Water electrolysers for electricity grid services – dynamics, advantages and disadvantages of different types of electrolysers

Kurzfassung

Water electrolysers are expected to play an important role in the future strategy of EU for decarbonization. With an increasingly renewable-energy fed grid they can produce hydrogen for application in transport and industry replacing in these sectors CO2-emitting technologies. They can also help stabilizing the grid and provide energy storage via hydrogen production and electricity production from hydrogen. Today there are primarily two techniques of electrolysers on the market. The mature and robust technology of alkaline electrolysis used up to megawatt size for decades is believed to be not flexible in operation. Just approaching systems commerciality in the megawatt size is the technique of PEM (polymer electrolyte membrane) water electrolysis. This technique is characterized by its capability of dynamic operation. Still with the demonstration in 100 kilowatt size is the technique of high temperature solid oxide electrolysis. It may reach very high electrical efficiency and has been demonstrated for reversible operation, i.e. the option of either consuming electricity and producing hydrogen (electrolysis) or consuming hydrogen and producing electricity (fuel cell). Grid services as supplied to TSO (transmission system operators) and DSO (distribution system operators) were investigated in the project QualyGridS and transferred into testing protocols for electrolysers performing grid services. In this application the electrolyser offers its operational flexibility as a power consuming load to achieve improved revenues. The properties of the different electrolyser technologies are reviewed in this contribution. Modern alkaline electrolysers show their suitability even for fast grid services. They as well as PEM electrolysers need an update in their control system to adapt them to grid services requirements. Based on the lessons learned from QualyGridS this contribution will discuss also the suitability of high temperature SOEC technology for grid service based on present knowledge and technology. This project has received funding from the Fuel Cells and Hydrogen 2 Joint Undertaking under grant agreement No 735485. This Joint Undertaking receives support from the European Union’s Horizon 2020 research and innovation programme and Hydrogen Europe and N.ERGHY. The work is also supported by the Swiss State Secretariat for Education, Research and Innovation (SERI) under contract No. 17.0009.