12-11-2012, 11:54 AM
ENERGY INDEPENDENCE USING PHOTOVOLTIAC CELLS
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ENERGY INDEPENDENCE-WHAT IS IT ACTUALLY ?
Today India depends heavily on coal, oil & natural gas (Fossil-fuels) for energy.
The end of fossil-fuel era is not far away.
Acute shortage of electricity possible from 2050 onwards.
By energy independence we mean a country NOT being dependent on its limited energy resources.
FUTURE PROBLEMS
Coal, oil, natural gas resources fast depleting
Global climate changing , rivers drying up
2007 : Population– 1.18 billion
Power demand- 1,21,000 MW
2030 : (Predicted) Population- 1.4 billion
Power demand- 4,00,000 MW
Energy crisis in India by 2050 as present day system will NOT be able to meet the demand
THE SOLUTION
Efficient utilization of fossil fuels
Maximum hydro and nuclear energy potential should be tapped
Renewable sources should produce at least 25 % of total demand
Renewable sources like solar,wind,tidal,biomass,geothermal to be used more
Achieve Energy Independence by 2030
WHAT IS A PV CELL?
Photovoltaic is the direct conversion of light into electricity at the atomic level.
Materials exhibit a property known as photoelectric effect that causes them to absorb photons of light and release electrons, these free electrons are captured, and electric current results.
Devices used in solar power plants
Solar cells are made up of same kind of semiconductor material i.e. silicon, used in the microelectronics industry.
For solar cells, a thin semiconductor wafer is specially treated to form an electric field.
When light energy strikes the solar cell, electrons are knocked .
If electrical conductors are attached to the positive and negative sides, the electrons can be captured in the form of an electric current
This electricity can then be used to power a load, such as a light or a tool.
HOW DOES IT WORKS?
To induce the electric field within a PV cell, two separate semiconductors are sandwiched together.
The "p" and "n" types of semiconductors correspond to "positive" and "negative" because of their abundance of holes or electrons.
Sandwiching these together creates a p/n junction, thereby creating an electric field.
When the p-type and n-type semiconductors are sandwiched together, the excess electrons in the n-type material flow to the p-type.
Absorption and Conduction
In a PV cell, photons are absorbed in the “p
layer”.
It‘s important to "tune" this layer to the properties of the incoming photons.
Another challenge is to keep the electrons from meeting up with holes and "recombining" with them before.
. By maximizing all these characteristics, we can improve the conversion efficiency of the PV cell.