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How
photovoltaics work |
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Even if you haven’t seen a residential or commercial solar electric
system up close, odds are that you have been exposed to the technology
in the form of a solar-powered calculator, watch, or emergency road-side
phone. Just a few solar cells and a little sunlight supply these devises
with electricity. Regardless of size, solar electric systems have one thing
in common – they are using one of the most environmentally friendly
forms of energy production, photovoltaics, to transform light into electricity.
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About
the discovery...
Around 160 years ago, scientists had already discovered that certain
materials, so called semiconductors, under certain circumstances act
as conductors for electricity. By the end of the 19th century, building
components had been developed which were able to transform light into
electricity, but not in sufficient amounts to be commercially viable.
Eventually, following the preparations for the first space travel (around
1950), the research was intensified. First priority was the search for
new, suitable materials from which to make photovoltaic cells. Soon
it was realized that silicon possessed the best qualities for this purpose.
It is perfectly suited for the manufacture of semiconductors, and, as
the second most commonly found element in the world, it is obtainable
in large quantities. |
On earth, silicon is generally found in the form of sand. Apart from silicon,
however, sand contains many other materials in differing quantities. For
the production of solar cells it is necessary to obtain the element in
its purest form, in order to achieve the highest possible efficiency of
the solar cells.
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Silicon in use
In order to produce electricity from silicon, energy must flow from
positive to negative poles, just like in a battery. Consequently, a
photovoltaic cell is made up of two layers, one positive and one negative.
The individual layers are doped by adding certain chemical elements
to the silicon. When light falls on this cell, electrical tension builds
up between the layers which can be picked up at the poles.
One single cell produces very little electricity; therefore many photovoltaic
cells are coupled together in one module. The sum of the solar modules
in an installation makes up the PV generator. |
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In this manner, a
sufficiently high amount of tension and energy is produced
to supply an entire household with electricity. But before
the energy from sunlight can be used, it must be processed.
The photovoltaic cells deliver direct current, which has to
be transformed into useable 50Hz alternating current by a static
converter. In the case of autonomous installations, the solar
produced energy is stored in batteries. That´s how a
reliable energy supply is guaranteed even at night or at times
of reduced sunlight. |
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