GreenSpur Renewables has built what is said to be the world’s largest ferrite-based direct drive permanent magnet generator (DD-PMG) for offshore wind turbines that is capable of multi-megawatt electricity generation.
The DD-PMG, capable of producing 250kW, uses a new construction method that solves many problems today’s offshore wind turbines experience without the need for large quantities of rare earth magnets, GreenSpur said.
The generator was assembled in the North East of England and is now at Offshore Renewable Energy (ORE) Catapult in Blyth where system testing will be carried out over the next few months.
“The current generation of direct drive generators used in today’s offshore wind farms rely on rare-earth magnets. Not only is the supply of these dominated by China – and may possibly be restricted as part of the ongoing US-China trade war – there is also competition for magnet supply from other fast-growing industries, including defence, computing and electric vehicles,” said Andrew Hine, Commercial Director at GreenSpur.
“Not only does our generator use no rare earth magnets, our source material – ferrite – is actually a waste product of the steel making process – unlike rare earths, whose mining is environmentally damaging.”
Replacing scarce and expensive rare earth magnets which cost GBP 40 per kg with cheap and abundant ferrite magnets, costing GBP 1 per kg, is expected to deliver a generator CAPEX saving of circa 33%.
The design is also said to offer fast scaling through a modular design that allows generators to be constructed in stages, for example, a 12MW offshore turbine can be created by stacking three 4MW units in parallel.
GreenSpur tested a 75kW generator in Blyth in 2017, after which it signed an agreement with ORE Catapult and Warwick Manufacturing Group to build a single-stage 250kW direct drive generator, which is part of a four-stage 1MW design.