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


June 18, 2014

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

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.

About the Author
Darren Quick Darren's love of technology started in primary school with a Nintendo Game & Watch Donkey Kong (still functioning) and a Commodore VIC 20 computer (not still functioning). In high school he upgraded to a 286 PC, and he's been following Moore's law ever since. This love of technology continued through a number of university courses and crappy jobs until 2008, when his interests found a home at Gizmag. All articles by Darren Quick

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:


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!


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.


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.

Mel Tisdale

I think this is a better idea

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.


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.

Simon Gibson

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.


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.


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.

Joel Joines

@ 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.


What a truly horrible idea. 685 m tall? That's taller than virtually every skyscraper in the world. It only works well in hot dry environments but consumes water? That just doesn't make sense. In a hot dry environment there typically is no water to spare. That's why it's hot and dry. True you can build it beside the ocean, but then you would probably have to desalinate the water first, which takes energy. The cost of building something like this would be huge.

Jim Bruin

Winter icing will be it's downfall and coat every thing down the tube including the generating fans, and the vibration of fans will be , well you guessed it, and as it builds up and then the water will rust this and that, and what happens in minus 20 to minus 40 climate Lets not consider the cost of lifting water to the top of this stack, It will be a problem in colder climates. Then to prevent any of this lets consider the materials that are needed to ward off some of this. WOW, Should it cost a fortune?

Cma Energy

this device must suck energy off the grid to pump water up a tower to mist it in the air and let the air drop.

this is a battery storing grid electricity in the form of pumped water.

wether or not it is a net electricity generator is another story.

but it is most definitely an inefficient method of generating electricity.

and probably a highly expensive battery.

and when you look at the funding for this research project achieving commercial funding levels; it's fraud.

you cannot fund 'test' projects at commercial levels. it's grossly negligent waste at best, and most likely fraud.


@thk No solar towers work at night too, due to the heat radiating from the ground after its been heated up in the night. Read the article its very interesting.


Not a bad idea. With the moist, cool air escaping the bottom, why not utilize that resource to cool a city or town buit around it?

Tina Elgersma Krikke

This sounds like a really bad idea. How does it get a positive energy balance if it has to transport the water that is used for cooling up? It seems like a silly idea. Also there is a similar concept that uses heated air flowing up in the tower (chimney effect) to drive turbines. Why is this better than the other concept? Both seem to be ridiculously large! I think the money would better go into the development of nuclear power.


Why build a tower when you can tunnel into a mountain lol or lay huge pipes up the side of the mountains.


Interesting idea! However, someone said it would have no emissions when in fact it will be emitting the most predominant greenhouse gas -water vapor. I have to wonder how much water it will lose to evaporation and how this increased humidity will affect the local environment and local climate. That water is absorbing and storing heat that might otherwise have been radiated back into space as it evaporates and will then go on to affect the albedo of the surrounding area. How will this affect the area? Will it create yet another anthropogenic heat island? Perhaps this is comparable to the heat and vapor emissions of a natural gas power plant with a much smaller carbon footprint?

Water in the Arizona desert is the rarest of resources.The Colorado River is fairly well emptied by upstream demands of Arizona and California metropolitan areas and agricultural operations here.

In essence they have looked at industrial AC systems. The first issue is the huge amount of water that will be required. The second issue is lifting all that water to a height. Then there will be issues with calcium carbonate and algae. My best guess is that older designs that use a black tower with an updraft that spins a large blade at the exit point at the top is more efficient. And that design needs no water and does not need to lift anything at all. Jim Sadler

Please visit to see a new city design that uses two Solar Chimneys for a 1.2 million population. Observe the proportional land requirements for urban footprint, organic and polyculture integration and forest/plantation requirements. Notice the mixed use transportation and mixed use structures. The sun heats the canopy as one source for heating the air thereunder. The ground can be either blacktopped or heated as was proposed for Taft City, CA. This additional heat source should make the system far more efficient. Regarding the tall chimney a stressed cabled lightweight gas filled envelope structure would be far more economical than the heavy weight concrete and footing requirements proposed. Worth thinking about!


Just because you can do something doesn't mean you should do it. Pumping water up 2250 feet? It's efficiency must be poor and it only works where it's warm. Ho hum.


