[The_Virginian]

http://www.enviromission.com.au/index1.htm This company "enviromission" is planing to put a huge tower in Austrailia to provide Solar energy from convection currents!

Now, I know there has got to be some debunking or other criticisims that this company does not tell us about.Is the science behind the figures for power generation realistic? Or is it part dfantasy to attract investors?

Diabolos any comments?

[smiley]

Maybe they have made the same mistake. In the prototype section they state that the prototype generates 50 kw.

$this->bbcode_second_pass_quote('', 'T')he plant operated for seven years between 1982 and 1989, and consistently generated 50kW output of green energy

[MarkR]

The science appears to be sound, as there is a prototype of this design, and it does work.

However, some quick back of envelope calculations suggest that the efficiency is pitiful compared to conventional solar techniques - and OMG the size of that thing.

Buried deep within the website, they state that the canopy area is 3,800 hectares. That's *4 miles* in diameter! Then there's the tower thing in the middle - 1000 metres.

Just how do they plan to build that, and how much will it cost?

Is it worth it for an efficiency of 0.4%?

[clv101]

1km high. The efficiency doesn't really matter when the fuel is free. The only calculations that need to be done are capital costs.

The only other fear is EROEI - concrete is energy expensive, even before you drag is 1000m in the air.

It's a nice idea in theory but many challenges exist - construction, keeping the glass, plastic clean, capital expense...

[The_Virginian]

If you go to the "Company Anouncements, they say they will use 3,800 hectares for green houses, this is out of 10,000 hetre solar tower site.

I assume the inner rings of the glass "heater" would be "too hot", thus only using the outer rings.

$this->bbcode_second_pass_quote('', 'M')aybe they have made the same mistake. In the prototype section they state that the prototype generates 50 kw

[The_Virginian]

$this->bbcode_second_pass_quote('', 'k')eeping the glass, plastic clean

[smiley]

Another thing I don't understand. If you want to capture heat you want to capture radiation right along the spectrum. That means you need to minimise reflection by creating an ideal black body.

I don't know how a silvery shiny thing fits in that concept

[clv101]

We're not talking about absorbing heat like a black body - this uses the green house effect literally, with food growing inside it (which has the added benefit of making the air damp, heavier and capable of doing more work through the turbines). I think the principles of black body absorption are very different to the green house effect.

The other channange is to keep it going overnight - thing the world largest storage heater to maintain the temperature gradient throughout the night.

[The_Virginian]

As to the construction costs and enginering:

The newly planed "Freedom" Tower in NY will be 1776 ft in hight (counting the Spire) and counting the spire, the tallest building in the world.


http://www.wordiq.com/definition/Freedom_Tower


It will cost 1.5-2 billion USD (and we know how over-runs can be!)

So to biuld a 1 KM Structure in the air must be tremendously expensive

On a side note the "Feeedom" tower will have wind turbines to generate a whopping 20% of the buildings energy needs.

How nice, 20% runs up to the estimate for total practical wind generated elecricity in the US as a renewable recource.

[The_Virginian]

$this->bbcode_second_pass_quote('', 'k')eep it going overnight

[clv101]

Regarding efficiency, I think they expect the 1km tower to be 1.5%. The higher the tower the greater the efficiency due to increased pressure difference. They have looked at a storage heater approach to keep the thing going through the night, it's not included in current plans but could help. Anyway – peak temperature power output occurs a few hours after the hottest part of the day, nicely corresponding with peak demand and in the night/early hours, demand is so low that other base load producers will be fine.

700,000 cubic metres of high grade concrete – it's gotta be good, and it's gotta be local materials so a lot of materials testing will be needed.

Total capital costs are estimated at ~US$ 720million. But think of the alternative revenue sources – TEG Heure sundial? Viagra Tower? Tourist attraction to a lofty viewing gallery?

In short it's an interesting project but doesn't really fit in with the scaling down, local idea. Mega projects seldom deliver on promises.

[The_Virginian]

And contrast this with the other famous "mega project the thee gorges Dam"

http://www.cbc.ca/news/features/threego ... facts.html

Here's what happnes when you don't cool the concrete correctly (ice or water pipes as some comments suggest) IT cracks, badly:

http://www.freerepublic.com/focus/f-news/920339/posts

So 1 Km of pure concrete? Up up and away?

[MarkR]

Well, it's cheaper than PV.

But at such a high capital cost, I doubt that it could be remotely cost effective without enormous subsidy.

What about running costs - there's a whole lot of real estate there than will need inspection/cleaning and maintenance.

I wonder what sort of electricity cost they anticipate in the end - I can't imagine any less than US$0.10-0.15/kWh being break-even.

[Devil]

The Oz project, as I heard it, was a 1 km high guyed steel chimney and 27 km2 of greenhouses containing enormous black finned water reservoirs. These served to a) limit the temperature to a tad over 100°C, so that the mechanics of the turbines and the whole caboodle were simplified (for maintenance) and b) ensure sufficient heat storage that it worked 24/7/52.

I'll start a separate thread on 3 Gorges.

[Guest]

$this->bbcode_second_pass_quote('', 'T')he Oz project, as I heard it, was a 1 km high guyed steel chimney and 27 km2 of greenhouses containing enormous black finned water reservoirs.

[Ender]

$this->bbcode_second_pass_quote('smiley', '
') It is hard to estimate the size of the thing from the picture, but it looks pretty big. I would say that it is at least 100m high with a 50 m radius

If that is the case then I wonder how big the 200 MW monolith must be.

[Ender]

$this->bbcode_second_pass_quote('The_Virginian', ' ')Why didn't I think of that. No sun = no Heat = no Juice at night.

[Antimatter]

http://www.wired.com/news/technology/0,1282,66694-2,00.html?tw=wn_story_page_next1
$this->bbcode_second_pass_quote('', 'T')he quest for a new form of green energy has taken a significant step with the purchase of a 25,000-acre sheep farm in the Australian outback. The huge alternative energy project isn't driven by manure, but by a 1-kilometer-high thermal power station called the Solar Tower.

Announced several years ago, the 3,280-foot Solar Tower is one of the most ambitious alternative energy projects on the planet: a renewable energy plant that pumps out the same power as a small reactor but is totally safe. If built, it will be nearly double the height of the world's tallest structure, the CN Tower in Canada.

The Solar Tower is hollow in the middle like a chimney. At its base is a solar collector -- a 25,000-acre, transparent circular skirt. The air under the collector is heated by the sun and funneled up the chimney by convection -- hot air rises. As it rises, the air accelerates to 35 mph, driving 32 wind turbines inside the tower, which generate electricity much like conventional wind farms.

But the Solar Tower has a major advantage over wind farms and solar generators: It can operate with no wind, and 24 hours a day. Thanks to banks of solar cells, the tower stores heat during the day, allowing it to produce electricity continuously.

[nocar]

I do not understand how it is supposed to yield pour 24 hrs a day when it is solar powered. Can someone please explain?
nocar

[nocar]

I meant power of course.
nocar