# Energy and Exergy Analyses of an Existing Solar-Assisted Combined Cycle Power Plant
## 5 Conclusions  
The objective of this study was to investigate the performance of an existing 135 MW ISCC power plant in Kureimat. The ISCC power plant was thermodynamically studied under Kureimat climatic conditions. Energy and exergy analyses were performed for the ISCC power plant as a whole at different ambient temperatures (5, 20, and 35 \({}^{\circ}\)C) and different solar heat inputs (0, 50, 75 MW). Moreover, the exergy destruction and the exergetic efficiency for the main components of the ISCC power plant were calculated and investigated regarding the influence of the ambient temperature and the solar heat input to identify the causes and locations of the highest thermodynamic irreversibility. The integration of solar energy into a natural gas CCPP was analyzed as a power-boosting mode. The main conclusions of this study are as follows:  
* The solar field has the lowest exergetic efficiency (17.8%), followed by the condenser (42.2%), at ambient temperature 20 \({}^{\circ}\)C and solar heat input 50 MW.
* The exergy destruction in the solar field is the largest part of the exergy destruction in the ISCC power plant (52.9% at ambient temperature 20 \({}^{\circ}\)C and solar heat input 50 MW).
* The thermal efficiency and the exergetic efficiency of the ISCC decrease with increasing solar field thermal input, where it has its highest values (51.14% and 49.18%, respectively) at no solar field thermal input (combined cycle regime) and ambient temperature 5 \({}^{\circ}\)C.
* The thermal efficiency and the exergetic efficiency of both the ISCC and the combined cycle (i.e., at no solar field heat input) decrease with increasing ambient temperature at different solar heat inputs (0, 50, 75 MW). This is due to the decrease of the exergetic efficiency of the gas turbine, the solar field, the condenser, and the HRSG with increasing ambient temperature.
* The integration of a solar field with a combined cycle (i.e., ISCC) reduced the thermal and exergetic efficiencies of the power plant under the combined cycle regime due to the low thermal and exergetic efficiencies of the solar field because the solar fuel cost was considered in this study.
* The target of the ISCC power plants is not to increase the overall thermal efficiency of the Brayton cycle, like the combined cycle, but to increase the economic feasibility of solar power plants. Elimination of the thermal storage system reduces the cost of the power plant [24; 25; 26]. So, this integration of a solar field is recommended regarding the given challenges for the electricity market with the continuing expansion of intermittent renewables.  
[PERSON] is responsible for the technical, analysis, writing and funding acquisition parts. [PERSON] has contributed strongly to the design and preparation of the investigation. [PERSON], [PERSON], [PERSON], [PERSON], and B.E. discussed the formulation and the results and contributed to the review and editing of the manuscript. All authors have read and agreed to the published version of the manuscript.  
The authors appreciate the Technical University of Darmstadt for funding the publication costs for the article in an open-access journal. The corresponding author appreciates the Egyptian Government for offering the PhD scholarship.  
The authors declare no conflict of interest.