Talk:Solar updraft tower/Archive 2

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I'd suggest not to move discussions there until they have run their course, and any relevant question has been answered. Thanks --Singkong2005 ^t_c 02:28, 17 July 2006 (UTC)

Contents 1 Intellectual property concerns 2 Question about this article 3 Self-promotion? 4 Physics 5 Production capacity 6 Merge Proposal 7 Rename 8 Byproducts 8.1 Byproducts 9 Some useful links 10 Solar Tower Buronga 10.1 Solar Tower Buronga 11 Solar updraft tower (from user talk:ScottDavis) 12 Carnot engine 13 Betz limit 14 Atmospheric winds 15 Conversion Rate of Solar Energy to Electrical Energy 16 move to Adaptations section 17 Farmland under the canopy? 18 Neutrality 19 Mediation 20 floating chimney 21 Rename (revisited) 21.1 Reasoning 21.2 Proposal to make Solar tower a disambiguation page 22 Financial hurdles 22.1 Risk 22.2 The bottom-line 22.3 Environmental impact

[edit] Intellectual property concerns

EnviroMission Ltd Australia owns the exclusive license to German designed Solar Tower technology in Australia while H. Alfred Goolsbee owns the Japanese trademark and service mark "Solar Tower". H. Alfred Goolsbee also retains certain rights to the use of the words "Solar Tower" in the United States.

I moved this remark about Intellectual property concerns from the article to here. If there are really "Intellectual property concerns" then the article doesn't not belong in Wikipedia at all, but in a bank vault :-). But I think it is BS: The ancient Babylonians had already "Solar Towers". and so did the Aztecs. JdH 06:46, 9 June 2006 (UTC)

Discussion of intellectual property and trademarks are valid topics. They need to be brought back out in the open. This should be brought back onto the page ... perhaps with a link so we can see some evidence for truth.--Flexme 22:45, 12 July 2006 (UTC)

[edit] Question about this article

I've been working on cleaning up Solar Tower, which was riddled with trademark symbols and likely advertisements for a specific company that develops solar towers. I'm concerned that the article describes generic solar chimneys, but presents them as the property of a company. This company goes by the names "Enviromission," "AEldwood," "Solar Mission," "Opensource Energy," among others. The company owns the trademark for the term "Solar Tower," note the capitalization in both the term and the Wikipedia article. An anonymous user, who I believe is affiliated with Enviromission, recently moved the article from Solar chimney, a term which I believe is unencumbered. The user added numerous links to the company, and a confusing note about the trademark status. Personally I think it's odd that someone invoking the spirit of open source would care so much about protecting their IP, but that's beside the point.

What do we do about this article? I think all generic information should be moved back to Solar chimney, and Solar Tower should focus on the activities of the company which owns that trademark. Right now we are muddling the technology with a specific product. It's like if Operating system redirected to Microsoft Windows. Thoughts? Also posted on the Village Pump. Rhobite 14:02, Oct 12, 2004 (UTC)

Agree. To have the generic term solar chimney redirect to Solar Tower, a registered trademark (allegedly), is completely inappropiate. Solar Tower should be stubified, removing the promotional material and documenting what facts we can verify. The generic stuff should all go to solar chimney, the concept has been around for many years and is used for cooling amd ventilation, although not successfully for power generation AFAIK.

The redirect from solar tower is just as bad, this should be an article describing the astronomical apparatus. I might fix this myself.

I'm not sure what the best thing is so far as the histories is concerned. My attitude is generally when in doubt leave them where they are, see talk:boyfriend, but if you can see a good way to untangle them go for it. I doubt that anyone will want to delete Solar Tower, so cross that bridge if and when. Andrewa 09:24, 13 Oct 2004 (UTC)

I've now put stubs at solar chimney and solar tower, both with links here. Andrewa 09:51, 13 Oct 2004 (UTC)

Thanks Andrew, I think that's what we need here. I won't be able to work on it today but I'll move the generic content out of Solar Tower when I get a chance. Agree re: the edit history, if there hadn't been any edits after the cut-and-paste rename it would be easy, but for now I say leave it. Rhobite 13:28, Oct 13, 2004 (UTC)

• How about a disambiguation page that explains the difference between "solar tower" and "solar chimney," and also points to the astronomical thingy.
  • Please sign your posts on talk pages, even if you're not signed on. TIA. Andrewa 00:20, 8 October 2005 (UTC)

I've been reading this discussion and I'm still a bit confused why Solar Tower has to remain a separate article from Solar chimney. They appear to be the exact same thing. The only difference is that the former is a trademark and the latter is a generic name. Why can't we just merge Solar Tower as a section in Solar chimney? Solarusdude 18:52, 30 September 2005 (UTC)

That sounds sensible to me. Also, solar power tower should probably become a disambiguation page linking to solar tower and somewhere else for the other concept. Andrewa 22:26, 7 October 2005 (UTC)

Add to that the confusion about the Energy towers. The appropriate thing to do would be to compare the Schlaich approach with that of Zaslavsky, discuss advantages/disadvantages of the two schemes; merge the Solar tower/Solar Chimney/Energy towers sections, including a careful discussion of physics and commercial impact. What about the energy transport issue from remote desert locations where these things have to be built? How is that going to impact the commercial viability? What about the environmental impact? The environmental impact of these things must be huge, yet it is not addressed at all in this section. For the Zaslavsky approach we have a reference to a critical review of that issue, but not for the Schlaich approach. JDH 10:46, 21 January 2006

Energy Towers seems the most generic term, and solar towers would be a subclass, though it's hard to imagine any energy tower other than solar based - wind based, tide based, what based? So energy towers might as well be ignored and just deal with the most generic solar tower name. Solar towers come in different kinds - concentrating mirror based on molten salt/Stirling engine design, or chimney based, either updraft with a huge(30 km) glasshouse collector, or downdraft based, without a collector but needing a water supply + pumping energy. So I recommend having a solar tower/energy tower disambiguation page, that points to concentrating thermal towers, or to solar chimneys, and has a remark on the solar tower trademark part too. Sillybilly 14:58, 21 January 2006 (UTC)

Actually, wind turbines are sometimes referred to as wind towers, and people actually point out that increasing the height of those wind towers increases the yield of those things, as it does for the solar chimney. Therefore one might argue that the concept of "energy towers" comprises not only the solar towers of different breeds but the wind tower as well.

Still, I find these sections murky at best. What about having a subsection on "energy towers" under Renewable energy? JDH 16:22, 21 January 2006

[edit] Self-promotion?

