The developing worldwide shortage of petroleum emphasizes the need for alternative nergy sources which are both inexpensive and clean. There has been high interest in and high potential use of renewable energy sources since the energy crisis faced during the 1970s. During the last few decades, an increasing effort based on research and development has been concentrated on the utilization of renewable energy sources, e.g. solar energy, wind energy, tidal waves, biogas, geothermal energy, hydropower, and hydrogen energy. Among these sources, solar energy for refrigeration applications is very popular because it is direct and easy to use, renewable, and continuous, maintains the same quality, is safe and free, and is environmentally friendly.
The continuous supply of solar energy to the earth’s surface is equal to a power of about 100,000 TW. Approximately one-third of the radiation impinging on land area and accumulated over less than 2 hours should suffice to satisfy the entire primary energy demand by humans for the period of 1 year (Dincer, 1997). More than 25% of the total energy in the world is consumed for heating and cooling of buildings and providing hot water. Therefore, the diversion of this particular energy demand to an alternative source would result in a substantial reduction in the world’s dependence on fossil fuels. The annual incidence of solar energy on buildings in the United States is several times the amount required to heat these buildings; approximately 1015 kWh of solar energy is received on earth annually. It has been projected that by the year 2020 from 25 to 50% of the thermal energy for buildings could be provided from the sun. Consequently, solar energy is an available energy source for many applications ranging from electricity generation to food cooling.
