Wind Power Tower Proposed for Desert Areas

May 17, 2014

Fast Company:

If the Solar Wind Downdraft Tower is ever built in the Arizona desert, it truly will be a wonder of the modern world. At 2,250 feet, it would be taller than the new Freedom Tower in New York (1,776 feet), and 1,000 feet higher than the Empire State Building. It would have 120 huge turbines at its base, and enough pumping capacity to keep more than 2.5 billion gallons of water circulating. And it would have colossal power output: the equivalent of wind turbines spread over 100,000 acres, or as big as the Hoover Dam.

That’s the plan, anyway.

The idea goes like this: Water is sprayed at the top, causing hot air to become heavy and fall through the tower. By the time it reaches the bottom, it’s reaching speeds of up to 50 miles per hour, which is ideal for running the turbines. The advantage over standard solar and wind energy is the plant runs continuously, day and night. There are no intermittency issues from the sun failing to shine, and you don’t need to dust off any solar panels to keep things going. As long as the air is warm enough (which is likely in Arizona), the tower will keep creating draft effects.

The plant itself runs under its own generated energy: about 11% of output goes to pumping the water to the top again, and about three-quarters of the water is collected at the bottom, according to Ron Pickett, CEO of Solar Wind Energy Tower, the Maryland company behind the design.

“This is totally clean energy that actually makes money,” he says in an interview. “It makes energy at a cost comparable to if you were using natural gas to power a plant.”


51 Responses to “Wind Power Tower Proposed for Desert Areas”

  1. Again, this is just noodling. Their patents don’t address the physics.

    The initial condition, before mist injection, is that the physical states of the interior and exterior air are the same. As the mist falls through the tower, IMO, the natural gas law will dominate surface pressure differential. Therefore, air will enter the tower via the wind tunnels until equilibrium. During the cooling off period the interior will be lower pressure than the exterior.

    Once the interior air is more uniformly cool and dense, then the force per unit area at the surface will dominate. The air inside the container will have more mass than the surrounding exterior air, therefore there will be a higher pressure in the container as a function of the container’s height. (At the top, very little difference. Greatest at the surface.) According to handy lookup tables, if the surface pressure difference is about 300 Pascals, the wind velocity through the wind turbine tunnels would be about 50 MPH, ignoring resistance imposed by the tunnels. Pascals? Me too. 1 pascal = the more familiar unit 0.01 millibars Therefore, a 3 millibar increase in interior pressure would create 50 MPH winds not taking air flow constraints into consideration – which in this case would be a very significant factor.

    Without grinding out more arithmetic, I bet a 3000 foot tower (wow!) would generate 3 millibars of added pressure under reasonably good conditions. However, aren’t much of thunderstorm wind speed due to cyclonic forces? The towers would have to cover a large area before Coriolis force kicked in. Wind shear won’t happen.

    • dumboldguy Says:

      Their patents are mainly BS about proprietary software and things removed from the basic physics and engineering involved. Maybe they have some kind of slats/doors they can deploy over the wind tunnel openings to manage the startup phase if what you conjecture is really a problem?

      I also don’t see that the inside will ever be at “lower pressure” during the cooling off period. Before startup, everything inside all up and down the air column should match conditions on the outside. Once the first water injection occurs, the temperature will drop, the density will increase, and the “pressure” of the column will increase. I would think that they should inject water not just at the top but put some in all up and down the interior as well.

      I wasn’t thinking of lateral windspeeds in thunderstorms, but rather the downburst situation, which is analogous to what the tower is designed to do. We had one downburst situation here a few years ago that hit 85mph and cost me three good-sized trees—-broke the top 15′ off one and threw it 50 feet across the yard..

      • I think we agree on the steady state physics. The physics during the transition from initial condition to steady state is where we disagree. That’s a brief period, so it’s practically irrelevant. My hunch is that if the air in the entire tower were instantaneously cooled, the pressure would fall until more molecules entered the chamber. (P = nrT / V). As “n” increases and stabilizes, then the surface pressure would increase and become the dominant force at the surface. It’s a nit. Maybe their project is one of those “interesting” ideas. Seems that we understand that we agree that building 3,000 feet tall towers in the desert is a business plan that would attract a lot more scrutiny than we can bring to the table.

