Reverse electrodialysis heat engine for sustainable power production

Abstract

Reverse Electrodialysis Heat Engine (REDHE) is a promising technology to convert waste heat at temperatures lower than 100. °C into electric power. In the present work an overview of the possible regeneration methods is presented and the technological challenges for the development of the RED Heat Engine (REDHE) are identified. The potential of this power production cycle was investigated through a simplified mathematical model. In the first part of the work, several salts were singularly modelled as possible solutes in aqueous solutions feeding the RED unit and the corresponding optimal conditions were recognized via an optimization study. In the second part, three different RED Heat Engine scenarios were studied. Results show that power densities much higher than those relevant to NaCl-water solutions can be obtained by using different salts, especially those based on lithium ion (i.e. LiBr and LiCl). Results on the closed loop show efficiencies up to about 15% corresponding to an exergetic efficiency of about 85%, thus suggesting that the RED Heat Engine could potentially be a promising technology, with applications mainly in the industry where low-grade heat that has no alternative use can be converted into electricity.