This article appears to be written by H. Alfred Goolsbee, User:Proton44. This would explain the promotion of http://wiki.solartower.com, which despite its amateurish appearance is listed as the first external link, and also the emphasis given to enviromission.com and SolarMission over other promoters and implementors of this idea. -- Tim Starling 05:47, Oct 15, 2004 (UTC)

Yes, it does appear to be self-promotion. Mr. Goolsbee has also been busy finding solar and fuel-cell related articles on Wikipedia, and adding links to his project at the bottom.

I moved the Benefits and History sections to Solar chimney, as they don't apply specifically to his Solar Tower brand. I also copied the intellectual property section, it's in both articles. I wasn't sure what to do about capitalization - in the chimney article, I'll remove most mentions of Solar Towers. In this article, I think we should use lower case "solar tower" or the term "solar chimney" when we refer to a generic solar chimney, and "Solar Tower" only when referring to the activities of the companies using that brand. Since this article is not an advertisement, we don't need to use trademark symbols - Mr. Goolsbee, please don't reinsert them. Rhobite 13:21, Oct 15, 2004 (UTC)

Hmmm, I've removed the duplicated Intellectual property... section from solar chimney before reading the above... it seemed to refer only to this particular design, not the more general concept. They seem vague about exactly what they're claiming... the enviromission website reads in part EnviroMission owns the exclusive licence to German designed Solar Tower technology in Australia, which doesn't seem to affect other solar chimney designs, but it's an interesting turn of phrase. Why German designed? Is this qualification intended to extend the claim to all German work, or to restrict it to only German work?

The claim in the now moved history section that no patent was granted following the building of the German prototype is another interesting turn of phrase. Was one applied for? If so, why was it denied? Andrewa 20:36, 17 Oct 2004 (UTC)

[edit] Physics

Why does the tower have to be so high? --noösfractal 22:23, 14 September 2005 (UTC)

Good question. For a project of this size (200MWe), you'd expect that the dimensions would be based on calculations of the performance of various sizes, so as to choose the optimum. But the only prototype they have is the German-financed plant in Spain, which was 50kWe (note the k not an M, so it was 4,000 times smaller than the proposed plant), and it seems that they don't want to release even that data for public scrutiny. That's not a lot to go on. If the plant is to be operational by 2008 (older sites say 2006), the size of the chimney will need to be decided fairly soon.

Some years ago (early 70s), at the Parkes Radio Telescope, they bought a laser to eliminate the cable that ran between the two dishes they then used as an interferometer. They actually had the laser on site for six months before anyone got it out of the box and tested it to see whether the beam would actually get from A to B. The answer was no, owing to thermal turbulence. Nobody had thought of that. End of project. You'd be a brave financier to put up money for a 200MWe plant based on data from a 50kWe prototype, even if they do say they'll build it from recycled materials.

I could be wrong. Andrewa 23:29, 7 October 2005 (UTC)

Or I could be right. See Talk:Solar updraft tower/Archive#Some interesting previous content. As I say there, This power plant operated successfully for approximately 8 years and was decommissioned in 1989 (current article content) is a very different story to It was destroyed by heavy weather and thunderstorms in 1989 and was officially decommissioned (previous version). I wonder which is the true story? Andrewa 11:34, 8 October 2005 (UTC)

The height has several impacts. From a pure fluid mechanics point of view, you want a smooth flow of air, and keeping turbulence (which happens at the exit) away from the turbines helps. Also, the power yield of the updraft is related to the temperature differential. The sun creates the most heat where it strikes at the ground, so air near the planet surface is warmer. The higher you go away from the ground, the cooler it gets. This is why the tower works at all. And since power yield is based on temperature, it's thus also based on height.

As for the reason they have no got a final height, the generator fans at the base will have an optimum airflow power range. At this point they probably also know how many they want to use. So depending on other factors like local weather and these heating ponds and other design revisions, the numbers for the height will shift to accomodate this. There's only a local market for a certain amount of power, so if they can reduce the height and keep the output constant by making a tweak to the design at ground level, this makes the project more profitable and less risky. Someone with a civil engineering degree can probably explain it better than me though, I'm just a former mechanical engineering student. Adam Kennedy

[edit] Production capacity

Does anyone know how much energy the Wentworth Shire tower is expected to produce? Akamad 08:25, 23 September 2005 (UTC)

• It says 200 MW at the Wentworth Shire link. --noösfractal 08:35, 23 September 2005 (UTC)

My personal expectation is zero. (;-> Andrewa 19:23, 7 October 2005 (UTC)

It now says 50 MW on the Enviromission site, announced 20 September 2005 under the banner Move to High Capacity 50MW Solar Tower Power Option. It's to be a 50MW power station at the Sunraysia site in Buronga, NSW, so I guess it's the same project, but it's now been reengineered for more smaller towers, and just one of them for a start. The announcement doesn't mention the physical size of this reengineered tower. It still says 200 MW on the Wentworth Shire site, which hasn't been updated for a while now. Expect further upgrades... (;-> Andrewa 03:29, 28 October 2005 (UTC)

[edit] Merge Proposal

Those two pages Solar Tower and Solar Tower Buronga are both about the very same structure; it like having two articles, one about Golden Gate Bridge and another one about Golden Gate Bridge (San Francisco). There is already a third article about solar chimneys in which the generic concept is discussed. Specifically, I would suggest to move the section about Competition from Solar Tower into Solar chimney, and take the specifics about Schlaich, Bergerman and Partner, EnviroMission and SolarMission Technologies Inc. and details of construction as there is in Solar chimney together with Solar Tower Buronga and merge that into Solar Tower. That way Solar chimney can be cleaned up and can be devoted to the concept only, and we will have one single article devoted the proposed commercial realization and construction of one of those structures in Australia. JDH 14:40, 29 January 2006

See Talk:Solar Tower Buronga. Andrewa 19:48, 18 February 2006 (UTC)

There is a lot of overlap between Solar chimney and Solar Tower. Both focus on the yet-to-be realized EnviroMission project in Australia. I don't think we need two articles on that subject. So I propose to move all the Schlaich, Bergerman and Partner, EnviroMission and SolarMission Technologies Inc. as there is in Solar chimney, and merge that into Solar Tower. That way Solar chimney can focus on what it really is supposed to be, and what has now been marginalized: An approach to passive cooling of buildings, see http://www.greenbuilder.com/sourcebook/PassSolGuide3.html. When you go back to the origins of the Solar chimney article you will see that that is what it was originally about, see http://en.wikipedia.org/w/index.php?title=Solar_chimney&oldid=6597806 , until it was overwhelmed by the EnviroMission folks JdH 04:21, 15 May 2006 (UTC)

see Talk:Solar_chimney#Merge_Proposal JdH 16:49, 17 May 2006 (UTC)

