[001] The present invention relates to energy recovery apparatus used in conjunction with refrigeration, heating, ventilation and air-conditioning (HVAC) systems.

[002] Refrigeration, heating, ventilation and air- conditioning (HVAC) systems are used to both heat and cool local environments. They however require significant energy to drive them, and inevitably energy is lost in the processes used to heat, ventilate and air-condition. The present invention is in this respect directed towards recovering and harvesting the energy lost in such processes. [003] According to a first aspect of the present invention there is provided apparatus for use within a refrigeration system, said refrigeration system comprising a condenser, a compressor, an expansion valve, and an evaporator; said apparatus being used for recovering energy lost as a result of processes applied to refrigerant as it passes through the refrigeration system; said apparatus comprising a low grade energy collector provided at one or more of a) the condenser, b) between the condenser and the compressor, c) in a heat exchanger provided between outlets of the condenser and the evaporator, d) at the evaporator or e) any combination of a to d) . In this way, the apparatus seeks to harvest energy that would otherwise be lost and to thereby optimise the performance of the system. [004] Conveniently, the low grade energy collector comprises a thermoelectric element.

[005] Preferably, the low grade energy collector is provided at the condenser, the collector further comprising a thermoelectric element provided adjacent a refrigerant carrying passage.

[006] The low grade energy collector may comprise a sleeve element provided around said refrigerant carrying passage. The low grade energy collector may furthermore comprise a plate heat exchanger.

[007] Preferably, the low grade energy collector is provided between the compressor and the condenser, the low energy collector comprising a thermal store through which a refrigerant carrying passage connected between the compressor and the condenser is directed.

[008] Conveniently, the heat sink is provided with a thermoelectric element.

[009] The apparatus preferably further comprises an absorption chiller or desiccant dehumidifier coupled to said thermal store.

[0010] Preferably, a heat exchanger is provided between respective outlets of the condenser and the evaporator.

[0011] Conveniently, the heat exchanger comprises a thermoelectric element.

[0012] Preferably, heat energy from the relatively warm liquid refrigerant exiting the condenser is passed to the relatively cold gaseous refrigerant exiting the evaporator.

[0013] The low grade energy collector may be provided at the evaporator and comprises a means for collecting energy from an air flow with a space being conditioned. [0014] The means for collecting energy may comprise a heat exchanger having a thermoelectric element, said heat exchanger being supplied with air directed into said space and air exhausted from said space. [0015] The apparatus may further comprises a fan for directing said air flow.

[0016] Preferably, said means for collecting energy comprises a heat pipe having a thermoelectric element.

[0017] Conveniently, said means for collecting energy comprises a solar plate having a thermoelectric element, exhaust air from said space being directed onto said solar plate .

[0018] Illustrative embodiments of the present invention will now be described with reference to the accompanying drawings, in which: [0019] Figure 1 shows a first embodiment of the present invention with an energy recovery collector provided in a condenser;

[0020] Figure 2 shows a second embodiment of the present invention with an energy recovery collector provided between a compressor and condenser;

[0021] Figure 3 shows a third embodiment of the present invention with an energy recovery collector provided in a heat exchanger provided between outlets of a condenser and an evaporator;

[0022] Figure 4 shows a fourth embodiment of the present invention with an energy recovery collector provided adjacent an evaporator in a flat plate arrangement; [0023] Figure 5 shows a fifth embodiment of the present invention with an energy recovery collector provided adjacent an evaporator in a heat pipe arrangement; and

[0024] Figure 6 shows a sixth embodiment of the present invention with an energy recovery collector provided in solar plate arrangement. [0025] Figure 1 shows a HVAC system comprising a heat pump 1 which supports a typical vapour compression refrigeration cycle. The heat pump 1 comprises a compressor 2, a condenser 4, an expansion valve 6 and an evaporator 8. These four components are connected by fluid passages in the respective order forming parts of a cyclic thermodynamic structure to circulate a refrigerant around the heat pump 1. The fluid passages may be tubes, pipes and/or coils or any other suitable coupling between the elements of the heat pump 1. [0026] In a conventional refrigeration cycle, the refrigerant adopts different states as it goes through each of the four components. As indicated in the Figure 1, at A the refrigerant is in a gaseous state having a high temperature and a high pressure where hot gaseous refrigerant needs to be cooled before condensation. The gaseous refrigerant then enters the condenser 4.

[0027] The condenser 4 precipitates the high temperature and high pressure gas to a high temperature and a high pressure liquid by transferring heat to a lower temperature medium, such as ambient air. The refrigerant at B is in a liquid state having a high temperature and high pressure. During the refrigeration cycle, the refrigerant goes through a subcooling process at the condenser 4 or at stage B so that the refrigerant is changed to a complete liquid state. Subcooling involves cooling the refrigerant below its saturation temperature and forcing the refrigerant to change its phase completely. This allows the refrigerant to effectively undergo the remaining stages of the refrigeration cycle. The high temperature liquid refrigerant then enters the expansion valve 6.

[0028] In the expansion valve 6, the pressure decreases abruptly, causing a partial evaporation and an auto- refrigeration. When this happens at least some portion of the high temperature liquid turns into gaseous form. This mixture of gas and liquid refrigerant at C has a low temperature and a low pressure. Only a limited amount of the resulting refrigerant is allowed to flow into the evaporator 8.

