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Photovoltaics
(PV), or solar cells, convert sunlight to electricity directly without
boilers, turbines, generators, piping or cooling towers.
They generate power
when particles of sunlight (photons) strike certain semiconductor
materials such as silicon. As silicon atoms absorb the sunlight, they
dislodge the electrons and allow them to move.
The free electrons
collect on the specially treated front surface of the cell, causing an
imbalance of charge between the front and back surfaces. This charges the
surfaces like the terminals on a car battery. A flow of electrons occurs
when one end of a wire is attached to the top layer and the other end to
the layer underneath.
Technicians connect
individual cells into panels to obtain required voltage. A power
converter is needed to change the direct current to alternating current.
PV devices have
provided energy for spacecraft for many years. They also are used for
beacons or floating buoys far from the nearest power lines.
Large-scale use of
PV devices for industrial or residential power is currently out of the
question because of the very high cost. Recent worldwide research could
result in considerably lower cost of PV in the near future.
To generate one
kilowatt of electricity when the sun is brightest would require about 100
square feet of PV panels. |
