To solve the problem, Covestro has developed a urethane-based elastomer that, in tests – where the blades are blasted with water at very high speed – can help deliver an almost 10-fold improvement in the wear resistance of the blade.
“It is always the leading edge that gets damaged because it is hitting rain drops at almost supersonic speeds,” said the Covestro boss, noting that the company has also developed new urethane-based alternatives to polyester or epoxy for the blade construction.
In tests, conventional blades last up to 150 minutes and are destroyed, whereas Covestro’s design has already hit up to 24 hours, which equates to “a massive improvement in longevity,” the CEO reported.
The part is based on a polyurethane elastomer developed at Covestro’s global wind power centre in Otterup, Denmark. It can be moulded or, later on, formed into a U-shape, which is applied onto the edge of a rotor blade, closest to the tip.
Thomas declined to provide further details about the elastomer composition, apart from saying that its performance is due to an “special urethane chemistry” developed at the Danish competency centre.
In response to a subsequent ERJ enquiry on this point, a Covestro spokesman said the elastomer “is not a real TPU.” Instead, he described the material as “semi-TPU processed: it is a two-component system, but not a thermoplastic.”
The company is still in a test phase with an independent testing institute and several cooperation partners towards commercialisation of the technology, the spokesman added.
Underlining the potential of the project, Thomas said: “If you can get to the point where the blade last 20 years, the whole economics of wind power changes because the depreciation cost within the breakeven point is spread over 20 years, instead of just seven years at the moment.
This, added the Covestro boss, is particularly the case for offshore turbines, where blades are already up to 100 metres long, with the next generation approaching 150 metres for higher efficiency.
“There are a number of companies around the world now testing the technology in production,” he said. “The focus is on the market in China, where we have actually made blades and are at the early adoption stage.”