Experimental study and prospect analysis of LiBr-H2O reverse electrodialysis heat engine

Abstract

Reverse electrodialysis heat engines are a theoretically efficient technique to harvest <100 °C low-grade heat and convert it into electric power. However, the feasibility, technical bottleneck, and application potential of such a concept are unclear because of the experimental study lack. This work experimentally investigates its performance and indicates current technical bottlenecks. After that, a prospect analysis is conducted based on sensitivity analyses to exhibit its potential assuming those bottlenecks are solved. Results show that the regeneration sub-unit performance is close to the theoretical values. The low permselectivities of ion exchange membranes in the reverse electrodialysis sub-unit constrain the performance of the heat engine. Developing high permselectivities of ion exchange membranes under high concentration conditions should be the priority. The prospect analysis indicates that energy and exergy efficiencies of reverse electrodialysis heat engines can reach 2.6% and 19%, respectively, when generation temperatures are 70 °C. It is hoped that this work clarifies that low permselectivities are current technical bottlenecks and provides a guideline for the following research.