Energy storage systems

Abstract

There is herein described energy storage systems. More particularly, there is herein described thermal energy storage systems and use of energy storable material such as phase change material in the provision of heating and/or cooling systems in, for example, domestic dwellings.

Claims

1. A thermal energy store, comprising: a first heat transfer fluid that has exchanged heat with at least one or more of a heat source; a configuration of three or more thermal energy storage banks having at least a first energy storage bank, a second energy storage bank and a third energy storage bank; wherein each of said first energy storage bank, said second energy storage bank and said third energy storage bank are encased at least in part in an insulation; wherein each of said first energy storage bank, said second energy storage bank and said third energy storage bank are at least in part insulated from one another by said insulation respectively configured between each of said first energy storage bank, said second energy storage bank and said third energy storage bank; wherein said first heat transfer fluid is respectively fed to one or more thermal energy storage banks of said configuration of three or more thermal energy storage banks that are configured in parallel; said first energy storage bank having a first feed point for feed of said first heat transfer fluid, said second energy storage bank having a second feed point for feed of said first heat transfer fluid and said third energy storage bank having a third feed point for feed of said first heat transfer fluid; wherein said first heat transfer fluid is configured as a first heat transfer fluid feed to any one or more of said first feed point, said second feed point and said third feed point; wherein said first heat transfer fluid is configured to be fed in a parallel feed configuration to any two or more of said first feed point, said second feed point and said third feed point; wherein each of said three or more thermal energy storage banks has a temperature, wherein the temperature of at least two of said first energy storage bank, said second energy storage bank and said third energy storage bank is different; wherein each of said first energy storage bank, said second energy storage bank and said third energy storage bank are configured to be fed said first heat transfer fluid configured to provide an energy transfer connection with at least one thermal energy source and to transfer heat from said thermal energy source to said configuration of three or more thermal energy storage banks; a control system of the thermal energy store configured to execute control logic controlling a flow rate of said first heat transfer fluid into one or more of said first energy storage bank, said second energy storage bank and said third energy storage bank; wherein said first heat transfer fluid is fed in a parallel feed configuration to two or more of said first energy storage bank, said second energy storage bank and said third energy storage bank; said control system controlled by a controller that is at least one of a thermostat, a mechanical controller, an electrical controller, and a control program running on a programmable computation system, said control system configured by the controller to provide flow of said first heat transfer fluid respectively to feed one or more of said first energy storage bank, said second energy storage bank and said third energy storage bank in response to at least one of a physical state of said respectively fed energy storage bank and the physical state of the environment surrounding the thermal store; said control system configured to control a first flow rate of a first flow of said first heat transfer fluid to at least one of at least one of said first energy storage bank, said second energy storage bank and said third energy storage bank; and said control system configured to control a second flow rate of a second flow of said first heat transfer fluid to another of said first energy storage bank, said second energy storage bank and said third energy storage bank; said control system configured to control said first flow rate optionally at a different flow rate than said second flow rate; a second heat, transfer fluid flowing to at least one of said first energy storage bank, said second energy storage bank and said third energy storage bank; wherein said second heat transfer fluid is fed in series to two or more of said first energy storage bank, said second energy storage bank and said third energy storage bank, wherein the control system adapts the thermal energy transfers within, and at least one of to and from the thermal energy store; wherein at least one or more of the thermal energy storage banks contains a thermal energy storage material comprising a single material or a mixture of materials; wherein the thermal energy storage material of at least two of said three or more thermal energy storage banks comprises a different thermal energy storage material, and each of said different thermal energy storage material has a different melting point; wherein at least one of said thermal energy storage banks comprises a first thermal energy storage material having a first transition temperature and at least one of said thermal energy storage banks comprises a second thermal energy storage material having a second transition temperature, said first transition temperature and said second transition temperature differing in transition temperature in a range of 5° C. to 35° C.; wherein a plurality of said thermal energy storage banks respectively have different of said thermal energy storage materials which have different said transition temperatures and each of the plurality of said thermal energy storage banks have a respective feed inlet to receive a flow of said first heat transfer fluid; wherein said control system is configured to control the feed of said first heat transfer fluid to a respective thermal energy storage bank based upon the transition temperature of the thermal energy storage material of the respective thermal energy storage bank; said control system configured to selectively control which one or more of said plurality of said thermal energy storage banks is fed said first heat transfer fluid through the respective feed inlet based upon the transition temperature of the thermal energy storage material of a respective thermal energy storage bank; wherein said thermal energy storage material comprises material that undergoes one or more of an energy absorbing phase transition at one or more temperatures within an operating temperature range of each bank and an energy releasing phase transition at one or more temperatures within the operating temperature range of the respective bank; wherein each phase transition is associated with a change in at least one of a physical property and a chemical property of said thermal energy storage material; wherein each of said first energy storage bank, said second energy storage bank and said third energy storage bank contain a heat exchanger which is configured to exchange heat with a second heat transfer fluid which is fed to said configuration of three or more thermal energy storage banks and said second heat transfer fluid is configured to provide an energy transfer connection with at least one thermal energy sink which is external to the thermal energy store and to exchange heat with said at least one thermal energy sink.

