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Positioning of VAWTs profoundly affects their generating efficiency

18 June 2013

A Caltech group is studying the environmental benefits and augmented efficiencies of closely grouped vertical axis wind turbines (VAWTs).

Photo courtesy of John Dabiri
Photo courtesy of John Dabiri

Back in 2009, John Dabiri, a professor of aeronautics and bioengineering at the California Institute of Technology (Caltech), was intrigued by the pattern of spinning vortices that trail fish as they swim. Curious, he assigned some graduate students to find out what would happen to a wind farm's power output if its turbines were spaced like those fish vortices.

In simulations, energy production jumped by a factor of ten. To prove that the same effect would occur under real-world conditions, Dabiri and his students established a field site in the California desert with 24 turbines. Data gathered from the site proved that placing turbines in a particular orientation in relation to one another profoundly improves their energy-generating efficiency.

The turbines Dabiri has been investigating are vertical-axis wind turbines (VAWTs) which have the potential to dramatically decrease the cost, footprint, and environmental impact of wind farms.

"We have been able to demonstrate that using wind turbines that are 30 feet tall, as opposed to 300 feet tall, could generate sufficient power for wind-farm applications," Dabiri says.

"That's important for us because our approach to getting to lower-cost energy is through the use of smaller vertical-axis wind turbines that are simpler—for example, they have no gearbox and don't need to be pointed in the direction of the oncoming wind—and whose performance can be optimised by arranging them properly."

Dabiri and his group are now beginning several pilot projects to test their concept.

One of the major benefits of VAWTs is that they can be placed much closer to one another; many more of them can fit within a given area, allowing them to tap into more of the wind energy available in that space than is typically possible. What this all means is that a very productive wind farm can be built that has a lower environmental impact than previously possible.

The team is also testing a few different VAWT designs. Among them is a new polymer rotor, designed by Caltech spin-offs, Materia and Scalable Wind Solutions, which may withstand icing better than standard aluminium rotors.

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