JUN 12

Solar towers are again getting some notice. According to recent news, a company called Clean Wind Energy, Inc. is trying to build a 3,000 foot (914 meters) tall tower to produce electricity. When the tower is operational, the company expects to have, on an hourly basis, "1,100 to 1,500 megawatt hours available for sale to the power grid."

Solar power towers are one of the more unusual concepts we've come across at EcoGeek. More properly, we should be calling them something like 'thermal chimney towers' to differentiate them from the solar towers which are targets for fields of solar reflectors.

To further complicate the matter, there are two types of solar chimney towers: updraft and downdraft. Updraft towers require a large area covered with transparent material to heat the air at the base of the tower in order to make it rise through the chimney. Downdraft towers pump water to the top of the tower where it is sprayed as a fine mist to cool the air and induce it to fall. In both cases, wind turbines at the base of the tower are turned by the moving air to produce electricity.

The tower that Clean Wind Energy is proposing is of the downdraft type, which may be problematic in the American desert southwest, where water is already scarce. Treehugger's article on the project also notes one of the major drawbacks to this kind of power generator: "Of course, there's the problem of dedicating large amounts of water in a desert city to the tower, and the energy required to send it 3,000 feet up. One third of the energy produced by the tower goes to that pumping."

Several years ago, we first noted that Enviromission, an Australian company with an updraft tower design, was trying to get their first solar power tower built in Arizona. That company found Arizona more conducive to their business model than building a tower in the Australian desert, and their project also seems to be moving slowly forward. Whether either one of these towers (or both) gets built remains to be seen.

via: Treehugger

Comments (11)

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Odd concept
written by A2H, June 12, 2012

Thanks for reporting on it; what a weird concept! I surely hope it won't be built. Seems like somebody dreamed this up without fully understanding the implications and now is too stubborn (full off it?) to back down, once it became clear how unsustainable it really is.

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Can it Compete?
written by Ronald Brak, June 13, 2012

If it ran off sea water there are low humidity coastal areas in the world where this could be used if the cost was low enough. The question is can it compete with other low emission sources of electricity?

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water may not be a problem
written by Tom Konrad, June 13, 2012

In my review of CWET's technology, the water used may not be such a problem. Much of the water can be recovered as condensation at the bottom of the tower, and even salt water can be used at the top, meaning that there may even be a net gain in useful desalinated water.

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very poor view of the project
written by wrr, June 13, 2012

This article offers a very poor view of the project and without all the facts it presents a rather murky picture. The location of the project is brillant, hot dry air, near major electrical transmission lines and most importantly, near a good source of water. Clearly the author has not dug into the facts. Sea water is within pumpable distance and by using sea water the process will produce desalinated water at the bottom of the tower that can be used in an area that badly needs a source of clean fresh water.

Other omissions in this article are that the concept is hardly a new one, it's been around for decades. The project leaders are two renowned scientist that know what they are doing. that the Arizona town of San Louis has passed the zoning for not one but two of these towers. That three of the worlds biggest builders will be bidding on this project, think tall towers in Dubai.

All of this information is readily available, why this author choose to presents this in the light that it is defies explanation.

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Please respond/follow-up or edit article
written by Voltair, June 13, 2012

Very interesting responses from wrr and Tom Konrad. This article and the Treehugger article used as a source left me with the impression that the project was dubious, at best. Wrr/Tom Konrad's feedback gives the impression that there is a lot of potential! I certainly want to know more.

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Re: Voltair
written by Tom Konrad, June 15, 2012

Here's the article I wrote about CWET last year:
http://www.altenergystocks.com/archives/2011/09/a_new_way_to_skin_the_renewable_energy_cat.html

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So, what happens to the salt?
written by Bob, June 22, 2012

The baloney alarms should be going off here.

It won't use salt water. When you cool air with water, the heat goes into the phase change when the water turns to gas. The dissolved minerals, however, won't change. They'll come out as particulates and they will cling to everything they touch. They will also fall down that big hole in the center and end up in the water. You will start with salt water, end up with somewhat less salty water and very corrosive salt crusted all over everything. How would you like the job of cleaning crusted salt off walls nearly a kilometer tall? Maybe the honchos are used to success, but if so, they're going to get a new experience with this project.

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Celebrate diversity
written by Lnr, June 25, 2012

Good report. Interesting idea. The more I read about clean energy solutions the more it strikes me that no one source can be all things to all situations. This may seem obvious but I don't think it gets said enough when talking about clean energy.
Variety is the spice of life and our reliance on fossil fuels should surely have shown us that getting all our energy from the once source is bad practice. The more methods we investigate for generating electricity the more we can improve and adapt them for the environment we happen to be in.

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What a great way to cool a city
written by Aaran, July 30, 2012

I am assuming that air that falls from 1000m altitude would be significantly cooler than that on ground level. If this was built in a city like Dubai the tall buildings could help to protect the tower from strong wind forces, the cool ari would flow out at ground level cooling the surrounding area.

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...
written by Bradley, October 18, 2012

Wouldn't there be an easy way to collect natural condensation from that height and simply use that instead of pumping water up? I know I've seen an article on here about a wind turbine that could condense water vapor.

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written by Michael Hertel, November 10, 2012

This will not produce fresh water from salt water the salt will be in the air moving down with the air stream if salt water is used.
Since humid air is lighter than dry air the increase in humidity reduces the density of the air even though it does cool it when it evaporates. If you can get it cool enough you still get an increase in density overall.

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