Experimental performance of a low−grade heat driven hydrogen production system by coupling the reverse electrodialysis and air gap diffusion distillation methods

Abstract

The reverse electrodialysis (RED) heat engine is an emerging and burgeoning technology used to convert low-grade heat (LGT) to electrical energy. This study designed and built a lab-scale prototype of integrating the RED and air gap diffusion distillation (AGDD) methods to convert LGT (as low as 60℃) to hydrogen, and the performances (the hydrogen production, thermal regeneration characteristic, and system efficiency) of the RED−AGDD integration system were experimentally investigated. The results indicate that the maximum net output power for hydrogen production is determined by the maximum current. The maximum net output power is 0.53 W when the HC−LC feed solution pair is 4−0.05 M. Either the excessively high or low salinity gradient energy is detrimental to the energy conversion efficiency of the RED−AGDD integrated system. In this study, the system efficiency reached its maximum value of 0.014% at the feed solution pair is 5−0.20 M. It is also observed the thermal separation effect of the AGDD unit is improved by increasing the solution temperature and flow rate, but weakened by increasing the concentration of separated solution. The effect mechanisms of the vital operating parameters on system performances are analyzed, providing guidance for the practical application of RED heat engine for hydrogen production.