ENERGY SUPPLY SYSTEM

Field of the Invention

The present invention generally relates to energy- supply systems, and in particular, but not limited to solar thermal heat storage and delivery systems.

Background

Heat pumps are commonly used for interior space heating during winter months and interior space cooling during summer months, as an air conditioner. A schematic diagram of a basic heat pump system is shown in Figure 1. The heat pump 1 comprises a compressor 3 for compressing refrigerant, for example FREON, a first heat exchange coil 5 for cooling and condensing the hot, high pressure refrigerant from the compressor 3, an expansion valve 7 for expanding and cooling the condensed refrigerant from the first heat exchanger coil 5, and a second heat exchange coil 9 for receiving refrigerant from the expansion valve 7 and enabling the refrigerant to evaporate on passage therethrough to provide cooling. Evaporator refrigerant from the second heat exchange coil is returned to the inlet of the compressor 3 and the cycle is repeated.

For space heating, air is blown across the condenser coil 5 and is heated by the hot, high pressure refrigerant from the compressor. The evaporator coil 9 receives heat from a suitable heat source, which may, for example, be outside ambient air, a water reservoir or the ground. For interior cooling, the heat pump may be operated in reverse so that the first heat exchanger coil 5 operates as an evaporator and the second heat exchanger coil 9 operates as a condenser. In this case, interior air is

blown across the first heat exchanger coil 5 and is cooled by the refrigerant, and hot, high pressure refrigerant from the compressor is passed through the second heat exchanger coil 9 and its heat is rejected to a suitable heat sink, for example outside ambient air, a water reservoir or the ground .

Figures 2A to 2G show various examples of geothermal heat pumps (GHP) , also known as ground source heat pumps (GSHP) . Figures 2A to 2C show various examples of ground coupled heat pumps (GCHP) , also known as closed loop heat pumps, which exchange heat directly with the ground. Figure 2A shows a system in which a heat exchanger 13 is arranged vertically in the ground, Figure 2B shows a system in which the heat exchanger 15 is disposed horizontally in the ground, and Figure 2C shows a coiled heat exchanger 17 embedded in the ground. Each heat exchanger loop may carry a heat transfer fluid which is separate from the heat pump refrigerant circuit, or the loop may comprise a heat exchanger of the heat pump and carry refrigerant.

Figures 2D and 2E show examples of ground water heat pumps (GWHP) , which are also known as open loop heat pumps, in which the outside heat exchange medium is water. Figure 2D shows a system comprising two wells 19, 21, in which water is pumped from one of the wells 19 to the heat pump 1 for heat exchange with one of the heat pump coils and is subsequently passed to the second well 21. Figure 2E shows a system having a single well 23 in which water is pumped from the well to the heat pump 1 for heat exchange with one of its coils and is subsequently passed to a suitable water disposal system, for example a lake, pond, river, creek, etc.

Figures 2F and 2G show examples of surface water heat pumps (SWHP) , also known as lake or pond loop heat pumps, in which the outside heat exchange medium is a body of surface water. In the system of Figure 2F, a series of heat exchange coils 25 are immersed in a body of surface water, for example a pond 27, and a heat transfer fluid is passed through the coils 25 for heat exchange with the water, is then passed to the heat pump 1 and subsequently returned to the heat exchange coils 25 in a closed cycle. In the system shown in Figure 2G, water is drawn directly from the pond 27 by means of a pump 29, passed to the heat pump 1 and returned to the pond via a return line 31.

Solar thermal collectors are also known for providing heat for buildings. In a typical system, the solar collector comprises an absorber and one or more conduits for carrying liquid which is heated by solar thermal energy and subsequently passed to a building for heating, and then returned to the solar collector. During summer months, a solar collector may produce more heat than is actually required. Some authors have proposed that solar thermal collectors be connected to borehole tubes or vertical heating tubes buried 50 to 200 feet below the ground as a possible way to store thermal energy from the solar thermal panels. However, detailed studies of the seasonal variation of ground water flow volumes and patterns are required to ensure the solar heat is not carried away with slowly flowing ground water.

Summary of the Invention

According to one aspect of the present invention, there is provided a thermal energy supply system, comprising a thermal storage container for containing a mass for

storing thermal energy, the container including a thermal insulating structure or material for thermally insulating the internal volume of the container, thermal energy supply means for supplying thermal energy to said mass, and energy supply means for drawing thermal energy from said mass and providing said thermal energy to a thermal energy receiver.

Advantageously, this arrangement enables thermal energy to be stored over a period of time determined by the thermal insulating properties of the insulating structure or material so that thermal energy provided to the thermal storage container at one point in time is available for use at a later point in time.

In some embodiments, the thermal insulating structure or material in combination with the thermal storage mass may enable thermal energy to be stored over periods of weeks or months so that thermal energy supplied during summer months, for example, is available for use during off summer months.

In some embodiments, the thermal insulating structure or material at least partially surrounds an external wall of the container. Advantageously, in this arrangement, the external wall of the container can also be used to store thermal energy.

In some embodiments, the container has an external structure, for example a wall or other structure which is substantially impervious to liquid, for example water, or a water-based liquid such as brine, or other liquid.

In some embodiments, the container may be positioned underground, for example, below and/or adjacent a building.

In some embodiments, the container may include a combination of solid material and liquid serving as the thermal storage mass. In some embodiments, the solid material may provide a support for structure above the container. In some embodiments, the solid material may comprise granite or other rock or any other granular material. In some embodiments, the solid material may include concrete or other solid material and which may be formed or shaped into a support structure, for example a pillar or beam.

In some embodiments, the thermal energy storage medium comprises a combination of different media, each media having a different specific heat and density, and wherein the relative amount of each medium in the thermal storage medium is selected to increase the amount of energy that can be stored per unit volume above that that can be provided by a single one of the different medium.

In some embodiments, the container may provide the base for a building, a parking lot, a park or other structure requiring stable ground to build upon.

In some embodiments, the container may prevent liquid migration through the container walls or base and/or inhibit heat convection and conduction from the thermal mass .

Some embodiments include a second container for storing thermal energy. The second container may have a smaller volume than the first container. In some embodiments, the second container may be in thermal contact or communication with the first container. The second container may be at least partially or fully immersed or

disposed in the first container. The second container may ^¬ be adapted to contain a liquid, such as water.

Some embodiments include one or more solar collectors for supplying solar thermal energy to at least one of the first and second containers. Some embodiments include a heat pump or heat exchanger for transferring heat between the first container and another entity such as a building and/or process and/or water supply. The heat pump or heat exchanger may be operated to transfer heat from the building to the first storage container and/or operated to transfer heat from the first storage container to the entity and/or to the second storage container.

