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August 30, 2011

World's first polyurethane blade reinforced with carbon nanotubes is lighter and stronger and eight times tougher

Blades installed in a 400W wind turbine generator.

A post-doctoral researcher at Case Western Reserve University has spearheaded an effort to build the world’s first polyurethane wind turbine blade reinforced with carbon nanotubes. Advanced materials with higher strength to mass ratios could enable larger area rotors to be cost-effective. Carbon nanotube based composites could enable larger rotor blades.

“The idea behind all this is the need to develop stronger and lighter materials which will enable manufacturing of blades for larger rotors,” Loos said in a news release. Loos built the blade on weekends.

Lighter blades help to maximize energy output from wind turbines. In a comparison of reinforcing materials, the researchers found carbon nanotubes are lighter per unit of volume than carbon fiber and aluminum and had more than 5 times the tensile strength of carbon fiber and more than 60 times that of aluminum.

Fatigue testing showed the reinforced PU lasts about eight times longer than epoxy-reinforced fiberglass. The new material was also about eight times tougher in delamination fracture tests. Performance was even better compared to vinyl ester-reinforced fiberglass.

Eurekalert - Using a small commercial blade as a template, he manufactured a 29-inch blade that is substantially lighter, more rigid and tougher. The functional prototype blades built by Loos were used to turn a 400-watt turbine.



The new composite also has shown fracture growth rates at a fraction of the rates found for traditional epoxy and vinyl ester composites.

Loos and the rest of the team are continuing to test for the optimal conditions for the stable dispersion of nanotubes, the best distribution within the polyurethane and methods to make that happen.



Radical redesign of the wind turbine by Nimrod Energy in the UK could do more

The industry has converged on a consensus that large wind turbines should be three-bladed, horizontal-axis machines on top of a tubular tower. This is good up to 150 meters in diameter.

Prof Garvey turbine is dramatically different: a horizontal-axis machine with eight blades — four long and four short. A floating framework replaces the tower, and it converts wind power internally within the blades. Think of a bicycle wheel rotating slowly, and a loose bead on each spoke. The beads represent pistons travelling back and forth inside tubes in the blades, compressing air as they do so.

The baby of the family is a 200 meter-diameter machine producing 18MW in a decent wind and costing less than 40% of the 40 million pounds you’d spend on a corresponding set of direct-generating machines. Her big sisters might easily reach 400 meter in diameter and could be 50% more cost-effective.




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