Researchers at the US Department of Energy’s National Renewable Energy Laboratory (NREL) have found a practical path for manufacturing bio-derivable wind turbine blades that can be recycled and reused, potentially ending the practice of landfilling old blades.
The paper “Manufacture and testing of biomass-derivable thermosets for wind blade recycling” involved work from investigators at five NREL research hubs, including the National Wind Technology Center and the Bio-Optimized Technologies to keep Thermoplastics out of Landfills and the Environment (BOTTLE) consortium.
The researchers built a 9-metre blade prototype to demonstrate the manufacturability of an NREL-developed biomass-derivable resin nicknamed PECAN. The acronym stands for PolyEster Covalently Adaptable Network, and the manufacturing process fits together with current methods, according to NREL.
The new resin, which is made of materials produced using bio-derivable resources, is said to perform on par with the current industry standard for blades made from thermoset resin and outperforms certain thermoplastic resins intended to be recyclable.
Under existing technology, wind turbine blades last about 20 years, and afterward, they can be mechanically recycled, such as shredded, for use as a concrete filler. PECAN represents an advancement due to its ability to recycle blades using mild chemical processes, said NREL.
The chemical recycling process allows the components of the blades to be recaptured and reused again and again, allowing the remanufacture of the same product, according to Ryan Clarke, a postdoctoral researcher at NREL. He said the chemical process was able to completely break down the prototype blade in six hours.
The research into the PECAN resin began with the end. The scientists wanted to make a wind blade that could be recyclable and began experimenting with what feedstock they could use to achieve that goal. The resin they developed using bio-derivable sugars provided a counterpoint to the conventional notion that a blade designed to be recyclable will not perform as well.
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Nic Rorrer, one of the two corresponding authors of the paper, said one concern others have had about these types of materials is that the blade would be subject to greater “creep”, which is when the blade loses its shape and deforms over time.
Composites made from the PECAN resin held their shape, withstood accelerated weatherization validation, and could be made within a timeframe similar to the existing cure cycle for how wind turbine blades are currently manufactured, according to NREL.
While wind blades can be as long as a football field, the prototype demonstrated the effectiveness of the recycling process, NREL added.
“Nine meters is a scale that we were able to demonstrate all of the same manufacturing processes that would be used at the 60-, 80-, 100-meter blade scale”, said Robynne Murray , the second corresponding author.
The US Department of Energy (DOE) jointly funded the research through its Advanced Materials and Manufacturing Technologies Office and Bioenergy Technology Office, and their support of the BOTTLE consortium.