An excellent idea and a similar concept to another I've seen on Gizmag. Using this tower with its evap effect (day time) combined with the other, which uses heated air from the ground (hot air rising @ night), you could program it to generate electric to different environmental conditions. In the Zone (or any desert for that matter), the ground stays warmer than the surrounding air at night. So, you could use the sinking air during dry daytime periods and rising air at night to generate electric. A Venturi effect could be beneficial and placement of the generators would have to be optimized as well.


Another silly expensive and unworkable "energy" project that will fail, perhaps catastrophically, and make it more difficult to fund real alternative energy.

Charles Smarr

Would getting the water to the dry site be cost effective? It will be interesting to see this in action.

Lisa Bell

Mel Tisdale: I am with you. I dream of the day when local municipalities can generate their own electricity and not have to buy it on the market and have it transported hundreds of miles with the attendant losses through the system.

LFTR is the idea whose time has come and we need to get behind it in a big way. Let it prove itself and then jump on board.

Oops, I forgot about those big corporations that have invested billions into producing the fuel rods for the current, dangerous, inefficient, high pressure, meltdown capable nuclear type of reactor. By the way, whose inventor did not want the technology used for electricity generation for the public.

I honestly hope that LFTR gets the required funds to prove the technology.

This type of system with a tower of unbelievincredible height seems far fetched and yet it received money? Wow!

It doesn't seem likely that many places are going to authorize you to build a tower a half mile high. It could be an eyesore for several towns if in a rural area.

I feel for the guys who would have to change the light bulbs on the blinking lights at the top!

As an aviator I say "hell no"!

Dr. Veritas

Why build this when you can build tunnels on top of mountains, to the bottom and use the pressure changes to turn turbines, plus we have water problems out west.

Leonard Foster

Simon: Air cooling draws the majority of electricity. At night, that drops. In the winter when output is way down, so is need. This might work, but I wouldn't invest.

Don Duncan

I think it's a great idea, however a bit of a waste of a huge structure if it only does what it says in the article. Why not cover it in solar panels and verticle free wind turbines? It would have to use seawater so could produce salt commercially.

We have wind farms everywhere so if the concept goes ahead it will have to be accepted in the same way as we accept and even cherish the wind farms but to me it seems logical to have it as an 'all in one' energy plant. Ugly it certainly is, but far fewer of them will be needed if every square inch of these concrete tubes are utilised.


Are all the naysayers here complaining about how horrible this technology would look or get in their way... just take a look at a coal burning plant or leveling mountains! Yeah, that's beautiful... The idea about tunneling a shaft through a mountain is a good idea. First of all, lobbyists/corporations would never let this happen, but I see the real problem with the public... All this crying about inconvenience is nonsense. Everyone talks about doing something to 'Save the Planet', helping the environment, but doing nothing is the REAL PROBLEM here. Just think about the early 1900's and people complaining about those 'NOISY AUTOMOBILES'! Stick with them great horses (we would probably be better off). Get a grip folks and put your action where your mouth is! We've been spoiled rotten our whole lives, now it's time to step up... The oil companies love your complaining, LOL... Don't you worry, nothing will ever spoil your beautiful view!


So it pumps water to the top, the water falls to the bottom, inducing a wind which is directed into turbines. How is it getting more energy out of the falling water/wind than the energy required to pump the water to the top. Let me guess: They simply leave out the pumping energy requirements from their calculations.


@Vilguy This not a perpetual motion machine! The energy comes from the Sun. The evaporating water collects the energy. I think it's a great idea.


Of course, the energy used to pump the water and the water that is not recovered mean nothing. As was mentioned the pollution caused by the manufacture of this monstrosity ond it's operation are not to be considered.

P.T. Barnum, welcome back!

James Smith

If there was a location suitable for this, close to a supply of water that could be piped down from a higher elevation, then it would work.

Otherwise most of the power generated wil have to go right back in to pumping the water up to the top.

I've seen this concept before, several times, possibly even before the people who have "invented" it this time around were born.


