Reap the Whirwind
by Hal Hodson / 07 March 2013
Whirlwinds are associated with destruction, not sustainable energy. Now it seems we can harness their power to generate renewable electricity. The Solar Vortex system 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 metre 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 centre. 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, fuelling 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-metre 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-metre 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 kilometre they cover. This is not bad considering conventional wind turbines yield just 3 and 6 megawatts per square kilometre. In fact, the team estimates that the electricity produced by a Solar Vortex will be 20 per cent cheaper than energy from wind turbines and 65 per cent 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 their 50 kW model running within two years, with tests on intermediate models scheduled for July. “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 energy, and can begin to sell some of that energy and convince people of our system.”
Dust Devils Power Energy Machine
by Eric Niiler / Feb 28, 2013
Dust devils are swirling micro-tornadoes that pop up regularly in dry, warm climates or during the summertime. Researchers say they have figured out how to tame the tiny twisters and extract their energy using a rotating turbine blade. A team at Georgia Tech has built a small demonstration prototype about three feet wide. It looks like the inside of an aircraft engine rotor turned on its side. Warm air flows in through a series of vanes that force the buoyant ground-heated air to rotate as it rises. This spinning creates a powerful vortex, or “dust devil,” according to Ari Glezer, the principal investigator and professor of mechanical engineering at Georgia Tech. As the column of air rises, it draws in more hot air to keep going. Here’s a video of a laboratory-created dust devil. And the real thing at a baseball field in Indiana. “We trigger a vortex artificially,” Glezer said. “The idea is to ultimately hook it up to the electric grid.”
Glezer’s project recently was awarded $3.7 million from the Department of Energy’s Advanced Research Projects Agency — Energy (ARPA-E). The Solar Vortex fits with the goals of ARPA-E to find high-risk, high-reward projects, according to program director Bryan Willson. “It’s part of our mission to look for disruptive energy technologies that are typically earlier stage and higher risk than other agencies or commercial entities would take on,” Willson said. “They also have to be based on sound science.” Glezer said if the Solar Vortex is successful, it would cost 25 percent less than traditional wind power generation and 60 percent less than solar panels. That’s because the vortex is generated with or without prevailing winds higher up in the atmosphere. The other nice thing is the turbines are low to the ground and don’t block neighbors views, something that has stymied wind projects in several parts of the country. Glezer says he envisions an one-kilometer square array of turbines that are six feet tall and 30 feet wide. He believes they could especially be helpful during the summertime, when demand for electricity spikes. He also sees them sitting atop rooftops on office buildings and factories where there is plenty of waste heat escaping to the air. Nobody has harnessed dust devils before, and Willson said some of his fellow DOE managers needed some convincing before the agency agreed to spend taxpayers’ money on it. “It’s definitely an unconventional technology,” Willson said. “Which means we put it through a lot of internal debate at ARPA-E to make sure it was a rational technology, as well as just being cool and innovative.”
by David Ferris / 2/26/2013
Now in its fourth year, the summit of the Advanced Research Projects Agency-Energy (ARPA-E) never fails to bring out the most cutting-edge ideas in renewable energy. This week’s conference inWashington D.C. is no exception. I walked the exhibition floor today and ran across some sexy new concepts in solar power. The Solar Vortex borrows its inspiration from dust devils, those miniature twisters of excited dirt that sometimes arise in the dusty and dry stretches of the U.S. Southwest. What gets a dust devil going is the difference in temperature between the scorching-hot ground and the somewhat cooler air above. The hot air rises, twists and gives rise to a momentary dust tornado. Georgia Tech is the leader of a consortium that aims to capture this dust-devil energy inside a stubby cylinder. The concept is simple: The cylinder sits upon a dark surface that absorbs lots of heat. The “walls,” so to speak, are angled vanes that take the hot air rising off that hot surface and twist it into a vortex. At the top, a set of fan blades sit in the path of the rising air. The fan blades turn, activating a generator that creates electricity. The video below is a miniature model of the Solar Vortex on the exhibition floor. The cylinder sits on a plate that is, like hot pavement, almost too hot to touch, about 47 degrees Celsius (116 degrees Fahrenheit). The movement you see in the blade is solely from the force of moving air.
