnitude as that enabled by the constraints of both the convex-concave dome portion 855 and the weight. The design should ideally have 0.3 < A2 / B2 < 1.0, but may be constrained to 0.1 < A2 / B2 < 1.0.

[0438] Again, in practice, there can be any number of composite curves, and here the design is constrained by the values of C2 / B2 and D2 / A2. The design should ideally have 0.25 < C2 / B2 < 0.75, but may be relaxed to 0.35 < C2 / B2 < 0.65. The design should also ideally have 0.25 < D2 / A2 < 0.75, but may be relaxed to 0.35 < D2 / A2 < 0.65.

[0439] Figure 23 shows an embodiment of a vacuum insulated thermal storage body 890 based on the thermal storage body 500 of Figure 17 in an inverted position with a neck region 800''' based on the neck region 800' of Figure 22ii) at the base of the container. The inner container includes an inner neck portion 840'' including an upper concave tapered dome-shaped neck portion 843'' and a lower tubular neck portion 844'' attached to a convex shoulder region 842a''. The lower outer container includes a concave dome portion 855''. The two vessels are joined at a modified neck plate 861"'. Water enters through inlet pipe 882 and exits through outlet pipe 881. An inner membrane 880 is physically added to separate the neck region from the portion of the chamber that stores the thermal mass, thereby maximizing the conduction path length to the neck region. Pipes 881 and 882 are welded to this inner membrane. The inner membrane 880 and tubular neck portion 844" create a longer path for heat to move from the thermal mass, thus reducing heat loss.

Claims

1. 1. A thermal storage body for an energy storage system, comprising: an inner container containing a thermal energy storage body; an outer container surrounding the inner container, the inner container and the outer container being separated by a vacuum region extending between the inner container and the outer container.

2. 2. The thermal storage element according to claim 1, wherein the vacuum pressure in the vacuum region is between 0.05 mbar and 1 mbar.

3. 3. The thermal storage body of claim 2, comprising a vacuum pump operable to maintain the vacuum pressure in the vacuum region.

4. 4. The thermal store of claim 3, wherein the thermal store comprises sensors operable to measure a parameter at one or more locations in the thermal store, and the vacuum pump is configured to operate whenever the sensors indicate that the parameter has reached a predetermined value.

5. The thermal storage element according to any one of claims 1 to 4, further comprising a thermal insulator provided within the vacuum region.

6. 6. The thermal storage element of claim 5, wherein the thermal insulation comprises n layers of multi-layer insulation wrapped around the outer wall of the inner container, each layer of the multi-layer insulation comprising a reflective layer and a spacer layer, and n≧50.

7. 7. The thermal storage element of claim 6, wherein n is about 200.

8. one or more electric heating elements operable to act as heat inputs to said thermal energy storage element; A thermal storage body according to any one of claims 1 to 4, comprising one or more heat exchangers operable to receive a heat transfer fluid.

9. The thermal storage body according to claim 8 , wherein the thermal energy storage body is a solid storage body, and the one or more electric heating elements and the one or more heat exchangers are each embedded within the solid storage body.

10. 10. The thermal storage body of claim 9, wherein the thermal energy storage body comprises a solid body including a solid thermally conductive matrix having a solid thermal filler material embedded therein, the solid thermally conductive matrix forming a thermally conductive pathway to the solid thermal filler material dispersed within the solid thermally conductive matrix.

11. A thermal storage body according to any one of claims 1 to 4, configured to heat the thermal energy storage body to a temperature above 300°C.

12. 5. The thermal storage body according to claim 1, wherein the inner container is suspended within the outer container by a neck connector connecting an upper section of the inner container to an upper section of the outer container, the neck connector supporting the weight of the inner container and the thermal energy storage body and comprising a central chamber accommodating supply lines for the thermal energy storage body.

13. 5. The thermal storage element according to claim 1, wherein the outer container has an interface for engaging with a transport device, the interface comprising one or more sockets provided on the outer container, the one or more sockets being configured to receive transport bolts provided on the transport device.