I've moved relevant material here from Solar chimney (see Talk:Solar_chimney#Merge_Proposal). It will need to be tidied. --Singkong2005 ^{(t - c - WPID)} 06:13, 24 June 2006 (UTC)

[edit] Rename

Following from the merge discussion, I'd support a generic, non-trademarked term as the name for this article, instead of Solar Tower. Schlaich uses "solar tower" (uncapitalised) as a general term, so Solar tower (power generation) is probably acceptable. "A solar updraft tower power plant – sometimes also called 'solar chimney' or just ‘solar tower’" [1]

Solar tower should probably be the disambig page (rather than Solar tower (disambiguation) , and the current Solar tower moved to Solar tower (astronomy. --Singkong2005 ^{(t - c - WPID)} 06:13, 24 June 2006 (UTC)

I think we need to move Solar Tower to something that sets it clearly apart from both Solar tower and Solar power tower, and from Energy Tower as well. One way would be to move Solar Tower to Solar Energy Tower (updraft) and Energy Tower to Solar Energy Tower (downdraft). Solar Tower should redirect to Solar tower, and Energy Tower would become a disambiguation page. However, in view of past history it would perhaps be better to change both Solar Tower and Energy Tower into disambiguation pages.

Suggestions are welcome JdH 09:04, 25 June 2006 (UTC)

This is a tricky one.

Just checked Wikipedia:Naming conventions - principles that apply here include

• Use common names of persons and things
• Give priority to what the majority of English speakers would most easily recognize, with a reasonable minimum of ambiguity, while at the same time making linking to those articles easy and second nature.
• Do not capitalize second and subsequent words unless the title is a proper noun (such as a name) or is otherwise almost always capitalized.
• These are conventions, not rules written in stone. As Wikipedia grows and changes, some conventions that once made sense may become outdated, and there may be cases where a particular convention is "obviously" inappropriate. But when in doubt, follow convention.

I need to give it some more thought and do some googling of terms before commenting further. --Singkong2005 ^{(t - c - WPID)} 05:38, 26 June 2006 (UTC)

Just checking the German wiki to get some inspiration: The article itself is called "Thermikkraftwerk"; that would translate as "Thermal power plant"; other terms used in that article: "Aufwindkraftwerk"; that translates as "Updraft power plant", and then there is "Aufwind-Solarkraftwerk"; that would be "Updraft solar power plant". JdH 17:40, 26 June 2006 (UTC)

And yes, I am not too eager to change the present name of Solar tower to something else; the reason for that you can find here The 150-Foot Solar Tower History; the point is that name Solar tower has been used for an astronomy instrument for 100 years; I think it is inappropriate for H. Alfred Goolsbee to copyright that very name for something totally different. Looking at the German wiki was very instructive: Schlaich himself calls it "Aufwindkraftwerk"; he does not use the German equivalent of "Solar Tower" at all.

Well, I decided to be bold, and rename this thing to "Solar updraft tower". This name was used in a paper I found on the site of Schlaich Bergermann und Partner (SBP), Stuttgart. JdH 20:41, 30 June 2006 (UTC)

But it's such a rare term - the people building one call it "Solar tower" and "solar updraft tower" gets only a couple dozen Google hits. --Wtshymanski 00:58, 1 July 2006 (UTC)

Actually, I get over 200 hits with "Solar updraft tower" (allowing some variations such as "Solar updraft power tower" or "Solar updraft power plant" "updraft tower power plant" etc). I think a google search with "solar tower" is pretty useless, because it is going to include tons of unrelated stuff.
But trust me: Wikipedia rules! Within a few months from now you will see a proliferation of the number of hits you get with "Solar updraft tower". JdH 01:42, 1 July 2006 (UTC)

some of this naming problem actually goes back to the companies promoting the idea ... the most natural name for the idea orignally seemed "solar chimney", because it uses a chimney effect, but this was thought to sound too much like an environmental polluter, and so they went for the name "solar tower".--Flexme 01:05, 11 July 2006 (UTC)

[edit] Byproducts

I just removed an entire section on Byproducts which I thought
was not germane to the topic of the article. I will move it here
for future reference JdH 18:27, 29 June 2006 (UTC)

[edit] Some useful links

• Concentrating Solar Thermal Systems Solar Thermal Energy Research
• Schlaich Bergermann und Partner (SBP), Stuttgart
• Jörg Schlaich, et al Design of Commercial Solar Updraft Tower Systems
• Gerhard Weinrebe Slide presentation, 1.Juni 2006 slice 37 provides a useful overview
• Renewable Energy Sector gets a Solar Powered Boost Ministers - Industry, Tourism and Resources
• Scott Rochfort Enviromission seeks a handout
• Baulderstone joins solar team
• Company Overview
• Efficiencies allow 50 MW to 200 MW Solar Towers
• Competitive Operating Performance
• Low Emission Technology Development Fund (LETDF) application
• History of the Solar Tower
• Management
• Investment Prospects
• Green energy plan to use smaller solar tower
• Torre solar de 750 metros de altura en Ciudad Real (España)
• Monohans Solar Tower Project
• China invests in solar towers

[edit] Solar Tower Buronga

Question: What do we do with this section? I have already truncated in half, but I would like to take it out completely. Basically, the problem is that the thing has been in the planning stage for 5 years now. It appears that the original design has been abandoned, and a scale-down version has been proposed instead. But it remains uncertain whether that scaled-down version will ever be built. So all we really can say at this point in time is that EnviroMission wants to built one, but they don't seem to be able to pull it off. I don't think that that belongs in Wikipedia, but I would like to get other people's opinion before axing it. JdH 03:05, 2 July 2006 (UTC)

At least Enviromission is a listed company that is required to report its activities. I have more trouble with the Evaluation and Competition sections that seem to be quite biased and drawing conclusions here that are not contained in the cited sources. --Scott Davis ^Talk 07:05, 2 July 2006 (UTC)

200 MW/(38 km²× 1 kW/m² )= 0.5%

500MW /(4,500 acres × 4046.86 m2/acre × 1 kW) = 2.75%

The weakest link in these calculations is the kW/m²; see Solar power for a discussion of that issue. The other numbers are firm: they come from the references provided. You are welcome to use a lower number for kW/m²; all that would do is bump up the percentages a bit, but it wouldn't change the basic conclusion: Compared to the Solar Tower Buronga (original design) the proposed SCE/SES plant will produce 2.5× more power on half the area.

