DNV approved the use of epoxy γm1 value for some design parameters.
HAMBURG, Germany, 20 December 2021 – DNV has issued the first verification letter for polyurethane used in wind turbine blades with a long-term degradation partial reduction factor of γm1 to Covestro, a leading manufacturer of high-tech polymers.
In line with DNV’s wind turbine rotor blade standard DNV-ST-0376, Covestro evaluated the influence of long-term degradation in polyurethane resin using extensive long-term degradation comparison testing and analysis. Based on this testing, DNV approved the use of adjusted material properties to include the effect of long-term degradation, in combination with a reduced γm1, Covestro’s Baydur 78BD085 resin with Desmodur 44CP20 hardener.
“As wind turbines increase in size, the failure of key components such as rotor blades can lead to significant losses for all project partners involved, explains Kim Sandgaard-Mørk, Executive Vice President for Renewables Certification at DNV. “ This is why manufacturers constantly work on improving the quality and reliability of wind turbine components. We are happy to see that suppliers like Covestro are introducing optimized materials which will help to lower the levelized cost of energy, making wind energy one of the most economical sources of energy generation. “
Dr. Irene Li, R&D Vice President of Tailored Urethanes Business Entity at Covestro in Asia Pacific said: "The certification granted by DNV proves that the excellent performance of polyurethane has been recognized by the certification authority in the wind power industry. As more and more polyurethane blades are being installed, we look forward to further innovation of polyurethane resin and the rapid development it will produce for the wind power industry."
γm1 factor is an important index to reflect the long-term degradation of blade material, and therefore to measure the long-term performance of the blade. The DNV-ST-0376 standard requires a more conservative value of γm1 for polyurethane than epoxy, which makes the design of polyurethane blades more challenging. However, based on extensive analysis of Covestro’s test results by DNV, the long-term degradation effect was for the first time quantified for Covestro’s Baydur 78BD085 resin with Desmodur 44CP20 hardener. By using the accurate material properties, the blade designer can make full use of the mechanical properties of polyurethane in the design process.