A COOLING PLANT

Technical Field

The present invention relates to a cooling plant and more particularly is concerned with a cooling plant adapted 5 to operate at least partially on solar power.

Background Art

In the past cooling plants have been extensively used, 10 the common forms of plant being either of the vapour compression type or the absorption type. It has also been proposed to operate the plant by using solar power but for a practical arrangement it is almost certainly necessary to provide an auxiliary form of power for the system as a 15 back-up. when there is not an adequate supply of energy from a solar collection system. Solar energy is variable and intermittent and in practice it is necessary in most applications to provide a continuous cooling effect.

20 -Proposals have been made for a lithium bromide chiller system powered by a hot water circuit from a solar collector, with an auxiliary boiler to provide energy when there is insufficient solar power available. The major difficulties with such systems is the very high capital

25 cost. Indeed the disadvantage of many proposed solar powered systems is that their initial capital cost is so high that they are cost effective, if ever, in only a few circumstances. There is a major need for a cost effective solar powered system and the present invention is directed to providing a new and useful alternative to previous proposals.

Disclosure of the Invention

According to the invention, a cooling plant provides an absorption chiller system including a generator adapted to receive thermal energy from a supply, an evaporator connected in a fluid circuit to the generator and for cooling a working fluid from an external circuit, said evaporator having a cooling coil and means for connecting the coil to said external circuit which is adapted when in use to condense the refrigerant of a vapour compression type cooling system.

The invention may be embodied in various forms and one particular application is to air conditioning systems for buildings and the like although the invention also extends to other applications and uses.

When put into practical use, a cooling plant according to the invention will provide a plant in combination with a vapour compression system in which it is believed -that substantial cost advantages can be achieved. The cooling system according to the invention will condense the refrigerant and thereby reduce the working load on the compressor of the vapour compression system.

In a conventional system the compressor compresses the warmed gas returning from the zone to be cooled. The gas- .. passes through a condenser which is usually cooled by ambient air often with a forced draft and the compressed gas on cooling liquifies before being passed to the evaporator ^' unit in the' zone to be cooled wherein heat is absorbed from the zone and the gas vapourises. Condensing of the refrigerant at below ambient temperature can be an efficient manner of employing solar energy in substantially reducing the work necessary at the compressor to maintain the desired temperature in the zone to be chilled.

OMPI

The present invention extends to the combination of cooling plant and vapour compressor system in which either directly or indirectly the refrigerant of the vapour compressor system is condensed at below ambient temperature when in use. An indirect connection would be one in which a heat exchanger is used for condensing the refrigerant of the vapour compressor circuit using the cooled working fluid from the circuit associated with the cooling plant. A direct connection would be one in which the refrigerant of the vapour compressor is passed through connection lines to the evaporator of the cooling plant and returned to the zone to be cooled thus bypassing the normal condenser of the vapour compressor.

Furthermore _/ the invention extends to the combination of a solar collector, a cooling plant comprising an absorption system having a generator connected to the solar collector and an evaporator connected to a fluid chilling circuit for cooling the fluid therein, and a vapour compressor system connected so as to have its refrigerant condensed at below ambient temperature via the cooling fluid cooled in the cooling plant.

Preferably, the cooling plant according to the invention is embodied in a form comprising an energy store consisting of a storage zone for weak aqueous solution and a store for liquified gas derived at the generator by heating an initial strong solution in which the gas was absorbed.

Brief Description of the Drawings

For illustrative purposes only an embodiment of the invention will now be described with reference to the accompanying drawings of which:-

Figure 1 is a schematic diagram of an embodiment of the invention when arranged for use; and

Figure 2 is a view schematically illustrating an absorption chiller unit forming part of the system of Figure 1.

Best Mode of Carrying out the Invention

Referring first to Figure 1, there is provided a solar collector 10 connected in a circuit comprising a line 11 for supplying heated water to an absorption chiller unit 14 and a return line 12 for returning cooled water back through a pump 13 to the solar collector 10. The absorption chiller unit 14 is shown in more detail in Figure 2 and receives the hot water from the solar collector as an energy source The chiller unit condenses refrigerant which is discharged through line 15 which is connected to a conventional vapour compressor system 16 from which hot refrigerant for condensing is supplied through line 17.

The vapour compressor system 16, as is conventional, comprises a compressor 18, a condenser 19, an evaporator 20 and stop valves 21 and 22 which may be operated as required together with fans 23 and 24 for providing a forced air flow over the coils respectively of the evaporator 20 and the condenser 19 to facilitate heat exchange.

The compressor receives relatively cool refrigerant vapour from the evaporator 20 and compresses it thereby making it hot. The hot refrigerant vapour is passed through the condenser 19 and is cooled to a substantially ambient temperature by the draft from the fan 24. This drop in temperature causes the refrigerant to become a liquid which is passed to the evaporator 20. Heat is absorbed at the evaporator 20 in vapourising the refrigerant thereby cooling, in this case, a duct 25 of an air conditioning system in a building 26. ^'

In the embodiment illustrated, additional lines are provided for bypassing the condenser 19, these lines being connected to lines 15 and 17 as shown. Thus, the refrigerant can be condensed at below ambient temperature by being passed through an evaporator of an absorption chiller unit 14 and this causes the- compressor system 16 to have less load applied thereto in operation thereby saving energy.

Referring now to Figure 2, the chiller unit 14 will be described.

The chiller unit 14 includes a generator 27 having a coil through which the hot water is passed from the solar collector. The generator 27 also receives a slightly warm, strong ammonia working solution through line 28; the solution is sprayed into the generator and is heated significantly by the hot water from the solar collector thereby driving off ammonia vapour upwardly through line 29 and leaving depleted weak, hot solution which is discharged from the bottom of the generator through line 30 to a heat exchanger 31 from which heat in this solution is recaptured. The weak, cooled solution is then passed from the heat exchanger 31 into a solution store 32 which is provided essentially so that energy can be stored when the demand of the cooling system does not match the energy production from the solar collector. Thus the store 32 has cool, weak solution which may be pumped by pump 33 to the top of an absorber 34 for re-enrichment with hot ammonia gas supplied along line 36. The ammonia gas becomes absorbed in the weak, aqueous solution which passes through the coils of the absorber which are externally cooled by a forced draft from a fan 37, the resultant, strong cold solution then being passed along line 38 through a pump 39, through the heat exchanger 31 and back to the generator 28.

The ammonia gas produced by the generator has a small percentage .of water vapour entrained therewith and this is

separated from the ammonia at a rectifier 35 which also has coils cooled by the draft from the fan 37.

The water vapour becomes liquified and the water is returned by line 45 to the generator. At the top of the rectifier pure cooled ammonia vapour under high pressure is produced. This is passed to a condenser 40 also cooled by the draft from the fan 37, the condenser discharging liquid ammonia through line 41 to a refrigerant store 42 which contains liquid ammonia and thus provides a store of energy. On operation of the system, liquid ammonia is drawn from the store 42 and passed through an evaporator 434 which includes the coils of a refrigerant circuit 44. Refrigerant gas is passed along line 17 from the vapour compressor system shown in Figure 1 and the refrigerant liquifies in the condenser coil within the evaporator 43 and is discharged as a liquid that has been cooled below ambient temperature along line 15.

The liquid ammonia introduced into the evaporator 43 vapourises in cooling the liquid from the compressor circuit and is then discharged as hot ammonia gas along line 36 back to the absorber 34 described above.