AU2007251367A1

AU2007251367A1 - Method and apparatus

Info

Publication number: AU2007251367A1
Application number: AU2007251367A
Authority: AU
Inventors: Rune Midttun
Original assignee: RM ENERGY AS
Current assignee: RM-ENERGY AS
Priority date: 2006-05-11
Filing date: 2007-05-10
Publication date: 2007-11-22
Also published as: EP2069612A2; WO2007132183A2; CN101529056B; CN101529056A; NO20085152L; RU2008149082A; GB0609349D0; US20090293516A1; WO2007132183A3; JP2009536705A

Description

WO 2007/132183 PCT/GB2007/001709 METHOD AND APPARATUS This invention relates to a method of, and apparatus for, transferring energy. Energy transferring cycles are known in which a liquid 5 is vapourised by heat supplied to an evaporating device, the vapour so produced is employed to output energy, particularly to drive a vapour engine, such as a turbine, the vapour output from the turbine is condensed in a condensing device, and the liquid so produced is pumped back to the evaporating 10 device. Such systems are disclosed in, for example, BE-A 895,148; DE-A-3,445,785; GB-A-9160/1899; and GB-A-1535154. It is known for the circulated medium to take the form of a mixture of a liquid of low volatility and a liquid of high volatility and for the latter liquid to be condensed in 15 a condenser/absorber wherein the latter liquid is absorbed back into the liquid of low volatility. Examples of such a system are disclosed in EP-A-181,275; EP-A-328,103;

