Thermo-economic optimization of organic Rankine cycle with steam-water dual heat source

Abstract

Dual-loop ORC (D-ORC) and single-loop ORC (S-ORC) systems can be employed to steam-water waste heat recovery. The maximum net output power and minimum electricity production cost (EPC) are considered as optimization objectives. To optimize the thermo-economic performance and obtain the Pareto front, non-dominated sorting genetic algorithm-II is employed, and the decision is made by TOPSIS and entropy weight method (EWM). The results show that the EPC of the S-ORC system is lower than that of the D-ORC system under any heat source condition. However, the net output power of the S-ORC system exceeds that of the D-ORC system when the steam mass flow rate and hot water inlet temperature are 10 kg/s and 110 °C, respectively. When the steam mass flow rate or the hot water inlet temperature is higher, the S-ORC system has more distinct advantages in terms of thermo-economic performance. When the working fluid at the outlet of hot water preheater of the S-ORC system is in a two-phase state, the optimal steam outlet pressure is invariably the lowest for operation, and cost can be reduced by removing the steam preheater. In the D-ORC system, the optimal steam outlet pressure is consistently the lowest allowable pressure.