2. A thermal energy store according to claim 1, wherein one or more of said thermal energy storage banks is capable of at least one of storing and releasing thermal energy at a range of one or more temperatures; said storing or releasing thermal energy can occur at least one of to and from of at least one of thermal energy sources and sinks simultaneously, or at different times; and wherein said phase transitions are reversible without substantial loss of energy absorbing, energy storing or energy releasing capacity across at least two reversible cycles.

3. The thermal energy store of claim 1, wherein the phase transition absorbs or releases substantially more energy at the said one or more temperatures than would be the case taking account solely of the energy absorbed or released as specific heat and wherein at least one bank contains one or more heat exchanger means operable to permit thermal energy to be transferred.

4. The thermal energy store of claim 1, wherein the thermal store, each bank and a plurality of banks are capable of accepting, storing and releasing thermal energy from one or more thermal energy sources and/or sinks simultaneously or at different times and wherein a first bank of the thermal store is at least partially enclosed within a second bank.

5. The thermal energy store of claim 1, wherein thermal energy is caused to move within or through a thermal energy transfer connection by the application of external energy selected from the group consisting of one or more of pumping a heat transfer fluid, heat pumping, thermoelectric effects, thermionic emission, convection, thermosyphoning and capillary action, in such a way as to promote the function of the thermal energy transfer connection to transfer thermal energy from a thermal energy source at one end of the thermal transfer connection to a thermal energy sink at the other end of the thermal transfer connection or vice-versa and wherein a thermal energy transfer connection comprises one or more devices for transferring heat from a lower temperature body to a higher temperature body, wherein such devices are selected from one or more of the group consisting of a vapor compression heat pump; a chemical heat pump; a thermoelectric device; a thermionic device; and any other device operable to move heat from a lower temperature body to a higher temperature body.

6. The thermal energy store according to claim 5, wherein the thermal store incorporates integrally within its function, structure or control logic one or more devices for transferring heat from a lower temperature body to a higher temperature body and wherein at least one thermal energy transfer connection links two or more banks and comprises one or more devices for transferring heat from the lower temperature body to the higher temperature body.

7. The thermal energy store of claim 1, wherein at least a first and second bank having overlapping or identical operating temperature ranges are connected by thermal energy transfer connections, wherein at least a first and second bank having distinct, non-overlapping operating temperature ranges are connected by thermal energy transfer connections and wherein every bank within the thermal energy store is connected only to another bank having a phase transition temperature which is different than the phase transition temperature of the given bank.

8. The thermal energy store of claim 1, wherein at least one of the following: thermal energy source external to the thermal energy store and at least one thermal energy source within the thermal energy store lacks a direct thermal energy transfer connection via a destination bank within the thermal energy store, to at least one thermal energy sink external to the thermal energy store, or both; and wherein thermal energy can still be transferred between the source and destination or vice-versa and wherein transfer of thermal energy from a source using a first thermal energy transfer connection causes thermal energy to be added to the energy stored in the at least one intervening bank, where thermal energy is stored temporarily, and wherein simultaneously, previously, or later thermal energy is removed from the said intervening bank and transferred using a second thermal energy transfer connection to a destination.