Georgia Tech has already gotten rights to use a site in Mesa, Arizona — plenty of heat there — and is working toward building a 50-kilowatt commercial-scale model. Final negotiations with ARPA-E are underway for an intermediate step: a 10-kilowatt version by 2015 . Arne Pearlstein, a professor of mechanical engineering who is a collaborator, told me that the commercial-scale version might be 10 meters wide but only two or three meters tall, and that the units would sit about 55 meters apart. These squat machines could bring renewable energy to regions that are bombarded by heat but don’t have much wind. (Though gusts of wind would only serve to make the turbine spin faster, Pearlstein said.) Pearlstein estimated that the Solar Vortex could spin out electricity 20 percent cheaper than wind turbines and 65 percent cheaper than solar photovoltaic panels. One form of saving comes from its potentially straightforward maintenance. “You’re talking about somebody getting up on a stepladder instead of going hundreds of meters up into a wind turbine to deal with a gearbox,” Pearlstein said.
Entrepreneur receives funding for ‘tornado’ power generator
December 18, 2012 / by Bob Yirka
Electrical engineer and entrepreneur Louis Michaud’s AVEtec company has received funding from PayPal cofounder Peter Thiel’s Breakout Labs program to build an experimental Atmosphere Vortex Engine (AVE). The $300,000 in startup funds is to go towards building a working engine to dispel or prove the viability of using such technology to produce electricity with virtually no carbon footprint. Michaud’s idea is to use a fan to blow some of the excess heat produced by conventional power plants, into a cylindrical hollow tower, at an angle. Doing so should create a circular air current, which he says will grow stronger as it moves higher. The higher it goes the more energy it draws due to differences in temperature. The result would be a controlled man-made tornado. To put it to good user, turbines would be installed at the base of the vortex to create electricity. The original test will be conducted at Lambton College in Ontario – the tower will be 131 feet tall with a 26 foot diameter. That should be enough to create a vortex about a foot in diameter – enough to power a small turbine. It’s just a proof of concept, Michaud notes on his site, a real-world tower would be about 25 meters in diameter, and would be capable of producing up to 200 megawatts of power using only the excess heat generated by a conventional 500 megawatt plant. Power goes up geometrically, he says, as the size of tower grows. He adds that the cost of producing electricity this way would be about 3 cents per kilowatt hour, well below the typical 4 or 5 cents for coal plants. Michaud has been investigating the idea of harnessing the power of tornado’s to provide electricity for several decades but until now has had problems being taken seriously by venture capitalists. He adds that his company built and successfully tested an AVE prototype in 2009, hinting that he has no doubts that the new tower and turbines will work as advertised. For those worried that a man-made tornado might get out of hand, escape its enclosure and wreak havoc on the nearby community, Michaud says that can’t happen because all it would take to stop the whole process would be to turn off the fan that feeds the vortex the warm air.
Inventor Louis Michaud watches as a tornado-like vortex rises from a small “vortex engine” in the garage of his Sarnia home in May. Michaud believes a full-scale vortex engine could be used to produce clean energy for 200,000 homes.
Taming tornadoes to power cities
‘Vortex engines’ fed by hot water from a nearby power plant could spin turbines, engineer says Tyler Hamilton / Jul 21, 2007
A curious-looking wood cylinder with a round opening at the top and a small heating element at the bottom sits in Louis Michaud’s garage, bicycles hanging overhead and a workbench pressed against the wall. The retired refinery engineer picks up a propane torch, lowers it into the opening, and lights a tiny piece of saltpetre. A loud fizzling is heard and a thick smoke begins to rise from the centre. At first the smoke has no form, but it soon swirls upward into a well-defined vortex – what, on a larger scale, you might call a tornado. “The air is being drawn in on its own. There’s no fan or anything involved,” says Michaud, explaining the physics of convection and how rising air behaves like a spinning top. “This is what’s going on in the atmosphere. The air is heated in the bottom by the sun and then it rises, cools and comes back down again.” It may seem like a hobby – a home science experiment meant to occupy time during retirement – but this 66-year-old isn’t just tinkering. Michaud has spent the past 40 years studying tornados and hurricanes, and is convinced it’s possible to engineer and control powerful, full-scale whirlwinds and harness their energy to produce emission-free electricity. Forget wind farms and their intermittent operation: the future of electricity generation could be tornado power on demand. Michaud has adapted this process to create what he calls a vortex engine, and has patented the invention in both Canada and the United States. Recently, he formed a company called AVEtec Energy Corp. with an aim to turning this unconventional – and to many, unthinkable – approach to electricity generation into a commercial reality.
