January 9, 2014
General News

Reported wind turbine blade breaks apparently involve carbon spars

Composites World | 1/9/2014 | www.compositesworld.com

Although it’s rarely recorded in HPC, wind turbine blades do occasionally fail. The magazine North American Windpower (published by Zackin Publications Inc., Waterbury, Conn.) recently reported on its Web site that on Nov. 20 a fourth 48.7m/160-ft blade had broken off a turbine supplied by GE Wind Energy (Fairfield, Conn.). That and three preceding breaks all occurred on GE 1.6-100 turbines; each failure happened either during or shortly after turbine commissioning. No one was injured in any of the failures.

Prior to the failures, the GE 1.6-100 turbine (see photo at right) was touted as the most popular U.S. wind turbine installation in 2012 by Navigant Research (Boulder, Colo.) and was named 2012 Turbine of the Year by Windpower Monthly (Hammersmith Media Group Ltd., London, U.K.) for kickstarting the large-rotor trend, which, when combined with modest generator power, has reduced the cost of energy. The turbine also helped GE surpass Vestas Wind Systems A/S (Aarhus, Denmark) as the number one turbine supplier in the world.

The most recent break occurred at Invenergy’s (Chicago, Ill.) California Ridge project in Illinois, on turbine #134. In this case, the failed blade struck another blade, and both fell to the ground. Three days earlier, a blade on turbine #34 at the company’s Orangeville wind farm in New York snapped near the hub, leaving a jagged stub. GE is in the process, reports North American Windpower, of investigating the breaks. Although GE Renewable Energy spokesperson Lindsay Theile says she can’t disclose much detail, a “suspect population” of 48.7m/160-ft blades has been identified, and GE is in the process of notifying other potentially affected customers. About 1.5 percent of the total GE wind turbine fleet of more than 22,000 could be affected, says Theile. More information might be available when a root cause analysis of the failures is complete.

Although the first two breaks (March 11 and Nov. 7) at Michigan wind farms operated by DTE Energy (Detroit, Mich.) occurred under similar circumstances, they looked very different. The first break, on Echo Wind Park’s #60 turbine, and the second break, on one of 40 turbines in Thumb Wind Park’s Sigel Township installation, both show separation of the blade along its length.

This year’s breaks followed two others in 2012, both in Illinois (see lower left photo). On one broken blade, at California Ridge, the carbon spar used in GE’s 48.7m blades can be clearly seen in a postbreak photo. According to a 2012 statement by GE’s Theile, an unspecified “isolated manufacturing issue was the cause of the two blade fault occurrences.” The March 11 break, at DTE’s Thumb Wind Park, was attributed by DTE to a failure in the carbon fiber spar “at the 19m [62-ft] mark.” The reported cause was an accidental two-hour oven shutdown during cure.

According to RechargeNews.com, the Echo Wind Park blade was made in Brazil. At the time, Tecsis (Sorocaba, Brazil) had a $1 billion contract to supply blades to GE for U.S. wind power projects from 2006 through 2010. In its 2012 Wind Turbine Overview for the World Bank, GE presented its 1.6-100 turbine blade-testing overview with a photo beside “Certification Requirements” titled “GE-Tecsis Collaboration,” indicating a close relationship between GE and Tecsis, and it is at least possible that the six failures in 2012-2013 involved Tecsis-built blades.

Founded in 1995 by aeronautical engineer Bento Koike, Tecsis was listed in 2012 as the second largest blade manufacturer in the world, behind LM Wind Power (Kolding, Denmark). A 2009 article in business magazine PIB (São Paulo, Brazil) claimed Tecsis had supplied half the blades in operation in North America and held more than 40 international patents on blade technology. Other published reports say Tecsis increased production from 10 or 12 to 30 per day, and the blademaker also has supplied Alstom (Levallois-Perret, France), Gamesa (Zamudio, Spain), Impsa (Buenos Aires, Argentina) and Siemens (Hamburg, Germany). Reportedly, Tecsis’ 2012 production was slated at 5,500 blades.

Tecsis described its largest blade as 50m/164 ft in length (i.e., the 48.7m blade for GE), originally weighing about 9 metric tonnes (19,840 lb), but now reduced, thanks to a “new” form of carbon fiber. Indeed, GE touts its 1.6-100 turbine’s lower weight and lists the blade at 6500 kg (14,330 lb). In 2008, GE showed infusing carbon fiber spar caps separately, laying them into dry fiberglass and balsa core blade shell layups, and then infusing the combined structures. Although Tecsis does develop materials and processes (M&P) for blades sold to its smaller/domestic customers, its large subcontract program M&P are specified by customers, e.g. GE, Siemens and Alstom. Tecsis must complete qualification tests before it can manufacture those blades. It seems likely that the “new carbon” material is Gurit’s (Isle of Wight, U.K.) oven-cured Sparpreg.

GE’s Katelyn Buress told HPC that it is performing thorough investigations of the recent breaks, but wouldn’t speculate about whether the breaks are related. “GE’s global fleet of 22,000 turbines has over 500 million safe operating hours and it is working closely with customers to maintain this success,” she stated.

Time will tell what these blade failures might have in common, but it is clear that they are quite different from blade failures experienced by Gamesa in 2007 and by Siemens earlier in 2013. For Gamesa, a defect in a 1-ft/0.3m long applicator produced an irregular line of adhesive, causing splintering and breakage in 13 of nearly 400 blades produced at its Ebensburg, Pa., plant that year. Seven blade failures were first observed at the Allegheny Ridge Wind Farm in Pennsylvania. The problem was corrected, and the blades were replaced. Siemens responded quickly to two B53 (53m/174-ft) blade failures in its SWT-2.3-108 turbines at the Eclipse wind farm in Iowa and the Ocotillo Wind project in California. It immediately curtailed production of that turbine, performed a root-cause analysis and determined the cause was failure of the adhesive bond between precast root segments and the main blade fiberglass laminate due to insufficient surface preparation. All B53 blades have been inspected, and most are back in operation. Siemens will replace a number of blades due to delamination and will apply a minor modification in the field to all B53 blades that are not replaced, incurring $131 million in charges on the company’s third-quarter 2013 results.

URL to article:  https://www.wind-watch.org/news/2014/01/09/reported-wind-turbine-blade-breaks-apparently-involve-carbon-spars/