In some embodiments, the solar collector may include a reflector and an absorber, wherein the absorber receives reflected solar radiation and includes one or more conduits for transferring solar thermal energy into a fluid, e.g. liquid or gaseous fluid. In some embodiments, the fluid may be supplied from the solar collector to the first and/or second thermal energy storage tanks and/or vice versa.

According to another aspect of the present invention, there is provided a controller for controlling the transfer of heat between the first container and another entity. In some embodiments, the controller may control the transfer of solar energy to the system, for example, the other entity and/or the first and/or second container. In some embodiments, the controller is adapted to transfer thermal energy from a solar collector to the second storage container or tank, and once the second storage tank has reached a predetermined temperature, the controller is

adapted to transfer thermal energy from the solar collector to the first storage container.

In some embodiments, the controller may be adapted to control the transfer of energy from the second storage tank to another entity. In some embodiments, the controller is adapted to control the transfer of thermal energy between the first and second storage containers. In some embodiments, the controller is adapted to control the transfer of heat from a solar collector to another entity.

In some embodiments, the controller is adapted to control a heat pump or other device to transfer heat from another entity into the first and/or second container, and in one embodiment may use the thermal storage mass in the first container as a heat sink to cool the other entity, for example a building or process.

According to another aspect of the present invention, there is provided an energy supply system comprising: a solar collector for receiving solar radiation and transferring received solar thermal energy to a fluid; a first container containing a first thermal storage medium; heat transfer means for transferring heat between the fluid and the first thermal storage medium; a second storage container containing a second thermal storage medium; heat transfer means for transferring heat between the fluid and said second thermal storage medium; a heat exchanger for exchanging heat between the second thermal storage medium and another entity; and a controller for controlling the transfer of heat between the first thermal storage medium and the fluid and between the second thermal storage medium and the fluid.

In some embodiments, the controller is operative to control the transfer of heat between the fluid and the second storage medium in response to the temperature of the second storage medium.

In some embodiments, the controller is operative to cause heat from the fluid to be transferred preferentially to the second storage medium if the second storage medium is below a predetermined temperature, and to cause heat from the fluid to be transferred preferentially to the first storage medium if the temperature of the second storage medium is at or above the predetermined temperature.

In some embodiments, the controller is operative to cease transfer of heat between the fluid and the first storage medium in response to the temperature of the first thermal storage medium.

In some embodiments, the energy supply system further comprises an exposure controller for varying the exposure of the solar collector to solar radiation.

In some embodiments, the controller is operative to reduce exposure of the solar collector in response to the temperature of at least one of the first and second storage medium.

In some embodiments, the energy supply system further comprises heat transfer means for transferring heat between the fluid and an entity.

In some embodiments, the controller is operative to control heat transfer between the fluid and the entity.

In some embodiments, the controller is operative to cause heat to be transferred to the entity based on one

or more criterion, for example, when heat is demanded by the entity.

In some embodiments, the controller is operative to cause heat from the fluid to be transferred to the entity when the entity requires heat and to cause residual heat from the fluid, if any, to be transferred to one or more of the first and second storage medium. In some embodiments, the controller causes heat to be transferred to the second storage medium in preference to the first storage medium.

In some embodiments, the energy supply system further comprises heat transfer means for transferring heat between the second storage medium and the entity.

In some embodiments, the controller is operative to control transfer of heat from the second storage medium to the entity.

In some embodiments, the controller is operative to cause heat to be transferred from the second storage medium to the entity based on a determination that insufficient solar thermal heat is available to the fluid.

In some embodiments, the energy supply system further comprises heat transfer means for transferring heat from the first thermal storage medium to the second thermal storage medium.

In some embodiments, the controller is operative to control heat transfer from the first thermal storage medium to the second thermal storage medium.

In some embodiments, the heat transfer means for transferring heat from the first thermal storage medium to the second thermal storage medium comprises a heat pump.

In some embodiments, the controller is responsive to one or more predetermined criteria to cause the heat pump to transfer heat from the first thermal storage medium to the second thermal storage medium. The predetermined criteria may comprise at least one of (1) that the temperature of the second storage medium is below a predetermined value, (2) that the cost of electricity is below a predetermined value, and (3) the predicted amount of solar energy available during a predetermined future period of time is below a predetermined value.

In some embodiments, the controller is operative to control the amount of heat transferred by the heat pump from the first thermal storage medium to the second thermal storage medium based on a predicted amount of solar energy available over a predetermined future period of time.

In some embodiments, the energy supply system further comprises a heat source other than the solar collector and the first thermal storage medium for transferring heat to the second thermal storage medium, and wherein the controller is operative to control the transfer of heat from the heat source to the second thermal storage medium based on one or more predetermined criterion. The predetermined criteria may include any one or more of (1) that the temperature of the first thermal storage medium is below a predetermined value and (2) that the predicted amount of solar energy available over a predetermined future period of time is below a predetermined value.

In some embodiments, the energy supply system further comprises heat transfer means for transferring heat between the first thermal storage medium and the entity.

In some embodiments, the controller may be adapted to control the transfer of heat between the first thermal storage medium and the entity.

In some embodiments, the controller is adapted to cause heat to be transferred from the entity to the first thermal storage medium based on one or more predetermined criteria. The predetermined criterion may for example be that the entity requires cooling and/or that the entity is at or above a predetermined temperature .

In some embodiments, the heat transfer means for transferring heat between the first thermal storage medium and the entity comprises a heat pump.

In some embodiments, the controller is adapted to cause the heat pump to transfer heat from the entity to at least one of the first and second thermal storage medium in response to a requirement to remove heat from the entity.

Embodiments of the invention may be used in conjunction with any form of solar collector, examples of which are disclosed in the applicant's co-pending U.S. provisional application filed on 28 ^th March, 2006, and the applicant's PCT application, entitled "Solar Collector" filed on 28 ^th March, 2007, attorney docket number 51159-14, and which are both incorporated herein by reference in their entirety.

