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Introduction to Solar Refrigerator
The solar refrigerator is the refrigeration system that runs on the solar energy. The solar refrigerator comprises of all the traditional components like the compressor, condenser, expansion valve and the evaporator or the freezer. The power is supplied not by the domestic electrical supply system, but from the solar panel.
The solar system of the solar refrigerator comprises of the solar panel that collects the solar energy. The solar panels are fitted with photovoltaic cells that convert the solar energy into electrical energy and store it in the battery. During the normal running of the solar refrigerator the power is supplied directly by the solar panel, but when the output power of solar panels is less, the additional power is supplied by the battery. The battery is recharged when excess amount of power is produced by the solar panels.
The output supply of the batteries and the solar panel is DC with voltage of about 12. A typical solar system produces 300W or 600W of power depending upon the size of the desired refrigerator. The voltage regulator is connected to the battery to convert the low voltage DC supply to high voltage AC supply to run the compressor. It is advantageous to use the AC supply compressor since it can run on domestic electrical supply also. Some of the solar refrigerators use compressors that can run directly on DC supply.
Another application where the solar energy can be very useful is the vapor absorption refrigeration system. In these systems heat from the steam is used to heat water mixed with lithium bromide or ammonia that act as the refrigerant. In these machines, the heat produced by the steam can be replaced by the heat produced by solar energy.
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Advantages and Disadvantages of the Solar Refrigerator
The advantages of the solar refrigerator are similar to the ones offered by the other solar energy devices. Since the solar refrigerator runs on solar energy there is lots of saving of electrical power that would have been produced by the conventional power plants causing lots of pollution. The solar energy is available freely, abundantly and is a clean source of energy. One of additional advantage is that the excess power produced by the solar refrigerator can be used for the other domestic purposes.
The solar refrigerators can be very useful in far off remote places where there is no continuous supply of electricity. In Maruata village, located on Mexican Pacific Coast, the fishermen use solar refrigerator for keeping the fishes fresh (http://www.scientificamerican.com/article.cfm?id=solar-refrigeration.)
The disadvantage of the solar refrigerator is that the production of power is not uniform since solar energy is not available throughout the day and it also changes in intensity during various times of the year. Hence, it can be used only in places where strong sun rays are available throughout the year and most parts of the day. The other major disadvantage of the solar refrigerator is the size of the solar collector occupying large areas of the home. To produce power sufficient for the refrigerator big solar panels are required. The solar collectors can be kept on the terrace, but still they will occupy lots of space.
A number of solar refrigerators have been developed, and they are being used successfully. However, the technology has not been developed to the stage for carrying out commercial production of the solar refrigerators. There are few companies manufacturing solar refrigerators, but high costs of the solar equipments, their low efficiency and their large sizes have not yet made them the popular choice.
When working in the Engineering College as a lecturer, I guided a group of students for the solar refrigerator project. They were highly enthused to show to the public, other teachers and the examiner how a refrigerator can work without the domestic electricity. But by the time the sun started setting, I could see their enthusiasm also settling down.