Sounds great — but will it scale up? That’s been the downfall of many projects that work small scale, like biofuels from algae & cellulosic, etc. And as I say at the top of many of these posts, this is an oil crisis, that’s what 97% of our transportation system runs on. Plus our electric grid is aging and falling apart, not being geared up for handling more electricity, which doesn’t solve our problems, and the grid and this whirlwind device depend on oil throughout their life cycle from mining, construction, transport, and maintenance.
11 March 2013. Hal Hodson. Reap the whirlwind for cheap renewable power. NewScientist
The Solar Vortex system (see diagram) is the brainchild of Mark Simpson and Ari Glezer at Georgia Institute of Technology in Atlanta. It relies on the temperature difference between hot air close to the ground and cooler air just a meter or so above it. As the hot air rises and cool air falls, convection currents form between these layers, leading to small whirlwinds or dust devils.
Solar Vortex channels these currents with an array of fixed blades or vanes. They funnel the airflow into a vortex, which turns a turbine at the device’s center. No power is needed to kick the process off as the position of the vanes helps the vortex to start spontaneously. As the warm air rises, more air rushes in, fueling the artificial whirlwind.
Maintenance and installation costs are much lower than for a conventional wind farm because there is no need to put turbines on high towers to catch the wind. Since ground temperature varies slowly through the day, the system’s energy output is more constant too, and stays steady for a few hours after sunset, when consumer demand is often highest.
Glezer had the idea after living in Arizona. “He had experienced naturally occurring dust devils and the kinetic energy they contain, and wanted to create a method for extracting that power,” Simpson says.
Simpson has tested a small, 1-meter version of the vortex that drives a turbine to create a few watts of power using nothing more than a hot, sun-baked metal sheet. However, the power output scales up rapidly as you increase the turbine’s diameter. Simpson calculates that a 10-meter turbine will produce 50 kilowatts of power using the same method. The team says that an array of these vortex turbines could produce 16 megawatts for every square kilometer they cover. This is not bad considering conventional wind turbines yield just 3 and 6 megawatts per square kilometer. In fact, the team estimates that the electricity produced by a Solar Vortex will be 20% cheaper than energy from wind turbines and 65% cheaper than solar power.
The US government’s clean energy start-up shop is convinced: the Advanced Research Projects Agency Energy (ARPA-E) announced its decision to fund some large-scale trials last week. Simpson is due to present a paper in July detailing the trials at the ASME International Conference on Energy Sustainability in Minneapolis, Minnesota. Working with ARPA-E, Simpson and Glezer plan to have a 10 kW model running within two years, with tests on intermediate models scheduled for July. They want to build a 50kW model in the future.
“The science is solid,” says Nilton Renno, who researches thermodynamics at the University of Michigan. “Once you induce circulation nearby, the vortex can be self-sustaining.”
Steven Chu, the outgoing energy secretary, is interested; he visited the team briefly at the ARPA-E conference in Washington DC last week. “We would like to start with building a small-scale farm of these things,” Simpson says. “At that point we start to produce real