Environmental Engineering Reference
In-Depth Information
the direction of the chimney. The air is able to fl ow in unencumbered at the sides
of the enormous roof. The sun warms the air under the glass roof. This air then rises
upward, follows the gentle slope of the roof and then fl ows at great speed through
the chimney. The airfl ow in the chimney then drives wind turbines that generate
electric power over a generator.
The ground under the glass roof can store heat so that the power plant is still able
to deliver power even after the sun has set. If hoses fi lled with water are laid in the
ground, enough heat can be stored to enable the plant to provide electric power
around the clock.
At the beginning of the 1980s a small demonstration plant with a rated power output
of 50 kilowatts was built near Manzanares in Spain. The collector roof of this plant
had an average diameter of 122 m and an average height of 1.85 m. The chimney
was 195 m high and had a diameter of 5 m. This plant was dismantled in 1988 after
a storm knocked the chimney down. However, all the planned tests had been com-
pleted and the research plant lived up to expectations. It was the fi rst successful
demonstration of a solar chimney power plant.
Because the effi ciency of solar chimney plants compared to other techniques is very
low, these plants require large areas of land. Furthermore, the effi ciency increases
in line with the height of the tower. Therefore, to be economically viable plants
must be of a certain minimum size. New power plant projects are currently being
discussed in Australia, for example. Consideration is being given to a large-scale
200-megawatt plant with a tower height of 1000 m, a tower diameter of 180 m and
a collector diameter of 6000 m. It is diffi cult to predict whether the building of new
large-scale power plants will be fi nancially viable. But based on a long-term view,
solar chimney power plants in the desert regions of the world have the potential to
be fi nancially competitive compared to conventional plants (Figure 7.11).
Figure 7.11
Computer animation of a solar chimney power plant park. The towers can
also be used as viewing platforms.
Illustration: Schlaich Bergermann Solar, Stuttgart
.
