Three known approaches that use solar energy to provide refrigeration at temperature below 0 degrees include photovoltaic (PV) operated. PDF | Energy consumption increases very rapidly as the world Solar energy is currently a subject of great interest, and refrigeration is a. Solar-Powered Refrigeration System. Benefits. • Environmentally friendly: Harnesses the energy of the sun to reduce dependence on fossil fuels and eliminates.
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A solar refrigerator capable producing of kg of ice per day reported by Kirpichev and Baum () which is operated by a vapour. Procurement Guidelines. Battery Powered Solar Refrigerators and. Freezers. Key information for UNICEF staff and partners, ensuring the. PROKLIMA I SOUTHERN AFRICA. Introducing Solar-Powered Refrigerators in. Southern Africa. Installation of a SolarChill refrigerator in Ghana by Greenpeace.
This contribution is nearly times greater than the direct contribution of the refrigerant alone. Moreover, approximately 62 million mew units are being manufactured worldwide every year, and hundreds of millions are currently in.
Therefore, in response to global concerns over greenhouse resorts are being made to produce refrigerator-freezers with low energy consumption.
In most of the developing third world, adequate supplies of drinking water and water for irrigation are a scarce commodity. In many places in Africa, India and Central and South America, adequate supplies of water are found only at considerable depth below the surface.
These locations generally do not have the infrastructure to provide an electrical grid to pump the water with electricity nor do they have the infrastructure to provide roads to bring in electrical generators or even the fuel for those generators. Therefore without an electrical grid or without generators to generate electricity, isolated areas do not have potable water nor do they have the refrigeration to keep medicine or foodstuffs from spoiling.
Even in the United States, there are communities such as the Amish communities where electricity is banned. Here the lack of cooling capabilities severely limits the production of various products. Because of the lack of cooling, milk production is limited to Grade B. Referred to as advanced adsorption chillers they represent one of the new technology options that are under development.
Advanced adsorption cooling technology offers the possibility of chillers with greater COPs and reduce cost of the system. The invention can improve refrigerating unit, raise coefficient of performance, reduce energy cost of refrigerating unit and has notably social and economic benefit. However, unlike vapour compression refrigeration systems, the required input to absorption systems is in the form of heat. Hence these systems are also called as heat operated or thermal energy driven systems.
Similar to vapour compression refrigeration systems, vapour absorption refrigeration systems have also been commercialized and are widely used in various refrigeration and air conditioning applications. Since these systems run on low-grade thermal energy, they are preferred when low-grade energy such as waste heat or solar energy is available.
History of Solar-Powered Refrigerator
Since conventional absorption systems use natural refrigerants such as water or ammonia they are environment friendly. The function of compressor in the vapor compression system is to continuously withdraw the refrigerant vapor from the evaporator and to raise its pressure and hence temperature, so that the heat absorbed in the evaporator, along with the work of compression, may be rejected in the condenser to the surroundings In vapor — absorption system, the function of the compressor is accomplished in a three — step process by the use of the absorber, pump and generator.
As Absorption unit become more popular not only in industry but also on a domestic level, their simulations become more important. This enables better understanding of the complex thermodynamic behavior which such system exhibit and for that various mathematical model have been created in the past. Nowadays, investigation of ammonia water H2O-NH3 systems is becoming more important especially with the introduction of efficient generator-absorber heat exchanger GAX absorption units.
Although the latter systems are in principle the same, they require additional devices which in themselves require thermodynamic modelling. But in reality it is less than 1. They require much larger cooling towers to reject the waste heat owing to their low COPs, and thus servicing them is not less than a nightmare. High cost The absorption refrigeration systems are much more expensive than the vapor- compression refrigeration systems which are quite obvious as their cost of production is high because of complex and large parts.
This also makes them difficult to service. This leads to higher power demands from power stations which in turn lead to more CO2 emissions. Absorption systems use a low grade form of energy in order to provide a cooling effect. This means that the source of input energy need not necessarily come from electric power but rather from any other heat source which is at a sufficiently high temperature. Apart from being advantageous from this perspective of energy use, such systems also provide other advantageous over vapour compression refrigeration units employing compressors.
In the vapor compression cycle the capacity control of the system is done from the compressor and in most of the cases stepwise capacity control is obtained.
In case of the absorption refrigeration system it is possible to obtain stepless capacity control and zero capacity when there is no load on the system. In the vapor compression refrigeration system the compression of the refrigerant is done by compressor which can be of reciprocating, rotating or centrifugal type.
In the vapor absorption refrigeration system, the compression of the refrigerant is done by absorption of the refrigerant by the absorbent. As the refrigerant is absorbed, it gets converted from the vapor state to liquid state so its volume reduces. C engines, etc. Hence Therefore, more wear, tear and noise.
