Cyclones carry enormous energy; even tornado of smaller or average size has power similar to that of a large power station. Louis Michaud has sought to harness this energy by creating man-made tornadoes that can be controlled and used to obtain energy. He calls his design the "atmospheric vortex engine [AVE]". 
Michaud's prototype uses warm air (e.g., the excess warm air released from the cooling system of a nuclear plant) to generate tornadoes. These tornadoes can stretch up to 9 miles high; the AVE uses these tornadoes to spin turbines and as a result, generate electricity. 
In a tornado, the draft at the base is proportional to the temperature difference between the warm air rising inside the storm and the outside cooler air and the height of the tornado. In a tornado, the rotating air is forced inward and prevents cooler outside air from entering the tornado because the centrifugal force of the air pushes the ambient air back outward. 
The tornado is created by filling a cylindrical tower with spinning warm air. A circular roof with a central circular opening forces the air to converge, and as the air escapes, a tornado forms. The pressure difference between the outside air and the air at the bottom of the tornado draws in air through ducts. This air in turn spins turbines through which energy can be collected. 
The AVE has been tested extensively, but only in smaller-scale models, the largest around 12 feet in diameter. Four 20kW heaters were used to create the warm air used to create the tornadoes. The resulting tornadoes were 1-2 feet wide and about 60 feet high. 
A full-scale prototype would logically have to be built at an existing thermal power plant; the power plant would function as a controllable heat source of fairly high temperature. The prototype would be able to take the typically wasted heat from the plant, and thus fully display the advantages of the AVE.
Theoretically, a fully functioning prototype (as envisioned by Michaud) could provide a cooling system to the thermal power plant it was attached to, create a use for the wasted heated air, and produce power on its own.
Michaud admits that concepts centered on weather control are more often than not "shunned by the scientific community and feared by the public".  Questions conjure up images of out-of-control man-made tornadoes ripping through cities destroying anything in their paths.
However, unlike the natural disasters we are accustomed to, the air in the AVE are regulated by adjustable restrictors. As a result, the tornado is theoretically always in control and can be turned on or off as needed.
A bigger, more relevant question is whether or not the energy needed to start the tornado is financially and energetically less than the energy harvested from the vortex. It is, in fact, funding that is the current obstacle for Michaud's progress. He is still "shopping his prototype around" to energy companies, hoping to obtain the go-ahead to build a prototype the size of a sports arena. 
While it is highly unlikely that the world will immediately turn to the AVE for energy, Michaud's vortex engine is receiving some attention and has drawn some funding and research from the University of Western Ontario through the Ontario Centers of Excellence. Researchers at the university are studying a one-meter version of the AVE, as well as running computer simulations of larger models. 
"Michaud figures that such a tornado could generate as much power as a nuclear plant" - and if his engine does precisely what Michaud predicts, the AVE is definitely an intriguing idea.  In theory, the engine creates a system that capitalizes on wasted heat from existing thermal power plants, is fully controllable, and potentially has the power to generate electricity using no fuel at all. 
While the AVE is an interesting concept, it is a project that is far from completion. A full-scale model has still yet to be built. Michaud has commented that "'People say ... it's too scary - how are you going to control it ... . But once you demonstrate you can operate it safely in a remote location, then you might be willing to have one located in a city.'"  There are still many steps to be taken before the general public views the engine as a valid source of energy.
© Brenda Ou. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
 "The Power of Spin," The Economist, 29 Sep 05.
 O. Kharif, "Energy from Unusual Sources," Bloomberg BusinessWeek, 10 Sep 07.
 L. Michaud and N. Renno, "The Sky's the Limit," Mechanial Engineering Magazine, April 2011.
 T. Hamilton, "Taming Tornadoes to Power Cities," The Toronto Star, 21 Jul 07.