Hot Water System

Abstract

According to an aspect of the present invention, there is provided a hot water system including an electric heating device for heating water, a battery, a battery management system, a heat sink arrangement, and an insulating shell. The battery is electrically coupled to the electric heating device for powering the electric heating device. The battery management system is electrically coupled to the battery for charging the battery. The heat sink arrangement is thermally coupled to the battery and configured to store and release thermal energy. The insulating shell surrounds the battery and the heat sink arrangement.

Description

[Technical field]

[0001] The present invention relates to a hot water system comprising an electric heating device for heating water, a battery and a battery management system electrically coupled to the battery for charging the battery. The present invention further relates to a method for controlling such a hot water system and to a computer program product enabling a computer to carry out such a method. [Background technology]

[0002] Central heating boilers often use natural gas to heat water on demand when hot water is needed for domestic activities such as washing, bathing, cooking or heating. Domestic gas boilers have a thermal output of around 20-40 kW, which will generally be enough to meet the instantaneous hot water demand in an average household. To increase the supply of available hot water, it is possible to use a well-insulated tank that is heated when demand is low and is used when hot water is consumed faster than it can be heated by the boiler.

[0003] The obvious disadvantage of gas boilers is that they require a continuous supply of natural gas and therefore the necessary infrastructure must be present. Alternatively, bulky storage tanks can be used, which must be replaced and / or refilled periodically. Furthermore, burning natural gas, a fossil fuel, produces CO 2 As a result, in many countries the use of gas boilers is gradually being phased out, being replaced, for example, by heat pumps, solar panels and electric boilers that can be powered by renewable energies.

[0004] Electric boilers have the advantage that they are easy to install and connect. For example, electric boilers can be very easily connected to the mains supply, for example via a connection to a mains socket, and can also be connected in a simple way to the water supply. Electric boilers are therefore a more practical gas boiler alternative than, for example, heat pumps or solar panels. The important disadvantage of electric boilers compared to gas boilers is undoubtedly that the heating capacity of an electric boiler is generally limited by the power available from the domestic mains supply. A typical domestic electric boiler cannot deliver more than about 15 kW of heating power, compared to the 20-40 kW delivered by a standard gas boiler. The energy required to heat water is a fundamental quantity, and therefore the temperature rise, flow rate and power are fundamentally interrelated. A typical domestic electric boiler is therefore not able to generate sufficient heating power to match the capacity of a standard gas boiler, i.e. to heat water flowing at an equivalent flow rate to an equivalent temperature. Instead, hot water is provided at a lower temperature because there is insufficient heating capacity to heat all of the water, or the flow rate through the boiler is reduced to allow the slower flowing water to be heated to the desired temperature.

[0005] Other systems employ hot water tanks to achieve the desired water flow rate at the desired temperature. However, because there is no insulation to permanently keep the heated water in the tank at a constant temperature, the hot water tanks may not always be available and typically take up space that can lead to efficiency losses. Furthermore, the hot water coming from such storage tanks often cannot be delivered at the same high pressure as a water supply coming directly from the mains. Additionally, the time it takes for the tank to heat up leads to a lack of flexibility for the user.

[0006] In the German patent application published under DE 102009030999 A1, an electric water heater is disclosed in which a battery-powered heat pump heats water stored in a water tank. The water in the tank can be heated and the battery can be charged when electricity is cheaper, for example at night when a special night tariff applies, or during the day when electricity is available from solar panels. The battery is cooled by a cooling jacket filled with a cooling fluid. This cooling jacket is used to control the temperature of the battery and to ensure that the battery can be charged and discharged with optimal efficiency. A heat exchanger is provided to exchange heat between the water in the tank and the cooling fluid in the cooling jacket of the battery. This makes it possible to utilize the heat generated in the battery during charging to heat the water in the tank, which contributes to the energy efficiency of the overall water heater. The electric water heater of DE 102009030999 A1 alleviates some of the known problems with electrically heating water, but leaves many of the problems mentioned above unsolved. Most importantly, the heat pump and large water tank of this heating system result in a complex setup that takes up a lot of space.

[0007] It is an object of the present invention to address one or more of the shortcomings associated with the prior art. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] German Patent Application Publication No. 102009030999 Summary of the Invention

[0009] According to an aspect of the present invention, there is provided a hot water system including an electric heating device for heating water, a battery, a battery management system, a heat sink arrangement, and an insulating shell. The battery is electrically coupled to the electric heating device for powering the electric heating device. The battery management system is electrically coupled to the battery for charging the battery. The heat sink arrangement is thermally coupled to the battery and configured to store and release thermal energy. The insulating shell surrounds the battery and the heat sink arrangement.

[0010] In contrast to previously known electric hot water systems, the heat sink configuration according to the present invention is not limited to simply preventing overheating of the battery by extracting heat during the charging process. Whereas known battery cooling devices try to extract all excess heat as efficiently as possible, the heat sink configuration according to the present invention absorbs and retains the generated heat, storing it for later use within the same insulating shell that also surrounds the battery. Advantageously, the heat sink configuration according to the present invention allows the heat generated by the battery to be utilized to provide hot water on demand without the need for a separate water storage tank. Furthermore, the heat sink configuration reduces the fluctuations in the battery temperature, thereby reducing the risk of damaging the battery through excessive thermal cycling. The space-saving and energy-efficient characteristics of the electric hot water system described herein make it suitable to be used to replace existing heat-on-demand gas boilers or for installation in new buildings and for use in other applications where space is limited.

[0011] A battery comprises a means for storing electricity. In a preferred embodiment, a battery may comprise one or more cells. For example, a battery may comprise one or more chemical batteries.

[0012] The battery management system is electrically coupled to the battery and configured to charge the battery. Thus, the battery management system may be referred to as a charger or battery charging device in some embodiments. In some embodiments, the battery management system may be a separate modular unit disposed within the insulating shell and may be electrically coupled to the battery. In other embodiments, the battery management system may be integrated with the battery.

[0013] Preferably, the heat sink arrangement is further thermally coupled to the battery management system, and the insulating shell further surrounds the battery management system. Like a battery, the battery management system may generate heat during the charging process. This heat may also be stored in the heat sink arrangement within the insulating shell for later heating of the water.

[0014] In a preferred embodiment, the hot water system includes an alternating current (AC) for directing to a current (DC) power supply for a battery management system. The AC-DC power supply is configured to be electrically coupled to a source of AC power, such as a wall outlet AC power source. The AC-DC power supply may be part of the battery management system in some embodiments, or alternatively, the AC-DC power supply may be a separate component configured to provide power to the battery management system. In any embodiment, the AC-DC power supply is configured to receive AC power, such as a utility power source, and convert the AC power to DC power for charging the battery. For example, the utility power source may provide the battery for charging via the battery management system and / or the AC-DC power supply. Thus, the AC-DC power supply is electrically coupled directly or indirectly to the battery. The AC-DC power supply may be configured to convert the AC power to DC power having a higher voltage than the RMS of the AC power, for example, using a power factor correction (PFC) based power supply. Even more preferably, the AC-DC power supply may be configured to convert the AC power to DC power having a higher voltage than the fully charged voltage of the cells in the battery.

