European collaborations lead the way in sustainable wind energy production.
by Marie O’Mahony
The Biden administration is wasting little time putting plans in place to achieve the goal of a carbon-free energy sector by 2035. Offshore wind energy is an important part of a vision that seeks to combine environmental, employment and industrial benefits. Danish companies Ørsted A/S, Vestas Wind Systems A/S and Norwegian energy company Equinor have led the way so far in offshore wind farms.
The U.S. is looking to catch up, and Jamie MacDonald, energy analyst for global energy consultancy Xodus, is enthusiastic. “The pipeline, the opportunity, is there for [the U.S.] to really be the world leaders in this,” MacDonald says.
Carbon and glass fibers are crucial in building high strength-to-weight ratio wind turbine blades, and as the first generation of wind turbine blades nears their end of life, the textile industry is increasingly looking at ways to recycle the carbon and glass fibers, as well as the blades themselves.
In March this year Denmark approved plans to build an artificial island with two hundred offshore wind turbines in the first phase of a project that will ultimately be capable of meeting the energy requirements for the country, with excess to sell to neighboring countries.
Each wind turbine is expected to be around 260 meters tall to maximize energy capability, and with this comes correspondingly long blades and a larger nacelle that houses the generating components. Already, an estimated 2.5 million tons of composites are being used in wind turbines, of which at least 85-90 percent are capable of being recycled. To do so to scale—and economically—is a challenge that the industry is actively seeking to address.
Recycling in a big way
The European DecomBlades consortium is establish a recycling industry for composites with members including key industry players: Ørsted, LM Wind Power, Vestas Wind Systems, MAKEEN Power, HJHansen Recycling and FLSmidth from Denmark; Siemens Gamesa Renewable Energy S.A. based in Spain;, the Energy Cluster Denmark (ECD), University of Southern Denmark (SDU) and Technical University of Denmark (DTU).
They are investigating three approaches. The first is shredding wind turbine blades so that the recycled material can be reused in different products and processes; the second is the scaled use of shredded blade material in cement production; the third uses pyrolysis, a method of separating the composite material using high temperatures. Vestas, global chemical company Olin Epoxy and partner universities in Denmark have established the Circular Economy for Thermosets Epoxy Composites (CETEC) project as a step towards increasing this recycling goal.
The method involves disassembling the composites into fiber and epoxy. This is then broken down further using a “chemcycling” process to produce materials that can be used in the manufacture of new wind turbine blades. The chemcycling of epoxy-based materials allows highly stable polymer chains to be converted into molecular building blocks. These are easily processable for use in a new epoxy, without loss of quality.
“Avoiding the loss of valuable molecular complexity in such a way is a highly desirable concept and an important step to sustainable materials,” says Dr. Troels Skrydstrup professor at Aarhus University, which is a consortium partner.
The University of Strathclyde in Scotland have signed a Memorandum of Understanding (MOU) with Aker Offshore Wind and investment firm Aker Horizons to develop the facility for recycling wind turbine blades. The university’s Regenerated Composite Value Reinforcement (ReCoVeR) technology enables glass-reinforced plastics (GRP) to be recycled to “near virgin quality” glass fiber that can be reused in composites achieving 80 percent of its original strength.
The technology involves thermally treating reclaimed glass fiber from the GRP composite waste, a process that deals efficiently with contaminated materials and other waste. “Retaining and redeploying the embodied energy in the fibers is essential as we move to a more circular economy,” according to Liu Yang, head of the Advanced Composites Group at the university. A further value seen by the university is economic, with estimates showing a cost for resale at 80 percent that of virgin glass fiber.
“There’s a massive environmental problem from the nearly three billion dollars’ worth of new carbon fiber scrap generated every year by the global supply chain—not to mention the end-of-life scrap from large structures like airplanes and wind turbine blades,” says Anvesh Gurijala, CEO and co-founder of Massachusetts-based materials science company Boston Materials.
His comments came as the company announced the closing of an $8 million financing deal to accelerate the expansion of the company’s Z-Axis Carbon Fiber technology, which provides a high-performance outlet for the growing amount of available, reclaimed carbon fiber, which it believes is creating a new economic opportunity in the composites and lightweight materials industries.
Earlier this year, the company commissioned a 60-inch-wide commercial production line capable of producing 800,000 square meters of Z-axis carbon fiber materials annually, with plans to triple the production capacity over the next two years. Installed in a 37,000 square foot manufacturing facility in Billerica, Mass., it also has fully automated equipment for quality control and traceability. Designed to offer a replacement for heavier metals, they are also looking at the value to the environment by reducing the reliance on virgin materials.
In Europe, the German Institutes of Textiles and Fiber Research Denkendorf (DITF) have developed textile semi-finished products using recycled carbon fibers (rCF). These are obtained by combining rCF fiber flocks with matrix staple fibers that can be fed into a carding process to produce an intermediate product needed for nonwoven and yarn production, the card web of preorientated rCF and matrix fiber.
For nonwoven production the card web is doubled by means of a cross lapper and transformed into a nonwoven using a needle-punching machine. To produce high-oriented hybrid yarn, the card web is transformed into a sliver. This is stretched and fed into a hollow spindle spinning machine where a matrix filament yarn is wrapped around the yarn core, drawing and compacting the sliver into a staple fiber yarn. The yarn can be used in composite materials, with tests showing good results in a PA6 matrix with a fiber volume content of up to 50 percent.
Natural Fiber Composites (NFC) are also receiving some attention for applications in wind turbines as a bio-based alternative to glass fiber and carbon fiber in large composites. The Green Nacelle is being developed by Danish sustainable composites company Greenboats, Swiss composites company Bcomp, and French composites manufacturer Sicomin. The nacelle (the cover over the generating components in a wind turbine) uses ampliTex flax reinforcement fabrics from Bcomp with FSC-certified balsa wood cores and biobased Infugreen 810 GreenPoxy resin from Sicomin.
Flax has a lower environmental impact than virgin glass fiber, and the technology is scalable with viable end-of-life processes in place. It is estimated that Green Nacelle’s NFC construction saves approximately 60 percent CO2equivalent and reduces the energy consumption by over 50 percent compared to a nacelle made with existing GFRP technology.
Given the interest in, and availability of, new processes for recycling composite components, it is clear that the textile industry is positioned to be an important part of a longer term solution in wind energy.
Dr. Marie O’Mahony is an industry consultant, author and academic. She the author of several books on advanced and smart textiles published by Thames and Hudson and Visiting Professor at the Royal College of Art (RCA), London.