Exergoeconomic, thermodynamic and working fluid selection analysis of a novel combined Brayton cycle-regenerative organic Rankine cycle for solar application

As previously mentioned, the solar power tower (SPT) system has a lot of irreversibilities that are difficult to avoid. Therefore, a new, effective power producing unit needs to be constructed in order to enhance the SPT plant's performance. The current study established an entirely novel combined cycle for the SPT plant. The regenerative organic Rankine cycle (RORC) was used for waste heat recovery, and the helium Brayton cycle (HBC) was considered as the topping cycle. Energy, exergy, and exergoeconomic assessments of the proposed power plant, was performed numerically using engineering equation solver software. Additionally, parametric analysis was carried out along with the short working fluid selection analysis. It was concluded that thermal, exergy efficiency, and power output of the proposed power plant (SPT-HBC-RORC) were improved by 19.97 %, 19.95 %, and 19.96 %, respectively, compared to the conventional solar plant (SPT-HBC). However, plant total cost was increased by 11.61 %. Finally, the proposed power plant yielded power output, exergy efficiency, thermal efficiency, and levelized cost of electricity (LCOE) values of 19,918 kW, 41.36 %, 38.62 %, and 43.23 $/MWh, respectively. The fluid R1233zd(E) was recommended as the best-performing fluid thermodynamically. The suggested combination cycle outperformed the Rankine cycle and supercritical CO₂ cycle power production systems based on SPT, according to a comparison with earlier research. Additionally, the proposed combined cycle is more efficient than the SPT-based combined HBC-basic ORC system.