WO2006136860A1

WO2006136860A1 - Improved energy storage system

Info

Publication number: WO2006136860A1
Application number: PCT/GB2006/002349
Authority: WO
Inventors: Alton Bews Copland; Henry Stewart Warwick
Original assignee: Ice Energy (Scotland) Ltd
Priority date: 2005-06-23
Filing date: 2006-06-23
Publication date: 2006-12-28
Also published as: GB0512813D0; CA2613231A1; JP2008546980A; EP1941211A1; CN101278155A

Abstract

An system and a method is disclosed for improving the use of energy. In particular, a system is disclosed which is capable of improving the use of renewable energy by selective storage and extraction in the form of thermal energy. The thermal energy may be generated by capturing thermal energy from the sun or by converting electrical energy from a wind turbine. It is then stored within a fluid, which can be directed into ground loops in boreholes, in arrangements of underground loops, or in a tank filled with a volume of fluid. The thermal energy is thereafter used as required to drive a heat pump which in turn generates hot water.

Description

Improved Energy Storage System

The present invention relates to the field of energy efficiency, and in particular a system and method for improving the use of energy.

In February 2003, the UK Government issued an Energy White Paper in which the need for increased energy efficiency was outlined. In short, targets to reduce carbon emissions by significant amounts can only be met if at least 50% of the reductions are achieved through energy efficiency. This is therefore at the heart of UK energy policy. Reducing the demand on electricity supply networks will lead directly to a reduction in carbon emissions.

Another problem is the issue of fuel poverty, millions of households in the UK cannot afford to heat their homes sufficiently. Some heating systems are inefficient and expensive to run, and a cheaper, more energy efficient alternative is very desirable.

Energy from the sun is one of the most widely available energy sources, and one of the most obvious. Solar panels are used, primarily for generating electricity but also solar water heating panels are known. Solar water heating panels are used to provide hot water supplies.

The disadvantage of such solar water heating panels is that they do not always produce enough heat to provide, for example, a domestic hot water supply. There are periods, during the night and in cloudy conditions, when little or no energy will be produced and standard domestic water heating must be relied upon. Therefore it increases energy efficiency in a household only under appropriate conditions .

In light of recent heightened awareness of the need for more efficient use of energy, the benefits of using heat pumps are clear. A heat pump is a heat exchanger which transfers heat from one location to another location, effectively swapping hot for cold, or vice versa. A refrigerator is a heat pump, where the heat is taken out of the food storage area and dispersed through a sink on the rear of the appliance.

An alternative type of heat pump is used to harness the benefits of various kinds of renewable energy, in particular heat from ambient air, or underground warmth, or even from sunlight-heated water or ground. In this type of system, energy efficiency is increased significantly. A small amount of electricity is required to move heat energy from one location to another, but the energy transferred by the heat is generally several times the energy that would be generated by the electricity alone. This offers a way of boosting, for example, conventional water heating systems for homes and businesses. Given that 30% of CO2 emissions were attributed to heating buildings in 1997, it is clear that total emissions can be drastically reduced by employing more energy efficient practices.

However, conditions are not always such that heat pumps can be employed at optimal efficiency, given that the source of heat from which the energy is drawn may not always be at the optimum temperature for operation. Furthermore, weather conditions and the time of year also contribute to some extent to the efficiency of heat pumps.

It is therefore an object of the present invention to provide a system for more efficient use of energy.

Summary of Invention

According to a first aspect of the present invention, there is provided a system, the system comprising; an energy extraction means, the energy extraction means adapted to extract energy from a source; an energy storage means, the energy storage means adapted to retrievably store the extracted energy; an energy output means, the energy output means adapted to controllably release energy from the system; an energy transferring means, the energy transferring means adapted to transfer energy between the energy extraction means, the energy storage means, and the energy output means ; and an energy transfer controlling means, the energy transfer controlling means adapted to control the transfer of energy between the energy extraction means, the energy storage means, and the energy output means. Preferably the energy transfer controlling means operates so as to optimise the energy flow into the output means.

Preferably the energy storage system further comprises a heat pump, the heat pump located between the energy storage means and the energy output means .

Preferably the energy transferring means comprises at least one conduit connecting two or more of the components of the system.

Preferably the conduit is hollow and contains a fluid, the fluid adapted to store and to transfer heat energy by flowing therein.

Optionally the fluid is glycol.

