Producing green hydrogen on a gigawatt scale

By Hans van’t Noordende, ISPT

The production of green hydrogen is technically not a brain teaser. Electrolysis technology to make hydrogen from demineralised water has been around for about a century. The challenge is mainly to make a jump in scale to make green hydrogen competitive in price. There are several preconditions for the necessary increase in scale (see box). EU and national governments must ensure that green hydrogen production is profitable with new regulations.
In addition, we need a growing capacity for offshore wind to keep future hydrogen factories running for sufficient hours per year.
Another condition for large-scale implementation of green hydrogen is clarity about the capital expenditure for a gigawatt hydrogen plant. What are the costs for a factory? Can smart applications of advanced technologies, materials and optimisations reduce costs to such an extent that green hydrogen becomes an attractive alternative for industry?

Hydrohub Gigawatt Scale Electrolyser project

The Hydrohub Gigawatt Scale Electrolyser project has answered the question of how we can produce green hydrogen in the Netherlands cost-efficiently and on a large scale. Furthermore, we looked at how to improve the performance and which electrolysis technologies have the best potential in terms of costs, flexibility and heat recovery. Advice on geographics and how the basic design for a hydrogen plant with a capacity of 1 gigawatt would look were also provided.
“We looked at where the factories could be located in the five Dutch industrial clusters and identified 22 potential locations,” says Hans van’t Noordende, technical project leader at ISPT.
“In consultation with industrial companies, network operators and governments, we mapped out how such a factory fits their needs and projects, where we can extract water and electricity, how to distribute hydrogen in the smartest way and how to use the residual heat.”

Advanced design for AWE and PEM factory

Engineers and scientists worked on an advanced design for an energy- and cost-efficient factory. They worked out the design for both an alkaline technology (AWE) plant and a plant with electrolysers using PEM: proton-selective polymer membranes.The team looked for innovations, improvements and optimisations at each process step in the design. Various innovations in the electrolysis stacks and scaling-up potential to larger units were investigated.
For example, both types of electrolysers use advanced electrode materials and thinner, state-of-the-art materials. In addition, higher operating temperatures are considered, assuming that the degradation of electrodes is controlled. As a result, a better performance expressed as H2 productivity per kW could be achieved with fewer stacks.
The number of cells per stack has also been increased. The AWE stacks have 335 cells with a total capacity of 20 megawatts. The PEM stacks use half that power with 310 cells.
“The anodes contain lower amounts of iridium, which means that we are less dependent on this scarce raw material for constructing hydrogen factories,” says Van ’t Noordende. The electrolysers form modular units of 160 megawatts (AWE) and 40 megawatts (PEM). “This modular structure makes it possible to scale up factories cost-effectively.”

Material selection

For alkaline water electrolysis technology with (30%KOH) caustic services at higher temperatures (90-100°C), stress corrosion cracking is the dominant corrosion mechanism. For PEM technology, dealloying is the main corrosion type.
In the case of Alkaline separators, CS Ni clad (3mm) is the most cost-effective material at these temperatures.
For piping with KOH/H2 service SS310S, Duplex 2906 materials are preferred, whereas for KOH/O2 service Ni-200, high Ni alloys (20, 600, 800) are needed.
In the case of PEM, ultra-pure water is used. Therefore, the material considered is SS316 for piping and for rotating and static equipment.
The main concern is the leaching of Fe(II) and other elements leading to the deactivation of catalyst materials with an adverse impact on PEM stack performance and lifetime. Extensive water treatment may be needed to remove these highly diluted elements.

Skip hydrogen compression

Another improvement in the design was to increase the pressure in the AWE electrolysers to 5 bar, Van’t Noordende reveals. “That way, we skip the first expensive step of hydrogen compression. The hydrogen must then be further compressed to 30 bar for the end users. For PEM, that pressure of 30 bar is already there, so extra compression is not necessary, making a PEM installation slightly more efficient. But both types of stacks have nearly 80% system efficiency.”
The AWE stacks operate at a temperature of 100°C, in the PEM it is at 70°C. The design also takes into account heat recovery from the cooling water. Regional heat networks could make use of this.
The engineers are also taking advantage of opportunities to optimise the electrical installations of the hydrogen plant. A cost-effective layout has been designed with 380 kV/66 kV transformers in combination with low voltage transformers and active control semiconductor rectifiers called Insulated-Gate Bipolar Transistors (IGBTs). That
is in accordance with the network requirements. The transformer and rectifiers form independent e-houses, which makes the design particularly compact.

Continue with R&D, pilots and demonstrations

On an area of approximately 10 hectares, the hydrogen factory houses everything needed for electrical installations, electrolysis, purification and compression to supply hydrogen in line with the fluctuating supply of sustainably generated wind energy and in accordance with the demand of the end users. Nevertheless, R&D, pilots and demonstration projects are still needed to implement technological innovations that allow further cost reductions.
A major advantage of the Hydrohub Gigawatt Scale Electrolyser project is that there is a concept or design on paper. In fact, the project team has even made a virtual reality model and animation film that allows you to walk through the factory; visit https://bit. ly/3IQrGV0

ISPT innovation platform

As a platform, ISPT brings parties together to work on making the industry more sustainable. “Together with our partners in the industry, we put issues on the agenda and define projects. In 2017 we started this Hydrohub Gigawatt Scale Electrolyser project, and worked with the most suitable implementing parties to form a strong consortium and get results. This project is part of ISPTs hydrogen program, the Hydrohub Innovation Program.