Experimental Investigation on an Absorption Refrigerator Driven by Solar Cells
The h It requires very strong foundation so that it absorption refrigeration systems operate can remain intact under vibrations and high silently. Here two paper review are as following 6. First of all they describe the Vapour Absorption Refrigeration System acts as an alternative to existing systems as it requires low grade of energy for example; solar energy as it's renewable and present in enormous amount. So, in recent times a lot of research is going on to improve such systems that affects least to the environment and humanity but acts for same purpose in very efficient manner.
Here they also concluded that Vapour Absorption System has an upper edge over the Vapour Compression System taking in regard of the environment. In absorption systems there is no danger of depletion of ozone layer, all renewable sources of energy could be used such as, solar energy, wind energy, bio-gas etc.
The only disadvantage with such system is low COP and requires longer time duration to perform the complete operation. Renjith and P. Joshy Department of mechanical engineering Cochin University of science and technology V. Renjith And P. Joshy published research paper on vapour absorption refrigeration system using law grade energy-an ecofriendly approach. They described that major commercial refrigerants, chloro fluro carbons are going to be phased out shortly as a part of Montreal protocol since they cause the phenomenon called greenhouse effect and depletion of ozen layer.
Extensive literature survey has shown that ammonia water pair is most studied and suitable pair of vapour absorption refrigeration system as it is very environmental friendly. Here this paper they are also described the basic principle of vapour absorption refrigeration system and to achieve performance of simple ammonia water var cycle, two addition component namely heat exchanger and rectifier is added to simple var system. Here he reduces the heating requirement in the generator and improves the cop and also reduced the cooling requirement in absorber.
Use of rectifier is to remove water vapour in refrigerant vapour leaving the generator. Here they also gives the thermodynamic analysis of two pressure var system. As generator temperature increases cop decreases and as condenser temperature increases cop decreases. Refrigeration components 1. Evaporator 2. Condenser B.
International Journal of Photoenergy
Regeneration Components 1. Generator 2. Absorber C.
Additional Components 1. Pump 2. Heat Exchanger 3. Expansion Devices 4. Solar Panel 7. The liquid is evaporated, or vaporized, into a gas. The evaporators are heat exchanger surfaces that transfer the heat from the substance to be cooled to the refrigerant, thus removing the heat from the substance. They are also classified in different manner depending on the method of feeding the refrigerant, construction of the evaporator, direction of air circulation around the evaporator, application and also the refrigerant control.
In the domestic refrigerators the evaporators are commonly known as the freezers since the ice is made in these compartments. In case of large refrigeration plants and central air conditioning plants the evaporator is also known as the chiller since these systems are first used to chill the water, which then produces the cooling effect. In the evaporator the refrigerant enters at very low pressure and temperature after passing through the expansion valve. This refrigerant absorbs the heat from the substance that is to be cooled so the refrigerant gets heated while the substance gets cooled.
Even after cooling the substance the temperature of the refrigerant leaving the evaporator is less the than the substance. The refrigerant leaves the evaporator in vapor state. The most common medium consists of parallel tubes but others have plates or coils typically made from copper or aluminum. The concentrating and separating section removes the vapor being produced from the solution. Thus the absorber consists of the weak solution of the refrigerant ammonia in this case and absorbent water in this case.
When ammonia from the evaporator enters the absorber, it is absorbed by the absorbent due to which the pressure inside the absorber reduces further leading to more flow of the refrigerant from the evaporator to the absorber. At high temperature water absorbs lesser ammonia, hence it is cooled by the external coolant to increase it ammonia absorption capacity.
Here, solar panel is used for the heating purpose. Separates the dissolved ammonia from the water-ammonia solution. The refrigerant ammonia solution in the generator is heated by the external source of heat. This is can be steam, hot water or any other suitable source. Due to heating the temperature of the solution increases.
The refrigerant in the solution gets vaporized and it leaves the solution at high pressure. The high pressure and the high temperature refrigerant then enters the condenser, where it is cooled by the coolant, and it then enters the expansion valve and then finally into the evaporator where it produces the cooling effect.
This refrigerant is then again absorbed by the weak solution in the absorber. This solution enters the pressure reducing valve and then back to the absorber, where it is ready to absorb fresh refrigerant.
In this way, the refrigerant keeps on repeating the cycle. The pressure of the refrigerant is increased in the generator, hence it is considered to be equivalent to the compression part of the compressor.
There are two types under this category a Natural convection and b forced-air type. As air comes in contact with the warm-condenser tubes, it absorbs heat from the refrigerant and thus the temperature of the air increases.
Warm air being lighter, rises up and in its place cooler air from below rises to take away the heat from the condenser. This cycle goes on. Since air moves very slowly by natural convection, the rate of flow of heat from the refrigerant to air will be small. Thus a natural convection condenser is not capable of rejecting heat rapidly. Therefore a relatively large surface area of the condenser is required.