14. 14. The thermal storage body of claim 13, further comprising one or more spreader plates movable between an inoperative position and a deployed position, wherein in the deployed position the spreader plates are operable to inhibit movement of the inner container relative to the outer container.

15. 5. The thermal storage element of claim 1, further comprising an internal brace disposed within the vacuum region, the internal brace configured to engage an inner surface of the outer vessel and to resist compression of the outer vessel.

16. 16. The thermal storage element of claim 15, wherein the inner surface of the outer vessel has a generally cylindrical profile and the internal brace has a generally annular profile when viewed along a longitudinal axis of the internal brace.

17. 16. The thermal storage element of claim 15, wherein the internal brace is a radially expandable brace expandable between a radially contracted configuration and a radially expanded configuration.

18. The thermal storage element of claim 17 , wherein the radially expandable brace is biased in the expanded configuration.

19. 20. The thermal storage element of claim 18, wherein the radially expandable brace is preloaded to apply tension to the inner surface of the outer vessel.

20. 18. The thermal storage element of claim 17, wherein in the radially expanded configuration, the radially expandable brace fits snugly inwardly against the inner surface of the outer vessel.

21. 18. The thermal storage element of claim 17, wherein the radially expandable brace is a torsion brace configured to be urged to radially expand when under tension.

22. 22. The thermal storage element of claim 21, wherein the torsion brace comprises a cage or coil structure.

23. 23. The thermal storage element of claim 22, wherein the torsion brace comprises a helical coil structure.

24. A vacuum insulated container, an inner container; an outer container surrounding the inner container, the inner container and the outer container being separated by a vacuum region extending between the inner container and the outer container; an internal brace disposed within the vacuum region, the internal brace configured to engage an inner surface of the outer container and to resist compression of the outer container.

25. 25. The vacuum insulated container of claim 24, wherein the inner surface of the outer container has a generally cylindrical profile and the internal brace has a generally annular profile when viewed along a longitudinal axis of the internal brace.

26. 26. The vacuum insulated container of claim 24 or 25, wherein the internal brace is a radially expandable brace expandable between a radially contracted configuration and a radially expanded configuration.

27. 27. The vacuum insulated container of claim 26, wherein the radially expandable brace is biased in the expanded configuration.

28. 30. The vacuum insulated container of claim 27, wherein the radially expandable brace is preloaded to apply tension to the inner surface of the outer container.

29. 27. The vacuum insulated container of claim 26, wherein in the radially expanded configuration, the radially expandable brace fits snugly inwardly against the inner surface of the outer container.

30. 27. The vacuum insulated container of claim 26, wherein the radially expandable brace is a torsion brace configured to be urged to expand radially when under tension.

31. 31. The vacuum insulated container of claim 30, wherein the torsion brace comprises a cage or coil structure.

32. 32. The vacuum insulated container of claim 31, wherein the torsion brace comprises a helical coil structure.

33. 26. The vacuum insulated container according to claim 24 or 25, wherein the vacuum pressure in the vacuum region is 0.05 mbar to 1 mbar.

34. 34. The vacuum insulated container of claim 33, comprising a vacuum pump operable to maintain the vacuum pressure in the vacuum region.

35. 35. The vacuum insulated container of claim 34, wherein the vacuum insulated container comprises a sensor operable to measure a parameter at one or more locations in the vacuum insulated container, and the vacuum pump is configured to operate whenever the sensor indicates that the parameter has reached a predetermined value.

36. 26. The vacuum insulated container according to claim 24 or 25, further comprising an insulating material provided within the vacuum region.

37. 37. The vacuum insulated container of claim 36, wherein the insulation comprises n layers of multi-layer insulation wrapped around the outer wall of the inner container, each layer of multi-layer insulation comprising a reflective layer and a spacer layer, and the insulation comprises 10 or more layers of multi-layer insulation per 100 degrees Celsius temperature differential across the vacuum region.