His challenge now is to persuade venture capitalists, energy executives and at least one community to back the construction of a full-scale vortex engine, capable of producing a power-packed funnel cloud that stretches kilometres into the atmosphere and runs on waste heat, ideally from a power plant. “I’m talking about a 200-megawatt device, which would be 200 metres in diameter,” says Michaud. That’s enough electricity for 200,000 homes. “The vortex would be one to 20 kilometres high, and have 10 turbines (at the bottom) each producing 20 megawatts.” It’s a scary thought, and a great basis for a movie script, bringing together the don’t-mess-with-nature themes of the films Twister and Jurassic Park. One can imagine the back of this DVD case: “A monster man-made tornado loses control and jumps out of its pen, terrorizing a community and ripping a path through dozens of harmless wind and solar farms. Rated R.” Michaud concedes that ideas related to weather modification and “cloud seeding” are typically shunned by the scientific community and feared by the public. “People say it’s impossible initially. And then they say, well, if you can do it, it’s too scary – how are you going to control it?” he says. “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.” He’s critical of the vast majority of climatologists who focus exclusively on weather prediction, arguing that it’s a waste of their skills and research efforts. “I tend to think that prediction is not the way of understanding things.” It’s not likely we’ll be seeing tornado generating stations operating in Toronto anytime soon, but Michaud’s vortex engine is drawing attention, and has already attracted some research funding from the Ontario Centres of Excellence.
The University of Western Ontario’s wind-tunnel laboratory, through a seed investment from OCE’s Centre for Energy, is studying the dynamics of a one-metre version of Michaud’s vortex engine – like the one in his garage. The lab is also conducting computer simulations to look at the impact of cross winds on a 20-metre model. “When the idea was first brought forward we were like, `tethered tornados,’ hmmm … But we looked at the patent and thought it merited further study,” says Nicole Geneau, manager of business development at OCE’s Centre for Energy. “We have a strong history of picking things up that seem like crazy ideas, and at least giving them a shot. We should not stand in the way because of preconceived bias.” Rick Whittaker, vice-president of investments at Sustainable Development Technology Canada, which funds clean-technology demonstration projects, also keeps an open mind. “They’re not violating the laws of physics. The question isn’t whether this strange idea will work or not, it’s a matter of the degree to which it would be more economically attractive than the alternative. “That’s the type of idea we actually seek out.” The next step is to build and study the performance of a four-metre model, requiring a further injection of OCE funds of about $300,000. The plan would be to scale up from there, moving on to 10-metre, 20-metre, and 50-metre pilot plants, likely requiring millions of dollars in both public and private funding. On a commercial scale, the plant would require a heat host, such as a power plant, that could provide the vortex engine with a constant supply of hot water “fuel.”
