Environmental Engineering Reference
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concentrated sunlight heats the air in a volumetric pressure receiver at about 15 bars
to temperatures up to 1100°C. A transparent quartz-glass dome separates the
absorber from the environment. The hot air then drives a gas turbine. The waste
heat of the turbine then fi nally drives the downstream steam turbine process. The
fi rst prototype has shown that this technology functions successfully.
With the combined gas and steam turbine process the effi ciency of the conversion
from heat to electric energy can be increased from about 35% to more than 50%
with a pure steam turbine process. As a result, total effi ciencies of more than 20%
are possible with this type of conversion of solar radiation into electricity. These
prospects justify the additional complexity and cost of receiver technology.
In contrast to parabolic trough power plants, there has not been much experience
with commercial plants in the solar tower plant area. Research facilities that are
optimizing system components and testing new components currently exist in
Almería (Spain) (see Figure 7.9), Daggett (USA) and Rehovot (Israel).
Figure 7.9 Research site for a solar tower power plant at Plataforma Solar de Almería
The fi rst commercial solar tower power plant to be put into operation was the
11-megawatt PS10 tower plant near Seville in Spain in 2006. However, instead of
heating up air, the receiver of this plant vaporizes water. Due to the low temperatures
the effi ciency of this power plant is still relatively low. In 2006 construction started
on the 20-megawatt PS20 tower plant, also near Seville, and other solar tower plants
are planned there.
Before it can be launched successfully in the market, the open air receiver technol-
ogy developed in Germany fi rst has to prove its suitability for practical use. This is
currently being tested at a newly built solar tower plant in Jülich, Germany. With
1.5 megawatts of power this demonstration plant is considerably smaller than the
commercial Spanish plants. The target in this effort is not the German power plant
market but to promote the export of German technology to the sunny countries of
the world.
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