Field of the Invention The present invention relates to thermodynamic power cycles and heat pump cycles, and to systems and apparatus for use in generating power and/or pumping heat. The invention relates In particular, but not exclusively to systems which create a refrigeration and/or heating effect with minimum energy waste,

Background to the Invention Air conditioning Is almost universally present in hotels, apartment blocks and other multi story bulldings around the world, The energy required to power such systems represents s significant cost.

Many such air conditioning plants operate on a standard vapour compression refrigeration cycle. A working fluid enters a compressor as a vapour, and is pumped to a condenser, where it loses heat and condenses to a liquid. The liquid working fluid Is forced through an expansion mechanism such as a throttle valve or a capillary tube, where It Is expanded and becomes a cold, liquid/vapour mixture. The liquid vapour mixture travels to an evaporator where it is heated to beoome a vapour, and then travels back to the condenser, The heat absorbed by the working fluid in the evaporator provides the desired cooling effect, In most large scale operations the evaporator is used to cool a heat transfer fluid, usually water based, which is then pumped to satellite heat exchangers in the areas which require cooling,

The heat absorbed by the condenser is also transferred to a heat transfer fluid, again typically water based, The heat absorbed is rejected to the environment by a cooling tower or other suitable heat rejection device. Rejection of heat to environment can be problematic, particularly where the difference in temperature between the heat transfer fluid and the ambient air is not great. Under these conditions large and sophisticated heat rejection devices may be required.

The performance of such air conditioning systems Is measured by dividing the rate of heat absorption by the evaporator by the power required to run the compressor. This ratio is called the Coefficient of Performance or COP.

Many refrigeration systems can be reversed, so that the condenser acts an evaporator, and the evaporator as a condenser, In this configuration the system can be used for heating, and may be referred to as a "heat pump". Whether a given system is referred to as a heat pump or a refrigeration system can be regarded as a matter of whether it is the heating aspect or the cooling aspect which is required, Accordingly the terms "heat pump", "refrigeration system" and "air conditioning system" are used interchangeably herein. In some oases the term "heat pump" is used where both the heating and the oooling effect of the system are useful.

Some refrigeration systems of the prior art use ejector pumps to provide at least a portion of the required compression of the working fluid. Ejector pump design will be well known to those skilled in the art, and Is described in a number of standard texts, for example, Perry's Chemical Engineer's Handbook, 8 ^th edition (ISBN 0-07-1422Θ4-3). Single stage ejector pumps are provided with a motive fluid inlet, a suction fluid Inlet and an outlet. In use a relatively high pressure fluid is introduced through the motive fluid inlet. The motive fluid is accelerated by a nozzle, thereby creating a low pressure zone, The suction fluid inlet is in fluid communication with the low pressure zone, and therefore fluid can be suoked into the ejector through the suction fluid inlet. The suction fluid and motive fluid are mixed and then flow through the outlet at a pressure whioh is higher than that of the suotlon fluid.

Most ejector pump designs are optimised to provide the greatest pressure at the output for a given motive fluid Input pressure. However, the range of pressures within which the ejector pump operates at maximum efficiency may be relatively narrow, In addition, the ejector pumps of the prior art may need to be manufactured to relatively dose tolerances to operate efficiently, increasing their cost of manufacture.

Another known way of heating fluids is through the use of a solar collector. Solar collectors are used for a number of applications. Relatively small units may be used to heat domestic hot water systems. Larger collectors may be used as the prime heating source for power generation systems, particularly those whioh use low boiling point working fluids. Examples of suoh systems include so called "Organic Ranklne Cycle" power generation systems,

Solar collectors of the prior art come in a variety of forms. One of the common solar collectors of the prior art use a copper tube arranged in a zig-zag pattern as the absorption element, Some embodiments cover the tube with specially coated glass, which reduces radiative energy loss from the collector. The glass used Is typically flat. Both the copper and the coated glass are high cost items, and so most solar collectors of the prior art are relatively expensive, A further disadvantage of the collectors of the prior art is that they only absorb sunlight at maximum efficiency for a small part of the day, due to the change in angle of the incident light from the sun from morning to evening.

Unless the context clearly requires, the terms "upstream", "downstream" and "between" are used herein to denote the position of a component in relation to the direction of flow of a fluid, for example the working fluid in a working fluid circuit.

The reference to any prior art in the specification is not, and should not be taken as, an acknowledgement or any form of suggestion that the prior art forms part of the common general knowledge in any country. Object of the Invention

It is an object of the invention to provide a heat pump and/or a combined air cooling and water heating system and/or a solar energy collection means which will overcome or ameliorate at least one problem such apparatus and/or systems at present, or which will at least provide the public with a useful choice, Other objects of the present invention may become apparent from the following description, which is given by way of example only.

Summary of the Invention

According to one aspect of the present invention there is provided a heat pump including a working fluid circuit provided with a first working fluid, the first working fluid circuit including a receiver, a pumping means for circulating the working fluid around the working fluid circuit when in use, and an ejector pump having a motive fluid inlet, a suction fluid inlet and an outlet, the working fluid circuit further including a first flow path between the receiver and the motive fluid inlet, the first flow path provided with a first heat exchange means for transferring heat from a first heat transfer fluid to the working fluid, thereby vaporising the working fluid in the first flow path, the working fluid circuit further including a second flow path between the receiver and the suction fluid inlet, the second flow path including a second heat exchange means adapted to transfer heat from a second heat transfer fluid to the working fluid and a working fluid expansion means upstream of the second heat exchange means adapted to reduce the temperature and pressure of the working fluid before the working fluid enters the second heat exchange means, the working fluid circuit further including a condenser adapted to transfer heat from the working fluid to a third heat transfer fluid, the condenser having an inlet in fluid communication with the outlet of the ejector pump and an outlet in fluid communication with the receiver. Preferably, the heat pump includes a second ejector pump having an outlet in fluid communication with the receiver, wherein the outlet of the first ejector pump is in fluid communication with a suction inlet of the second ejector pump, and the working fluid circuit includes a third flow path in parallel with the first and second flow paths and in fluid communication with a motive inlet to the second ejector pump, the third flow path including a third heat exchange means adapted to transfer heat from a third heat transfer fluid to the working fluid.

