Thermal store

Abstract

A thermal store 10 comprising a self-supporting shaft 100 in the ground 60 and, fixed at least partially in the self-supporting shaft, a container 120 defining a chamber 150 that is configured to stor

Description

TECHNICAL FIELD

[0001] The present invention relates to thermal stores, heat storage systems, heat energy transfer systems, methods of manufacturing thermal stores, and methods of transferring heat energy. BACKGROUND

[0002] District heating networks utilise thermal stores to store and provide heat energy, also referred to as “heat” herein, to a network of buildings. The thermal store typically includes a container that contains water, or another fluid, comprising the heat energy.

[0003] The heat energy may be provided to the thermal store from a heat energy source, such as a power station, that is near to or remote from the thermal store. The water containing the heat energy may be provided to, or extracted from, the thermal store via associated pipework. SUMMARY

[0004] A first aspect of the present invention provides a thermal store comprising a self-supporting shaft in the ground and, fixed at least partially in the self-supporting shaft, a container defining a chamber that is configured to store fluid comprising heat energy. The self-supporting shaft comprises a hole defined by the ground and a self-supporting structural support in contact with, and supporting, the ground defining the hole. The chamber is elongate and is oriented so that a longitudinal axis of the chamber is within twenty degrees of vertical. The thermal store comprises at least one flow path that opens into the chamber.

[0005] By providing the self-supporting shaft in the ground, and providing the at least part of the container in the self-supporting shaft, the at least part of the container is located underground. This may reduce an amount of space taken up by the container above ground compared to a container that is entirely above ground, or may allow a larger container to be provided for the same above-ground space requirement. This may also allow a larger thermal store to be provided in a built-up environment, such as a city, than might be possible if the container were to be located entirely above-ground.

[0006] Providing the self-supporting structural support that supports the ground defining the hole may allow a size of the self-supporting shaft and container to be greater than with a shaft that does not comprise the self-supporting structural support that supports the ground defining the hole. This is because, by providing the self-supporting structural support, the container itself need not support the ground that defines the hole. This is in contrast to simply digging a hole and providing a container in the hole. In that case, the container would need to support the ground, which may limit a size of the hole and / or container that can be provided. It is to be noted that with a container comprising, e.g., an inner layer defining a chamber along with an outer skin, and / or a layer of insulation, the respective layers would form a single self-supporting unit, and would not individually be self-supporting. Thus, such an insulation layer and / or outer skin would not form a “self-supporting” structure that supports the ground - instead, it would be the entire container that supports the ground. In the present invention, the structural support is self-supporting, so that the container need not have sufficient strength to support the ground.

[0007] Providing that the chamber is elongate and oriented so that a longitudinal axis of the chamber is within twenty degrees of vertical may allow a larger chamber to be provided for a given available horizontal “footprint” above or below the ground, or may allow a footprint of the container to be reduced for a given volume of the container. In this way, a large (e.g., deep) chamber may be provided even in a location where there is limited horizontal space available above or below the ground, such as in an urban or otherwise built-up area.

[0008] Optionally, the longitudinal axis of the chamber is vertical. This may reduce a footprint of the chamber for a given volume of the chamber, or allow a larger chamber to be provided for a given available footprint.

[0009] Optionally, the fluid is a liquid, so that the container is configured to store the liquid. Optionally, the container is configured to store water, such as liquid water. Water may be a readily-available resource for storing the heat energy in the thermal store, which may provide a low-cost solution for storing the heat energy in the thermal store.

[0010] Optionally, the container abuts the structural support. In this way, the self-supporting structural support may also absorb stresses on the container due to fluid in the chamber. This is particularly valuable as a depth of the container increases, whereby a pressure of fluid in the chamber on the container increases with depth. Thus, by providing the container abutting the self-supporting structural support, a depth, and therefore volume, of the chamber may be increased compared to a case where the container is unsupported by the self-supporting structural support.

[0011] Optionally, the container occupies at least a majority of a space defined by the structural support. This may increase a volume of the chamber for a given size of the self-supporting shaft.

[0012] Optionally, the container comprises thermal insulation, for thermally insulating the chamber from the ground external to the self-supporting shaft. The thermal insulation may reduce a rate of transfer of the heat energy from the fluid in the chamber to the ground, as compared to a container without such thermal insulation. This may allow the thermal store to store heat at a given temperature for a longer period, which may improve a quality of the fluid that the thermal store is able to provide to other systems.

[0013] Optionally, the thermal insulation has a thermal conductivity of less than 0.045 Watts per metre-Kelvin, such as less than 00.036 Watts per meter-Kelvin. Optionally, the structural support has a wall thickness that is greater than, such as more than 1.5 times, more than 2 times, or more than 2.5 times, a wall thickness of the thermal insulation. Optionally the structural support has a wall thickness of greater than 0.8 metres, such as greater than 0.9 metres, such as 0.95 metres. Optionally, the structural support has a wall thickness of up to 1 metre, or greater than 1 metre. Optionally, the structural support has a wall thickness of less than 1 metre. Optionally, the thermal insulation has a wall thickness of up to 0.3 metres, up to 0.4 metres, up to 0.5 metres, or greater than 0.5 metres. Optionally, the thermal insulation has a wall thickness of less than 0.5 metres. Optionally, the thermal insulation comprises a cellular glass insulation, such as Foamglas® insulation. Optionally, the thermal insulation comprises a mineral wool material, such as Rockwool®. Optionally, the thermal insulation, such as the mineral wool material, is provided over an upper end of the chamber.

[0014] Optionally, the container comprises a liner between the chamber and the thermal insulation. The liner may provide a barrier between the fluid in the chamber and the thermal insulation, which may reduce interactions between the fluid in the chamber and the thermal insulation. This may reduce a likelihood of degradation of the thermal insulation, and even of the self-supporting structural support, due to the liquid in the chamber. The liner may provide a leakproof barrier between the chamber and the thermal insulation, which may aid in retaining a given quantity of the fluid in the chamber, thereby increasing a heat storage capacity of the fluid in the chamber.

[0015] Optionally, the liner defines the chamber. Optionally, the thermal insulation defines the chamber. For instance, optionally, the liner is not provided. In such cases, the thermal insulation may have limited or no adverse interactions with the fluid in the chamber, in use, and / or the thermal insulation itself may provide a leakproof barrier between the fluid in the chamber and the self-supporting structural support and / or the ground.

[0016] Optionally, the thermal insulation comprises a layer of thermal insulation on the self-supporting structural support. In this way, the self-supporting structural support may also provide structural support to the thermal insulation, and / or the container as a whole.

[0017] Optionally, the self-supporting structural support comprises at least one (e.g., reinforced) concrete structure. Concrete, and particularly reinforced concrete, is a proven and readily available material for strong structures in many areas of construction, such as in buildings. Providing the concrete structure may provide the strength required for the self-supporting structural support to support the ground defining the hole, and / or to support the fluid contained in the chamber in use.

[0018] Optionally, the self-supporting structural support comprises a plurality of annular structures, such as (e.g., reinforced) concrete annular structures. This may permit ease of transport and / or installation of the self-supporting structural support. Optionally, the plurality of annular structures are stacked on top of each other and thereby form the self-supporting structural support. This may provide flexibility in a depth of the self-supporting structural support. For instance, providing a greater number of annular structures may permit a greater depth of the self-supporting structural support, and thus the chamber, in the ground.

