Environmental Engineering Reference
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Figure 5.7 Cross-section of a thin fi lm photovoltaic module.
the same power output, and, therefore, more assembly is required and the associated
costs are higher. However, because less material is used, in the long term the cost
of thin fi lm modules could fall below that of crystalline modules. If the effi ciency
of thin fi lm modules can also be increased, this technology could put an end to the
current predominance of crystalline silicon solar cells.
In addition to thin fi lm materials, other technologies are currently being tested.
Pigment cells and organic solar cells could eventually offer a cost-effective alterna-
tive to current technologies. At the moment it is almost impossible to project which
technologies will fi nd acceptance in 30 or 40 years. But competition is bringing new
life to the sector. Costs will continue to drop due to the competition of different
technologies for photovoltaics. So in the medium term photovoltaics will be very
important in the effort to provide low-cost and climate-compatible electricity supply.
5.3 Photovoltaic Systems - Networks and Islands
5.3.1 Sun Islands
With photovoltaic systems a distinction is made between island systems and grid-
coupled systems. Solar island systems work autonomously without being connected
to an electricity grid. For example, they are often used in small applications, such
as wristwatches and pocket calculators, because in the long run they are less expen-
sive than energy supplied by disposable batteries, and a network cable in this case
would be highly impractical. Solar systems are also popularly used for small systems
like car park ticket machines. In this case it is less expensive to install a photovoltaic
system than to lay network cables and install a meter (Figure 5.8).
The big market for solar island systems is in areas that are far from an electricity
grid. Globally, around two billion people have no access to electricity. Even in
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