Alternatively the fluid is water.

Preferably the energy extraction means comprises a solar heating panel, the solar heating panel adapted to receive energy from the sun and impart thermal energy to a fluid in the solar heating panel.

Preferably the energy extraction means further comprises a temperature sensor.

Alternatively the energy extraction means comprises one or more hoses filled with a fluid, the hose adapted to trap thermal energy from the surroundings . Alternatively the energy extraction means comprises a hose located within a tank containing a volume of fluid, the hose adapted to extract thermal energy from the volume of fluid.

Preferably the energy extraction means further comprises one or more heating elements located on or in the tank and adapted to provide thermal energy to the fluid.

Preferably the energy extraction means comprises a wind turbine adapted to provide electrical energy to the one or more heating elements. Preferably the energy storage means comprises one or more ground loops .

Preferably the one or more ground loops are inserted in respective boreholes.

Alternatively the energy storage means comprises a tank containing a volume of fluid.

Preferably the energy transfer controlling means comprises at least one valve, the at least one valve located within the system so as to control the flow of the fluid within the system.

Preferably the energy transfer controlling means further comprises a controller means, the controller means adapted to control the at least one valve in response to a temperature signal received from the temperature sensor. Preferably the energy output means comprises a cylinder, the cylinder adapted to receive and retain a quantity of fluid.

Preferably the cylinder comprises an output means, the output means adapted to selectively flow fluid into the system or into an external system.

Optionally the external system comprises a hot water system.

Alternatively the external system comprises a heating system.

According to a second aspect of the present invention, there is provided a cylinder adapted for use in the system of the first aspect, the cylinder comprising a first reservoir and a second reservoir, wherein the cylinder further comprises a means of diverting fluid from at least one of the energy extraction means and the energy storage means to either reservoir.

Preferably the cylinder is vented.

Alternatively the cylinder is unvented.

Preferably the first reservoir and the second reservoir are adapted to retain different quantities of fluid.

Preferably the first reservoir and the second reservoir are adapted to retain different temperatures of fluid. Preferably the first reservoir and of the second reservoir are adapted to receive fluid at different rates of flow.

According to a third aspect of the present invention, there is provided a method of storing and distributing energy employing the system of the first aspect, the method comprising the steps: measuring a temperature in the energy extraction means; and selectively moving energy from the energy extraction means to either the energy storage means or the energy output means or retaining the energy in the energy extraction means dependent on the temperature in the energy extraction means.

Preferably the energy is moved in the form of thermal energy within the system.

Preferably the thermal energy is stored in the fluid which flows in conduits connecting the components of the system.

Preferably a change in the movement of fluid in the system is dependent on the temperature of the fluid in the energy extraction means reaching a threshold value.

Alternatively a change in the movement of fluid in the system is dependent on the temperature of the energy extraction means reaching a threshold value.

Preferably the change in the flow of fluid is further dependent on the temperature of the fluid or the energy extraction means exceeding a threshold value for a predetermined period of time.

Preferably the step of moving energy from the energy extraction means to the energy storage means is selected in response to the temperature in the energy extraction means exceeding a first threshold temperature value.

Preferably the step of moving energy from the energy extraction means to the energy output means is selected in response to the temperature in the energy extraction means exceeding a second threshold temperature value, the second threshold temperature value being higher than the first threshold temperature value.

Preferably the step of moving energy from the energy extraction means to the energy output means is selected in response to the temperature in the energy extraction means exceeding a second threshold temperature value, the second threshold temperature value being lower than the first threshold temperature value.

Preferably the step of retaining the energy in the energy extraction means is selected in response to the temperature in the solar heating panel not exceeding the first threshold temperature value.

Preferably the step of retaining the energy in the energy extraction means comprises the additional step of flowing energy from the energy storage means to a heat pump.

According to a fourth aspect of the present invention there is provided at least one computer program comprising program instructions, which, when loaded into at least one computer, constitutes the energy transfer controlling means.

According to a fifth aspect of the present invention there is provided at least one computer program comprising program instructions, which, when loaded into at least one computer, cause the at least one computer to perform the method of according to the third aspect.

Preferably the computer programs are embodied on a recording medium or read-only memory, stored in at least one computer memory, or carried on an electrical carrier signal .

