E-bypass separator enabling electrolysis under very low load and very high pressure.

Hydrogen can be extracted from water by means of alkaline water electrolysis, producing simultaneously hydrogen and oxygen gases. The generation of hydrogen in electrolysers requires high energy input which is further increased due to a separate compression step. This is needed to bring the hydrogen pressure up to a high level (100-800 bar), required for storage. By producing the hydrogen in the electrolyser under high pressure, the need for an external hydrogen compressor is eliminated. The limiting factor of pressurized alkaline water electrolysis cells is often a small operational window (20-100 %) due to a generally low gas quality, typically due to the high pressure conditions.  Under these circumstances it is very difficult to avoid cross contamination of the hydrogen and oxygen gasses.

VITO solution

VITO developed a three-element separator that solves the above mentioned shortcomings. This so-called “e-bypass” separator comprises two separator layers with a free electrolyte bypass channel in between. This enables flushing fresh electrolyte from this channel towards the anode and cathode compartments during electrolysis operation, preventing the diffusion of dissolved gases to the other cell space. Consequently, the hydrogen gas that is dissolved in the catholyte compartment as an effect of the high pressure is completely prevented from diffusing to the anolyte compartment. The third cell space (between the two separator layers) and the electrolyte flow out of the e-bypass are the key elements.

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