solar energy

Definition

Electromagnetic energy (solar radiation) transmitted by the sun (approximately one billionth of which reaches the earth) that is the basis of all terrestrial life. It amounts to about 420 trillion kilowatt-hours, and is several thousand times greater than all the energy used by all the people. Solar energy is harnessed by capturing the sun's heat (through solar heaters) or light (through photovoltaic cells). It is estimated that one square kilometer (about 0.4 square miles) of land area receives some 4000 kilowatts (4 megawatts) of solar energy every day enough for the requirements of a medium-sized town.