Brief Description of the Drawings

Aspects and advantages of the present invention will become apparent upon reading the following detailed description and upon reference to the following drawings in which:

Figure 1 presents a schematic view of an energy storage system in accordance with an aspect of the present invention; • Figure 2 presents a block diagram indicative of a mode of operation of the energy storage system in accordance with an aspect of the present invention; and

Figure 3 presents a schematic view of an alternative energy storage system in accordance with an aspect of the present invention. Specific Description

Referring initially to Figure 1, a schematic view of an energy storage system 1 is presented, to illustrate an embodiment of the present invention.

The system 1 comprises a control module 2, which governs the storage and transfer of thermal energy between the constituent components of the system 1.

A solar water heating panel 3 is provided, which comprises a tubing 4 containing water to be heated. The tubing 4 is arranged within the panel 3 in a serpentine fashion to increase the length and surface area of tubing 4, and hence amount of water, to be heated. Solar energy impinges on the panel 3 , which for exemplary purposes further comprises a blackened plate 5 in thermal contact with the tubing 4. The plate 5 heats up under the impinging solar energy, and in turn the heat is transferred to the water within the tubing 4.

When deployed in this way, heating of the water in the solar water heating panel 3 is effected by the thermal energy collected from sunlight. The sunlight heats up the panel 3 and as a result, thermal energy is transferred from the plate 5 to the water. The heated water can be pumped away and the thermal energy will be replaced by continued thermal energy received from the sun which will reheat the panel 3. As the water may be circulated, the thermal energy may be carried away from the solar panel to other parts of the system 1. A ground loop 6 is provided, in the form of a bore hole 7 with an inserted hose package 8 of an appropriate length. The hose package 8 extends to the bottom of the bore hole 7 where it loops to extend back up to the surface. It is envisaged that if necessary a larger length of hose could be accommodated by adopting a coiled, serpentine or helical hose in a shortened borehole. The borehole 7 will typically extend to between 60 and 100m in depth. This acts as a thermal energy storage device as the water, heated as described above, may be pumped to the ground loop 6 where it can reside underground. The ground loop 6 similarly comprises a ground loop input port 9 and a ground loop outlet port 10 formed at either end of the hose package 8.

A heat pump 11 is also provided, the heat pump 11 comprising a heat pump input port 12 and a heat pump output port 13. The heat pump input port 12 and output port 13 receive the heated water disposed from the solar panel 3 or from the borehole 7, and is connected to a hose system 14 between them both by means of an input hose 15 and an output hose 16. The hose system 14 joins the solar panel 3 and the ground loop 6 in the borehole 7, to which the input 15 and output hoses 16 of the heat pump 11 are connected. The thermal energy storing water can therefore be circulated amongst the components of the system 1.

The heat pump 11 is used to provide a heat exchanging mechanism whereby a house to which the system 1 is deployed may benefit from the thermal energy collected by the water in the system 1. The water within the system 1 has been warmed by solar thermal energy in the solar panel 3 , or by thermal energy transferred to or retained by the liquid in the borehole 7.

The heat exchange mechanism is well known. The warm liquid is used to heat up a refrigerant within the heat pump 11, which in turn evaporates. The heat pump 11 then compresses the refrigerant which results in an increase in the temperature of the refrigerant. This temperature increase is used to heat up water which is then transferred to the cylinder 17 or back into the borehole 7. In heating the water, the refrigerant condenses and is pumped back to be heated again by incoming water, thus completing the cycle. By way of example only, the heat pump 11 may generate three units of heat for each single unit of electricity powering the heat pump.

A first 18 and a second solenoid valve 19 are employed to control the flow of water within the system 1, to control whether the water flows into the borehole 7 or into the cylinder 17, for example. A "solar controller" 20 is provided which controls the operation of the valves 18,19 in response to the temperature of the solar water heating panel 3, as measured by the temperature sensor 21. A number of predetermined conditions, i.e. threshold temperature values, are set from which the "solar controller" 20 determines the optimum flow of water to optimise energy efficiency.

The cylinder 17 is analogous to a hot water tank within a conventional domestic environment, wherein water is heated and then stored in the cylinder 17, ready for use. The cylinder 17 is adapted to receive hot water from the heat pump 11, and also from the solar water heating panel 3 dependent on the position of the valves 18,19, and store each in a first and a second reservoir respectively.

