Discussion on:

26,250-feet solar power supertower to rise over Arizona (video)

How about 2,625 feet. That would make it just under the Dubai tower's 2,716.5 feet. Nasty things those little decimals.

On a 2,600 foot tower could bands of solar collectors at the 1,000-foot level and increments above that reheat the rising air and improve the updraft?

They might get the effect in a very cost effective manner by simply darkening the concrete in bands to improve solar heat absorption at fixed altitudes.

In the morning those bands would get sunlight first to warm the top of the tower. Which theoretically could slow start the updraft before the main panel grid is even in the sun.

I know Arizona is a dry place, but any moisture that is thrust up like that will form Nimbus type clouds.

While the generation technology will be squeeky clean, the construction technology is less so: Making concrete is a significant contributor to greenhouse gas emissions, as is making glass.

Why not add turbines all the way up the stack? At least do so to the point that it does not interfere with the draft. The current design seems like a waste to me.

$750 million seems like a lowball estimate for the cost, and 80 years sounds awfully optimistic for end of life, but it would then come to just over $5 per month per home for electricity, so even if the numbers are off, it still sounds feasible.

Why not hang vertical turbines on the outside? There are some nice designs built to be installed on the sides of skyscrapers.

Wind turbines on the outside could boost daytime production and help to even out the 27/7 power production instead of having it drop to 0 once the sun goes down.

The white painted top is what got me thinking it should be a dark color to increase heat retention and aid the updraft.

It does seem like a lot of wasted space if it is not contributing to the efficiency of the design.

Mammoth Solar Tower Structure. This is an indication of the big solar projects in the offing.

Dr.A.Jagadeesh Nellore(AP),India
Wind Energy Expert
E-mail: anumakonda.jagadeesh@gmail.com

We have TOXIC LEVELS of ARSENIC III, LEAD, URANIUM, ETC in our drinking water NOW, causing CANCER CLUSTERS in GEORGIA. My son, our 2 dogs & I are a "Cluster". We also have 3 proposed Coal Plants on "several persons'" agendas. 9/10's of GA's surface area is Watershed for our aquifers. PLEASE HELP STOP ALL THREE POISONOUS COAL PLANTS! The EPA, CDC, Health Dept, & other GOVT AGENCIES in GA are aware of the POISONS in our WATER. www.caringbridge.org/visit/benmcmahan

We've seen our electric rates increase by over 30% in less than 30 months here in central Missouri. Now I'd gladly pay an extra $5 or more a month if we were building something like this. Instead all we see is the executives get massive raises every single time the utility company goes before the utility commission for another rate hike. How about us spending more money on something that gives us more. Brilliant design that could work. If LA needs a dozen of the things, then so be it. There's money all over the place, it's just how and where it's being spent that makes a sane person go half nuts. We make love with the oil companies and pay whatever they charge yet when a person tries to do something good for our mother earth, it's called a waste. I care about tomorrow. Now if only more would.

This was in a sci-fi story 'Waaaayy back there somewhere -- but in the story, the "towers" were actually helium-levitated tubes of plastic floated over a horizontally-spinning turbine at the bottom.

They were meant to channel heated ground air up from the solar-heated prairie, which would, as in this design, generate its own pull on the way up.

But in point of fact, such a design would not work, simply because the air outside the tube would rise faster than the air inside of it, due to the tube's constriction. Thus a tube would never get the flow started in the first place.

The missing piece that makes this design work, is the large solar heating space at the bottom. That should generate enough heat to get the flow started up the tube.

What can I say? Sci-Fi doesn't ALWAYS anticipate actual science.

But note: I still see no reason why a flexible, dirigible-floated tube wouldn't work perfectly well for this design; and that adaptation might save these builders a LOT of money.

Try reading [assuming you can find a copy] of Genius Unlimited by John T Phillifent. [one of John Rackam's pen-names] from 1972- like the 'Dragon Kiln' {or furnace?} in one of the early books of Leo Frankowski's Cross-Time Engineer's series, they built the updraft power stacks up the side of a mountain rather than free-standing.

that group wasn't looking for max efficiency, but minimum impact on a fragile ecology.

it'd be lots harder to blow into a pretzel than a gas-lfted flex stack, too.

This is why lay people should not (as a rule) second-guess scientists and engineers, who spend their whole lives studying their subjects.

Trust me, a competent design WILL use all of the generated force that it can.

But rather than put "additional" turbines all the way up the stack, where access would be not only difficult but also perhaps dangerous (height AND weight), the increased resistance would be put where it is now: at the bottom. Up the stack is highly unnecessary.

