The power output of wind farms can be increased at least tenfold by optimizing the placement of turbines on a given plot of land, say researchers at the California Institute of Technology (Caltech), who have been conducting a field study at an experimental two-acre wind farm in northern Los Angeles County.
A paper describing the findings – the results of field tests conducted by John Dabiri, Caltech professor of aeronautics and bioengineering, and colleagues during summer 2010 – appears in the July issue of the Journal of Renewable and Sustainable Energy.
Dabiri's experimental farm, known as the Field Laboratory for Optimized Wind Energy, houses 24 10-meter-tall, 1.2-meter-wide vertical-axis wind turbines.
In modern wind farms that utilize horizontal-axis wind turbines, the individual turbines have to be spaced far apart. With this type of design, the wake generated by one turbine can interfere aerodynamically with neighboring turbines, with the result being that ‘much of the wind energy that enters a wind farm is never tapped,’ says Dabiri.
Designers compensate for the energy loss by making bigger blades and taller towers to suck up more of the available wind at heights where gusts are more powerful.
The solution, says Dabiri, is to focus instead on the design of the wind farm itself and works to maximize its energy-collecting efficiency at heights closer to the ground. Enough energy can be obtained with smaller wind turbines as long as they are arranged in the right way, he adds.