Solar Energy and Methods of Harvesting Solar Energy

 Solar Energy :

The energy we get directly from the sun is called the solar energy. 

The nuclear fusion reactions occurring inside the sun release enormous amount of energy in the form of heat and light. Several techniques are available for collecting, converting and using solar energy.  

Methods of Harvesting Solar Energy : 

Some Important solar energy harvesting devices are given below.

1.Solar Cells (or) Photovoltaic Cells (or) PV Cells :

Solar cells consists of  a p-type semiconductor (such as Si doped with B) and n-type semiconductor (such as Si doped with P). They are in close contact with each other. When the solar rays fall on the top layer of p-type semiconductor, the electrons from the valence band get promoted to the conduction band and cross the p-n junction into n-type semiconductor. There by potential difference between two layers is created, which causes flow of electrons (ie., an electric current). 

Uses :

      Used in calculators, electronic watches, street lights, water pumps to run radios and TVs. 

1.Solar Battery :

       When a large number of solar cells are connected in series it form a solar battery. Solar battery produce more electricity which is enough to run water pump, to run street-light, etc., They are used in remote areas where conventional electricity supply is a problem.

 2. Solar heat Collectors :

 It consists of an insulated box inside of which is painted with black paint. It is also provided with a glass lid to receive and store solar heat. Inside the box it has black painted copper coil, through which cold water is allowed to flow in, which gets heated up and flows out into a storage tank. From the storage tank water is then supplied through pipes.

Significance of solar energy :

1. Solar cells are noise and pollution free.

2. Solar water heaters, cookers, require neither fuel nor attention while cooking food. 

3. Solar cells can be used in remote and isolated areas, forests, hilly regions.