## 4 Results and Discussion
### GC (Gas Cycle) and CC (Combined Cycle) Results  
Figure 8 demonstrates the monthly average of net electricity generation in four types, which are GT, GT + HRSG, GT + HSR, and GT + HRSG + HSR. For the GT type, the average of net electricity generation changed from 8.54 MW in July up to 9.51 MW in January. As can be seen, the electricity generation of GT diminished in warm months of a year. As known, in gas cycles, the volume flow rate of a cycle was constant while the gas density was reduced in warm months of a year, which ended up with lower electricity generation. For the GT + HSR type, the monthly average of net electricity generation was lower than the GT type. Since the HSR was employed to preheat the inlet air of the combustion chamber, the mass flow rate of the inlet fuel of the combustion chamber decreased, followed by a decrement of the inlet mass flow rate of the gas turbine, which led to less electricity generation. Clearly, for the GT + HRSG type, because of the heat recovery used for the Rankine  
Figure 7: Monthly average absorbed heat rate by the solar receiver, heat loss, and net heat gain in different months of a year. cycle significantly higher electricity generation can be achieved. Hence, for the GT + HRSG type, the variations of net electricity generation ranged from 14.9 MW in July up to 15.87 MW in January. Furthermore, when adding the HSR cycle to the GT + HRSG type a slight reduction could be seen, which is justified similarly to adding HSR to the GT type mentioned above. The monthly average of energy efficiencies of the four mentioned types was exhibited in Figure 9. By comparing the GT cycle and the GT + HSR system, although the monthly average net electricity production of GT + HSR type was lower than the GT type according to Figure 8, the monthly average energy efficiency was higher for the GT + HSR type. This phenomenon is because that by employing the HSR cycle less of a fuel mass flow rate is required in the gas cycle leading to a reduction in the denominator that has a dominance effect in comparison to a decrease of numerator, which is the net electricity generation. Definitely, for the combined cycle or GT + HRSG type, the energy efficiency is higher than GT type due to higher net electricity generation. In warm months of a year, a slight decrease in both GT and GT + HRSG types was observed, which is because of a reduction in the gas density in these months that diminishes the net electricity generation. In the GT + HSR type, for May, June, and July, the energy efficiency was higher than the GT + HRSG type because of an increase of the average absorbed heat rate by the solar receiver in these months. Additionally, the GT + HRSG + HSR or the whole system had a significant energy efficiency between 61% and 93%, particularly in warmer months such as May, June, and July that the energy efficiency maintained being more than 87%. Figure 10 reports the monthly average of exergy efficiency of four types of GT, GT + HRSG, or the combined cycle, GT + HSR, and GT + HRSG + HSR, or the whole system. The results of monthly average exergy efficiencies were similar to the monthly average energy efficiency presented in Figure 9 with slight changes. Exergy efficiencies of all four types were slightly lower than their energy efficiencies, which were because of the higher value of fuel-specific exergy in comparison to LHV of the fuel in the denominator of the energy and exe  
Figure 8: Monthly average of net electricity generation in four types of GT, GT + HRSG, GT + HSR, and GT + HRSG + HSR. In Figure 11, a new concept for energy and exergy efficiencies of the GT + HRSG + HSR was proposed that includes solar radiation. For the energy efficiency of system (b), the solar energy radiation input in Equation (17) was added to the denominator of the equation. Additionally, for the exergy efficiency of this system, the exergy rate of solar energy input presented in Equation (28) was added to the denominator of the exergy efficiency equation.