According to a second aspect of the present invention there is provided a heat pump including a working fluid circuit provided with a first working fluid, the first working fluid circuit including a receiver, a pumping means for circulating the working fluid around the working fluid circuit when in use, and an ejector pump having a motive fluid inlet, a plurality of suction fluid inlets and an outlet, the working fluid circuit further including a first flow path between the receiver and the motive fluid inlet, the first flow path provided with a first heat exchange means for transferring heat from a first heat transfer fluid to the working fluid, thereby vaporising the working fluid in the first flow path, the working fluid circuit further including a further flow path between the receiver and each said suction fluid inlet, the further flow paths including respective further heat exchange means adapted to transfer heat from a respective heat transfer fluid to the working fluid and respective working fluid expansion means upstream of the respective further heat exchange means adapted to reduce the temperature and pressure of the working fluid before the working fluid enters the further heat exchange means, the working fluid circuit further including a condenser adapted to transfer heat from the working fluid to a third heat transfer fluid, the third heat exchange means having an inlet in fluid communication with the outlet of the ejector pump and an outlet in fluid communication with the receiver.

Preferably, the pump is provided in the first flow path. . Preferably, the pump is provided between the receiver and the first and second flow paths. Preferably, the working fluid expansion means is a thermostatic valve. Preferably, the working fluid expansion means includes at least one capillary tube. Preferably, the working fluid leaves the working fluid expansion means as a saturated vapour.

Preferably, the working fluid circuit includes a second working fluid expansion means between the condenser and the receiver.

According to a third aspect of the present invention there is provided a heat pump of the first or second aspect wherein the working fluid circuit includes a turbine between the condenser and the receiver. According to a fourth aspect of the present invention there is provided a combined air cooling and hot water heating system including;

■ An air cooling system including at least one heat exchange means for transferring heat from air to be cooled to a heat transfer fluid, wherein the heat transfer fluid circulates around a closed heat transfer fluid circuit;

■ A fluid heating circuit including a heater;

■ A heat pump including an evaporator and a condenser, wherein the evaporator is in thermal contact with the heat transfer fluid and receives heat from the heat transfer fluid, and the condenser is in thermal contact with fluid in the fluid heating circuit, and transfers heat to the fluid in the fluid heating circuit before it enters the water heater.

Preferably, the heat pump is the heat pump of any one of the first, second or third aspects.

According to a fifth aspect of the present invention there is provided a solar energy collection means comprising an elongate outer member having a transparent convex cross-section portion and at least one inner member located within the outer member, the inner member provided with at least one passage therethrough to allow a fluid to flow through the inner member, wherein the transparent convex cross-section portion is shaped to focus Incident solar radiation towards the inner member.

Preferably, the convex cross-section portion is semi-circular. Preferably, the outer member is substantially circular in cross-section. Preferably, the inner member is provided with a plurality of passages therethrough.

Preferably, each said inner member has a first end provided with a first manifold means and a second end provided with a second manifold means.

Preferably, one of said manifold means has an inlet adapted to direct a fluid, in use, to one of said passages, and the other of said manifold means has an outlet, adapted to receive fluid, in use, from a different one of the passages.

Preferably, one of said manifold means is provided with an inlet means and an outlet means.

Preferably, said manifold means are adapted to direct fluid through each of the passages between the inlet and the outlet.

Preferably, the inner member is a substantially rectangular in cross-section. Preferably, the solar energy collection means includes a plurality of said inner members. Preferably, the solar energy collection means is provided with a fluid between said inner members and said outer members.

Preferably, the fluid Is a liquid.

Preferably the fluid is selected to provide a required refractive Index. Preferably, the refractive Index is selected to maximise incidence of solar rays onto the one or more inner members when in use.

According to a further aspect of the present invention there is provided a heat pump substantially as herein described with reference to any one or more of Figures 1 , 2, 3, 6, 7, or 8, 12, 12A, 13, 14 or 25. According to a still further aspect of the present invention there is provided a heat pump substantially as herein described with reference to any one or more of Figures 1, 2, 3, 6, 7, or 8, 13 or 25 in combination with an ejector substantially as herein described with reference to Figure 4.

According to a still further aspect of the present invention there is provided a heat pump substantially as herein described with reference to Figures 1 , 2, 3, 6, 7, or 8 in combination with a heat transfer fluid circuit substantially as herein described with reference to Figure 17, 18, 20, 21 or 25.

According to a still further aspect of the present invention there is provided a combined air cooling and water heating system substantially as herein described with reference to any one or more of Figures 9 to 16.

According to a still further aspect of the present invention there is provided a heat pump substantially as herein described with reference to any one or more of Figures 1, 2, 3, 6, 7, or 8, 12, 12A, 13, 14 or 25 in combination with a solar energy collector substantially as herein described with reference to Figure 22, 23 and 24. According to a still further aspect of the present invention there is provided a combined air cooling and water heating system substantially as herein described with reference to any one or more of Figures 9 to 16 in combination with a solar energy collector substantially as herein described with reference to Figure 22, 23 and 24,

According to a still further aspect of the present invention there is provided a power generation system substantially as herein described with reference to Figure 19.

According to a still further aspect of the present invention there is provided a power generation system substantially as herein described with reference to Figure 19 in combination with a heat pump system substantially as herein described with reference to any one or more of Figures 1 , 2, 3, 6, 7, or 8, 12, 12A, 13, 14 or 25,

The invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, in any or all combinations of two or more of said parts, elements or features, and where specific integers are mentioned herein which have known equivalents in the art to which the invention relates, such known equivalents are daemed to be incorporated herein as if individually set forth.

Further aspects of the invention, which should be considered in all its novel aspects, will become apparent from the following description given by way of example of possible embodiments of the invention.

Brief Description of the Figures Figure 1 is a schematic diagram of a heat pump system according to one embodiment of the invention.

Figure 2 is a schematic diagram of a heat pump system according to a second embodiment of the invention.

Figure 3 is a schematic diagram of a heat pump system according to a third embodiment of the invention.

Figure 4 is a diagrammatic longitudinal cross-section though an ejector according to an embodiment of the invention. Figure 5 is a diagrammatic longitudinal cross-section though an ejector according to another embodiment of the invention.

Figure 6 is a schematio diagram of a heat pump system according to a fourth embodiment of the invention.

Figure 7 is a schematic diagram of a heat pump system according to a fifth embodiment of the Invention.

Figure 8 is a schematic diagram of a heat pump system according to a sixth embodiment of the invention.

Figure 9 is a schematic diagram of a combined heating and cooling system according to an embodiment of the invention. Figure 10 is a schematic diagram of an intermediate heat transfer circuit between the heat transfer fluid circuit and tha haat pump. Figure 11 is a schematic diagram of an intermediate heat transfer circuit between the heat pump and the fluid heating circuit.

Figure 12 is a schematic diagram of a further embodiment of a heat pump. Figure 12A is a schematic diagram of a modified version of the heat pump of Figure 12, Figure 13 is a schematic diagram of a further embodiment of a heat pump, Figure 14 is a schematic diagram of a further embodiment of a heat pump. Figure 15 is a schematic diagram of another embodiment of the combined heating and cooling system.

