DOE To Explore Offshore Heights With Onshore Construction Techniques

The U.S. Department of Energy (DOE) is investing $2 million to explore ways to build taller wind turbines that can access stronger and more consistent high-altitude winds.

What’s known as the Taller Hub Heights opportunity for federal funding will help wind farms in Iowa and Massachusetts get access to the stronger winds and, using longer rotor blades, reap more wind energy than they can today.

The two projects will help reduce the cost of harnessing wind energy and expand the number of regions where turbines can be successfully situated at relatively low cost, David Danielson, the assistant U.S. secretary for energy efficiency and renewable energy, said Sept. 18 in announcing the funding.

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Currently, the height of wind towers is limited by the constraints of logistics and transportation in moving the turbines’ components to their installation sites. As a result, onshore turbines installed in 2013 averaged 260 feet in height.

But the newer turbines to be installed for the grant recipients, Iowa State University and Keystone Towers of Massachusetts, will reach heights of nearly 400 feet. That’s the “hub height” of the turbine, measured from the ground to point at which the rotor blades are attached. If the blades describe a circle 100 meters (328 feet) in diameter, the tip of each rotor will reach 558 feet above ground.

The taller the turbines and the bigger the rotors, the more wind they can catch – as much as 7.5 megawatts or even up to 10 megawatts, far outpacing U.S. onshore turbines built in 2013, which  capture less than 2 megawatts at best.

These taller turbines already have been used in offshore wind farms and can capture between seven and 10 megawatts of wind energy. But their construction, while suitable for offshore applications, doesn’t translate to onshore construction. Besides, building towers strong enough to support heavy turbines can be expensive.

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But the two projects being funded by the DOE are exploring novel ways to make construction and shipping more efficient and less expensive. Massachusetts’ Keystone Towers, for example, is considering applying a spiral welding technique that could lead to on-site construction of tubular steel towers that are 40 percent lighter than the current design. That would save on shipping and materials cost.

Meanwhile, Iowa State is focusing on a modular design made of hexagonal concrete and steel that would allow the taller towers to be shipped in pieces and assembled on-site.

“Through innovative construction processes that will cost-effectively manufacture taller wind turbine towers, these projects in Iowa and Massachusetts will help reduce the cost of wind energy and expand the geographic areas where wind turbines can successfully be deployed in the U.S.,” the DOE said in a news statement.

By Andy Tully of Oilprice.com

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