# Energy and Exergy Analyses of an Existing Solar-Assisted Combined Cycle Power Plant
## 4 Results and Discussion
### The Overall Thermal Efficiency of the ISCC Power Plant  
The overall thermal efficiency of the ISCC power plant in Kureimat at different ambient temperatures for solar heat inputs of 0 MW, 50 MW, and 75 MW is shown in Figure 2.  
The overall thermal efficiency of the power plant at different ambient temperatures for solar heat inputs. The overall thermal efficiency of the power plant at different ambient temperatures for solar heat input equal to 0 MW, which represents the combined cycle regime, is shown in Figure 2. At no solar heat input (combined cycle regime), the thermal efficiency of the plant was reduced from 51.14% at ambient temperature 5 \({}^{\circ}\)C to 48.67% at 35 \({}^{\circ}\)C.  
Figure 2 shows that the overall thermal efficiency of the ISCC decreases with increasing ambient temperature at different solar heat inputs (0, 50, 75 MW), and that appears most distinctly at ambient temperature 35 \({}^{\circ}\)C. This may be due to the direct effect of the ambient temperature increase on the efficiency of the condenser and the gas turbine: the condenser and gas turbine efficiency decreases with increasing ambient temperature. The overall thermal efficiency of the ISCC is lower than the overall thermal efficiency of the plant in the combined cycle regime in all cases (different solar heat inputs and ambient temperatures). Figure 2 shows that the integration of the solar field with the combined cycle (i.e., ISCC) reduced the thermal efficiency of the power plant at all ambient temperatures. This may be because the target of the ISCC is not to increase the overall thermal efficiency of the Brayton cycle, like the combined cycle, but to increase the economic feasibility of the solar power plants. Elimination of the thermal storage system reduces the cost of the power plant [24; 25; 26]. Figure 2: The overall thermal efficiency of the power plant at different ambient temperatures for different solar heat inputs. Exergy Destruction in Each Component of the ISCC as a Percentage of the Total Exergy Destruction in the Whole ISCC  
The exergy destruction in each component of the ISCC and the exergy destruction in the whole ISCC were calculated for different solar heat inputs and ambient temperatures 5 \({}^{\circ}\)C, 20 \({}^{\circ}\)C, and 35 \({}^{\circ}\)C.  
The percentages of exergy destruction in each component of the ISCC out of the total exergy destruction of the power plant at different ambient temperatures for solar heat inputs 0 MW, 50 MW, and 75 MW are shown in Figures 3-5, respectively. Figure 4: Percentage of exergy destruction in each component of the ISCC out of the total exergy destruction of the plant at different ambient temperatures for solar heat input equal to 50 MW. Figure 3: Percentage of exergy destruction in each component of the ISCC out of the total exergy destruction of the plant at different ambient temperatures for solar heat input equal to 0 MW. It is revealed in Figure 3 that the combustion chamber (CC) has the highest percentage of exergy destruction, and this value is higher in the combined cycle regime than in the ISCC regime. This may ensure that the solar field has high irreversibility weight, which affects the percentage of exergy destruction in the combustion chamber compared to its value in the combined cycle regime. However, Figure 3 shows that the exergy destruction in the combustion chamber decreases slightly with the increase of the ambient temperature under the combined cycle regime (0 MW solar heat input). It can be observed from Figures 4 and 5 that the exergy destruction in the combustion chamber decreases significantly with the increase of the ambient temperature in the case of ISCC. This may account for the weight of exergy destruction in the solar field. Also, the exergy destruction in the solar field increases with increasing ambient temperature, in contrast to the exergy destruction in the combustion chamber. Figures 3-5 show that the combustion chamber and the solar field have the highest exergy destruction among all the subsystems.