9. The thermal energy store of claim 1, wherein sources and destinations of thermal energy transfers are switched in succession or in parallel such that at least at some times thermal energy is transferred from one external source to a selected bank when the thermal energy storage material in the selected bank has a lower average, maximum or minimum temperature than the temperature of the external source of thermal energy and wherein a selected bank is chosen because it is, at that time, the hottest bank amongst all banks of the thermal energy store that have temperatures lower than an external thermal energy source and/or the temperature of an external thermal energy source less a fixed temperature decrement.

10. The thermal energy store of claim 1, wherein a selected bank is chosen because it is, at that time, the bank most depleted in thermal energy and wherein after or at the same time as thermal energy is transferred from an external thermal energy source to a selected bank, potential to transfer thermal energy to other banks in the thermal energy store remains, and at least a further bank is selected to accept some or all of the remaining thermal energy that could be potentially transferred in sequence or at the same time to be further directed by an arrangement of one or more additional thermal energy transfer connections in sequence to heat exchanger means in one or more additional banks, wherein the one or more additional banks are visited in descending sequence of average, maximum or minimum temperature of the thermal energy storage material within each bank.

11. The thermal energy store of claim 1, wherein two or more sources or destinations of thermal energy transfers are switched in succession or parallel such that at a given time thermal energy is transferred to one external sink of thermal energy from a selected bank having a higher average, maximum, or minimum temperature in its thermal energy storage material than the temperature of the external sink of thermal energy, wherein a selected bank is chosen because it is, at that time, the coldest bank amongst all banks of the thermal energy store that have temperatures higher than an external thermal energy sink or the temperature of an external thermal energy sink plus a fixed temperature increment and wherein a selected bank is chosen because it is, at that time, the bank containing the largest quantity of thermal energy.

12. The thermal energy store of claim 1, wherein after or at the same time as thermal energy is transferred to an external thermal energy sink from a selected bank, potential to transfer thermal energy from other banks in the thermal energy store remains, and one or more further bank banks is selected to provide some or all of the remaining thermal energy that could be potentially transferred in sequence or at the same time to one or more additional banks, wherein the one or more additional banks are visited in descending or ascending sequence of average, maximum or minimum temperature of the thermal energy storage material within each bank before it is directed by a final thermal energy transfer connection to the external thermal energy sink from the last bank.

13. The thermal energy store of claim 1, wherein the number, order, phase transition temperature, current average, maximum or minimum temperature of banks to include in the transfer of thermal energy via an external source or an external sink is chosen such that the return temperature of any thermal energy transfer fluid that flows back from the thermal energy store is better adapted to or is optimally matched to a characteristic of the external source or external sink of any of the following: the temperature at which thermal energy transfer fluid flowing into the external source or external sink will deliver, collect, reject, generate or convert thermal energy most optimally; returning thermal energy transfer fluid to a solar thermal panel during the day at a low temperature so that radiative losses from the solar panel are minimized and therefore the solar panel operates as efficiently as possible to collect heat; returning thermal energy transfer fluid to a solar thermal panel during the night or a radiator at a high temperature so that radiative losses from the solar panel or radiator are maximized and therefore the solar panel or radiator operates as efficiently as possible to reject heat; returning thermal energy transfer fluid to a gas boiler within the design temperature range for which its operation is designed and rated to be most efficient; or returning thermal energy transfer fluid to a back boiler in a wood-burning stove at a temperature at which the thermal energy transfer fluid will not boil, and at which the structure of the stove will not crack due to thermal stress.

14. The thermal energy store of claim 1, wherein an external source of thermal energy is selected from a group consisting of a fluid, environment containing waste, excess thermal energy from a process including that of exhaust warm air from a building in a cold environment, exhaust cool air from a building in a warm environment, waste warm water from bathing or showering, oil in a heat engine requiring cooling before re-use, a fuel cell, a biogas digester and a bio-fuel production plant, wherein the thermal energy store is used to capture waste heat, excess heat or both from a fluid, an environment, or both, and wherein the rate of thermal energy transfer from lower to higher temperature banks is lower than the peak rate at which thermal energy transfers to the lower temperature banks from waste or excess energy sources.

