Wednesday, May 31, 2017

Rare earths and wind turbines: Yes, it’s a problem

Despite wind industry lobbyists and apologists asserting otherwise, rare earth metals, particularly neodymium, are indeed extensively used in wind turbine magnets.

‘Permanent magnet machines feature higher efficiencies than machines with excitation windings (absence of field winding losses), less weight and the advantage of having no slip-rings and brushes. Machines above kilowatt range (and most below) employ high-specific energy density PM material, preferably of neodymium-iron-boron (Nd-Fe-B).’ —Wind Energy Systems for Electric Power Generation, by Manfred Stiebler, Springer, 2008

‘The data suggest that, with the possible exception of rare-earth elements, there should not be a shortage of the principal materials required for electricity generation from wind energy. ... Sintered ceramic magnets and rare-earth magnets are the two types of permanent magnets used in wind turbines. Sintered ceramic magnets, comprising iron oxide (ferrite) and barium or strontium carbonate, have a lower cost but generate a lower energy product than do rare-earth permanent magnets comprising neodymium, iron, and boron (Nd-Fe-B). The energy-conversion efficiency of sintered Nd-Fe-B is roughly 10 times that of sintered ferrite ... As global requirements for rare-earth elements continue to grow, any sustained increase in demand for neodymium oxide from the wind resource sector would have to be met by increased supply through expansion of existing production or the development of new mines. ... An assessment of available data suggests that wind turbines that use rare earth permanent magnets comprising neodymium, iron, and boron require about 216 kg [476 lb] of neodymium per megawatt of capacity, or about 251 kg [553 lb] of neodymium oxide (Nd₂O₃) per megawatt of capacity.’ —Wind Energy in the United States and Materials Required for the Land-Based Wind Turbine Industry From 2010 Through 2030, by U.S. Geological Survey, U.S. Department of the Interior, Scientific Investigations Report 2011–5036

‘Five rare earth elements (REEs)—dysprosium, terbium, europium, neodymium and yttrium—were found to be critical in the short term (present–2015). These five REEs are used in magnets for wind turbines and electric vehicles or phosphors in energy-efficient lighting. ... Permanent magnets (PMs) containing neodymium and dysprosium are used in wind turbine generators and electric vehicle (EV) motors. These REEs have highly valued magnetic and thermal properties. Manufacturers of both technologies are currently making decisions on future system design, trading off the performance benefits of neodymium and dysprosium against vulnerability to potential supply shortages. For example, wind turbine manufacturers are deciding among gear-driven, hybrid and direct-drive systems, with varying levels of rare earth content. ... Neodymium-iron-boron rare earth PMs are used in wind turbines and traction (i.e., propulsion) motors for EVs. ... the use of rare earth PMs in these applications is growing due to the significant performance benefits PMs provide ... Larger turbines are more likely to use rare earth PMs, which can dramatically reduce the size and weight of the generator compared to non-PM designs such as induction or synchronous generators. ... Despite their advantages, slow-speed turbines require larger PMs for a given power rating, translating into greater rare earth content. Arnold Magnetics estimates that direct-drive turbines require 600 kg [1,323 lb] of PM material per megawatt, which translates to several hundred kilograms of rare earth content per megawatt.’ — Critical Materials Strategy, by U.S. Department of Energy, December 2011

‘In the broader literature ..., concerns have been raised about future shortage of supply of neodymium, a metal belonging to the group of rare-earth elements that is increasingly employed in permanent magnets in wind turbine generators.’ —Assessing the life cycle environmental impacts of wind power: a review of present knowledge and research needs, by Anders Arvesen and Edgar G. Hertwich, 2012, Renewable and Sustainable Energy Reviews 16(8): 5994-6006.

‘A single 3MW wind turbine needs ... 2 tons of rare earth elements.’ —Northwest Mining Association

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