What is Solar Energy?

Sun, is a mid-size star that is composed from high density gasses under very high temperatures. It is 150 million km away from the earth and its diameter is 1.39 million km (i.e. 110 times bigger than the diameter of the earth). The temperature which is determined to be 5777 °K at its surface is estimated to be 8 million °K in its core. Under this very high temperature values, electrons are separated from the nucleus of atoms and are unattached.

This mixture is called plasma; under very high temperature values, the atomic nucleuses of lighter elements gather together to form the nucleuses of heavier elements.

Within this fusion reaction which is called as Thermo nuclear reaction, 564 million tonnes of hydrogen transfer into 560 million tonnes of helium in just one second. The mass difference between these two elements which is 4 million tonnes, spread into deep space in the form of thermal and light energy that is known as the solar energy.

The intensity value of the solar energy within the outer bounds of the earth’s atmosphere is 1367 W/m² on average, and this figure is known as the ‘Solar Constant’. Sunlight beams are reflected, deflected and absorbed by dust particles and gas molecules as they pass through the earth’s atmosphere. This causes the sunlight beams to weaken. The part of sunlight beams which pass through the atmosphere without running into any obstacles like dust particles and gas molecules and reach the surface of the earth, are called the direct radiation. The part that is reflected, deflected and absorbed by dust particles and gas molecules and reach the surface of the earth directionless is called the diffuse radiation.

The total amounts of direct and diffuse radiation indicate the total radiation value that fall onto the surface of the earth (onto the horizontal surface). Under optimal conditions (cloudless and clear skies, noon time) the total radiation value reaches up to 1000 W/m².

Depending on the type of the collectors, it is still possible to make use of 75 % of the total radiation.