Design Point and Off-Design Simulation of a Gas Turbine–Solar Combined Cycle

Document Type : Original Article

Author
Hamoon Pourmirzaagha
Assistant professor, Department of Mechanical and Aerospace Engineering, Ram.C., Islamic Azad University, Ramsar, Iran
10.22034/stme.2025.551028.1178
Abstract
The integration of solar energy into gas turbine cycles, as an emerging approach, can enhance system efficiency while reducing fossil fuel consumption. In this study, a single-shaft solar-assisted gas turbine power plant is simulated under both design-point and off-design conditions and analyzed from energy and exergy perspectives. The model incorporates a compressor, turbine, combustion chamber, heat exchanger and solar receiver. The effects of key parameters, including compressor pressure ratio, turbine inlet temperature, and solar irradiance, are systematically investigated. The results demonstrate that the utilization of solar energy significantly reduces fuel consumption and decreases exergy destruction in the combustion chamber. Off-design analyses indicate that variations in rotational speed and solar irradiance have a substantial impact on power output, fuel consumption, and overall system efficiency. An increase in compressor speed leads to a higher air mass flow rate and consequently requires a greater fuel input to maintain an appropriate air–fuel ratio. Although this results in higher power output, it is accompanied by increased fuel consumption and a reduction in thermal efficiency. Therefore, while solar integration primarily improves efficiency and reduces primary energy consumption, off-design operation reveals important trade-offs between power augmentation, efficiency degradation, and fuel usage.
Keywords
Solar energy
Gas turbine–solar power plant
Energy and exergy analysis
Design point
Off-design conditions
Subjects
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  • Receive Date 06 October 2025
  • Revise Date 02 November 2025
  • Accept Date 29 November 2025
  • First Publish Date 29 November 2025
  • Publish Date 23 July 2026