Wind Turbines Shed Their Gears

Wind turbine manufacturers are turning away from the industry-standard gearboxes and generators in a bid to boost the reliability and reduce the cost of wind power. 

Siemens has begun selling a three-megawatt turbine using a so-called direct-drive system that replaces the conventional high-speed generator with a low-speed generator that eliminates the need for a gearbox. And last month, General Electric announced an investment of 340 million euros in manufacturing facilities to build its own four-megawatt direct-drive turbines for offshore wind farms. 

Power ring: This three-megawatt wind turbine uses permanent magnets and a design that makes it significantly lighter than a conventional geared turbine.  

Most observers say the industry's shift to direct-drive is a response to highly publicized gearbox failures. But Henrik Stiesdal, chief technology officer of Siemens's wind power unit, says that gearbox problems are overblown. He says Siemens is adopting direct-drive as a means of generating more energy at lower cost. "Turbines can be made more competitive through direct-drive," says Stiesdal. 

Siemens's plans hinge on a new design that reduces the weight of the system's generator. In conventional wind turbines, the gearbox increases the speed of the wind-driven rotor several hundred fold, which radically reduces the size of the generator required. Direct-drive generators operate at the same speed as the turbine's blades and must therefore be much bigger--over four meters in diameter for Siemens's three-megawatt turbine. Yet Siemens claims that the turbine's entire nacelle weighs just 73 metric tons--12 tons less than that on its less powerful, gear-driven 2.3-megawatt turbines.

Much of the weight reduction comes from the use of permanent magnets in the generators' rotor--a trick that GE is also using. Conventional turbine generators use electromagnets--copper coils fed with electricity from the generator itself. Henk Polinder, an expert in permanent-magnet generators at Holland's Delft University of Technology, says that a 15-millimeter-thick segment of permanent magnets can generate the same magnetic field as a 10- to 15-centimeter section of copper coils.

Stiesdal says Siemens reduced weight further by inverting its generator's design. Rather than a steel rotor covered with permanent magnets spinning inside a stationary doughnut-shaped stator (the design GE is using in its four-megawatt direct-drive turbine) Siemens's rotor is a steel cylinder with permanent magnets on the inside, and this rotor spins around a column-like stator. 

Siemens erected a prototype of its machine in Brande, Denmark, in December and plans to install 10 more this year, primarily in Denmark, before beginning mass production in 2011. GE's technology, which it acquired with the purchase of Norwegian turbine producer ScanWind last year, is being demonstrated at a test site in Norway; commercialization of its four-megawatt machine is slated for 2012. 

More competition is on the way. Venture capital firm New Enterprise Associates is backing a Boulder, CO-based startup called Boulder Wind Power, which is developing a 1.5-megawatt direct-drive turbine. The firm was founded in December by Sandy Butterfield, who was chief engineer for the U.S. National Renewable Energy Laboratory's (NREL) wind technology center, where he led a major study of the gearbox design process. 

Whether gearbox failures are an industrywide problem remains a matter of some contention. NREL initiated its study in 2007, when there were several failures: a U.S.-based company, Clipper Windpower, experienced serious gearbox problems within months of installing the first of its 2.5-megawatt turbines at a wind farm in Lackawanna, NY, while gearboxes in the 30 Vestas Wind Systems turbines forming the U.K.'s offshore Kentish Flats wind farm had to be replaced after just two years of operation. NREL concluded that most wind turbine gearboxes would fail "well before" their 20-year design life. 

Stiesdal says Siemens's own studies show that gearboxes are quite reliable, overall. A 2008 analysis of Siemens machines installed from 1983 to 1989 in the U.S. found that the "vast majority" were still operating with their original gearboxes. But he does expect increased reliability from the direct-drive system, which has about half as many parts as a conventional turbine.

Direct-drive systems do introduce one potential problem, however. There are ongoing concerns regarding the future supply of the rare earth metals used to make permanent magnets. "That's a serious issue," says Stiesdal. 

