Exergoeconomic analysis and optimization of a solar-assisted integrated combined cycle with direct steam generation and organic Rankine cycle

This study investigates the design, analysis, and optimization of a novel integrated power generation system that combines a gas turbine cycle, a steam Rankine cycle, and an organic Rankine cycle (ORC), supported by a solar field and an auxiliary boiler. The motivation behind this work is to enhance overall energy and exergy efficiencies while reducing system costs and environmental impact in hybrid solar-fossil energy systems. The system is capable of generating 44.2 MW of net power, with the gas turbine acting as the primary energy source for the bottoming cycles. A detailed thermodynamic and exergoeconomic analysis was conducted using Engineering Equation Solver (EES) software, followed by a multi-objective optimization in MATLAB employing a genetic algorithm. The optimization aimed to simultaneously maximize exergy efficiency and minimize the total cost rate of the system. The results show that the combustion chamber, solar field, and auxiliary boiler are the major sources of exergy destruction. In the optimized configuration, the exergy efficiency improved from 46.79 % to 47.82 % (a 2.2 % increase), while the total cost rate decreased from $3511/hr to $3381/hr (a 3.7 % reduction). Additionally, the Levelized Electricity Cost (LEC) dropped from $0.0794/kWh to $0.0771/kWh. The payback period analysis indicates that the investment in the solar field can be recovered within 9.8 years. The novelty of this work lies in the integration of solar-assisted direct steam generation with a combined gas-steam-organic Rankine configuration, optimized through a multi-objective approach that balances efficiency and cost. • Integration of solar combined cycle, direct steam generation and organic Rankine cycle. • Auxiliary boiler supports feedwater heating when solar field temperature is insufficient. • Thermodynamic and thermo-economic analyses followed by genetic algorithm optimization. • Optimization boosts exergy efficiency by 2.2 % and cuts total cost rate by 3.7 %. • Levelized Electricity Cost drops by 2.9 %, with solar field payback in 9.8 years.