Reported wind turbine blade breaks apparently relates to spar failures

Flaws in popular U.S. turbines blade reportedly attributed to isolated

manufacturing defects.

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Although its 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 Invenergys (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 companys 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 cant 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 Parks #60 turbine, and the second break, on

one of 40 turbines in Thumb Wind Parks Sigel Township installation, both show

separation of the blade along its length.

This years 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 GEs 48.7m blades can

be clearly seen in a postbreak photo. According to a 2012 statement by GEs Theile, an

unspecified isolated manufacturing issue was the cause of the two blade fault

occurrences. The March 11 break, at DTEs 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 (So 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 turbines 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. (Note: Tecsis

blades for the latter do not include carbon fiber.) Tecsis must complete qualification tests

before it can manufacture those blades. It seems likely that the new carbon material is

Gurits (Isle of Wight, U.K.) oven-cured Sparpreg.

GEs Katelyn Buress told HPC that it is performing thorough investigations of the recent

breaks, but wouldnt speculate about whether the breaks are related. GEs 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, both of which were related to adhesive bonding issues. 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 companys

third-quarter 2013 results.