Integration of Direct-Contact Membrane Distillation with Flat-Plate Solar Collector versus Proton-Exchange Membrane Fuel Cell: Dynamic Simulations and Comparative Analysis

Abstract

Two hybrid systems, i.e., an integrated flat-plate collector (FPC) and direct contact membrane distillation (DCMD) system and an integrated proton exchange membrane fuel cell (PEMFC) and DCMD system, are proposed to mitigate the negative effects of conventional heat supply methods such as burning fossil fuels. In addition to benefiting from renewable and clean sources, harvesting the waste heat of PEMFCs helps enhance its total efficiency. The proposed FPC-DCMD and PEMFC-DCMD hybrid systems were simulated to evaluate their performance on representative days in the city of Wuhan, China. A new approach that combines two programming environments is demonstrated, i.e., a programmed engineering equation solver code for DCMD modeling and the TRNSYS version 16.0 (2016) software for the dynamic simulation of hybrid systems. The driving force required by DCMD (8,457 kJ/h) is supplied using the two proposed heat supply scenarios to produce 77.4 kg/m2 h of freshwater. The results of the integrated FPC-DCMD system show that the maximum amount of energy supplied by the FPC are 5,919 kJ/h and 2,490 kJ/h at 2 PM during the summer and winter solstices, whereas the amounts of energy provided by the auxiliary heater are 2,537 kJ/h and 5,967 kJ/h, respectively. The average solar fraction at the summer solstice was 19%, whereas at 2 PM, the integrated FPC-DCMD system can provide approximately 70% of the total energy required at the maximum mode. In another scenario, 6,185 kJ/h of the total energy required for DCMD was supplied by harvesting the waste heat of the PEMFC, whereas the rest was provided by an auxiliary electric heater. It was found that 73% of the total energy required by DCMD to increase the feed water inlet temperature from 25°C to 80°C was obtained by harvesting the waste heat of the PEMFC.