Performance evaluation of the combined helium Brayton cycle and organic Rankine cycles for solar power tower application—A comparative study

Solar energy is the prime renewable energy source to provide the carbon-free power. However, various irreversibilities are associated with the solar power tower (SPT) system, and they cannot be avoided. Therefore, to enhance the performance of the solar power plant, in this work, four configurations of the combined cycles have been considered for harvesting the solar heat from the SPT system, and the performance of all the considered power systems was compared with the SPT-based conventional helium Brayton cycle (HBC) system. These four proposed combined cycles used HBC as the topping cycle and basic organic Rankine cycle (ORC), recuperative ORC, regenerative ORC, and regenerative-recuperative ORC (RRORC) as bottoming cycles separately. Energy and exergy analyses of the proposed power generation systems were performed based on numerical technique using the computational software engineering equation solver. It was concluded that the SPT-HBC-RRORC system was considered the best-performing power generation system among the other considered power systems. The SPT-HBC-RRORC system achieved energy efficiency, exergy efficiency, and net work output, respectively, as 7.69%, 8.09%, and 21.69% higher than that of the conventional system (SPT-HBC). However, the SPT-HBC-RRORC system achieved 5.44%, 5.08%, and 18.51% higher energy efficiency, exergy efficiency, and net work output, respectively, than that of the SPT-HBC-basic ORC. Therefore, the SPT-HBC-RRORC system is far better than the conventional SPT-HBC system. The parametric analysis indicates that the parameters related to the solar subsection significantly influence the power generation unit's performance.