Prototype modular cryostat utilized for 10 MW offshore superconducting wind turbine.

Karlsruhe Institute of Technology (KIT) has designed the cryogenic cooling system for a 10 MW superconducting generator (SCG) for offshore wind turbines. The cooling system adopts the cryogen-free and modular concept. A modular cryostat, that enables each of 48 coils in the SCG to work at cryogenic temperatures of 20 K, provides an advantage of easy transportation, installation, and maintenance in the offshore environment. Furthermore, with the modular design the 10 MW SCG concept can be validated through a scale-down model. This paper describes the development of a prototype modular cryostat and the preliminary cool down by a two stage Gifford-McMahon cryocooler through conduction cooling. The dummy coil made of copper enveloped in the cryostat could reach a temperature of 9 K after 56.5 hours. The encouraging experimental results agree well with the numerical simulation. Numerical model and test results are presented.