GB-A

294,882; JP-A-56-083,504; JP-A-56-132,410; JP-A-05-059,908; and US-A-5,007,240. 20 According to one aspect of the present invention there is provided a method of transferring energy, comprising causing a fluid substance to flow through a circuit and, in sequence, converting said substance from a liquid phase to a gaseous phase by inputting energy from a source and while 25 said substance is under relatively high pressure, and converting said substance from said gaseous phase to said liquid phase by outputting energy and while said substance is under relatively low pressure. According to another aspect of the present invention 30 there is provided apparatus for transferring energy, comprising a circuit, a displacing device arranged to displace a fluid substance around said circuit, an evaporating device in said circuit and arranged to convert said substance from a liquid phase to a gaseous phase by 35 inputting energy from a source, a condensing device in said 1 WO 2007/132183 PCT/GB2007/001709 circuit and arranged to convert said substance from said gaseous phase to said liquid phase by outputting energy, said displacing device comprising a pump arranged to act directly upon said liquid phase, said pump being downstream of said 5 condensing device and upstream of said evaporating device. Owing to the invention, it is possible to increase the proportion of total energy supplied which is available for use, in other words to reduce the proportion of the total energy supplied to the system which is lost in achieving the 10 transfer. Advantageously, the condensing device is in the form of a condenser/absorber having a sorbent of solid material-. This has an advantage over the systems using a medium mixture that the need to provide heat to split the mixture into vapour and 15 liquid is avoided. Furthermore, the present system can be relatively simplified by combining the condensing device with the evaporating device as a single assembly, preferably as a modular unit. 20 In order that the invention may be clearly and completely disclosed, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a diagram showing a prior art refrigeration system, 25 Figure 2 is a diagram of an embodiment of the system according to the present invention, Figure 3 is a diagram illustrating various applications of the system of Figure 2, Figure 4 is a diagram illustrating in detail a version 30 of the embodiment of Figure 2, and Figure 5 is a diagram illustrating in detail another version of the embodiment of Figure 2. Referring to Figure 1, the system comprises a sealed circuit 2 including a compressor 4, a condenser 6, an 35 expansion valve 8, and an evaporator 10, in series. The 2 WO 2007/132183 PCT/GB2007/001709 circuit 2 has a low pressure side 12 containing the evaporator 10 whereby thermal energy is input into the refrigerant, for example the substance R22 (a single hydrochlorofluorocarbon), and a high pressure side 14 5 containing the condenser 6 and whereby thermal energy is emitted from the refrigerant. A disadvantage of this system is that it requires a gaseous phase compressor 4 which requires a significant power input, as well as being bulky and expensive. In this prior art system, the compressor 4 10 increases the pressure of the gaseous phase refrigerant, whereafter the gaseous phase refrigerant is converted into the liquid phase in the condenser 6, from which thermal energy is emitted and the refrigerant arrives at the expansion valve 8 which has a cooling effect on the substance 15 owing to the pressure drop, causing conversion of the substance into partially gaseous phase and partially liquid phase. In the evaporator 10, the cold liquid substance receives thermal energy from the exterior and the substance is supplied to the compressor 4 in its gaseous phase. Thus, 20 the substance converts from its liquid phase to its gaseous phase under low pressure and converts from its gaseous phase to its liquid phase under high pressure. Referring to Figure 2, this system again includes a sealed circuit 20, but this contains a condenser/absorber 25 combination 22, a liquid pump 24, an evaporator 26, a superheater 28 and an energy-consuming device 30, which may be a turbine, a propeller, a piston-in-cylinder drive device, or a gas engine. Again, the circuit 20 has a low pressure side 32 and a high pressure side 34, but the substance is 30 converted from its liquid phase to its gaseous phase in the high pressure side 34 and from its gaseous phase to its liquid phase in the low pressure side 32. Setting aside losses, the heat input into the superheater 28, where the substance in vapour phase may receive thermal energy from the 35 ambient environment, is consumed by the device 30. The 3 WO 2007/132183 PCT/GB2007/001709 substance in the circuit 20 may be any suitable substance that has an evaporation temperature level at atmospheric pressure which is at least 30 0 C lower than the temperature of the ambient source supplying thermal energy to the 5 superheater 28. The ambient source may be air near the ground, or sea, lake or river water. Preferably, the evaporation temperature level is significantly lower than the temperature of the source, for example at least 5 0 C lower for water and at least 10C lower for air. Examples of such 10 substances are R22, carbon dioxide and nitrogen. An advantage of this system is that the liquid pump 24 which, correspondingly to the compressor 4, provides the motive power for driving the substance round the circuit, has a much lower power requirement than the compressor 4 and is 15 also more compact and inexpensive. Referring to Figure 3, this illustrates that the thermal energy input into the superheater 28 may be from ambient air, or ambient water, such as from a river or from the sea. In particular, the superheater 28 could replace the water cooler 20 of an air conditioning plant of a building, especially a large building such as an hotel. The Figure also illustrates that the energy-consuming device 30 may drive an electrical generator 38, a marine propeller 40, or replace the engine of a vehicle 42. The electrical generator 38 may be used to 25 supply the hotel 36, a house 44, and/or the pump 24. Referring to Figure 4, the condenser/absorber 22 comprises a shell 46 containing an absorbent 48 of solid material of a capillary nature, for example charcoal or coal powder, or nanotubes. Through the shell 46 and the absorbent 30 48 extends the evaporator 26 which is in the form of a coil 50. Thus the condenser/absorber 22 and the evaporator 26 constitute an assembly with only four inlets and outlets. The effect of the absorbent 48, which is in contact with the coil 50, is to reduce the saturation vapour pressure of the 35 substance entering the absorbent. Inside the coil 50, the 4 WO 2007/132183 PCT/GB2007/001709 vapour phase is created under a higher pressure than exists in the absorbent 48. Normally in a thermodynamic cycle, the condenser pressure is higher than the evaporator pressure, but, owing 5 to the use of the absorbent 48, in the system shown in Figure 4 the condenser pressure is lower than the evaporator pressure. The thermal energy released during condensing of the vapour in the absorbent 48 balances the heat requirement for the evaporator 26. The internal surface area of the coil 10 50 is a major factor in determining the mass flow of the vapour into the superheater 28. The superheater 28 transfers thermal energy into the substance in the circuit from, say, ambient air or water, because the temperature of the gaseous substance therein is lower than the ambient temperature. The 15 superheated vapour enters the turbine 30 through a pressure regulating, solenoid valve 52. The output vapour from the turbine 30, at low pressure, enters the condenser/absorber 22 for condensing and thus releasing thermal energy. The turbine 30 is used to drive the electrical generator 38 which may 20 drive a compressor 54 having a significantly lower power consumption than the power generation by the turbine 30, for example 10% to 15% of the power generated by the turbine. The compressor 54 creates in a liquid reservoir 56 the lowest pressure in the circuit 20. At the bottom of the shell 46 is 25 a flow connection 57 to the reservoir 56 for the liquid condensate. As the condensate leaves the absorbent 48, some of the liquid immediately evaporates and forms "flash" vapour, which is about 10% of the mass flow. The compressor 54 draws off from the reservoir 56 this "flash" vapour and, 30 by way of an auxiliary condenser 58 and an expansion valve 60, and with the aid of those items, converts the "flash" vapour into liquid condensate, which is delivered to the reservoir 56. A liquid pump 62 pumps the condensate in the reservoir 56 to the coil 50 via a non-return valve 64. The 35 pump 62 may be a gear or centrifugal pump. The compressor 54 5 WO 2007/132183 PCT/GB2007/001709 may be driven mechanically from the device 30, or electrically from the generator 38 or from an external power supply 66 by way of switches 68 and 70. A pressure-relief valve 72 bypasses the turbine 30 and the solenoid valve 52. 5 The version shown in Figure 5 differs from that of Figure 4 in a number of respects. Firstly, the auxiliary circuit 61, which is active particularly during start-up phases of the system, instead of containing the reservoir 56, includes an evaporator 74 inside the reservoir 56 and forming 10 a main super-cooler, so that the circuit 61 is totally separate from the circuit 20, with the- "flash"vapour being thereby condensed in the reservoir 56 itself. Moreover, the liquid is pumped by the pump 62 to the coil 50 via an auxiliary supercooler 76 in the reservoir 56, whereby the 15 heating of the liquid by the pump 62 is counteracted. Furthermore, the device 30 has an output gearbox and power shaft 78. Moreover, the low-pressure vapour output from the device 30 passes directly into the top of the shell 46 instead of via piping. 6