[0015] The AC-DC power supply for the battery management system is preferably thermally coupled to the heat sink arrangement. Most preferably, the AC-DC power supply for the battery management system is located within the insulating shell, e.g., the insulating shell surrounds the AC-DC power supply for the battery management system. Thus, when charging the battery, the thermal energy generated by the AC-DC power supply can be stored by the heat sink arrangement within the insulating shell. Power electronics for other electrical devices within the insulating shell, e.g., pumps and / or fans, can also be located within the insulating shell and, when in use, can also generate heat that can be stored in the heat sink arrangement within the insulating shell.

[0016] In a preferred embodiment, the heat sink configuration has a thermal capacity that is sufficient to store all the heat generated by charging the battery without causing damage to the battery due to excessive thermal cycling. For example, heat may be generated by the battery management system, the AC-DC power supply for the battery management system, the battery itself, and other electrical components within the insulating shell during charging of the battery, and this heat can be stored by the heat sink configuration. Preferably, the thermal capacity of the heat sink configuration is greater than the total amount of heat generated by charging the battery. For example, the thermal capacity of the heat sink configuration is preferably greater than all the heat generated by the electrical components, e.g., the battery management system, the AC-DC power supply for the battery management system, and the battery, when charging the battery.

[0017] The optimal maximum temperature of the battery and the amount of heat generated during charging are known or measurable quantities. Thus, the thermal capacity requirement of the heat sink configuration can be calculated. Also, the thermal capacity of the materials in the heat sink configuration are known or measurable quantities. Thus, the thermal requirement of the heat sink configuration can be calculated, and the heat sink configuration can be configured to ensure that the heat sink has a large and sufficient maximum thermal storage capacity to avoid causing damage to the battery due to excessive thermal cycling.

[0018] Note that heat is also generated while the battery is being discharged. However, the discharge of the battery occurs during a period of demand for hot water. When there is a demand for hot water, the electric heating device utilizes the electrical energy stored in the battery to heat the water. Any heat already stored in the heat sink arrangement, and any heat generated within the battery itself during discharge, can be used to preheat the water flowing to the electric heating device.

[0019] The heat sink arrangement can include a heat exchanger configured to facilitate heat exchange between an interior of the insulating shell and water flowing to an inlet of the electric heating device, such that the temperature within the insulating shell can be controlled by removing heat from the interior of the insulating shell via the heat exchanger.

[0020] The heat sink configuration preferably comprises a heat sink volume for holding a heat exchange fluid. The heat sink volume can be configured for holding a heat exchange fluid that is either liquid or gas. In other words, the system can comprise a heat exchange fluid in the heat sink volume, which can be liquid or gas. The heat exchange fluid can facilitate a particularly efficient removal of heat from the interior of the insulating shell. Furthermore, the heat exchange fluid can facilitate flexibility in the way in which heat is removed from the interior of the insulating shell.

[0021] How the pre-heating of the water is accomplished depends on whether the heat sink volume is an "open system" or a "closed system."

[0022] In an open system, the heat sink volume can be fluidly coupled to the inlet of the electric heating device. This allows the water to be heated to fill the heat sink volume, which increases the thermal capacity of the heat sink arrangement. This also allows the water to be routed through the heat sink arrangement before being routed to the electric heating device. Thus, the water can be preheated before being routed to the electric heating device for further heating. In a closed system, the water supplied to the electric heating device and the heat sink volume are not fluidly coupled. Instead, the heat sink arrangement can include a heat exchanger for exchanging heat between a heat exchange fluid in the heat sink volume and the water flowing into the inlet of the electric heating device. In this way, the water heated by the electric heating device is further preheated by the heat exchanger. In a closed system, the heat exchange fluid can be water, air, or any other suitable fluid (e.g., liquid or gas).

[0023] A pump can be included in either an open or closed system to facilitate circulation of fluid within the heat sink volume to ensure uniform distribution of thermal energy during charging and discharging of the battery. For example, in an open system, a pump can be utilized to facilitate circulation of water through the heat sink volume. In a closed system, a pump can be provided to facilitate circulation of a heat exchange fluid through the heat sink volume and to further facilitate removal of heat from the heat sink volume through a heat exchanger. It will be appreciated that in embodiments where the heat exchange fluid is a gas, the circulation pump can be, for example, a fan.

[0024] Preferably, the hot water system further comprises a controller operably coupled to the battery management system and / or the electric heating device, the controller being able to control the charging process of the battery, for example to ensure that charging costs are kept low, or for example to ensure that the battery is fully charged when a high demand for hot water is expected.

[0025] A temperature sensor may be provided for measuring the temperature inside the insulating shell.

[0026] In some embodiments, the controller can be operably coupled to a device configured to initiate a flow within the heat sink volume. Such a device can be a pump (or a fan in embodiments where the heat exchange fluid is a gas) or, for example, a release valve fluidly coupled to the heat sink volume. The controller is preferably operably coupled to a temperature sensor and a device, and can be configured to selectively initiate a flow within the heat sink volume to reject heat from the heat sink volume depending on the temperature inside the insulating shell. The initiated flow can be, for example, a heat exchange fluid exiting the heat sink volume, or a circulation of a heat exchange fluid within the heat sink volume to facilitate heat exchange between the heat exchange fluid and water flowing into the inlet of the electric heating device. In either embodiment, the flow within the heat sink volume ultimately rejects heat from the heat sink volume.

[0027] The system may further include a release valve fluidly coupled to the heat sink volume and configured to facilitate release of the heat exchange fluid from the heat sink volume. A controller operably coupled to the temperature sensor and the release valve is configured to open the release valve dependent on a temperature inside the insulating shell.

[0028] In some embodiments, a dump valve fluidly coupled to the heat sink volume may also be fluidly coupled to an inlet of an electric heating device and configured to allow drainage of water from the heat sink volume to the inlet of the electric heating device, where if there is no direct demand for hot water and the temperature inside the insulating shell rises above the optimal maximum temperature of the battery, heat may be dumped by dumping pre-heated water, for example, to a drain or to a fluid-based heating system, such as a water-based heating system.

