5. Conclusion
The energy and exergy analysis has been carried out of
a conceptually proposed direct steam generation (DSG) solar–
thermal power plant (STPP) having only one feed water heater
(FWH). The major energy loss has been found to occur in condenser
followed by collector field. The exergy analysis shows that collector
field is main source of exergy destruction. The exergy loss in
condenser is insignificant, because in the condenser the low quality
energy is lost. Thus, the exergy analysis provides a more accurate
measurement of the actual inefficiencies in the system and the true
location of these inefficiencies. The results of exergy analysis of DSG
STPP point out that collector and receiver require improvement. To
reduce exergy loss in collector, material constraints play an
important role and hence, extensive work in this direction is to be
carried out to make STPP a real success. To reduce the exergy loss in
receiver of DSG STPP the temperature of water at inlet to row of
parabolic-trough collector must be optimum. Only marginally
change in efficiency has been observed by changing the bleed mass
fraction and bleed pressure of DSG STPP with single FWH and the
optimum bleed pressure has been found to be 4.1 bar with
maximum efficiency equal to 15.879%. The optimization has also been carried out by incorporating two and three FWHs. The
maximum efficiency equal to 16.134% can be achieved by using the
two FWHs without drip pump. It has been found that by using three
FWHs there is significant improvement in maximum efficiency
(16.606%). and for higher efficiency at least three FWHs are must.
Further enhancement in efficiency of DSG STPP is possible by
making provision for more number of FWHs.