[0019] Optionally, the chamber has a circular cross-sectional area orthogonal to the longitudinal axis. This may allow a stress on the container caused by fluid in the chamber to be distributed more evenly around a perimeter of the container compared to a chamber with a non-circular, such as a polygonal, cross-sectional area.

[0020] Optionally, the chamber has a volume of more than 100 cubic metres. Providing a chamber with a volume of more than 100 cubic metres may allow the thermal store to store an amount of the heat energy that is suitable for industrial use, such as for providing to a district heating network. This is in contrast to a chamber having a volume of less than 100 cubic metres, which may be more suited to storing thermal energy for use by a single household, for example.

[0021] Optionally, the chamber has a volume of more than 150 cubic metres, more than 250 cubic metres, or more than 600 cubic metres. Optionally, the chamber has a volume of up to 1,000 cubic metres, up to 10,000 cubic metres, up to 25,000 cubic metres, or more than 25,000 cubic metres. Increasing a volume of the chamber may increase a heat energy storage capacity of the thermal store, which may in turn increase how long the heat energy can be stored above a given temperature, and / or may increase a size of system that the heat energy is able to be supplied to from the thermal store.

[0022] Optionally, the chamber has a width orthogonal to the longitudinal axis of at least 5 metres. Increasing a width of the chamber may increase a volume, and thus heat energy storage capacity, of the thermal store. Optionally, the width of the self-supporting shaft is up to 10 metres, up to 25 metres, up to 30 metres, up to 50 metres, or greater than 50 metres.

[0023] Optionally, the chamber has a longitudinal dimension of at least 5 metres. Increasing a longitudinal dimension, such as a depth, of the chamber may increase a volume, and thus heat energy storage capacity, of the thermal store. Optionally, the longitudinal dimension of the self-supporting shaft is up to 10 metres, up to 20 metres, up to 30 metres, up to 50 metres, or greater than 50 metres.

[0024] Optionally, a maj ority, or all, of the chamber is located in the self-supporting shaft. This may reduce a volume of the container and / or chamber that is located above ground, which may reduce an above-ground space requirement for a given volume of the chamber. Moreover, temperature fluctuations in the ground may be lower than temperature fluctuations in air above the ground. Thus, locating a greater amount, or all, of the chamber underground may reduce temperature fluctuations in the fluid in the chamber, in use, due to transfer of energy between the fluid and the surrounds outside the thermal store. This may be particularly advantageous in locations where the air temperature regularly drops below an average temperature of the ground. In that case, locating a majority, or all, of the chamber within the self-supporting shaft may increase an amount of heat energy that is retained in the fluid in the chamber, in use, compared to a chamber that is mostly, or partly, located outside the shaft, above the ground.

[0025] Optionally, the container is not a pressure vessel. This may allow the container to be provided without additional components, such as relief valves, for controlling a pressure in the container, and / or may reduce a required strength of the container and / or structural support that is required to contain the fluid. This may provide a simpler and / or cheaper thermal store than one in which the container is a pressure vessel.

[0026] Optionally, the container is a pressure vessel. This may allow the fluid to be stored at a higher temperature, whilst remaining in liquid form. For instance, water may be stored in liquid form at a temperature above 100 degrees C. More generally, when the fluid is water comprising the heat energy, and the water would be steam if it were to be stored at a given temperature and at a pressure surrounding the container, by instead storing the water at a greater pressure for the given temperature, the temperature of the water may be increased so as to increase the amount of heat energy stored per unit volume.

[0027] Optionally, the container defines the chamber so that: an upper portion of the chamber has a first width, orthogonal to the longitudinal axis, and a lower portion of the chamber below the upper portion has a second width, orthogonal to the longitudinal axis and greater than the first width. This may provide additional capacity in the chamber for a given depth and / or above-ground footprint of the container. This may also allow a depth of the chamber to be reduced for a given volume of the chamber, which may reduce hydrostatic stresses on the lower portion of the chamber. This may, in turn, reduce a strength requirement of the container and / or self-supporting structural support in the region of the lower portion.

[0028] Optionally, the upper portion of the chamber is elongate and is oriented so that a longitudinal axis of the upper portion of the chamber is within twenty degrees of vertical. Optionally, the upper portion of the chamber is elongate and is oriented so that a longitudinal axis of the upper portion of the chamber is substantially vertical. Optionally, the lower portion of the chamber is elongate and orientated so that a longitudinal axis of the lower portion of the chamber is within twenty degrees of vertical. Optionally, the lower portion of the chamber is oriented so that the longitudinal axis of the lower portion of the chamber is substantially vertical.

[0029] Optionally, the second width is at least 10% greater than the first width, such as at least 25% greater than the first width or at least 50% greater than the first width.

[0030] Optionally, the at least one flow path comprises a first flow path that opens into the chamber in an upper region of the chamber and a second flow path that opens into the chamber in a lower region of the chamber below the upper region. This may allow fluid to be selectively provided to and / or from the upper and / or lower regions of the chamber, which may improve a versatility of the thermal store. This may be particularly advantageous when there is a temperature gradient in the fluid in the chamber, in use, with hotter fluid in the upper region and cooler fluid in the lower region. In that case, for instance, hotter fluid may be provided to the upper region and cooler fluid may be removed from the lower region, which may reduce mixing in the fluid in the two regions and allow the hotter-temperature fluid in the upper region to be stored at a higher temperature than if mixing were permitted or encouraged. Optionally, the first flow path passes through a lateral wall of the container and the second flow path passes through a lateral wall of the container.

[0031] Optionally, the thermal store comprises a third flow path that opens into the chamber in an intermediate region of the chamber below the upper region and above the lower region. This may further improve a flexibility and / or versatility of the thermal store, by allowing the fluid to be provided to and / or from the chamber in different regions of the chamber.

[0032] Optionally, the self-supporting shaft extends to ground level. In this way, there is no ground, such as back-filled ground, above the self-supporting shaft. This may allow a depth of the hole, relative to ground level, to be less than if the self-supporting shaft did not extend to ground level, for a given size of the self-supporting shaft. This may reduce a cost and / or improve an ease of manufacture of the self-supporting shaft. Alternatively, the self-supporting shaft may not extend to ground level.

[0033] Optionally, the thermal store of the first aspect of the present invention comprises any of the essential and / or optional features of the thermal store of the second aspect of the present invention and / or the third aspect of the present invention. Optionally, the thermal store of the first aspect of the present invention benefits from any of the advantages ascribed to the thermal store of the second aspect of the present invention and / or the third aspect of the present invention.

[0034] A second aspect of the present invention provides a thermal store comprising a container defining a chamber that is configured to store fluid comprising heat energy. The chamber is elongate and is oriented so that a longitudinal axis of the chamber is within twenty degrees of vertical. An upper part of the chamber is located above ground level and a lower part of the chamber is located below ground level. The thermal store comprises at least one flow path that opens into the chamber.

[0035] Optionally, the at least one flow path comprises a first flow path that opens into the chamber in an upper region of the chamber and a second flow path that opens into the chamber in a lower region of the chamber below the upper region.

