Small, vertical axis wind turbines

This new vertical axis wind turbine might change the way you look at wind energy. For many years there has been a trend across the wind industry to make wind turbines bigger and bigger – mostly to improve efficiency and lower costs.

John Dabiri, a professor of aeronautical and bioengineering at Caltech, has a different idea. He believes the way to lower the wind energy costs is to use small, vertical axis wind turbines, and optimize their arrangement in a wind farm using computer models. When correctly arranged, each turbine boosts the power output of its neighbors. Dabiri has demonstrated the basic idea at a 24-turbine test site in southern California, and received $6 million in grants from the Gordon and Betty Moore Foundation and the U.S. Department of Defense to further his research.

The first 10 turbines will be installed this year, and the long-term goal is to install 50 – 70 turbines.

Dabiri is also installing turbines in between existing turbines at an existing wind farm in Palm Springs, California. Ordinarily, the wind that passes around and through a wind turbine produces turbulence that reduces the power output of downstream turbines and increasing wear and tear. Dabiri says that properly positioned vertical-axis turbines produce a wake that can be beneficial to other turbines.

Conventional turbines have blades horizontally, arranged like spokes on a wheel.  These new wind turbines have vertical blades. As wind moves around the vertical-axis turbines, it speeds up. The vertical blades on the downstream wind turbines allows them to effectively catch that wind and generate more power.

The new design also makes it possible to save space and position more turbines closer together.

Unlike the typical 100-meter-tall, multi-megawatt turbines, Dabiri’s wind turbines are 10 meters tall and generate three to five kilowatts. Dabiri says smaller turbines make for easier manufacturing and if produced on a large scale could cost less than conventional turbines . He also says maintenance costs could decrease because of the ease of accessing the short turbines.

There are other advantages as well. Wind turbine noise has sometimes been an issue to local communities, but the new turbine design he says is almost inaudible. The vertical axis turbines are also less likely to kill birds. The Department of Defense has taken interest in their short profile and granted a $1 million grant to study their use on military bases. The short profile interferes less with helicopter operations and radar than conventional, horizontal blade wind turbines.

There are also challenges: vertical axis wind turbines aren’t as efficient as conventional turbines, because during 50% of their operation the blades are actually moving against the wind. As the blades alternatively catch the wind and then move against it, they create wear and tear on the structure, says Fort Felker, director of the National Wind Technology Center at the National Renewable Energy Laboratory. Dabiri and other researchers say they are working on improved turbine designs to address some of these issues.

In the future, vertical axis wind turbines just might be more popular than the very large ones that dot the landscape now.