        • dumboldguy Says:

          I don’t think we disagree at all—-we just don’t have enough info to see the problem clearly. The gas laws don’t exactly hold true because the addition of water molecules actually changes the composition and weight/density of the gas—-it is not a closed system, dry air is not quite the same “stuff” as moisture-laden air, and injecting the water DOES provide the “more molecules” to the air column without even considering the air flow in at the top. I am not going to get a headache trying to figure the physics out beyond that because it’s clear to me that the main thing that they want to increase at this point in time is the bank accounts of the original shareholders. The concept seems sound but they need to build one and show that it works. If it does work, and the SHTF with climate change soon so that we have to try to quickly mitigate, there will be much money to be made with SWET.

          The stock traded in a range of $.01 to $.30+ during its first runup a couple of years ago before it dropped back to a penny or two. It is being touted on many investment “advice” sites right now, and I would suspect that those tens of millions of shares owned by the Superior Silver Mine boys will soon be in play again. One of them seems to have sold a bunch during the first price runup.

          Anyone who watches what the stock does (and has the nerve and $$$ to risk) might make a few bucks by riding any future bubble that occurs—-buy at a penny and sell at a quarter—-remember the 90’s?. Actually, considering that average daily volume is ~6 million shares and the stock has had several “daily doublings” and dropbacks over the past month that it has been back in the news, someone is already surfing on it. Buying 6 million shares at $.005 and selling at $.010 is $3000 in the pocket—-do that once week for a year and pocket ~$150,000. The HFT boys WILL be playing games with this one. Read between the lines of this quote for the real “focus” of this venture.

          “The Company secured the site for its first tower project in the U.S. in the City of San Luis, Arizona and may have its first Tower ready for operation there as soon as 2018. Aside from the development of this Tower, the Company is focused on licensing its development know-how and establishing partnerships at home and abroad to propagate Tower projects and in turn, receive licensing fees for territories, development fees during construction, and recurring royalty fees based on the actual kilowatt hours produced by the Tower”.

      • I would think that they should inject water not just at the top but put some in all up and down the interior as well.

        Ideally, you’d evaporate water until the air was saturated (thus at maximum density) at the very top of the tower.  Unless there was significant heating from compression on the way down, there would be no point trying to evaporate more water.  Anything you put in the tower for this, such as spray bars, would cause air drag and reduce the available output.  The standard lapse rate of 3°C per 1000 feet wouldn’t make it terribly worthwhile on a 300 meter tower, but a 1 km tower could probably benefit.

        Fine droplets of water in saturated air would begin to evaporate as the air heated by compression, so some excess water added at the top would serve as well as water sprayed at lower levels.  The upside is less gear, the downside is a little extra pumping work.

        Pressure in the tower is going to depend where you restrict the flow.  Put the fans at the top and it will be under vacuum; at the bottom, it’ll be under pressure.

        This idea has been around for a while, and it’s neat enough that I hope someone builds one just for the sake of building one.  I’d give them double coolness points for building it out of Accoya.

        • dumboldguy Says:

          Yes, it certainly is a “neat” concept, but I would suggest you NOT sell your B-H Class A’s to invest in this. The only ones guaranteed to come out ahead on this deal are the Superior Silver Mine folks (who never owned or operated a mine).

          We can talk about the physics endlessly, but until they build one, we will never know if it works. In my searching, I found a new supposed “benefit”—-if you use salt water, you will actually be distilling it and will end up with fresh water as a by-product. I am not making that up.

          • I don’t expect those folks to try building anything.

            Now, if Bill Gates, Vinod Khosla and Elon Musk decided to put a few hundred mil into a lark like that, I’m sure they’d actually get it built.  And it would have some serious cool, because that’s how Musk rolls.

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