Maximizing Wind Turbine Efficiency

A new design for small wind turbines leads to greater efficiency and a big increase in energy production. It also promises to revolutionize the residential market for wind energy.

A radically different-looking wind turbine is in the works at Clarkson that can produce twice the energy of a similarly sized conventional turbine.

Professor Ken Visser, along with his graduate students Ben Kanya, Nojan Sadeghi and others, built and tested a ducted turbine with a rotor diameter of 2.5 meters, an ideal size for producing energy for household use.

The concept of a ducted turbine itself isn’t new. Designs for a duct that would wrap around a turbine’s rotor to increase the rotor’s performance go back about 100 years.

If you took a slice from our duct, it would look like the airfoil of an airplane wing.

But Visser’s innovative design includes two patented technologies: a novel blade design and the unique placement of the turbine rotor in the duct itself. Operating in an area with an average wind speed of 5 meters per second, this turbine would produce up to half of the electricity used annually by a typical U.S. home.

The associate professor of aeronautical and mechanical engineering recently tested the uniquely designed turbine for the first time at the University of Waterloo Wind Turbine Test Tunnel. “The numbers we are seeing,” he says, “could revolutionize the market.”

Professor Ken Visser in front of a wind turbine

To get these results, Visser altered the way his turbine takes in wind.

Picture a giant tube. This tube is a stream of air. Most small turbines can pull around 30 percent of the energy from this stream. Visser’s turbine is able to “grab” more air from a bigger wind stream tube, the equivalent of more than 80 percent of that original stream’s energy.

Ducted turbines, like Visser’s, also change the shape of the captured air stream as it moves, from a tubular shape to an hourglass shape. The increased air flow moves faster at the narrower point, contributing to the increased power output.

Visser’s experience designing large commercial aircraft led him to conceive a more complex kind of duct. “If you took a slice from our duct, it would look like the airfoil of an airplane wing.” And, while ducted turbine designs have usually placed the rotor at the narrowest part of the air stream, Visser’s blades are located downstream, just past the pinched part of the hourglass.

Perhaps most importantly, the turbine promises to significantly reduce the cost per unit of energy generated.

Visser’s turbine is already generating interest. He recently partnered with an energy professional to launch Ducted Turbines International to commercialize this technology.

“There is more work to be done and many engineering decisions still to be made,” he says, “but I’d love to see people using this turbine design. It simply harnesses more energy. It will be a game-changer.”

Learn more at ductedturbinesinternational.com.

Wind App screen shot

WindApp is a mobile wind energy application developed by Prof. Visser that is available through Energy Research Applications, a company he started with the help of the Shipley Center for Innovation.

“Most people don’t know what's involved in choosing a wind turbine, how much energy is generated or what the power rating means,” says Visser. “WindApp offers an easy, practical way for the public to determine which wind option is best for them.”

The app figures out the user’s location, the local wind speed and how much energy could be generated when a particular turbine is selected. It then computes how long it will take to pay back the turbine choice, based on the buyer’s local electric rates.

Through the Shipley Center, Visser connected with Jack of Trade Apps, an incubator company founded by alumnus Andrew Davis '98.

Jack of Trade Apps developed a mobile version of WindApp that runs on both Apple and Android phones and tablets. They also created a content management system for WindApp so that as new turbines and wind turbine installers come on board, the app will automatically update the data on the user’s device.

Learn more or download the app: energyresearchapplications.com/wind-app

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