Brief Description of the Drawings

Examples of embodiments of the present invention will now be described with reference to the drawings, in which:

Figure 1 shows an example of a compressor based heat pump system;

Figures 2A to 2C show schematic diagrams of ground coupled heat pump systems;

Figures 2D and 2E show schematic diagrams of ground water heat pump systems;

Figures 2F and 2G show schematic diagrams of surface water heat pump systems;

Figure 3 shows an example of the variation of building energy use as a function of time;

Figure 4A shows a front view of an energy supply system according to an embodiment of the present invention;

Figure 4B shows a front view of an energy supply system according to another embodiment of the present invention;

Figure 4C shows a block diagram of elements of an energy supply system shown in Figure 4B;

Figure 5 shows a cross-sectional view through a building and thermal storage tank according to an embodiment of the present invention;

Figure 6 shows a perspective view from below of a building having a thermal storage container according to an embodiment of the present invention;

Figure 7 shows a plan view of a building and thermal storage container according to an embodiment of the present invention;

Figure 8 shows an example of a graph showing the variation of heat storage capacity as a function of the percentage of granite content for a thermal storage system;

Figure 9 shows an example of a graph of the seasonal variation in temperature of a long-term low temperature thermal storage tank according to an embodiment of the present invention;

Figure 10 shows a graph of the coefficient of performance (COP) of a heat pump as a function of scavenging temperature;

Figure 11 shows a schematic diagram of an energy supply or cooling system according to an embodiment of the invention;

Figures 12A and B show an example of a short-term thermal energy storage tank according to an embodiment of the present invention;

Figures 13A to E show various views of an example of the short-term thermal energy storage tank of Figures 12A and 12B;

Figure 14 shows Table 1, which provides examples of values of various parameters for an energy supply system;

Figure 15 shows Table 2, which provides propertie of different thermal storage medium;

Table 1 provides values of thermal energy storage capacity for various materials;

Figure 16 shows Table 3, which provides thermal energy storage capacity values of various materials; and

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Figure 17 shows Table 4, which provides values relating to heat pump performance.

Description of Embodiments

Figure 3 shows an example of graphs of the energy use of a building over a yearly period (solid line) , solar thermal energy produced by a solar energy supply system over a yearly period (broken line) and domestic hot water energy load over a yearly period (alternate short and long broken line) . The graph shows that the energy use as a function of time is near a maximum in January, (~ 8,000 kWh) gradually decreases to a minimum of about 800 kWh between July and August and then increases again during the months of September, October, November and December toward the maximum. Production of thermal solar energy steadily increases from about 3,000 kWhs to about 3,300 kWhs between January and mid-March, then gradually decreases to about 2,000 kWhs in June, increases again in the summer months to about 3,000 kWhs, decreases to a minimum value of about 1,300 kWhs during the month of November and then slowly increases again during December.

As can be seen by comparing the two curves, more energy is consumed between January and April than the amount of solar energy produced, more solar thermal energy is produced than consumed between about mid-May and mid- September and more energy is consumed between October and December than the amount of solar thermal energy produced over the same period. Embodiments of the present invention enable solar thermal energy produced but not consumed during one part of the year, for example, between June and September, as shown, for example, by the area 41 between the two curves in Figure 3 to be stored for later use during

other parts of the year when, for example, the energy requirements exceed the amount of solar thermal energy produced, as, for example, shown by the areas 43, 45 between the two curves of Figure 3.

Referring to Figures 4A to 4C, a thermal energy supply system, generally shown at 101, for supplying thermal energy to a building 103 comprises a solar collector 105 for receiving solar radiation 107 and transferring the received solar thermal energy to a fluid 109 which may be carried through one or more conduits 111. The energy supply system includes a first container 113 containing a thermal storage medium 115 and a second container 117 containing a second thermal storage medium 119. In this embodiment, the first container is positioned below ground level 121 and includes container walls 123, 125, a base 127 and a top 129. The container walls 123, 125 and base 127 may be formed of a moisture impermeable material or lined or treated with a moisture impermeable material . A moisture impermeable material 131 may be provided for example on the inside and/or the outside of the container walls and base.

The container walls 123, 125 and the base 127 may comprise a thermal insulating material or structure, and/or a thermal insulating material may be provided adjacent the walls 123, 125 and may be provided adjacent the base 127. Thermally insulating material 135 may be positioned outside the container wall, as for example, shown in Figure 4B and/or may be provided within the container adjacent the inside surface of the walls 123, 125. Thermally insulating material 137 may be provided adjacent and below the base 127, as shown, for example, in Figure 4B, and/or within the container above the base 127. One benefit of providing thermal insulation outside the container is that the

container walls may provide part of the thermal storage medium.

In this embodiment, the container walls 123, 125 also provide foundation support for supporting the building 103.

The thermal storage medium 115 includes a liquid, for example water or brine or other liquid. The thermal storage medium may also include solid material such as rock 139, either natural or man-made, and/or other solid material or structure, such as one or more structural support pillars or walls 141. The solid material is preferably arranged to provide gaps and spaces within the solid material for the passage of liquid. To this end, the solid material may comprise discrete pieces arranged to allow liquid to flow between the individual pieces. The solid structure within the container 113 may provide support for a structure above the container, and in the present embodiment, the solid material at least partially provides support for the top 129 of the container and the floor 143 of the building. The top of the container 129 may comprise a thermally insulating material and/or a separate thermally insulating material or liner 145 may be provided at or near the top of the container to resist thermal leakage therefrom.

In this embodiment, the second container 117 is positioned within the first container 113 and includes container walls 147, 149 and a base 151. The walls and base may be formed of a thermally insulating material or structure to resist flow of heat between the first and second containers, and/or a thermally insulating material may be provided externally and/or internally of the walls

and/or base of the second container. Although in other embodiments, the second container may be positioned externally of the first container, positioning the second container within the first allows heat that may pass through the walls of the second container to be deposited in the thermal storage medium 115 of the first container 113.

The thermal storage medium of the second container may comprise a liquid, for example water, or other liquid.

The energy supply system further comprises a means for transferring heat between the fluid from the solar collector and the thermal storage medium 115 of the first container 113. In the present embodiment the heat transfer means comprises a conduit 155 for carrying the fluid from the solar collector 105 to the first container 113 and an optional heat exchanger 157 positioned within the first container for exchanging heat between the fluid and the first thermal storage medium 115. In other embodiments, a heat exchanger may be omitted and the fluid from the solar collector may be introduced directly into the first container.

The energy supply system further comprises a heat transfer means for transferring heat between the fluid from the solar collector and the second thermal storage medium 119 of the second container 117. In the present embodiment, the heat transfer means comprises a conduit 161 for carrying fluid from the solar collector 105 to the second container 117 and an optional heat exchanger 163 positioned within the second container for exchanging heat between the fluid and the second storage medium. In other embodiments, the optional heat exchanger 163 may be omitted

and fluid from the solar collector introduced directly into the second container.

The energy supply system further comprises a heat exchanger for exchanging heat between the second thermal storage medium and another entity. The other entity may comprise any device or element that may require thermal energy such as a device for providing space heating to the building, water heating and/or simply a supply of hot water or other liquid. In the present embodiment, shown in Figure 4B, for example, a heat exchanger 167 is provided for exchanging heat between the second thermal storage medium 119 and air for the interior of the building and a heat exchanger 169 for exchanging heat between the second thermal storage medium 119 and a supply of water 171. A water storage tank 173 may optionally be provided to store conditioned (e.g. heated) water from the heat exchanger 169. In some embodiments, the heat exchanger (s) may be arranged to exchange heat with the first storage medium. Other embodiments may include a heat exchanger for exchanging heat between the second storage (and/or first) medium and a process .