Here’s how it works: Waste heat, a byproduct of any fossil fuel or nuclear plant operation that is typically vented into the air through cooling towers, is carried by water pipe to a vortex engine facility nearby. The hot water enters a number of cooling cells stationed around the facility where fans push dry air across hot pipes. The air picks up the heat and enters the vortex through 10 or more angled ducts, causing the air to swirl inside. The heated air begins to rise in a spinning motion, gathering energy the higher it gets and creating a vortex. As the vortex gathers momentum it begins to suck air through the cooling cells, at which point the fans that initially pushed in the air now function as turbines that generate electricity. As long as the heat is available, the vortex will keep spinning. Michaud figures that a commercial plant of between 200 metres and 400 metres in diameter could generate 200 megawatts of baseload power and be built for $60 million. But $20 million of that, he points out, would be offset because the power plant would no longer need a separate cooling tower. Compared to nuclear, even coal, it’s a bargain. Michaud estimates that one of his vortex engines would cost less than one quarter the cost of a coal plant, and that’s excluding the cooling tower benefits and the fact that no ongoing fuel expenses are needed to keep it going. Nilton Renno, a professor at the department of atmospheric, ocean and spaces sciences at the University of Michigan, has spent his career studying tornados and water spouts. He says there’s no reason why Michaud’s vortex engine wouldn’t work. “The concept is solid,” says Renno. Top atmospheric scientists from the University of Oxford, the University of Cambridge and the Massachusetts Institute of Technology have joined AVEtec’s advisory board. The group includes respected MIT meteorology professor Kerry Emanuel, perhaps best known for establishing a strong link between hurricane intensity and global warming. Still, Renno isn’t without reservations. He’s particularly concerned about the ability to control such a powerful monster. “The amount of energy involved is huge. Once it gets going, it may be too hard to stop,” he says. Michaud argues that the power of the vortex engine could be turned down, or shut off completely, by limiting the amount of air flow into the base of the funnel. He also dismisses any idea that his vortex engine would be loud and menacing, pointing out that tornados make noise and become more destructive as they draw debris into their funnels.
The vortex engine, by contrast, would be kept stationary in its arena and only draw in debris-free air, making it far less visible than a typical tornado. Renno isn’t convinced. He points out that as the vortex grows it would likely be able to pull in warm ambient air from many kilometres away, creating the possibility for debris accumulation and making it more difficult to manage. Asked whether he’d accept a vortex engine in his own community, Renno replied: “No, not close to my house” – at least not until the concept is proven. Whittaker of Sustainable Development Technology Canada says public demonstrations will be key to gaining acceptance. “Perceptions are created because of lack of information.” Michaud realizes he will need to break down a lot of mental barriers before pushing his idea beyond the stage of intellectual curiosity. He doesn’t rule out starting small, possibly promoting the creation of less powerful vortex engines as tourist attractions that the public can visit, see and learn about. “I was thinking if we got one of these to produce a tornado 200 metres high, the first people to buy one would be Disneyland.” If people accept it, the potential is unlimited. He says down the road, hundreds of vortex engines could be located in the ocean along the equator, where the warm tropical water would provide an endless source of energy. Why would anyone do such a thing? To cool the planet, Michaud says. Greenhouse gases in the atmosphere are what prevent the sun’s heat from radiating back into space, he explains. A series of controlled tornados along the equator would carry that heat to the outer edges of the atmosphere, where it could more easily escape. In other words, Michaud believes man-made tornados could function as exhaust systems for the planet, a massive air conditioner that could help manage global warming. There’s simply too much at stake to ignore this potential, he says. “I could work as a consultant and get more money for the effort, but this is something I like doing. If you realize there’s a potential there and nobody is doing anything about it, I don’t think it would be right for me to say, okay, nobody is listening – too bad.” Whatever the outcome, Michaud’s four grandchildren, aged 4 to 8, are loyal backers of his work. Whenever they visit, the first words out of their mouths, says Michaud, are: “Grandpa, can you show us the vortex again?” And his wife? “She’s been quite patient.”
lmichaud [at] vortexengine [dot] ca
Mechanical energy is produced when heat is carried upward by convection in the atmosphere. A process for producing a tornado-like vortex and concentrating mechanical energy where it can be captured is proposed. The existence of tornadoes proves that low intensity solar radiation can produce concentrated mechanical energy. It should be possible to control a naturally occurring process. Controlling where mechanical energy is produced in the atmosphere offers the possibility of harnessing solar energy without having to use solar collectors. The Atmospheric Vortex Engine (AVE) is a process for capturing the energy produced when heat is carried upward by convection in the atmosphere. The process is protected by patent applications and could become a major source of electrical energy. The unit cost of electrical energy produced with an AVE could be half the cost of the next most economical alternative.
