The project will build a test facility to test electrolysis systems. It will then carry out tests with electrolysis for the production of hydrogen and oxygen and for the recovery and utilisation of residual heat. The facility will be used for academic and scientific research by replicating the large-scale facilities planned for the steel industry in Norrbotten. The tests are aimed at creating reliable and vendor-independent data that can form the basis for planning the operation and maintenance of large plants. The results will be made public and will be of use to anyone with an interest in large-scale electrolysis. The focus is on the transient behaviour of the electrolyser and the special difficulties that can arise during operation in cold climates. The long-term tests will be documented to create a basis for operating strategies that can balance the electricity grid.