Solar Power - PhotoVoltaic Cells

Photo-Voltaic energy is an ideal choice of power for locations which are far from the electric grid. 

In many countries, it is not feasible to lay power lines to certain far-flung areas as there may be a small no of consumers.  Investing huge amounts of money in laying powerlines and maintaining them may not be economically viable.  Providing power by means of diesel generators may be expensive.

A practical and environmentally friendly source of power are Solar Cells.  Solar cells convert the sunlight into electricity.

Solar Cells work on the principle of the photo-voltaic effect.  When light falls on certain materials, the atoms absorb the photons and release an electron.  These electrons create an electric potential.  When an external circuit is connected, a current flows.  The direct conversion of sunlight to electricity makes the modules compact without any emissions or residue.  Photovoltaic cells are thus popular for powering small electronic devices  and lighting.

Photovoltaic modules have been used for powering aircraft, cars and even the international space station.

Photovoltaic modules are made of materials such as silicon, cadmium telluride, gallium arsenide, etc.  The basic silicon cell consists of a NP junction. When light is incident on the PN junction, electron-hole pairs are produced.  This creates a voltage across the junction.  When an external load is connected, current flows.

Photovoltaic cells are usually covered by an anti-reflective coating to prevent the incident light from being reflected away.

Current Photovoltaic cells can achieve effiency of around 30%.  Cells with concentrated sunlight focused on them can achieve still higher efficiencies.

It would be interesting to note that a solar cells is just an LED in reverse.  An LED (A light emitting diode) functions by emiting light when a voltage is applied, while the solar cell generates a voltage when light is incident.  A solar cell is specially designed to have a wide PN junction which can collect more light.   

The solar cell technology needs further development before it can be widely used for base power generation.  It is hoped that further research with new materials will improve efficiency and lower the high initial capital costs. 

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