Artificial Dust Devils
The word ‘tornado’ is usually associated with death and destruction, but mechanical engineers Mark Simpson and Ari Glezer at the Georgia Institute of Technology have figured out a way to harness them for renewable energy. They’re not out braving huge natural tornadoes, but rather they’re artificially creating small, controlled vortexes and using them to produce cheap, renewable energy. After seeing dust devils in Arizona sparked the idea, Glezer and Simpson built a metre-wide prototype that looks a bit like the inside of an aircraft engine rotor. Called the Solar Vortex, it relies on the temperature difference between hot air near the ground and cooler air just a metre above it. When the hot air rises and the cool air descends, convection currents form between the layers (convection currents are basically the continual cycle of heat transfer up and down). Well-positioned vanes force the airflow to spontaneously form into a vortex, which sucks in more warm air to maintain itself and turns a turbine at the centre of the device, generating energy—and no power is needed to kick-start it. The Department of Energy’s Advanced Research Projects Agency have agreed to fund large-scale trials, and they hope to build a 10 kilowatt model within two years and a 50 kilowatt model in the future. Glezer estimates that a square kilometre array of the turbines would produce 16 megawatts of energy—much more than the 3 to 5 megawatts of conventional wind turbines. It would be 20% cheaper than traditional wind power generation and 65% cheaper than solar panels, and the Solar Vortex doesn’t even need to be elevated to catch the wind, so it could be installed on building and factory rooftops where sufficient waste heat escapes.