[0029] In some embodiments, a fluid-based heating system, e.g., a central heating system, can act as an additional heat sink. For example, even if there is no water actively flowing through the central heating system, heat from the battery can also be conducted to the water in the central heating system if the water in the central heating system is in fluid communication with the heat sink volume in the insulating shell and is thus thermally coupled to the heat sink volume. Thus, opening the release valve to facilitate fluid communication between the central heating system and the heat sink volume can increase the thermal capacity available to store heat radiated by the battery and other electrical components in the shell.

[0030] In some examples, the controller can be operably coupled to a temperature sensor and a pump configured to circulate a heat exchange fluid within the heat sink volume. As such, the controller can be configured to operate the pump dependent on a temperature within the insulating shell. For example, if the temperature within the insulating shell rises above a set threshold, the controller can operate the pump to circulate the heat exchange fluid within the heat sink volume to facilitate heat exchange from the fluid through a heat exchanger in a closed system to water to be heated.

[0031] In some embodiments, the controller can be operably coupled to the temperature sensor, the pump, and the dump valve, and the controller can operate both the pump and the dump valve to move the heat exchange fluid, in either liquid or gaseous state, from the heat sink volume to reject heat from the heat sink volume.

[0032] In some embodiments, the cooling loop of the heat pump may be configured within the insulated shell or may be thermally coupled to the interior of the insulated shell, so that heat radiating from the battery and other components within the shell can be rejected to the cooling loop of the heat pump.

[0033] In some embodiments, the hot water system may further include a second heating device. The second heating device is preferably configured to be powered by a utility power source. Thus, the second heating device may be referred to as a second electric heating device. Optionally, the second heating device may include a heat pump configuration.

[0034] In some implementations, the hot water system can be configured such that the water heated by the second heating device is preheated by heat from the interior of the insulating shell, so that in an open system, the heat sink volume can be fluidly coupled to the inlet of the second heating device, and in a closed system, a heat exchanger can be configured to exchange heat between a heat exchange fluid in the heat sink volume and the water flowing into the inlet of the second heating device.

[0035] In embodiments including an electric heating device and a second heating device, depending on the circumstances, either the (first) electric heating device, the second heating device, or both may be used. When two heating devices are connected in series, the choice of which heating device to use may depend, for example, on the desired temperature increase or the relative cost of operating one or the other. In some embodiments, the first electric heating device and the second heating device may be provided on a parallel fluid flow path. When the (first) electric heating device and the second heating device are provided on a parallel fluid flow path, using both simultaneously will allow for a higher throughput, i.e., a higher hot water flow rate and therefore a higher water pressure at the outlet for a given flow rate. Thus, the choice of which of the two to utilize may also depend on the demand for hot water.

[0036] A controllable valve arrangement can be provided for controlling the fluid flow rate in each of the parallel fluid flow paths. For example, the controllable valve arrangement can comprise a first valve controlling the fluid flow rate in the fluid flow path comprising the (first) electric heating device and a second valve controlling the fluid flow rate in the second fluid flow path comprising the second heating device. Preferably, the first valve can be located downstream of the heat sink volume. This ensures that the heat sink volume remains filled with water even with the first valve closed to stop the first fluid flow path. As previously mentioned, the water in the heat sink volume increases the heat capacity in the insulating shell. In some embodiments, the first valve can operate as the aforementioned release valve, configured to be operated to control the temperature in the insulating shell. Preferably, the second valve can be located downstream of the second heating device.

[0037] Providing the (first) electric heating device and the second heating device on separate parallel fluid flow paths advantageously minimizes the resistance effect experienced by the water being heated. For example, the first and second heating devices provide resistance to the water flow. By arranging the heating devices on parallel fluid flow paths, the resistance provided by a given heating device is only experienced when the heating device is in use, i.e., when water is flowing through the fluid flow path. Such an arrangement provides an advantage over systems with heating devices arranged in series, where the water flows through and is resisted by multiple heating devices, even when such heating devices are not actively heating the water.

[0038] Optionally, the heat sink construction includes a phase change material, which is well suited for storing large amounts of thermal energy in a relatively small volume and can do so while limiting temperature fluctuations within the insulating shell. For example, the heat sink construction can include a sodium sulfate or paraffin-based phase change material.

[0039] In an exemplary embodiment, the battery includes a plurality of modules, i.e., battery modules, each housing one or more individual cells. The modules are preferably formed from a material having high thermal conductivity, e.g., aluminum, to efficiently transfer thermal energy from the cells to the remainder of the heat sink configuration. The heat sink configuration can include a frame having a plurality of compartments or fixtures, each configured to hold one or more of the battery modules, all of which increase the thermal capacity of the heat sink as a whole within the insulating shell.

[0040] The heat sink volume can include heat exchange flow paths passing between each battery module. In some embodiments, the heat exchange flow paths can pass through each battery module. With such a modular structure, the size and thermal capacity of the system can be easily adapted to the needs and circumstances. The modular structure further allows for easy replacement of individual modules in case of technical failure, and makes the flow paths of the heat sink volume more practical to pass through the battery structure and to create a large surface area available for heat transfer.

[0041] In some embodiments, one or more heat exchange flow paths can be defined by conduits within the frame. For example, such conduits can be formed as an integral part of the frame. The frame can thus perform multiple functions including holding the battery modules, directing heat exchange fluid around the battery modules, and conducting heat between the battery modules and the heat exchange fluid, all of which themselves increase the overall thermal capacity of the heat sink arrangement within the insulating shell. The frame can also include one or more compartments configured to hold a phase change material. In some embodiments, individual modules can include one or more compartments configured to hold a phase change material.

[0042] Containing the battery in an insulating shell increases the thermal capacity within the insulating shell, so that the structure of the battery itself increases the thermal capacity to help store heat not accepted by the cells during charging, even when no heat exchange fluid is flowing within the heat sink volume. In such a case, in contrast to the prior art examples, the cells are not necessarily actively cooled. Instead, the heat sink configuration within the insulating shell is configured with sufficient thermal capacity to ensure that the cells do not overheat or become damaged by excessive thermal cycling as a result of the predictable amount of thermal energy radiated during charging. Including a frame within the insulating shell further increases the thermal capacity within the insulating shell.

[0043] Providing a heat sink arrangement within the insulating shell that is thermally coupled to the battery helps to reduce fluctuations in battery temperature. Reducing temperature fluctuations extends the life of the cells. In a preferred embodiment, the temperature within the insulating shell can be maintained between 0°C and 85°C, more preferably between 20°C and 40°C. To provide active control of the temperature within the insulating shell, the controller can operate the discharge valve and / or the circulation pump and / or control charging of the battery, as described above.

