SOLAR ENERGY

Solar energy is a very large,inexhaustible source of energy.The earth receives nearly 4000 trillion kWh of energy every day in the form of electromagnetic radiation from the sun.this is about a hundred times the total energy consumption of world in a year.Solar energy is cheap and free from pollution.It is virtually inexhaustible and is usually expressed in watts per square meter.The total energy incident over a period of time (such as a day) is expressed in kilowatt hours per square meter.Most parts of India receive 4 to 7 kWh of solar radiation per square meter per day. these are low values from the point of view of technological utilization.large collecting areas are required in many applications.Hence initial investments required for collection and storage of solar energy are large.Another problem associated with the use of solar energy is that its availability varies widely with time. The daily and seasonal variation in the energy available may required storage or a combination with other energy sources.
consequently,the energy collected when the sun is shining must be stored for use during the periods when it is not available.

Of the various forms in which solar energy can be converted,its conversion in the form of electricity is  considered to be most desirable. Presently,two technologies are being developed for conversion of solar energy to electrical energy.
1.Solar thermal energy technology.
2.Solar photovoltaic technolgy. 

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