The energy supply system further includes a controller 175 for controlling the transfer of heat between the first thermal storage medium 115 and the fluid from the solar collector 105 and for controlling the transfer of heat between the second thermal storage medium 119 and fluid from the solar collector.

In this embodiment, the energy supply system further comprises a heat pump 179 for providing heating and/or cooling. The heat pump 179 may be operable to transfer heat from the first storage container 113 to the

second storage container 117. In one embodiment, one of the heat exchangers of the heat pump which carries refrigerant may be positioned within the first container and the second heat exchanger of the heat pump may be positioned within the second container. In other embodiments, the heat pump heat exchanger may be adapted to exchange heat between the heat pump refrigerant and another heat transfer fluid which is passed through a separate heat exchanger positioned within the first container. Alternatively, or in addition, the second heat exchanger of the heat pump may be arranged to transfer heat between the heat pump refrigerant and another heat transfer fluid which is passed to a separate heat exchanger within the second storage container.

In some embodiments, the heat pump may be arranged to transfer heat between any other device and a suitable heat source / heat sink 181. For example, the heat pump may be arranged to provide heating and/or cooling to any one or more of the air to liquid heat exchanger 167 and the liquid to liquid heat exchanger 169. The heat pump may comprise any type of heat pump, for example a geothermal heat pump, such as any of the geothermal heat pump systems described above with reference to Figures 2a to 2g, or an ambient air type heat pump .

Referring to Figure 4C, the energy supply system includes a fluid path switching and pumping system 177 for controlling the flow of fluid between various components of the energy supply system, under control of the controller 175. The fluid path switching system may comprise one or more valves which are capable of opening and closing a particular fluid path and/or regulating the flow of a particular path to provide positive flows of a plurality of different values. Embodiments of the fluid

path switching system 177 may control any one or more of the flow of fluid between the solar collector and the first storage container 113; the flow of fluid between the solar collector and the second storage container 117; the flow of fluid between the solar collector and the air-to-liquid heat exchanger 167; the flow of fluid between the solar collector and the liquid-to-liquid heat exchanger 169; the flow of fluid between the second storage container and the air-to- liquid heat exchanger 167; the flow of fluid between the second storage container and the liquid-to-liquid heat exchanger 169; the flow of fluid between the first storage container 113 and the air-to-liquid heat exchanger 167; the flow of fluid between the first storage container and the liquid to liquid heat exchanger 169; the flow of fluid between the first and second storage containers 113, 117, the flow of fluid between the first storage container and the heat pump 179 and the flow of fluid between the second storage container 117 and the heat pump 179.

The controller 175 may be connected to one or more sources of external data and operable to control the energy supply system based on the data. The data may include, for example, weather forecast data, such as the predicted amount of solar energy available during a predetermined future period of time, e.g. the next daily or other predetermined period, and/or the strength of solar radiation at the present time, as for example may be measured by a local sensor such as a light meter. The data may include data indicative of the cost of electricity at the present and/or a future time. The external data may be derived from the Internet or any other source or communication network, including, but not limited to, a wireless network, e.g. satellite and/or a land based wireless communication network .

In some embodiments, the controller may be arranged to control any one or more of a building heat delivery system, a hot water delivery system, a process heat or steam delivery system (which may, for example, be installed in a commercial or other building) , an electric heating element, a solar thermal collector, a solar electric collector, an electricity storage system, one or more conventional hot water storage tank(s), and one or more on- demand hot water system (s) . The controller may be operable to control any one or more of these elements based on temperature (s) and/or pressure (s) and/or flows at any appropriate position, and which may be measured by any suitable sensing or measuring device (s) .

Referring to Figure 4B, in some embodiments, a sump hole 190 is provided with a removable thermally insulated lid 192, and containing a sump pump 194 and a fill valve 196 connected to a suitable fluid source. This arrangement enables to the fluid level in the first storage container to be controlled by adding fluid, for example, to make up any fluid evaporated or otherwise lost, and pumping out any excess water that may seep in. The fluid level may be measured by a suitable device, e.g. by a limit switch (es) and the fluid level may be automatically controlled by the system controller 175, for example, or by another controller.

Long Term Low Temperature Thermal Storage Tank

Embodiments of the long term storage container may include any one or more of the follow features.

Some embodiments comprise an enclosed volume that is impervious to fluid flow, thermal conduction and convection, filled with structural elements and fluid

containing a means to transfer heat in the fluid from a heat source and to a heat sink.

In some embodiments, the enclosed volume is the basement or sub basement of a building.

In some embodiments, the enclosed volume is a separately buried tank, a reservoir, a community swimming pool, an effluent pond, a natural or man-made underground cavern.

In some embodiments, the enclosed volume is a wrap around tank adjacent to a building foundation and may use the area under the parking garage normally filled with sand or fine aggregate as a part of said enclosed volume.

Some embodiments include an enclosed volume where the combination of size, shape, thermal insulation level, and fluid needed is such that the maximum and minimum temperatures of the enclosed volume remain between about 45 ⁰ C and 0 ⁰ C upon absorbing all summer solar thermal energy that is not required for domestic hot water, and scavenging all the available heat stored for winter heating, respectively.

In some embodiments, the enclosure may contain an embedded (day tank) or short term thermal storage tank so that heat lost from the tank is lost to the long term thermal storage tank.

In some embodiments, the volume may contain fluid only such as water or brine .

In some embodiments, the volume is filled with fluid and rocks, or aggregate, or crushed stone or porous concrete which can act to support vertical structural loads

while the fluid such as water provides convenient heat transfer media.

In some embodiments, the optimum ratio of solid structural elements to fluid is calculated using appropriate data, and for example, one embodiment comprises between about 12% to 50% granite in a granite/water ratio as optimum, where up to 60% granite performs as well as water only, yet provides structure.

In some embodiments, thermal insulation is applied to outside of tank walls so that thermal mass of walls becomes a portion of the thermal mass of the tank.

In some embodiments, a water impervious layer of soil such as clay or silt or other naturally occurring bio material lines the outer walls of the enclosure to prevent fluid migration or leak from the tank.

In some embodiments, the enclosed volume 5 is lined with a water proof membrane to prevent fluid leak.

In some embodiments, the enclosed volume is thermally insulated all around.

Further examples of energy supply systems and long term storage containers are described below with reference to Figures 5 to 9 and Tables 1 to 3.

