Mark Simpson and Ari Glezer at Georgia Institute of Technology in Atlanta have developed a new way of driving a wind turbine using the vortex effect which produces whirlwinds and tornados.

When there is a temperature difference between hot air close to the ground and cooler air just above it, the hot air rises and cool air falls. This causes convection currents to form between these layers, leading to small whirlwinds.

The researchers channelled these currents with an array of fixed blades into a vortex, which turns a turbine at the device's centre. As the warm air rises, more air rushes in, fuelling the artificial whirlwind.

Maintenance and installation costs are much lower than for a conventional wind turbine because there is no need to put turbines on high towers. Since ground temperature varies slowly through the day, the system's energy output is more constant than with conventional wind turbines and continues for a few hours after sunset.

To date, only a small 1-metre diameter version of the system has been tested but the researchers calculate that a 10-metre version will produce 50 kilowatts and that a square kilometre array would produce 16 megawatts. Conventional wind turbines produce between 3 and 6 megawatts per square kilometre.

The U.S. Advanced Research Projects Agency Energy is funding a large-scale trial of the technology.