Claims

1. A method of transferring energy, comprising causing a fluid substance to flow through a circuit and, in sequence, converting said substance from a liquid phase 5 to a gaseous phase by inputting energy from a source and while said substance is under relatively high pressure, and converting said substance from said gaseous phase to said liquid phase by outputting energy and while said substance is under relatively low pressure. 10

2. A method according to claim 1, wherein said converting - of said substance from said gaseous phase to said liquid phase comprises reducing the saturation vapour pressure of said gaseous phase, and said converting of said substance from said gaseous phase to said liquid phase 15 comprises sorbing said gaseous phase utilising solid sorbent.

3. A method according to claim 1 or 2, wherein said substance has a transition temperature level between said liquid phase and said gaseous phase at atmospheric 20 pressure which is at least 5 0 C lower than the temperature of said source, which is ambient water.

4. A method according to claim 1 or 2, wherein said substance has a transition temperature level between said liquid phase and said gaseous phase at atmospheric 25 pressure which is at least 10 0 C lower than the temperature of said source, which is ambient air.

5. Apparatus for transferring energy, comprising a circuit, a displacing device arranged to displace a fluid substance around said circuit, an evaporating device in 30 said circuit and arranged to convert said substance from a liquid phase to a gaseous phase by inputting energy from a source, a condensing device in said circuit and arranged to convert said substance from said gaseous phase to said liquid phase by outputting energy, said 35 displacing device comprising a pump arranged to act 7 WO 2007/132183 PCT/GB2007/001709 directly upon said liquid phase, said pump being downstream of said condensing device and upstream of said evaporating device.

6. . Apparatus according to claim 5, wherein said condensing 5 device serves to reduce the saturation vapour pressure of said gaseous phase and comprises solid sorbent material for said gaseous phase.

7. Apparatus according to claim 6, wherein said condensing device is in contact with said evaporating device. 10

8. Apparatus according to claim 7, wherein said sorbent material -is in contact with said evaporating device.

9. Apparatus according to any one of claims 5 to 8, and further comprising, in said circuit, a superheating device for said gaseous phase downstream of said 15 evaporating device, and an energy-consuming device downstream of said superheating device, said condensing device being downstream of said energy-consuming device.

10. Apparatus according to claim 9, wherein said energy consuming device comprises a driving device. 20

11. Apparatus according to claim 10 and further comprising an auxiliary circuit including a gaseous-to-liquid phase-change device and serving to convert into said liquid phase said gaseous phase flowing from said condensing device. 25

12. Apparatus according to claim 11, wherein said auxiliary circuit is in fluid communication with the first mentioned circuit.

13. Apparatus according to claim 11, wherein said auxiliary circuit is out of fluid communication with the first 30 mentioned circuit.

14. Apparatus according to any one of claims 5 to 13, and further comprising a supercooling device downstream of said pump. 8