Identifying path ahead for tackling future challenges in direct-drive permanent magnet wind turbine generator's electro-mechanical design and manufacturing

Increasing the number of offshore wind farms and installing larger wind turbines, are just two ways to meet the Net Zero targets set in both the UK and EU. The offshore environment is harsh and there are additional challenges such as accessibility, so it is important to have reliable equipment installed within these wind turbines. Geared drivetrains have been observed to lack the sufficient level of reliability required in an offshore environment, so the direct-drive generator designs without any gearbox, aim to increase the reliability. Due to the increased level of torque the direct-drive generators tend to be larger and heavier, they require more permanent magnets and accordingly more rare earth material, as well as more demanding mechanical structures for the generator and drives and these all cause issues with design, supply chain, manufacturing and installation for original equipment manufacturers (OEMs). This paper has reviewed the state-of-the-art design, manufacturing and assembly of direct-drive permanent magnet generators. The key OEMs that supply the current state-of-the-art direct-drive turbines have been identified and some interviews with experts from industry have been conducted. These efforts aimed to understand the challenges with direct-drive turbines, that is a significant contribution to the growth of offshore wind, to address Net Zero’s growing demand. These challenges are found to be primarily imposed on the manufacturing side, to the scaling up in numbers and size to catch up with the market demands. Finally, this work proposes recommendations to overcome these challenges, with regards to the design and manufacturing respectively, which includes, reducing the amount of permanent magnet material, optimizing the design to reduce the structural mass, automating as many of the manufacturing/assembly processes as possible and practicable, and using alternative processing such as additive manufacturing.