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Massive Solar Tower Planned For Arizona
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."
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.
Faster! Faster! Faster would be better!
lots of moving parts
Maybe in absolute terms, but virtually any other means of electrical power generation has more. The only moving parts here are the turbines. Not only do we have plenty of experience with running turbines (since every other power source uses them), but they should all be independent from one another, so a failure of one doesn't lead to damage or require a shutdown, it just means you're putting out a little less power.
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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.
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They aren't "lifting tons of air mass" against gravity. Gravity pushing down on the surrounding air is what is pushing the air up in the first place. This tower is a way to focus that downward push of cool air onto a narrow tube of hot air that then floats up and runs the turbines. This isn't any different than boiling small amounts of water at the bottom of a lake. The bubbles will rise quickly and that energy could be harnessed, but it would be pretty useless to try and harness the energy of the resulting water vapour eventually drifting back to the bottom of the lake.
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.
Sigh... I have a pen, anyone have an envelope?
The tower is rated for 200 MW, with an estimated utilization of 60%. So the average power output is about 120 MW.
Wholesale electricity prices in the United States are 40-100 $ / MWhr. This should be able to provide most of its power during peak usage, which is great from a business model. Plus they can command a bit of a premium from the California ISO because it is renewable, and California has a 33% renewable mandate. Let's assume 60 $/MWhr.
In each year there are 24 * 365 = 8760 hours. So the company's annual revenue should be in the ballpark of $65 M/yr.
The estimated cost to build the thing is $750M, and their estimated payback period is 11 years. That doesn't quite jive with the numbers I've come up with, and doesn't take into account net-present-value calculations, financing costs, operating expenses, etc. But, even so, you should certainly be able to pay for the thing over its many-decades-long lifetime.