[0036] Optionally, the thermal store comprises a self-supporting shaft in the ground and the container is at least partially in, such as fixed at least partially in, the self-supporting shaft. Optionally, the self-supporting shaft comprises a hole defined by the ground and a self-supporting structural support in contact with, and supporting, the ground defining the hole.

[0037] Optionally, the thermal store of the second aspect of the present invention comprises any of the essential and / or optional features of the thermal store of the first aspect of the present invention and / or the third aspect of the present invention. Optionally, the thermal store of the second aspect of the present invention benefits from any of the advantages ascribed to the thermal store of the first aspect of the present invention and / or the third aspect of the present invention.

[0038] A third aspect of the present invention provides a thermal store comprising a container defining a chamber that is configured to store fluid comprising heat energy. The container defines the chamber so that: an upper portion of the chamber has a first width, orthogonal to the longitudinal axis, and a lower portion of the chamber below the upper portion has a second width, orthogonal to the longitudinal axis and greater than the first width. At least the upper portion of the chamber is elongate and is oriented so that a longitudinal axis of the upper portion of the chamber is within twenty degrees of vertical.

[0039] Optionally, the upper portion of the chamber is oriented so that the longitudinal axis of the upper portion of the chamber is substantially vertical. Optionally, the lower portion of the chamber is elongate and orientated so that a longitudinal axis of the lower portion of the chamber is within twenty degrees of vertical. Optionally, the lower portion of the chamber is oriented so that the longitudinal axis of the lower portion of the chamber is substantially vertical. Optionally, the chamber as a whole is elongate and oriented so that a longitudinal axis of the chamber is within twenty degrees of vertical. Optionally, the chamber as a whole is oriented so that the longitudinal axis of the chamber is substantially vertical.

[0040] Optionally, the thermal store comprises at least one flow path that opens into the chamber. Optionally, the thermal store comprises a self-supporting shaft in the ground and the container is at least partially in, such as fixed at least partially in, the self-supporting shaft. Optionally, the self-supporting shaft comprises a hole defined by the ground and a self-supporting structural support in contact with, and supporting, the ground defining the hole. Optionally, an upper part of the chamber is located above ground level and a lower part of the chamber is located below ground level.

[0041] Optionally, the upper portion of the chamber has a first volume, the lower portion of the chamber has a second volume, and the first volume is different in magnitude to the second volume. Optionally, the first volume is greater than the second volume. Optionally, the first volume is less than the second volume.

[0042] Optionally, the thermal store of the third aspect of the present invention comprises any of the essential and / or optional features of the thermal store of the first aspect of the present invention and / or the thermal store of the second aspect of the present invention. Optionally, the thermal store of the third aspect of the present invention benefits from any of the advantages ascribed to the thermal store of the first aspect of the present invention and / or the second aspect of the present invention.

[0043] A fourth aspect of the present invention provides a heat storage system comprising a road traffic intersection, having an island and a roadway around the island, along which roadway road traffic is directed to flow, and a thermal store at least partially beneath the road traffic intersection. The thermal store comprises a container defining a chamber, the chamber configured to store a fluid comprising heat energy.

[0044] Optionally, the island is a roundabout. Optionally, the thermal store is at least partially beneath the island. Optionally, the thermal store is fully beneath the road traffic intersection. Optionally, the thermal store is fully beneath the island. Optionally, the thermal store is partially beneath the island and partially beneath the roadway.

[0045] Optionally, the chamber is elongate and is oriented so that a longitudinal axis of the chamber is within twenty degrees of vertical. Optionally, the longitudinal axis of the chamber is vertical.

[0046] Optionally, the longitudinal axis of the chamber is substantially aligned with a centre point of the island. Optionally, the island and the container are substantially circular and coaxially aligned.

[0047] Optionally, the heat storage system comprises at least one flow path that opens into the chamber. Optionally, the at least one flow path comprises a first flow path that opens into the chamber in an upper region of the chamber and a second flow path that opens into the chamber in a lower region of the chamber below the upper region.

[0048] Optionally, the thermal store comprises a self-supporting shaft in the ground and the container is at least partially in, such as fixed at least partially in, the self-supporting shaft. Optionally, the self-supporting shaft comprises a hole defined by the ground and a self-supporting structural support in contact with, and supporting, the ground defining the hole. Optionally, an upper part of the chamber is located above ground level and a lower part of the chamber is located below ground level.

[0049] Optionally, the container defines the chamber so that: an upper portion of the chamber has a first width, orthogonal to the longitudinal axis, and a lower portion of the chamber below the upper portion has a second width, orthogonal to the longitudinal axis and greater than the first width. Optionally, at least the upper portion of the chamber is elongate and is oriented so that a longitudinal axis of the upper portion of the chamber is within twenty degrees of vertical.

[0050] Optionally, the thermal store is according to any one of the first to third aspects of the present invention. Optionally, the thermal store of the heat storage system comprises any of the optional features of the thermal store of any of the first to third aspects of the present invention, and / or benefits from any of the advantages ascribed to the thermal store of any of the first to third aspects of the present invention.

[0051] A fifth aspect of the present invention provides a heat energy transfer system for transferring heat energy. The heat energy transfer system comprises the thermal store of any of the first to third aspects of the present invention, or the heat storage system of the fourth aspect of the present invention. The heat energy transfer system comprises a transfer system for transferring fluid between the chamber of the container of the thermal store and at least one other location.

[0052] In this way, the thermal store may provide storage of heat energy that is generated at the at least one other location, such as for convenient distribution to another location, or back to the at least one other location. The thermal store may also provide storage of heat energy that is to be distributed to the at least one other location.

[0053] Optionally, the heat energy transfer system is thermally connected to a source site to receive the heat energy from the source site. Optionally, the source site is one of a power station and a district heating network. Optionally, the at least one other location comprises a district heating network. Optionally, the at least one other location comprises the source site.

[0054] Optionally, the at least one other location comprises an interface apparatus for transferring the fluid between the heat energy transfer system and an interface arrangement of a mobile heat energy storage system. This may allow the heat energy to be transferred to other locations using the mobile heat energy storage system. Optionally, the mobile heat energy storage system is a mobile heat energy storage system of a water borne vessel, and the interface apparatus is a waterside or water borne interface apparatus. This may allow the heat energy to be transported via a waterway, such as a river, which may allow a greater amount of the heat energy to be transported than utilising a road network, where space may be more limited.

[0055] Optionally, when the thermal store comprises the first flow path and the second flow path, the transfer system comprises piping for transferring fluid between the chamber and the at least one other location, wherein the piping comprises a first line connected to the first flow path of the thermal store and a second line connected to the second flow path of the thermal store.

[0056] The thermal store of the heat energy transfer system may comprise and / or benefit from any of the optional features of, and / or advantages ascribed to, the thermal store of any of the first to third aspects of the present invention.

[0057] A sixth aspect of the present invention provides a method of manufacturing a thermal store. The method comprises providing a self-supporting shaft in the ground, wherein the self-supporting shaft comprises a hole defined by the ground and a self-supporting structural support in contact with, and supporting, the ground defining the hole. The method comprises providing, at least partially in the self-supporting shaft, a container defining a chamber that is configured to store fluid comprising heat energy, wherein the chamber is elongate and is oriented so that a longitudinal axis of the chamber is within twenty degrees of vertical. The method comprises providing at least one flow path that opens into the chamber.