15. The thermal energy store of claim 1, wherein the thermal energy store is used is one or more thermal energy stores selected from the group consisting of: a heating system; to provide a heating service; a cooling system; to provide a cooling service; a combined heating and cooling system used at the same time as both a cooling system and a heating system to simultaneously provide heating and cooling services; a combined heating and cooling system used at different times as both a cooling system and a heating system to provide heating and cooling services at different times; a central heating system; a distributed space heating system; water heating; heating thermal energy transfer fluids to provide industrial process-heat, directly heating working fluids of an industrial process; cooling thermal energy transfer fluids to provide industrial process-cooling, directly cooling working fluids of an industrial process, heating heat-transfer fluids for use in a machine that converts thermal energy, or temperature differences, into electrical or mechanical energy; a central cooling or air conditioning system; a distributed space cooling or air conditioning system; and a refrigeration system.

16. The thermal energy store of claim 15, wherein the thermal energy transfer fluid is a liquid or a refrigerant, wherein at least one bank of the thermal energy store is used as a thermal store for at least one of the following: heating, cooling, or a combined service, or is used as a thermal store for at least one service that is used at least some of the time for heating and the same service is used at least some of the time for cooling, wherein the thermal energy store is used for one or more heating or cooling functions selected from the group consisting of space heating, cooling delivered through radiant walls, under-floor heating, radiant ceilings, chilled beams, radiators, over-sized radiators, fan-coil radiators and air handling systems.

17. The thermal energy store of claim 1, wherein at least a sub-part of at least one bank of the thermal energy store is physically co-located with or adjacent to a point of delivery of the service for which it is a thermal energy reservoir and is selected to have a usual operating temperature range suitable to directly drive said service, wherein the thermal energy store is used inside one or more devices selected from the group consisting of domestic appliances, commercial appliances, industrial appliances, and machinery, and wherein the machinery is selected from the group consisting of a dishwasher, a washing machine, a machine that delivers hot and cold drinks; a vending machine for hot food; a vending machine for hot drinks; a vending machine for cold food; a vending machine for cold drinks; a system incorporating re-usable and re-chargeable heated cups, and a system incorporating re-usable and re-chargeable cooled cups.

18. The thermal energy store of claim 1, wherein at least one bank or the whole thermal energy store is used as a heat battery, a cool battery, or both.

19. The thermal energy store of claim 1, wherein the at least one thermal energy source or thermal energy sink is selected from the group consisting of flat plate solar collectors; evacuated tube solar collectors; roof tiles; dedicated solar air heaters; photovoltaic panels; and hybrid solar thermal photovoltaic panels; and wherein the at least one thermal energy source is waste heat from an electronic assembly or other device that generates waste heat selected from the group consisting of computer processors; micro-processors; amplifiers; batteries; lighting equipment; LED lighting; an electric motor; an internal combustion engine; and photovoltaic solar cells.

20. The thermal energy store of claim 1, wherein the ability to transfer thermal energy, of one or more of the following: a thermal energy transfer connection; a part of a thermal energy transfer connection; heat exchanger means within a bank connected to such a thermal energy transfer connection; and heat exchanger means external to the thermal energy store connected to such a thermal energy transfer connection, is modulated between a state in which the ability to transfer thermal energy is maximally resistant to, or completely incapable of, transferring thermal energy and a state in which the ability to transfer thermal energy is at its minimal resistance to transferring thermal energy or; is modulated to any degree of permissiveness between the minimum and maximum levels.

21. A thermal energy store according to claim 1, wherein the thermal store is capable of at least one of storing and releasing thermal energy at a range of one or more temperatures; said storing or releasing thermal energy can occur at least one of to and from at least one of thermal energy sources and sinks simultaneously, or at different times; and wherein said phase transitions are reversible without substantial loss of energy absorbing, energy storing or energy releasing capacity across at least two reversible cycles.

22. The thermal energy store according to claim 1, wherein an exchange of heat from at least two of said first energy storage bank, said second energy storage bank and said third energy storage bank is a heat exchange transferring heat into the second heat transfer fluid; and wherein the heat exchange transferring heat into the second heat transfer fluid is counter to a heat exchange of the first heat transfer fluid.

