Harvesting tornadoes as power plants; renewable wind vortex energy
Rhett A. Butler, mongabay.com
October 9, 2005
Engineers are working to use artificial tornadoes as a renewable energy source according to an article in last week's issue of The Economist.
Storms release a tremendous amount of energy. Hurricane Katrina, a category 4 hurricane, released enough energy to supply the world's power needs for a year, while the typical tornado produces as much power as a large power station.
As described in The Economist, his system "works on a similar principle to a solar chimney, which consists of a tall, hollow cylinder surrounded by a large greenhouse. The sun heats the air in the greenhouse, and the hot air rises. But its only escape route is via the chimney. A turbine at the base of the chimney generates electricity as the air rushes by... His scheme replaces the chimney with a tornado-like vortex of spinning air, which could extend several kilometres into the atmosphere."
Michaud's "vortex would be produced inside a large cylindrical wall, 200 metres in diameter and 100 metres tall. Warm air at ground level enters via tangential inlets around the base of the wall. Steam is also injected to get the vortex started. Once established, the heat content of the air at ground level is enough to keep the vortex going. As the air rises, it expands and cools, and water vapour condenses, releasing even more heat," much like how a hurricane frees energy by drawing warm humid air from its base (usually tropical sea water) and then releasing cold, wet air 7 miles (12 kilometers) up in the troposphere.
"The intensity of the vortex would be controlled by closing the inlets around the base, or by opening another set of inlets to inject air in the opposite direction and so slow the vortex's rotation. And, of course, there would be a set of turbines at the base of the vortex that would allow its energy to be harnessed as air rushed through the inlets. Mr Michaud estimates that an atmospheric vortex engine with a diameter of 200 metres would produce around 200 megawatts of power."
History of solar chimney designs
A solar chimney is a device for harnessing solar energy by the convection of heated air. First officially described in 1931 by a German author, Hanns Günther, the first functional model solar chimney power station was built in 1982 in Manzaranes, Spain. Funded by the German Government, the power plant operated for eight years. The chimney had a diameter of 10 metres and a height of 195 metres, with a collection area (greenhouse) of 46,000 m² (about 11 acres) obtaining a maximum power output of about 50 kW.
EnviroMission says a single 200MW Solar Tower power station will provide enough electricity to power around 200,000 households, but at a savings of more than 900,000 tons of carbon dioxide, an important greenhouse gas. Such a wind-based power scheme could play an important part in supplying energy in a future where carbon-based fossils fuels are expensive and heavily regulated due to their impact on the environment and global climate.
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The article used quotes and information from The Economist: "Alternative energy -- The power of spin," Sep 29th 2005.