Figure 16 is a schematic diagram of part of a heat pump circuit having a plurality of compressors arranged in a parallel flow configuration.

Figure 17 is a schematic diagram of a first heat transfer fluid circuit. Figure 18 is a schematic diagram of a second heat transfer fluid circuit. Figure 19 is a schematic diagram of a power generation circuit. Figure 20 is a schematic diagram of a third heat transfer fluid circuit. Figure 21 is a schematic diagram of a fourth heat transfer fluid circuit, Figure 22 is a very diagrammatic side view of a soiar collector of the present invention, Figure 23 is a very diagrammatic transverse cross-section through plane A-A. Figure 24 is a schematic diagram of a flow path through an inner member of the solar collector of Figure 22. Figure 25 Is a schematic diagram of a power generation system according to an embodiment of the invention,

Best Modes for Performing the Invention

Referring first to Figure 1 , a refrigeration system according to one embodiment of the present invention is generally referenced by arrow 1100. In the embodiment shown the system 1100 is configured for use with large scale air conditioning systems, for example as would be used in a hotel.

The system includes a closed working fluid circuit 1 , In which a suitable working fluid, for example R41 Oa, circulates. The working fluid circuit 1 is provided with a working fluid storage means 2, hereinafter referred to as a receiver, which stores a portion of the working fluid in the circuit,

The working fluid circuit further includes first and second parallel flow paths 3, 4, and pump 5 which is preferably positioned between the receiver 2 and the parallel flow paths 3, 4. The first parallel flow path 3 includes a first heat exchange means 7, The second parallel flow path 4 includes a working fluid expansion means 9 and a second heat exchange means 10.

An ejector pump 11 is in fluid communication with the first and second parallel flow paths 3, 4,

Ejector pump design will be well known to those skilled in the art, and is described in a number of standard texts, for example, Perry's Chemical Engineer's Handbook, 8 edition (ISBN 0-07- 142294-3), the relevant portions of which are included herein by reference. However, a preferred ejector pump design is described hereinbelow with reference to Figure 4.

The first parallel flow path 3 is connected to the motive fluid inlet 12 of the ejector pump 11. The second parallel flow path 4 is connected to the suction inlet 13 of the ejector pump 11. The ejector pump outlet 14 is in fluid communication with an inlet of a condenser 15. The outlet of the condenser 15 is connected to the receiver 2, thereby completing the working fluid circuit 1.

In use, R410a working fluid Is stored in the receiver 2 as a combination of liquid and vapour. Liquid working fluid, at a pressure of around 16 to 22 bar and a temperature of around 26-37°C flows out of the receiver 2 and is pumped along the first and second flow paths 3, 4 by the pump 5. The pump 5 adds a pressure differential of 10 to 14 bar. The working fluid leaves the pump 5 at a pressure of around 26-36 bar and flows though the first heat exchange means 7, where it absorbs heat from a first heat transfer fluid 16 and is vapourised. The source and nature of the first heat transfer fluid 16 may differ depending on the application of the system 1100, as is described further below. The working fluid in the second parallel flow path 4 moves through an expansions means, for example a thermostatic (Tx) valve 9, before entering the second heat exchange means 10. The Tx valve 9 reduces the temperature and pressure of the working fluid to around 0°C and 4.7 bar, at which point the working fluid is a saturated vapour. The saturated vapour then moves to the second heat exchange means 10 which acts as an evaporator, transferring heat from a second haat transfer fluid 17 to the working fluid, thereby superheating it. In some embodiments the evaporator 10 and vaporiser 7 may receive heat which has been rejected by one or more separate heat pump cycles.

The ejector pump 11 merges the working fluid from the second parallel flow path 4 into that of the first parallel flow path 3. The working fluid leaves the ejector pump 11 as a vapour. In the embodiment shown the working fluid leaving ths ejector is a superheated vapour. Some of the superheat is consumed during the compression process. The saturated vapour moves to the third heat exchange means 15, which acts as a condenser. The third heat exchange means transfers heat from the working fluid to a third heat transfer fluid 18.

The working fluid returns to the receiver from the condenser 15 as a slightly subcooled liquid. R134a may also be used as a working fluid, in which case the receiver is held at a pressure of around 5-6 bar. The pump 5 adds around 10 to 14 bar. The working fluid leaves the Tx valve 9 at around 1.8-2,2 bar and around 0°C.

Referring next to Figure 2, a second embodiment of the refrigeration system !s shown, with similar reference numerals referring to similar features as in Figure 1. The refrigeration system, generally referenced by arrow 1101, is provided with a first ejector 11, and first and second parallel flow paths 3, 4, in the same configuration as the system shown in Figure 1. However, rather than the working fluid flowing directly from the ejector outlet 14 to the condenser 15, the ejector outlet 14 is in fluid communication with the suction inlet 19 of a second ejector pump 20. The motive fluid inlet 21 of the seoond ejector pump 20 receives fluid from a third parallel flow path 22, .which is provided with a further heat exchange means 23 for adding heat to the working fluid. The second ejector pump 20 increases the pressure of the working fluid from the outlet of the first ejector pump 11 , thereby increasing the condensing temperature of the working fluid in the condenser 15.

The flow rates through the first, second and third parallel flow paths may be varied as required, but it is preferred that the flow rate through the second flow path 4 be much larger than the flow rate though the first and third flow paths 3, 22. In a preferred embodiment the flow rate through evaporator is around 6 times that of the flow through the motive parallel flow paths.

If even higher condenser pressures are required then a third ejector pump may be included between the second ejector pump 20 and the condenser 15, with a similar motive fluid feed as the first and second ejector pumps, The mass flow rate of the working fluid through the motive fluid paths is adjusted through the nozzle throat sizes to ensure that flashing to vapour occurs with the heat available. Figure 3 shows a further embodiment, generally referenced by arrow 1102, which is. a variation on the system shown in Figure 2.

In this embodiment a further ejector pump 24 is provided between the outlet 14 of the first ejector pump 11 and the inlet of the second ejector pump 20. The suction inlet 25 of the further ejector pump 24 receives the working fluid from the outlet 13, via a further heat exchanger 26 which adds further heat to the working fluid,

The motive fluid inlet 27 of the further ejector pump 24 receives working fluid from the first parallel flow path, in parallel with the inlet 12 of the first ejector 11.