Figure 5 shows another embodiment of an energy supply system 201 installed below a building 203. The energy supply system 201 comprises one or more solar collectors 205, a first storage container 213 containing a thermal energy storage medium 215, and a second storage container 217 containing a second thermal energy storage medium 219. In this example, the first storage

container 213 is positioned below the basement 222 of the building 203, and may comprise a sub-basement, or a separate structure, for example. The first storage container 213 has container walls 223, 225, which may be formed of concrete, for example, or other material, and a base or floor 227, which may be formed of any suitable material . The container walls 223, 225 and/or the base 227 may be partially or completely surrounded by a water impervious layer 229, for example a water impervious layer of soil, such as clay or silt or other naturally occurring bio material to prevent fluid migration or leakage from the container. In some embodiments, any one or more of the container walls 223, 225, the base 227 or the top 231 of the first storage container may comprise an insulating material such as polystyrene (e.g. extruded Polystyrene) Celfort 300 ^® or similar material. Thermal insulation may be applied outside of the tank walls so that the thermal mass of the walls constitutes a portion of the thermal mass of the first container 213. The enclosed volume of the first container 213 may be lined with a waterproof membrane 233 to prevent fluid leakage .

In the embodiment of Figure 5, the first thermal energy storage medium 215 may comprise a liquid 235 such as water, brine, or other liquid, and solid material 237. The solid material may comprise solid pieces of rock or other material arranged within the volume of the container in such a way as to provide support for the top 231 of the container and structure above the container, e.g. building 203. The solid material may comprise rocks, stones or aggregate, crushed stone or porous concrete which can act to support vertical structural loads. In the example of Figure 5, the width of the first storage container 213 is greater than the width of the building, with the container walls being

positioned beyond the walls (either one or both) of the building.

In this embodiment, the second thermal storage tank or container 217 is positioned outside the first container 213, and may, for example, be located in the basement 222 of the building 203. Each of the first and second thermal storage containers 213, 217 are arranged to receive thermal energy from the solar collector (s) 205 via one or more fluid lines 241, 243.

In this embodiment, the energy supply system further comprises a heat pump 245 for upgrading and transferring heat from the first energy storage container to provide space heating, for example, for the building 203, as indicated by the arrows 247, 249. The heat pump 245 may also be arranged to upgrade and transfer heat from the first storage container to the second storage container, as for example described above with reference to Figures 4A to 4C. Thermal energy stored in the second storage container may be used for any suitable purpose, including space heating, water heating and/or process heating.

Some thermal energy may be transferred from the building into the first storage container as indicated by the arrow 249. In practice, some loss of thermal energy may occur from the first storage container to the ground surrounding the container as indicated by the arrow 251.

The energy supply system of Figure 5 may include any one or more of the components or features of the energy supply system described above with reference to Figures 4A to 4C.

Figure 6 shows another embodiment of a thermal energy storage system. In this embodiment, the storage system 301 comprises one or more storage containers 303, 305, 307 positioned in the ground and adjacent an existing basement 309 of a building 311, and a storage container 313 which is also positioned below ground and partially surrounds the existing basement 309, in this example on three sides thereof. Each of the storage containers 303, 305, 307 may be located below a parking garage 315, 317, 319, which is normally filled with sand, or fine aggregate. The thermal storage containers 303, 305, 307, 313 may be interconnected and effectively constitute a single storage container, or two or more separate storage containers. The storage containers may comprise a thermal storage medium comprising a fluid and solid material, as for any of the other embodiments of the first storage container described herein.

Figure 7 shows another embodiment of a thermal storage system. In this embodiment, the storage system 401 comprises a storage container 403, which completely surrounds the foundation 405 of a building. The storage container has first and second opposed walls 407, 409. The inside wall 407 of the container may be provided by the foundation wall of the building or may comprise a separate wall. The storage container 403 contains a thermal storage medium 411 comprising a fluid 413 such as water or brine and solid material 415. The solid material may or may not provide structure for supporting structure above the container. The inner and outer walls 407, 409 of the container 403 may be lined with a waterproof membrane 417 to prevent the leakage of fluid from the container.

In other embodiments of the long-term storage container, including those described above, the thermal storage medium may comprise a fluid only.

Table 1 of Figure 15 provides non-limiting examples of the values of various parameters associated with an energy supply system, and in particular, an example of the volume of an embodiment of the first (e.g. longer term) storage container or thermal storage medium, based on one day's energy use. In this example, the volume of the thermal storage medium is 30281itres. The reference to "spars" in the table refers to solar collectors. The table is for illustrative purposes only, and is in no way limiting of the invention.

In some embodiments, the thermal storage medium of the long term storage container may comprise a combination of different media, each medium having a different specific heat and density, and wherein the relative amount of each medium in the thermal storage medium is selected to increase the amount of energy that can be stored per unit volume per unit temperature above that that can be provided by a single one of the different medium.

Values of specific heat and density for water and a number of different materials (aluminum, steel and granite) are provided in Table 2 of Figure 15, and the 4 ^th column provides the value of their product, rho-C, the energy per unit volume per degree Kelvin. The last row in the table provides the values of specific heat, density and rho-C for a combination of 30% Granite and 70% Water.

Table 3 of Figure 16 provides values for the energy stored in the exemplary volume of 30281 for different materials (Column 2) , and the storage volume and mass

required for: 100% daily production (Column 3) ; 100% daily use (Column 4) and Net daily use (Column 5) . The net daily use is that portion of energy forced in the short term storage tank, and then used at night or during cloudy periods, for example. The table includes values for a combination of 30% Granite and 70% Water.

Figure 8 shows a graph of heat storage capacity (rho-C) as a function of relative proportions of water and granite, as determined from x times rho-C of water plus y times rho-C of granite, where x and y are the fraction or percentages of the material (where x+y=l) , as provided in Table 2. As can be seen from the graph of Figure 8, the heat storage capacity of the combination exceeds that of water for a content of granite between about 55% and 5%. An optimum range for the granite content may for example be defined as between about 12% and 47% as indicated in the graph.

In other embodiments, any combination of solid material (s) and liquid may be used for the storage medium, and the proportion of each material may be selected to increase the thermal storage capacity of the medium above that of a single component.

Figure 9 shows a graph of an example of the variation in temperature of embodiments of a long term storage medium with time. The curve 503 shows one example of the temperature variation, and curves 505 and 507 show other examples of temperature variation above and below curve503, respectively, and which are separated by a temperature of about 10 degrees C. Embodiments of the thermal storage volume may be formed, by, for example, any one or more of size, shape, thermal insulation level, material (s) of the

storage medium and fluid needed, and/or any other variables, such that the maximum temperature of the enclosed volume remains at or below about 45 degrees C, and/or the minimum temperature of the volume remains at or above about 0 degrees C, upon absorbing all available summer solar thermal energy not required for hot water, and scavenging all available heat stored for winter heating, respectively. The adiabatic curve is a no heat loss simulation and the 'ICEPAK' curve is a detailed computational fluid dynamics model of the thermal system (which is very close to reality) .

