Final Technical Report: Manufacturing and Additive Design of Electric Machines by 3D Printing (MADE3D)

As the U.S clean energy transition hinges on the growth of offshore wind, this is expected to be a major driver for innovations in manufacturing, material and design advancements to enable robust and cost-competitive wind turbines. The race to build larger and taller turbines rated 10 megawatts (MW) and beyond, has intensified pressure on OEMs in terms of logistics of handling and transporting large wind components, securing critical raw material as well as scaling up necessary domestic production infrastructure to meet the demand. There is increased interest in building lightweight, more efficient, and high-power dense drivetrains that will ease the burden on installation, minimize the raw material demand, increasing domestic sourceability. Despite good efficiency and reliability, existing drivetrain technologies such as direct-drive permanent magnet generators are heavy (> 300 tons), expensive, and often rely on large quantities of rare-earth permanent magnets (PMs), steel and copper. Existing design and manufacturing techniques for lightweighting are time intensive, result in complex topologies that are difficult to manufacture and result in material wastage. Substantial design and manufacturing innovations are needed to improve their scalability. MADE3D is a project led by the National Renewable Energy Laboratory in partnership with Oak Ridge National Laboratory (ORNL) and NASA Glenn Research Center aimed at advancing next generation of lightweight wind turbine generators with the potential to reduce demand for critical materials by more than 25% and enable such designs by multimaterial additive manufacturing (AM). As part of the project, new capabilities were developed to design and manufacture every component of the generator, including magnetic core packs and permanent magnets with reduced rare earth content. Electrical conductors with insulation, structural/mechanical components were designed and built in collaboration with a small wind turbine original equipment manufacturer (OEM), Bergey Windpower Company. NREL led the development of new electric machine design toolsets (topology optimization and shape optimization techniques) for the multimaterial design of magnets, electrical steel core, and conductors used in radial flux permanent magnet synchronous generators. The design methods and toolsets were used in design space exploration for lightweighting a 15-MW direct-drive generator and a 15-kW commercial wind turbine generator. ORNL investigated the feasibility of Fe3.0Si and Fe6.0Si steel as candidate materials for electrical steel laminate and rotor by selective laser melting. New insert molding technique was developed by extrusion-based printing processes for multimaterial printing of polymer bonded composite magnets made from SmFeN and Dy-free NdFeB magnets with electrical steel. NASA Glenn researchers advanced a direct-ink write approach for multimaterial printing of both the electrical conductors and insulation to achieve more than 70% fill factor that is beneficial for achieving high power densities. The design tools and manufacturing processes developed through the MADE3D project are anticipated to provide new opportunities to reduce the demand for critical materials used in next-generation offshore wind turbine generators, alleviate pressures on the supply chain, and create domestic manufacturing infrastructure that will eliminate multiple manufacturing processes, reduce production time and wastage by exploring novel optimized generator designs enabled via 3D printing.