In the embodiment shown in Figure 3 the pump 5 shown in Figures 1 and 2 has been replaced by separate pumps 5a, 5b and 5c in each of the first, second and third parallel flow paths 3, 4,

22. This configuration may be used in any embodiment of the invention, and may be useful in controlling the flow rates through each parallel flow path. However, a single pump may be used upstream of the parallel flow paths, as shown in Figures 1 or 2, or, in some embodiments (not shown) a pump may be used only in the first parallel flow path, which feeds the motive fluid inlet 11 of the first ejector.

Referring next to Figure A an ejector pump is shown, generally referenced by arrow 1200.

The ejector pump 1200 has a body 28 provided with a passage 29 between and inlet 30 and an outlet 31. The passage 29 is preferably substantially circular in transverse cross-section. The passage 29 has tapered section 32 which reduces in cross-section, a length of substantially constant cross-section 33 which acts as a mixing chamber, and an expanding diffuser section 34. The path between the inlet 30 and outlet 31 has a substantially straight centreline.

The ejector 1200 is further provided with a, nozzle 35. The nozzle 35 is positioned in the tapered section 32 facing the outlet 31 and is substantially coaxial with the tapered section 32. The nozzle 35 has a nozzle inlet 36 outside the passage 29. In a preferred embodiment the nozzle inlet 36 is provided on a side of the body 28, the nozzle 35 having a 90* bend to orientate the flow from the nozzle in the correct direction.

In use the nozzle inlet 36 is the motive fluid inlet. The motive fluid flowing out of the nozzle 35 creates a low pressure area in the tapered section 32 which draws fluid in through the inlet 30. The inlet 30 acts as the suction fluid inlet. Referring next to Figure 5, a two stage embodiment of the ejector of Figure 4 is shown, generally referenced by arrow 1201. The two stage ejector 1201 is created by connecting the outlet 31 of a first ejector unit 1120a directly to the inlet of a second ejector unit 1120b. Those skilled In the art will appreciate that any suitable number of ejector units may be oonneoted together in this way, as required.

Figure 6 shows a variation of the system of Figure 1 , generally referenced by arrow 1103. In this embodiment the ejector 11a is a three stage design in accordance with Figures 4 and 5. Three parallel flow paths 3a, 3b, 3c are provided to feed working fluid to the three motive fluid inlets 12a, 12b and 12c via three vaporiser heat exchangers 7a, 7b, 7c, Referring next to Figure 7, a high pressure version of the system shown in Figure 1 is generally referenced by arrow 1104. In this embodiment the TX valve has been replaced by a system of one or more capillary tubes 9a connected in a parallel flow configuration. This substitution may be used in any of the embodiments described herein, wherever thermostatic valves cannot be found which will operate at the required combination of pressure and flαwrate. The system 1104 further includes a further expansion device 37 between the condenser 15 and the receiver 2. This allows a high condensing pressure to be used without requiring a similarly high pressure receiver.

Referring next to Figure 8, a further variation of the working fluid circuit shown in Figure 1 is generally referenced 1105. The embodiment 1105 shown in Figure 7 differs from that shown fn Figures 1 in that a superheater 38 is provided. The superheater 38 is in fluid communication with the outlet 14 of the ejector pump 11. The superheater 38 receives the working fluid from the ejector pump 11 and heats it with a heat transfer fluid 39 which is heated by a heat source (not shown). The heat source is preferably a waste heat source, such as flue gas from an industrial boiler, In the embodiment shown the working fluid is heated to around 65°C inside the superheater 38, The superheated working fluid moves from the superheater 38 to a turbine/generator, referred to hereinafter as a turbine 40. The turbine 40 generates electrical power and cools the working fluid to slightly above its condensing temperature before it moves to the condenser 15, In this way, some or all of the electrical power necessary to run the pump 5 may be generated by the system, thereby increasing the Coefficient of Performance (COP) and reducing running costs.

To start the ejector based versions of the heat pump, it may be necessary to provide a compressor (not shown) between the outlet of the ejector and the Inlet to the condenser. The compressor may be used to assist in establishing a flow around the working fluid circuit during startup. Once the heat pump is operating normally the working fluid may be directed around the compressor,

Those skilled in the art will appreciate that the working fluid cycles described herein may be provided with other standard refrigeration components such as one way valves, filter/dryers and accumulators as required.

Referring next to Figure 9, a combined air cooling and hot water heating system is generally referenced by arrow 1300, The system illustrated is particularly suitable for use In hotels, apartment blocks or similar installations. The system 1300 includes a first closed heat transfer fluid circuit 41 , a heat pump, generally referenced by arrow 42, and a fluid heating circuit 43.

The heat transfer fluid circuit 41 includes at least one heat exchanger 44. The first heat exchanger 44 is preferably a so called "air to water" type of heat exchanger, although the heat transfer fluid circulating around the heat transfer fluid circuit 41 may be of any suitable type. In large installations many first heat exchangers 44 may be provided, in any suitable combination of series and/or parallel connection.

The first heat exchanger 44 transfers heat from the air to be cooled, for ©xamp.le air in an air conditioning duct, to the heat transfer fluid, thereby cooling the air and heating the heat transfer fluid. The heat pump 42 includes an evaporator 45 and a condenser 46, as well as other standard components such as are well know to those skilled in the art, The heat pump 42 may be of any suitable type, as is described further below, but in one embodiment is a standard vapour compression configuration, provided with one or more compressors 47 between the evaporator 45 and the condenser 46, and a working fluid expansion means such as a thermostatic valve 48 or a capillary tube between the condenser 46 and the evaporator 45.

The evaporator 45 is in thermal contact with the heat transfer fluid and transfers heat from the heat transfer fluid to the working fluid of the heat pump 42, thereby heating the working fluid and cooling the heat transfer fluid. The heat transfer fluid then returns to the first heat exchanger 44.

The thermal contact between the heat transfer fluid in the first heat transfer fluid circuit 41 and the refrigerant in the evaporator 45 is shown schematically in Figure θ, and may be achieved in a variety of ways. In some embodiments the heat transfer fluid may exchange heat directly with the refrigerant in the evaporator 45, as is shown schematically in Figure 9. However, in one embodiment, shown in Figure 10, a hoat exchanger 49 is provided in parallel with the heat transfer fluid circuit 41. A valve 50 may be opened to direct heat transfer fluid through the primary side of the heat exchanger 49, or closed to isolate the heat exchanger 49 from the heat transfer fluid circuit 41. A second valve 51 Is provided downstream of the heat exchanger 49. A pump 52 may ba provided to control the flow rate through the heat exchanger 49, Valves 50 and 51 also prevent reverse flow of heat transfer fluid 41 into heat exchanger 49.