A vortex engine consists of a cylindrical wall open at the top and with tangential air entries around the base. Heating the air within the wall using a temporary heat source such as steam starts the vortex. The heat required to sustain the vortex once established can be the natural heat content of warm humid air or can be provided in cooling towers located outside of the cylindrical wall and upstream of the deflectors. The continuous heat source for the peripheral heat exchanger can be waste industrial heat or warm seawater. Restricting the flow of air upstream of the deflectors regulates the intensity of the vortex. The vortex can be stopped by restricting the airflow to deflectors with direct orientation and by opening the airflow to deflectors with reverse orientation. The electrical energy is produced in turbo-expanders located upstream of the tangential air inlets. The pressure at the base of the vortex is less than ambient pressure because of the density of the rising air is less than the density of ambient air at the same level. The outlet pressure of the turbo-expanders is sub-atmospheric because they exhaust into the vortex.
The Atmospheric Vortex Engine has the same thermodynamic basis as the solar chimney. The physical tube of the solar chimney is replaced by centrifugal force in the vortex and the atmospheric boundary layer acts as the solar collector. The AVE needs neither the collector nor the high chimney. The efficiency of the solar chimney is proportional to its height which is limited by practical considerations, but a vortex can extend much higher than a physical chimney. The cylindrical wall could have a diameter of 200 m and a height of 100 m; the vortex could be 50 m in diameter at its base and extend up to the tropopause. Each AVE could generate 50 to 500 MW of electrical power. The average upward convective heat flux at the bottom atmosphere is 150 W/m2, one sixth of this heat could be converted to work while it is carried upward by convection. The heat to work conversion efficiency of the process is approximately 15% because the heat is received at an average temperature of 15 C and given up at an average temperature of -15 C. The average work that could be produced in the atmosphere is therefore 25 W/m2. The total mechanical energy produced in the atmosphere is 12000 TW (25 W/m2 x 510 x 1012 m2) whereas the total work produced by humans is 2 TW. The quantity of mechanical energy which could be produced in the atmosphere is 6000 times greater than the mechanical energy produced by humans. The thermodynamic basis of the AVE is consistent with currently accepted understanding of how energy is produced in the atmosphere. Atmospheric scientists call the mechanical energy that would be produced if a unit mass of air were raised reversibly from the bottom to the top of the troposphere Convective Available Potential Energy (CAPE). CAPE during periods of insolation or active convection is typically 1500 J/kg which is equal to the mechanical energy produced by lowering a kilogram of water 150 m. The vortex would transfer the mechanical energy down to the Earth’s surface where it would be captured.
Producing and capturing the work requires that the expansion process be carried out at mechanical equilibrium. Without a mechanism such as a turbo-expander, mechanical energy reverts to heat and is lost. Work is produced when a gas is expanded in a turbine; however, no work is produced when a gas is expanded through a restriction. There must be an expander with a shaft to get the work out of the system. The design of the AVE station compels the expansion to take place at mechanical equilibrium and at a specific location. The quantity of energy which could be produced by the AVE process is far greater compared to the kinetic energy of horizontal winds captured by conventional horizontal axis wind turbines. The AVE process can provide large quantities of renewable energy, alleviate global warming, and could contribute to meeting the requirements of the Kyoto protocol. The AVE also has the potential of providing precipitation as well as energy. There is reluctance to attempt to reproduce a phenomenon as destructive as a tornado, but controlled tornadoes could reduce hazards by relieving instability rather than create hazards. A small tornado firmly anchored over a strongly built station would not be a hazard. The AVE could increase the power output of a thermal power plant by 30% by converting 20% of its waste heat to work. It is estimated that it would be possible to establish a self-sustaining vortex to demonstrate the feasibility of the process with a station 30 m in diameter under ideal conditions. Learning to control large vortices under less than ideal conditions would be a major engineering challenge. Developing the process will require determination, engineering resources; and cooperation between engineers and atmospheric scientists. There will be difficulties to overcome, but they should be no greater than in other large technical enterprises.