GB2549525A

GB2549525A - Power generating system

Info

Publication number: GB2549525A
Application number: GB1606989.0A
Authority: GB
Inventors: Geoffrey Nixon Robin
Original assignee: Individual
Current assignee: Individual
Priority date: 2016-04-21
Filing date: 2016-04-21
Publication date: 2017-10-25
Also published as: WO2017182809A1

Abstract

A power generating system 100 comprising a reservoir 110 for storing working fluid, a first heat exchanger 120, a second heat exchanger 130 and a power output 140. The second heat exchanger 130 transfers thermal energy from a heat source 160 to working fluid received in the second heat exchanger 130 from the first heat exchanger 120. The power output 140 is driven by expansion of working fluid in the second heat exchanger 130. The first heat exchanger 120 is configured to transfer thermal energy from working fluid received from the second heat exchanger 130 to working fluid received from the reservoir 110, to preheat the working fluid using waste heat from the system.

Description

Power Generating System

Technical Field

The present invention relates to a power generating system. In particular, but not exclusively, the present invention relates to a power generating system which employs a sustainable or renewable energy source.

Background

As the desire to reduce dependence on fossil fuels and levels of waste thermal energy increases, so innovation is required to achieve this. The Earth has an abundance of freely available thermal energy. Many industrial processes also produce waste thermal energy.

Conventional ground source heat pumps collect thermal energy from the ground, which is used, for example, for washing or heating purposes. Typically, these machines have a co-efficient performance of around 1/3 to 1/4, that is IKw of electrical energy input yields 3-4Kw of thermal energy output. These pumps use electricity and generate thermal energy.

There is therefore a need for systems that capture, or recapture, thermal energy and turn it into power, for example electrical power.

Summary

According to a first aspect of the present invention, there is provided a power generating system comprising a reservoir for storing working fluid, a first heat exchanger, a second heat exchanger and a power output, wherein the second heat exchanger is configured to transfer thermal energy from a heat source to working fluid received in the second heat exchanger from the first heat exchanger, wherein the power output is configured to be driven by expansion of working fluid in the second heat exchanger, and wherein the first heat exchanger is configured to transfer thermal energy from working fluid received in the first heat exchanger from the second heat exchanger to working fluid received in the first heat exchanger from the reservoir, such that working fluid received in the first heat exchanger from the reservoir reclaims thermal energy from working fluid received in the first heat exchanger from the second heat exchanger.

According to a second aspect of the present invention, there is provided a method of operating a power generating system, the system comprising a reservoir for storing working fluid, a first heat exchanger, a second heat exchanger and a power output, the method comprising configuring the second heat exchanger to transfer thermal energy from a heat source to working fluid received in the second heat exchanger from the first heat exchanger, configuring the power output to be driven by expansion of working fluid in the second heat exchanger and configuring the first heat exchanger to transfer thermal energy from working fluid received in the first heat exchanger from the second heat exchanger to working fluid received in the first heat exchanger from the reservoir, such that working fluid received in the first heat exchanger from the reservoir reclaims thermal energy from working fluid received in the first heat exchanger from the second heat exchanger.

According to a third aspect of the present invention, there is provided a computer program comprising a set of instructions, which, when executed by a processor, cause the processor to perform a method of controlling a power generating system, the system comprising a reservoir for storing working fluid, a first heat exchanger, a second heat exchanger and a power output, the method comprising controlling the second heat exchanger to transfer thermal energy from a heat source to working fluid received in the second heat exchanger from the first heat exchanger; controlling the power output to be driven by expansion of working fluid in the second heat exchanger; and controlling the first heat exchanger to transfer thermal energy from working fluid received in the first heat exchanger from the second heat exchanger to working fluid received in the first heat exchanger from the reservoir, such that working fluid received in the first heat exchanger from the reservoir reclaims thermal energy from working fluid received in the first heat exchanger from the second heat exchanger.

