The solar collectors, solar photo voltaics and solar thermal devices are based on solar radiation. The technical and economical performance of these device depends on the amount of solar radiation falling at a given location and time.
The Sun
The Sun is the star at the center of the solar system. It is seen in the sky and gives light to the Earth. When the Sun is in the sky, it is day. When the Sun is not in the sky, it is night. The Planets, including Earth, orbit around it.
The Sun gives off energy(ie. Solar Energy ) as electromagnetic radiation. Solar energy is very large, indexhaustible source of energy. The power from the Sun intercepted by the earth is approximately 1.8x1011MW, which is many thousands of times larger than the present consumption rate on the earth of all commercial energy sources.
The Earth
Earth is the third planet from the Sun, the densest planet in the solar system, the largest of the solar system’s four terrestrial planets and the only astronomical object known to harbor life.
According to radiometric dating and other sources of Evidence, Earth formed about 4.54 billion year ago.