Figure 10 shows a graph of an example of the variation of COP (Coefficient of Performance) of a heat pump as a function of scavenging temperature, i.e. the temperature of the heat source from which heat is pumped. COP is defined as the amount of heat produced per unit of electrical energy used in producing the heat. The graph shows two curves, curve 603, which is the COP and curve 605, which is the linear COP. The upper curve is derived from test data of a heat pump. Both curves illustrate that COP increases substantially monotonically with scavenging temperature .

Controller Modes of Operation

Examples of modes of operation of an energy supply system are described below, with reference to the system shown in Figures 4a to 4c, and any one or more of these modes may be implemented in an energy supply system.

1) Sun shining and building or process calling for heat or hot water

The controller directs a thermal fluid stream 156 from the solar thermal collector 105 to the appropriate heat exchangers 167, 169 to provide any one or more of building heat, process heat and hot water.

2) Sun shining and no call for heat from process, building or water delivery system

(a) If the second container 117, e.g. day tank is at a predetermined maximum temperature, the controller 175 diverts the solar thermal fluid stream 156 to the first container e.g. long term thermal energy storage tank 113, to deposit heat into the thermal storage medium 115, either directly or via the heat exchanger 157.

(b) If the temperature of the storage medium of day tank 117 is below the predetermined maximum temperature, the controller diverts the solar thermal fluid stream 156 to the day tank 117 to thermally charge the thermal storage medium 119, either directly or via the heat exchanger 163.

3 ) Night

a) If the day tank 117 has useable thermal energy, e.g. has a temperature at or above a predetermined value, for example, > 10 ⁰ C, and heat is required, the controller causes heat from the day tank to be transferred to the appropriate point (s) where heat is required, where it may be used, for example, to pre-heat process or hot water or directly for building heating. This may be achieved by drawing liquid directly from the day tank 117 and passing the liquid through one or more heat exchangers 167, 169, for example, or by passing a heat transfer fluid through the heat exchanger 163 in the day tank and then to the appropriate external heat exchanger (s) 167, 169.

b) If the day tank 117 has no useable thermal energy, e.g. has a temperature of < 10 ⁰ C (or some other temperature) and the weather forecast for the following day is no sun, the controller controls the system to charge the day tank with thermal energy by controlling the heat pump 179 to upgrade and transfer heat from the long term thermal storage tank 113. In some embodiments, the controller only causes this operation if the cost of electricity is below a predetermined value. This condition may be indicated by a low electricity price flag. The controller may monitor the temperature of day tank 117 as it being thermally charged, and cease the transfer of heat thereto once the temperature reaches a predetermined value . The predetermined temperature value may be based on the materials in the system and/or the boiling point of the fluid in the day tank, and/or a requirement to reduce heat loss to the building. For example, the predetermined temperature may be below the boiling point of the fluid, e.g. less than 100 ⁰ C for water to avoid boiling and/or a temperature which assists in minimising heat loss to the building.

The heat required by the process, building, or hot water delivery system may be provided directly by any one or more of respective electrical heater (s), by the day tank, once it has been charged with sufficient thermal energy, and/or by the heat pump 179.

c) If the weather forecast for next day (or some other predetermined period of time) is partially sunny then charge the tank by the heat pump with an amount of thermal energy based on the predicted amount of solar thermal energy available the next day. For example, the heat pump thermal charge may by such that the heat pump thermal charge plus the predicted solar thermal charge together substantially

equals one full day charge, e.g. with the final temperature of the tank Temp _C h _ar ge = the maximum temperature Temp _max . In other words, the controller may be adapted to operate the heat pump for a period of time which is just sufficient to make up the short fall of thermal solar energy available the next day due to the partial amount of predicted sunshine. In this case, the heat pump may be operated to charge the tank to a temperature Temp _C harge = x% * Temp _max , where 1-x is the fraction, e.g. percentage, of predicted thermal solar energy available the next day.

Weather forecast data/information may be obtained automatically by the system from any suitable source, for example, a control operating station on the internet.

(d) If the temperature of the long term thermal storage tank is below a predetermined value, for example < 2 ⁰ C (or some other temperature) , then the controller activates the electric heating element 170 in the day tank and/or an on-demand hot water heater 176 to charge the day tank. The amount of heating may be controlled depending on the predicted amount of solar thermal energy available the next day, as per (3b) or (3c) , describe above, for example. In this case, if no sun is predicted for the next day, the controller may operate the appropriate heater (s) to charge the day tank to Temp _max , i.e. its full thermal charge, e.g. as in (b) . On the other hand, if partially sunny conditions are predicted for the next day, the controller may operate the heater (s) to partially charge the day tank, for example to a temperature Temp _cha rqe = x% * Temp _max , as in (c) .

4) Cloudy - day time

Use solar thermal energy from day tank directly if called for and if available. If not, upgrade through heap

pump from long term tank to supply building heat or process or hot water directly on demand - do not charge day tank if low cost electricity beacon is not on - as indicated by controller connection to control operating station on the internet, i.e.: charge day tank only at night with inexpensive electricity - during the day use expensive electricity only on demand!

5) Day time - Partially cloudy

(a) The controller controls the flow heat transfer fluid from the solar collector so that solar thermal energy, as available, is used directly for process and/or building heat and/or hot water, as required. The controller may be arranged to control the flow of fluid to divert excess solar thermal energy to the day tank until the maximum and/or a predetermined temperature is achieved.

(b) If the maximum and/or predetermined day tank operating temperature is achieved, the controller may control the flow of fluid to divert solar thermal energy to the long term low temperature storage volume 113.

In the above example 5 (a) , excess solar thermal energy may be diverted to the short term storage tank 117 in preference to the long term storage tank 113 over a period of time until a predetermined criterion is met, in this case, until the short term storage tank reaches a predetermined temperature. This means that more solar thermal energy is passed to the short term storage tank over this period than to the long term tank, and in some embodiments, little or no solar thermal energy is passed to the long term storage tank.

In the above example 5 (b) , excess solar thermal energy may be diverted to the long term storage tank 113 in preference to the short term storage tank 117 once a predetermined criterion is met, in this case, once the short term storage tank reaches a predetermined temperature. This means that more solar thermal energy is passed to the long term storage tank over this period than to the short term tank, and in some embodiments, little or no solar thermal energy is passed to the short term storage tank once the predetermined condition is met.