According to a fourth aspect of the present invention, there is provided a method of generating power comprising releasing a working fluid from a reservoir to a first heat exchanger; transferring thermal energy to the working fluid in a first heat exchanger; transferring thermal energy to the working fluid from a heat source, the transferring being conducted in a second heat exchanger; expanding the working fluid across a power output to generate power; converting energy used for the expanding in to an output energy; transferring thermal energy from the working fluid received in the first heat exchanger from the second heat exchanger to the working fluid received in the first heat exchanger from the reservoir, the transferring being conducted in the first heat exchanger; and returning the working fluid to the reservoir.

Further features and advantages of the invention will become apparent from the following description of preferred embodiments of the invention, given by way of example only, which is made with reference to the accompanying drawings.

Brief Description of the Drawings

Figure 1 shows a schematic representation of a power generating system according to embodiments of the invention;

Figure 2 shows a schematic representation of a power generating system according to embodiments of the invention;

Figure 3 shows a schematic representation of a power generating system according to embodiments of the invention; and

Figure 4 shows a schematic representation of a power generating system according to embodiments of the invention.

Detailed Description

Embodiments of the present invention comprise power generating systems, methods of generating power and methods of controlling power generating systems.

Embodiments of the present invention rely on at least one freely available, stable thermal energy source, referred to hereinafter as a heat source. The heat source may be any one of, but not limited to, a ground heat, waste heat from an industrial process, solar energy, an ambient air temperature and water. In Europe, the stable ground source at a depth of 2.3m is 10°C. In some geographical locations around the world, bodies of water e.g. oceans, lakes and reservoirs, maintain a near-constant temperature throughout the year. In other geographical locations air temperature remains consistently above a certain temperature. Many industrial processes are in constant or near-constant operation, often producing a constant amount of waste heat.

Embodiments of the present invention are conceived on the principle of expansion and contraction of a working fluid. In some embodiments, the system is for use with a working fluid that is a refrigerant. In an example, the working fluid has a boiling temperature below 0°C. In some examples, the working fluid has a boiling temperature between -40°C and -20°C. In some examples, the working fluid has a boiling temperature between -28.5°C and -27.5°C. In essence, the working fluid starts at a temperature that is lower than the ambient temperature of the system.

In some embodiments, the system is a closed system and is configured to cycle a fixed amount of working fluid.

Figure 1 shows a schematic representation of a power generating system according to embodiments of the invention. The system 100 comprises a reservoir 110, and first heat exchanger 120, a second heat exchanger 130 and a power output 140. The system 100 is configured to receive thermal energy in the second heat exchanger 130 from a heat source 160, as depicted by arrows 162.

The reservoir 110 is for storing working fluid. In some examples, the reservoir 110 is configured to store working fluid at a predetermined temperature. The predetermined temperature is lower than a temperature of the heat source 160. In some examples, the predetermined temperature is below the boiling temperature of the working fluid, such that working fluid is a liquid in the reservoir 110. In some embodiments, the predetermined temperature is below 0°C, or is between -40°C and -20°C, oris -28.5°C and -27.5°C.

In some embodiments, the reservoir 110 is configured to store working fluid in a vacuum or partial vacuum. In some embodiments, the reservoir 110 is positioned at the lowest point of the system 100.

In some embodiments, the system comprises a cooler 112. The cooler 112 is configured to maintain working fluid in the reservoir 110 at the predetermined temperature. In some embodiments, the cooler 112 is at least partially powered by a portion of power generated at the power output 140. In an embodiment, the cooler 112 requires less power to maintain the working fluid in the reservoir at the predetermined temperature than the power generated by the system 100 at the power output 140.

The reservoir 110 is configured to release working fluid from the reservoir 110, for example through an outlet (not shown) of the reservoir 110. The system 100 is configured to direct working fluid from the reservoir 110 to the first heat exchanger 120. Working fluid received in the first heat exchanger 120 from the reservoir 110 gains thermal energy as it progresses through the first heat exchanger 120, as will be described hereinafter.

In some embodiments, working fluid received in the first heat exchanger 120 from the reservoir 110 at least partially evaporates in the first heat exchanger 120, at least partially changing from a liquid state to a gaseous state. In some embodiments, the working fluid is at least partially a vapour in the first heat exchanger 120. In some embodiments, the vapour comprises a superheated vapour.

