(d) (e)
Figure 6. Computed performance: a) Steam generated; b) Steam power
turbine output; c) ISCC output; d) ISCC efficiency; e) Solar electric
ratio
In order to estimate the sensitivity of ISCC power plant vis-à-vis the
ambient temperature through the whole year; the average ambient
temperature of each month (Table 12) is introduced. Also, the values of
DNI were evaluated for monthly periods based on the daily average values
which were averaged over one month. The obtained results are shown in
Fig. 7 based on monthly average ambient temperatures during days. As
shown, the output and thermal efficiency of ISCC plant exhibit a drop as
the ambient temperature gets to its highest value. If the plant works as
a conventional CC there is a significant drop in the output around 1 MW
compared to ISCC and this is explained by the negative impact of high
ambient temperature on GT. The slight decrease in performance of ISCC in
hot periods is explained by the advantage of converting solar energy in
producing additional steam in HSSG. Fig. 7(a) and Fig. 7(b) reveal that
the additional steam generated by coupling the CC with the solar field
compensates for the loss in power during the hot days, and hence the
solar integration with CC is a good solution. It can be concluded that
during high ambient temperatures coinciding with the period of higher
normal radiation, the steam produced by the solar collectors alleviated
the drop in electricity production by CC plants during the peak demand
periods and improved the overall efficiency. Fig. 7(c) displays the
impact of ambient temperature on the produced electricity by the solar
field as quantified by the solar electric ratio which seems decreasing
slightly with the ambient temperature such as the case during the
summer.
Fig. 8 displays the response of ISCC plant to the variation in the
ambient temperature during nights or cloudy periods depicted in Table
13. As shown the power output drops significantly from cold to hot
periods such as in summer. Since ISCC works as CC and due to negative
impact of ambient temperature the power drops for about 1 MW (Fig. 8(a))
as well as the thermal efficiency about 0.3 % as depicted in Fig. 8(b).
Table 12. Average ambient temperatures during the day [32]