[0044] The battery modules, i.e., cells, can be actively cooled by circulating or flowing a heat exchange fluid through the heat sink volume. Such transfer of heat exchange fluid can be accomplished using pumps in open or closed systems, as previously described. In some examples, the battery modules can be actively cooled by flowing water, heated, for example, by an electric heating device, through the heat sink volume in an open system. For example, heat can be released from the interior of the insulating shell, so that the battery modules can be actively cooled when hot water is required, for example, by opening a tap or other outlet downstream of the heat sink volume.

[0045] The hot water system may further include a battery heating device enclosed within the insulating shell. The battery heating device may be used to ensure that the battery temperature remains within an optimal range for high energy efficiency and low battery wear. In some embodiments, the system may include a return conduit configured to pipe heated water from downstream of the first and / or second heating devices back to a heat sink volume within the insulating shell to heat the battery. The return conduit may include a controllable valve such that the temperature within the insulating shell, and therefore the temperature of the battery, may be actively managed by opening and closing the valve.

[0046] In some embodiments, the hot water system may comprise an external casing. In a preferred embodiment, an insulating shell surrounding the battery and heat sink arrangement may be housed within the external casing. Additionally, the battery management system may be housed within the same external casing. In a further preferred embodiment, the external casing may further house the heat exchanger as mentioned above. Most preferably, the external casing may additionally house at least one of an electric heating device and a second heating device. If desired, a controllable valve arrangement may also be housed within the external casing.

[0047] According to another aspect of the invention, a control means is provided for controlling the hot water system described above. For example, the control means may be used to control the fluid flow rate in each available parallel fluid flow path depending on at least one of the following: a current demand for heated water, a state of charge of the battery, a temperature inside the insulating shell, and a current price of the utility power. Another control means may control the charging of the battery depending on at least one of the following: a state of charge of the battery, a temperature inside the insulating shell, a predicted cost of charging the battery, a current price of the utility power, and a predicted demand for heated water. [Brief description of the drawings]

[0048] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: [Figure 1] 1 illustrates a schematic diagram of a hot water system according to an embodiment of the present invention. [Diagram 2] 1 shows a schematic of a battery for a hot water system surrounded by an insulating shell. [Diagram 3] FIG. 1 shows a schematic diagram of the inlet and outlet of the heat sink volume of a hot water system with an open heat transfer configuration. [Figure 4] 1 shows a schematic diagram of a heat exchanger configured to transfer thermal energy between a heat sink volume and a water supply in a system having a closed-loop heat sink volume. [Diagram 5]1 shows a perspective view of a battery frame having a battery module and heat sink arrangement suitable for use in the hot water system of claim 1. [Figure 6] FIG. 6 shows an enlarged view of a portion of the battery frame of FIG. [Figure 7] 1 shows a cross-sectional view of a battery frame suitable for use in the hot water system according to claim 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0049] 1 shows a schematic diagram of a hot water system 10 according to an embodiment of the present invention. Hot water system 10 includes a water intake 12 configured to receive water from a water supply, e.g., a water mains or a water tank (not shown). System 10 also includes an electric heating device 14 for heating the water entering system 10 via water intake 12. Electrical heating device 14 may be, for example, an electrical resistance heating element. Electrical heating device 14 is electrically coupled to battery 16 such that battery 16 can provide power to electrical heating device 14.

[0050] In a preferred embodiment, the electric heating device 14 may be powered by a direct current (DC) source via the battery 16. In other embodiments, the electric heating device 14 may be an alternating current (AC) heating device 14, and the system 10 may further include a DC / AC converter (not shown) for converting the DC power from the battery 16 therethrough into AC power for powering the heating device 14.

[0051] 1 , the hot water system 10 further includes a battery management system 18 electrically coupled to the battery 16 to enable charging of the battery 16, i.e., the battery management system 18 is configured to charge the battery 16. The battery management system 18 is preferably connected to a utility power source 20 to accept power for charging the battery 16. Although not shown in the figures, in some embodiments the hot water system 10 may also include an AC / DC power source for the battery management system 18, where the management system is configured to accept AC power from the utility power supply 20 and convert it to DC power for charging the battery 16.

[0052] As shown generally in FIG. 1, the system 10 also includes a controller 22 operably coupled to the battery management system 18 to control the charging of the battery 16. For example, the controller 22 may control the charging of the battery 16 depending on at least one of the state of charge of the battery 16, the projected cost of the battery 16, the current price of utility power, and the projected demand for heated water. Thus, the controller 22 may control the timing of the charging of the battery 16. In some embodiments, the controller 22 is configured to accept user input to directly command the charging of the battery 16. In some embodiments, the controller 22 is also coupled to the heating device 14 to control the operation of the heating device 14 when in use.

[0053] In some embodiments, the electric heating device 14 may be electrically coupled to the utility power source 20 such that the utility power source 20 may power the heating device 14 in addition to the power provided by the battery 16. In such embodiments, the system 10 may further include an AC / DC converter (not shown), e.g., a rectifier that rectifies the AC utility power source 20 and provides DC power to the heating device 14. Thus, although not shown in the accompanying drawings, in some embodiments, the system 10 may include a heating device 14 that is powered by both the battery 16 and the utility power source 20. In such embodiments, the heating device 14 may be powered primarily by the battery 16, with supplemental power provided by the utility power source 20. Alternatively, the heating device 14 may be powered primarily by the utility power source 20, and the battery 16 may provide supplemental power to achieve a heating capacity equivalent to that of a conventional gas boiler.

[0054] In particular, the hot water system 10 includes a heat sink arrangement 24 that is specifically configured to store heat radiated from the battery 16 and other electrical components, thus helping to regulate the temperature of the battery 16. Accordingly, the heat sink arrangement 24 is thermally coupled to the battery 16 to facilitate the transfer of thermal energy from the battery 16 to the heat sink arrangement 24. In a preferred embodiment, the heat sink arrangement 24 is also thermally coupled to the battery management system 18 to accept heat from the battery management system 18. Similarly, in embodiments in which the hot water system 10 includes an AC / DC power source for the battery management system 18, such AC / DC power source is preferably thermally coupled to the heat sink arrangement 24 such that the heat sink arrangement 24 can accept and store thermal energy radiated by the AC / DC power source during charging of the battery 16.

[0055] The heat sink arrangement 24 is described in more detail below with reference to Figures 5, 6 and especially the cross-sectional view of Figure 7. In initial overview, however, the heat sink arrangement 24 is configured with a thermal capacity that is sufficient to store all of the heat generated by charging the battery 16 without causing damage to the battery 16 due to excessive thermal cycling.

