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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."
But too bad - the greenhouse effect is a myth, as we all know.
The mammoth 800-plus meter (2625 ft) tall tower will instantly become one of the world's tallest buildings.
Compensating for something there, Arizona?
"None can love freedom heartily, but good men; the rest love not freedom, but license." --John Milton
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!
FTA:
The output has already been pre-sold - the Southern California Public Power Authority recently signed a 30-year power purchase agreement with EnviroMission that will effectively allow the tower to provide enough energy for an estimated 150,000 US homes. Financial modelling projects that the tower will pay off its purchase price in just 11 years - and the engineering team are shooting for a structure that will stand for 80 years or more.
Every time I start to have faith in humanity, I ruin it by driving to work between 7 and 8 am.
It's in Arizona, what do they have to lose? :-P
"When information is power, privacy is freedom" - Jah-Wren Ryel
This is a ridiculous idea. The only structure that is taller than 2600 ft is the Burj Khalifa (Burj Dubai), which is 2717 ft.
http://en.wikipedia.org/wiki/List_of_tallest_structures_in_the_world
The idea that we would build the 2nd tallest structure in the world for 200 MW is ridiculous. This doesn't even come CLOSE to being a top producer of energy per power plant. The top 10 power plants in the world all produce more than 6000 MW. Even the largest biofuel, geothermal and tidal plants currently exceed 200MW.
http://en.wikipedia.org/wiki/List_of_largest_power_stations_in_the_world
-molo
Using your sig line to advertise for friends is lame.
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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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.
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.
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.
I know this is in a desert, but it will rain on rare occasions; what will they do with the water that falls on the structure? I imagine it would not be worth while to collect it and transport it somewhere, since it will be so rare. I feel like they probably have considered this, and I just want to know what decision they came to. Put it all in a big gutter, feed it into a huge sump (or a lot of little ones), or what? Also, what about dust buildup - will it get cleared by wind (like the Mars rovers' solar panels) or will someone have to go up there with a giant squeegee to clean it off every now and then? Again, I bet they have thought of it, and I am curious about what ideas they came up with. Maybe they only clean it when it rains? Maybe every time they do clean it, it rains the next day? Who knows?
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.
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.
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
When oil is ten times the price it is today (give it, oh, a decade tops) then anything will look cheap.
Imagine we'd only just discovered oil - we'd probably be shouting down some lunatic scheme to build a huge floating platform, tow it out into deep, windy, wavy waters and then drill several kilometers into poorly understood geology to tap a pressurised well of highly flammable oil and explosive gas.
In engineering and financial terms, this is easy.
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At those temperatures, we can just put pigs in the bottom to get bacon strips.
Yep, they cook then get drawn into the turbine, it'll be raining bacon strips for mile downwind.
It's kind of like putting a hose in a tub, running it out the window and sucking on the hose a bit to get the water started.
The hot air raising up the tube creates a vacuum that pulls in more cold air around the base which is heated by the sun through the glass. The higher it goes, the more air it needs to pull in the bottom. If you cut the tube off, the vacuum is reduced because the hot air is not being used fully and being released too soon.
Every time I start to have faith in humanity, I ruin it by driving to work between 7 and 8 am.
I get it... turbine generators have really good efficiency and we've refined their use for over a century. But it seems to me that every worth-while method of power production uses them...
Solar Cells, and Lightning Rods seem to be the only methods I can think of that produce electricity without the use a turbine/generator combo but neither are viable for wide spread use. It seems to me that we'd do well to invest in methods of converting heat directly into electricity (giant Peltiers?) without the use of a turbine/generator. I would think doing so would theoretically make a number of our existing methods that much more efficient and perhaps open the door for other methods of power production.
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