A new analysis by the California Institute of Technology (Caltech) finds that the power output of wind farms can be increased tenfold — and with fewer environmental impacts — through better positioning of vertical-axis turbines. Because the large turbines used in most modern wind farms are placed far apart to prevent aerodynamic interference, much of the potential wind energy that enters the farms is wasted, according to the paper, published in the Journal of Renewable and Sustainable Energy. And the common steps taken to compensate for that problem, including construction of bigger blades or taller towers, generate higher costs and greater environmental impacts. Using a test array of vertical-axis wind turbines on a Southern California field, the Caltech researchers showed that more strategic placement of turbines closer to the ground maximizes energy production. The vertical-axis turbines can be placed closer together without causing aerodynamic interference, and researchers found that having each turbine spin in the opposite direction of its closest neighbor increased efficiency, perhaps because the opposing spins decreased the drag on each turbine, allowing them to spin faster.