If in any of cases 1 to 5 above, the long term storage tank reaches its maximum and/or a predetermined temperature, the controller may be arranged to cease the transfer of solar thermal energy thereto, for example by stopping the flow of heat transfer fluid from the solar collector to the long term tank, and/or controlling the solar collector to look away from sun, for example by sending an appropriate signal to an activator for controlling the position of the solar collector and/or to stop collecting solar thermal energy.

6) Cooling - e.g. Summer and/or when required

The heat pump 179 of the system shown in Figures 4a to 4c may be operable in refrigeration mode to provide cooling. As mentioned above, the heat pump may be geo-source or air based. Alternatively, or in addition, the system may include a dedicated air conditioner heat pump, e.g. a heat pump which only operates in refrigeration mode.

The system may be arranged to operate in any of the following cooling modes.

(a) If there is a call for cooling and the temperature of the long term thermal storage tank is in a useful cooling range, for example, at or below 15 to 10 ⁰ C or another temperature, or within a predetermined range, e.g. 0 to 15 ⁰ C, as for example indicated by the range 705 in Figure 7, the fluid from the long term storage tank can be directly or indirectly (through a heat exchanger, for example heat exchanger 157) transferred to the building or process cooling appliance such as a fan coil in a forced air cooling system, e.g. heat exchanger 169 in Figures 4a to 4c.

(b) If the temperature of the long term low temperature thermal storage tank 113 is above a predetermined temperature, for example, the useful cooling temperature, e.g. above 10 to 15 ⁰ C, the controller may operate the heat pump in refrigeration mode, rejecting heat to the long term thermal storage volume 115 and supplying cooling to the building and/or process cooling system. In some embodiments, a heat exchanger of the heat pump serving as an evaporator may be arranged to absorb heat directly from the medium to be cooled, or may be arranged to absorb heat from the medium by exchanging heat with an intermediate heat transfer agent or fluid, which circulates between, and is in heat exchange relationship with, both the refrigerant and the medium to be cooled. In some embodiments, a heat exchanger of the heat pump serving as a condenser may be arranged to deposit heat directly from the refrigerant into the long term storage tank 113, in which case the heat exchanger may be positioned within the long term storage tank to transfer heat directly to the thermal storage medium 115. In other embodiments, the condenser may be arranged to deposit heat into the long term tank indirectly by exchanging heat with an intermediate heat transfer agent or fluid, which circulates between, and is in heat exchange

relationship with, both the refrigerant and the thermal storage medium.

This mode of operation allows heat which is rejected to provide cooling, and which would otherwise be wasted to ground or atmosphere to be stored for later use . The stored heat may, for example, be stored long term for use in the next heating season and/or may be used in a relative short term, for example later that same day or the next day or any subsequent time if there is a call for heat, for example, either side of winter, i.e. spring or autumn. Another benefit is that the amount of energy required for cooling can be considerably reduced as there may be no requirement to actively circulate the fluid of the long term storage tank relative to the condenser heat exchanger of the heat pump if the heat exchanger is positioned within the long term storage tank, or only a small parasitic energy use for pumping the fluid of the thermal storage medium (or an intermediate heat transfer fluid in heat exchange relationship with the thermal storage medium) in heat exchange relationship with the condenser, in comparison to the energy required by conventional air fan-based cooling tower systems or fan-coil systems, usually mounted on roof tops or adjacent to the building being cooled.

Figure 9 shows an example of a graph of COP of a heat pump operating in heating mode as a function of temperature of the available heat source (i.e. scavenging temperature. The COP increases with temperature from about 3 at 0 degrees C to about 8.5 at 35 degrees C. The increase is substantially linear.

Embodiments of the system may provide any one or more of the following benefits.

a) Embodiments of the system may be arranged so that the temperature of the thermal storage medium of the long term storage container attains temperatures that are higher than the ground-based heat sources (e.g. ground or water) . For example, the thermal storage medium may attain temperatures of 35 degrees C or more, as shown in Figure 7. These higher temperatures allow the system heat pump to operate more efficiently, with higher COP'S. For example, referring to Figure 9, the system allows COP's of between 8 and 9 to be achieved, as indicated by point 905, for example, in comparison to a COP of between 3 and 4, e.g. point 903, for a conventional geothermal heat pump, where the available heat source temperatures are typically -10 to +1O ⁰ C in winter, depending on how much heat is removed from the ground, and between 10 to 30 ⁰ C in Summer, depending on how much heat has been input by the heat pump.

b) The system allows heat to be derived from the long term storage tank by means of a heat pump at a time, e.g. night, when the cost of electricity is low, i.e. off- peak and to charge the day tank with the heat for subsequent use, which may be at a time when the electricity price is higher (e.g. during day time) . Thus, for example, the daytime storage tank may be charged at one half the peak electricity price, making the cost based COP as high as 17, if the "off peak" electricity is one half the price of "on- peak" electricity.

c) Embodiments of the system captures a large percentage of rejected air conditioning heat, for example, in the summer or at other times when air conditioning is needed, for use in winter heating, for example, or at other times when heat is needed.

(d) The provision of solar thermal storage of embodiments of the system enables solar thermal plus electric collectors to be reduced in size, for example, sized approximately 40% smaller and still supply substantially 100% of net thermal and electrical energy for a building. The solar electric collector can be made smaller due to the reduced electricity load required by the heating system as a result of the thermal storage system and its operation and timing of generating and storing heat. Additionally, in embodiments of the solar collector, both heat and electricity are generated using the same surface area. If the collector has PV electric cells and solar thermal panels, the area would be larger.

The above operational modes may provide maximum system efficiency and thus enable the building so fitted to require little or no other net energy except that supplied by the sun to heat the building, and provide the occupants with all their hot water and electricity thus providing a zero net energy building.

Heat Pump Loop Solar Booster

Many geo-thermal systems suffer from under sized heat scavenging loops, such as the loops 13, 15, 17 shown in Figures 2a to 2c, so they tend to freeze in cold winter months rendering the heat pump inefficient and/or forced to operate in "regular electric heat only" mode at 2 to 4 times the electricity cost compared to heat pump mode .

An aspect of the present invention provides a thermal solar collector in combination with a heat pump to provide additional thermal energy to the heat pump heat exchanger fluid to assist in preventing freezing and/or

increasing the ability of the heat pump to operate effectively in cold climates. The solar thermal energy may be transferred into a heat transfer fluid, which is circulated in heat exchange relationship with the heat pump to draw the heat therefrom. The heat transfer fluid may be circulated in a loop, which includes the ground loop of the geothermal heat pump, or circulated in a separate loop, which may or may not be used to warm the ground around the geothermal ground loop .