38. 38. The vacuum insulated container of claim 37, wherein the insulation comprises 20 or more layers of insulation per 100 degrees Celsius temperature differential across the vacuum region.

39. 39. The vacuum insulated container of claim 38, wherein the insulation comprises 40 or more layers of insulation per 100 degrees Celsius temperature differential across the vacuum region.

40. A vacuum insulated pipe, an inner pipe section; an outer pipe section surrounding the inner pipe section, the inner pipe section and the outer pipe section being separated by a vacuum region extending between the inner pipe section and the outer pipe section; an internal brace disposed within the vacuum region, the internal brace configured to engage an inner surface of the outer pipe section and to resist compression of the outer pipe section.

41. 41. The vacuum insulated pipe of claim 40, wherein the inner surface of the outer pipe section has a generally cylindrical profile and the internal brace has a generally annular profile when viewed along a longitudinal axis of the internal brace.

42. 42. A vacuum insulated pipe according to claim 40 or 41, wherein the internal brace is a radially expandable brace that is expandable between a radially contracted configuration and a radially expanded configuration.

43. 43. The vacuum insulated pipe of claim 42, wherein the radially expandable brace is biased into the expanded configuration.

44. 44. The vacuum insulated pipe of claim 43, wherein the radially expandable brace is preloaded to apply tension to the inner surface of the outer pipe section.

45. 43. The vacuum insulated pipe of claim 42, wherein in the radially expanded configuration, the radially expandable brace fits snugly inwardly against the inner surface of the outer pipe section.

46. 43. The vacuum insulated pipe of claim 42, wherein the radially expandable brace is a torsion brace configured to be urged to radially expand when under tension.

47. 47. The vacuum insulated pipe of claim 46, wherein the torsion brace comprises a cage or coil structure.

48. 48. The vacuum insulated pipe of claim 47, wherein the torsion brace comprises a helical coil structure.

49. A vacuum insulated pipe according to claim 40 or 41, wherein the vacuum pressure in the vacuum zone is between 0.05 mbar and 1 mbar.

50. 50. A vacuum insulated pipe according to claim 49, comprising a vacuum pump operable to maintain the vacuum pressure in the vacuum region.

51. 51. A vacuum insulated pipe as described in claim 50, wherein the vacuum insulated pipe comprises a sensor operable to measure a parameter at one or more locations in the vacuum insulated pipe, and the vacuum pump is configured to operate whenever the sensor indicates that the parameter has reached a predetermined value.

52. 42. A vacuum insulated pipe according to claim 40 or 41, further comprising insulation disposed within the vacuum region.

53. 53. A vacuum insulated pipe as described in claim 52, wherein the insulation comprises n layers of multi-layer insulation wrapped around the outer wall of the inner pipe section, each layer of multi-layer insulation comprising a reflective layer and a spacer layer, and the insulation comprises 10 or more layers of multi-layer insulation per 100 degrees Celsius temperature difference across the vacuum region.

54. 54. A vacuum insulated pipe as defined in claim 53, wherein the insulation comprises 20 or more layers of insulation per 100 degrees Celsius temperature differential across the vacuum region.

55. 55. A vacuum insulated pipe as defined in claim 54, wherein the insulation comprises 40 or more layers of insulation per 100 degrees Celsius temperature differential across the vacuum region.

56. 42. A vacuum insulated pipe according to claim 40 or 41, wherein the outer pipe section comprises one or more expansion zones, and the vacuum insulated pipe further comprises one or more external supports operable to support the outer pipe section.

57. 57. The vacuum insulated pipe of claim 56, wherein the one or more external supports are configured to slidably engage the outer pipe section.

58. 42. A vacuum insulated pipe according to claim 40 or 41, further comprising one or more internal supports operable to support the inner pipe section.

59. 59. The vacuum insulated pipe of claim 58, wherein the one or more internal supports are configured to slidably engage the inner pipe section.

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