Development of superconducting wind turbine generators

Abstract

In this paper the commercial activities in the field of superconducting machines, particularly superconducting wind turbine generators, are reviewed and presented. Superconducting generators have the potential to provide a compact and light weight drive train at high torques and slow rotational speeds, because high magnetic fields can be produced by coils with very little loss.Three different superconducting wind turbine generator topologies have been proposed by three different companies. One is based on low temperature superconductors (LTS); one is based on high temperature superconductors (HTS); and one is a fully superconducting generator based on MgB 2 . It is concluded that there is large commercial interest in superconducting machines, with an increasing patenting activity.Such generators are however not without their challenges. The superconductors have to be cooled down to somewhere between 4K and 50K, depending on what type of superconductor is employed, which poses a significant challenge both from a construction and operation point of view. The high temperature superconductors can facilitate a higher operation temperature and simplified cooling, but the current price and production volumes prohibit a large scale impact on the wind sector. The low temperature superconductors are readily available, but will need more sophisticated cooling.Eventually the CoE from superconducting wind turbines, with particular emphasis on reliability, will determine if they become feasible or not and for such investigations large-scale demonstrations will be needed.

AC Losses and Their Thermal Effect in High-Temperature Superconducting Machines

“…3. 1 As will be seen later, the temperature increase due to the AC losses for the case studied in this paper is very limited, its influence on the critical current density is negligible, so the temperature dependence of J c is not considered.…”

“…H IGH temperature superconducting (HTS) machines possess characteristics such as high power density and high efficiency, and they are preferable in applications such as ship propulsion and wind generators [1], [2]. Particularly, since direct drive wind generators with large power ratings will reduce the cost of wind farms, designs of HTS wind generators in 10 MW rating and above have been of great interest in recent years [3]- [5].…”

Wind Turbine Generator Efficiency Based on Powertrain Combination and Annual Power Generation Prediction

“…However, the requirement for 600-800 kg rare earth per MW may significantly affect development costs. Furthermore, generators with high torque density may contribute to light weight, but the fundamental problems with maintenance cannot be addressed [6]. The maintenance costs of wind turbine generators are significantly affected by the structure complexity and marine conditions.…”

Contemporary wind generators

“…• Synchronous reluctance generator (SynRG) (Tokunaga et al;2011) • Switched reluctance generator (SRG) (Choi et al, 2014); • Brushless DFIG (BDFIG) (Long et al, 2013); • Split-PM induction generator (S-PMIG) (Potgieter, 2011); • Slip synchronous-PM generator (SS-PMG) (Potgieter, 2014); • Switched-flux generator (SFG) (Sulaiman et al, 2013;Kayano et al, 2010;Ojeda et al, 2012) • Ferrite-assisted reluctance synchronous generator (FA-RSG) (Baek et al, 2009); • Magnetic gears and pseudo-direct drive (Wenlong, 2011); • Superconducting machines (Jensen et al, 2013); • PM Field-intensified synchronous reluctance generator (FI-RSG) (theoretical).…”