(Invited) Looking Beyond the Stack: A Systems Engineering Approach to Optimize Stack and System Design of Electrolysers
Authors: de Groot Arend , Fabrizio Sara , Marcandali Giulia , Gali Harshraj , Snajdr Jan , de Goeij Bryan T.G. , Ntagkras Dimitris , Dussi Simone 
Published: August 2024

In the coming decade green hydrogen production is expected to grow at an unparalleled rate. Much of the international focus is currently on the Gigawatt scale plants, with regular announcement of new projects. From a European perspective, the rapid scale-up is necessary to reduce the reliance on fossil fuels and achieve CO₂ reduction targets. Importing green hydrogen or derivatives such as ammonia from regions where renewable electricity cost are low, is key driver for investments for the energy intensive industry, especially in the North Western part of Europe. This will require hydrogen production on a very large-scale. In contrast to the differentiation on application level, a one-size fits all approach for stack manufacturing appears to be attractive, with a high degree of standardisation and volume of production.
However, as the case for the Netherlands illustrates, there are more drivers for green hydrogen production, such as addressing (regional) grid congestion, improving the business case for offshore wind farm developments, and providing green energy to small and medium enterprises. For all these use cases the requirements for the electrolyser system differ. Aspects such as the variability of the energy supply, capacity factors, logistics for operation and maintenance, available footprint, are application specific. Therefore, electrolyser system designs may need to be optimized for different markets and applications.
At TNO we focus on the development, integration and validation of novel materials and innovative cell components for the different generations of electrolyser technology, both for low temperature (liquid alkaline, PEM, AEM) and high temperature electrolysers. To understand and assess the requirements for future generations of electrolyser technology, a systems engineering approach is developed together with the industrial partners. This allows to translate the requirements from the application, to the system and stack design, down to the requirements on a cell and component level.
Results will be presented from several studies carried out by TNO and industrial partners in the field of low temperature electrolyser systems to understand:

How to optimize a stack design for a specific application. Should an electrolyser be designed to maximize flexible operation and achieve a broad operating range? Or will a high efficiency be the most important target? And how application specific is such an optimisation.

How to bring down the cost of the total system. What impact do the design choices for the electrolyser stack have on the complexity of the system around the electrolyser, the balance-of-plant? What can we learn from this for the future stack requirements?

How different operating strategies impact a certain design. Which stack requirements change in large multi-stack systems powered by renewable electricity supply? Can different strategies improve overall system performance and bring down the overall cost of hydrogen production?

How can the desired safety level be achieved against the lowest cost by optimizing component and stack design?

As both the electrolyser technology and the value chains become more mature, a systems engineering approach will be indispensable, bringing together the requirements of the different levels: from application, electrolyser system and stack design, down to the performance of individual components.