Energy, exergy and exergoenvironmental assessments of waste heat operated basic and modified cogeneration systems for freshwater and hydrogen production

Abstract

In this study, thermodynamic and environmental assessments of waste heat driven cogeneration systems are carried out. The cogeneration systems include basic and modified configurations of Organic Rankine cycle (ORC), Reverse osmosis (RO) unit and Proton exchange membrane (PEM) electrolyser. The ORCs are aimed at transforming waste heat into power for the operation of a reverse osmosis (RO) unit and a proton exchange membrane (PEM) electrolyser, for generation of fresh water and hydrogen, respectively. The systems were simulated in engineering equation solver (EES). Among the studied configurations and working fluids, the findings demonstrate that the ORC configuration that combines both an internal heat exchanger and a mixing chamber (HMORC) and employing Isopentane as working fluid showed optimal performance, and showcasing energy and exergy efficiencies, and sustainability index values of 19.31%, 24.63%, and 2.033, respectively. Furthermore, this setup achieves maximum flow rates of 5.211 m³/h for fresh water and 2.737 kg/h for hydrogen. Moreover, The parametric study indicates that performance of the cogeneration systems improves with rise in evaporator pressure and drop in condenser pressure. The results highlight the promise of optimised system configuration for effective waste heat recovery and sustainable resource use.