New wind turbines said more efficient

PASADENA, Calif., July 13 (UPI) -- The power output of wind farms can be increased at least ten-fold simply by optimizing the placement of turbines on a given plot of land, U.S. researchers say.

Researchers at the California Institute of Technology have been conducting a field study at an experimental 2-acre wind farm in northern Los Angeles County.

Despite improvements in the design of wind turbines, wind farms are rather inefficient, researcher John Dabiri said.

Modern farms generally employ horizontal-axis wind turbines, the standard propeller-like giants that have to be spaced far apart, and not just far enough that their giant blades don't touch.

With this type of design, the wake generated by one turbine can interfere aerodynamically with neighboring turbines, with the result that "much of the wind energy that enters a wind farm is never tapped," Dabiri said.

At their experimental facility, Caltech researchers are using vertical-axis wind turbines that have vertical rotors and look like eggbeaters sticking out of the ground.

Such wind turbines are ideal, Dabiri said, because they can be positioned very close to one another.

Tests showed that an arrangement in which all of the turbines in an array were spaced four turbine diameters apart -- about 16 feet -- completely eliminated the aerodynamic interference between neighboring turbines.

By comparison, propeller-style wind turbines would require spacing them about 20 diameters apart, a distance of more than a mile between the largest wind turbines now in use.

The vertical turbines at the Caltech experimental farm generate 21 to 47 watts of power per square meter of land area, whereas a comparably sized horizontal turbine farm generates just 2 to 3 watts per square meter, the researchers said.