Researchers from the California Institute of Technology found out that how turbines are placed in a wind farm can increase their efficiency and power output
Most conventional wind farms use horizontal-axis wind turbines which, to make room for their blades, need to be spaced far apart. But such a design, the "wake" generated by one turbine can interfere aerodynamically with neighboring turbines.
The researchers believe that vertical-axis wind turbines or V.A.W.T.'s can overcome this problem because they can be placed closer together than H.A.W.T.'s.
As a result, the close placements allow them to capture nearly all the energy of the blowing wind in the wind farms.
John Dabiri, Caltech professor of aeronautics and bioengineering, and his colleagues tested their theories during the summer of 2010 by measuring the rotational speed and power generated by the turbines when placed in a number of different configurations.
The researchers worked on an experimental wind farm in Los Angeles county. The experimental two-acre wind farm was composed of 24 10-meter-tall, 1.2-meter-wide vertical-axis wind turbines.
The tests showed that an arrangement in which all of the turbines in an array were spaced four turbine diameters apart, or approximately 5 meters, completely eliminated the aerodynamic interference between neighboring turbines.
By comparison, removing the aerodynamic interference between horizontal-axis wind turbines would require spacing them about 20 diameters apart, which means a distance of more than one mile between the largest wind turbines now in use.
Under this configuration, the six V.A.W.T.'s in the field test generated from 21 to 47 watts of power per square meter of land, compared with a similarly sized H.A.W.T. farm which would only generate around 2 to 3 watts per square meter.
A paper describing the full findings of the field tests appears in the July issue of the Journal of Renewable and Sustainable Energy. (K.D. Mariano)
source: apec-vc korea