Remember: the tower is sealed to leakage (or it would not work), therefore one can take ALL of the energy one is going to take, at either end of the tube. Generators can be designed to use MOST of the available energy, leaving only enough lift in the tube to move the air fast enough to generate power. This turbine will not be "off the shelf," but will be designed to use every bit of energy available, leaving only enough in the column of air to keep the flow moving at an adequate generation speed. Too slow, and the turbines will stall out.

They have already optimized the turbines and blades, or they wouldn't have achieved 80 % efficiency.

My point was to modify the tower to generate power when the sun was not shining.

Right now the tower design would run at 60% efficiency during the day. What is that efficiency after dark when the tower is putting out 0 power? How does that impact the towers efficiency when measured over a 24/7 period?

If you are going to build a 2,600-foot tower that will obviously see usable wind at the upper altitudes wouldnt it make sense to capture some of that external wind?

Even if the turbines added provide just enough to power the mandatory hazard lights required by structures that large it would save on tapping the grid at night.

To have a 2,600-foot tower that fails to generate power after the sun goes down is a huge waste. External turbines capturing the winds common above 1,000 feet would greatly improve the towers 24/7 efficiency. There are already turbine designs in place for skyscrapers that could be easily modified for use on this tower.

To follow-up on the other thought. The darkened area at the top of the tower could warm the stack and maintain the heated air to the top. You do not want to have rising air cooling too much and potentially causing down drafts, which would hurt efficiency.

To my knowledge no one has ever built a chimney this tall, but at those altitudes the stack would be subject to cooling breezes. The potential for back drafts causing air flow stall at the top of the stack increases with the height of the stack.

A previous tower design using internal turbines actually used this cool air falling effect to generate power. The naturally cooling air was to be assisted by spraying water at the top of the tower. It was suggested to use the water for this in lieu of conventional irrigation because it would generate power and increase natural air moisture levels downwind of the tower.

During nightime, the temperature differential may be reduced, but it certainly doesn't go to zero. It's colder up there at the top. My main concern would be the structural stability of such a tall object, and its potential vulnerability to extreme weather, accidents or intentional destruction. Must the tower be made of glass, or could it be a more conventional material like corrugated steel or aluminum panels bolted to a steel frame? It's a very elegant concept. But in a world where neighbors don't want to live near giant windmills, nimbyism might be a serious problem.

With the way perth development is going build it outside Perth in WA.

Deserts are very dusty climates, and it is not obvious to me that dust sucked into the turbines will never become problamatic. I found a reference to a prior prototype which says, "The prototype for the tower operated for seven years in Manzanares Spain and consistently generated 50kW output of green energy." Why was this ended after only seven years? Did it get clogged with dust, or did it just run out of money?

Good topic for a follow-up article.

RetiredEngineer

I always question the reliability of Wikipedia, but on this power option there is some information about concept projects. The tower in Spain supposedly collapsed during a storm because of guy wire corrosion.

http://en.wikipedia.org/wiki/Solar_updraft_tower

Great!!! thanks for sharing this information to us!
sesli chat sesli sohbet

EnviroMission have being promising to build a 1,000m tower "next year" for this project, in Victoria (Australia), just south of the Murray River, for the past eight or more years, but they never got started. Construction costs currently are probably a fair bit cheaper in the US than AUS, but this has not always been the case.
There was never any explanation for the continuous postponements. I have seen the publicity pictures before ...

The desert tortoise simply won't permit it!

This may be low-tech enough to work. I checked out the Wikipedia link that @HatesIdiots posted. The article layed out some very good design improvements and alternatives.

The power plant requires a lot of land, but making that same area perform double-duty would significantly improve benefits. The suggestion of a solar vortex seems like a particularly good way to boost the velocity and volume of the generated updraft.

Replacing the glass roof with a tough polymer like PETE would reduce the construction cost and it would support recycling, as well. Adding PV panels under the roof would produce more renewable energy, especially if the panels were cooled by a thermal-absorbing material as simple as water. Using a thermal mass as well would allow operation well into the night, when the larger temperature difference would increase output. Adding an airfoil to the top of the tower would take advantage of upper-level winds to decrease the air pressure and improve the updraft.

The height of the tower, though, would pose a major hazard to aviation. I would also be concerned about the durability of a free-standing structure that tall.

On the other hand, maybe putting an amusement park ride at the top and charging people a lot of money for the thrill could help the ROI (I'm referring to the Stratosphere Casino in Las Vegas). Heck, maybe Las Vegas is just the right place for it. We could use the chimney to shuffle lotto balls, too.