What is “photovoltaics”?
The transformation of light energy (photo) into electrical energy (voltaics).
How does a solar cell work?
It consists of a thin semiconductor layer with a positive and negative
pole: when light falls on the cell an electrical voltage between the two
poles is generated.
How long does it take for the solar cell to produce as much
electricity as was needed for its manufacture?
From 4 to 18 months depending on the cell type. Every half hour, the earth
receives enough sunlight to provide for mankind’s annual energy
requirements. The energy is there, we just need to make use of it!
Electricity from Light: How?
Light striking certain substances causes the surface of the material to
emit electrons. It is as if light somehow kicks electrons right out of
atoms. Light striking other substances causes the material to accept
electrons. It is the combination of these two substances that can be made
use of to cause electrons to flow through a conductor.
This is the so called photo-electric effect. Photovoltaic means sunlight
converted into a flow of electrons (electricity). Photovoltaic devices, or
solar cells, are like generators that work in sunlight. They make
electricity without waste, noise or pollution. They produce electricity
without combustion. A solar cell is a solid state device in which there
are no moving parts (except for photons and electrons) so nothing wears
out.
The fuel is "photons". These can be thought of as "packets of sunlight"
that carry a phenomenal amount of energy to earth at a prodigious rate.
The Solar Panels of today make use of this abundant energy by using
silicon crystals with small amounts of impurity added. This process of
adding minute amounts of different elements into an otherwise pure crystal
is called "doping". By having two thin layers of doped material bonded
against one another, an electric current can be induced when exposed to
light.
Energy Content of Sunlight Sunlight has an energy content of 1 kW (1,000
watts) per square metre. The typical Solar Panel today achieves between
10% and 15% conversion. The theoretical maximum efficiency of a silicon
cell is about 21%. Using a more costly technology 31% conversion has been
achieved.
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