The energy received from the Sun in the form of radiations is called solar energy. The sun has enormous energy. Only 0.1% of the sun energy reaches the earth. Solar energy received needs to be converted to other form for its use. There are two methods of solar energy technology i.e. thermal conversion and photoconversion. Thermal conversion takes place through direct heating and air heating. Photoconversion consists of photovoltaic, photosynthesis, photochemistry etc.
The various applications of solar energy are
Solar space heating: The buildings and homes can be kept warm during winter by using solar air heaters. In this process the collector is heated through solar energy. The air is heated by passing it over a heated collector. The air gets heated by convection and the heated air is taken to the space to be heated through ducts.
Solar water heating: A blackened metal plate absorber absorbs the heat and this heat is transferred to the water being circulating through the pipes beneath the absorber. A storage water tank is located above the top of the collector. This type of water heating system is common in hotels and houses now a day.
Solar cooking: The solar cooker is a metal box blackened from the inner side and with a glass cover at the top. The solar radiations pass through the glass and absorbed by the blackened surface results in increasing the inside temperature of box. The temperature is so high that the food can be cooked. The cooking takes comparatively more time.
Solar air conditioning: It consists of solar refrigeration system based on Rankine cycle. In this the ambient air is adiabatically cooled, dehumidified, cooled both sensibly and evaporatively and drawn to the space to be cooled.
Solar refrigeration: Solar refrigeration systems are used for domestic and small scale ice making units. These systems are very complicate to operate so not commonly used by the people.
Solar electricity: Solar energy can be converted to electric energy by using photovoltaic cells. It works on the principle of photoelectric effect.
Solar power plants: Fluid is heated through solar energy. The fluid heat is then used to generate the electricity through a conventional engine. To heat the fluid flowing through the pipes, concentrating type collectors are used.
Solar greenhouses: The greenhouse consists of a closed structure covered with a transparent material like glass or plastic. The glass acts as a solar collector. The solar energy is used for growing the plants. The radiations get entrapped within the greenhouse and the inside temperature of greenhouse increases.
Solar energy has also many other applications like solar furnaces, solar ponds, salt production etc.