Working fluid selection, exergy, energy and exergoeconomic assessment of a novel combined Brayton cycle and regenerative-recuperative organic Rankine cycle for concentrated solar power application

The current study created the novel integrated system for solar power tower plants to generate power efficiently. In this work, the helium Brayton cycle was considered as topping cycle, and the recuperative-regenerative organic Rankine cycle was incorporated as the bottoming cycle for waste heat recovery. The energy efficiency, exergy efficiency, exergoeconomic analysis, and working selection of the proposed system were conducted using engineering equation solver software. Additionally, a parametric analysis was conducted to explore the impact of key factors on the performance of the proposed plant. It was concluded that implementation of the recuperative-regenerative organic Rankine cycle in the conventional plant (solar power tower-based helium Brayton cycle) increased energy and exergy efficiency by 23.88% and 23.91%, respectively. However, total plant cost was improved by 14.49% only. Finally, the proposed solar power plant obtained the energy efficiency, exergy efficiency, and levelized cost of electricity values of 38.22%, 40.93%, and 0.01457 $/kWh, respectively. The fluids R1224yd (Z) and n-pentane were suggested to be the best fluids thermodynamically and economically, respectively. Parametric analysis revealed that the solar parameters and compressor pressure ratio much affected the plant performance. A comparison with prior studies shows that the present novel system performed better than Rankine and supercritical CO2-based power generation systems.