8. Conclusions

In conclusion, PEM water electrolysis is a technique that breaks water down into molecular hydrogen and oxygen at temperatures ranging from ambient to around 150°C. It involves using an acidic electrolyte confined within an ionomer polymer membrane. Although thin (typically between 50 and 200 µm), the membrane (when properly supported) can operate at high operating pressures of several tens of bar and even operate under pressure differential (typically 20 bar). The machines currently available cover an electrical power range of up to several tens or even hundreds of MW. This type of technology is capable of operating satisfactorily and sustainably when the incident electrical power is highly transient (renewable energy sources or service to the electrical grid).