An example of an embodiment of the system is shown in Figure 10. The system 950 comprises a heat pump 951, a geothermal ground loop 953 for carrying a heat transfer fluid for absorbing heat from the ground and passing the fluid in heat exchange relationship with the evaporator of the heat pump, and a solar collector 955. The solar collector includes one or more heat exchange conduits 957 for carrying heat transfer fluid to absorb solar thermal energy, and which includes an inlet 959 connected to the ground loop at a point "P" by a first valve 961, and an outlet 963 connected to the ground loop at a point "Q" by a second valve 965. A pump 967 is provided to pump heat transfer fluid through the ground loop 953 and solar collector 955, and an optional fluid bypass 969 and bypass valve 971 are provided to enable the fluid flow to bypass the heat pump. A controller is provided to control operation of the valves 961, 965, 971, to control the fluid path, and to control operation of the pump 967. The system may be controlled so that heat can flow directly from the solar collector to the heat pump, or heat can be scavenged from the ground to the heat pump, or from a mixture of solar heat and ground heat. The controller may monitor the temperature of each heat source and determine a mode of operation that may, for example provide increased heat pump efficiency.

In operation, when no additional heating from the solar collector is required, each of the valves is controlled to permit the heat transfer fluid to circulate through the ground loop 953 and to by pass the solar collector. When heating form the solar collector is required, the controller 973 switches the first valve to connect the fluid path to the inlet 959 of the solar collector and switches the second valve to connect the outlet 963 of the solar collector to the fluid path, so that the heat transfer fluid passes through the solar collector, absorbs heat, is passed through a portion of the ground loop and then to the heat pump. In this case, the fluid path bypasses part of the ground loop, i.e. between points "P" and "Q" . By passing part of the ground loop if cold, prevents cooling of the solar loop and degradation of heat pump efficiency.

The controller may control the fluid direction valves, monitor loop fluid temperature and control pump 967 to optimize the performance of the heat pump. A non-limiting example of values that may be used to increase the efficiency or optimise heat pump performance is provided in Table 4 of Figure 17.

If there is solar energy available from the collector when the building (or process) is not calling for heat, the controller may be operable to activate the pump 967 and valves 961, 965, 971 to by-pass the heat pump via fluid path 969 and to warm the ground and collector loop and enable photovoltaic cells in the solar collector (if present) to be cooled, so that, for example, cooling of the cells may be effected all year round.

The embodiment of Figure 10 allows the heat pump to operate effectively in cold climates, reducing or avoiding the need for supplementary heat form other sources such as direct electric heat.

In other embodiments, a separate conduit may be provided adjacent the ground loop to carry fluid from the solar collector to warm the ground. The separate conduit may be in addition to the provision of adding solar heated fluid to the ground loop fluid path, or as an alternative thereto.

Embodiments of the system may exist alone or incorporated into other systems, for example systems having thermal storage as described in the examples above with reference Figures 4a to 4c or any other embodiment described herein.

Short Term Thermal Storage Tank

Some embodiments comprise a thermally insulated and fluid tight enclosed volume fluidically connected to the output of a liquid-to-liquid, e.g. water-water (e.g. geo- source) heat pump and/or a solar thermal collector and/or an electric heating element, sized so as to provide one day (or other predetermined period) of thermal energy requirements for the building it is installed in, and connected fluidically so as to enable the supply of hot water and building heat for the building installed therein.

In some embodiments, the tank is non pressurized and includes any one or more of the following features. An inner fluid tight bladder or liner, a thin gauge sheet metal or similar structural sheet material to take the radial hydraulic loads from the fluid, a shape forming angle top and bottom, a liner edge guard to hold the liner in place, a

radial thermal insulating material, structural top and bottom thermal insulating material, an outer insulation cover made from plastic or thin sheet metal, a moisture barrier cover to prevent moisture migration from tank top, an over-fill drain, an upper level limit switch, a lower level limit switch, a temperature probe, an inlet and exit for heat storage fluid and a flow reversal preventer (back flow valve) and a lid locking strap.

In some embodiments, inner and outer tank walls are thin gauge metal or structural plastic and can be rolled up to a smaller diameter than that of the tank for easy- entry into small doorways and then assembled in their final usage position.

In some embodiments, the inner and outer tank walls have a hem seal running vertically and/or are riveted and/or glued in their final usage position.

In some embodiments, the internal liner is flexible and conforms to internal shape of the tank and may be made from polyvinylchloride tarpaulin material or similar moisture impervious membrane.

Figures 12A and 12B and 13A to 13E show various views and components of a thermal storage container according to an embodiment of the invention, and which may be included in any embodiment of an energy supply system, including any embodiments described herein. Referring to the Figures, the storage container 501 comprises a cylindrical wall 503, which includes a structural wall 505 and an inner, fluid impermeable bladder or liner 507. The structural wall 505 may be formed of any suitable material, including sheet material. Referring to Figures 13A and 13D, a retainer 509 is provided for holding the liner in place,

and in this embodiment is positioned adjacent an upper portion and edge of the cylindrical container wall 503. The container wall further includes a thermal insulating material for insulating the enclosed volume of the container to reduce heat loss therefrom. The insulating material 513 is provided on the outside of the container, although in other embodiments, the insulating material may be provided on the inside and/or outside of the container. The container includes a structural top 515 and a structural bottom 517 which may include a thermal insulating material. An outer insulation cover 519 may be provided around the insulation layer and may be made from plastic or thin metal sheet or other suitable material . A moisture barrier cover 521 is provided to prevent moisture migration from the top of the thermal storage container.

The thermal storage container may further include any one or more of an overfill drain, for example mounted in the side thereof, a sensor for sensing the level of fluid in the container and which may be used to control the level of fluid within the container, for example by means of a limit switch, a level sensor for sensing a low level of fluid in the container which may be used to control a switch to cause fluid to be introduced into the container, for example by means of a lower level limit switch. The container may include a temperature sensor for sensing the temperature of the fluid medium within the container. The container includes a fluid inlet and fluid outlet for heat storage fluid and an optional flow reversal preventer (e.g. back flow valve) to allow fluid to pass only in one direction. A locking mechanism may be provided to lock the lid to the container.

Referring to Figures 13A, 13B, 13C and 13E, a heat exchanger coil 523 may be provided within the container having appropriate fluid connectors 525.

Other aspects and embodiments of the present invention may comprise any one or more features disclosed herein in combination with any one or more other features disclosed herein or their equivalent or a variant thereof. In any aspect or embodiment of the present invention, any one or more features disclosed herein may be omitted altogether or replaced or substituted for another feature which may or may not be an equivalent or variant thereof.

Numerous modifications and changes to the embodiments described herein will be apparent to those skilled in the art.