It marks a move to lower cost materials by the wind energy sector, as manufacturing difficulties are gradually overcome.
The advantage that polyurethane resin has over epoxy resin is that it flows more easily and ensures better wetting of the fibers used for reinforcement, and can be processed more quickly.
“This is a clear cost advantage for manufacturers,” said Kim Klausen, head of Covestro’s global wind energy program. “After all, rotor blades account for around a quarter of the total cost of new wind turbines.”
Much of the saving come in the processing of the materials, as well as the materials themselves being cheaper. The half-shells for the rotor blades are efficiently manufactured using the vacuum infusion process. This involves placing the core materials and glass fibre fabrics in a mould and sealing the structure hermetically with a film. Once the vacuum has been created, introducing the liquid resin starts the infusion process.
Thanks to the vacuum, the process only requires a relatively short cycle time and prevents the formation of cavities.
In addition, the blade used glass fibre as opposed to the more expensive, but stronger, carbon fibre. It’s thought the properties of polyurethane will make up any shortfall in mechanical properties, though tests will confirm by how much.
The project provides important evidence that a polyurethane resin is suitable for industrial production. Covestro is planning to produce further prototypes.