A good writeup from 33 years ago on Carlson's original scheme, as SiteGuy noted in the first comment, with detail more accessible to those not scientifically inclined:


Roger, it's not about falling water creating a draft. Water cools the air. If you can cool 20 tonnes of air with 1 tonne of water (I don't know how much, it's just an example) then if you're lucky you can come out ahead. Okies.

Craig Jennings

No emissions hey. I'd like to see the LCA for such a project with accurate carbon payback periods calculated. What about the distribution infrastructure required to transport the power from "hot dry zones... with an abundance of water" to where the majority of the population lives?

Interesting concept but a fail in general. The max energy that can be extracted is derived from E=1/2MV^2. Air, even cold air has a density of 5/8 of 7/10 of 4/5 of SFA. The energy density is nothing, hence the only way to improve the power calc is to pump up the velocity which requires a significant temp drop between the inlet and outlet.

Better advances in the production and storage or hydrogen from domestic scale renewables is the future. The era of massive centralised power generation is coming to an end.

On another note, water vapour is a GHG; however, it readily gives up the absorbed energy via condensation, CO2 does not. This is the fundamental problem for those of you who have NFI about thermodynamics, The rate of CO2 production exceeds the capacity of absorbing processes (carbon cycle), therefore the amount of CO2 trapped in the atmosphere increases. This in turn absorbs more energy in the form of heat (IR radiation) and the cycle perpetuates. Increasing CO2 concentrations (in atmosphere) will store more energy within the atmosphere i.e. more heat. This additional 'heat' energy will attempt to reach equilibrium (that thermodynamics thing again...) with the final result being a lower energy level. Increasing the energy density within the atmosphere increases to rate at which the system tries to achieve equilibrium. This increased flux is what drives the notion of more severe weather events as a result of global warming. It's all the same processes with the exception of more energy.

Hope this helps for those who have NFI!

Aaryn Johansen

the siliness of needing water in a "hot, dry" environment has already been pointed out above, as has

As for the cement, there are options that use CO2.


Seems very similar to this

Andrew Larmour

The video uses some inaccurate language "the dry air absorbs moisture and gains weight" suggesting that the weight of the moisture is what drives the tower. Of course the falling moisture only adds as much energy as it took to pump it up there in the first place. The useful energy comes from the air density increase due to evaporative cooling.

Tony Morris

The only advantage I can see is to the inventors - hidden cost overrun etc will soak up the money from investors like a sponge. At least it may be less noisy and a bit less ugly than turbine wind farms. The only profit generated by them is the subsidisies to makers and the payments given to farmers and landowners allowing the positioning of these blights. Check out where the money is going V power generation happening in the UK.

The Skud

What is it with this site and incorrect units? The plant's generating capacity is given in megawatt-hours, which is a unit of energy, not power. The correct unit is megawatts, unless they're referring to the amount of energy generated in a day - but then they should say that.


Stupidest idea since before they learned to slice bread! They need to paint the tower black, and focus mirrors on it and make the hot air go UP! Secondly they need to make the intake air go through tunnels deep enough to cool the air, and take advantage of the pressure and temperature differential. Why fight the entropy war, and even pay for the battle, by trucking in and pumping water up to the top of this thing; when, you can place your wind mills in the the NATURAL flow of entropy, and harness that energy without the need to waste precious water resources? DO NOT do this thing as designed I am BEGGING you! You haven't the slightest idea what you are doing!


It sounds a great idea in principal and weren't there plans to build one inside of a mountain some years ago.

They say; "where it [water] 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.". I don't think so!, when air absorbs water and becomes humid and less dense (lighter) it rises, you can't just spray water into warm dry air and expect it to fall as the reverse will happen.

There are of course proven methods to cool air while keeping it in a dry state but how efficient this would be, I don't know. And a tower some 2,250 ft (685 m) tall; don't forget that air is 2 degrees cooler for every 1,000 ft of elevation above ground level so this is a plus as some cooling has already taken place and it wouldn't take long to induce a significant amount of temperature differential in the incoming air to create quite a powerful wind if you could keep the air dry.

I wish them well as the idea has merit. Dan

Facebook User

"the output for a year would average out to approximately 435 MWh." This is 435 MW for 1 hour or 1 MW for 435 hours !

