Energy and Exergy Analysis of a Parabolic Trough-Assisted Brayton–Rankine Hybrid Power Cycle under Tropical Climatic Conditions

Abstract

Integrated solar combined-cycle (ISCC) plants offer a low-risk route to cleaner generation in regions with a strong solar resource. This study develops and validates a thermodynamic model of a parabolic trough-assisted hybrid plant that couples a Brayton-cycle gas turbine block (2 × 40 MWe) with a Rankine-cycle steam turbine (80 MWe) through two heat recovery steam generators and a solar steam generator. Site-specific radiation data for Kalaburagi, Karnataka, drive a 183,120 m² trough field. Each component was represented by mass and energy balances, and the integrated model was used to evaluate solar-field output, steam-cycle and overall thermal efficiencies, solar-to-electric conversion and a second-law (exergy) measure of performance. The model was validated against hourly net output measured at the Hassi R'mel ISCC plant. Over 24 h the present model reproduced the measured energy within +0.98%, with a mean absolute percentage error of 3.34% and a normalised RMSE of 4.1%, against 6.39% and 6.8% for a reference model. The combined-cycle-mode thermal efficiency reached 67%, corresponding to an exergy efficiency of about 64%, while the solar field operated at an exergy efficiency of 21–28%. The framework provides a robust basis for assessing solar-assisted combined cycles in high-irradiance tropical climates.