Edinburgh Napier University

  With an ever-growing market share for offshore wind, direct-drive generators are touted as a low maintenance alternative to conventional drivetrains. However, to contend with higher torque requirements essential for low-speed operation, direct-drive machines are vastly heavier than conventional geared systems. As material use and sustainable engineering remains a key theme in the current climate, establishing methods for best practice in design stages is critical. This report therefore details a proposed methodology for the efficient, sustainable design of large-scale, direct-drive wind turbine electrical generator structures, considering mechanical, and thermal performances, whilst meeting sustainability metrics. This investigation finds that Coefficient of Thermal Expansion has a considerable influence on the maximum Equivalent Von-Mises' stress, for an optimised rotor structure under the expected loading scenario. Material choice was also found to have a significant impact on the rotor's carbon footprint and the energy use during manufacture and transport.