[0056] 2 in addition to FIG 1, the battery 16 and heat sink arrangement 24 of the hot water system 10 are enclosed in an insulating shell 26. In a preferred embodiment, the insulating shell 26 also encloses the battery management system 18, as shown in FIG 2. In embodiments that include an AC / DC power source for the battery management system 18, such power source is also preferably enclosed within the insulating shell 26. The insulating shell 26 ensures that heat generated by the battery 16 and other electrical components within the shell, and transferred to the heat sink arrangement 24, is retained within the heat sink arrangement 24, i.e., is not wasted or is quickly rejected.

[0057] Thus, as described in more detail below, the hot water system 10 advantageously facilitates the efficient use of heat generated by the battery 16 to improve the overall efficiency and lifespan of the hot water system 10. Specifically, retaining the heat generated by the battery 16 allows for pre-heating of the water before the pre-heated water is sent to the electric heating device 14, as shown diagrammatically in FIG. 1. Retaining the heat may also help maintain the temperature of the battery 16 within an optimal operating range. Maximizing the capacity of the insulating shell 26, i.e., increasing the thermal resistance of the shell 26, improves the efficiency of the hot water system 10 by minimizing heat loss as a result of charging and discharging the battery 16. Thus, in some embodiments, the insulating shell 26 is configured to retain within the heat sink arrangement 24 within the shell 26, 70%, preferably at least 80%, or more preferably at least 90% of the thermal energy generated by charging and discharging the battery 16. For example, the thermal performance of the shell 26 may be comparable to that of an insulated hot water tank.

[0058] In a preferred embodiment, the hot water system 10 further includes a second heating device 28, as shown in the schematic diagram of Figure 1. The second heating device 28 is preferably configured to be powered by the utility power source 20 and may include, for example, an electrical resistance heating element. The inclusion of the second heating device 28 facilitates an increase in the total heating power output such that the heating power of the electric hot water system 10 may be comparable to that of a typical gas-powered boiler when both heating devices 14, 28, powered by the battery 16 and the utility power source 20, respectively, are used to heat water.

[0059] As shown in FIG. 1, in a particularly preferred embodiment, the electric heating device 14 and the second heating device 28 are disposed on parallel fluid flow paths 30a, 30b. For example, the electric heating device 14 can be disposed on the first fluid flow path 30a, and the second heating device 28 can be disposed on the second fluid flow path 30b. The hot water system 10 can include a controllable valve arrangement 32 for controlling the fluid flow rate in each of the parallel fluid flow paths 30a, 30b. For example, the system 10 can include a first controllable valve 34a disposed on the first fluid flow path 30a and a second controllable valve 34b disposed on the second fluid flow path 30b.

[0060] The controller 22 is preferably operably coupled to a controllable valve arrangement 32. By opening and closing the first and second controllable valves 34a, 34b, the proportion of water from the water intake 12 that flows through each heating device 14, 28 can be controlled. The fluid flow rate in each of the parallel fluid flow paths 30a, 30b can be controlled depending on at least one of the current demand for heated water, the state of charge of the battery 16, the temperature inside the insulating shell 26, and the current price of the utility power 20.

[0061] 1 and 2, but as most clearly illustrated in FIG. 7, the heat sink configuration 24 preferably includes a heat sink volume 36 for holding a heat exchange fluid 38. Heat generated by the battery 16 and the battery management system 18 is transferred to the heat exchange fluid 38 in the heat sink volume 36. Providing the heat exchange fluid 38 in the heat sink volume 36 increases the thermal capacity within the insulating shell 26. Thus, thermal energy radiated from the battery 16, the battery management system 18, and other electrical components within the shell can be stored in the heat exchange fluid 38 within the insulating shell 26. The heat exchange fluid 38 helps to enable control of the temperature within the insulating shell 26 and facilitates multiple options for removing heat from the interior of the insulating shell 26, as described in more detail below.

[0062] With further reference to FIG. 3 with reference to FIG. 1, in some embodiments, the hot water system 10 can be configured as an open system. In an open system configuration, the heat sink volume 36 is fluidly coupled to the inlet 40 of the electric heating device 14. In other words, the heat sink volume 36 is in fluid communication with the inlet 40 of the electric heating device 14 such that fluid 38 from the heat sink volume 36 is delivered to the electric heating device 14 for subsequent additional heating. Thus, preferably, in an open system, the heat exchange fluid 38 in the heat sink volume 36 can be water introduced into the hot water system 10 via the mains water intake 12.

[0063] In an open system, water flows from the water intake 12 through the heat sink volume 36 and then to the electric heating device 14, for example, via the first fluid flow path 30a. In such a configuration, the water is preheated by heat radiated from the battery 16, battery management system 18, and other electrical components contained within the insulating shell 26 before being further heated by the electric heating device 14. Such a configuration results in an energy-efficient hot water system 10, since excess heat is transferred from the battery 16, battery management system 18, and other electrical components, such as the AC / DC power source, directly to the water to be heated. Thus, energy input to the hot water system 10 is utilized, directly or indirectly, to heat the water and is not wasted as a result.

[0064] The inlet 42 and outlet 44 of the heat sink volume 36 in an open system are shown diagrammatically in Figure 3. In this embodiment, all of the water conveyed from the first fluid flow path 30a first flows through the heat sink volume 36 before reaching the electric heating device 14. However, in some other embodiments, the system 10 may be configured such that a portion of the water entering the first fluid flow path 30a is diverted to flow through the heat sink volume 36, while the remaining water in the first fluid flow path 30a bypasses the heat sink volume 36 and is sent directly to the electric heating device 14.

[0065] In some embodiments, the hot water system 10 may include a discharge valve (not shown) fluidly coupled to the heat sink volume 36. In some embodiments, the discharge valve may be configured to allow for the discharge of a heat exchange fluid 38, such as water, from the heat sink volume 36. For example, the water may be discharged into the first fluid flow path 30a. Although not shown in FIG. 3, a temperature sensor configured to measure a temperature inside the insulating shell 26 may also be included. The controller 22 is preferably operably coupled to the temperature sensor and the discharge valve such that the discharge valve may be actuated depending on the temperature inside the insulating shell 26. In some embodiments, the first controllable valve 34a described above may perform the same function as the discharge valve, i.e., the first controllable valve 34a may open or close depending on the temperature inside the insulating shell 26. The valve 34a may be actuated independently of the electric heating device 14, i.e., the valve 34a may be actuated regardless of whether the electric heating device 14 is actuated to heat the water. Thus, in some embodiments, the temperature inside the insulating shell 26 can be controlled by allowing or preventing the flow of water through the heat sink volume 36 by opening or closing the controllable valve 34a to allow or prevent the rejection of heat from the heat sink volume 36.