23. The thermal energy store according to claim 1, wherein each of said first feed flow rate is based upon data comprising at least the temperature of said first energy storage bank, said second feed flow rate is based upon data comprising at least the temperature of said second energy storage bank, and said third feed flow rate is based upon data comprising at least the temperature of said third energy storage bank.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawing in which:

(2) FIG. 1 is a schematic representation of an energy storage system according to a first embodiment of the present invention;

(3) FIG. 2 is schematic representation of an energy storage system according to a further embodiment of the present invention comprising a nested multi-bank phase change material heat store;

(4) FIG. 3 is a schematic representation of an energy storage system according to a further embodiment of the present invention of a nested multi-bank phase change material heat store used for underfloor heating as well as water heating;

(5) FIG. 4 relates to a single heat pump directly connected between two PCM stores, one intended to store and provide warmth for heating and hot water and one intended to store and provide coolth for cooling according to a further embodiment of the present invention;

(6) FIG. 5 is a reconfigured store which has two centres (one cold, one hot) and an outermost bank at or close to room temperature according to a further embodiment of the present invention;

(7) FIG. 6 relates to a single time-shared heat pump with many-to-many (i.e. multiple) connectivity according to a further embodiment of the present invention;

(8) FIG. 7 relates to a heat pump performing dual duty and two heat transfer buses according to a further embodiment of the present invention;

(9) FIG. 8 relates to pulling heat from an environmental source using a heat pump and lower capacity heat pumps interposed between each bank according to a further embodiment of the present invention;

(10) FIG. 9 relates to multi bank PCM heat & cool store for domestic heating, hot water and air conditioning from environmental heat sources using a shared heat pump according to a further embodiment of the present invention;

(11) FIGS. 10 and 11 relate to a radiator-based central heating system according to a further embodiment of the present invention.

DETAILED DESCRIPTION

(12) FIG. 1 is a representation of an energy storage system according to the present invention generally designated 100. The heating/cooling system comprises a series and/or a collection of banks 102a, 102b, 102c, 102d, 102e, 102f, 102g and 102h which are used to collect and store thermal energy from, for example, a solar thermal panel (not shown) and, for example, later deliver thermal energy to heat up cool water. Although FIG. 1 shows eight banks, the invention is intended to cover any suitable number of banks. Each of the banks 102a, 102b, 102c, 102d, 102e, 102f, 102g, 102h contains a different phase change material which therefore has a different melting point to store heat. As shown in FIG. 1, there is insulation 104 around the banks 102a, 102b, 102c, 102d, 102e, 102f, 102g102h. Bank 102a is at temperature of about 15° C. by virtue of containing a suitable phase change material with a phase transition temperature of 15° C. Similarly, bank 102b is at temperature of about 20° C., bank 102c is at temperature of about 25° C., bank 102d is at temperature of about 30° C., bank 102e is at temperature of about 35° C., bank 102f is at temperature of about 40° C., bank 102g is at temperature of about 45° C., bank 102h is at temperature of about 50° C. Although FIG. 1 shows specific temperatures, the present invention is intended to cover any selection of temperatures. As shown in FIG. 1 each of the banks in the energy storage system 100 contain heat exchangers 109a, 109b, 109c, 109d, 109e, 109f, 109g, 109h. Cold water is inserted from an inlet 106 into heat exchanger 109a and passes through heat exchangers 109b, 109c, 109d, 109e, 109f, 109g and 109h. Heated water may exit outlet 108 at about 45° C. Heat from, for example, a solar thermal panel 1110 and/or from the environment 1112 or other heat sources 1114 may be fed in from any of feed points 110 using heat exchange means 1116.

(13) In FIG. 1, the heat storage medium in each of banks 102a, 102b, 102c, 102d, 102e, 102f, 102g, 102h could be water (or some other heat storage medium), but preferably the heat storage medium is a suitable phase change material (PCM) A PCM is used for several reasons: The energy density of the PCM heat store (kWh stored per litre) will be much higher than for water; Large amounts of energy can be stored (melting) or extracted (freezing the PCM) within very narrow temperature bounds around the melting point—thus each bank can genuinely represent a specific temperature in a heating ladder; There is no reason to stick to cylindrical shapes typical for water tanks: the store can be a cuboid or any shape convenient to the application which means further density advantages.

