UK-based global major power and propulsion systems group Rolls-Royce has announced that its Germany-based Power Systems division had acquired a 54% stake in German start-up company Hoeller Electrolyzer (Hoeller). The start-up, founded in 2016, has developed an innovative hydrogen electrolysis technology that will form the basis of a new range of electrolyser products that Rolls-Royce Power Systems will market under its ‘mtu’ brand, using Hoeller’s product name Prometheus. Hoeller will continue to function as a standalone company, retaining its current leadership.

In its press release, Rolls-Royce explained that the production of hydrogen by electrolysis involved subjecting water to direct current electricity; as a result, hydrogen would be released and concentrate at the negative electrode while the oxygen released would concentrate at the positive electrode. The electrodes, in plate form, were separated by membranes. A complete unit, enclosing the electrodes, membrane, water, forms a cell – a polymer electrolyte membrane (PEM) cell, to be precise. Hundreds of these cells, placed one above the other and “pressed together” form a PEM stack. The electricity required to power the electrolysis process can of course come from green power sources.

Hoeller’s PEM stacks are highly efficient. The company has developed special surface technologies for the electrodes that “significantly reduce” the use of expensive platinum and iridium as catalysts. “Our stack is going to produce hydrogen at a price not previously thought possible,” affirmed Hoeller MD Stefan Höller.

The first mtu electrolyser to use a Hoeller PEM stack is already under development. It is scheduled to start operating next year, at Rolls-Royce’s Validation Centre in Germany, where it will demonstrate how such technology can be incorporated into the architecture of a microgrid. The first project for a customer is planned for 2024.

“We’re going to launch electrolysers with several megawatts of power right from the start,” highlighted Rolls-Royce Power Systems Net Zero Solutions business unit head Armin Fürderer. “A total output of over 100 megawatts is conceivable by combining several electrolysers.”

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