There are plenty of references in this article; if there is a problem it would be some of them were removed, including very relevant ones to the websites of SBP & EnviroMission. Also some news articles which describe lack of progress with the Buronga project have been removed. JdH 08:27, 2 July 2006 (UTC)

I take that back. While it is true that there are plenty of references there is a dearth of scholarly information. The only thing out there that provides some solid information is the Schlaich paper. What I would like to see is a good independent review, and I don't have much luck; I did find some 25 independent papers in the scientific literature that address different technical aspects, but the only independent review I have found thus far is
Pretorius JP, Kröger DG (2006). "Critical evaluation of solar chimney power plant performance". Solar Energy 80 (5): 535-544.  doi:10.1016/j.solener.2005.04.001
Suggestions are welcome. JdH 02:08, 5 July 2006 (UTC)

I have trimmed and reshuffled the info that was in the subsection
"Solar Tower Buronga". All what is left now is the current status
of the project. Below I will copy what this section looked like
back on June 29, 2006 before I started trimming it. We may use it
and put some of it back if and when Solar Tower Buronga gets in
the air. JdH 23:27, 7 July 2006 (UTC)

[edit] Carnot engine

Trying to move a conversation out of the XML comments. I said on 2 July This seems irrelevant as Carnot heat engine is about a closed system, which the solar tower is not. Needs a reference to a paper that says the small heat differential is the main problem with a solar updraft tower, and uses Carnot's theorem to explain it..

JdH said The yield of the Solar Tower is only 0.5%, which is quite low by any standard, in particular those of parabolic throughs and solar dishes. I don't understand the argument about "closed system"; the same rules apply, regardless whether you have a pocket sized device or one of 1 km high and 7 km in diameter

User:211.29.251.98 said this seems like rubbish ... the main problem seems to be the large initial financial and physical investment, and the immobility of the completed tower.

The issue is not the size of the project. The Carnot theorem appears to only be relevant where the system is closed, and the medium being heated needs to be cooled and recycled. The solar chimney is open at the edges of the collector, and open at the top of the chimney. The air is not collected at the top of the chimney, cooled, and returned to the edge of the collector, therefore to my mind, the Carnot Theorem is irrelevant. If it is relevant, it needs a reference saying it is relevant. --Scott Davis ^Talk 06:20, 9 July 2006 (UTC)

What is at issue here is a comparison between the Concentrating solar systems, and the Stirling dish/steam engine approach in particular, on one hand, and the updraft tower plant on the other. The argument is that since the temperature differences in the dish/Stirling setup is far greater (hundreds of degrees rather than tens of degrees) that its conversion efficiency is far greater (presently 30%, and getting better). This issue of conversion efficiency in connection with solar energy is already discussed in Wiki in different places, see e.g. Solar pond, Concentrated Solar Power (CSP) Plants, Exergy and various other places, so I don't think that this is the right place to discuss this here in any detail.
With regards to the updraft power plant: In the end there is a closed loop too: air is warmed up under the canopy, flows up the chimney, and eventually cools down again, and recycled. You can consider it to be a very very large heat engine that not only includes the greenhouse and the chimney, but a large section of the surrounding atmosphere and countryside as well, and there is no reason to declare the principles of thermodynamics invalid. Implicitely the issue is already discussed: According to the Schlaich paper the conversion efficiency gets better with higher towers, and larger canopy's; the underlying reason is a thermodynamic one: Temperature differences and therefore pressure differences increase with size.
btw, that "Carnot cycle" was not put in by me, it may have been Sillybilly; it may be a good idea to ask for his input on this issue. JdH 10:46, 9 July 2006 (UTC)

when you say there is a closed loop you are mistaken. the incoming air is not the outgoing air ... furthermore ... the air which comes in is given a boost of energy from an outside source before it goes out ... this is not closed.--Flexme 16:11, 10 July 2006 (UTC)

If that were true it would be even more difficult to explain that conversion (in)efficiency of 0.5%. But is isn't: There is nothing about the updraft tower that cannot be explained within the framework of classical thermodynamics.
Basically, like all heat engines, the thing is driven by a difference in temperature. The temperature of the air inside the chimney is higher than the temperature outside; that's all, that is what is driving it. Air expands at higher temperature; therefore the air inside the chimney is less dense than the outside air. Just consider the weight of a column of air inside the chimney with a comparable column of air outside: Because of its higher temperature, and hence lower density that column of air inside weighs less than the column outside; and that difference in weight causes a pressure difference at ground level between inside and out. It is that pressure difference what is driving the turbines.
There really is nothing mysterious happening outside: All that counts is the temperature and pressure of the outside air. There is no reason to invoke non-equilibrium thermodynamics; all we are talking about are temperatures and pressures, concepts that are perfectly well understood within the framework of classical thermodynamics. No "massive" "boost" or anything from something mysterious happening outside the tower.
Of course, when the thing is actually in operation there are all sorts of losses, such as drag and flow induced pressure gradients within the chimney; those are some of the issues that need to be taken into account when doing quantitative predictions. As are the efficiency of the collector. Or the Betz Limit. All of those help explain that 0.5% JdH 12:17, 11 July 2006 (UTC)

The interest of the Carnot cycle is that it sets a quantitative limitation on the efficiency of all heat engines, not just cyclic ones. This is all explained in the article on the Carnot engine. A PWR, for example, is less thermally efficient than a coal-fired boiler of the same capacity, owing to the higher steam temperature possible with coal. These heat engines are neither cyclic nor closed (not in the senses used above, anyway). Andrewa 19:29, 12 July 2006 (UTC)

Hi, it was suggested that I come here and give my two cents worth. Coincidently, recently I separated Carnot heat engine into: Carnot cycle and Carnot heat engine and I uploaded the two new images of the original drawing for the Carnot heat engine and a modern one. After skimming this article and talk discussion quickly, I would argue that the solar updraft tower is in essence a heat engine. There is a furnace, i.e. the greenhouse, which provides the heat (body A); and there is a condenser, i.e. the cooler upper atmosphere, which absorbs the heat (body B). By way of passage of heat from body A to body B work is produced. This is the basic statement of the second law of thermodynamics.

To clarify further, from the Carnot heat engine page:

A heat engine acts by transferring energy from a warm region to a cool region of space and, in the process, converting some of that energy to mechanical work. In the adjacent diagram, from the original 1824 paper by Sadi Carnot entitled On the Motive Power of Fire, we are told to “imagine two bodies A and B, kept each at a constant temperature, that of A being higher than that of B. These two bodies, to which we can give or from which we can remove the heat without causing their temperatures to vary, exercise the functions of two unlimited reservoirs of caloric. We shall call the first the furnace and the second the refrigerator.” Carnot then explains how we can obtain motive power, i.e. “work”, by carrying a certain quantity of heat from the body A to the body B.

So, as to the Question: Is the Carnot Theorem applicable to the Solar updraft tower or not? The answer is yes. To clarify further, according to Carnot:

“In order to consider in the most general way the principle of the production of motion by heat, it must be considered independently of any mechanism or any particular agent. It is necessary to establish principles applicable not only to steam-engines but to all imaginable heat-engines, whatever the working substance and whatever the method by which it is operated.”

