New Carbon Fibre for Wind Turbine Blades Could Bring Cost and Performance Benefits

A new carbon fibre material could bring cost and performance benefits to the wind industry if developed commercially, according to a study led by researchers at Sandia National Laboratories.

Wind blades containing carbon fibre weigh 25% less than ones made from traditional fibreglass materials. That means carbon fibre blades could be longer than fibreglass ones and, therefore, capture more energy in locations with low wind. A switch to carbon fibre could also extend blade lifetime because carbon fibre materials have a high fatigue resistance, said Brandon Ennis, a wind energy researcher at Sandia Labs and the principal investigator for the project.

The project is funded by DOE’s Wind Energy Technologies Office in the Office of Energy Efficiency and Renewable Energy. Partners on the project include Oak Ridge National Laboratory and Montana State University.

Of all the companies producing wind turbines, only one uses carbon fibre materials extensively in their blade designs. Wind turbine blades are the largest single-piece composite structures in the world, and the wind industry could represent the largest market for carbon fibre materials by weight if a material that competed on a cost-value basis to fibreglass reinforced composites was commercially available, said Ennis.

Cost is the main consideration during component design in the wind industry, yet turbine manufacturers also have to build blades that withstand the compressive and fatigue loads that blade experience as they rotate for up to 30 years.

Ennis and his colleagues wondered if a novel low-cost carbon fibre developed at Oak Ridge National Laboratory could meet performance needs while also bringing cost benefits for the wind industry. This material starts with a widely available precursor from the textile industry that contains thick bundles of acrylic fibres. The manufacturing process, which heats the fibres to convert them to carbon, is followed by an intermediate step that pulls the carbon fibre into planks. The plank-making pultrusion process creates carbon fibre with high performance and reliability needed for blade manufacturing and also allows for high production capacity.

When the research team studied this low-cost carbon fibre, they discovered it performed better than current commercial materials in terms of cost-specific properties of most interest to the wind industry.

ORNL provided developmental samples of carbon fibre from its Carbon Fiber Technology Facility and composites made from this material as well as similar composites made from commercially available carbon fibre for comparison.

Colleagues at Montana State University measured the mechanical properties of the novel carbon fibre versus commercially available carbon fibre and standard fibreglass composites. Then Ennis combined these measurements with cost modelling results from ORNL. He used those data in a blade design analysis to assess the system impact of using the novel carbon fibre, instead of standard carbon fibre or fibreglass, as the main structural support in a wind blade. The study was funded by the U.S. Department of Energy Wind Energy Technologies Office.

Ennis and his colleagues found that the new carbon fibre material had 56% more compressive strength per dollar than commercially available carbon fibre, which is the industry baseline. Typically, manufacturers accommodate a lower compressive strength by using more material to make a component, which then increases costs. Considering the higher compressive strength per cost of the novel carbon fibre, Ennis’ calculations predicted about a 40% savings in material costs for a spar cap, which is the main structural component of a wind turbine blade, made from the new carbon fibre compared to commercial carbon fibre.