Rare-earth magnet supply and cost issues
Major industrial consumers of rare-earth permanent magnets (PMs)—such as generators for wind turbines and other large electrical machines—are in the spotlight but the impact of supply and cost is much more widespread. Data storage devices, medical equipment, electric vehicles, and solar panels are among various industries affected. The issue is also strategic since many high-tech military and defense systems rely on rare-earth (RE) magnets.
It’s a case of millions of devices requiring relatively small amounts RE materials versus thousands of large PM generators using huge amounts. Direct-drive (DD) generators for wind turbines are most affected, requiring as much as 265 kg (585 lb) of RE material per megawatt (MW) of power output. This is due to very high torques needed with slow-speed generators that turn at 4-20 rpm (see August 2011 Control Engineering article on “Direct-drive wind turbines”).
Markedly less RE material is needed as the generator’s operating speed increases. For example, “high-speed generators”—the type often used with traditional (geared) wind turbines—have about one-tenth the RE material requirement of DD generators, according to The Switch Controls & Converters Inc.
Rare-earth materials are not actually rare in the normal sense. They’re found in various parts of the world, but less widely in the concentrated form necessary to allow processing the RE elements into the strongest permanent magnets available today. Of some 17 RE elements, neodymium is most used, alloyed with iron and boron to form Nd-Fe-B permanent magnets.
Much has been said about the dominance of China in RE materials. Yet it’s estimated that China accounts for only about 40% of the world’s total rare-earth reserves, explained Anders Troedson, vice president and general manager of The Switch, in a paper at the recent Metals for Energy & the Environment 2011 conference in Las Vegas, NV (Ref. 1). Troedson mentioned nine mines or known resources of RE materials in six countries outside of China.
China does dominate mining of RE ore and is said to produce 95-97% of the global supply of rare-earth metals. That did not happen by accident. The world’s developed countries allowed control of the supply and processing of these vital materials to pass to China because short-term vision made that move appear economically viable.
At one time the U.S. was a major force in rare-earth magnet production. Today, there is very little production and rare-earth oxide (REO) mining is just restarting in the U.S. That scenario may be changing now that China has started limiting exports of RE materials to supply the rapidly growing needs of its own high-tech industries.
Molycorp Minerals—a Colorado-based domestic company and one of the resources noted by Troedson—began mining again this year to feed its limited production requirements. Full scale production (at a 20,000 mt REO per year rate) using new processes will come online in 2012. With accelerating demand and prices for RE materials, reopening of the above mines (or other dormant ones) and new mine exploration becomes a possibility.
As noted in the August 2011 Control Engineering article on direct-drive wind turbines, OEMs are looking at design alternatives. Henrik Stiesdal, CTO of Siemens Wind Power, mentioned the possibility of a direct-drive generator design “variant” not using rare-earth magnets to be available in case of RE material shortage. However, no further details were provided.
In a presentation at Motor Summit 2010 in Zurich (Ref. 2). Dr. Stefan Berchten, principal of MagnetDrives AG of Switzerland, concluded that PM production methods must be “reinvented,” which includes increasing the magnetic power of materials other than the highest rated rare-earth magnets. Direct-drive wind turbines were part of the discussion, although Berchten’s central theme was PM motors.
Further growth of wind turbine sizes exacerbates the issue for direct-drive generators. Besides large PM requirements, DD generators run into mechanical design constrains when approaching the eight to 10 MW power range, explained The Switch’s Troedson. He mentioned in the Aug. `11 CE wind turbine article that an alternative, medium-speed generator—with only one stage of gears—reduces weight and size of the unit while providing some DD advantages. An adjunct advantage of that design is substantially less RE magnet material required.
Research for alternatives is another promising area. For example, the U.S. Department of Energy (DOE) announced in late June 2011 the funding of six research and development projects at six organizations, focusing on “next-generation designs for wind turbine drivetrains.” Four of the R&D projects will include direct-drive generators of PM or non-PM type. Several projects apply to wind turbines up to 10 MW size and have the objective to reduce or eliminate the need for rare-earth magnets in the generator. One DOE project addresses the single-stage gearbox and generator combination similar to that mentioned by The Switch, but with a non-PM generator design.
Longer term rare-earth magnet outlook
Various recent technology conferences attest to concerns for the availability of these strategic materials. Besides Ref. 1 (above), the 26th International Rare Earth Research Conference, Santa Fe, NM (Ref. 3) was noteworthy. Keith Delaney, executive director of the Rare Earth Industry and Technology Association (REITA), outlined the pertinent issues and suggested longer term measures to ease current conditions in a plenary presentation entitled "Challenges Facing the Rare Earth Industry 2011–2020."
“China has no incentive to support supply chains outside of its borders,” Delaney said. “By 2015 China could be a net importer of rare-earth materials just to feed its own clean energy needs.”
A prime issue facing rare-earth project companies is to demonstrate a “reliable supply” of RE materials to OEMs. This includes shortening the five- to 12-year process to develop and commercialize a new RE resource, Delaney explained. “Adequate development funding must be available to accelerate the commercialization process.” With tight financial resources, Delaney suggested sources of funding and support for new RE projects from lending and capital markets and trading companies, among others.
As for OEMs, Delaney recommended that they fully understand and address vulnerabilities within their specific supply chains and plan for diversifying the supply. “OEMs must also interact with RE property developers and ‘the rest of its downstream supply chain.’ ” OEMs can demonstrate their commercial commitment through loans, letters of interest, and joint ventures. (REITA’s mission is to promote the creation of a commercially sustainable rare-earth industry and technology base to meet the growing global need for RE materials and products.)
Delaney also identified prime areas of “global collaboration” that can benefit all stakeholders involved in rare-earth materials. Industry cooperation is key to realizing any of the recommendations:
- Rebuild necessary intellectual infrastructures abandoned earlier
- Develop new high-yield processes to extract, separate, and refine rare-earth materials
- Develop technologies to improve manufacturing efficiency and reduce raw material waste downstream of RE processing and recycling of end-of-life products
- Develop methods to maintain coercivity of REPMs with minimal use or no use of dysprosium
- Pursue continued long-term, basic research on rare-earth material properties and chemistries.
“As long as there is a perceived supply gap—price and availability of rare-earth materials will continue to remain unstable and problematic to OEM sustained investment,” Delaney concluded.
Frank J. Bartos, PE, is a Control Engineering contributing content specialist. Reach him at email@example.com
Ref. 1 – Metals for Energy & the Environment 2011 (June 2-3)
“PM generators for wind turbines: topology, features and future trends”
Ref. 2 – MotorSummit 2010 (Oct. 26-28)
“PM motor development…applications and energy potential” http://motorsummit.ch/data/files/MS_2010/ms_int_10/8_berchten.pdf
Ref. 3 – 26th International Rare Earth Research Conference (June 19, 2011). http://www.reitausa.org/presentations-and-articles/