Annual transient analysis of energetic, exergetic, and economic performances of solar cascade organic Rankine cycles integrated with PCM-based thermal energy storage systems

In this study, the annual transient analysis of the solar cascade organic Rankine cycle integrated with the phase change material (PCM) storage and parabolic trough collectors (PTC) has been conducted. The proposed system has been evaluated from energy, exergy, and economic points of view. Several PCMs, namely Isomalt, Adipic acid, Salicylic acid, Dimethylol propionic acid, A164, and KNO3-NaNO2-NaNO3 composition, have been compared to each other. Moreover, the effects of three different pairs of organic fluids, R245fa/R134a, R245fa/R500, and R245fa/R1234yf, have been examined on the system's performance. The annual investigation indicated that the closer the PCM melting temperature to the auxiliary heater setpoint temperature, the higher the solar fraction, exergy and energy efficiencies. Furthermore, the pair of R245fa/R500 had the best energy and exergy performances, which were 12.76% and 13.87%, respectively. The economic evaluation revealed that the case of R245fa/R500 combined with Dimethylol as the PCM thermal storage has the best economic performance with the NPV, LCOE, and PP of 186,622 $, 0.29 $/kWh, and 18 years, respectively. Also, the results of a sensitivity analysis showed that the NPV is extremely sensitive to the energy carriers prices and least sensitive to the PTC cost.