[0029] The evaporator 8 then expands the refrigerant so that the refrigerant vapourises which results in cooling of the warm air from the space being refrigerated. The warm air may be blown by a fan (not shown) across the evaporator 8. The resulting superheated refrigerant at D then returns to the compressor 4, completing the refrigeration cycle.

[0030] Figure 1 shows apparatus in the form of a heat pump 1 according to a first embodiment of the present invention. As shown, the condenser 4 of the heat pump 1 has an inlet where the high temperature vapour refrigerant (A) enters. The condenser 4 further comprises a passage 20 which has an energy recovery unit 30 located at the passage 20. The refrigerant travels through the passage 20. The passage 20 may be coil and the energy recovery unit 30 may comprise a thermoelectric material 9 which is capable of handling low grade heat.

[0031] Operation of the first embodiment of the present invention will now be described. Figure 1 illustrates recovering energy which could have been lost whilst the refrigerant goes through the condenser 4. A superheated refrigerant enters the compressor 2 where the pressure increases. Then hot vapour refrigerant from the compressor 2 enters the condenser 4. By entering the phase of condensing and subcooling the excessive heat is removed from the gaseous refrigerant (A) by releasing the unnecessary heat into a lower temperature medium, such as the surrounding atmosphere. This creates a heat sink surrounding the passage 20 containing the refrigerant. The energy recovery unit 30 located at the passage 20 then recovers the low grade heat (waste heat) from the heat sink and converts the thermal energy into electricity by way of the thermoelectric material. This electricity is collected and channelled by electrical cabling (not shown) to be stored and/or to be used.

[0032] Figure 2 shows a heat pump 1 according to a second embodiment of the present invention. The heat pump 1 further comprises a thermal store 40. The thermal store 40 is filled with a suitable liquid such as water, and disposed between the compressor 2 and the condenser 4.

[0033] A thermoelectric module 41 is located at the walls of a thermal store 40. The module 41 may be provided in the form of a lining, provided around an inner surface of the thermal store. The thermoelectric lining is electrically coupled (not shown) to suitable electrical circuitry. The thermal store 40 may further be connected to an absorption chiller 42.

[0034] Operation of the second embodiment of the present invention will now be described. Water is stored in a tank like structure 40 and the refrigerant passage 34, at A is inserted into the thermal store 40. The refrigerant passage 34 may be a tube, pipe or coil which is made of thermal conductive material. The refrigerant at A is hot vapour with high pressure after absorbing heat at the evaporation and at the compression stages. By going through the passage 34 the low grade heat released from the refrigerant is absorbed by the water. The water is warmed by the thermal energy which would have otherwise been wasted in the ambient air.

[0035] This hot water can be used directly. Furthermore, the thermoelectric module 41 surrounding the hot water will convert the thermal energy into electricity. The heat rejected by the system can therefore be used to produce both hot water and electricity minimising energy loss.

[0036] If the hot water is not required, then the hot water can power an absorption/adsorption chiller 42 or desiccant dehumidifier which is coupled to the thermal store 40. The absorption chiller 42 is used to aid cooling. Therefore, the heat pump 1 enhances refrigeration by tri-generation to recover most of energy which may otherwise have lost and wasted to the ambient atmosphere.

[0037] Figure 3 shows a heat pump 1 according to a third embodiment of the present invention. As shown, the heat pump 1 further comprises a heat exchanger 50 which has a thermoelectric module 51 disposed within the heat exchanger 50. The heat exchanger 50 is placed between B where subcooled the liquid refrigerant flows and D where the superheated gaseous refrigerant flows. The heat exchanger 50 is configured so that the liquid refrigerant from B flows along the length of the passage within the heat exchanger 50 and the gaseous refrigerant from D enters from and leaves by the sides of the passage. The gaseous refrigerant flows in opposite direction from the liquid refrigerant. [0038] Operation of the third embodiment of the present invention will now be described. Heat exchanger 50 is placed between B and D where the refrigerant is most affected by the subcooling and superheating processes. The heat exchanger works because of the similarity of subcooling and superheating and the operation of the processes being inverse of each other. By allowing heat to flow from the refrigerant at a higher pressure (liquid at B) to the one with lower pressure (gas at D) an energetic equivalence can be created between the two processes. In general, the fluid being subcooled is hotter than the refrigerant being superheated. Therefore the energy flux is in the required direction and enables the energy exchange between the two processes by coupling the processes with an internal heat exchanger 50. [0039] By placing the thermoelectric module 51 within the heat exchanger 50, it is possible to convert the heat exchange between the subcooling and superheating into electricity . [0040] The thermoelectric heat exchanger 50 may comprise a thin or thick film and cooled by fluid.

[0041] Figure 4 shows a heat & refrigeration & air conditioning system 1 according to a fourth embodiment of the present invention. As shown in Figure 4, the system comprises a flat plate 60 adjacent to the space which is being air conditioned and as such adjacent the evaporator 8. In order to warm or cool the space, supply of fresh air and removal of the air from the space is required. This air flow is directed over the flow plate and its thermoelectric module 61 in order to generate electricity.

[0042] Figure 5 shows a fifth embodiment having a similar configuration to that of Figure 4, in this case with a heat pipe 70 having a thermoelectric module 71. [0043] Figure 6 shows a sixth embodiment, where the exhaust air is directed via a fan 83 past the evaporator 8 and across a solar plate 80 to boost the thermoelectric generation of module 81.

[0044] It will be understood that the described embodiments relate to preferred examples of the invention and that the present invention encompasses variants that fall within the scope of the appended claims.