Exposure to sunlight, freezing temperatures and precipitation can erode the leading edge of wind turbine blades, shortening the life of the blade and reducing the overall productivity of the turbine. With turbine blades getting longer, from around 50 meters just a few years ago to 80 meters or more today, the force of natural elements working to degrade a blade’s leading edge has increased.
A Danish company believes it has found a solution. PolyTech’s ELLE (Ever Lasting Leading Edge) is a polyurethane shell applied to turbine blade tips. The product has been likened to a “swim cap” for turbine blades.
According to Mads Kirkegaard, PolyTech’s CEO, the incumbent solutions on the market can be divided into two groups: paints and tapes. But, he wrote in an email, these solutions are “not working good enough in most areas. Paints have been developed slightly over time but do not deal with the problems once and for all.”
“The real problem," he said, emerged during the shift from 45-meter blades to 60-meter blades. "During the development of those blades, the performance of the shorter blade was not yet known. So as the problem become known (after four to six years in operation), the number of blades put on the market was just crazy.”
“A very critical issue for the wind energy industry”
Aaron Barr, senior consultant, Wood Mackenzie Power & Renewables, confirmed in an email that blade protection is becoming an increasingly important concern for project owners. Barr specializes in wind turbine technology and operations and maintenance.
“Blade leading-edge erosion has become a very critical issue for the wind energy industry,” he wrote. “If the leading edge of the blade is not properly maintained, the gel coat and paint can erode over time, exposing the composite structure of the blade. This can lead to a significant reduction in energy production, as the aerodynamic performance of the blade is impaired.”
“If erosion is left unattended for too long,” he continued, “it can lead to costly blade repairs and in some cases has contributed to catastrophic blade failure.”
Barr, like Kirkegaard, cited longer blades as one of the factors exacerbating turbine degradation. “This issue has been made worse by a number of factors, including the aging wind fleet and longer blades that are spinning at higher tip speeds.”
The solution most often used by project owners today is tape that must be replaced at least a few times during a turbine’s life, he said. Not surprisingly, it’s much cheaper to install blade protection in the factory.
“One of the largest issues is the high cost of field installation," said Barr. "The cost of installing these solutions in a factory is substantially lower than in the field, as a field installation requires specialized rope-access technicians or a suspended platform to install.”
He added: “Factory installations are also controlled environments, which makes the quality of the installation much less susceptible to environmental variables that can cause leading edge treatments to fail prematurely.”
Deployment in the field
So how much can installing ELLE protection save wind turbine project owners? “There is not an easy answer to that. The costs vary a lot,” said Kirkegaard. The range depends on factors such as the project site, weather and the size of the turbines.
PolyTech told the Denmark-based publication Energy Watch, “In a modeled example, a 3 percent production loss for 400 MW offshore wind farm in the North Sea with 60 to 70 turbines would amount to DKK 20 million [$3.085 million] in productivity loss, if the turbines are allowed to operate for one year without repair.” ELLE could theoretically get at a sizable chunk of that number.
Kirkegaard told GTM that 30 wind turbine project operators and OEMs have installed the ELLE product on a total of 3,000 turbine blades globally. He declined to name the customers. Companies are not ready to go public, he said, because they are still testing ELLE.
“A vast number of operators are testing the product on a few turbines before going big,” he said.
GTM asked about the performance of turbines already outfitted with ELLE protection.
“None have failed — but that’s not the same as lasting 25 years,” said Kirkegaard.
Wood Mackenzie’s Barr said because ELLE is just entering the market he couldn’t comment on its performance or effectiveness compared to competing products.
However, he said, “It appears to be a well-researched concept with a focus on robust and simple field application.”
He cautioned that ELLE may not be a comprehensive solution to blade degradation, though.
“This solution is only aimed toward the tip of the blades, but leading-edge erosion occurs over the entire span of the blade,” he said. “The erosion is typically worst at the tip, due to higher speeds. But this application may not address in-board leading-edge erosion.”