Investigation of gas purity in pressurized alkaline water electrolysis

Investigation of gas purity in pressurized alkaline water electrolysis

The aim of this project was the experimental and theoretical investigation of gas purity in alkaline water electrolysis under elevated system pressures and relevant operating conditions. For this purpose, both steady-state and dynamic experiments were carried out under variation of current density, system pressure, electrolyte concentration as well as electrolyte volume flow and electrolyte flow concepts to evaluate the product gas quality and system behavior. With the help of these experimental results, it was possible to extend an existing process model for alkaline water electrolysis by dynamics and pressure influence, so that the evaluation of dynamic operating concepts for the extension of the part-load range of alkaline water electrolyzers was possible. It was found that the electrolyte volume flow rate has a very large influence on the resulting product gas quality. Both alternating operation between mixed and separated electrolyte cycles and a reduced electrolyte volume flow rate were successful concepts for reducing gas contamination during part-load operation. In addition, pre-commercial separators were compared with the current state of the art in terms of product gas permeability and ohmic voltage losses in cooperation with other European research institutes and a material manufacturer. For this purpose, both physical and electrochemical tests were carried out with the materials. This study showed that thin separators are a good alternative for classical alkaline water electrolysis, since the cell voltage can be significantly reduced with them, thus saving operating costs in the form of electricity costs.

Jörn Brauns, M. Sc.

Scientific Assistant

Phone: +49 5323 72-2473

Room 120, Leibnizstraße 19
38678 Clausthal-Zellerfeld