Thermoeconomic optimization of a novel high-efficiency combined-cycle hybridization with a solar power tower system

Today, the international community is obligated to utilize renewable energy due to accelerated energy consumption on the one hand and the necessity of environmental pollution reduction, on the other hand. Meanwhile, the Solar Power Tower (SPT) is at significantly optimum conditions for integration with conventional fossil power plants due to reaching temperatures of up to 1200 degrees C and a high-power generation capacity. The present paper demonstrates the optimal layout of the new hybrid-cycle power generation section with SPT. The Heliostat field was optimized as a transient optical model at all hours of the year by considering the city of Seville as a case study using the System Advisor Model (SAM). Subsequently, the cycle's thermo-economic model was developed using Engineering Equation Solver (EES) to minimize the Levelized Cost Of Electricity (LCOE). In the following, four fluids of n-Butane, R245fa, n-Pentane, and R123 were utilized for the final analysis as a downstream fluid. Through this process, the appropriate operating fluid was selected. The study results demonstrate an increase in the efficiency of the novel proposed cycle layout compared to a solar power tower power plant with standard pressurized air-fluid; moreover, it reduced fuel consumption, CO2 emission, and LCOE. The maximum efficiency and the minimum LCOE were53.25% and 61.8 $/MWh, respectively. The n-Pentane fluid was recognized as the most appropriate fluid for the downstream cycle. Due to the optimization of solar parts, the number of heliostat field mirrors were 889, with a total area of 131,525 m(2) and a central tower height of 105.87 m. The novel presented cycle layout solves a portion of the pressurized air receiver limitations, enabling access to higher efficiency and lower LCOE with the real payback time (RPBT) of 3.876 years, the annual solar share of 23.1%, and reduction of CO2 production by 33,426 ton/year. Consequently, this study's proposed cycle layout signifies a promising future for using SPT with high efficiency and better environmental and economic conditions.