[0058] By providing the self-supporting shaft in the ground, and providing the at least part of the container in the self-supporting shaft, the at least part of the container is located underground. This may reduce an amount of space taken up by the container above ground compared to a container that is entirely above ground, or may allow a larger container to be provided for the same above-ground space requirement. This may also allow a larger thermal store to be provided in a built-up environment, such as a city, than might be possible if the container were to be located entirely above-ground.

[0059] Providing the self-supporting structural support that supports the ground defining the hole may allow a size of the self-supporting shaft and container to be greater than with a shaft that does not comprise the self-supporting structural support that supports the ground defining the hole. This is because, by providing the self-supporting structural support, the container itself need not support the ground that defines the hole. This is in contrast to simply digging a hole and providing a container in the hole. In that case, the container would need to support the ground, which may limit a size of the hole and / or container that can be provided. It is to be noted that with a container comprising, e.g., an inner layer defining a chamber along with an outer skin, and / or a layer of insulation, the respective layers would form a single self-supporting unit, and would not individually be self-supporting. Thus, such an insulation layer and / or outer skin would not form a “self-supporting” structure that supports the ground - instead, it would be the entire container that supports the ground. In the present invention, the structural support is self-supporting, so that the container need not have sufficient strength to support the ground.

[0060] Providing that the chamber is elongate and oriented so that a longitudinal axis of the chamber is within twenty degrees of vertical may allow a larger chamber to be provided for a given available horizontal “footprint” above or below the ground, or may allow a footprint of the container to be reduced for a given volume of the container. In this way, a large (e.g., deep) chamber may be provided even in a location where there is limited horizontal space available above or below the ground, such as in an urban or otherwise built-up area.

[0061] Optionally, the longitudinal axis of the chamber is vertical. This may reduce a footprint of the chamber for a given volume of the chamber, or allow a larger chamber to be provided for a given available footprint.

[0062] Optionally, the providing the self-supporting shaft and the providing the container comprises: forming the self-supporting shaft in the ground; and then fixing the container at least partially in the self-supporting shaft. By first forming the self-supporting shaft in the ground, the ground may be fully supported by the self-supporting structural support of the self-supporting shaft before the container is fixed in the shaft. This may ensure that the ground is fully supported by the self-supporting shaft, and that the container need not provide structural support for the ground. Thus, the container may be of a simpler and / or more lightweight design than might otherwise be required if the container were to support the ground.

[0063] Optionally, the forming the self-supporting shaft in the ground comprises drilling and blasting the ground. For example, one or more detonation holes are drilled into the ground, explosives are placed in the holes, and controlled detonations break the ground into manageable pieces. The debris is removed, and the process is repeated to deepen the self-supporting shaft.

[0064] Optionally, the forming the self-supporting shaft in the ground comprises raise boring. For example, a small pilot hole may be drilled into the ground from ground level to the bottom of the intended self-supporting shaft. A reaming head may then be attached at the bottom and pulled back upward, creating the hole.

[0065] Optionally, the forming the self-supporting shaft in the ground comprises use of a shaft boring machine (SBM) with a rotating cutter head that bores through the ground while excavated material is transported to the surface.

[0066] Optionally, the forming the self-supporting shaft in the ground comprises manually excavating the hole, optionally with the installation of (e.g., timber or steel) supports as the hole is deepened.

[0067] Optionally, the forming the self-supporting shaft in the ground comprises an open cut method, in which a wide opening is formed in the ground to define the hole and, once a desired depth for the self-supporting shaft is reached, one or more supports or permanent structures are installed to define the hole.

[0068] Optionally, the method comprises freezing the ground using a network of pipes filled with a refrigerant, creating a temporary ice barrier to stabilize loose soils and prevent water ingress, before the forming the self-supporting shaft in the ground.

[0069] Optionally, the structural support comprises a wall, such as a (e.g., reinforced) concrete wall. The wall may be constructed in (e.g., prefabricated or sprayed) sections around a periphery of the hole. A dewatering system may be provided to remove water from the self-supporting shaft or the ground.

[0070] Optionally, the providing the self-supporting shaft comprises: sinking at least part of the self-supporting structural support at least partially into the ground; and removing material from within the at least part of the self-supporting structural support to form the self-supporting shaft. This may provide a convenient way of providing the self-supporting shaft. Moreover, by sinking the at least part of the self-supporting structural support and removing material from within the at least part of the self-supporting structural support, the ground defining the hole may be suitably supported at all times during construction of the shaft. This may reduce a likelihood of a loss of integrity of the ground during formation of the self-supporting shaft, and / or may permit the formation of a deeper self-supporting shaft than utilising other methods.

[0071] Optionally, the at least part of the self-supporting structural support comprises one or more prefabricated (e.g., concrete or steel) annular structures, such as caissons. This may permit ease of transport and / or installation of the self-supporting structural support.

[0072] Optionally, the self-supporting structural support comprises at least one (e.g., reinforced) concrete structure. Optionally, the self-supporting structural support comprises a plurality of annular structures, such as (e.g., reinforced) concrete annular structures, and the providing the self-supporting structural support comprises placing the annular structures on top of each other to form a series of stacked annular structures. This may provide flexibility in a depth of the self-supporting structural support. For instance, providing a greater number of annular rings may permit a greater depth of the self-supporting structural support, and thus the chamber, in the ground. Such annular structures may be caissons.

[0073] Optionally, the method comprises sinking a first one of the annular structures into the ground and removing material from the first one of the annular structures to form the hole and to cause the first one of the annular structures to sink into the ground. Optionally, the method comprises providing a second one of the annular structures on top of the first one of the annular structures, to form the series of stacked annular structures in the hole. Optionally, the method comprises removing material from the series of stacked annular structures to deepen the hole and cause the series of stacked annular structures to sink further into the ground. Optionally, the method comprises providing further annular structures on top of the series of stacked annular structures to increase a depth of the self-supporting shaft.

[0074] Optionally, the providing the container comprises providing a container comprising thermal insulation, for thermally insulating the chamber from the ground external to the container. The thermal insulation may reduce a rate of transfer of the heat energy from the fluid in the chamber to the ground compared to a container without such thermal insulation. This may allow the thermal store to store heat at a given temperature for a longer period, which may improve a quality of the fluid that the thermal store is able to provide to other systems.

[0075] Optionally, the providing the thermal insulation comprises applying the thermal insulation onto the self-supporting structural support, such as onto a surface of the self-supporting structural support that faces the longitudinal axis. In this way, the self-supporting structural support may also provide structural support to the thermal insulation, and / or the container as a whole.

[0076] Optionally, the providing the container comprises providing a container comprising a liner between the chamber and the thermal insulation. Optionally, the liner defines the chamber. Optionally, the thermal insulation defines the chamber. For instance, optionally, the providing the container does not comprise providing the liner.

[0077] Optionally, the chamber, the container or the self-supporting shaft has any of the optional features of the chamber, the container or the self-supporting shaft, respectively, of the thermal store of any one of the first to third aspects discussed above.