(14) As long as over the whole storage cycle the different banks of the multi-bank PCM heat store are kept in equilibrium (i.e. as much heat is added to any given bank as is extracted from the same bank via water heating and incidental losses) it can at any given moment accept heat from any environmental heat source at any temperature from over 15° C. to over 50° C. (for the example in FIG. 1) and route it to the appropriate bank. For example when a solar panel is just warming up in the morning and it reaches 20° C., it can already start to load heat into the 15° C. bank of PCM material. At midday in bright sunlight when the solar panel's stagnation temperature could be over 100° C. the control system 2005 of the thermal store can choose an appropriate heat transfer fluid flow rate and bank into which to load heat, for instance: A low flow rate to take heat from the solar panel at 60° C. to load into the 50° C. bank; or A higher flow rate to take heat at 40° C. to load into the 35° C. bank.

(15) It should be noted also that heat transfer fluid that started at the solar panel at say 60° C. is, after it exits the heat exchanger in the 50° C. bank, still at or above 50° C. This can be routed now to load heat to the 45° C. bank, and so on down to the coolest bank. Thus heat transfer fluid can be made to return to the solar panel at around 15° C. in this example to be warmed again. So almost all the useful heat collected by the solar panel can be extracted and stored. Also the solar thermal panel itself will perform more efficiently, with lower thermal losses, by virtue of the low temperature of heat transfer fluid entering it.

(16) A further preferred embodiment is to nest the banks of PCM inside each other like Russian dolls. Such an energy storage system 200 is shown in FIG. 2 which has nested banks 202a, 202b, 202c, 202d, 202e, 202f, 202g, 202h. Bank 202a is at temperature of about 15° C., bank 202b is at temperature of about 20° C., bank 202c is at temperature of about 25° C., bank 202d is at temperature of about 30° C., bank 202e is at temperature of about 35° C., bank 202f is at temperature of about 40° C., bank 202g is at temperature of about 45° C., bank 202h is at temperature of about 50° C. (For clarity purposes insulation has been omitted from FIG. 2).

(17) The innermost bank 202h would be the hottest, with the outermost bank 202a the coolest. Of course there would still be maintained some insulation between each layer. In this case the loss of heat from each bank would be proportional to the much smaller ΔT between each bank and its outer neighbour.

(18) TABLE-US-00001 Bank ΔT Derived by (° C.) (° C.) (° C.) 55 5 55-50 50 5 50-45 45 5 45-40 40 5 40-35 35 5 35-30 30 5 30-25 25 5 25-20 20 5 20-15 15 −5  15-20

(19) By contrast, the embodiment of FIG. 1 separately insulates each bank from the local environment. If the insulation is of identical type and thickness around each bank then the higher temperature banks will lose more heat to their surroundings than the lower temperature ones, because heat loss is proportional to the ΔT between the bank and its surroundings.

(20) For a multi-bank PCM store inside a house, with surrounding temperature 20° C.:

(21) TABLE-US-00002 Bank ΔT Derived by (° C.) (° C.) (° C.) 55 35 55-20 50 30 50-20 45 25 45-20 40 20 40-20 35 15 35-20 30 10 30-20 25  5 25-20 20  0 20-20 15 −5 15-20

(22) The embodiment of FIG. 1, or a regular hot water tank, over time loses energy to the local environment. The nested multi-bank PCM heat store of FIG. 2 can, by suitable choice of outermost bank temperature to be equal to or lower than the local environment temperature, be made virtually neutral. For example in FIG. 2, if the local environment is at 20° C., the thermal store's outermost 15° C. layer will slowly absorb heat from the local environment.

(23) This means energy storage system 200 will store the heat put into it much better than energy storage system 100 (although over time the grade of heat it holds will reduce as heat flows from the high temperature core out to lower temperature banks around it). It will also be cool to the touch making it possible to integrate it into places one would not want to put a hot water tank.

