  In this paper, the authors investigate a number of design and market
considerations for an axial flux superconducting electric machine design that
uses high temperature superconductors. This work was carried out as part of the
University of Cambridge's Centre for Entrepreneurial Learning ETECH Project
programme, designed to accelerate entrepreneurship and diffusion of innovations
based on early stage and potentially disruptive technologies from the
University. The axial flux machine design is assumed to utilise high
temperature superconductors in both wire (stator winding) and bulk (rotor
field) forms, to operate over a temperature range of 65-77 K, and to have a
power output in the range from 10s of kW up to 1 MW (typical for axial flux
machines), with approximately 2-3 T as the peak trapped field in the bulk
superconductors. The authors firstly investigate the applicability of this type
of machine as a generator in small- and medium-sized wind turbines, including
the current and forecasted market and pricing for conventional turbines. A
study is also carried out on the machine's applicability as an in-wheel hub
motor for electric vehicles. Some recommendations for future applications are
made based on the outcome of these two studies. Next, the cost of YBCO-based
superconducting (2G HTS) wire is analysed with respect to competing wire
technologies and compared with current conventional material costs. Current
wire costs for both 1G and 2G HTS are still too great to be economically
feasible for such superconducting devices, but round wire, so-called 3G HTS,
conductors may be a promising new option with a view to the future. Finally,
different cooling options are assessed for the machine design and the analysis
suggests that waiting for the maturation of pulse-tube cooling technology may
be the best option for this particular application.
