There are mainly two electrolyzer technologies available today: polymeric and alkaline. Polymeric electrolyzers, although quite efficient, are limited to powers of the order of kWs to hundreds of kWs, whereas alkaline electrolyzers range between a few kilowatts to several megawatts. Wind farms are in the range of several megawatts (typically 20-50 MW), and nowadays, there are only a few electrolyzer manufacturers, one of them being IHT (Switzerland), with the know-how and the capability of manufacturing such high capacity electrolysis units. Moreover IHT electrolysis units operate at high pressure (32 bar), the highest ever achieved for bipolar technology. High pressure electrolyzers, high meaning over 32 bar, show many advantages, such as savings in the compression unit downstream of the electrolyzer and faster reactive capacity of the stack and enabling longer standby times (required for intermittent operation and low capacity factor). Currently, the most interesting, and perhaps unique, electrolysis technology that can match the expectations of renewable hydrogen pressure production belongs to IHT, who takes part in this proposal.
The principle of alkaline water electrolysis is that water is reduced to hydrogen gas and two hydroxyl ions at the cathode. The hydrogen escapes from the surface of the cathode and the hydroxyl ions migrate under the influence of the electrical field from the cathode to the anode through the porous diaphragm to the anode, where they are oxidized to oxygen.