In accordance with safety rules and regulations, a number of safety features (not shown) are also incorporated. A pressure relief valve, typically designed to relieve pressures in excess of 1.5 bar, is provided to prevent excess pressure build up in the hose system. Furthermore, a temperature relief valve, typically designed to relieve temperatures in excess of 100⁰C, is provided to prevent overheating of the system, and also prevents water of excessive temperatures being supplied through, for example, the plumbing system of a house.

An exemplary mode of operation will now be described in relation to the block diagram illustrated in Figure 2, and with further reference to Figure 1.

The values in the following description of operation are for indicative and relative purposes only and are not intended to be limiting.

The temperature of the solar water heating panel is constantly monitored 22 by the temperature sensor. The temperature of the water within may be directly determined from the temperature of the solar water heating panel.

When the temperature of the solar water heating panel is below 16°C 23, the solar water heating panel produces water at below 8⁰C, which will typically not increase the temperature of water stored in the ground loop and therefore the system does nothing 24.

When the temperature exceeds 16°C 23, but is below a second threshold value 25 of, say, 48°C, the solar water heating panel produces hot water up to a temperature of 30⁰C 26. This water is pumped directly into the ground loop 27.

It is worth noting that typically the temperature will have to remain above any threshold value for, say, 30 seconds before any action is performed as a result.

If the temperature exceeds 48°C 25, hot water is produced at temperatures of 42°C and above 28. This water is pumped directly to the cylinder 29.

In the meantime, domestic demand on the water cylinder may require hot water to be provided 30 in excess of the hot water currently produced directly by the solar water heating panel in which case the water from the ground loop is pumped to the heat pump 31. The heat pump generates hotter water which is then pumped to the cylinder 32, as long as demand continues.

Any means, preferably reliant on renewable sources, may be employed to extract energy from the surroundings. Furthermore, any means may be employed to store the energy.

Figure 3 illustrates a further embodiment of the present invention which employs a rotary turbine 34 as an alternative to the solar heating panel discussed in relation to Figure 1 above. The rotary turbine 34 is used to heat a fluid 35 within a tank 36 by means of three IkW immersion heating elements 37,38,39. The temperature of the fluid 35 within the tank is measured by a thermostat 40.

The size of the tank 36 will ideally be matched to the desired output of the heating elements. It is envisaged that the tank would be sized at around two thousand litres per kilowatt output of the heating elements 37,38,39.

The fluid 35 within the tank 36 is heated in a staged process. For example, when the rotary turbine 34 is being driven by a light wind, only the first heating element 37 is powered. As the wind increases in speed, the remaining heating elements, 38 then 39, are driven according to the electrical energy being provided by the rotary turbine 34. A de-stratification pump 41 is attached to the tank 36 in order to redistribute thermal energy in the fluid 35 and prevent stratified layers of temperature. This maximises the energy usage in the tank 36.

A tank hose 42 is arranged within the tank 36 in a serpentine fashion, and is used to extract thermal energy from the tank 36. A fluid within the tank hose 42, for example glycol, is circulated by a circulation pump 43 and thus moves thermal energy from the tank 36 (as generated and stored by means of fluid 35) to other parts of the system 33. Glycol is selected in this example as it has a low freezing point (preventing freezing in the winter) and a high boiling point (meaning it can work with high temperatures) , has favourable thermal conductivity (can transfer heat with its surroundings) and good specific heat capacity (can store thermal energy) . However any suitable fluid with similarly advantageous properties may be used.

Two ground loops 44,45 are provided, consisting of bore holes 46,47 each with a respective hose package 48,49 of appropriate length inserted. As above, the ground loops 44,45 act as thermal energy storage devices, and will (to continue the example above) be filled with glycol. A heat pump 50 is also provided, and receives heated glycol from either the tank hose 42 or from the boreholes 46,47. As described above, the thermal energy provided to the heat pump in this way allows the heat pump to generated heated water for an external system (not shown) such as an underfloor heating installation.

An arrangement of hoses join the heat pump 50, bore holes 46,47 and the tank in order to facilitate the movement of thermal energy (by means of the glycol within) amongst the parts of the system as required. Three motorised valves 51,52,53 (and a by-pass valve 54) determine the flow of thermal energy, and are controlled by a control module 55. The control module 55 also receives temperature information via the thermostat 40 in order to determine how the thermal energy in the system should be routed. In a particular example, the control module 55 monitors the temperature of the fluid 35 within the tank 36 to determine the most efficient way of using the thermal energy available to generate heated water to the external system.

