Environmental Engineering Reference
In-Depth Information
From the Quotation for a PV System to the Running Installation
■
Find out about public grants and low - interest loans.
■
Review economic feasibility based on quotations received (see Figure 5.17).
■
Clarify connection conditions with the energy supply company.
■
Arrange for the system to be installed by company specializing in photovoltaics.
5.6 Ecology
There is a persistent rumour that it takes more energy to produce the silicon for a
solar cell than the cell could ever generate during its lifetime. No one knows where
this rumour started. Presumably it was spread by opponents of solar technology
before detailed studies on the subject were even available.
It is true that quite a lot of energy is needed to produce solar cells. Temperatures
of well over 1000 °C are required in the production of silicon and for its subsequent
purifi cation. However, in contrast to conventional coal-fi red, natural gas and nuclear
power plants, no other energy supplies are needed in the operation of photovoltaic
systems. Once a solar system is in operation, it begins to supply back the energy
used in its production. Various scientifi c studies in the 1990s showed that in Germany
it takes around three to four years for solar cells to regenerate the energy needed to
produce them (Quaschning, 2005), but less than two years in Southern Europe or
at good US sites. Due to increased effi ciency and decreases in cell thickness, these
fi gures will now be much lower. With a lifetime of 20 to 30 years, a solar cell
generates vastly more energy than that used to produce it.
Today a 0.3 mm-thick, 6-inch crystalline silicon solar cell weighs around 16 grams.
The amount of energy needed to produce solar cells will continue to fall, because
there is an active interest in drastically reducing the materials used, and, conse-
quently, in reducing cost. For example, the amount of material used in thin fi lm
cells has already decreased considerably. It is expected that in the future solar
systems will be able to make up the energy needed for their production in just a
few months.
Various chemicals, some of them toxic, are used to produce solar cells. As with all
chemical systems, care has to be taken that no chemicals escape into the environ-
ment. This should not be a problem with the modern production systems and high
environmental standards that exist today.
An old solar system that is no longer useable, on the other hand, is considerably
less problematic. Nevertheless it would be a shame simply to scrap old and unviable
solar systems, because they contain valuable raw materials. The solar industry is
therefore working on methods to recover these materials. Initial attempts at recy-
cling solar cells seem promising. The solar modules are dismantled into their origi-
nal parts, and new photovoltaic modules are produced from the reclaimed cells.
