SOLAR REFRIGERATIONSubmitted by: AMIT PRAJAPATI Presented by: ABOUT REFRIGERATION TYPES OF REFRIGERATION ABOUT SOLAR REFRIGERATION WORKING CYCLES - V.C.R CYCLE - V.A.R CYCLE - SOLID ABSORPTION CYCLE ADVANTAGES APPLICATIONS Refrigeration is the removal of heat from a space at a temperature lower than the surrounding temperature. In other word Refrigeration is the science of providing and maintaining temperature below that of surrounding atmosphere. Liquid Gases Refrigeration .There are many types of refrigeration like…. Vapour Refrigeration 5. Air Refrigeration 4. Evaporative Refrigeration 3. 1. Steam-jet Refrigeration 6. Ice Refrigeration 2. Solar Refrigeration 7. The solar energy is used for many purpose as Drying. . This Electrical energy we use in Refrigerator. In the solar refrigeration system we take a solar energy from sun and to convert solar energy into electrical energy. Melting in Addition to Heating & Cooling. Power Generation. gas. Solar energy needs no conversion & on the other hand. coal and Nuclear fuels. There are different methods of cooling using solar energy are represented on following block diagram. Solar energy may be collected either as heat or as electricity.……… . it helps to conserve non renewable energy sources like oil. . . The solar energy can be used either in VAPOUR COMPRESSION REFRIGERATION or VAPOUR ABSORPTION REFRIGERATION system. . . Solar energy could be converted directly into mechanical work for operating conventional compressor of a conventional vapour compression refrigeration system. The shaft work to the compression was provided by a steam turbine supplied with a steam which was generated by a steam generator placed at the focus of a large parabolic mirror. The COP of the system was found to be about 30% of the values for an idle system for the temperature values considered. not much work has been done in developing the rankine cycle for the use of vapour compression system. In this system cooling tower are not generally acceptable because of lack of water. There fore. Air cooled condensers are an alternative but the ambient temperature rises to 50’c and therefore the condenser designed becomes critical. Rankine cycle conversion of solar energy into mechanical power is more complex than absorption cycle directly driven by solar heat. . A small electric motor is mounted on the same shaft to provide stand by compressor power and to serve as a alternator when the compressor is idle but the sun is shining. . The refrigerant vapours are formed using the heat collected by solar concentrators and passed through a high speed turbines which runs a centrifugal compressor of the conventional refrigeration cycle. COP falls considerably as high compression ratio is essential to carry out the condensation above 50’c. . . CIRCUIT 1. This water is used for generating refrigerant vapour in the refrigerant boiler. . This provides the hot water which is collected from the solar collector. An auxiliary hot water boiler is provided to compensate the heat required when solar energy is not sufficient or not available due to cloudy sun or during rains. This circuit is used to generate mechanical power which is use to run the compressor of refrigeration circuit.CIRCUIT 2. This power generating circuit consist of generator. condenser and a pump. The vapour coming out at lower pressure from turbine is condensed in the condenser and pumped back to the refrigerant boiler. . The hot water from the collector is used to vaporise the organic fluid in the refrigerant generator. The vaporised fluid drives the turbine which drives the compressor of the refrigeration cycle. turbine. But the disadvantage is thermal effinciency is very poor.CIRCUIT 3. . An advantage of using refrigerant in the power cycle is low grad heat which can be used to generate the vapour…. This is conventional vapour compression refrigeration cycle which works on reversed rankine cycle. condenser. This circuit consist of compressor. expansion valve and evaporator. . Since we can convert solar energy more efficiently to heat than the mechanical or electrical energy the use of absorption refrigeration system with solar energy seem to be the best solution at present time. . A generator may be consider as a heat exchanger with heat transport liquid on one side and boiling two phase flow on the other. ammonia and water vapour are boiled off from the strong mixture in the upper part of the generator. .A generator contains an ammonia water mixture with strong concentration of refrigerant. In the generator. This vapour leaving the generator may contain from 5 to 10% of water vapour. The conveying of warm condensate from the condenser into the evaporator through throttling valve causes a reduction in refrigeration effect.there by the refrigeration effect by recovering heat which would otherwise be lost. . Therefore a heat exchanger is inserted between the storage and evaporator to decrease the temperature of the liquid refrigerant. The vapour coming out of generator is liquefied in the condenser and led to the refrigerant storage. . The absorber is considered as an indirect heat exchanger with cooling water flowing on one side and weak mixture flowing from the generator on the other side. The refrigerant which is at low temperature . low pressure is evaporated by absorbing the heat from the air or water which is circulated in the evaporator. This cooled air or water is further used either for refrigeration or air conditioning according to requirement. A pressure reduction valve between the generator and absorber reduces the pressure from high generator pressure to a lower one in the absorber. A liquid to liquid heat exchanger is used in the circuit in between absorber and generator which transfer energy from the weak hot liquid coming out from generator to the strong cooled liquid coming out of absorber. . . The basic philosophy behind the development of the cycle has been that the system should not be dependent on energy sources other than solar radiation and it should be simple so that there would be virtually no need for service or maintenance during the life time of the plant. it would be also desirable if the operation of the system is made fully automatic. in addition to this. . The solid absorption cycle is the answer to all the above mentioned requirement. A solid absorption cycle with NH3 as refrigerant and calcium chloride as the absorbent came out as the best solution for the requirements. . An intermittent absorption cycle is very well suited to the diurnal cycle of the sun. The pumps and blowers are also ruled out as well as no electrical control devices are required. The solid absorption cycle is based on the ability of metal halides to form complexes with certain gases. chloride of calcium is well suited. . especially NH3. For condensing temperature of 40*c the dotted lines to the right indicate equilibrium deabsorption temperature of 94*c & 106*c respectively. It absorbs 8 moles of NH3 of which 6 can be driven off at temperature around 100*c. For refrigeration. Another absorbent used in chloride of strontium from which 7 moles of NH3 out of 8 can be driven off which is an advantage over calcium chloride but it is very costly compared with calcium chloride.5. The heats of reaction are nearly equal for the above mentioned two steps and almost twice the latent heat of vaporization. This states that the COP of the cycle can not be more than 0. . The efficiency of the cycle is not very sensitive to high condensing temperature like other system. A gravity driven evaporation/condensation loop is the only feasible solution that will lend itself easily to an automatic operation. This is only possible with this cycle. . It has no problem to obtain evaporation temperature -10 to -15 oC. It has no moving parts so it does not require any maintenance. This system is well suitabled for freezing of ice in the form of block ice or in an ice bank tank. . meat and fish. The former can be used in crushed form for preservation of agricultural produce.