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Power Earth Technology

Massive Solar Tower Planned For Arizona 407

inkscapee writes "It's simple, clean, low-maintenance, and cost-effective: using hot air on a large scale to generate electricity. No, this not a plan to use Congress to generate power, though that would certainly be an endless supply — EnviroMission will use air rising up a tall tower to generate 200 megawatts of electricity. The concept is simple: a giant greenhouse at the base of the tower warms the air. The warmed air rises through the tower and turns turbines, which generate electricity. The taller the tower, the faster the air moves, which increases power output. This structure will be a monster at over 2600 feet tall. It works in all weather, and if there is a feasible water source, food could be grown in the greenhouse."
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Massive Solar Tower Planned For Arizona

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  • Re:Decent idea. (Score:5, Insightful)

    by ColdWetDog ( 752185 ) on Monday July 25, 2011 @02:43PM (#36873936) Homepage
    Seems like a reasonable idea. The wikipedia article [] has more info than the TFA. There have been a couple of much smaller systems build world wide but little info on how well they work or stand up. I'm a little concerned about the 'limited maintenance' claim. It's a big structure in a hostile environment and has lots of moving parts. One wonders just how optimistic their financial spreadsheets are and how far they will diverge from reality.
  • by ByOhTek ( 1181381 ) on Monday July 25, 2011 @02:48PM (#36874008) Journal

    That's not the only myth they are tackling

    Put this tower in a hot desert area, where the daytime surface temperature sits at around 40 degrees Celsius (104 F), and add in the greenhouse effect and you've got a temperature under your collector somewhere around 80-90 degrees (176-194 F).

    It emits absolutely no pollution - the only emission is warm air at the top of the tower. In fact, because you're creating a greenhouse underneath, it actually turns out to be remarkably good for growing vegetation under there.

    Hmmm... What plants grow at those temperature?

    Maybe in cooler climes it can be used to grow stuff colder climes (or seasons), however at the locations where it'll be warmer and have more stable temperatures, it's gonna get awful damn windy... That means, amongst other things, rugged plants, lots of soil loss (going straight into the turbines or filters that will need to be replaced!) , and lot of moisture loss.

    It's looks like an interesting concept for an energy source, but as for green growing space... doubt it.

  • by ColdWetDog ( 752185 ) on Monday July 25, 2011 @02:52PM (#36874046) Homepage
    You grow plants at the periphery of the collector where it's warm, not hot and less windy. At least, that is the plan. Nearer to the turbines will serve as a training ground for Arrakis.
  • by ByOhTek ( 1181381 ) on Monday July 25, 2011 @02:55PM (#36874086) Journal

    the problem is, at those locations, it would only be useful in moderate climes anyway, that don't need greenhouses much.

    Also, if you are doing this in the desert, the problem is water, which the greenhouse will not serve to conserve, since there is a constant airflow.

  • by TehCable ( 1351775 ) on Monday July 25, 2011 @03:01PM (#36874182)

    The idea is interesting, but it seems to me that a substantial portion of the solar energy is going towards gravitational potential energy - that is, lifting tons of air mass hundreds of feet in the air.

    At some point, that air mass cools off, the air will want to drop back down towards the earth because of gravity. Seems like, in addition to generating 200MW on the 'exhaust' stack, they could build a second "cool air return" stack that generated power from the force of gravity pulling the cooled air back down to ground level?

    -1 parent. The exhaust air at the top of the tower is going to keep rising because it will still be hotter than the ambient air. The cold air that falls to offset the rising mass is called the atmosphere. It's big, it's going to be moving slower than the air you just used to spin a turbine, and it's not cost effective to try to make electricity from it until it enters the greenhouse, gets heated, and funnels into the turbines that are already in the design (the one place where air is moving fast in the whole design.

  • by necro81 ( 917438 ) on Monday July 25, 2011 @03:01PM (#36874186) Journal
    For this specific case: not many hurricanes in Arizona, nor in most every desert.

    More generally: site selection and engineering for the weather are surely taken into account before they break ground. The tower is freestanding and attached to the ground - the greenhouse is built around it, not the other way around. Even if the company glosses over stability in inclement weather, it should be caught in the permitting process. And even if it isn't accounted for during permitting, you can bet the insurers and underwriters will want good answers. Even so, this probably isn't ideal technology for, say, coastal Florida.
  • by GameboyRMH ( 1153867 ) <`gameboyrmh' `at' `'> on Monday July 25, 2011 @03:05PM (#36874238) Journal

    Taller doesn't necessarily mean more expensive. It's a big metal tube, not the same as a full building. It doesn't even need to be habitable. Structures of similar heights have been built for radio transmission you know.

  • by pla ( 258480 ) on Monday July 25, 2011 @03:12PM (#36874312) Journal
    This is a ridiculous idea. The only structure that is taller than 2600 ft is the Burj Khalifa (Burj Dubai), which is 2717 ft.

    The complexity of a giant hollow tube doesn't really compare well to an office and apartment building designed to safely hold tens of thousands of humans at a time.

    As for the cost, the average US nuclear power plant puts out very close to one gigawatt, and costs on the order of 6-9 billion dollars to build and another 30 billion in expenses over its lifetime. This tower has an estimated construction cost of 750 million dollars, and although I can't find any estimates of the maintenance cost, I'm going to go out on a limb here and say "a hell of a lot less than completely rebuilding it every 3 years of its spec'd lifetime".

    Sounds like at the very least a better-than-breakeven proposition vs nuclear, IMO - With no waste or risk of disaster.
  • Re:Decent idea. (Score:3, Insightful)

    by Anonymous Coward on Monday July 25, 2011 @03:22PM (#36874462)

    I'm kind of annoyed when people say "empty desert." The problem with this is a desert isn't empty and the animals that do live there need more area to hunt out edible plants and other creatures than more rain prone climates.

    Don't get the idea that I'm some cactus hugger, it's just I live in the arizona desert and people think it's all sand when there is quiet an abundant variety of life that can only be found in an area that's already relatively small.

  • by vlm ( 69642 ) on Monday July 25, 2011 @03:25PM (#36874496)

    Hmmm... What plants grow at those temperature?

    Locally mix in some cold air during the winter, it'll be nice.

    Kind of like asking, if my natural gas furnace burns a 2500 degree blue flame, how can I use it to keep my house at 72 degrees in the winter?

  • Re:Decent idea. (Score:5, Insightful)

    by cmiller173 ( 641510 ) on Monday July 25, 2011 @03:29PM (#36874536)
    Curious what the effect of launching a stream of hot air a half mile up will have on local weather patterns. Would suck big time if this upwelling of hot air caused a localized artificial high pressure zone that shifted the natural weather patterns. Just say'n
  • by Dunbal ( 464142 ) * on Monday July 25, 2011 @03:31PM (#36874580)

    It's the typical "we want a federal grant" spiel. It will cut your grass for you and cure cancer, as well as produce cheap reliable clean energy. Of course there's no logistical problems involved in keeping plants at the optimal temperature, watering them, etc. Nah, some dufus in a lab coat who has never seen a vegetable outside a supermarket said "hey, we could probably grow plants there too".

    Of course it would make a hell of a gnomon for a giant desert sundial. That would keep future archaeologists guessing for quite a while. Just to fuck everyone up they should align the doors with compass directions.

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