By Peter Fairley
From Technology Review


To relieve Siemens's potential problem of “ongoing concerns regarding the future supply of the rare earth metals used to make permanent magnets”, U.S. Rare Earths, Inc. (, an American owned and operated resource company holds enough accessible American light and heavy rare earth reserves to allow metal processors, magnet fabricators and magnet using device fabricators to become competitive in the global market.

U.S. Rare Earths, Inc. Announces Strategic Review

Press Release Source: U.S. Rare Earths, Inc. On Monday June 14, 2010, 8:01 am EDT
June 14, 2010 08:01 AM Eastern Daylight Time
SALT LAKE CITY--(BUSINESS WIRE)--U.S. Rare Earths, Inc. (“U.S. Rare Earths, Inc.” or the “Company”), a private company, announced today that it has initiated a review of strategic alternatives to enhance shareholder value, including those involving a possible merger, sale or other transaction. The Board of Directors of the Company has engaged Pope and Company Limited ("Pope") to act as the Company's financial advisor.
U.S. Rare Earths, Inc.’s Chief Executive Officer, Edward Cowle, explained that growing awareness by the U.S. government of Chinese dominance in the rare earth element (“REE”) market continues to increase the value of the Company’s REE reserves. In particular, the U.S. Government Accountability Office (“GAO”) report issued in April demonstrates the need for the Department of Defense to mitigate REE supply chain risks. Cowle stated, “The GAO has recognized U.S. Rare Earths, Inc.’s resources as a key component in the effort to expand domestic production of light and heavy REEs.”
U.S. Rare Earths, Inc. holds 169 unpatented mining claims of individual major vein deposits of REEs in the Diamond Creek and the Lemhi Pass areas of Idaho and Montana. The United States Geological Survey (“USGS”) reported total rare earth oxide (“TREO”) concentrations of 0.59 to 5.51% and an overall grade of resource of 1.22% TREO at Diamond Creek. TREO content of recent sampling of a number of the veins at Diamond Creek by U.S. Rare Earths, Inc. ranged from about 0.06 to 4.3% with an average TREO of about 1.2%. The USGS also reported average TREO concentration of 0.52% at Lemhi Pass.
According to reports by the USGS, the Company’s REE deposits are:
• one of the two largest reported historical estimates of REEs in the U.S.;
• one of only six proven, substantial deposits of REEs in the world outside of mainland China or Chinese control; and
• The only significant U.S. REE deposit that has heavy REE (“HREE”) concentrations.
(1) Reserve and Resource amounts provided are estimated from reported historical amounts under applicable definitions and standards used by the USGS or respective private company at the time such amounts were reported. Amounts provided are not compliant with applicable Canadian NI 43-101 or SEC Industry Guide 7 (SME) or other applicable laws. Amounts reported are for informational purposes to the CIM.

In addition, recent geologic investigation by the Company including age dating of mineralization and of igneous intrusive rock at Lemhi Pass indicates that the age of rare earth and thorium mineralization is Devonian (350 Ma) and that of previously unknown alkali complex intrusive rock as Cambrian (500Ma). Recent and ongoing work suggests the potential for a larger buried mineralized system possibly similar in nature to peralkaline REE-Th, IOCG/Fe-REE and/or carbonatite models of deposition. Historical and recent work by the Company at Diamond Creek suggests similarities to Lemhi Pass and also includes a potential for a larger buried Fe-REE-Th system.
“We are committed to finding a partner or buyer that has the financial capability and resources to ensure that the properties are developed as rapidly as possible,” said Cowle.
For further information regarding the strategic review process:
Pope & Company Limited
Grant White, 416-588-6139
Justin Sim, 416-588-9780
For further information regarding U.S. Rare Earths, Inc.:
U.S. Rare Earths, Inc.
Patrick Kennedy, 254-559-6464
Stern & Co.
Stephanie Stern, 212-888-0044

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