A second heat transfer fluid circuit 53 connects the secondary side of the heat exchanger 49 with the evaporator 45. The second heat transfer fluid circuit 53 is provided with a pump 54. Typically the heat transfer fluid will be water based, with suitable anti-freeze and/or anti corrosion additives. A preferred heat transfer fluid is a mixture of water and an ethylene glycol additive such as Dowcal™, manufactured by the Dow Chemical Company,

By Isolating the first heat transfer fluid circuit 41 from the heat pump 42 in this way, a failure in one of the systems will not necessarily result, in the other being disabled.

Use of the second heat transfer fluid circuit 53 also allows the heat transfer from the first heat transfer fluid circuit 41 to the evaporator 45 to be optimised, Temperature sensors (not shown) sense the temperature of the fluid flowing into and out of each heat exchanger 49, 45 and a control means varies the speed of the pumps 52, 54 to optimise the heat transfer.

Referring back to Figure 9, the fluid heating circuit 43 is preferably a closed circuit filled with a liquid heat transfer fluid, for example water. Heat transfer fluid flows from a heater 55 such as a boiler, to a heat exchange means 56 which transfers heat from the heat transfer fluid to water in a hot water system 57. The heat exchange may be direct, or via an intermediate heat transfer circuit, such as that described with reference to Figures 10 and 11,

Heat from the condenser 46 is added to the heat transfer.fluid in the fluid heating circuit 43 between the heat exchange means 56 and the heater 55, to preheat the heat transfer fluid raturning to the heater 55. The heater 55 then raises the temperature of the heat transfer fluid to the required temperature, if it is not already within a required range already.

Additional cold "makeup" fluid 43a may be added to the system between the heat exchange means 56 and the condenser 46, if required.

The hot water system 57 receives water from a source 58, which flows to the heat exchange means 56, and then to the showers, basin, washing machines or other hot water requiring apparatus 57a, before being moved to a drain.

In an alternative embodiment (not shown) the fluid heating circuit may be an open circuit, with water flowing from a source, receiving heat from the condenser 46, then being heated by the heater 55, and moving to the hot water requiring apparatus and then the drain. As with the thermal contact between the first heat transfer fluid circuit 41 and the evaporator 45, and the thermal contact between the fluid heating circuit 43 and the hot water system 57, the thermal contact between the condenser 46 and fluid heating circuit 43 may be direct, or may involve a further heat transfer fluid circuit 59, as shown In Figure 11. The further heat transfer fluid circuit 59 may include a pump 60.

A further heat exchanger 61 is provided in parallel configuration with the fluid heating circuit 43, with valves 62 provided to isolate the further heat exchanger 61 if necessary. Fluid from the fluid heating circuit 43 flows through heat exchanger 61, and receives heat from the condenser 46, via the fluid in the further heat transfer fluid circuit 59. As with the system shown in Figure 10, temperature sensors (not shown) sense the temperature of the fluid flowing into and out of each heat exchanger 46, 61 and a control means varies the speed of the pumps 60, 63 to optimise the heat transfer.

White any suitable heat pump may be used as part of the present invention, a preferred embodiment of the heat pump 42 is shown in Figure 12. In the embodiment shown, the heat pump 42 is provided with a receiver 64 for storing hot liquid refrigerant, and an accumulator 65 downstream of the evaporator 45. The accumulator 65 fulfils the normal function of allowing any liquid refrigerant to flash to vapour before entering the compressor 47, In order to ensure that no refrigerant enters the compressor 47 in a liquid state, the heat pump 42 may be provided with a superheater 66. The superheater 66 is preferably a heat exchanger which heats the refrigerant working fluid vapour exiting the accumulator 65 by heat exchange with a suitable heating media. In the embodiment shown the heating media is liquid working fluid pumped from the receiver 64, The working fluid is returned to the receiver 64 after flowing through the superheater 66. In a preferred embodiment the system may be provided with means for controlling the flow of liquid refrigerant from the receiver 64 to the superheater, for example a variable speed pump 67, and/or means for bypassing a portion of the flow from the receiver 64 around the superheater 66.

The control means (not shown) may ensure that the temperature of the working fluid entering the compressor 47 is within a required range. In a preferred embodiment the working fluid may enter the compressor 47 at around 12°C. While it is important that the working fluid entering the compressor 47 is sufficiently high to ensure that the working fluid is in a vapour state, it may also be important to keep the temperature below a threshold maximum temperature in order to ensure that the compressor 47 is not damaged. The control means may monitor the temperature of the compressor casing(s) and adjust the temperature of the working fluid entering the compressor(s), for example by varying the heat added to the working fluid by the superheater 66.

Embodiments of the invention which use a compressor may suffer from problems associated with liquid entering the compressor at startup, To avoid this, one or more valves (not shown), for example a solenoid operated valve or a pneumatically aotuated valve, may be provided between the evaporator and the compressor. At startup, this valve may remain closed, thereby allowing the compressor to decrease the pressure in the manifold downstream of the evaporator, When the valve is opened, the low pressure established may assist in ensuring that all working fluid entering the compressor is in a vapour form. An accumulator or other similar device may also be used to assist in removing unwanted liquid droplets from the working fluid stream. In a preferred embodiment two such valves are provided in parallel, and opened sequentially.

In an alternative embodiment, shown in Figure 12A, the hot liquid working fluid flowing through the superheater 66 is sourced from the condenser outlet, and returns to the main working fluid circuit between the receiver 64 and thermostatic valve 48. This embodiment eliminates the • requirement for pump 67. Control of the flow of liquid working fluid through the superheater 66 is achieved with a bypass which be opened or closed. A small pressure dropper 16a may be provided between the condenser 46 and the receiver 64.

Referring back to Figure 12, the heat pump 42 may also be provided with an oil separator 68 which is adapted to remove any oil which has been introduced into the refrigerant by the compressor 47. Oil which has been removed from the refrigerant by the separator 68 is stored in a tank (not shown) and returned to the compressor 47 as required by a small pump (not shown). Those skilled in the art will be familiar with suitable oil separators. A filter may be used downstream of the oil separator in order to remove any residual oil from the working fluid. In some embodiments a plurality of compressors 47 may be used in parallel configuration, as is described in more detail hereinbelow.

A further optional feature of the heat pump 42 is the use of a second superheater heat exchanger 69 to add further heat to the refrigerant before it enters the condenser 46. The heat required to heat the superheater 69 may be provided by any suitable fluid, for example hot water from the hot water system 43.