The second heat exchanger 130 is configured receive working fluid from the first heat exchanger 120. The working fluid received in the second heat exchanger 130 from the first heat exchanger 120 gained thermal energy in the first heat exchanger 120. The second heat exchanger 130 is further configured to receive thermal energy from a heat source 160, as depicted by arrows 162. In the second heat exchanger 130, thermal energy from the heat source 160 is transferred to working fluid received in the second heat exchanger 130 from the first heat exchanger 120. In some embodiments, the thermal energy from the heat source 160 and the working fluid received in the second heat exchanger 130 from the first heat exchanger 120 are thermally coupled.

It is the difference in temperature between the predetermined temperature of the reservoir 110 and the temperature of the heat source 160 that causes expansion of working fluid over the power output 140, which generates power. In an example, the predetermined temperature of working fluid in the reservoir is -28°C, and the heat source is at 10°C. The temperature difference of 38°C will cause working fluid to expand. The working fluid used will depend on the temperatures that the system 100 will be subjected to in its working environment. In some embodiments the working fluid will be chosen such that it is a gas at the temperature of the heat source.

In some embodiments, the second heat exchanger 130 comprises a first coil positioned inside a second coil (not shown). In a preferred embodiment, thermal energy is transferred from the second coil to the first coil.

The system 100 is configured such that working fluid exiting the second heat exchanger 130 expands across the power output 140. In some embodiments, the working fluid is in a high-pressure and gaseous state at the power output 140. The expansive power of the working fluid is then converted to a particular type of output energy. The type of output energy will depend on the application that the system 100 is used for. In some embodiments, the expansive power is converted into electromechanical energy. In some embodiments, the power output 140 comprises a turbine. In some embodiments, the system comprises a generator 150. In some examples the power is used to drive a generator 150. In other examples, the system is configured for connection to a generator, for example a generator that is already in-situ.

After expansion over the power output 140, working fluid is at a higher volume and lower pressure than the volume and pressure of working fluid before expansion over the power output 140. This difference in pressure causes a draw through the system as working fluid attempts to create equilibrium as per the second law of thermodynamics; thus, naturally drawing working fluid from the second heat exchanger 130 across the power output 140. Since the system 100 is configured to hold only a fixed amount of working fluid, working fluid cycles around the system 100. The design of the system 100 will dictate any loses in energy, for example, at bends in conduits that transport working fluid between components of the system 100.

In embodiments according to Figure 1, working fluid that has expanded via the power output 140 is received in the first heat exchanger 120 from the power output 140. Working fluid received in the first heat exchanger 120 from the power output 140 is at a higher temperature than working fluid received in the first heat exchanger 120 from the reservoir 110. Thus, at least some thermal energy in working fluid received in the first heat exchanger 120 from the power output 140 is reclaimed by working fluid received in the first heat exchanger 120 from the reservoir 110, as depicted by arrows 122.

In some embodiments, the first heat exchanger 120 is configured such that working fluid received in the first heat exchanger 120 from the power output 140 is thermally coupled to working fluid received in the first heat exchanger 120 from the reservoir 110.

In some embodiments, working fluid received in the first heat exchanger 120 from the power output 140 at least partially condenses in the first heat exchanger 120, at least partially changing from a gaseous state to a liquid state.

In some embodiments, working fluid that loses thermal energy in the first heat exchanger 120 is returned to the reservoir 110.

In some embodiments (not shown) a separate working fluid receives thermal energy from the heat source 160. In these embodiments, the second heat exchanger 130 is configured to receive the separate working fluid from the heat source 160, and is configured such that thermal energy is transferred from the separate working fluid to working fluid received in the second heat exchanger 130 from the first heat exchanger 110. In these embodiments, the separate working fluid loses thermal energy in the second heat exchanger 130, and is then returned to the heat source 160 to regain thermal energy. In some of these embodiments, the separate working fluid is returned to the heat source 160 via the first heat exchanger 120. In these embodiments, the first heat exchanger 120 is configured such that working fluid entering the first heat exchanger 120 from the reservoir 110 additionally reclaims at least a portion of the residual thermal energy in the separate working fluid.

