Electrolyzers for green hydrogen

Hydrogen plays a central role in the energy transition. The so-called national hydrogen strategy provides for 700 million euros in government subsidies to drive implementation forward. This comprises the three lead projects: _H2Giga, _H2Mareand TransHyDE.

We urgently need large electrolyzers that can be used flexibly to produce hydrogen," warns Prof. Bernd Kuhlenkötter, Head of the Chair of Production Systems (LPS) at Ruhr-Universität Bochum, who is playing a key role in _H2Giga. "Without this technology, the production of green hydrogen and thus the energy transition is not feasible."

In fact, the demand for hydrogen is huge. The government now expects several hundred million tons per year. The aim of the national initiative is to build up electrolysis capacities of no less than five gigawatts for Germany by 2030. This capacity corresponds to around 876,000 tons of green hydrogen per year. Although the current capacity is already just under 8 million tons of hydrogen, this has so far been produced almost exclusively from natural gas, which is harmful to the climate. The scientists now want to change this. "We want to make electrolysers ready for the assembly line and also develop assembly line production for electrolyser production on an industrial scale," summarizes Kuhlenkötter, who heads the FertiRob sub-project. To this end, the LPS is working together with the Institute of Production Engineering (wbk) at the Karlsruhe Institute of Technology (KIT) and 14 other partners from industry, including companies such as Bosch and ABB.

Focus on mass production

More specifically, the researchers are looking to automate the production of stacks and electrolysers, drastically increase their capacity and meet quality requirements in the process. The production of stacks, the core component of electrolysers in which the actual splitting takes place, is currently a purely manual process and therefore very cost-intensive, and production capacities are limited. "We therefore also need automation solutions for the production and assembly of smaller electrolysers, which are later assembled into larger electrolyser systems," reports Kuhlenkötter. "This step is necessary if we don't want value creation to migrate to the East, where labor is cheaply available, as has already happened with solar energy. The danger is real, because China, for example, is currently investing huge sums in hydrogen technologies."

The WGP researchers from Bochum and Karlsruhe are approaching the matter with an open-minded approach to technology, meaning they want to look at PEM technology (proton conducting membrane electrolysis) as well as alkaline (AEL) and high-temperature electrolysis (HTEL). "Each of the three types is particularly suitable for special applications," says Kuhlenkötter. "HTEL - as the name suggests - is used wherever high temperatures prevail, such as in the steel industry. The advantage of PEM electrolysers, on the other hand, lies in their dynamics; they can be switched on and off repeatedly and are primarily used where volatile energy supply is required." For example, in an electricity grid that is fed by an ever-increasing proportion of renewable energy sources such as wind power and solar energy. Instead of switching off wind turbines on windy days so as not to overload the power grid, the surplus energy can be sent to hydrogen production. "In this way, power peaks in the German power grid, especially at the locations of wind and solar power plants, can be usefully smoothed out. Unfortunately, PEM electrolysers are very expensive."

And the quality?

However, the researchers are not just focusing on assembly, automation and easier handling. Quality assurance also plays a central role in everything. "In order to make electrolyser production more economical, it is essential to develop strategies for quality assurance so that the result of the production process is already possible through the assessment of intermediate products," explains Prof. Gisela Lanza from the wbk at the Karlsruhe Institute of Technology (KIT). "Our aim is therefore to identify critical process and product parameters in order to ensure the quality of the electrolysers without losing time and money with immature production processes."

As part of FertiRob, digital twins of the stacks and systems as well as virtual commissioning (VIBN) are to be established in the coming years. The digital images will then be used to optimize processes before they are actually implemented, thus preventing defective products in advance.

In addition to FertiRob, the LPS is also working on the HyPLANT100 project. The aim here is to research how smaller electrolysers, for example on the scale of a computer, can be assembled modularly and efficiently into larger electrolysis systems. They are to be flexibly tailored to the respective industry. An electrolyser for a refinery has to meet different requirements than a plant for the fertilizer industry, which wants to produce ammonia with hydrogen instead of natural gas.

In addition to planning and production, WGP researchers are also involved in recycling and the sustainable use of resources as part of ReNaRe. This sub-project focuses on the recycling of electrolysers and materials. "We are researching automated mechanical processes for dismantling electrolysers. In this way, resources can be used optimally in the future and materials can be reused," explains Prof. Jürgen Fleischer, also from the wbk in Karlsruhe. Depending on the technology, very different materials can be recycled, including special steels, nickel, metals such as iridium and platinum or even rare earths such as yttrium. "This is also an important cost factor. After all, one gram of iridium, for example, costs around 150 euros today and the annual extraction volumes are very low."

More than 20 partners from industry and research are involved in the FertiRob and HyPLANT100 projects, with the German government providing 24 million euros in funding. The Chair of Production Systems (LPS) is receiving a good 4.8 million euros in funding for these two projects. For ReNaRe, it approved around 9 million euros for 13 partners, including around 700,000 euros for KIT alone.