What Is Solar Power

The significance of solar power to the human civilization.

Before mankind could understand how the earth depended on the Sun for its existence, many ancient cultures such as the Egyptians, the Greeks and the Romans considered the bright searing hot ball in the sky as a God that brought light and warmth. In those olden times, directly or indirectly, the solar power dominated human societies. The life cycles of communities revolved around the seasons set by the Sun. They recognized the Sun as the life giver, the all- powerful protector.

The Sun was worshipped in Egypt and Greece. The Sun occupied an important position in the belief-systems of many communities of people. Such as the Zoroastrians, the Aztecs of Mexico, the Incas of Peru, Hindus, Native American tribes, etc.

It is only in the modern times we have started understanding the magnificence of the Sun. The Sun is about 1.5 million times as big as the earth and is composed almost entirely of hydrogen gas. Its surface temperature is about 27 million deg C.

The Sun around which our planet Earth rotates, emits radiation. This solar radiation carrying energy falls on to the Earth. While traveling through the atmosphere, about 5% of the radiation is reflected away from the earth and about 15% is absorbed by the atmosphere. Thus the maximum energy received from the Sun through the incoming solar radiation (INSOLATION) at the equator is about 1000 W/m2. Presence of clouds, dust, etc. reduces this further and on an average we receive only about 800 W/m2 of solar power at the equator.

Plants on earth convert this energy into chemical energy by photosynthesis; vegetables, fruits and trees grow through this process. The living organisms (including humans) consume this bounty and grow. Forests grow; animal kingdom grows – all surviving on the energy received from the Sun. All the energy received from the Sun, of course, is not used up on the earth. After having passed through the Earth’s atmosphere, most of Sun’s energy is in the form of visible and infrared radiation. A large part of this energy is utilized in warming the earth. The earth, in turn, radiates this energy back outwards into the atmosphere.