Figure 2 shows a schematic representation of a power generating system according to embodiments of the invention. Some components in system 200 are the same as those in Figure 1 where reference numbers are the same, but increased by 100. Embodiments of the system 200 comprise a compressor 270. The compressor is positioned between the first heat exchanger 220 and the reservoir 210, and is configured to compress working fluid from which thermal energy is reclaimed in the first heat exchanger 220, such that it re-enters the reservoir 210 at the predetermined temperature.

In some embodiments, the compressor 270 is at least partially powered by a portion of power generated at the power output 240. In an embodiment, the compressor 270 requires less power to compress the working fluid than the power generated by the system 200 at the power output 240. In a still further embodiment, the combined power requirements of the compressor 270 and the cooler 212 are less than the power generated by the system 200 at the power output 240. In some embodiments, the compressor 270 compresses only working fluid that remains in a gaseous state when it reaches the compressor 270; working fluid that has already condensed to a liquid is directed directly to the reservoir 210 without being compressed.

In some embodiments, the system 200 is configured such that working fluid received in the first heat exchanger 220 from the reservoir 210 reclaims thermal energy produced by the compressor 270, as depicted by arrows 272. In this way, at least a portion of the waste thermal energy generated by the compressor 270 in compressing working fluid is recycled by the system 200 and used to heat working fluid exiting the reservoir 210.

In some embodiments, the compressor 270 comprises a dual pump and compressor. The dual pump and compressor is configured such that working fluid flows continuously around the system 200.

In addition, or alternatively to the compressor 270, the system 200 comprises an expansion valve 280. The expansion valve 280 is positioned between the reservoir 210 and the first heat exchanger 220. The system 200 is configured such that as working fluid exits the reservoir 210, it passes through the expansion valve 280 before entering the first heat exchanger 220. In some embodiments, working fluid at least partially changes from a liquid to a vapour as is passes through the expansion valve 280. In some embodiments the vapour comprises a superheat vapour. The expansion of working fluid at the expansion valve 280 can create a partial vacuum, which draws working fluid around the system 200.

In some embodiments, the system 200 additionally or alternatively comprises a second compressor 290. The second compressor 290 is configured to compress working fluid entering the first heat exchanger 220 from the power output 240, so it is returned to substantially the same volume at it was when it exited the first heat exchanger 220 and was directed to the second heat exchanger 230. Such a configuration allows the pressure on each side of the first heat exchanger 220 to be equal, thus promoting the transfer of thermal energy as the system 200 tries to maintain equilibrium.

Figure 3 shows a schematic representation of a power generating system according to embodiments of the invention. Where components are the same as those in Figure 1, reference numbers are the same, but increased by 200. The system 300 can be thought of as resembling a figure-of-eight configuration. The system 300 is configured such that working fluid that gains thermal energy in the second heat exchanger is directed in a first loop via the power output 340, over which it expands, heat source 360, where it gains thermal energy and back to the second heat exchanger 330, where is loses thermal energy. The working fluid that loses thermal energy in the second heat exchanger 330 is then directed in a second loop via the first heat exchanger 320, where is loses further thermal energy, the reservoir 310, the first heat exchanger 320, where is reclaims thermal energy, and back to the second heat exchanger 360, where gains thermal energy and thus starts the first loop again.

As described with reference to Figure 1, working fluid that gains thermal energy in the second heat exchanger 330 expands over the power output 340. In some embodiments, the expansive power drives a generator 350. The system 300 is configured such that working fluid that is expanded across the power output 340 is directed to the heat source 360.

The working fluid gains thermal energy from the heat source 360, and is then directed to the second heat exchanger 330.

In embodiments according to Figure 3, the second heat exchanger 330 is configured to receive working fluid from the heat source 360 and working fluid from the first heat exchanger 320. Working fluid from the heat source 360 has a higher thermal energy than working fluid from the first heat exchanger 320, such that, in the second heat exchanger 330, thermal energy is transferred from working fluid from the heat source 360 to working fluid from the first heat exchanger 320, as depicted by arrows 332.

In some embodiments, working fluid from the heat source 360 condenses in the second heat exchanger 330.

