Thermodynamic analysis and optimization of a solar-powered organic rankine cycle with compound parabolic collectors

The solar-powered Organic Rankine Cycle (ORC) could solve the energy crisis and achieve low emissions because it presents a high energy conversion efficiency for a low-temperature heat source, with little impact on the environment. This paper investigates a solar-powered ORC that applies a compound parabolic collector (CPC) and a thermal storage unit for collecting solar radiation and achieving the continuous system operation, respectively. According to the established mathematical model, the effects of thermodynamic parameters on system performance are analyzed. In addition, a multiobjective optimization is performed to find the optimal key parameters and obtaining the optimal system performance from both thermodynamic and economic perspectives by employing nondominated sorting genetic algorithm II (NSGA-II). The results reveal that increasing the turbine inlet pressure, thermal oil mass flow of vapor generator, and CPC and decreasing the cooling water temperature could improve system performance. The optimization results show that the optimum solution is obtained with an average net power output of 143.02 kW and a daily average exergy efficiency of 7.75% under the given conditions. The corresponding values of the selected decision variables - turbine inlet pressure, thermal oil mass flow of CPC, thermal oil mass flow of vapor generator, and terminal temperature difference of condenser - are 1,999.611 kPa, 12.00 kg·s-1, 5.97 kg·s-1, and 14.02 K, respectively.