VOMPELS: High-pressure electrolysis of water

The “Power-to-Gas” process is a key component of the energy transition in order to provide long-term storage for the fluctuating supply of energy generated from renewable sources. During electrolysis, electric current is used to split water into hydrogen and oxygen, the hydrogen produced can be fed into the existing natural gas network and stored. To do this, the hydrogen has to be pressurised. This usually takes place after electrolysis using a process of mechanical compression. A consortium consisting of the Westphalian University of Applied Sciences and the companies iGas Energy GmbH, ProPuls GmbH and Obitronik GmbH has now developed a system whereby electrolysis is carried out directly under pressure, making the downstream mechanical compression of hydrogen unnecessary. This saves money, time and resources.

The fully modular PEM high-pressure electrolyser developed in the collaborative “Vompels” project has a special design and is based on various patents. Several electrolysis cells are combined to form a stack and rinsed with a pressurised hydraulic medium while in operation. The pressure on the active cells can thus be kept constant throughout. Under these conditions, the hydrogen gas which is produced during electrolysis can be extracted directly and therefore efficiently under high pressure. Thanks to the variably adjustable hydraulic pressure, it is also possible to achieve nearly any pressure level required for the hydrogen produced.

Engine for progress:

  • Development of a specialised high-pressure electrolysis stack
  • Elimination of the downstream mechanical compression process
  • Savings in terms of resources, time and money
  • Optimised for simultaneous utilisation of waste heat

1 of 1

Photo: Westfälische Hochschule

Schematic structure of the modular PEM electrolyser stack (PEM: proton exchange membrane) in pocket-type construction.

Avoiding mechanical compression saves resources

Using this process, the hydrogen produced can be fed directly into the natural gas pipeline network. The downstream mechanical compression process is no longer required – and the need for a high maintenance and expensive mechanical component of the power-to-gas plant is also removed. This not only saves money and time, but also resources. The initial studies of the electrolysis system have been carried out as part of a project run by the Central Innovation Programme for SMEs (ZIM). With the measuring system developed in-house it was possible to prove the functional capability of the newly developed electrolyser up to a pressure of five bars. What is more, ongoing research is focusing on producing hydrogen at pressures of up to 100 bars. In the near future it will also be possible to expand the electrode surfaces to more than 1,000 cm2 in order to produce larger quantities. “The overall cell design is aimed at industrial applications in particular,” says Dr Ulrich Rost of ProPuls GmbH.

Climate-friendly heating

The possibility of utilising waste heat offers a further benefit: the waste heat produced during electrolysis can be recovered through the hydraulic medium and made available for use via external heat exchangers. The stack concept is thus making a contribution to climate-friendly heating in the area of future applications with combined heat and power (CHP). What is more, the system is designed for high outputs and high voltages, so the waste heat utilisation can also be further optimised.

Photo: Andreas Hoch

"If one considers the challenges in terms of storage technology which result from the energy transition, it is clear that these cannot be overcome without using hydrogen as a storage medium. In future, therefore, the simple, economical and robust provision of high-pressure hydrogen will be especially important. With the development of a PEM high-pressure electrolyser, the consortium consisting of various companies in collaboration with the Westphalia Energy Institute is offering a particularly elegant solution to this problem.”

Prof Dr Michael Brodmann, Vice President for Research and Development at the Westphalian University of Applied Sciences, Director of the Westphalia Energy Institute

Partners and sponsors

  • Westfälische Hochschule
  • iGas energy
  • ProPuls GmbH
  • Obitronik GmbH
  • EU-Förderung
  • Bundesministerium für Wirtschaft und Energie (BMWi)
  • Landesregierung NRW

Further reading & downloads