Have they or you got your units right ? This is akin to "mah" used with batteries. It is the total energy stored. To get even average output power you the calculation would go something like 435 /24 hours per day / 365 days per year. This would give you an output of something like 50 KW. What can you do with this ????

A height of 2250 feet ? This is like 2 Sears towers stacked one on top of the other.


Craig Jennings - you described the concept correctly. The ratio is about one ton of water to cool 200 tons of air. The air shrinks about 3% in this process.

Tony Morris

They don't publish the net specific power generated by the system or how much water is lost per MW-hr of energy produced. Without those numbers this is snake oil to me.

It can only create air flow if the temperature is high and the dew point is very low. That limits where this idea could be implemented even if it can be economical.

It relies pumping a lot of water up a long distance which uses a lot of energy. Pumps may be in the 50% efficiency range so you lose a lot of energy there. It also relies on evaporation of water to produce the cooling effect. That means it creates a net loss of water. Couple that with the fact that it will only work in very hot and dry climates where there will likely be water shortages and the potential areas it could be installed are narrowed even more.


Since this is like all the other something for nothing schemes with their rather intermittent output anyone building this should be required to also build on the site a hot spinning reserve generator of 1.25 times the rated output of the scheme. Such reserve generator should have its output so balanced that the power going into the grid is constant. Also any power supplied by the spinning reserve should not be counted in subsidies paid.


It's amazing that here, like all over the internet, people think that they point out problems that the designers have never figured out, even considered for a moment, nor do they think ("I'm BEGGING you!!") that funding will simply show up, no questions asked, no analysis, nothing.

Why do people get all apoplectic when there is an announcement like this? Then write stuff about the black solar tower (air going up) as if no one has ever conceived of it (I thought of it in the 1970s, and I am certain I am not the first!!!). There's this huge rush by egomaniacs to point out flaws. Gosh! You (YOU!!!) are a g-e-n-i-u-s!!!

Gizmag gives things a "10,000 foot view", and maybe a "1000-foot view", but if you're interested in arguing engineering, I suggest you contact those firms and people that are touting this idea, NOT spew all over Gizmag comments!

That is simple narcissism. Encourage these people to build it. Don't be a denouncer.

Scott in California

@vilguy; You seem to be under the (false) impression that the "laws" of physics cannot be broken…they can, and at least one that I know of has been. Perpetual motion is coming, laws of physics or not; at least, that's my prediction. As for most of the rest of you (constant) naysayers, I hope you're not always this negative, but I have a feeling you are.

Old J Hawthorne

I read about this years ago in popular science.Always wondered if the cool dense air it moves to ground level would prevent tornadoes from touching down.


@ Facebook User Cool air is heavier than warm air even count the difference that the water vapor makes.


Calling this "solar" looks fraudulent to me.

Slowburn Link to the company which proposed an updraft solar tower. Isn't it better? No wastage of water.

Prateek Jain

No one mentioned how strong this tower would have to be to withstand prevailing winds, storms or even an earthquake. Pumping water that high would require about 900 psi and a very high flow rate. A large portion would be lost due to evaporation. And my last question, why have all those small wind turbines at the bottom instead of a larger turbine in the center at the bottom of the tower that would seem to be more efficient. I have no idea what it would cost to construct this thing but I suspect it would be a loser, a big loser.


might turnout to be a great idea,but a million and a half won't go far towards building a giant tower more than 600 meters tall,the huge walls around the tower could be fitted with solar cells to help produce the electricity necessary to pump the water to the top and for electric production when its not very hot,,also if a windy location is chosen it could also be adapted to help turn the turbines when the weather is not so hot.

Salvatore Cento

Another concept that seems 'iffy' at best. The main problem that I see is having to locate such a structure in a hot arid area which will require a lot of water to operate. There are also updraft tower that are similar but work in reverse and don't require the use of water. I would think that the latter makes a bit more sense and one is, if I'm not mistaken, already built or in the works.

Edward Kerr

Unlikely to ever see fruition. This takes a method of generation which doesn't require any water and makes it require probably as much water annually as a coal plant and only works in desert conditions. There's a reason why updraft and downdraft towers keep getting reinvented every decade, and it's not because they work, it's because credulous investors can be found every decade for R&D dollars.

Mike Barnard
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