Power Plant Engineering

‘Solar Power Tower’ Power PlantThe first is the 'Solar Power Tower' design which uses
thousands of sun-tracking reflectors or heliostats to direct and concentrate solar radiation onto a boiler
located atop a tower. The temperature in the boiler rises to 500 – 7000°C and the steam raised can be
used to drive a turbine, which in turn drives an electricity producing turbine. There are also called
central Receiver Solar Power Plants.
It can be divided into solar plant and conventional steam power plant. The flow diagram is given
in Fig. 2.12.

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NON-CONVENTIONAL ENERGY RESOURCES AND UTILISATION
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Central Receiver
Beam Radiation
Heliostat Field
Tower
ST
Fig. 2.12. Central Receiver Solar Power Plant.
A heliostat field consists of a large number of flat mirrors of 25 to 150 m
2
area which reflects the
beam radiations onto a central receiver mounted on a tower. Each mirror is tracked on two axis. The
absorber surface temperature may be 400 to 1000°C. The concentration ratio (total mirror area divided
by receiver area) may be 1500. Steam, air or liquid metal may be used as working fluid. Steam is raised
for the conventional steam power plant.
‘Distributed (Parabolic) Collector System’ Power Plant. The second type is the distributed
collector system. It is also called solar farm power plant as a number of solar modules consisting of
parabolic trough solar collectors are interconnected. This system uses a series of specially designed
‘Trough’ collectors which have an absorber tube running along their length. Large arrays of these
collectors are coupled to provide high temperature water for driving a steam turbine. Such power
stations can produce many megawatts (mW) of electricity, but are confined to areas where there is
ample solar insulation.
Every module consists of a collector as shown in Figs. 2.13 and 2.14. It is rotated about one
axis by a sun tracking mechanism. Thermo-oil is mostly used as heating fluid as it has very high boiling