[0078] Optionally, the providing the at least one flow path comprises providing at least one flow path that passes through a lateral wall of the container. Optionally, the providing the at least one flow path comprises providing a first flow path that opens into the chamber in an upper region of the chamber and a second flow path that opens into the chamber in a lower region of the chamber below the upper region. Optionally, the providing the first flow path comprises providing a first flow path that passes through a lateral wall of the container, and the providing a second flow path comprises providing a second flow path that passes through a lateral wall of the container.

[0079] Optionally, the method comprises providing a third flow path that opens into the chamber in an intermediate region of the chamber below the upper region and above the lower region.

[0080] It will be appreciated that the thermal store may comprise any of the optional features of, and / or may benefit from any of the advantages ascribed to, the thermal store of any one of the first to third aspects of the present invention.

[0081] A seventh aspect of the present invention provides a method of transferring heat energy. The method comprises transferring fluid comprising the heat energy between at least one location and the chamber of the thermal store of any one of the first to third aspects of the present invention, or the chamber of the thermal store of the heat storage system of the fourth aspect of the present invention.

[0082] Optionally, the transferring fluid comprises transferring the fluid via the at least one flow path, where provided. Optionally, the at least one location comprises a heat energy storage system. Optionally, the heat energy storage system is a mobile heat energy storage system. Optionally, the at least one location comprises a heat energy storage system of a water borne vessel. Optionally, the at least one location comprises one of a power station and a district heating network.

[0083] Optionally, when the thermal store comprises the first flow path and the second flow path, the transferring the fluid via the at least one flow path comprises transferring the fluid via the first flow path or via the second flow path. Optionally, the transferring the fluid via the at least one flow path comprises transferring water, such as liquid water, via the at least one flow path.

[0084] Optionally, the transferring comprises transferring fluid, such as water, comprising the heat energy, at a first temperature between the location and the first flow path, and transferring fluid, such as water, at a second temperature, lower than the first temperature, between the location and the second flow path. Optionally, the transferring fluid at the first temperature and the transferring fluid at the second temperature are performed concurrently.

[0085] Optionally, the at least one location comprises a source site that is a source of the heat energy. Optionally, when the thermal store comprises the first flow path and the second flow path, the transferring comprises transferring fluid, such as water, comprising the heat energy, at a first temperature from the source site to the first flow path, and transferring fluid, such as water, at a second temperature, lower than the first temperature, from the second flow path to the source site.

[0086] Optionally, the thermal store is according to any one of the first to third aspects of the present invention. The thermal store, and thus the method, may comprise and / or benefit from any of the optional features of, and / or advantages ascribed to, any of the first to third aspects of the present invention.

[0087] Optionally, the heat energy storage system is according to the fourth aspect of the present invention. The heat energy storage system, and thus the method, may comprise and / or benefit from any of the optional features of and / or the advantages ascribed to the heat energy storage system of the fourth aspect of the present invention.

[0088] Optionally, the method is performed by the heat energy transfer system of the fifth aspect of the present invention. The method may comprise and / or benefit from any of the optional features of, and / or advantages ascribed to, the heat energy transfer system of the fifth aspect of the present invention.

[0089] It will be appreciated that optional features of any one of the above aspects of the present invention may be applied equally to any other one of the aspects of the present invention, where appropriate. Effects or advantages noted as being resultant of features or optional features of any one of the aspects of the present invention may result equally from corresponding features or optional features of any other one of the aspects of the present invention and are not reiterated in the interests of brevity. BRIEF DESCRIPTION OF THE DRAWINGS

[0090] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0091] Figure 1 shows a schematic view of an example heat energy transfer and storage system;

[0092] Figure 2 shows another schematic view of the heat energy transfer and storage system of Figure 1;

[0093] Figure 3 shows a flow diagram of an example method of transferring heat energy;

[0094] Figure 4 shows a flow diagram of an example method of manufacturing a thermal store; and

[0095] Figure 5 shows a schematic diagram of an alternative example heat energy transfer and storage system. DETAILED DESCRIPTION

[0096] Figure 1 shows an example heat energy transfer and storage system 1 comprising a power station 20, a district heating system 30, a thermal store 10, and a transfer system 40. The power station 20 comprises a generator 22 and a source store 21. The district heating system 30 comprises a heating network 32 and a destination store 31. As will be described in more detail below, the thermal store 10 comprises a shaft 100, which is located underground, and a chamber 150 in the shaft 100. The transfer system 40 comprises pipework for transferring fluid between the chamber 150 and each of the source store 21 and destination store 31, again as will be described in more detail below. The power station 20 and district heating system 30 may be referred to herein as a “source site” and a “destination site”, respectively.

[0097] Figure 2 shows a more detailed schematic view of the heat energy transfer and storage system 1. The heat energy transfer and storage system 1 comprises a road traffic intersection 50, the road traffic intersection 50 comprising an island 51 and a roadway 52 around the island 51, along which road traffic is directed to flow. The island 51 may colloquially be referred to as a “roundabout”, a “rotary” or a “traffic circle”. In other examples, the island may be any other type of island.

[0098] The thermal store 10 is partially beneath the island 51 and partially beneath the roadway 52, but fully beneath the road traffic intersection 50. More specifically, the shaft 100 is in the ground 60, and is located beneath the road traffic intersection 50. In this way, the shaft 100 is covered by the road traffic intersection 50, and an access hatch 53 is provided in the island 51 to permit access to the shaft 100. In other examples, the shaft 100 may be located in any other suitable location, which may or may not be beneath an existing urban structure. In some examples, the shaft 100 may be open to a region above the ground 60, i.e., not covered by another structure.

[0099] The shaft 100 is a self-supporting shaft that comprises a hole 101 defined by the ground 60, and a series of concrete rings 110a, 110b, 110c, 1 lOd, IlOe, 11 Of (herein referred to collectively with the reference numeral 110) arranged concentrically in a stacked arrangement in the hole 101. The thermal store 10 comprises a container 120 located in the hole 101 and fixed in the shaft 100. The container 120 comprises an inner liner 122 that forms a wall of the chamber 150, and an insulation layer 121 located between the inner liner 122 and the series of concrete rings 110. The series of concrete rings 110 forms a self-supporting structural support of the shaft 100, which is in contact with, and supports, the ground 60 defining the hole 101. The hole 101 and concrete rings 110 are circular in cross-section, and are concentric along a longitudinal axis of the shaft, herein referred to as a shaft longitudinal axis 160. In this example, the shaft longitudinal axis 160 is substantially vertical. The concrete rings each have a wall thickness of 0.95 metres, and the insulation layer has a wall thickness of 0.4 metres. The inner liner 122 has a smaller wall thickness than each of the insulation layer 121 and the concrete rings 110.