[0066] The closed system is configured such that heat is removed from the interior of the insulating shell 26 via the heat exchanger 48. FIG. 4 shows an example of a portion of a closed system at the boundary of the heat sink volume 36 and the fluid flow path 30a. This configuration can be described as a closed system because the heat sink volume 36 is not in fluid communication with the first or second fluid flow paths 30a, 30b. The heat exchanger 48 facilitates the transfer of thermal energy from the interior of the insulating shell 26 to the water flowing to the inlet 40 of the electric heating device 14. To this end, the heat exchanger 48 is preferably located upstream of the electric heating device 14. Thus, the water sent to the electric heating device 14 can be preheated by the heat exchanger 48 using heat from within the insulating shell 26.

[0067] In a closed system, a separate heat exchange fluid 38 is circulated within the heat sink volume 36 to receive the thermal energy radiated by the battery 16. The heat exchange fluid 38 is preferably configured to transfer heat from the heat exchange fluid 38 to water flowing to the inlet 40 of the electric heating device 14. In some embodiments, the heat exchange fluid 38 in the heat sink volume 36 of the closed system may be water. However, since in such a system the heat exchange fluid 38 is not fluidly coupled to the outlet through which the heated water is sent to the consumer, the closed system also facilitates the use of other heat exchange fluids 38. As such, the heat exchange fluid 38 does not need to be safe for human consumption and may include beneficial additives, such as, for example, anti-corrosion additives.

[0068] The heat sink volume 36 may be a complex configuration with multiple heat exchange fluid paths 50 (e.g., as shown in Figures 6 and 7). Therefore, it may be advantageous to configure the heat sink volume 36 as a closed system that allows for closed control of the fluid 38 within the heat sink volume 36. For example, mains water may contain different natural minerals that may leave deposits, such as limescale, on the surfaces over which such water flows over time. A closed system heat sink volume 36 means that certain chemical agents may be introduced into the heat sink volume 36 to ensure that the heat exchange fluid paths 50 are not damaged, restricted, or blocked by such deposits. And, in some embodiments, the water that flows over and around the battery 16 and other materials within the insulating shell 26 may not be suitable or safe for human consumption, and therefore forming the heat sink volume 36 as a closed system avoids any possible contamination of the water supplied to consumers at the outlet.

[0069] The closed system may include a pump (not shown) for circulating the heat exchange fluid 38 through the heat sink volume 36. The closed system may also include a temperature sensor (not shown) inside the insulating shell 26. The controller 22 may be operatively coupled to the temperature sensor and the pump, and the controller 22 may operate the circulation pump depending on the temperature inside the insulating shell 26 to facilitate rejecting heat from the heat exchange fluid 38 through the heat exchanger 48 and into the incoming cold water flow in the fluid flow paths 30a, 30b.

[0070] In other embodiments, the closed system may further include a release valve (not shown). The release valve may be fluidly coupled to the heat sink volume 36. The controller 22 may be operatively coupled to such a release valve such that the release valve may be actuated depending on the temperature inside the insulating shell 26. For example, the gaseous heat exchange fluid 38, such as air, in the heat sink volume 36 may be released directly to the environment outside the insulating shell 26 to manage the temperature inside the insulating shell 26. Alternatively, the liquid heat exchange fluid 38 may be released from the heat sink volume 36 through the release valve, for example into a drain, to control the temperature inside the insulating shell 26.

[0071] In some embodiments of a closed system, the dump valve may be fluidly coupled to a fluid-based heating system, such as a water-based central heating system, such that heat can be dumped from the heat sink volume 36 to the heating system fluid via operation of the dump valve. This dumping of heat does not necessarily require a heating system in which heat exchange fluid 38 actively flows through the heat sink volume 36, but may be facilitated simply by fluidly and thermally coupling the heat sink volume 36 to the heating system by opening the dump valve. Providing fluid communication between the heat sink volume 36 and the water-based heating system may increase the thermal capacity available to store heat radiated by the battery 16.

[0072] Although not shown in the accompanying drawings, in some embodiments, the system 10 may include a battery heating device enclosed within the insulating shell 26. The battery heating device may be operably coupled to the controller 22 such that the controller 22 may activate the battery heating device, when necessary, to increase the temperature within the insulating shell 26 to ensure that the temperature of the battery 16 remains within an optimal operating range.

[0073] The battery 16 disposed within the insulating shell 26 and other components of the hot water system 10 will now be described in more detail with reference to the remaining figures. The following description is equally applicable to the open and closed systems previously described. For ease of reference, the fluid 38 within the heat sink volume 36 will be referred to as the heat exchange fluid 38 since heat is transferred, i.e., exchanged, from the battery 16 to the heat exchange fluid 38. It will be appreciated that in an open system, the heat exchange fluid 38 is water that is heated using the heating device 14, and in a closed system, the heat exchange fluid 38 is a separate fluid to the water that is heated using the heating device 14.

[0074] 5, 6 and 7, the battery 16 preferably comprises multiple battery modules 52. For example, the battery modules 52 may each include one or more battery cells 54, e.g., chemical battery cells 54. The battery modules 52 may be electrically connected to each other in series to provide a high current to the electric heating device 14. Alternatively, the battery modules 52 may be electrically connected to each other in parallel to provide a high voltage output to the electric heating device 14. In some other embodiments, the electrical connections between the battery modules 52 may be selectively reconfigurable to facilitate active control of the current and voltage provided to the electric heating device 14.

[0075] The heat sink arrangement 24 includes a frame 56 having a number of compartments or fixtures arranged to hold one or more of the battery modules 52. It will be appreciated that, being part of the battery structure, the frame 56 is also housed within the insulating shell 26 (e.g., as shown in FIG. 2). Thus, the frame 56 provides additional thermal capacity for storing thermal energy radiated by the battery 16 and other electrical components within the shell 26. In some embodiments, and as most clearly illustrated in FIG. 7, the heat sink arrangement 24 within the insulating shell 26 can include a phase change material 60, and the phase change material 60 can be housed by the frame 56.

[0076] 7, the heat sink volume 36 includes heat exchange fluid flow paths 50 passing between or through each battery module 52. This configuration provides the heat sink volume 36 with a high surface area through which heat can be transferred to the heat exchange fluid 38. For reference, the heat exchange fluid flow paths 50 of the heat sink volume 36 are also illustrated in the embodiments of FIGS. 5 and 6.

[0077] Next, the advantages of the electric hot water system 10 of the present invention will be described by way of numerical examples. However, it should be noted that the numerical values ​​described in the examples are merely given as examples and are not intended to limit the scope of the present invention as defined in the appended claims.

[0078] For purposes of demonstration, the following examples assume a charging efficiency of 90% and a battery capacity of 10 kWh. To charge the battery 16, the battery 16, i.e., the cells 54 and the battery management system 18 together, rejects (10 / 0.9)-10=1.11 kWh of thermal energy. This is thermal energy that would be wasted unless it was stored.

