Large Offshore Wind Power Generators Suitable for Green Hydrogen Production

This invited talk was presented at the 2024 Applied Superconductivity Conference in Salt Lake City, Utah, U.S.A. on 6 September 2024.

Generation of hydrogen with renewable energy generation from wind power is currently of great interest. Off-shore wind farms are well-suited for electrolysis because they have access to a large and consistent source of renewable energy. The strong and consistent wind at sea provides a reliable source of electricity for the electrolysis process. Offshore H₂ production is estimated to be the most economical option. Large wind turbine generator units exceeding 20 MW are of interest as the generator’s physical size and efficiency are the two most important attributes. Superconductors help reduce the size and increase the efficiency. Initially, field excitation coils could be constructed using superconductors with a stator employing conventional conductors. Both rotor and stator coils could be constructed to enable quick replacement of defective coils to minimize the down time. The low generator frequency could also permit use of superconductors for the stator coils. This is likely to have significant beneficial impacts on the size and efficiency of the generator.

It might be possible to design large units dedicated to production of H₂ alone – avoiding transfer of electric power to the shore. This decouples the generator from the electric grid and allows optimizing the generator design for hydrolysis only. The DC required for hydrolysis is obtained simply by rectifying generator produced AC. The electronics system needed for simple AC to DC conversion would be much simpler and cheaper than AC synched to the electric grid.

A 25 MW generator operating at about 6 RPM will be large, prohibiting road transportation from the factory to the site. This paper describes a concept design for a 25 MW generator with the stator and rotor assembled from self-contained quadrant modules that are factory built and tested prior to road transporting to the site. Each quad unit has its own superconducting coils, cryostat, cooling, and current sources. The modules are assembled to form the generator unit at the site, and can also be serviced or replaced individually, which adds significant flexibility and robustness to the operating model.