[0100] As will be described in more detail below, the thermal store 1 also comprises upper source and destination ports 141a, 142a, lower source and destination ports 141b, 142b, and intermediate source and destination ports 141c, 142c. Each of the upper, lower, and intermediate source and destination ports 141a, 141b, 141c, 142a, 142b, 142c is defined by a respective pipe that passes through a lateral wall of the container 120, more specifically through the inner liner 122, and opens into the chamber 150. The upper, lower, and intermediate source and destination ports 141a, 141b, 141c, 142a, 142b, 142c each also pass through the insulation layer 121 and the series of concrete rings 110. The transfer system 40 (not labelled in Figure 2) comprises upper, lower, and intermediate source pipes 41a, 41b, 41c that are fluidically connected between the source store 21 and, respectively, the upper, lower, and intermediate source ports 141a, 141b, 141c. The transfer system 40 also comprises upper, lower, and intermediate destination pipes 42a, 42b, 42c that are fluidically connected between the destination store 31 and, respectively, the upper, lower, and intermediate destination ports 142a, 142b, 142c. Whilst not shown in the Figures, the transfer system 40 comprises suitable flow control equipment, including pumps and valves, that are operated by signals received from a suitable flow controller, to cause water to flow through each of the upper, lower, and intermediate source and destination pipes 41a, 41b, 41c, 42a, 42b, 42c as required in use.

[0101] The shape and construction of the shaft 100, the container 120 and the chamber 150 will now be described in more detail. The concrete rings 110 define an upper shaft portion 102a of the shaft 100, and the shaft 100 comprises a lower shaft portion 102b extending downwardly away from the upper shaft portion 102a. The lower shaft portion 102b is defined by a concrete wall 111, which comprises concrete that has been sprayed onto a wall of the hole 101 defined by the ground 60 after excavating the hole 101 to form a void to accommodate the lower shaft portion 102b. The upper shaft portion 102a has an inner diameter, in a direction orthogonal to the shaft longitudinal axis 160, that is substantially constant along the shaft longitudinal axis 160, so that a space defined by the upper shaft portion 102a is substantially cylindrical. The lower shaft portion 102b has an inner diameter, orthogonal to the shaft longitudinal axis 160, that increases from a minimum diameter (which is the same as the diameter of the upper shaft portion 102a), where the lower shaft portion meets the upper shaft portion 102a, up to a maximum diameter greater than the minimum diameter in a direction downwardly along the shaft longitudinal axis 160. In this way, a space defined by the lower shaft portion 102b is substantially frustoconical. The lower shaft portion 102b has the maximum diameter at a lowermost end of the shaft 100. The upper shaft portion 102a is elongate in the vertical direction.

[0102] The insulation layer 121 of the container 120 comprises Foamglas® insulation, which is located on an inner surface of each of the concrete rings 110 and the concrete wall 111. The inner liner 122 comprises Polyethylene of Raised Temperature Resistance (PE-RT), which is provided on an inner surface of the insulation layer 121. The Foamglas® insulation of the insulation layer 121 is thermally insulating, at least in that it has a lower thermal conductivity than the material of each of the inner liner 122, the concrete rings 110 and concrete wall 111. The inner liner 122 and the insulation layer 121 in the upper shaft portion 102a and the lower shaft portion 102b each conform to a shape of the concrete rings 110 and concrete wall 111, and are concentric with the shaft longitudinal axis 160. In this way, the chamber 150 is elongate, circular in cross-section, and has a chamber longitudinal axis (not shown) that is concentric with the shaft longitudinal axis 160 and with the island 51. Moreover, the chamber 150 has an upper chamber portion 152a, which has a similar size and shape to, and is aligned with, the upper shaft portion 102a. The chamber 150 also has a lower chamber portion 152b, which has a similar size and shape to, and is aligned with, the lower shaft portion 102b. More specifically, in this example, the upper chamber portion 152a has a constant diameter along its length of 5 metres. The lower chamber portion 152b has a minimum diameter of 5 metres, where the lower chamber portion 152b meets the upper chamber portion 152a, and increases in diameter downwardly away from the upper chamber portion 152a up to a maximum diameter of 10 metres. In this way, the upper chamber portion 152a is cylindrical, and the lower chamber portion 152b is frustoconical. An overall depth D of the chamber 150 (and the shaft 100) along the shaft longitudinal axis 160 is 20 metres. Specifically, the upper chamber portion 152a has a depth of 15 metres and the lower chamber portion 152b has a depth of 5 metres. The upper chamber portion 152a thereby has a volume of around 300 cubic metres, the lower chamber portion 152b has a volume of around 230 cubic metres, and the chamber 150 has an overall volume of around 530 cubic metres. It will be appreciated that, in other examples, the upper and lower chamber portions 152a, 152b may have any other suitable dimensions. For instance, the lower chamber portion 152b may have a greater depth and / or volume than the upper chamber portion 152b. Moreover, in various examples, the lower chamber portion 152b may have any suitable cross-sectional shape in a plane aligned with the shaft longitudinal axis 160, such as trapezoidal, rectangular, bulb-shaped, or bell-shaped.

[0103] The upper source and destination ports 141a, 142a each open into the chamber 150 in an upper region 150a of the chamber 150, which here is an upper-most third of the upper chamber portion 152a of the chamber 150. The lower source and destination ports 141b, 142b each open into the chamber 150 in a lower region 150 of the chamber 150, which here is a lower-most third of the upper chamber portion 152a of the chamber 150. The intermediate source and destination ports 141c, 142c each open into an intermediate region 150c of the chamber, which extends between the upper and lower regions 150a, 150b. It will be appreciated that, whilst the upper, intermediate, and lower regions 150a, 150b, 150c of the chamber 150 are each located in the upper chamber portion 152a of the chamber, in other examples any of the upper, intermediate, and lower regions 150a, 150b, 150c, may be located in other locations in the chamber 150. For instance, the lower region 150 may be located in the lower chamber portion 152b of the chamber 150.

[0104] The source store 21 contains water comprising heat energy that is received from the generator 22, and the destination store 31 contains water comprising the heat energy that is to be supplied to the heating network 32. As will be described in more detail below with respect to the method 200 shown in Figure 3, water is transferred via the transfer system 40 between the source store 21 and the thermal store 10 so that heat energy in the source store 21 is transferred to, and stored in, the thermal store 10. Water is also transferred, via the transfer system 40, between the thermal store 10 and the destination store 31, so that heat energy in the thermal store 10 is transferred to, and stored in, the destination store 31. In this way, the thermal store 10 can provide long-term storage of heat energy generated by the generator 22, which can later be utilised by the heating network 32. It will be appreciated that transferring water via the transfer system 40 is by the flow controller of the transfer system 40 sending signals to the various pumps and / or valves of the transfer system 40 to cause operation of the various pumps and / or valves in any suitable way, as will be evident to a skilled person.

[0105] Water is stored at different temperatures in the thermal store 10. In particular, “hotter” water at a higher temperature (such as above 80 degrees Celsius) is located towards the top of the thermal store 10, such as in the upper region 150a of the chamber 150, and “cooler” water at a lower temperature (such as below 60 degrees Celsius) is located towards the bottom of the thermal store 10, such as in and below the lower region 150 of the chamber 150. A thermocline (not shown) having a high temperature gradient is typically formed in the chamber 150, the thermocline separating the hotter and cooler water in the chamber 150.