[0079] In this example, each cell 54 has a mass of 0.65 kg, a nominal voltage of 3.2 V, a capacity of 30 Ah, and provides an energy storage of 96 Wh. The individual heat capacity of such cells 54 will depend on the exact construction of the cell, but will typically be in the range of 0.8 to 1.7 kJ / kgK. For this example, each cell 54 has a specific heat capacity of 1 kJ / kgK.

[0080] A battery 16 with a capacity of 10 kWh can be formed with 104 given cells 54 (10 kWh / 96 Wh=~104 cells). Thus, the thermal capacity of the cells 54 in this battery 16 in this embodiment is 104 x 1 kJ / kgK x 0.65 kg = 67.6 kJ / K. Therefore, 67.6 kJ of thermal energy is required to heat all the cells 54 at 1 K (=1°C). 1.11 kWh of thermal energy is radiated by the battery 16 and the battery management system 18, which is about 4 MJ, and 4 MJ / 67.6 kJ results in a temperature rise of 59°C.

[0081] While battery temperature rise can technically be within the inherent range of the cells 54, thermal cycling within this range over many years can degrade the health and / or capacity of the battery. Therefore, as previously mentioned, the hot water system 10 of the present invention further includes a heat sink arrangement 24 within the insulating shell 26 to increase the thermal capacity within the insulating shell 26. The heat sink arrangement 24 within the insulating shell 26 includes a frame 56 that houses or mounts the battery module 52 to hold the module in place. For this embodiment, the frame 56 can be formed of cast aluminum.

[0082] A numerical example will now be described to demonstrate the thermal capabilities of the heat sink configuration 24 within the insulating shell 26. For the purposes of the example, a frame 56 is configured to hold twelve of the previously described cells 54 (see, e.g., FIG. 6). It should be appreciated that any calculation can be performed with any number of cells, so long as the respective numbers are observed, allowing direct comparison of temperature changes.

[0083] Continuing with the example shown in FIG. 6, the twelve cells 54 have a combined heat capacity of 12×1 kJ / kgK×0.65 kg=7.8 kJ / K. The twelve cells 54 used in this example have a storage capacity of 12×96 Wh=1.152 kWh. The thermal energy radiated during charging at 90% efficiency is (1.152 / 0.9)−1.512=0.128 kWh, which is 460.8 kJ. Thus, without utilizing a heat sink 24 in the shell 26, the temperature rise experienced by the cells as a result of heat radiated during charging would be 460.8 kJ / 7.8 kJ / K=59° C. in this example.

[0084] However, as previously mentioned, providing the heat sink arrangement 24 within the insulating shell advantageously reduces the temperature fluctuations experienced by the cells 54 of the battery 16. The frame 56 inside the insulating shell 26 is part of the heat sink 24 in this example. For the purposes of this example, the frame 56 may be assumed to have a mass of 2.5 kg, and the specific heat capacity of aluminum is 0.96 kJ / kgK. Thus, the heat capacity of the frame 56 may be calculated as 2.5 kg x 0.96 kJ / kgK = 2.4 kJ / K. Thus, in this example, the total heat capacity of the frame 56 and the cells 54 within the insulating shell 26 is 7.8 kJ / K + 2.4 kJ / K = 10.2 kJ / K.

[0085] As mentioned above, the twelve cells 54 in this example have a storage capacity of 1.152 kWh, and the heat energy radiated during charging at 90% efficiency is 460.8 kJ. Therefore, the total temperature rise within the insulating shell 26 as a result of charging can be calculated as 460.8 kJ / 10.2 kJ / K=45° C. Thus, providing the heat sink arrangement 24 including the frame 56 reduces the temperature rise experienced by the cells 54 within the insulating shell 26 during charging.

[0086] The heat capacity within the shell 26 is further increased by including a heat exchange fluid 38 within the heat sink volume 36 within the insulating shell 26. For this example, the heat exchange fluid 38 is water. The heat sink volume 36, including the heat exchange fluid flow passages 50, has a volume of 0.466 liters in this example. The heat exchange fluid 38 (water) within the heat sink volume 36 therefore has a mass of 0.466 kg and a specific heat capacity of 4.2 kJ / kgK. The heat exchange fluid 38 within the heat sink volume 36 therefore provides an additional heat capacity of 1.957 kJ / K (from 4.2 kJ / kgK x 0.466 kg = 1.957 kJ / K).

[0087] Therefore, the total heat capacity within the insulating shell 26, including the cells 54, the frame 56 and the heat exchange fluid 38, is 7.8 kJ / K+2.4 kJ / K+1.96 kJ / K=12.16 kJ / K. The total heat radiated during charging at 90% efficiency is 460.8 kJ. The total temperature rise experienced by the cells 54 within the insulating shell 26 is therefore 460.8 kJ / 12.16 kJ / K=37.9° C. temperature rise. Clearly, the heat exchange fluid 38 within the heat sink volume 36 further reduces the temperature rise.

[0088] As mentioned above, in some embodiments, the hot water system 10 may further include a phase change material 60, for example, sodium sulfate, within the insulating shell 26. For this embodiment, the phase change material 60 is sodium sulfate, which has a melting point of 32.4° C. and a heat of fusion of 252 kJ / kg. Thus, 252 kJ of energy is required to melt 1 kg of sodium sulfate, which will occur at 32.4° C.

[0089] In a preferred embodiment, the hot water system 10 is configured such that the melting point of the phase change material 60 is within the range of temperatures experienced inside the insulating shell 26 when charging and discharging the battery 16. Thus, the change in temperature will cease for the time it takes to melt (or freeze) a given volume of the phase change material 60.

[0090] Referring again to this embodiment, three of the nine heat exchange fluid flow paths 50 in the frame 56 shown by way of example in FIG. 6 may be filled with sodium sulfate 60. That is, the sodium sulfate, a phase change material 60, may be contained within the heat sink arrangement 24 within the compartment formed by the frame 56.

[0091] The energy required to melt this volume of phase change material 60 can be subtracted from the energy available to raise the temperature (or added to the energy not accepted during cooling). Here, in this example, the heat exchange fluid flow passage 50 filled with the heat exchange fluid 38 has a volume of 0.311 liters, so the system 10 contains water in the heat sink volume 36 having a mass of 0.311 kg. Because the specific heat capacity of water is 4.2 kJ / kgK, the heat capacity added by containing the heat exchange fluid 38 in the insulating shell 26 is 4.2 x 0.311 = 1.306 kJ / K. Thus, in this example with the reduced amount of heat exchange fluid 38, the total heat capacity in the insulating shell 26 is 7.8 kJ / K + 2.4 kJ / K + 1.31 kJ / K = 11.51 kJ / K.

