The light energy is transformed to electric
energy by a solar cell (see left image). A solar cell or photovoltaic
cell is made of special materials called semiconductors, the
most common semiconductor material is known as silicon. When
a light source strikes a solar cell, a portion of it is absorbed
by the semiconductor material. The absorbed light energy knocks
electrons loose, allowing them to flow freely.
Ordinarily pure silicon is a poor conductor
of electricity so impurities such as phosphorus and boron are
added to create what is known as a semi-conductor. The addition
of these impurities not only allows the silicon to conduct electricity,
but also acts to force electrons freed by light absorption to
flow in a certain direction. This directional flow of electrons
is also referred to as a current. By placing metal contacts
on the top and bottom of the solar cell, it then becomes possible
to draw that current off to use externally to perform work.
 A solar
electric module consists of an aluminum framed sheet
of highly durable low reflective, tempered glass that has had
individual solar cells adhered to the inner glass surface. These
individual solar cells are wired together in a series parallel
configuration so as to obtain the necessary voltage and current.
Individual cells are wired in series strings to increase the
module's voltage and the series strings are wired in parallel
to increase the module's current. The back of the module is
protected by another sheet of tempered glass or a long lasting
material such as Tedlar.
 The
series parallel connections are passed through the protective
backing and then wired to a weather proof junction box
which is permanently mounted to the back of the module. The
junction box is where the module's output connections are made.
Several solar modules wired together are known as a solar
panel, while several panels are called an array.
 The
solar panel or the array will always produce DC "direct
current" and in most of the configurationen allows 12 Voltage
current. A solar panel like the one above (size about 1,3 m
on 0,7 m) will produce 80-120 Watt - if there is enough sunshine
("solar radiation"). To produce about 1 kWh you need
a surface of about 8-10 m². The "energy harvest"
of 10 m² with high quality solar panels will be about 1.600
kWh per year - in Thailand. In Germany with less solar radiation
it is only about 800 kWh per year.
 As
Solar panels are producing DC-Voltage you have to connect them
to DC electric devices (rare) or you must transform
DC-Voltage to AC-Voltage with an inverter.
This inverter is a just small box but the "heart"
of every PV-system.
A reliable, long lasting AC inverter can invert about 10 m²
of Solar Panels.
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