(24) It should be noted that everything described so far can also apply in inverse for cold applications, with a coldest layer as the innermost bank, well below environmental temperature, and increasingly warm layers surrounding it, with the outermost layer the warmest at close to environmental temperature.

(25) We now refer to FIG. 3 which relates to an energy storage system 300. There are banks 302a, 302b, 302c, 302d, 302e, 302f. Bank 302c is preferably the largest bank as this is connected to an underfloor heating system 310 which has insulation 312 around its pipes where they pass through other banks 302a and 302b in the energy storage system 300. The energy storages system 300 contains an inlet 304 for mains cold water and heat exchangers 306 in each of the banks 302a, 302b, 302c, 302d, 302e, 302f. There is also an outlet 308 for hot water which also benefits from insulation 312 when it passes through banks 302e, 302d, 302c, 302b and 302a.

(26) We now refer to FIG. 4 which is a further energy storage system 400 according to the present invention. There is a multi-bank phase change material (MBPCM) heat store generally designated 410. There are a series of banks 402a, 402b, 402c, 402d, 402e, 402f connected with heat exchangers 404. There is also a cold water inlet 406 and a hot water outlet 408. The energy storage system 400 also has a heating loop 410 and a heating/cooling loop 412. There is also a multi-bank phase change material (MBPCM) cold store generally designated 420 which contains banks 422a, 422b, 422c, 422d. A heat pump 424 may be used to extract heat from selected banks (any of 422a, 422b, 422c, 422d) of cold store 420 and load it at higher temperatures into selected banks (any of 402a, 402b, 402c, 402d, 402e, 402f) of heat store 410 (for clarity purposes the heat exchangers to and from heat pump 424 have been omitted). Exiting from the cold store 420 there is a cooling loop 426 which is connected to a fan coil 428 which may blow cold air and/or may be connected at times when no heating is required to underfloor loop 412 to deliver comfort cooling.

(27) To generate cool for air-conditioning, heat can be removed from a bank of the PCM cool store using a heat pump and concentrated to a suitable higher temperature. This higher temperature heat could be released to the environment; however an alternative is to add it to a bank of a PCM heat store that needs additional heat.

(28) The highlighted path in FIG. 4 shows heat being removed from 10° C. bank 422b of cool store 420 via heat pump 424 and entering heat store 35° C. bank 402c. The benefit is high since this single use of a heat pump is both adding heat to the heat store 410 for later use (e.g. for hot water, space heating) and simultaneously (and with the same energy to drive the heat pump) removing heat from the cool store 420, thereby adding cool to it for later use (e.g. for air conditioning).

(29) It is not clear that there really need to be two distinct stores (one for heat and one for cold) as the ranges of useful temperature overlap. FIG. 5 therefore shows a further energy storage system 500 with a cold store 510 and heat store 512 joined together, having two centres, one hot and one cold and an outermost bank at or close to room temperature (assuming it will be housed inside a building's thermal envelope).

(30) In FIG. 6, a similar shared heat and cold store 600 is shown which has a single time-shared heat pump with many-to-many connectivity, connected on its input side to all except the hottest bank (the connection is multiplexed, i.e. a choice can be made of which cold source to draw upon) and on its output side connected by a multiplexed connection to all except the coldest bank.

(31) Most practical implementations of Multi-Bank PCM Heat/Cool Stores will need to re-balance the amount of heat stored between banks. Sometimes this will be possible purely by controlling the flow of heat from environmental sources to each bank; however it is likely that this will not always be possible.

(32) Furthermore, often some banks of PCM are required, for example for air conditioning, at below ambient temperature or below room temperature. A conveniently cold ambient source may not be available.

(33) A multi-bank PCM heat store could be configured with one or more heat pumps. These could be connected by heat exchangers, valves, etc in such a way that the heat pump(s) can pump heat from any bank to any warmer bank.

(34) Many practical implementations of heating and cooling systems using multi-bank phase change heat stores will likely include one or more heat pumps to provide a guaranteed way to lift heat from cooler to warmer.

