The project PRETZEL has the following objectives:

  1. Develop and manufacture high pressure polymer electrolyte membrane electrolyzer (PEMEL) to operate at increased temperatures.
  2. Develop and manufacture the high pressure PEMEL stack based on the novel principle of hydraulic compression.
  3. Set-up and undertake continuous procedures to evaluate the development process through all phases against PRETZEL specifications.
  4. Integrate the innovative PEMEL stack into a high pressure PEMEL test facility and validate the overall performance and operational criteria.
  5. Disseminate and exploit the innovations in PRETZEL in order to prepare the market penetration of this new technology.

A central objective of this project is the development of a novel PEMEL system with a maximum 25 kW electrical power consumption that generates 4.5 mh-1 H2 at rated power, at an output pressure of 100 bar and feed water temperature of maximum 90 °C.

At the system level, the specific energy demand at rated production rate will be below 25 kWh kg-1 H2 and 70 % on the basis of higher heating value (HHV). Furthermore, this system will be able to operate in overload mode referring to a production rate as high as 6.8 mh-1 H2 (1.5 times overload). Rapid response of 1 second for a hot start and 10 seconds for a cold start are the operating targets of the system.

At the stack level, the project will implement a patented design approach based on hydraulic cell compression. This design allows for large planar cell components, which is required for future mass production, and effective cooling at very high production rates and temperature levels. Regarding sufficient stack conditioning, a cooling system will be developed for voltages of maximum 2.0 V per cell at rated power and of 2.3 V per cell in overload modus. Additionally, the target of PRETZEL is the development of a high pressure PEMEL stack, which opens a perspective for specific stack costs of below 500 € kW-1. As for the production at 100 bar, an additional compressor is omitted, for the targeted system specific systems costs are possible in the range of 750 € kW-1.