Vertical-Axis Wind Turbines a Sign of the Future? (November 25, 2005)

Various designs of vertical-axis wind turbines (VAWT) have been mooted for several years as possible competitors for the ubiquitous horizontal-axis wind turbines (HAWT) seen with increasing frequency on all continents. So far none has gained favour.

This may be about to change through the research of two fluid dynamicists from the California Institute of Technology (Caltech), Robert Whittlesey and John Dabiri who reported yesterday at the annual meeting of the American Physical Society in Minneapolis, Minnesota on their comparative studies of grouped VAWTs and HAWTs.

Their analyses are still preliminary but nevertheless they are remarkable. They found that tightly packed VAWT arrays can produce as much electricity as conventional HAWTs, but occupy as little as 1% of the land area. "I don't think I expected to see as great an improvement in the land use," says Mr Whittlesey who is currently a second year graduate student at Caltech in aeronautics and a member of Prof. John Dabiri's group.

So far an arrangement of alternating the rotational direction of the turbines: a clockwise rotation in the lead turbine, say, with two counter-clockwise rotators next in line, followed by three clockwise rotators, and so on appears to be the most efficient but further analyses are underway to determine maximum efficiency.

Mr Whittlesey also noted that "the faster the rotors spin, the more solid they appear," thereby allowing birds to see the turbines more easily and navigate around them".