Techno-economic modelling of a hydrogen-electrodialysis (HED) unit for the simultaneous production of freshwater and hydrogen

Abstract

Green hydrogen has been proposed as the most promising future energy carrier, however, its cost is still higher than the grey hydrogen from steam reforming. Furthermore, there is an increasing freshwater demand which must be covered, and desalination is the most promising option to tackle this issue. The present work proposes a new technology named hydrogen electrodialysis (HED) able to produce simultaneously freshwater and a worthy amount of hydrogen. A conventional electrodialysis (ED) stack consists of a repetition of membranes and spacers sandwiched by two electrodes only, whose cathode can intrinsically guarantee a low hydrogen production. Conversely, the proposed innovative idea of HED is to insert additional shared electrodes in the cell package to enhance the hydrogen productivity, without changing the freshwater production. A suitable techno-economic model is developed and adopted to investigate a 1000 cell-pairs electrodialysis HED unit devoted to desalinating 5 g L−1 brackish water to 0.5 g L−1. Preliminary results show an attractive minimum levelized cost of hydrogen of 3.43 € kg−1H2, proving that there is a large room for future more-in-depth studies.