Performance analysis, multiobjective optimization and working fluid selection for a DPORC system with geothermal source shunting

A dual-pressure ORC system with geothermal source shunting (GSS-DPORC) is proposed. The geothermal source at the outlet of the high-pressure evaporator is shunted so that one portion of it heats the high-pressure preheater and the other portion heats the low-pressure evaporator. Thermodynamic, economic, and environmental performance of the GSS-DPORC system are examined and contrasted with those of the DPORC system under different working fluids and conditions. Further, the EW-GRA-TOPSIS comprehensive evaluation method, which picks the optimal working fluid while attaining the best working conditions, is proposed. It fully assesses the working fluid based on the multiobjective optimization results generated by NSGA-II. The results indicate that the performance metrics of the GSS-DPORC system are superior to those of the DPORC system when the geothermal source inlet temperature is in the range of 373–423 K, the evaporation pressure of high-pressure stage ranges from 740 kPa to 1610 kPa, and the evaporation pressure of low-pressure stage ranges from 540 kPa to 1020 kPa. R227ea has better thermodynamic and economic performance, and R245fa has better economic performance. The R227ea has the best overall performance following a thorough review using the EW-GRA-TOPSIS method, while the R245fa has the poorest performance.