A wind tunnel on the Homewood campus allows researchers to experiment with variables such as the correct spacing of wind turbines. Charles Meneveau and a colleague have devised a new formula for determining the optimal positioning. (Will Kirk, JHU)
Large wind farms are being built around the world, but operators are still searching for the most cost-effective and efficient way to arrange the massive turbines. To help steer wind farm owners in the right direction, Johns Hopkins University researchers devised a new formula through which the optimal spacing for a large array of turbines can be obtained.

The newest wind farms, which can be located on land or offshore, typically use turbines with rotor diameters of about 300 feet. Currently, turbines on these large wind farms are typically spaced about seven rotor diameters apart. The new spacing model developed by Charles Meneveau, a Johns Hopkins fluid mechanics and turbulence expert, and Johan Meyers, an assistant professor at Katholieke Universiteit Leuven in Belgium, suggests that placing the wind turbines 15 rotor diameters apart - more than twice as far apart as in the current layouts - results in more cost-efficient power generation.

Meneveau and Meyers argue that the energy generated in a large wind farm has less to do with horizontal winds and is more dependent on the strong winds that the turbulence created by the tall turbines pulls down from higher up in the atmosphere. Using insights gleaned from high-performance computer simulations as well as from wind tunnel experiments, they determined that in the correct spacing, the turbines alter the landscape in a way that creates turbulence, which stirs the air and helps draw more powerful kinetic energy from higher altitudes.

In the video below, the researchers conduct previous experiments in the campus wind tunnel.