If required, the heat pump 42 may be provided with a second evaporator and second thermostatic valve (not shown) in parallel connection with the evaporator 45 and thermostatic valve 48. The second evaporator and thermostatic valve may be switched into the circuit when the load on the heat pump 42 is high, and may operate simultaneously with the evaporator 45 and thermostatic valve 48. At lower loads a valve may be closed to prevent flow to the second evaporator and thermostatic valve. By controlling flow through the second evaporator and thermostatic valve In this way, incidences of liquid refrigerant entering the compressor(s) may b© minimised. Under some conditions the heat added to the fluid heating circuit 43 by the condenser 46 may be sufficient to raise the temperature of the water in the hot water system 57 to the required temperature without the use of the heater 45. In this case, if the heater 45 is a boiler, the boiler may be placed into a "low fire" mode, whereby the flow rate of fuel to the boiler is reduced to the minimum necessary to keep the boiler operational,

In one embodiment the second superheater heat exchanger 69 heats the working fluid with heat which is taken from the housing of the boiler while the boiler is in the "low fire" mode. In one example this may increase the temperature of the working fluid entering the condenser 46 from around 60°C to around 68°C. When the boiler is not in "low fire" mode, that is , the when the boiler is being used to heat the heat transfer fluid in the fluid heating circuit 43, the second superheater heat exchanger 6Θ may be thermally isolated from the boiler so that no heat is transferred to the working fluid.

Referring back to Figure 9, an important feature of the system described above is that heat absorbed from the air by the heat pump 42 can be extracted from the heat pump 42 without the use of a cooling tower or similar apparatus. The hot water system 67 absorbs all of this heat under normal operation. The heat added by the heater 55 Is varied depending on the temperature of the fluid at the inlet to the heater 55, in order to maintain a relatively constant temperature at the heater outlet. In some cases, where air conditioning loads are relatively high and water flows through the hot water system 57 are relatively low, the heater 55 may not need to add any further heat to the hot water,

In preferred embodiments of the combined heating and cooling system 1300 the heat pump 42 may be a heat pump as described hereinbefore. In the embodiment shown in Figure 13 the heat pump 42 is substantially as described with reference to Figure 1, with the evaporator 10 performing the function of evaporator 45, and condenser 15 performing the function of condenser 66.

The vaporiser 7 receives heat from any suitable heat source, for example the water which has been heated by the heater 55. The additional superheater 69 may be used if required, but is optional, Referring next to Figure 14, in some embodiments the heat pump 42 may be provided with an energy conversion means such as a turbine 74 between the compressor 47 and condenser 46. The turbine 74 may generate electricity, or it may be used to directly power one or more of the pumps jn the system, or both. The combined turbogenerator/pump described in International Application No.PCT/AUI 2008/000506 may be suitable, In embodiments which have an energy conversion means the superheater 69 i$ normally used to ensure that the working fluid has sufficient superheat for the turbine 74 to operate correctly.

In some embodiments (not shown), heat pump may also be provided an energy conversion means between the ejector and the condenser.

Referring back to Figure 9, in one embodiment the fluid in the first heat transfer circuit 41 is cooled from around 12X to around 6°C by the heat transfer to the evaporator 45.

The fluid in the fluid heating circuit leaves the heat exchange with the condenser 46 at around 60°C-65°C. The heater 55 increases the heat to between 70°C and 80°C, The heat exchange with the hot water system 57 reduces the temperature to around 52°C. The makeup fluid, when present, reduces the temperature to around 40-45°C.

Referring next to Figure 15, a further embodiment of the combined air cooling and hot water heating system is generally referenced by arrow 1301. In the embodiment 1301 shown in Figure 15 the heat transfer fluid circuit 41 is provided with a large capacity heat transfer fluid storage vessel, referred to hereinafter as a tank 75. A bypass conduit 76 is provided to allow the heat transfer fluid to bypass the tank 75 when a bypass valve 77 is closed.

The fluid heating circuit 43 is also provided with a large capacity heat transfer fluid storage ^' vessel, referred to hereinafter as a tank 78. The fluid heating circuit is also provided with a bypass 79 around the heat transfer fluid tank 78, and a bypass valve 80. The tanks 75, 78 provide thermal mass when the air cooling and fluid heating demands are mismatched.

If the demand for hot water is high, but the demand for cool air is relatively low, bypass valve 80 is closed and bypass valve 77 is opened. This brings tank 75 into the heat transfer fluid circuit 41. Since the tank 75 is large the temperature of the heat transfer fluid in the heat transfer fluid circuit 41 falls slowly in response to the heat being removed by the evaporator 45.

Similarly, if demand for air oooling capacity is high, while demand for hot water is relatively low, bypass valve 77 is closed and bypass valve 80 is opened, including tank 78 in the fluid heating circuit 43. In this way the temperature of the fluid in the fluid heating circuit rises slowly despite relatively little heat being rejected by the heat exchange means 46.

When the heating and cooling demand equalise, both bypass valves 77, 80 may be opened until the temperature in the tanks 75, 78 returns to its normal level, During this phase the heat pump 42 may be operated at a reduced output. After the temperatures return to normal the bypass valves 77, 80 may be closed, and the system 1301 runs as normal.

Those skilled in the art will appreciate that the required capacity of the tanks 75, 78 is determined by the specific heat capacity of the fluids in the circuits 41 , 43, the maximum allowable temperature variation of the fluids, and the maximum anticipated imbalance in the heat transfer rate between the cooling and heating sides of the apparatus.

Referring next to Figure 16, in some embodiments of the heat pump shown in Figures 12, 12a or 14 a plurality of compressors 47 are used in parallel configuration. Oil which is removed from the refrigerant by the separator 58 is stored in an oil storage tank 81. The oil from the tank 81 is distributed to each compressor 47 as required. In one embodiment oil is distributed to the compressors 47 by a common oil return conduit 82. Each compressor has an internal oil reservoir. A level switch (not shown) monitors the level of the oil in the internal reservoir and opens a valve to allow the reservoir to be "topped up" with oil from the oil return conduit 82 as required, Where more than one compressor 47 is used a control means (not shown) may determine how many of the available compressors are running at any given time, in order to provide a required flow of working fluid in the heat pump circuit 42. One or more of the compressors 47 may also be provided with variable speed drives which allow their speed to be varied, and the control means may vary the speed of the compressors in order to maximise the efficiency of the system.

In a preferred embodiment the compressors 47 are fed by an inlet manifold, generally referenced by arrow 83, which connects the main refrigerant line 84 from the evaporator 45 to the compressor inlets. The manifold 83 is provided with a plurality of runners 85, each of which extends between the main line 84 and a compressor 47. The runners 85 are preferably all substantially the same length, so that the pressure of the refrigerant at the inlet to each compressor 47 is substantially the same. Each runner 85 is preferably provided with a one way valve 86 to prevent the flow of refrigerant from reversing when one or more of the compressors 47 are not running. An outlet manifold, generally referenced by arrow 87, having substantially equal length runners 88 is preferably also provided between the compressor outlets and the main refrigerant line 89 to the condenser 46.