Following this and other statements, Carnot went on to develop his rule for calculating the maximal possible thermodynamic efficiency for any possible heat engine configuration. The efficiency calculated by this method only sets the maximal limit; no real heat engine, however, can reach this level of efficiency. Steam engines in olden days were less than 2% efficient, modern engines are at most 40% efficient. I hope this helps.--Sadi Carnot 03:06, 19 July 2006 (UTC)

Thank you for your interest. Intuitively, a solar tower does not appear to be in equilibrium, therefore cannot be a reversible process and as such, Carnot's theorem does not apply. I will happily accept any claim properly supported by a reliable source added to the article. If it applied, Carnot's theorem would indicate a theoretical maximum efficiency for a heat engine. The original discussion of Carnot in this article was in an extrememly negative paragraph, using Carnot to demonstrate that

"The main problem with the solar updraft tower concept is the relatively small difference in temperature ...". Even a 2% efficient steam engine is a useful tool. It's just more expensive to operate than a 40% efficient one on the same fuel. In this case, the fuel (sunlight) is free, so other factors influence the choice of technology to harness it. --Scott Davis ^Talk 04:34, 19 July 2006 (UTC)

Scott, your suggestion to have a reliable source attached to this is good idea. WP articles and talk-pages are not the proper place to do original research. However, just to set the record straight, coming from a friendly perspective, people who invoke words such as “equilibrium”, “reversibility”, “open-system”, etc., so that they might win their random argument based on some backwards use of semantics, are completely missing the point. Adios:--Sadi Carnot 19:44, 19 July 2006 (UTC)

You're right - I have missed the point. Thankyou for being polite whilst saying so. That was the chain of articles I had read to attempt to understand, and I still don't understand that a solar tower is in a state of equilibrium. Possibly I need to read the thermal equilibrium article again, as it's different to chemical equilibrium. I came to (a predecessor of) this article to learn, not to teach, and have ended up involved in this mess by trying to work out what is real and what is made up or OR. However, I did not feel I was making a "random argument", or attempting to win one by invoking big words. --Scott Davis ^Talk 23:21, 19 July 2006 (UTC)

I find it hard to believe that anyone really believes that the Solar Chimney can violate the Carnot cycle limit on thermal efficiency. I thought that was as close to a closed question as science can deliver. Albert Einstein once stated that thermodynamics had impressed him in a unique way, in that he was convinced that within the limits of its assumptions it would never be overturned.

But my most recent study of thermodynamics was in 1972, so it's a bit rusty. IMO we need someone who has studied it (as in passed exams and submitted assignments) a bit more recently. Andrewa 14:40, 22 July 2006 (UTC)

What would be interesting then is a citable reference that presents the theoretical maximum efficiency of a solar chimney in ideal circumstances. If Sadi Carnot and Andrewa are right, that hypothetical paper will use the Carnot Theorem as part of its calculations. It is likely to also use Betz' or some other theorem relating to theoretical maximum efficiency of the turbines, as these are also important in the overall process. This paper is likely to conclude that the theoretical maximum efficiency is somewhat higher than the initial proposed capacity which JdH has said will be around 0.5%, in the same way as steam engine efficiency improved with experience and newer technology. Is convection constricted by the Carnot cycle limit? --Scott Davis ^Talk 16:00, 22 July 2006 (UTC)

IMO nobody is likely to publish a citeable paper on the thermodynamics of the sort of solar chimney proposed here! I could be wrong, but the concepts and principles are nothing terribly exciting. The fascinating thing is that so many people can be persuaded to have such faith in such a bizarre proposal. Doesn't the fact that the proposed chimney was so much bigger than the only prototype to date tell you anything?

What you might find is an assignment question from a second-year university physics course in introductory thermodynamics. It wouldn't even be an honours question. Andrewa 19:20, 25 July 2006 (UTC)

To help clarify this debate, compare the Solar updraft tower to the Aeolipile, which has been defined (not be me) as the world's first steam engine (or heat engine, technically).--Sadi Carnot 02:46, 31 August 2006 (UTC)

[edit] Betz limit

the betz limit is discussed in depth in the wind turbine page ... its derivation involves comparing the speed of the wind going through the turbine to the speed of the wind far away from the turbine ... this has absolutely no place here, the turbines in this tower will be enclosed and are not subject to this limit. I believe we should completely discard discussion of the betz limit.

The turbines used here are more like turbines, engineers do not apply the betz limit in here.

the only reason i have not done this yet, is that three people i have discussed this with have disagreed with me ... however the truth is not democratic.--Flexme 15:12, 10 July 2006 (UTC)

Does "far away from the turbine" mean undisturbed air in the same plane as the turbine, as you interpret here? I interpreted it as meaning upstream and downstream in the airflow through the turbine, but in steady flow outside of the local effects of the turbine. If the Betz Limit does not apply, there must be some other study of fluid dynamics that expresses theroetical calculations on how fans, turbines, propellors etc work, and how to identify the optimal size, angle of attack, speed etc. Intuitively, if all the kinetic energy is removed, the airflow stops, and if none is removed, the turbine stops, so there must be some middle ground. --Scott Davis ^Talk 23:21, 12 July 2006 (UTC)

i love your reasoning ... "if all the kinetic energy is removed, the airflow stops, and if none is removed, the turbine stops, so there must be some middle ground" you moderator you!!!! ... unfortunately it is not appropriate in a applied physical scenario ... the limit may approach either end of you bounds up to 99.99999999% Of course there will be best efficiencies that are achieved in our current technology ... it will be related to , in particular, subsonic (possibly incompressible) air flow through a turbine in a pipe ... hopefully we will find this soon.--Flexme 09:52, 13 July 2006 (UTC)

The discussion on Betz's limit comes from the article by Haaf et al "Haaf W, Friedrich K, Mayr G, Schlaich J (1983). "Solar Chimneys. Part 1: Principle and Construction of the Pilot Plant in Manzanares". International Journal of Solar Energy 2 (1): 3-20. " It is up to you to come up with a source that repudiates Schlaich himself JdH 20:33, 3 August 2006 (UTC)

[edit] Atmospheric winds

it is presently claimed that winds at the top of the tower will disrupt the function. surely an atmospheric wind would cause suction at the top of the tower due to the venturi effect, this should increase the suction and give a greater productivity ... perhaps a power generator could be constructed utilising this alone ... aiming at the prevailing strong winds--Flexme 15:28, 10 July 2006 (UTC)