When the temperature of the fluid 35 in the tank 36 is below, say, 10 ^aC, the heat pump 50 will operate normally and take thermal energy from the fluid in the ground loops 44,45 in order to generate hot water in accordance with the heat exchange mechanism described above.

When the temperature of the fluid 35 in the tank 36 is at a temperature of between, say, 10 ^SC and 20 ^aC, the heat pump 50 will use the thermal energy from the fluid 35 in the tank 36 via the glycol circulating in the tank hose 42 to generate hot water. Above 20 ^SC the thermal energy from the tank will be transferred to the ground loops 44,45.

It is also envisaged that the system 33 could be adapted to operate without the need for the ground loops 44,45. In fact, it is possible to operate the system 33 without these, instead using the fluid 35 within the tank 36 as the means of storing thermal energy (as well as generating that energy) . In this way the heat pump 50 could be connected solely to the tank hose 42 and still generate hot water for an external system.

An alternative to the ground loop in the borehole comprises a buried hose, for example a hose buried in the garden of a house in which the energy storage system is to be dfeployed. This hose is typically buried at a depth of approximately 1 m. The hose has two ends, which serve as an input port and an output port. Water is stored within the hose, which may be circulated. The solar energy stored in the ground may also be used to heat the water, in which case this type of ground loop may in fact, as an alternative, replace the solar panel.

It has been shown that the present invention provides a system and a relevant method for more efficient use of energy, in particular thermal energy used as a renewable energy source. In an exemplary embodiment, the system will heat water in a solar water heating plate to transfer to a hot water cylinder, but below a threshold temperature the heated water will be pumped into the ground loop. When required, the water from the ground loop can be pumped to the heat pump to generate heat which is transferred to a hot water cylinder.

The foregoing description of the invention has been presented for purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the precise form disclosed. The described embodiments were chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilise the invention in various embodiments and with various modifications as are suited to the particular use contemplated. Therefore, further modifications or improvements may be incorporated without departing from the scope of the invention as defined by the appended claims.

Claims

Claims ;

1. A system comprising; an energy extraction means, the energy extraction means adapted to extract energy from a source; an energy storage means, the energy storage means adapted to retrievably store the extracted energy; an energy output means , the energy output means adapted to controllably release energy from the system; an energy transferring means, the energy transferring means adapted to transfer energy between the energy extraction means, the energy storage means, and the energy output means; and an energy transfer controlling means, the energy transfer controlling means adapted to control the transfer of energy between the energy extraction means, the energy storage means, and the energy output means.

2. A system as defined by Claim 1 wherein the energy transfer controlling means operates so as to optimise the energy flow into the output means.

3. A system as defined by Claim 1 or Claim 2 wherein the energy storage system further comprises a heat pump, the heat pump located between the energy storage means and the energy output means .

4. A system as defined by any of Claims 1 to 3 wherein the energy transferring means comprises at least one conduit connecting two or more of the components of the system.

5. A system as defined by Claim 4 wherein the conduit is hollow and contains a fluid, the fluid adapted to store and to transfer heat energy by flowing therein.

6. A system as defined by Claim 5 wherein the fluid is glycol .

7. A system as defined by Claim 5 wherein the fluid is water.

8. A system as defined by any of Claims 1 to 7 wherein the energy extraction means comprises a solar heating panel, the solar heating panel adapted to receive energy from the sun and impart thermal energy to a fluid in the solar heating panel.

9. A system as defined by any of Claims 1 to 7 wherein the energy extraction means comprises one or more hoses filled with a fluid, the hose adapted to trap thermal energy from the surroundings.

10. A system as defined by any of Claims 1 to 7 wherein the energy extraction means comprises a hose located within a tank containing a volume of fluid, the hose adapted to extract thermal energy from the volume of fluid.

11. A system as defined by Claim 10 wherein the energy extraction means further comprises one or more heating elements located on or in the tank and adapted to provide thermal energy to the fluid.

12. A system as defined by Claim 11 wherein the energy extraction means comprises a wind turbine adapted to provide electrical energy to the .one or more heating elements .

13. A system as defined by any of Claims 1 to 12 wherein the energy extraction means ^• further comprises a temperature sensor .

14. A system as defined by any of Claims 1 to 13 wherein the energy storage means comprises one or more ground loops.

15. A system as defined by Claim 14 wherein the one or more ground loops are inserted in respective boreholes.

16. A system as defined by any of Claims 1 to 13 wherein the energy storage means comprises a tank containing a volume of fluid.

