The Solar Tower

By on February 24, 2005

EnviroMission_tower.jpg

An Australian company, EnviroMission Limited, is blasting forward with plans to build a totally new type of clean power generating facility. Their concept consists of a monstrous tube that reaches 1000 meters (that’s 3280.84 feet) into the sky and is surrounded by a huge glass solar collector. The idea is for sunlight to hit the solar collector, warming the air below, which rises up the tower, driving a bunch of turbines to generate electricity. From the looks of their spiffy little video clip there are also plans for the tower to generate some tourism revenue as well, what with the tram taking passengers to the top. I’d sure pay for that!

It’s a great idea, what with the clean electricity that will be produced, but you’ve got to wonder what kind of unintended consequences might result from operating one, or several, of these puppies. The solar tower will basically be pumping huge volumes of air to places it wouldn’t ordinarily go. I’m no meteorologist, but it seems that doing something like that would tend to disrupt the way the weather works in the area surrounding the tower.

When I first heard of this project (through a Wired article) my first thought was of an article I read years ago about a similar concept. The earlier version also had a tall hollow tower, but instead of heating the air to make it go up, they planned to pump water up the tower and spray it as a mist into the tower at various heights. The mist would cool the air, which would cause it to descend down the tower driving wind turbines at the base. The plan was to locate the thing somewhere very dry, and the cooler, humidified air would make it possible for the land surrounding the tower to be used for farming. The article also cited opponents to the project that were concerned about the effects such a climate change in the vicinity of the tower would have in other areas. I never heard anything more about that project, so I’m guessing the critics got the best of the project.

And I’m guessing there are critics who will try to do the same with EnviroMission’s tower.

Gadgetopia

Comments

  1. I think this is called “scaremongering”. Hot air rises anyway; this is just using it to drive a turbine. The rest of the apparatus is simply a big funnel (as otherwise you’d need a really large, really lightweight turbine). Net air movement outside the site would be practically unaffected; anything which was “pumping huge volumes of air” would require energy, not generate it!

    The proof-of-concept was a working prototype operating between 1982 and 1989 near Manzanares in Spain; see below for some pictures: http://images.google.com/images?q=solar+chimney+manzanares

  2. How much hot air do the cooling towers of a nuclear reactor give off? I imagine it’s quite a bit. They don’t pump it that high into the atmosphere, but I’m skeptical it would have any weather effect.

  3. Check this out, I caught it the other night:

    http://www.pbs.org/saf/1506/segments/1506-3.htm

    “Alda also visits the roof of MIT in Cambridge, Mass, where an extraordinary device made of large triangular glass tubes soaks up sunlight and uses it to grow algae — algae that can later be turned into hydrogen. But Isaac Berzin’s invention not only converts sunshine (indirectly) to hydrogen; it also cleans up the smokestack gases from power plants. “

  4. “I think this is called “scaremongering”.”

    Is Anthony referring to this article as scaremongering, or the environmental impact concerns that likely brought down the earlier project? (That’s just a guess on my part; as I said, I have heard nothing more of it since that one article.) If it’s the former, I’d take issue with that. From some quick calculations I figure there will be around of 630,000 cubic feet of air rushing out the top of that thing every minute in a vertical column. That is something that doesn’t happen in nature. That said, I’m reasonably sure that the EnviroMission guys have done their homework on the climatic impact of the project, but I’m doubly sure that there will be some who will stand in the way of the Solar Tower because they believe it might have a negative impact on the local climate. I brought up the unintended consequences angle mainly because of the concerns aired in regard to the earlier project, not to frighten people into rising up against the EnviroMission project.

    I would also stick with my description of the Solar Tower as pumping huge volumes of air; 630,000 cubic feet is an awful lot of air to have rushing through that thing every minute. That does require energy, which comes from the solar heating at the base of the tower. The electricity generated is a byproduct of the heated air moving past the turbines as it heads up through the tower.

  5. The environmental impact is a cloud on the top of it and maybe some storms will begin at this point if the weather is appropiate. In the night it could make some drops fall, I think.

  6. Nothing “scary” is going to happen!

    Without a tower the sun heats the ground, the hot ground then heats the air. This warm, less dense air, then rises as whats commonly called thermals to anything from a couple of thousand feet to over 15 thousand feet.

    The thermals are what sail planes hang gliders and birds use to gain height.

    The height of the temperature inversion is where the thermal stops.

    If this activity did not happen then the air temperature at ground level would rapidly rise until it killed all life.

    All the tower does is effectively catch the thermal activity and feed it up the tube.

    There is no more energy added to the air surrounding the top of the tower. In fact there is less because some has been taken away as electricity

    Roy

  7. Yeah, this really is a gross misunderstanding. All its doing is concentrating the rising air from the 5000m diameter greenhouse into a 100 m diameter funnel. That air was going to rise anyway, at a much slower speed. So no net change.