There are two references that discuss the effect of atmospheric winds, and they look at different effects and come to very different conclusions.
The El-Haroun paper looks at the effect of wind speed at the top of the tower, and claims that "the mean inlet air velocity to the solar turbine is found to be 117% of its value for a wind free turbine"; those numbers were calculated for a location somewhere in Egypt.
The Serag-Eldin abstract looks at an entirely different effect; it seems more concerned about wind effects on the collector. It says "The analysis reveals a total degradation of performance with strong winds, and considerable degradation even with weak winds unless the collector inlet height is relatively low". JdH 15:36, 11 July 2006 (UTC)

sounds interesting ... do you have links that work ... i try those there but do not seem to be able to find them ... maybe it is just my computer?! I would like to see a better discussion of these effects. I am sure we can work something out.--Flexme 14:02, 12 July 2006 (UTC)

Flexme, can I ask if you have some kind of formal training or qualifications in physics and/or fluid dynamics? It would be very useful to have an expert on the subject contribute, if indeed you are such. --User: Jaganath 11:07, 13 July 2006 (UTC)

training and qualifications are surely irrelevant, most successful students are pitifully unaware of the truth, truth should see through such trivia ... the truth will be ultimate ... i will do my best to see the ultimate come A.S.A.P.--Flexme 10:45, 13 July 2006 (UTC)

[edit] Conversion Rate of Solar Energy to Electrical Energy

The solar updraft tower does not convert all of the incoming solar energy into electrical energy.

Test units of 50 kWe have been built with a solar-to-electric net annual efficiency of 0.05%. According to model calculations an updraft power plant with an output of 200 MW would need a collector 7 kilometres in diameter (total area of about 38 km²) and a 1000 metre high chimney.^[1]
With total area of 38 km², it appears that it would extract about 0.5%.^[2] of the solar power (1 kW/m²) that falls on the area it covers. Because no data available to test these models on a large-scale updraft tower there remains uncertainty about the reliability of these calculations.^[3] Many designs in the solar thermal group of collectors have higher conversion rates. The low conversion rate of the Solar Tower is balanced by the low investment cost per m² of solar collection.^[4]

If less than 1% of the sunlight becomes electricity, then where does 99% of the energy go? Some of the causes of loss are shown below.

1/ Reflection of light off the top of the canopy imply a loss of 7.7% of incoming solar energy, as calculated by the fresnel equations, if the canopy is made of common glass.

2/Transmittance losses of sunlight through the canopy. this requires detailed information about the frequency components of the incoming light, and the absorption properties of the canopy. {Analysis of regular sunlight through glasses should be available somewhere.}

3/Reflection of light off the floor of the greenhouse and back out through the canopy, taking its energy with it. This will be very highly dependent on the surface on the base of the greenhouse.

4/Heat leakage by radiation and conduction back out through the canopy from the higher temperature environment under the canopy, to the lower temperature environment above it. These losses will be proportionally related to the surface area, and the surface area of the canopy is likely to be huge. {i am guessing that these may be reduced a little through double glazing of the central section of the canopy where heat is highest, and careful selection of material used for the canopy.}.

5/Turbine losses {i think these will only be quite small, turbines have always been quite good, computers have made them more efficient}.

6/Turbulence losses may erupt around the base of the tower where high speed is seen, especially in a faulty design. Inside the tower, laminar flow or turbulent flow may dominate depending on the flow characterisics, narrow towers would tend to exhibit turbulent flow with greater energy losses, wide towers are likely to be laminar. {excessive width will result in a lack of chimney effect}

7/Skin friction losses will be where laminar flow dominates.

8/Imperfect tower height. {Thermals have a height to which the convection currents rise then become stable, to go lower or higher than this height will result in energy loss. even if the tower is made to exactly the correct height, it is not clear to me that all energy will be extracted. the glasshouse temperature and local atmospheric conditions will affect the best height; the fact that the atmosphere constantly changes makes this a very difficult loss to avoid. however from a realistic construction point of view it does seem clear that bigger is still better. complete disfunction may result in the case of a temperature inversion}

{i have put some discussion of my ideas on optimal tower height in my talk page, it is a little too hazy, and controversial to have here as yet, feel free to look and/or contribute.}--Flexme 07:11, 15 July 2006 (UTC)

9/The performance of an updraft tower may be affected by atmospheric winds^[5][6], or by drag induced by bracings used for supporting the chimney.^[7] Of course the venturi effect may increase productivity when their are winds at the tower top.--Flexme 11:40, 14 July 2006 (UTC)

[edit] move to Adaptations section

A solar updraft tower with a sloped collector on the side of a hill facing toward the equator, can be located at high latitues, such as in Canada, and may then produce up to 85% of a similar plant at low latitude locations.^[8].--Flexme 02:43, 13 July 2006 (UTC)

[edit] Farmland under the canopy?

Can the land under the outer rim still be used for farmland? This will require water (is water infusion into the airflow a positive or a negative?).

What percentages of the land used are either too hot or too windy?--Flexme 16:52, 10 July 2006 (UTC)

i just went hunting through the solarmission website ... they discuss degradation of concrete, a dry arid environment is required otherwise the tower is likely to degrade more rapidly. So water seems to be bad for longevity of the power plant. They also discuss temperatures as much as 100F above ambient ... and will kill plants ... i will imediately remove any farm type comments in the page.--Flexme 03:27, 11 July 2006 (UTC)

with the Floating Solar Chimney Technology, there is no concrete tower, and so the introduction of water may be sensible in this case. however it would still only leave the outer rim of the glasshouse usable.--Flexme 14:01, 12 July 2006 (UTC)

[edit] Neutrality

This article been recently been revamped by an editor from Australia, a person who could very well be on the payroll of EnviroMission, and who has pretty much edited out anything that is even remotely critical of EnviroMission's POV. It now pretty much reads like a brochure of EnviroMission. For comparison you may want to have a look at my Revison as of 23:11, 7 July 2006 to see what is going on. Going back in the history of this article reveals that this kind of stuff has been going on before.
I have put in considerable effort in bringing this article up to Wikipedia standards, specifically improve the description of the technology, adding references, and put in an unbiased discussion of strengths and weaknesses of the technology. I was not yet done cleaning up this article; I intended to tighten it further, get it more focussed on describing the technology, including a discussion of conversion efficiency. I just wrote a section comparing conversion efficiencies of the updraft power plant with competing solar thermal plants; that section was promptly excised and moved someplace where it is conveniently out of sight, see Solar thermal energy. JdH 17:44, 11 July 2006 (UTC)

