Environment

Solar Wind Energy's Downdraft Tower generates its own wind all year round

Solar Wind Energy's Downdraft ...
Solar Wind Energy's Downdraft Tower generates its own wind that is directed down the hollow tower and through turbines placed around its base
Solar Wind Energy's Downdraft Tower generates its own wind that is directed down the hollow tower and through turbines placed around its base
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Solar Wind Energy's Downdraft Tower generates its own wind that is directed down the hollow tower and through turbines placed around its base
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Solar Wind Energy's Downdraft Tower generates its own wind that is directed down the hollow tower and through turbines placed around its base

When we think of wind power, we generally think of huge wind turbines sitting high atop towers where they can take advantage of the higher wind speeds. But Maryland-based Solar Wind Energy, Inc. is looking to turn wind power on its head with the Solar Wind Downdraft Tower, which places turbines at the base of a tower and generates its own wind to turn them.

Described by the company as the first hybrid solar-wind renewable energy technology in the renewable energy market, the tower at the center of the system generates a downdraft that drives the wind turbines positioned around its base. This is done by using a series of pumps to carry water to the top of a tower standing up to 2,250 ft (685 m) tall, where it is cast across the opening as a fine mist. The mist then evaporates and is absorbed by hot, dry air, thereby cooling the air and making it denser and heavier than the warmer air outside the tower.

This water-cooled air then falls through the hollow tower at speeds up to and in excess of 50 mph (80 km/h). When it reaches the bottom of the tower, the air is directed into wind tunnels that surround the base, turning wind turbines that are contained within the tunnels. Although the system requires large amounts of water, the bulk of the water emitted at the top of the tower is captured at the bottom and recirculated through the system, being pumped back up to the top with some of the power generated by the wind turbines.

In this way, the company claims the system can generate electricity 24 hours a day, 365 days a year, when located in a hot, dry area – although electricity generation would be reduced in winter. Depending on the tower's geographical location, electricity generation could also be supplemented through the use of vertical "wind vanes" that would capture the prevailing wind and channel it into the tower.

Solar Wind Energy says it has developed proprietary software capable of determining a tower's electricity generation capabilities based on the climate in geographic regions around the globe. Using the software, the company says it can predict the daily energy outputs of a tower based on its location and size.

Based on the most recent design specifications, the company says a tower designed for a site near San Luis, Arizona, would have a peak production capacity on an hourly basis of up to 1,250 MWh on sunny days. However, when taking into account the lower generation capabilities during the winter months, the average hourly output per day comes out to approximately 435 MWh.

The company points out that once built (using conventional materials, equipment and techniques), its towers are capable of operating throughout the year independent of wind speeds with virtually no carbon footprint, fuel consumption or waste generation.

Earlier this year, Solar Wind Energy gained the necessary local entitlements to pursue development of its first tower near San Luis, Arizona. The project got a leg up earlier this week when it announced a financing agreement with JDF Capital Inc., which will provide up to US$1,585,000 to the company. Solar Wind Energy says it is also exploring potential sites in Mexico, which along with the Middle East, Chile and India, would be an ideal location for the technology in terms of climate.

The video below explains how the Downdraft Tower works.

Source: Solar Wind Energy Inc.