17. A system as defined by any of Claims 1 to 16 wherein the energy transfer controlling means comprises at least one valve, the at least one valve located within the system so as to control the flow of the fluid within the system.

18. A system as defined by Claim 17 wherein the energy transfer controlling means further comprises a controller means, the controller means adapted to control the at least one valve in response to a temperature signal received from the temperature sensor.

19. A system as defined by any of Claims 1 to 18 wherein the energy output means comprises a cylinder, the cylinder adapted to receive and retain a quantity of fluid.

20. A system as defined by Claim 19 wherein the cylinder comprises an output means, the output means adapted to selectively flow fluid into the system or into an external system.

21. A system as defined by any of Claims 1 to 20 wherein the external system comprises a hot water system.

22. A system as defined by any of Claims 1 to 20 wherein the external system comprises a heating system.

23. A cylinder adapted for use as the energy output means in a system as described in any of Claims 1 to 22, the cylinder comprising a first reservoir and a second reservoir, wherein the cylinder further comprises a means of diverting fluid from at least one of the energy extraction means and the energy storage means to either reservoir.

24. A cylinder as defined by Claim 23 wherein the cylinder is vented.

25. A cylinder as defined by Claim 23 wherein the cylinder is unvented.

26. A cylinder as defined by any of Claims 23 to 25 wherein the first reservoir and the second reservoir are adapted to retain different quantities of fluid.

27. A cylinder as defined by any of Claims 23 to 26 wherein the first reservoir and the second reservoir are adapted to retain different temperatures of fluid.

28. A cylinder as defined by any of Claims 23 to 27 wherein the first reservoir and of the second reservoir are adapted to receive fluid at different rates of flow.

29. A method of storing and distributing energy employing a system as described by any of Claims 1 to 22, the method comprising the steps of: (a) measuring a temperature in the energy extraction means; and (b) selectively moving energy from the energy extraction means to either the energy storage means or the energy output means or retaining the energy in the energy extraction means dependent on the temperature in the energy extraction means .

30. A method as defined by Claim 29 wherein the energy is moved in the form of thermal energy within the system.

31. A method as defined by Claim 29 or Claim 30 wherein the thermal energy is stored in the fluid which flows in conduits connecting the components of the system.

32. A method as defined by any of Claims 29 to 31 comprising the step of effecting a change in the movement of fluid in the system dependent on the temperature of the fluid in the energy extraction means reaching a threshold value.

33. A method as defined by any of Claims 29 to 31 comprising the step of effecting a change in the movement of fluid in the system dependent on the temperature of the energy extraction means reaching a threshold value.

34. A method as defined by Claim 32 or Claim 33 wherein the step of effecting a change in the flow of fluid is dependent on the temperature of the fluid or the energy extraction means exceeding a threshold value for a predetermined period of time.

35. A method as defined by any of Claims 29 to 34 comprising the step of moving energy from the energy extraction means to the energy storage means in response to the temperature in the energy extraction means exceeding a first threshold temperature value.

36. A method as defined by any of Claims 29 to 35 comprising the step of moving energy from the energy extraction means to the energy output means in response to the temperature in the energy extraction means exceeding a second threshold temperature value, the second threshold temperature value being higher than the first threshold temperature value.

37. A method as defined by any of Claims 29 to 35 comprising the step of moving energy from the energy extraction means to the energy output means in response to the temperature in the energy extraction means exceeding a second threshold temperature value, the second threshold temperature value being lower than the first threshold temperature value.

38. A method as defined by any of Claims 29 to 37 comprising the step of retaining the energy in the energy extraction means in response to the temperature in the solar heating panel not exceeding the first threshold temperature value .

39. A method as defined by any of Claims 29 to 38 wherein retaining the energy in the energy extraction means comprises the additional step of flowing energy from the energy storage means to a heat pump.

40. At least one computer program comprising program instructions, which, when loaded into at least one computer, constitutes the energy transfer controlling means of any of Claims 1 to 22.

41. At least one computer program comprising program instructions, which, when loaded into at least one computer, cause the at least one computer to perform the method of any of Claims 29 to 39.

42. At least one computer program according to Claim 41 embodied on a recording medium or read-only memory, stored in at least one computer memory, or carried on an electrical carrier signal.