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(Almelo, Netherlands), a Dutch rotor blade design and technology supplier, announced completion of end-to-end blade tests in India for a novel 2.5-3-megawatt (MW) rotor blade currently under development at a global wind blade manufacturer. After designing the blade structure in the Netherlands, partner  (Gujarat, India) produced the mold for the prototype that wind turbine manufacturer  (Pune, India) subsequently tested for load and fatigue. The results met IEC61400-5:2020 certification, the production standard for engineering integrity of wind turbine blades.

Eight months of design and engineering work preceded the rotor blade’s final validation testing. This included the blade’s structural design, the infusion process used for the materials — carbon fiber and epoxy resin — as well as training for the production of two molds and one complete rotor blade prototype. Passing these validation tests, the rotor blade is ready for serial production.

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The standard IEC 61400-5:2020, issued by independent test service provider, TÜV Rheinland (Cologne, Germany), specifies the requirements for the engineering integrity of wind turbine blades and operational safety and includes aerodynamic, structural design and material selection. The certification provides the technical reference for designers and manufacturers among others.

“From an engineering perspective, this result is motivating,” says Arnold Timmer, managing director of We4Ce. “We had a very tight schedule of just eight months, which is a challenge, especially for the production of mold and prototype. In the end, successful TÜV certification proved that our engineering design will work in practice.”

We4Ce notes that its materials and methods differ from more traditional rotor blade development. “Unlike many others, we do not use pultrusion materials. In fact we consider these with some reservation, preferring to use infusion and a lower cost dry fabric-infused carbon fiber [for the spars],” explains Edo Kuipers, technology director and co-founder of We4Ce. Kuipers has spent the last 27 years in rotor blade design, founding We4Ce in 2008. “While pultrusion is a trending method, we believe it still needs to be proven long-term as it is costly and too technically risky without this long-term experience.” Kuipers points to infusion’s ability to offer uniform material distribution, thereby reducing the risk of cracks and delamination.

We4Ce is always considering its customer needs (blade manufacturers) to reduce/keep costs in check; its objective is to achieve a balance between costs and performance, including strength and aerodynamics. “We use infusion methods for our [carbon fiber spar] blade designs, and this enables our customers to use dry fabrics,” says Kuipers. “Our prescribed carbon fibers may cost as much as half of the carbon fiber that would be used in the pultrusion process, so that has huge cost-saving potential. We believe our method will offer endurance with minimum risk of technical problems 5-7 years down the line, which we believe is the point in time you can tell how good the original process was.”

Kuipers notes that infusion also works well for blade root inserts (the bushings that join the blade with the hub via bolts). In a 2.5-MW turbine design, We4Ce increased the root insert’s load-carrying capability by 20%.

For this project in particular, We4Ce trained technicians from Suzlon and InDutch Composites Technology to use its infusion method for prototype production. Carbon fibers and epoxy resin were placed in the mold and then vacuum processed for uniform distribution. Following prototype production, Suzlon performed static load tests, dual-axis fatigue and post-fatigue tests, simulating a 20-year lifecycle performance.

Offering full service from documentation, drawings, static to fatigue testing requirements, We4Ce supports training blade manufacturers worldwide during prototype blade production on-site. Currently, 40 customized rotor blade engineering designs have resulted, from 900-kilowatt, 23-meter-long blades to 14-MW, 108-meter-long blades.