(35) A heat pump can be time multiplexed to perform dual duty both as a bank to bank heat pump and also as an external heat pump as in practice, there will be occasions when it makes sense to transfer heat directly from colder to hotter banks of a thermal store, and others when it makes sense to remove heat to or extract heat from the surrounding environment. With suitable configuration of pipes and valves it is possible to allow for all these possibilities. In that case control algorithms can add this direct transfer to their repertoire and optimise for this as well, thus dynamically choosing it when appropriate. This is shown in FIG. 7 where energy storage system 700 has a heat pump 706 performing this dual duty. There is an environmental heat source 708. (For clarity purposes the insulation and some of the valves have been omitted).

(36) Instead of time-sharing or multiplexing a heat pump, an alternative is to interpose a lower capacity heat pump between each bank. This is illustrated in the energy storage system 800 shown in FIG. 8 which has a series of banks 802a, 802b, 802c, 802d, 802e, 802f, 802g, 802h, 802i, 802j between which are interposed heat pumps 804. (For clarity pipework, heat exchangers connecting heat pumps 804 to the banks and insulation are omitted). There is also an external heat pump 806 allowing heat to be drawn from an environmental source.

(37) An application of a heat & cool store for domestic heating, hot water and air conditioning from environmental heat sources using a shared heat pump is shown in FIG. 9. An energy storage system 900 comprises a series of banks where heated water or other heat transfer fluids may be used for a variety of purposes. Inlet 902 is used as a heating return; outlet 904 is used for underfloor heating; outlet 906 is used for fan-coil radiator flow; outlet 908 is used for radiator flow; inlet 912 is used for cold mains; outlet 910 is used for hot water; inlet 916 is used for air conditioning return and outlet 914 is used for air conditioning flow. Inlet 918 is an environmental heat source. Heat pump 920 may be used as a heat pump or by-passed if the environmental or solar heated water from a solar panel 922 is at a sufficiently high temperature. (The insulation has been omitted for clarity and multiplexing valves omitted for clarity. On the left-hand side of FIG. 9 flows are only shown and returns are omitted for clarity. Furthermore, pathways for cooling via night-time radiation from solar panel are omitted for clarity).

(38) Consider the case where environmental heat is loaded into an MBCPM Heat/Cool Store by using an External Heat Pump to raise the temperature at which heat is transferred from the environmental source to the Heat Store to above the temperature of the coldest bank of the Heat Store

(39) Instead of using a heat pump to directly move heat from a lower temperature environmental source, a thermal store could instead be configured with one or more additional (colder) banks of PCM that have temperatures lower than the environmental source. The heat from the environmental source can flow into these colder banks without initial heat pumping.

(40) Heat pumps interposed between each bank of the thermal store can be used to pump the heat so acquired to hotter banks; thereby making the heat useful and keeping the colder banks at a low enough temperature that they can continue to capture environmental heat thus eliminating the need for any external heat pumps.

(41) We can consider the example of an MBCPM system used to drive a radiator-based central heating system, where the primary heat source is a ground loop recovering low grade heat from the earth at 5° C.

(42) We refer to FIGS. 10 and 11 which represent energy storage systems 1000, 1100, respectively.

(43) In one case as shown in FIG. 10, there is an external heat pump 1004 that raises the heat of the ground water 1020 to 35° C.-50° C.+ in order that it can be loaded into the PCM banks 1002a, 1002b, 1002c, 1002d at 35, 40, 45, 50° C., respectively. The heated water is fed to radiator 1006. In FIG. 11, there are PCM banks 1102a, 1102b, 1102c, 1102d which have heat pumps 1104 interposed between each bank. The heated water is fed to radiator 1106.

(44) Bank 1102a, specially configured with PCM with melting point 0° C., is introduced. Heat is captured from ground water 1120 by passing this 5° C. fluid through heat exchange with the 0° C. bank 1102a. Later or simultaneously, this heat is pumped to the warmer banks using heat pumps 1104.

(45) It will be clear to those of skill in the art, that the above described embodiment of the present invention is merely exemplary and that various modifications and improvements thereto may be made without departing from the scope of the present invention. For example, any suitable type of phase change material may be used which can be used to store energy.