A number of options are possible for adding heat to the working fluid in the first and second heat exchange means, 7, 10 of the ejector based systems shown in Figures 1 to 8, and for removing heat from working fluid in the condenser 15 of those systems.

Figure 17 shows one embodiment of a heat transfer fluid circuit, generally referenced by arrow 1400. The heat transfer fluid circuit 1400 includes a first tank 93 for storing relatively hot heat transfer fluid and a second tank 94 for storing relatively cold heat transfer fluid. In the embodiment shown the heat transfer fluid is a glycol based fluid such as Dowcal™ 10, manufactured by the Dow Chemical Company- Heat transfer fluid from' ths hot tank 93 may be used as the first heat transfer fluid 16 to heat the working fluid In the first heat exchange means 7. The heat transfer fluid 16 returns from the first heat exchange means 7 to the hot tank 93. Heat transfer fluid from the cold tank 94 is used as the second heat transfer fluid 17, and is pumped to the second heat exchange means 10 by a suitable pump. The heat transfer fluid 17 returns to the cold tank 94.

Heat transfer fluid from the cold tank 94 is also used as the third heat transfer fluid 18, and is pumped to the condenser 15 by a pump. The third heat transfer fluid 18 is heated by the condenser 15, and then flows into the hot tank 93.

Cold heat transfer fluid from the cold tank 94 is also supplied to a heat load 95. The heat load may be any heat exchanger or group of hsat exchangers which require a refrigeration effect. For example, the heat load may Include one or more satellite heat exchangers which provide a refrigeration or air conditioning effect to a required area, The heat transfer fluid returns from the heat load to the cold tank 94, which is constantly being cooled by evaporator heat exchanger 10 and chilled water being recirculated to the bottom of the tank 93 from heat exchanger 7.

The heat transfer fluid in the hot tank 93 is also heated by exchange means 96. In some embodiments exchange means 96 may transfer heat from a further heat transfer fluid 97 which has been heated by a waste heat source, for example heat transfer fluid which has been used to cool the condenser of a separate air conditioning system. Both the hot and cold tanks are large in volume, for example around 30,00OL each in some large scale installations.

Referring next to Figure 19, another possible embodiment of a heat transfer circuit suitable for use with the working fluid circuits of Figures 1 to 3 or 6 to 8 is generally referenced by arrow 1401. Heat transfer fluid 98 from a heat load 95 enters a three port mixing valve 99. A portion of the flow, for example around one quarter, flows to the first heat exchange means 7, while the remainder flows to the second heat exchange means 10. The heat transfer fluid transfers heat to the working fluid in the first and second heat exchange means 7, 10, and then moves to a reservoir or tank 94a. Heat transfer fluid 98 is taken from the tank 94a to be heated by the heat load 95.

The working fluid in the third heat exchange means 15 is cooled by heat transfer fluid 98 from the tank 94a. The heat transfer fluid is then returned to the tank 94a.

As with the embodiment shown In Figure 17, the heat load 95 may be any heat exchanger or group of heat exchangers which require a refrigeration effect. For example, the heat load may include one or more satellite heat exchangers which provide a refrigeration or air conditioning effect to a required area. In embodiments where the present invention is being used as a supplement or support an existing air conditioning system, the heat transfer fluid 98 may be that used by the existing system to transfer heat between one or more satellite heat exchangers and the evaporator of the existing system. Referring next to Figure 19, a power generation system is generally referenced by arrow 1500.

The system 1500 is suitable for use in utilising heat rejected by air conditioning or heat pump systems, for example the system shown in Figure 1.

The power generation system 1500 includes a working fluid circuit 100 provided with a turbine 101, a condenser 102, a receiver 103, liquid pump 104 and boiler/vaporiser 105. Those skilled in the art will recognise this as a Rankine cycle. Those skilled in the art will also recognise other components which will enhance the running of the system, for example an oil separator 106 downstream of the turbine 101 , a filter dryer 107 downstream of the condenser 102 and a liquid separator 107a upstream of the turbine 101.

The working fluid is preferably a low temperature boiling point organic working fluid such as R134A.

Working fluid circuit is in fluid communication with a heat transfer fluid circuit 108, The fluid in the heat transfer fluid circuit 108 receives heat from the condenser 102 and then receives heat from the condenser 15 of a heat pump or refrigeration cycle. The heat transfer fluid is then further heated by a heat exchanger 10Θ before it transfers heat to the boiler/vaporiser 105. A pump 110 circulates the fluid. In some embodiments the flow rate through the pump 110 may be controlled to ensure that the temperature of the fluid entering the condenser 102 Ia maintained within a target range. A heat rejection device such as an air blast cooler 111 is provided to reject heat from the fluid before it enters the condenser 102.

The heat transferred to the circuit 108 may be obtained from any suitable source, but in a preferred embodiment it comes from a boiler 112 and is transferred to the heat exchanger 109 by a second heat transfer fluid circuit 113. The fluid returning from the heat exchanger 109 may reject heat to a suitable heat sink 114. The heat sink 114 may be a hotel hot water system, or a heat storage means.

A system for dealing with heat into and out of an air conditioning or heat pump system of the present invention, for example the system shown in Figure 1, is shown in Figure 20, and is generally referenced 1600.

In many embodiments the working fluid flowing though the second heat exchange means 10 is at a relatively low temperature, for example around 0°C, Accordingly, the second heat transfer fluid 17 is suitable for receiving heat from a relatively low temperature heat source 115. In many embodiments the heat source 115 may include a system for cooling air, for example as part as of an air conditioning system. In other embodiments, where cooling is not the primary purpose of the system, the heat source 115 may be heated by the environment, for example a volume of water which absorbs heat from the sun, as is described further below.

The working fluid flows through the condenser 15 at a relatively high temperature, for example around 65 °C, heating the third heat transfer fluid 18 to around 54°C. Accordingly, the third hsat transfer fluid 18 is suitable for providing a low temperature source of heat, or the condenser 15 may act to preheat the third heat exchange fluid 19 before it has further heat added from an additional source.

In the embodiment shown the third heat transfer fluid 18 flows from the condenser 15 to another heat exchange means 109, where it receives heat from a boiler 112. The third heat exchange fluid 1Θ, having been heated by heat exchange means 109 to a relatively high temperature, can be used to heat a high temperature heat sink 114, such as a hotel hot water system, or a heat storage means.

