Pressurised alkaline electrolysers

ALK electrolysers are the most mature technology and are already at the commercial stage. They have a simple stack system design and are relatively easy to manufacture. Their capital costs are lower than those of other electrolyser technologies (see Table 9.3). While ALK electrolysers can operate at either atmospheric pressures or high pressures (up to 30 bar), high-pressure electrolysers can be ramped up and down much faster (in less than a minute) than those operating at atmospheric pressure, which take several minutes to ramp up or down. High-pressure ALKs are therefore better at following fluctuations in wind and solar generation.

Given that pressurised ALK electrolysers can rapidly follow fluctuations in wind and solar production, its smart integration would facilitate the integration of variable renewable sources. ALK electrolysers also have lower investment costs than other technologies, and have been certified to provide primary reserves to the power system (IRENA, 2020c).