AMES, Iowa — The Iowa State University Biopolymers and Biocomposites Research Team is investigating the production of carbon fibers from low-cost, lignin-based polymer blends for use in wind turbine blades.
Michael Kessler, associate professor of materials science and engineering, leads the project. “Our goal is to provide a low-cost, biobased carbon fiber that significantly outperforms glass fiber in composites for wind turbine blades,” said Kessler.
To meet energy guidelines set by the Department of Energy, wind turbine manufacturers are designing wind turbines with longer blades. Increased blade length improves wind capture at lower wind speeds and increases energy output. However, the additional length increases blade weight and the load experienced by the rotor hub and wind tower.
Currently most turbine blades are made from glass fiber reinforced polymers. These glass fibers are dense and weaken over time under repeated stress, which limits turbine blade length and performance. New lightweight, low-cost blades need to be developed, which led Kessler to begin investigating carbon fibers that could replace the glass fibers currently used in wind turbine blade manufacturing. Instead of using expensive petroleum-based carbon fiber, his research group is exploring ways to use lignin, a renewable resource, to create low-cost carbon fibers for use in manufacturing wind turbine blades.
Lignin is derived from plants and is a byproduct of the wood pulping process. It is an inexpensive, readily available material, and carbon fiber produced from lignin could lead to stronger and lighter wind turbine blades.
The lignin-based carbon fibers are produced using a manufacturing process called melt spinning. First the polymer is heated to a melted state and then extruded through a spinneret, a die with numerous holes. The polymer fibers are then wound and stretched into thinner fibers for further processing. Because lignin polymers are brittle and cannot be spun and spooled into fibers without modification, Kessler’s research group had to test ways to overcome this barrier. They are chemically modifying and blending the lignin with biopolymers to enhance polymer flexibility and improve the melt spinning process.
Kessler believes there is significant potential for making the carbon fiber production greener and renewable by blending lignin with biopolymers, such as the starch-based polymer polylactic acid (PLA), rather than using petroleum-based polymers such as polyethylene terephthalate (PET).
“The expected benefits are three-fold,” said Kessler. “It uses renewable resources, it optimizes energy and materials costs for producing carbon fibers (estimated cost savings 37 percent to 49 percent), and the fibers themselves will be used for wind turbine blades to produce renewable energy.”
Although this project is focused on wind energy applications, Kessler sees other potential applications for the lignin-based carbon fibers. For example, in the automotive industry, the replacement of steel structures with stronger and lighter carbon fiber reinforced polymers would lead to vehicle weight reductions of 30 percent to 50 percent. Such weight savings would result in very significant fuel efficiency improvements.
About the Biopolymers and Biocomposites Research Team
The Biopolymers and Biocomposites Research Team was established in 1995 to promote research and development of biorenewable polymers and composites from agricultural crops, encourage bioplastics in industry and work toward new formulations and processing techniques. The team operates under the Center for Crops Utilization Research umbrella at Iowa State University.