The working fluid in the first heat exchange means 7 is heated from a temperature of around 65°C to around 70°C. Accordingly, the first heat transfer fluid 16 enters the first heat exchange means 7 at a temperature of around 75°C and leaves at a temperature of around 66°C. A source of relatively high temperature heat is required to heat the first heat transfer fluid. In the embodiment shown the first heat transfer fluid 16 is heated by the boiler 112, optionally via a further heat exchange means 116, although in other embodiments an alternative source of heat may be used.

Those skilled in the art will appreciate that when used as a heating system, it is possible to extract more heat from the condenser 15 than is added to the system through the first heat exchanger 7, leading to a net saving in the energy required to provide heat to the heat sink 114 through use of the system. However, the overall efficiency of the system is maximised when the cooling effect on the heat source 115 is put to useful effect, for example to cool a controlled temperature space, or to replace or supplement an air conditioning system, Referring next to Figure 21 , a system for dealing with heat into and out of an air conditioning or heat pump system 1102 shown in Figure 3 is shown, and is generally referenced 1601,

A heat transfer fluid flows from the boiler 112 through the first heat exchange means 7 and further heat exchange means 23, thereby vapourising the working fluid in those heat exchange means. The cooled heat transfer fluid then moves to the high temperature heat sink 114, where further heat is transferred from the heat transfer fluid. From the high temperature heat sink 114 the heat transfer fluid moves though the condenser 15, where heat is transferred to the heat transfer fluid from the working fluid, thereby pre-heating the heat transfer fluid before it returns to the boiler 112 via a pump.

The second heat exchange means 10 receives heat from the second heat transfer fluid 17, in this embodiment the second heat transfer fluid moves around a closed loop which includes a tank 117, pump 118 and a solar energy collector 119. The solar energy collector 119 ensures that the second heat transfer fluid 17 is sufficiently warm to heat the working fluid travelling through the second heat exchange means 10 to a superheated vapour state. Similarly, heat exchange means 26 receives heat from a closed loop which includes a tank 119, pump 120 and solar energy collector 121.

Referring next to Figures 22 and 23, a solar energy collection means, referred to hereinafter as a "solar collector", is generally referenced by arrow 1700.

The solar collector 1700 comprises an elongate outer member 131 with an elongate inner member 132 provided within the outer member 131. The outer member 131 has a transparent convex cross- section 133 which, fn use, is orientated to allow incident sunlight to travel therethough. In some embodiments substantially the entire outer member 131 may be transparent, for example, in the embodiment shown in Figures 22 and 23 the outer member 131 may be a substantially transparent cylinder made from a suitable glass or plastic material.

The shape of transparent convex cross-section 133 Is selected to refract incident sunlight towards, and preferably onto, the inner member 132, The inner member 132 absorbs the energy from the incident sunlight. A number of arrangements are possible for the inner member, but In one embodiment the inner member 132 comprises at least one length of a suitable material, for example an aluminium extrusion 134, with at least one passage 135 therethough, In the embodiment shown in Figures 22 and 23, the inner member 132 consists of four lengths of substantially rectangular cross section aluminium extrusion 134, each having four passages 135 extending longitudinally therethrough. The extrusions 134 may be arranged to form a rectangular box section, as is beet seen in Figure 22. The centre of the box may be substantially collinear with the centra line of the outer member 131.

The sunlight which passes through the transparent section 133 falls on the inner member 132, heating the aluminium lengths, and thereby heating a heat transfer fluid 136 which is pumped through the passages 135.

Referring next to Figure 24, in one embodiment each extrusion 134 is provided with a manifold 137 at each opposing end 138. The manifolds 137 direct the heat transfer fluid 136 through the extrusion 134 in a series connection between an inlet 139 and an outlet 140, that is, so that all of the heat transfer fluid 136 flows through each passage 135. In this way the temperature of the heat transfer fluid 13Θ is maximised. The manifolds 137 may be separate components from the extrusion 134, or they may be integrally formed In the extrusion 134.

Referring back to Figure 23, in some embodiments the volume 141 between the inner member 132 and outer member 131 may contain a suitable gas such as air, or a vacuum. However, in other embodiments the volume between the inner member 132 and outer member 131 may be occupied by a suitable liquid 142. The liquid 142 may be selected to provide the required refraction of the Incident sunlight, in combination with the refraction provided by the transparent convex section 13, to maximise the amount of sunlight which falls on the inner member 132. In this way the outer member 131 and liquid may act in a similar way to a lens, focussing the sunlight onto the inner member 132. The focussing effect may be effective at a large range of incident sunlight angles.

Referring next to Figure 25, a power generation system suitable for use with the solar collector 1700 is generally referenced by arrow 1800, The power generation system is a variation of the system 1105 shown in Figure 8, however, theturbine 40 feeds a suction inlet of a second ejector 143. The motive Inlet of the second ejector 143 ia in fluid communication with the vaporiser heat exchanger 7, and the outlet of the second ejector 143 is in fluid communication with the condenser 15.

The power generation system further comprises a heat transfer fluid circuit carrying a suitable heat transfer fluid, for example water and/or Dowcal™, manufactured by the Dow Chemical Company.

The heat transfer fluid enters the solar collector 1700 at a temperature of around 27°C and leaves the collector at around 35°C. The water moves to the condenser 15 where it is heated from around 35°C to around 70°C by the working fluid in the condenser 15. From the condenser 15, the heat transfer fluid moves to the first heat exchanger 7, where it loses heat from around 70'C to around 65°C, the heat being transferred to the working fluid in the first heat exchanger 7, thereby vaporising the working fluid. From the vaporiser 7 the heat transfer fluid moves to a heat exchanger 144 which may be used to heat any suitable medium. In a preferred embodiment the heat exchanger 144 is used to heat hot water in a hot water system, The heat transfer fluid is cooled from around 65°C to around 55-60°C in the heat exchanger 144. The heat transfer fluid then moves to the second heat exchanger 10 where heat is transferred to the working fluid, cooling the heat transfer fluid to around 27-30'C. The heat transfer fluid then moves to the solar collector 1700 to complete the circuit.

In some embodiments which use a turbogenerator 40, the turbogenerator and pump 5 may be a combined, for example by using a combined turbogenerator pump such as that described in international application No. PCT/AU2008/000606,

Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise", "comprising", and the like, are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense, that is to say, in the sense of "including, but not limited to".

Where in the foregoing description, reference has been made to specific components or integers of the invention having known equivalents, then such equivalents are herein incorporated as if individually set forth.

Although this invention has been described by way of example and with reference to possible embodiments thereof, it is to be understood that modifications or improvements may be made thereto without departing from the spirit or scope of the Invention.