Solar Wind Energy Tower Demonstration

63 comments
SiteGuy
A bit of background on this invention: the concept was patented by Phillip R. Carlson in 1975. The patent was titled "Power generation through controlled convection (aeroelectric power generation)". Research and engineering work towards a practical system was done by Professor Dan Zaslavsky of the Technion in Israel, together with several other collaborators around the world. They published a detailed paper on the subject in 2001. The research continued and was updated over the course of the following eight years. Although working prototypes were proposed, finding serious investment capital was always the obstacle. The first company to follow through and build a commercial solar tower is Solar Wind Energy, Inc. In that sense the company is pioneering, since the success of the San Luis, Arizona project will no doubt generate wide interest and serious investors from around the world for similar projects in places with suitable climates, thereby kickstarting the technology. In the long run and taking into account the capital and running costs, the electrical power supplied by an "energy tower" costs about one third that of a plant run on fossil fuels. Wikipedia has a decent overview here: http://en.wikipedia.org/wiki/Energy_tower
vilguy
The proposal is a perpetual motion machine in effect.... good luck with that! however well done to them for blagging over 1.5 million out of an investor! "In this way, the company claims the system can generate electricity 24 hours a day, 365 days a year" so on a winters night I can expect this white elephant to be keeping me toasty warm? and finally... 685 m high!!!! How much carbon would be emitted from the production of the concrete alone in its construction!
martinkopplow
The concept is certainly new and it is great to see new ideas being developed in this industry. I have concerns regarding the performance stated, though. The air will only be cooled down so many degrees, and all the energy harvested comes from the added density of the air mass inside, so it can be easily calculated. It is kind of an inverted hot air balloon, only it is a continuous process that creates a certain pressure difference at the bottom to drive the turbines. The shape of the tower does not appear logical in this context, and the turbine setup looks not very much sophisticated, which makes me wonder how well thought out this overall concept actually is. Also, I wonder how much water needs to be pumped up the tower, and how great the difference in potentioal energy of the water pumped up and the air streaming down will finally be. It could well turn out to be a nice scheme tailored only for accessing public subsidies.
Mel Tisdale
People already complain about wind turbines - me included - heaven knows what they'll make of these blots on the landscape. Six hundred and eighty-five meters tall and almost as wide at its base! How long before some advertising clown has them covered with messages persuading us to buy this, holiday there, or do whatever? What on earth would Wordsworth make of a host of golden bill boards? If it weren't for the Green nuclearphobes, we would be well into a LFTR 'Manhattan' type of project by now, and given the urgency of the energy supply situation, possibly even have operational prototypes. It would only be a small step from there to having production lines producing small modular reactors, which would mean that not only would we not need devices such as these, we would also not need the supporting grid whose pylons serve to further spoil the environment to an unacceptable extent. LFTR power generation, being local, very local, and not requiring copious amounts of water, could be sited wherever suits the local requirements best, probably in a unit or two on an industrial park. We could then phase out the water cooled nuclear reactors and all the problems they pose, most of all, the availability of suitable uranium. (Thorium is a waste product of rare earth mining and the mines would supply for free as it is a problem for them to dispose of.) Heaven help us if we have to rely on these scaled up, look alike, inverted, vending machine beakers scattered about the countryside as if dropped by some giant litter-lout. Technically feasible they may be, harmonious with the environment they most definitely are not.
FabianC
I think this is a better idea http://www.gizmag.com/enviromission-solar-tower-arizona-clean-energy-renewable/19287/ It works on temperature differential rather than absolute temperature which allows it to be built almost anywhere. it also requires no water and no electricity to generate power. No pollution, it only emits hot air.
Simon Gibson
As parts of America are currently suffering from record droughts, and the potential is for the climate to get worse, would this be a good, efficient, use of the surrounding water resource that could be used for humans/crops? Obviously this is dependant upon the consumption by the tower. If the output is 1,250 MWh on sunny days but a yearly average would work out to approximately 435 MWh then the winter output must therefore be much less than the average of 435 MWh. What makes up the winter shortfall in generation? The technology looks fascinating and I hope a full size tower is constructed as we must fully investigate every source of clean electrical generation technology but should make sure that we don't create a potential of causing another problem in doing so.
windykites
It would be interesting to know what percentage of water is lost through evaporation. I would have thought that water would be at a premium in hot dry desert conditions, and probably better used for growing crops. An alternative idea would be to have a tower painted black. This would heat up in the sun, and the air inside would naturally rise upwards. Fans fitted at the base would work to generate electricity, but no water is required. The estimate for the amount of electricity generated is probably rather generous I would feel, and the capital cost of building must be quite high, with all those fans and generators requiring maintenance.
BigGoofyGuy
On a hot day, the wind created from it that comes out the bottom would be welcomed by those who are hot and need some sort of breeze.
Joel Joines
I have to agree with other comments. Using water to generate the downdraft is silly. Especially with the EnviroMission using essentially the same structure, but not requiring the waste of water. The only place I could see this being useful is when the generation location is close to the ocean and seawater could be used. These locations tend to not have "hot dry air" though so the evaporation would be less dramatic and cooling less noticable.
thk
@ martinkopplow, It is shaped like a Venturi to maximize the speed of the airflow to drive the turbines. Still, it would be interesting to see if a pilot plant could live up to all expectations. @ FabianC, Solar tower works only when there's daylight and batteries may be needed to store excess.