To clear up any possible misunderstanding about this: I don't think that EnviroMission has anything to do with Flexme's edits, and is in no way responsible for any of it. JdH 15:08, 16 July 2006 (UTC)

the solar updraft tower page requires discussion of as many and various aspects of solar updraft towers as possible ... the overview of conversion rates of various solar collectors should be on the solar collector page ... it struck me as very strange that it was not there, but it was here. I have tried very hard to remove anything that is not related to solar updraft towers, and I have tried very hard not to remove anything that is related to solar updraft towers, whether it is pro enviromission or anti ... further ... if the enviromission people did want to contribute, then surely they should be allowed to, they probably know a lot more about this stuff than you and me(of course self interest groups should not be given compete freedom, wikipedia is good at that.--Flexme 14:00, 12 July 2006 (UTC)

Flexme - you said: if the enviromission people did want to contribute, then surely they should be allowed to, they probably know a lot more about this stuff than you and me(of course self interest groups should not be given compete freedom, wikipedia is good at that

People are discouraged (but not forbidden) from editing Wikipedia articles about themselves - see here - and this seems to apply to businesses as well (see intro to that Wikipedia guideline page). In these cases, they are encouraged to make suggestions/corrections on the talk page instead, allowing other editors to incorporate the material. Of course, if someone from the company did that, in good faith, trying to improve the article, then I would rather not condemn them, but rather suggest them to make all further contributions via the talk page. --Singkong2005 ^{(t - c - WPID)} 03:29, 13 July 2006 (UTC)

thanks Singkong2005, i can see what you say ... jdh has very respectfully stopped editting, and (now) i will also ... this leaves us where we are now : my last page edit seems to be out there representing the truth of wiki, of course i believe in myself, but we do need to have a sensible page in the meantime ... how about a last version created by neither jdh nor myself? (i have no idea what it is and hate to think?!)--Flexme 10:22, 13 July 2006 (UTC)

am i correct in thinking that you,JdH, added lots of details to this page, ALWAYS casting doubt on the feasibilty of solar updraft towers, that you changed the name from solar tower to solar updraft tower which is much more obscure, that you requested deletion of the Floating Solar Chimney Technology page? it does seem that there is a neutrality issue!!--Flexme 14:23, 12 July 2006 (UTC)

Regarding the name - I was also part of that discussion. It was a difficult issue, but I believed there was no clear choice, but the decision made was a reasonable one. Of course you're free to make other suggestions, addressing the reasons given by JdH and others for the rename. --Singkong2005 ^{(t - c - WPID)} 03:29, 13 July 2006 (UTC)

the rename is not really something for us to decide, it does not depend on the input from members in the past ... it IS dependent on the human race ... i f most IP addresses find that "solar tower" means that they must next find an alternative link to a different page called something else ... then that page should replace the first. i am surprised that this is not automated in wiki ... (who should i talk to?)--Flexme 10:05, 13 July 2006 (UTC)

Which "editor from Australia" are you accusing? --Scott Davis ^Talk 01:15, 13 July 2006 (UTC)

Following ScottDavis's comment - it's best to name an editor and politely discuss edits made.

Since things are getting a little heated here, I'll mention that I already suggested to JdH to assume good faith. I could also add do not bite the newcomers - and since JdH has only been here a few months, that applies both ways. Hopefully we can move past the accusations and deal with the substance of the article.

JdH, could you please post a link to the changes that you disagree with. Thanks --Singkong2005 ^{(t - c - WPID)} 03:29, 13 July 2006 (UTC)

[edit] Mediation

The issue on edits concerning advantages and shortcomings was submitted to the Mediation Cabal, and the case is now open at Wikipedia:Mediation Cabal/Cases/2006-07-12 Solar Updraft Tower. If you have any suggestions, arguments or compromise proposals, please comment or take part in the discussion on the case page. I'd also suggest to avoid further personal discussions here and continue them on the case page so they don't affect the article and can be better addressed. CP/M 03:47, 13 July 2006 (UTC)

[edit] floating chimney

If I read JdH correctly, you claim that the pressure inside the solar tower is lower than the pressure outside it. This may be true near the bottom (the pressure in the bottom of the tower is presumably lower than the pressure under the canopy), it cannot be true at the top, or atmospheric air would pour in to the tower instead of acting as a chimney. Or is it all powered by convection, not pressure differences? Either way, I'd imagine the choice of concrete rather than lightweight fabric with hoops for the top part is based on requirements of stability or durability, not rigidity and strength. --Scott Davis ^Talk 02:41, 15 July 2006 (UTC)

the issue of loft of a heavy tower could be simply solved ... there is a continual massive stream of warm air coming out the top of the tower, this can be diverted as needs arise, into a huge hot air balloon providing lift. i doubt this would be more feasible than i standard concrete tower ... as jdh says it will require support ... without a rigid framework the tower will not give suction to the turbines at the base ... of course the turbines could be at the top of the tower floated up by the giant balloon, then the tower would be inflated .... hmmm quite wild.--Flexme 05:07, 15 July 2006 (UTC)

[edit] Rename (revisited)

[edit] Reasoning

Flexme has been arguing for a rename from Solar updraft tower to Solar tower, and I felt this is best addressed in a separate section.

The various sides of the issue were considered recently and at least some of the changes that were made were a definite improvement (e.g. solar chimney now refers to the passive solar architectural feature, rather than the energy plant). So let's say, good work so far, but there's nothing to prevent us making further changes as well.

Arguments for moving to "Solar tower": Flexme is correct that googling "Solar tower" mainly leads to the solar power generation structure (i.e. the subject of this article), and that's what solar tower usually refers to in the media. So Solar tower probably shouldn't lead to a different topic. Solar updraft tower might be a better name for the device, but it is also less than ideal from the point of view of the convention of using common names. (Of course we shouldn't overdo it, but in this case I would argue that the overwhelmingly more common name is "Solar tower."

Arguments against moving to "Solar tower": As I understand it, "solar tower" until very recently was used almost solely to refer to the astronomical observation tower. That's a fairly strong argument that Solar tower should not lead directly to a different topic.

All of that leads to my suggested resolution, which I'll put in a subsection below. It may not be everybody's favorite solution, but it might be one we can all live with happily enough - or it might prompt someone to suggest a more acceptable solution. --Singkong2005 ^t_c 01:32, 17 July 2006 (UTC)

[edit] Proposal to make Solar tower a disambiguation page

Proposal: Have the disambiguation page at Solar tower, linking to renamed pages Solar tower (energy plant) and Solar tower (astronomy).

