Information Concerning Residential And Commercial
Solar Panels
Solar Power Technology From Raw Silicon To Tapping The Sun's Limitless Energy.
Solar cells are devices
that convert light energy (photons) into electricty
(electrons) through a process known as the photovoltaic
effect. The term "photovoltaic" is a Greek derivative coming
from the terms (phōs) for light and "voltaic" for
electricity. The photovoltaic effect was first discovered in
1839 by the French physicist A.E. Becquerel but the world
would have to wait until 1883 for the first functional solar
cell to be built by American inventor Charles Fritts. This
first cell used Selenium and had an efficiency of 1%. In
1954 while experimenting with semiconductors, Bell
Laboratories introduced the first practical silicon solar
cell which was doped with specific impurities that began the
evolution of what would become today's high efficiency solar
technology.
Solar modules that used
these early solar cells had an efficiency rating of about 6% which
was first demonstrated in April of 1954. In 1958 Vanguard 1
became the first satellite to use solar technology to power
its electronics in space. Today solar panel costs have
dropped dramatically and have
efficiency ranging from about 6% for thin film technology
and up to 18% for conventional crystalline technology.
Modern solar panels are used in
home solar power power applications and Commercial Solar
applications as well as
off grid solar power and
RV solar
power uses. Solar power panel systems are even used to
provide emergency power and
for Solar powered air
conditioning systems in homes and businesses.
Mono Crystalline (Single crystal)
Silicon Cells
Mono crystalline or single
crystalline solar cells are produced primarily by the Czochralski (Cz) process. The large diameter single crystal
ingots that are created from this process are cut into thin
wafers using thin wire saws. Conductive energy collection grids
are silk screened onto the surface of these wafers and a
functional solar cell is produced. Solar panels that utilize
single crystalline solar cells offer among the highest
efficiencies available on today's commercial market.
Poly Crystalline (Multi crystal)
Silicon Cells
Solar cells that are
created from polycrystalline or (multi crystalline) technology
are cut from a silicon boule that has been casted from molten
silicon and allowed to cool. The rate that the silicon is
allowed to cool effects the size of the crystals that are
formed. The multi crystalline solar cell is grown from lower
grade silicon material which forms multifaceted
crystals that grows in different
directions. Conventional multi crystalline
solar cells
typically have a slightly lower efficiency resulting in larger
individual cells and thus typically a slightly larger module.
Most panels that are made today use polycrystalline
solar
cells.
Ribbon Silicon
Technology
A process which cost less
than traditional manufacturing techniques is known as "Ribbon Growth". Silicon is
formed directly into thin wafers which avoid the expensive
process of sawing silicon from a solid silicon boule. One such
method is known as "Edge defined film fed growth" starts with
two crystal seeds. A thin layer of silicon is formed as the
seeds are pulled from a molten vat of silicon which produces a
continuous ribbon of silicon. Solar panels that that use this
technology are effective at saving
material but the quality of the material produced is not as high
as the Czochralski (Cz) process.
Cell efficiency may also be reduced. Solar panels that use
this type of technology are not as common as more
traditional higher efficiency technologies.
UMG Technology (Ugraded
Metalurgical Grade Silicon)
In an effort to save on
materials and processing cost. A few manufacturers have turned
to less pure silicon to manufacture solar cells. Unlike the nine
9s (99.9999999%) or even the eleven 9s (99.999999999) of purity
that is the result of the
conventional Siemens process, solar
modules that are manufactured using UMG are of less purity
which can have an effect on efficiency. Several Canadian based
solar companies have introduced these lower cost, lower
efficiency based products into the European and U.S. markets.
CdTe
Solar Technology (Cadmium
Telluride Thin Film) Thin Film
Like their crystalline
silicon thin film cousins,
Cadmium Telluride CdTe solar suffers from the same
stigma of lower efficiency. The primary difference between
both crystalline silicon solar and Amorphous silicon solar
when compared to CdTe solar is that CdTe does
not utilize silicon in its design.
Instead CdTe solar panels
use a compound which is formed by a combination of Cadmium
and Tellurium blended with Zinc. Another difference between
CdTe and more traditional solar panel technologies is that
Cadmium one of the substances used to form the compound CdTe
is an extremely toxic material with known cancer causing
effects which raises concerns among health officials.
Cadmium telluride is
toxic, but only if it is ingested or its dust is inhaled.
There is also concern if it is handled improperly for
example, without the use of appropriate gloves and other
safety precautions. Although CdTe modules have been touted as being safe
especially once encapsulated in a solar
panel, environmental concerns remain if these solar panels
are not be disposed of or recycled properly should they
become broken, defective, or decommissioned at the end of
their life cycle.
Amorphous
Silicon
Solar (Thin Film) Thin
Film
Unlike crystalline
silicon whose atoms are arranged in a very orderly fashion,
the atoms in amorphous or thin film solar panels are not
arranged in any specific pattern and in fact contain many
structural and bonding defects.
Amorphous solar panels are
made by utilizing a vapor deposition process not unlike
spraying the silicon which deposits a microscopic thin layer
of doped silicon onto a glass substrate. Although thin film
is less costly to manufacture than mono or
poly crystalline technology they do suffer from several
drawbacks, among them are a much lower efficiency. While
mono and poly crystalline solar technologies typically
produce power in the 12 to 15 percent efficiency range,
thin
film technology's efficiency range from 6 to 9 percent.
Another drawback with Amorphous technology is an anomaly
know as the Staebler-Wronski
effect whereby the conversion efficiency of a Amorphous
solar panel has the tendency to degrade causing a drop in
output of up to 20% when it is first exposed to sunlight.
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