System 300 is configured such that working fluid that loses thermal energy in the second heat exchanger 330 is directed to the first heat exchanger 320. Working fluid received in the first heat exchanger 320 from the second heat exchanger 330 is at a higher temperature than working fluid received in the first heat exchanger 320 from the reservoir 310. Thus, at least some thermal energy in working fluid received in the first heat exchanger 320 from the second heat exchanger 330 is reclaimed by working fluid received in the first heat exchanger 320 from the reservoir 310, as depicted by arrows 322.

In some embodiments, working fluid is directed from the power output 340 to the heat source 360 via the first heat exchanger 330 (not shown). In these embodiments, the first heat exchanger 320 is configured such that working fluid entering the first heat exchanger 320 from the reservoir 310 additionally reclaims at least a portion of the residual thermal energy in the working fluid received in the first heat exchanger 320 from the power output 340.

Figure 4 shows a schematic representation of a power generating system according to embodiments of the invention. Some components in system 400 are the same as those in Figure 3 where reference numbers are the same, but increased by 100.

Embodiments of the system 400 comprise a compressor 470. The compressor is positioned between the first heat exchanger 420 and the reservoir 410, and is configured to compress working fluid received in the first heat exchanger 420 from the second heat exchanger 430, such that it re-enters the reservoir 410 at the predetermined temperature.

In some embodiments, the compressor 470 is at least partially powered by a portion of power generated at the power output 440. In an embodiment, the compressor 470 requires less power to compress the working fluid than the power generated by the system 400 at the power output 440. In a still further embodiment, the combined power requirements of the compressor 470 and the cooler 412 are less than the power generated by the system 400 at the power output 440. In some embodiments, the compressor 470 compresses only working fluid that remains in a gaseous state when it reaches the compressor 470; working fluid that has already condensed to a liquid is directed directly to the reservoir 410 without being compressed.

In some embodiments, the system 400 is configured such that working fluid received in the first heat exchanger 420 from the reservoir 410 reclaims thermal energy produced by the compressor 470, as depicted by arrows 472. In this way, at least a portion of the waste energy expended hy the compressor 470 in compressing working fluid is recycled by the system 400 and used to heat working fluid exiting the reservoir 410.

In some embodiments, the compressor 470 comprises a dual pump and compressor. The dual pump and compressor is configured such that working fluid flows continuously around the system 400.

In addition, or alternatively, the system 400 comprises an expansion valve (not shown). The system 400 can operate as described herein with reference to expansion valve 280 of Figure 2.

In addition, or alternatively, the system 400 comprises a second compressor (not shown). The second compressor is configured to compress working fluid entering the first heat exchanger 420 from the second heat exchanger 430, so it is returned to substantially the same volume as it was when it exited the first heat exchanger 420 and was directed to the second heat exchanger 430.

In each of the systems 100, 200, 300, 400, the first and second heat exchangers may be any suitable heat exchanger. In some embodiments, the first heat exchanger is the same type of heat exchanger as the second heat exchanger. In other embodiments, the first heat exchanger is a different type of heat exchanger than the second heat exchanger. The amount of heat exchange that occurs will depend upon how the system is engineered. A number of factors will influence the transfer of thermal energy in the heat exchangers, for example; the material, thickness and diameter of conduits for transporting working fluid, the pressure and the speed at which the system is configured to transport working fluid around the system and the interface between the “warmer” and “cooler” fluids in each heat exchanger.

Some embodiments comprise a method of operating a power generating system. The system may be any of the systems 100, 200, 300, 400 discussed herein with reference to Figures 1-4. In the description below, the reference numbers of Figure 2 are used, however it is to be understood that the systems 100, 300 and 400 are also suitable for embodiments according to this method.

In some embodiments, the method comprises configuring the second heat exchanger 230 to transfer thermal energy from a heat source 260 to working fluid received in the second heat exchanger 230 from the first heat exchanger 220. In these embodiments, the method comprises configuring the power output 240 to be driven by expansion of working fluid in the second heat exchanger 230 and configuring the first heat exchanger 220 to transfer thermal energy from working fluid received in the first heat exchanger 220 from the second heat exchanger 230 to working fluid received in the first heat exchanger 220 from the reservoir 210, such that working fluid received in the first heat exchanger 220 from the reservoir 210 reclaims thermal energy from working fluid received in the first heat exchanger 220 from the second heat exchanger 230. In these embodiments, working fluid received in the first heat exchanger 220 from the second heat exchanger 230 may be received directly from the second heat exchanger 230 (system 300, 200) or from the second heat exchanger 230 via the power output 240 (system 100, 200).

