Environmental Engineering Reference
In-Depth Information
371 °C
17 bar
391 °C
Reheater
(Natural gas)
Reheater
(solar)
Generator
G
371 °C, 100 bar
Steam
turbine
Solar
superheater
Solar field
510 °C
Conden-
ser
Steam
generator
Boiler
Natural gas
Solar
preheating
283 ° C
Steam cycle
Fig. 5.19 Diagram of a parabolic trough power plant (SEGS VI and VII) (refer to /5-19/)
Pump
Pump
Integrated Solar Combined Cycle System (ISCCS). To enhance availability,
efficiency and controllability, the solar field may be incorporated into a combined
cycle power plant. Solar steam is superheated once more up to a temperature of
approximately 530 °C in a heat recovery boiler.
If a solar collector field is integrated into the steam cycle of an Integrated Solar
Combined Cycle System (ISCCS) the "solar" steam is transferred to the high pres-
sure cycle of the steam generator. The required fossil fuel energy is thus reduced,
so that more steam can be generated with the same flue gas stream or less flue gas
is required to provide the same quantity of steam. In this operating mode, the gas
turbine may be operated at part load; the solar field thus saves fossil fuel energy.
The share of solar power generation is between 3 and 10 %.
Integration into conventional power plants. A further possibility to integrate
solar heat into conventional power plant processes is to incorporate solar heat into
the feed water preheating of conventional steam power plants. For internal feed
water preheating, normally turbine extraction steam is required, which is then not
available for expansion in the turbine anymore. If solar heat is available for feed
water preheating, the steam can be utilised for the turbines.
In summer 2004, the first phase of solar feed water preheating by means of
Fresnel collectors was commissioned in Liddell, Australia. For the final configu-
ration it is planned that the last high-pressure pre-heater is exclusively operated by
solar heat. In addition, this plant is to be tested with additional steam generation
/5-17/.
5.3.2 Economic and environmental analysis
The following explanations are aimed to assess parabolic trough power plants
according to economic and environmental parameters.
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