[0106] Operation of the heat energy storage and transfer system 40 is now described with reference to Figure 3, which shows a method 200 of transferring heat energy. The method 200 comprises transferring 210 water comprising the heat energy, at a temperature of 90 degrees Celsius, from the source store 21 to the upper region 150a of the chamber 150 of the thermal store 10 via the upper source pipe 41a and the upper source port 141a. The method 200 also comprises transferring 220 water at a temperature of 50 degrees Celsius from the lower region 150 of the chamber 150 to the source store 21 via the lower source port 141b and lower source pipe 41b. In this way, hotter water is supplied to the upper region 150a of the chamber 150 and cooler water in the lower region 150 of the chamber 150 is circulated back to the source store 21 for subsequent heating. This reduces mixing of hotter and cooler water in different vertical regions of the chamber 150, so that the hotter water is stored at a higher temperature in the upper region 150a.

[0107] The method 200 also comprises transferring 230 water comprising the heat energy at a temperature of 90 degrees from the upper region 150a of the chamber 150 to the destination store 31 via the upper destination port 142a and the upper destination pipe 42a. The method 200 also comprises transferring 240 water at a temperature of 50 degrees Celsius from the destination store 31 to the lower region 150 of the chamber 150 via the lower destination pipe 42b and the lower destination port 142b.

[0108] The method 200 also comprises transferring 250 heat energy from the generator 22 to the water in the source store 21, such as to the cooler water that is transferred from the thermal store 10 to the source store 21. This allows re-heating of the cooler water, which can then be passed as hotter water back to the thermal store. Similarly, the method 200 also comprises transferring 260 the heat energy from the water in the destination store 31 to the district heating network 32.

[0109] It will be appreciated that, whilst the transferring 210, 220, 230, 240, 250, 260 actions described above are shown in sequence in Figure 3, in various examples, any of the transferring 210, 220, 230, 240, 250, 260 actions described above may be performed concurrently or in any suitable sequence with any of the other transferring 210, 220, 230, 240, 250, 260 actions. Though not shown here, the method 200 may, in various examples, comprise transferring water between one or both of the source and / or destination store 21,31 and the intermediate region 150c of the chamber via, respectively, the intermediate source and / or destination pipe 41c, 42c and, respectively, the intermediate source and / or destination port 141c, 142c. This may be alternative to, or in addition to, transferring water to and / or from the upper and lower regions 150a, 150b of the chamber 150. For instance, the method may comprise transferring water from the intermediate region 150c of the chamber 150 via the intermediate source and / or destination port 141c, 142c when a water level in the chamber 150 is below the respective upper source and / or destination port 141a, 142a and above the respective intermediate upper source and / or destination port 141c, 142c. In other examples, the method may comprise, instead of, or in addition to, transferring 220 water at 50 degrees Celsius from the lower region 150 of the chamber 150 to the source store 21, transferring water at 75 degrees Celsius from the intermediate region 150c of the chamber 150 to the source store 21. This may increase an overall amount of lower-temperature water that is transferred to the power station 20 for reheating by the generator 22, which may in turn increase an average temperature of water in the chamber 150. .

[0110] Turning now to Figure 4, shown and described is a method 300 of manufacturing the thermal store 10. The method 300 comprises, at a general level, providing 310 the shaft 100 in the ground 60, providing 320 the container 120 in the shaft 100, and providing 330 the upper, lower, and intermediate source and destination ports 141a, 141b, 141c, 142a, 142b, 142c opening into the chamber 150.

[0111] The providing 310 the shaft 100 in the ground 60 and the providing 320 the container 120 comprises forming 311 the shaft 100 in the ground, and fixing 321 the container 120 in the shaft 100. The forming 311 the shaft in the ground comprises sinking 312 a first concrete ring 110a of the series of concrete rings 110 at least partially into the ground 60, and removing 313 material from within the first concrete ring 110a to form the hole 101 and to sink the first concrete ring 110a further into the ground 60. The method 300 also comprises sequentially providing further concrete rings 110b, 110c, 1 lOd, 1 lOe, 11 Of of the series of concrete rings 110 on top of the first and subsequent concrete rings 110a, 110b, 110c, HOd, IlOe, 11 Of as the first and subsequent concrete rings 110a, 110b, 110c, 1 lOd, 1 lOe, 1 lOf are sunk further into the hole 101, to form the series of concrete rings 110. More specifically, as the first concrete ring 110a is sunk further into the ground, the method 300 comprises stacking a second concrete ring 110b of the series of concrete rings 110 on top of the first concrete ring. The method 300 then comprises repeatedly removing material from within the first concrete ring 110a, so that the first concrete ring 110a, the second concrete ring 110b, and any subsequent concrete rings 110c, 1 lOd, 1 lOe, 1 lOf provided on top of the first concrete ring 110a, are sunk further into the ground. As the first, second, and subsequent concrete rings 110a, 110b, 110c, 1 lOd, 1 lOe, 1 lOf are sunk into the ground, a further one of the concrete rings 110 is stacked on top of the most-recently placed one of the concrete rings 110 to form the shaft 100.

[0112] The fixing 321 the container 120 in the shaft 100 comprises applying 322 the insulation layer 121 onto the series of concrete rings 110. In various examples, this is by spraying the thermal insulation material of the insulation layer onto the series of concrete rings 110. In other examples, this is by lining the series of concrete rings 110 with the insulation material. The fixing 321 the container in the shaft 100 also comprises providing 323 the inner liner 122 onto the insulation layer 121, so that the inner liner 122 ends up between the chamber 150 and the insulation layer 121. Again, this may be by spraying, or otherwise lining, the insulation layer 121 with the material forming the inner liner 122. In some examples, the insulation layer 121 is not provided, and the method 300 comprises providing the inner liner 122 directly onto the series of concrete rings 110.

[0113] In various examples, the providing 330 each of the upper, lower and intermediate source and destination ports 141a, 141b, 141c, 142a, 142b, 142c is by cutting, drilling, or boring a respective pipe hole through the inner liner 122, insulation layer 121, and concrete rings 110, and placing a pipe into the respective pipe hole. Similar drilling, cutting, or boring may be performed in the ground 60 to provide the upper, lower and intermediate source and destination pipes 41a, 41b, 41c, 42a, 42b, 42c of the transfer system 40.

[0114] It will be appreciated that other methods of forming 311 the shaft 100, fixing 321 the container 120 in the shaft 100, and providing 330 the upper, lower, and intermediate source and destination ports 141a, 141b, 141c, 142a, 142b, 142c are possible, for instance as described in the “Summary” section above.

[0115] Figure 5 shows an alternative heat energy transfer and storage system 401. The alternative heat energy transfer and storage system 401 is the same as that of the heat energy transfer and storage system 1 described above, with some exceptions as will be described below. Like components of the heat energy transfer and storage system 1 described above and the alternative heat energy transfer and storage system 401 are given like reference numerals, incremented by 400. Moreover, many features of the alternative heat energy transfer and storage system 401, which are the same as those features of the heat energy transfer and storage system 1 described above, are omitted from the view in Figure 5, for clarity.

[0116] In contrast to the heat energy transfer and storage system 1 described above, the shaft 500 and the chamber 550 of the alternative heat energy transfer and storage system 401 comprise neither the lower shaft portion 102b nor the lower chamber portion, which increase in diameter with depth. Moreover, the road traffic junction 50 is not provided, and an upper part 522 of the container 520 is here located external to, and above, the shaft 500, and also above the ground 60. Specifically, here, the container 520 is a unitary structure, such as an insulated tank, that is lowered and fixed into the shaft 500 after construction of the shaft 500. The container 520 also comprises a cover 590, which covers the chamber 550 and is removable to permit access to the chamber 550.

