Principles of electric generation by solar cell

Introduction: Solar energy is god gift to human beings. Daily trillions KWh of energy falls on earth. The solar energy is in the form of different sizes of solar radiations. Among these are 7% ultraviolet (200nm – 380nm- Neno meter means 10^-9M), 47% visible wavelengths (380nm – 780nm) & 46% infrared (780nm – 5000nm). The average irradiation falls on the outside of earths’ atmosphere is 1367 watts/M^2. About 25% energy is absorbed or scattered by ozone, water vapors, dry air, upper & lower dust and rest of extraterrestrial direct normal irradiation  1000watts/M^2 reaches to earth surface.

The India is getting good share of it due to its position on the earth. The Barmer a western district of Rajasthan the state of India is receiving solar energy 6-6.5 KWh/M^2/day (Killo-watt hour per meter square per day). There are two processes to generate electricity . One is solar thermal and other is photovoltaic. Our discussion is towards electric generation by photovoltaic.

The solar radiation also called “PHOTON”. The meaning of PHOTO is “produced by light” and VOLTAIC is “electricity produced by chemical reaction”. Thus a photovoltaic cell means a device which produces electricity by light. The device by which electricity is produced is called solar photovoltaic cell.

Solar cell: Solar cell is made of 0.9999% pure silicon doped boron & phosphorus. Silicon has 4 electrons in its outer bond.  Boron has three electrons in his outer bond so there is vacancy for one electron , so it is positive & phosphorous has 5  electrons in outer bond so it is has extra electron , it is negative. Thus constituted silicon with boron & phosphorous is  P-N junction diode and  is called solar cell.  The movement of free electron are  always from p side to N side of P-N junction diode even in night also.

Types of Solar cells:

There are two types of solar cells generally used one is Crystalline and second is thin film.  Further Crystalline solar cell is divided as mono crystalline and poly crystalline depends upon their manufacturing processes. The mono crystalline cell has 13.5% to 15% efficiency, where poly crystalline has 0.5% less efficiency to mono crystalline. The poly crystalline is cheaper than mono crystalline solar cell. The amorphous is thin film solar cell, but it has 6 % to 7% efficiency. So space required for thin film solar cell is double the space required for crystalline solar cell for same power output. In my opinion always use poly crystalline solar cell.

Principles of electricity generation: Keep the ‘N’ side of solar cell parallel to sun so that sun rays fall perpendicular to surface of cell. The sun rays constituted of photons falls on the cell. Sum photons reflected back, sum passes through cell and some are absorbed for generation of electricity. The photons dislodge the electrons from ‘N’  surface  (CONTINUE)