US: NREL developing recyclable wind turbine blade

The U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) has manufactured a wind turbine blade made of thermoplastic resin that can be recycled, and has now demonstrated its feasibility and structural integrity in partnership with Arkema Inc of Pennsylvania.

Photo: Dennis Schroeder, NREL

This has been done with a 13-metre thermoplastic composite blade compared to a near-identical thermoset blade, after NREL had previously demonstrated the feasibility of the thermoplastic resin system by manufacturing a 9-metre composite wind turbine blade.

NREL researcher working on a thermoplastic composite turbine blade at the Composites Manufacturing Education and Technology Facility at NREL's Flatirons Campus.
NREL researcher Robynne Murray working on a thermoplastic composite turbine blade; Photo: Dennis Schroeder, NREL

The research demonstrated the advantages of moving away from the currently used thermoset resin system, which requires more energy and manpower in the manufacturing facility, and the end product often ends up in landfills, according to NREL.

“Switching to thermoplastic resin would make wind turbine blades more recyclable, and can also enable longer, lighter-weight, and lower-cost blades”, NREL states.

Furthermore, a new technoeconomic model has been developed to explore the cost benefits of using a thermoplastic resin, as current wind turbine blades are made primarily of composite materials such as fiberglass infused with a thermoset resin.

The manufacturing process using epoxy thermoset resin needs additional heat to cure the resin, adding to the cost and time to manufacture blades, while thermoplastic resin cures at room temperature.

The process does not require as much labor, which currently accounts for about 40 per cent of the cost of a blade. The new process, the researchers determined, could make blades about 5 per cent less expensive to make, according to NREL.

“The thermoplastic material absorbs more energy from loads on the blades due to the wind, which can reduce the wear and tear from these loads to the rest of the turbine system, which is a good thing”, said Robynne Murray, NREL’s research engineer.

The thermoplastic resin could also allow manufactures to build blades on site, alleviating a problem the industry faces as it trends toward larger and longer blades. As blade sizes grow, so does the problem of how to transport them from a manufacturing facility, NREL pointed out.