[0092] However, the mass of sodium sulfate 60 contained in the three channels is 0.414 kg, and the energy required to dissolve this mass of sodium sulfate is 0.414 kg x 252 kJ / kg = 93 kJ. The heat radiated during charging with 90% efficiency is 460.8 kJ. Removing the heat absorbed by dissolving the phase change material 60 leaves 460.8 kJ - 93 kJ = 367.8 kJ. The total temperature increase experienced by the cells 54 in the system 10 including the phase change material 60 in the insulating shell 26 in this example is 367.8 kJ / 11.51 kJ / K = 32.0 ° C. The above calculation does not take into account the specific heat capacity of solid and liquid sodium sulfate, and in reality, the temperature increase is actually not that drastic. In summary, therefore, the inclusion of phase change material 60 within shell 26 further reduces the temperature rise experienced by cells 54 which, as previously discussed, extends the life of those cells.

[0093] The present invention, as described herein and defined in the appended claims, advantageously stores heat radiated by the battery 16 during charging and utilizes it to enable more efficient water heating and extend battery life. Increasing the efficiency of a system typically results in increased material and manufacturing costs. However, the hot water system 10 of the present invention facilitates increasing system efficiency without increasing costs. For example, because the radiated heat is recaptured in the heat sink arrangement 24 for later use, less efficient cells 54 with higher internal resistances that produce greater heat output can be used. The use of such cells 54 may support cost advantages. Similarly, because the radiated heat energy is captured and stored for later use, the electronics in the battery management system 18 can be purposefully designed to be less than optimal and therefore cheaper.

[0094] It will be appreciated that any feature described in connection with the various embodiments above may be readily combined with any other feature described in connection with the different embodiments without departing from the scope of the present invention as defined in the appended claims. It will further be appreciated that the above description and accompanying drawings are given by way of example only. Thus, many substitutions can be made to the specific embodiments described above without departing from the scope of the present invention as defined in the appended claims.

Claims

1. an electric heating device for heating water; a battery electrically coupled to the electric heating device for powering the electric heating device; a battery management system electrically coupled to the battery for charging the battery; a heat sink arrangement thermally coupled to the battery and configured to store and release thermal energy; an insulating shell surrounding the battery and the heat sink arrangement.

2. 10. The hot water system of claim 1, wherein the heat sink configuration has a thermal capacity sufficient to store all of the heat generated by charging the battery without causing damage to the battery due to excessive thermal cycling.

3. The hot water system of claim 1 , wherein the heat sink arrangement is thermally coupled to the battery management system, and the insulating shell further surrounds the battery management system.

4. The hot water system of claim 1 , wherein the heat sink arrangement comprises a heat exchanger configured to facilitate heat exchange between an interior of the insulating shell and water entering an inlet of the electric heating device.

5. The hot water system of claim 1 , wherein the heat sink arrangement comprises a heat sink volume for holding a heat exchange fluid.

6. The hot water system of claim 5 , wherein the heat sink volume is fluidly coupled to an inlet of the electric heating device.

7. The hot water system of claim 5 , wherein the heat sink arrangement comprises a heat exchanger for exchanging heat between a heat exchange fluid in the heat sink volume and water entering an inlet of the electric heating device.

8. The hot water system of claim 7 further comprising a pump for circulating the heat exchange fluid through the heat sink volume.

9. The hot water system of claim 5 , further comprising a controller operably coupled to the battery management system and / or the electric heating device.

10. The hot water system of claim 9 , further comprising a temperature sensor for measuring a temperature inside the insulating shell.

11. 11. The hot water system of claim 10, wherein the control unit is operably coupled to a device configured to initiate flow within the heat sink volume, the control unit being operably coupled to the temperature sensor and the device and configured to initiate flow within the heat sink volume to reject heat from the heat sink volume depending on the temperature inside the insulating shell.

12. 11. The hot water system of claim 10, further comprising: a release valve fluidly coupled to the heat sink volume and configured to facilitate release of heat exchange fluid from the heat sink volume; and the controller is operably coupled to the temperature sensor and the release valve and configured to open the release valve depending on the temperature inside the insulating shell.

13. 13. The hot water system of claim 12, wherein the release valve is further fluidly coupled to an inlet of the electric heating device and configured to allow drainage of water from the heat sink volume to the inlet of the electric heating device.

14. 11. The hot water system of claim 10, further comprising a pump for circulating the heat exchange fluid through the heat sink volume, the control unit being operably coupled to the temperature sensor and the pump and configured to operate the pump dependent on the temperature inside the insulating shell.

15. The hot water system of claim 1 , further comprising a second heating device.

16. The hot water system of claim 15 , wherein the second heating device is configured to be powered by a utility power source.

17. The hot water system according to claim 15, wherein the electric heating device and the second heating device are provided on parallel fluid flow paths.

18. 18. The hot water system of claim 17, further comprising a controllable valve arrangement for controlling fluid flow rate in each of the parallel fluid flow paths.

19. The hot water system of claim 1 , wherein the heat sink arrangement comprises a phase change material.

20. 2. The hot water system of claim 1, wherein the battery comprises a plurality of battery modules, each capable of housing one or more individual cells, and the heat sink arrangement comprises a frame having a plurality of compartments or fixtures, each compartment or fixture configured to hold one or more of the battery modules.

21. 21. The hot water system of claim 20, wherein the heat sink configuration comprises a heat sink volume for holding a heat exchange fluid, the heat sink volume comprising a heat exchange fluid flow path passing between and / or through each battery module.

22. 21. The hot water system of claim 20, wherein the heat sink configuration comprises a heat sink volume for holding a heat exchange fluid, the heat sink volume comprising a heat exchange fluid flow path, and one or more heat exchange fluid flow paths are defined by conduits within the frame.

23. The hot water system of claim 1 further comprising a battery heating device enclosed within the insulating shell.

24. 2. The hot water system of claim 1, further comprising an AC / DC power supply within the insulating shell, the AC / DC power supply electrically coupled to at least one of the battery and / or a battery management system to power the battery, and the AC / DC power supply thermally coupled to the heat sink arrangement.

25. 20. The method of controlling a hot water system of claim 18, the method including controlling fluid flow rate in each of the parallel fluid flow paths depending on at least one of a current hot water demand, a state of charge of the battery, a temperature inside the insulating shell, and a current price of utility power.

26. 25. A method of controlling a hot water system according to any one of claims 1 to 24, comprising controlling charging of the battery depending on at least one of the state of charge of the battery, the temperature inside the insulating shell, the predicted cost of charging the battery, the current price of utility power, and the predicted demand for hot water.

27. 26. A computer program product comprising computer executable instructions that, when executed by a computer, cause the computer to perform the method of claim 25.

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