Hence the use of this type of condenser is limited to very small units such as domestic refrigerators. It, however, requires very little maintenance. In the small units, the condenser is fixed at the rear of the refrigerator cabinets. Generally, steel tubes are used, steel being cheaper than copper. To increase the heat-transfer area, wires are welded to the condenser tubes. These wires provide mechanical strength to the coil as well.
In certain designs, widely-spaced fins are used. It is necessary to space the fins quite widely to avoid resistance to free natural convection air movement over the condenser. The condenser coil is of the finned type. Fins in such coils are closely spaced ranging between 8 and 17 fins per inch. The space between the fins gets choked with dirt and lint.
Therefore to obtain optimum capacity, the fins should be kept clean. Pumps operate via many energy sources, including manual operation, electricity, engines, or wind power, come in many sizes, from microscopic for use in medical applications to large industrial pumps. When the absorbent absorbs the refrigerant strong solution of refrigerant absorbent ammonia water is formed. This solution is pumped by the pump at high pressure to the generator.
Thus pump increases the pressure of the solution. This refrigerant ammonia in this case then enters the evaporator. Controls the amount of refrigerant flow into the evaporator. Cause a pressure drop Isenthalpic of the working fluid. Causes sudden drop in temperature. If the solute itself has some vapour pressure i.
If the solute is non-volatile e. In the simplest absorption refrigeration system, refrigeration is obtained by connecting two vessels, with one vessel containing pure solvent and the other containing a solution.
Since the pressure is almost equal in both the vessels at equilibrium, the temperature of the solution will be higher than that of the pure solvent. This means that if the solution is at ambient temperature, then the pure solvent will be at a temperature lower than the ambient. Hence refrigeration effect is produced at the vessel containing pure solvent due to this temperature difference. The solvent evaporates due to heat transfer from the surroundings, flows to the vessel containing solution and is absorbed by the solution.
This process is continued as long as the composition and temperature of the solution are maintained and liquid solvent is available in the container. As shown in the figure, low temperature and low pressure refrigerant vapour from evaporator at state 1 enters the absorber and is absorbed by solution weak in refrigerant state 8. The heat of absorption Qa is rejected to an external heat sink at To.
The solution, rich in refrigerant state 2 is pumped to the generator pressure Pg by the solution pump state 3. The pressurized solution gets heated up sensibly as it flows through the solution heat exchanger by extracting heat from hot solution coming from generator state 4.
Heat is supplied to this solution from an external heat source in the generator Qg at Tg , as a result refrigerant vapour is generated absorbent may also boil to give off vapour in case of ammonia-water systems at state 5. This high pressure refrigerant liquid is throttled in the expansion device to evaporator pressure Pe state 10 from where it enters the evaporator, extracts heat from low temperature heat source Qe at Te and leaves the evaporator as vapour at state 1, completing a cycle.
This process effectively creates an "ice pack," enabling temperature maintenance inside the enclosure in the absence of sunlight. Proper sizing of the highly insulated cabinet, phase change thermal storage, variable speed compressor, and solar PV panel allow the refrigerator to stay cold all year long.
To optimize the conversion of solar power into stored thermal energy, a compressor control method fully exploits the available energy. Other power optimization measures include: Smoothing the power voltage via a capacitor, providing additional current during compressor start-up Monitoring the rate of change of the smoothed power voltage using a controller to determine if the compressor is operating below or above the available power maximum, enabling adjustment of the compressor speed if necessary Replacing the capillary tube in the refrigerator system with an expansion valve, improving energy efficiency in certain operating conditions These adjustments to the compressor operation contribute to the conversion of the majority of the available solar power into stored thermal energy.
Applications may include a cold side water loop or incorporation of the evaporator into the thermal storage. Electronic controls also can be added to provide backup power from an alternative power source such as an electric grid. Why it is Better The standard use of AC electricity supplied by the electric utility to power a single-speed vapor compression cooling system in a moderately insulated cabinet ties refrigerators to an electric grid and limits where they can be used.
This prohibits their use in off-grid applications and maintains a dependence on fossil fuels for power. For these reasons, the demand for solar appliances of all kinds is increasing. However, other existing solar refrigerators use batteries, presenting a number of disadvantages.It is this method of refrigeration that is most widely used today and is known as the vapor-compression process. Cyclic Refrigeration a. Thus one can utilize the extra steam from the boiler, or generate extra steam for the purpose and also use the hot available water.
High cost The absorption refrigeration systems are much more expensive than the vapor- compression refrigeration systems which are quite obvious as their cost of production is high because of complex and large parts.
Click here to sign up. This process effectively creates an "ice pack," enabling temperature maintenance inside the enclosure in the absence of sunlight.
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