Exergoeconomic analysis and optimization of a Gas Turbine-Modular Helium Reactor with new organic Rankine cycle for efficient design and operation

Gas Turbine-Modular Helium Reactor (GTMHR) is a promising option to meet today's soaring energy demand. A GTMHR combined with organic Rankine cycles (ORCs) can deliver higher performance. This paper presents an exergoeconomic optimization for a combined system comprising a GTMHR and an ORC where the ORC recovers the GTMHR waste thermal energy. The system performance is optimized using a simulation-based optimization method with simultaneous determination of the design parameters as well as selection of the components and their respective compositions for the ORC working fluid. A parametric study is performed to study the effects of the key design parameters on the system performance. Moreover, an off-design simulation procedure is proposed, and the system off-design performance is analyzed. The results show that R134a (100%), R22 and R143a (11.27% and 88.73%), and R134a and R152a (54.54% and 45.46%) are the best ORC working fluid for low, medium, and high helium temperature cases, and their minimum levelized cost per unit exergy are 8.449 $/GJ, 8.116 $/GJ, and 7.862 $/GJ, respectively. Furthermore, helium temperature and pressure ratio are found to have the most significant influences on the system performance. Finally, it is observed that a combined system with higher design parameters exhibits better off-design performance, namely higher power output and efficiency. Therefore, the GRMHR-ROC system should be designed with a relatively high helium temperature if allowed.