Rolls-Royce is entering the H₂ production market and acquiring a 54% majority stake in electrolysis stack specialist Hoeller Electrolyzer, whose innovative technology will form the basis of a new range of mtu electrolyzer products from its Power Systems division. Hoeller Electrolyzer, based in Wismar, Germany, is an early-stage technology company that is developing highly efficient polymer electrolyte membrane (PEM) stacks, under the brand name Prometheus, for the cost-effective production of H₂.

H₂ is an increasingly attractive power source to fuel the green energy transition and demand for green H₂ – whose production creates no CO₂ – is expected to rise significantly. It is needed for fuel cells and H₂ engines, to produce synthetic drop-in fuels and for industrial processes that use H₂ that is not created in a carbon neutral process. Consequently, high-performance electrolyzers are a key component of any H₂ system.

Dr. Otto Preiss, COO and Chief Technology Officer, Rolls-Royce Power Systems said, “By developing our own mtu electrolyzers and by taking a majority stake in Hoeller Electrolyzers, we are methodically growing our H₂ portfolio and securing access to this fascinating technology, which is not a pipe dream but has great market potential. This will enable us to supply complete H₂ solutions and make a significant contribution to protecting the climate. Our complete H₂ solutions will enable customers to store renewably produced energy in the form of H₂ for use as and when required, or for further processing or onward sale.”

In H₂ electrolysis, water is subjected to DC electrical current, producing H₂ at the negative pole and oxygen at the positive pole. In this way, it is possible to produce carbon-neutral H₂ by using electricity from renewable sources such as solar or wind. The electrochemical reaction takes place in a cell between plate-shaped electrodes separated by membranes. Hundreds of cells located one above the other and pressed together form a stack, the heart of an electrolyzer.

Hoeller Electrolyzer has positioned itself, with Prometheus, as one of the few highly specialized expert players in the field of high-efficiency PEM electrolysis stacks. Its founder, Stefan Höller, has more than a quarter of a century’s experience of developing electrolysis technology and has already registered 14 patents connected with Prometheus. Particularly high efficiency is promised by special surface technologies for the bipolar plates which significantly reduce the use of expensive precious metals platinum and iridium as catalysts, as well as increased output pressure.

Stefan Höller, Managing Director, Hoeller Electrolyzer said, “Our stack is going to produce H2 at a price not previously thought possible.”

Rolls-Royce and Hoeller Electrolyzer are united by a shared belief in the opportunity of zero-carbon energy – both for power supply and the propulsion of heavy vehicles. With decades of experience and systems expertise, Rolls-Royce is going to develop a complete electrolyzer system and has a global sales and service network, which opens the potential for significant worldwide sales.

Matthias Kramer, CFO and Joint Managing Director, Hoeller Electrolyzer said, “In Rolls-Royce, not only have we found an important customer for our stacks, we've also secured an ideal partner and supporter who shares our vision of putting stacks into full production.”

Development work on the first mtu electrolyzer using a stack from Hoeller Electrolyzer is already underway. In 2023, it will go into operation at the Validation Center in Friedrichshafen to demonstrate how an electrolyzer fits into the overall architecture of a microgrid. An initial customer project is already planned for 2024.

Armin Fürderer, who heads up the Net Zero Solutions business unit of Power Systems said, “We're going to launch electrolyzers with several megawatts of power right from the start. A total output of over 100 megawatts is conceivable by combining several electrolyzers.”

The equity in Hoeller Electrolyzer now held by Rolls-Royce comes from departing minority shareholders and from an increase in share capital. Financial details of the transaction are not being disclosed. Stefan Höller and Matthias Kramer will continue to lead Hoeller Electrolyzer as a standalone company, with the goal of building a leading international stack manufacturer.