Design of a 20-MW Fully Superconducting Wind Turbine Generator to Minimize the Levelized Cost of Energy

Superconducting machines are promising candidates for direct-drive multimegawatt offshore wind turbines. Here, we designed a 20-MW fully superconducting synchronous wind turbine generator using magnesium diboride (MgB2) superconductors for both rotor and stator windings. MgB2 tapes operating at 10 K are used for the rotor windings in order to improve the packing factor. A Rutherford cable made of 91-filament MgB2 wires operating at 20 K is used for the stator windings in order to limit the ac losses. Two separate cryostats are considered for the stator and the rotor to increase the system reliability. Besides, to reduce the machine's weight and to simplify the cryogenic system, a toothless magnetic circuit is adopted. The goal of the two-dimensional finite element method based optimization was to minimize the levelized cost of energy (LCOE). Numerical results show that the adopted topology is lightweight enabling to reduce the cost of the nacelle, tower, and foundation, and therefore, the LCOE in comparison to a conventional generator. But the ac losses are significant, requiring at this stage of the study an impractical number of cryocoolers.