Multi-criteria assessment of an auxiliary energy system for desalination plant based on PEMFC-ORC combined heat and power

Abstract

A novel auxiliary energy system for desalination plant based on proton exchange membrane fuel cell (PEMFC)-organic Rankine cycle (ORC) combined heat and power is proposed in this paper. A thermodynamic model of the system is established, and a dynamic net present value (NPV) calculation method under the context of time-of-day tariff is designed. The system output power, economic and environmental evaluation indicators under steady-state and dynamic operation are optimized using NSGA-III and TOPSIS. The parameters sensitivity analysis shows increasing the ORC system saturation pressure and the auxiliary equipment efficiency is beneficial to increase output power and reduce indirect CO2 mass specific emission (MSE). However, excessive pressure and efficiency will lead to a significant decrease in NPV. Under steady-state optimization, the electrical power of the system is increased by 20.1 % compared to the conventional PEMFC system. And when the proposed system operates dynamically, the single-day power generation is 1620 kWh, which is 9.31 % higher than the PEMFC system. The single-day heated seawater production is 110.1 tons and the MSE is 0.105 kg/kWh. The NPV decreases significantly, but the system can pay for itself over its lifetime. Therefore, the proposed system has thermodynamic and economic performance advantages over the conventional PEMFC system.