  8. You don’t get thermals at night, but this thing “pumps” hot air up 24/7. Might have intesting weather effects when the outside temperature is cooler. On the plus side, if you had a network of solar towers you could have gliders flying round the clock …

  9. So basically the people who are saying it won’t have an impact think that whitewater rapids are the same as a calm river, just because they funnel the same quantity of water?

    Don’t get me wrong, I applaud the idea, and I think it’s marvelously ingenious. However, considering studies have shown that even the contrails of jets can change cloud cover over wide regions, shooting a column of heated air high into the atmosphere where the air is much cooler could cause a lot of potential weather disruption.

    I wonder if putting some sort of cap on the top of the tower to spread out the effect (so that the heated effluent is more broadly distributed, like a spray bottle) might lessen the impact. Alternately, if there was some way to set the turbines so that as much of the energy as possible is transferred prior to emission.

    Possibly some sort of heat exchange system could be put into place, to transfer any remaining heat back down to the base to both increase capacity and lessen the impact.

    One would also think humidity gradations between the ground-level air and the release area may play a role in weather havoc, in addition to altering the generation potential of the facility (since humid air takes more energy to heat)

  10. I’m amazed at how concerned many are about something they know absolutely nothing about. I see no obvious reason why warm air rising over a desert would strike anyone as unusual. What do you think happens when they build a large asphalt parking lot ? You get updrafts. Glider pilots get from here to there by latching on to rising warm air current to gain altitude and them gliding to the next one. While it’s always a good idea to consider possible negative side effects, it’s also obvious that no one around here is qualified to speak authoritatively on the subject and that there is no obvious reason to expect any side effects from what seems a very benign activity. In other words, it’s up to those who worry to produce some valid evidence (and I don’t mean logical arguments, but empirical eveidence) that the process is not as benign as it seems. I very very seriously doubt that anyone can. Warm air currents even higher than 3300 ft are encounterd by glider pilots all the time, everywhere on Earth, from a variety of sources.

  11. One of the main goals of these towers is obviously to produce clean electricity, ie without production of greenhouse gases, the goal being to reduce the impact electricity generation has on global climate change. I would be most disappointed if arguments about climate change were to delay/stop what is a project with such amazing potential. Now I’m no meteorologist, but I think it highly unlikely there would be any significant local climate change due to the tower, for all the reasons mentioned in previous posts. Hypothetically, if there were to be any effects, I fail to see how this would affect the viability of the project. One must remember they are planning to build these towers in arid/semi-arid sites (The area of Australia where the prototype is being built has been badly dought affected for the best part of a decade, and probably more). Therefore it would be difficult for any local climate change to make things any drier then they already are. If the column of rising air did create a storm or two, I hardly think the locals would complain about the potential rain.
    In my view, the (very) outside change of significant local climate change is far, far outweighed by the overwhelming need to develop alternatives to coal fired plants. If global climate change is to continue unchecked, most simulations show eastern australia (and other parts of the world) becoming increasingly arid, making any climate change from these chimneys insignificant.

  12. According to my calculations to supply the energy needs for the households in the US state of North Carolina, you would need to cover 1/4 of the state. Also the 90 degree temperatures would eliminate most of the native fauna and flora below the skirt. Maybe in the Gobi desert this would not be as big a concern. From an aesthetic point of view, I don’t think looking at 3000 foot towers would be appealing.

  13. An economic drawback of Solar Chimney Power Plants (SCPP) is the low overall conversion efficiency from solar energy to electricity, which negatively effect on the levelized solar electricity cost. Continuous improvement of the concept has involved the investigation of methods to increase power station efficiency and capacity. From this standpoint a new approach to prospective SCPP includes the combining of the following grid connected technologies: Hybrid Geothermal / Solar Chimney Power Plant and Hybrid Geothermal / photoVoltaic (PV) / Solar Chimney Power Plant . They are based on thermal conversion, which allows hybrid operation with both solar radiation and low temperature geothermal to continue generating electricity even when sunlight is not available. Furthermore, new schemes of Hybrid SCPP would fully exploit the potential of the geothermal/solar combination, based on the following principles:

    ─ supply solar heat to the transparent solar PV/T arrays , to achieve the highest possible conversion efficiency,

    ─ supply low temperature geothermal heat to the collector zone, to achieve the highest possible geothermal contribution,

    ─ hybrid geothermal/solar operation, to provide dispatchable full capacity at sunny and cloudy periods of operation, without solar-specific restrictions on the plant?s operation.

    This is a major advantage since it enables operation according to the actual demand for electricity, without limitation to sunlight hours only and considerably improves SCPP ability to compete with conventional power plants.

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