[0117] In some examples, the alternative heat energy transfer and storage system 401 comprises a road junction corresponding to the road traffic junction 50 described above. In some such examples, the upper part 522 of the container 520 is provided in or on an island of the road junction corresponding to the island 51 described above. In some examples, the shaft 500 and chamber 550 of the alternative heat energy transfer and storage system 401 comprise, respectively, a lower shaft portion and a lower chamber portion, corresponding, respectively, to the lower shaft portion 102b and the lower chamber portion 152b described above. It will be appreciated that any other features of the heat energy transfer and storage system 1 may be applied to the alternative heat energy transfer and storage system 401, and vice-versa, as appropriate to specific implementations.

[0118] Variations and modifications to the above disclosures, within the scope of the appended claims, will be evident to the skilled person. Moreover, it will be appreciated that features from one example may readily be combined with features from one or more other examples.

[0119] For instance, with respect to Figure 1, in some examples, the shaft 100 may not extend all the way up to the surface of the ground 60. For instance, the shaft 100 may extend upwardly from the depth D to a location below the surface of the ground 60, and may be covered by some of the ground 60. Moreover, one or both of the shaft longitudinal axis 160 and the chamber longitudinal axis may be oriented slightly offset from vertical, such as within 10%, with 20%, or within 30% of vertical.

[0120] Moreover, whilst the hole 101 and concrete rings 110 are circular in cross-section, and are concentric along a shaft longitudinal axis 160, in other examples, the hole 101 and / or concrete rings 110 may take any other suitable cross-section. For instance, the hole 101 and / or concrete rings 110 may have a substantially square or substantially rectangular or substantially oval cross-section. In such cases, the shaft 100 is elongate with respect to the shaft longitudinal axis 160, and may be substantially vertical with respect to a direction of gravity.

[0121] Whilst the method 200 of transferring heat energy described above describes transferring water at specific temperatures, it will be understood that these temperatures are merely exemplary, and that water may be transferred at any other suitable temperature. For instance, water may be transferred from the source store 21 to the upper region 150a of the chamber 150 at temperature of about 90 degrees Celsius. However, heat energy may be lost to the ground 60 during transfer of the water through the transfer system 40 and / or during storage of the water in the thermal store 10, such that the water actually stored in the upper region 150a is at a lower temperature, e.g., 87 degrees Celsius. Further losses may be experienced during transfer of the water through the transfer system 40 to the destination store 31, such that the temperature of the water actually received at the destination store 31 is less than a temperature of water in the upper region 150a, such as 85 degrees Celsius.

[0122] Other variations and modifications within the scope of the appended claims will be apparent to the skilled person.

Claims

1. A thermal store comprising a self-supporting shaft in the ground and, fixed at least partially in the self-supporting shaft, a container defining a chamber that is configured to store fluid comprising heat energy,wherein the self-supporting shaft comprises a hole defined by the ground and a self-supporting structural support in contact with, and supporting, the ground defining the hole;wherein the chamber is elongate and is oriented so that a longitudinal axis of the chamber is within twenty degrees of vertical, andwherein the thermal store comprises at least one flow path that opens into the chamber.

2. The thermal store of claim 1, wherein the container comprises thermal insulation, for thermally insulating the chamber from the ground external to the self-supporting shaft.

3. The thermal store of claim 2, wherein the container comprises a liner between the chamber and the thermal insulation.

4. The thermal store of any one of claims 1 to 3, wherein the chamber has a volume of more than 100 cubic metres.

5. The thermal store of any one of claims 1 to 4, wherein the chamber has a width orthogonal to the longitudinal axis of at least 5 metres.

6. The thermal store of any one of claims 1 to 5, wherein the chamber has a longitudinal dimension of at least 5 metres.

7. The thermal store of any one of claims 1 to 6, wherein a majority, or all, of the chamber is located in the self-supporting shaft.

8. The thermal store of any one of claims 1 to 7, wherein the container is not a pressure vessel.

9. The thermal store of any one of claims 1 to 8, wherein the container defines the chamber so that:an upper portion of the chamber has a first width, orthogonal to the longitudinal axis, anda lower portion of the chamber below the upper portion has a second width, orthogonal to the longitudinal axis and greater than the first width.

10. The thermal store of any one of claims 1 to 9, wherein the at least one flow path comprises a first flow path that opens into the chamber in an upper region of the chamber and a second flow path that opens into the chamber in a lower region of the chamber below the upper region.

11. A thermal store comprising a container defining a chamber that is configured to store fluid comprising heat energy,wherein the chamber is elongate and is oriented so that a longitudinal axis of the chamber is within twenty degrees of vertical,wherein an upper part of the chamber is located above ground level and a lower part of the chamber is located below ground level; andwherein the thermal store comprises at least one flow path that opens into the chamber.

12. A thermal store comprising a container defining a chamber that is configured to store fluid comprising heat energy, wherein the container defines the chamber so that:an upper portion of the chamber has a first width, orthogonal to the longitudinal axis, anda lower portion of the chamber below the upper portion has a second width, orthogonal to the longitudinal axis and greater than the first width;wherein at least the upper portion of the chamber is elongate and is oriented so that a longitudinal axis of the upper portion of the chamber is within twenty degrees of vertical.

13. A heat storage system comprising a road traffic intersection, having an island and a roadway around the island, along which roadway road traffic is directed to flow, and a thermal store at least partially beneath the road traffic intersection,wherein the thermal store comprises a container defining a chamber, the chamber configured to store a fluid comprising heat energy.

14. The heat storage system of claim 13, comprising at least one flow path that opens into the chamber.

15. A heat energy transfer system for transferring heat energy, the heat energy transfer system comprising:the thermal store of any one of claims 1 to 12, or the heat storage system of claim 13 or claim 14; anda transfer system for transferring fluid between the chamber of the container of the thermal store and at least one other location.

16. A method of manufacturing a thermal store, the method comprising:providing a self-supporting shaft in the ground, wherein the self-supporting shaft comprises a hole defined by the ground and a self-supporting structural support in contact with, and supporting, the ground defining the hole;providing, at least partially in the self-supporting shaft, a container defining a chamber that is configured to store fluid comprising heat energy, wherein the chamber is elongate and is oriented so that a longitudinal axis of the chamber is within twenty degrees of vertical; andproviding at least one flow path that opens into the chamber.

17. The method of claim 16, wherein the providing the self-supporting shaft and the providing the container comprises:forming the self-supporting shaft in the ground; and then fixing the container at least partially in the self-supporting shaft.

18. The method of claim 16 or claim 17, wherein the providing the self-supporting shaft comprises:sinking at least part of the self-supporting structural support at least partially into the ground; andremoving material from within the at least part of the self-supporting structural support to form the self-supporting shaft.

19. The method of any one of claims 16 to 18, wherein the providing the container comprises providing a container comprising thermal insulation, for thermally insulating the chamber from the ground external to the container.

20. A method of transferring heat energy, the method comprising:transferring fluid comprising the heat energy between at least one location and the chamber of the thermal store of any one of claims 1 to 12, or the chamber of the thermal store of the heat storage system of claim 13 or claim 14.

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