In some embodiments, where the system is system 200 or system 400 and comprises a compressor 270, 470, the method comprises configuring the system 200, 400 such that working fluid received in the first heat exchanger 220, 420 from the reservoir 210, 410 reclaims thermal energy produced by the compressor 270, 470.

Some embodiments comprise a computer program comprising a set of instructions, which, when executed by a processor, cause the processor to perform a method of controlling a power generating system. The system may be any of the systems 100, 200, 300, 400 discussed herein with reference to Figures 1-4. In the description below, the reference numbers of Figure 2 are used, however it is to be understood that the systems 100, 300 and 400 are also suitable for embodiments according to this method.

In some embodiments, the method comprises controlling the second heat exchanger 2303 to transfer thermal energy from a heat source 260 to working fluid received in the second heat exchanger 230 from the first heat exchanger 220, controlling the power output 240 to be driven by expansion of working fluid in the second heat exchanger 230 and controlling the first heat exchanger 220 to transfer thermal energy from working fluid received in the first heat exchanger 220 from the second heat exchanger 230 to working fluid received in the first heat exchanger 220 from the reservoir 210, such that working fluid received in the first heat exchanger 220 from the reservoir 210 reclaims thermal energy from working fluid received in the first heat exchanger 220 from the second heat exchanger 230.

In some embodiments, working fluid received in the first heat exchanger 220 from the second heat exchanger 230 is received directly from the second heat exchanger 230 (system 300, 200). In some embodiments, working fluid received in the first heat exchanger 220 from the second heat exchanger 230 is received from the second heat exchanger 230 via the power output 240 (system 100, 200).

Some embodiments comprise a method of generating power. The system may be any of the systems 100, 200, 300, 400 discussed herein with reference to Figures 1- 4. In the description below, the reference numbers of Figure 2 are used, however it is to be understood that the systems 100, 300 and 400 are also suitable for embodiments according to this method. The method comprises releasing a working fluid from a reservoir 210 to a first heat exchanger 220, transferring thermal energy to the working fluid in a first heat exchanger 220, transferring thermal energy to the working fluid from a heat source 260, the transferring being conducted in a second heat exchanger 230, expanding the working fluid across a power output 240 to generate power, converting energy used for the expanding in to an output energy, transferring thermal energy from the working fluid received in the first heat exchanger 220 from the second heat exchanger 230 to the working fluid received in the first heat exchanger 220 from the reservoir 210, the transferring being conducted in the first heat exchanger 220 and returning the working fluid to the reservoir 210.

In some embodiments, where the system is according to system 200 or system 400, the method comprises compressing the working fluid before returning the working fluid to the reservoir 210. In some of these embodiments, the method further comprises reclaiming thermal energy generated by the compressing into the working fluid released from the reservoir.

In some embodiments, the method comprises boiling the working fluid in the second heat exchanger 230. Expanding the working fluid from a lower volume, higher pressure to a higher volume, lower pressure generates energy across the power output 240.

In some embodiments, where the system is according to system 300 or 400, the method comprises re-heating the working fluid that expanded across the power output 340, 440 with thermal energy from a heat source 360, 460, and, in the second heat exchanger 330, 430, transferring heat from the working fluid heated by the heat source 360, 460 to the working fluid being heated in the second heat exchanger 330, 430.

Embodiments according to this method may comprise any of the additional features, or any combination of the additional features described herein.

As can be understood from this description, the present invention provides a power generating system that recycles thermal energy in the system that is not used to generate power across the power output. In such a way, the system can provide a constant and sustainable power output with input from a heat source or plurality of heat sources.

It is envisaged that the system be sold as a “white good” for households; fitted into new builds and retrofitted into existing properties. Households would then be able to produce energy, any surplus of which could be fed back to the National Grid. The system may for example provide enough power for a baseline electrical supply to one or more domestic households.

