Following a thorough investigation, GE says a ‘spar cap manufacturing anomaly’ is to blame for the recent blade breaks at the Orangeville Wind Farm in New York and Echo Wind Park in Michigan. The company has identified other customers whose turbines are subject to the anomaly and is working to perform blade replacements.
As Dan Shreve, a partner at MAKE Consulting, explains, a spar cap is a "key structural element within the blade that carries the bending load of the blade."
"If you look at the internal structure of a blade that uses a shear web/spar cap type design, it resembles an I-beam," he says. "The spar cap represents the top and bottom elements of that I-beam with the shear web in the middle connecting the two spar caps."
Last month, NAW reported about four GE blade breaks that occurred this year, all of which involved the company's 1.6-100 wind turbines with 48.7-meter blades. Two of the affected wind farms were still undergoing construction or commissioning, and the other two were operational.
On Nov. 17, Invenergy stopped its efforts at the 94 MW Orangeville project after a blade fell to the ground, and 10 days prior, DTE Energy had ceased work on its 112 MW Echo Wind Park after a similar incident. According to GE's root-cause analyses, both of those incidents were due to the spar cap manufacturing anomaly.
Invenergy, which had finished construction at the Orangeville Wind Farm and began commissioning its wind turbines before the blade failure, says the developer is now resuming work on the project.
"The investigation of turbine blades at the Orangeville Wind Farm involves a thorough inspection of each individual blade," Invenergy explains in a statement. "This process is ongoing, as GE personnel makes its way through the Orangeville fleet, turbine by turbine.
"After extensive consultation with GE, Invenergy is resuming commissioning and operations activity at Orangeville on turbines cleared by GE," the developer continues. "We have confidence in the safe operation of these turbines. Moving forward, we will continue to resume activity incrementally as each unit is cleared as safe to operate."
As for DTE Energy's Echo project, utility spokesperson Scott Simons says, "The project is still offline as we work with GE to make sure that no other blades at Echo are at risk. We expect that review to go into January, but some turbines may begin operations as they are cleared." When the blade failure occurred, workers had erected – and commissioned along the way – 59 of Echo's 70 wind turbines.
Lindsay Theile, a GE spokesperson, says the company has determined separate causes for the blade failures at the two operational wind farms.
According to Theile, an investigation at Invenergy's California Ridge wind farm in Illinois revealed that a blade broke on the night of Nov. 20, not because of the spar cap issue, but because of "extreme weather." An Invenergy spokesperson further tells NAW that the blade was struck by lightning. The project's other 133 turbines remain operational, and GE is currently repairing the affected 134th unit.
In addition, Theile maintains that the March blade failure at DTE Energy's Thumb Wind Park in Michigan is unrelated to the other incidents. Following an investigation earlier this year, GE had discovered a separate "isolated supplier manufacturing defect" that the company says was later addressed and fixed. Thumb Wind has been online ever since.
GE's 48.7-meter blades are on a variety of the company's wind turbine models, but most are featured on the 1.6-100. In November, GE determined a "suspect population" representing about 1.5% of its total blades in the company's wind turbine fleet of over 22,000. All blades within the population have now been analyzed, and of that 1.5%, Theile says a "small percentage" have been identified as affected by the spar cap manufacturing anomaly.
MAKE Consulting's Shreve notes he is not surprised that the blade breaks have been tied to the spar cap.
"The type of blade failure – in this case, a rapid large-scale structural failure – generally lends itself to an issue with the spar caps," he comments. "It is not a common failure mode and, as such, is often due to some sort of manufacturing defect.
"That said, design shortcomings are not unheard of with respect to blade failures, as is evidenced by a number of large-scale blade retrofit/replacements programs over the past five years," Shreve continues. "In terms of the cause of this particular issue, GE's use of carbon fiber in its blades provides a very low-weight, high-performance design, but does introduce manufacturing complexity in terms of material storage, material handling and, of course, the lay-up of those carbon fiber prepreg elements."
Now that GE has discovered the root cause of the failures, the company is quietly swapping out affected blades. "We're working with our customers to replace any impacted blades and get the turbines back up and running as quickly as possible," says Theile.
Shreve notes that a blade-replacement program could cost wind turbine companies millions of dollars. For example, Siemens incurred over $130 million in charges after dealing with its own "adhesive bonding failure" issues earlier this year. However, because GE will not disclose exactly how many of its blades were affected by the spar cap issue, it's not possible to calculate just how big of a financial hit the company might take.
In addition to performing blade replacements, Theile says GE is implementing proactive actions. "[T]he quality and reliability of GE turbines is of utmost importance to us, and we are proud of our quality track record," she adds. "Following the discovery of the manufacturing anomalies, we have put additional controls in place to prevent future events from happening, including resourcing GE inspectors who are performing additional quality reviews and data verification, as well as oversight from GE Engineering."
Theile says GE does not plan to disclose any more details, including the names of affected wind projects or the blade supplier.