The above embodiments are to be understood as illustrative examples of the invention. Further embodiments of the invention are envisaged. For example, the system may be connected to a plurality of heat sources. It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the invention, which is defined in the accompanying claims.

Claims

1. A power generating system comprising: a reservoir for storing working fluid; a first heat exchanger; a second heat exchanger; and a power output, wherein the second heat exchanger is configured to transfer thermal energy from a heat source to working fluid received in the second heat exchanger from the first heat exchanger, wherein the power output is configured to be driven by expansion of working fluid in the second heat exchanger, and wherein the first heat exchanger is configured to transfer thermal energy from working fluid received in the first heat exchanger from the second heat exchanger to working fluid received in the first heat exchanger from the reservoir, such that working fluid received in the first heat exchanger from the reservoir reclaims thermal energy from working fluid received in the first heat exchanger from the second heat exchanger.

2. A system according to claim 1, wherein the first heat exchanger is configured such that working fluid from which thermal energy is reclaimed in the first heat exchanger re-enters the reservoir after exiting the first heat exchanger.

3. A system according to claim 1 or claim 2, wherein the system is configured such that working fluid received in the first heat exchanger from the reservoir at least partially changes from a liquid state to a gaseous state due to the reclamation of thermal energy from working fluid received in the first heat exchanger from the second heat exchanger.

4. A system according to any one of the preceding claims, wherein the system is configured such that working fluid received in the first heat exchanger from the second heat exchanger at least partially changes from a gaseous state to a liquid state due to thermal energy being reclaimed from working fluid received in the first heat exchanger from the second heat exchanger by working fluid received in the first heat exchanger from the reservoir.

5. A system according to any one of the preceding claims, wherein the first heat exchanger is configured such that working fluid received in the first heat exchanger from the reservoir is thermally coupled to working fluid received in the first heat exchanger from the second heat exchanger.

6. A system according to any one of claims 1 to 5, wherein the reservoir is configured to store working fluid at a predetermined temperature.

7. A system according to claim 6, wherein the reservoir is configured to store working fluid in a partial vacuum.

8. A system according to either claim 6 or claim 7, wherein the predetermined temperature is lower than a temperature of the heat source.

9. A system according to any one of claims 6 to 8, wherein the predetermined temperature is below 0°C.

10. A system according to any one of claims 6 to 9, wherein the predetermined temperature is between -40°C and -20°C.

11. A system according to any one of claims 6 to 10, wherein the predetermined temperature is between -28.5°C and -27.5°C.

12. A system according to any one of claims 6 to 11, wherein the system comprises a cooler configured to maintain working fluid in the reservoir at the predetermined temperature.

13. A system according to claim 12, wherein the cooler is at least partially powered by a portion of power generated at the power output.

14. A system according to claim 2 and any one of the claims 6 to 12, comprising a compressor configured to compress working fluid from which thermal energy is reclaimed in the first heat exchanger, such that it re-enters the reservoir at the predetermined temperature.

15. A system according to claim 14, wherein the compressor is at least partially powered by a portion of power generated at the power output.

16. A system according to claim 14 or claim 15, configured such working fluid received in the first heat exchanger from the reservoir reclaims thermal energy produced by the compressor.

17. A system according to any one of claims 14 to 16, wherein the compressor comprises a dual pump and compressor configured such that working fluid flows continuously around the system.

18. A system according to any one of claims 1 to 17, comprising an expansion valve between the reservoir and the first heat exchanger, the expansion valve configured to allow at least a portion of working fluid entering the first heat exchanger from the reservoir to expand to a vapour.

19. A system according to claim 18, wherein the vapour comprises a superheated vapour.

20. A system according to any one of the preceding claims, configured such that working fluid that has expanded via the power output is received in the first heat exchanger, and wherein the system is configured such that at least some thermal energy in working fluid received in the first heat exchanger from the power output is reclaimed by working fluid received in the first heat exchanger from the reservoir.

21. A system according to claim 20, configured such that separate working fluid receives thermal energy from the heat source, wherein the second heat exchanger is configured such that thermal energy is transferred from the separate working fluid to working fluid received in the second heat exchanger from the first heat exchanger.

22. A system according to claim 21, wherein the separate working fluid loses thermal energy in the second heat exchanger and returns to the heat source to regain thermal energy.

23. A system according to any one of claims 1 to 19, configured such that working fluid that has expanded via the power output is directed from the power output to the heat source such that the working fluid receives thermal energy from the heat source and the working fluid is then directed from the heat source to the second heat exchanger such that thermal energy is transferred from working fluid received in the second heat exchanger from the heat source to working fluid received in the second heat exchanger from the first heat exchanger.

24. A system according to claim 23, configured such that at least a portion of working fluid received in the second heat exchanger from the heat source condenses in the second heat exchanger.

25. A system according to either claim 23 or claim 24, configured such that working fluid received in the second heat exchanger from the heat source is directed to the first heat exchanger, and wherein the system is configured such that thermal energy in working fluid received in the first heat exchanger from the second heat exchanger is reclaimed by working fluid received in the first heat exchanger from the reservoir.

26. A system according to any one of the preceding claims, wherein the first heat exchanger comprises a first coil inside a second coil, and wherein the reclamation of thermal energy is from the second coil to the first coil.

27. A system according to any one of the preceding claims, comprising a working fluid.

28. A system according to claim 27, wherein the working fluid comprises a liquid when it is stored in the reservoir at the predetermined temperature.

29. A system according to either claim 27 or claim 28, wherein the working fluid comprises a refrigerant.

30. A system according to claim 29, wherein the heat source comprises one or more of: a ground heat; waste heat from an industrial process; solar energy; an ambient air temperature; and a water source.

31. A method of operating a power generating system, the system comprising: a reservoir for storing working fluid; a first heat exchanger; a second heat exchanger; and a power output, the method comprising: configuring the second heat exchanger to transfer thermal energy from a heat source to working fluid received in the second heat exchanger from the first heat exchanger; configuring the power output to be driven by expansion of working fluid in the second heat exchanger; and configuring the first heat exchanger to transfer thermal energy from working fluid received in the first heat exchanger from the second heat exchanger to working fluid received in the first heat exchanger from the reservoir, such that working fluid received in the first heat exchanger from the reservoir reclaims thermal energy from working fluid received in the first heat exchanger from the second heat exchanger.

32. A computer program comprising a set of instructions, which, when executed by a processor, cause the processor to perform a method of controlling a power generating system, the system comprising: a reservoir for storing working fluid; a first heat exchanger; a second heat exchanger; and a power output, the method comprising: controlling the second heat exchanger to transfer thermal energy from a heat source to working fluid received in the second heat exchanger from the first heat exchanger; controlling the power output to be driven by expansion of working fluid in the second heat exchanger; and controlling the first heat exchanger to transfer thermal energy from working fluid received in the first heat exchanger from the second heat exchanger to working fluid received in the first heat exchanger from the reservoir, such that working fluid received in the first heat exchanger from the reservoir reclaims thermal energy from working fluid received in the first heat exchanger from the second heat exchanger.

33. A method of generating power comprising: releasing a working fluid from a reservoir to a first heat exchanger; transferring thermal energy to the working fluid in a first heat exchanger; transferring thermal energy to the working fluid from a heat source, the transferring being conducted in a second heat exchanger; expanding the working fluid across a power output to generate power; converting energy used for the expanding in to an output energy; transferring thermal energy from the working fluid received in the first heat exchanger from the second heat exchanger to the working fluid received in the first heat exchanger from the reservoir, the transferring being conducted in the first heat exchanger; and returning the working fluid to the reservoir.

34. A method according to claim 33, comprising compressing the working fluid before returning the working fluid to the reservoir.

35. A method according to claim 34, comprising reclaiming thermal energy generated by the compressing in to the working fluid released from the reservoir.

36. A method according to any one of claims 33 to 35, comprising boiling the working fluid in the second heat exchanger.

37. A method according to any one of claims 33 to 36, comprising; re-heating the working fluid that expanded across the power output with thermal energy from a heat source; and in the second heat exchanger, transferring heat from the working fluid heated by the heat source to the working fluid being heated in the second heat exchanger.

38. Apparatus substantially in accordance with any of the examples as described herein with reference to and illustrated by the accompanying drawings.