The problem with with Solar tower (energy plant) is that it does not resolve ambiguity. The word updraft is needed to differentiate it from the Solar power tower. Energy plant is not a good Google keyword either; see below for a discussion of that issue. JdH 19:55, 17 July 2006 (UTC)

As updraft is not part of the common name, it's best included within the parentheses. e.g. Solar tower (updraft energy plant) or Solar tower (updraft power generation). --Singkong2005 ^talk 12:48, 30 July 2006 (UTC)

• Neutral Support - as I argued above... But as long as disambiguation pages and top links continue to be handled properly, I'm not going to complain loudly. --Singkong2005 ^t_c 01:32, 17 July 2006 (UTC) Changed to neutral for now - JdH makes a strong case. --Singkong2005 ^t_c 08:05, 18 July 2006 (UTC)
• Support based on Wikipedia:Avoid neologisms. As convenor of the discussion, would you like to also mention it on talk:Solar tower? --Scott Davis ^Talk 04:04, 17 July 2006 (UTC)

Yes, I should have done that - have put a note there now. --Singkong2005 ^t_c 08:05, 18 July 2006 (UTC)

• Oppose First let me first clarify some more how I arrived at the name Solar updraft tower. As mentioned in the discussion above, the name Solar Tower is too ambiguous. If you do a google search with Solar Tower (no quotes) you get > 10,000,000 hits, virtually all of it unrelated to the technology described here. The first 10 hits is about the Ozzy project, after that unrelated stuff takes over. Put it in between quotation marks "Solar Tower" reduces the number of hits to > 100,000; still mostly unrelated stuff, and again after the first 10 hits other stuff takes over. Adding "Updraft" to the search criterium helps a lot: Solar updraft tower (without quotes) gives > 24,000 hits, and most of the first 100 hits are relevant. "Solar updraft tower" with quotation now gives almost 900 hits (last week it was only 200), and the first 20 or 30 of those are quite relevant. What makes me feel particularly good about it is that the Schlaich paper pops up first, and that is exactly where people should go if they want to find out more about the technology. As said, "Solar updraft tower" is what Schlaich himself calls it, and in view of the fact he has done more than anybody else in developing the technology it is entirely appropriate to follow his lead. Too bad for EnviroMission that their name doesn't show up on the first page; all they need to do is insert the word updraft on the pages, and they will be right on top. Maybe somebody should drop them an email to tell them that.
  About making Solar tower into a disambiguation page: That discussion should be held there; not on this page. I am comfortable about the present situation, because people who go there expecting to find this page are only one click away; there is a disambiguation statement first thing on that page. JdH 17:01, 17 July 2006 (UTC)

i think financial issues are vital to the life of any alternative energy source ... they are always considered when the sourse is dysfunctional... and should also be included when there are some positive prospects... nevertheless company specific info should be centred around that company's page ... i have transferred some new contributions to the enviromission page ... i think the comments in this page which are enviromission specific can be removed from here ... but will leave that to others Flexme 08:23, 15 August 2006 (UTC)

[edit] Financial hurdles

I feel that this article should focus on technical issues; this is not the proper place to go into issues having to do with investment and logistics.
But since the issue has been raised I would like to put in my 2¢ worth.
People should be aware of that fact that recently there has been a significant commitments towards Solar power plants, such as the planned Solar dish facilities in California, see the SCE/SES plant and the SDG&E plant, as well as the Andasol plant in Spain. The Solar Tower project in Australia is still pending.
What do people look at when making decisions like that?
Foremost there is risk and the bottom-line.
In addition to those there may be regulatory issues and other government involvement. These may include things like an Environmental Impact Statement. Or the Government may be prepared to put money into it, for reasons such as creating new jobs, or stimulating new innovative technology.

[edit] Risk

Let’s compare with competing Solar thermal systems, in particular Solar troughs and Solar dishes. The SEGS Solar trough system in California has been in operation for about 20 years, see Projects Deployed , so there is a significant track record in that.
Solar dishes have less of a track record; there is a six-dish pilot plant at Sandia National Laboratory, see Sandia, Stirling to build solar dish engine power plant. The first of those 6 dishes was deployed in 2004, so there are a few years of experience with that. Since these systems scale linearly with the number of dishes it should be possible to make projections on the basis of that.
How does that compare with the Solar updraft power plant? Well, there is the 50kW pilot plant in Spain of course, which was in operation for several years. In Schlaich’s review we read “Plastic membrane roof was used in part of the prototype plant at Manzanares, Spain. It was installed there for comparison with the glass roof. It was cheaper than glass; however, plastic gets brittle with time and thus tends to tear.” In Mills’ paper we read the following “The SBP technology originally used plastic sheet glazing at Manzanares, but this encountered severe structural instability close to the tower due to induced vortices.“ So it appears that the pilot plant in Spain did have some problems. One may expect that those problems have been resolved for the Australian project. On the other hand, that project involves a 1000-fold increase in scale, with an increase of that magnitude previous experience is of limited value, and it is likely that some new unexpected problems may pop up.
In short, the troughs have many years of experience behind them, and it should be possible to make a fairly good assessment of risk. The solar have dishes less experience, and the Solar updraft tower even less

[edit] The bottom-line

The Sunlab has some excellent resources, included many documents which go into the issue of bottom-line in quite a bit of detail. From the PROJECT FINANCIAL EVALUATION document I get the following:

Levelized Cost of Energy (constant 1997 cents/kWh)

Technology	Configuration	1997	2000	2010	2020	2030
	Dispatchable Technologies
Solar Thermal	Solar power tower	--	13.6*	5.2	4.2	4.2
	Parabolic Trough	17.3	11.8	7.6	7.2	6.8
	Dish Engine – Hybrid	--	17.9	6.1	5.5	5.2
	Intermittent Technologies
Wind	Advanced Horizontal Axis Turbines
	- Class 4 wind regime	6.4	4.3	3.1	2.9	2.8
	- Class 6 wind regime	5.0	3.4	2.5	2.4	2.3

So these include projections for the future, assuming further improvement in technology and management.
Bearing in mind that coal fired plants produce electricity at around 4-5 cents/kWh this shows that wind turbines are the only alternative source of energy that is competitive with coal fired plants. The thermal solar systems are not yet competitive, but are expected to become competitive in the near future.
How does that compare with the Solar updraft tower? The Schlaich paper says the following: ‘’Assuming an interest rate of e.g. 12% and a depreciation time of 20 years leads to LEC of 0.12 €/kWh for the 200 MW system. i.e.: Schlaich’s estimate comes out a factor 2 higher for the Solar updraft tower than the estimates the Sunlab has for Solar dishes. One must bear in mind though that these number come from different sources, and different models may have been used, so those numbers may not be directly comparable.

[edit] Environmental impact

As said before, the Solar updraft tower needs 5x more land than the Solar troughs and dishes to generate the same amount of electricity. The land under the canopy will be pretty much turned into a wasteland, unless one resorts to irrigation. However, irrigation will lead to evaporation, and evaporation takes heat away from the power plant, so it will have a negative impact on the conversion efficiency. Apart from the detrimental effect it may have on the structural concrete of the chimney itself. JdH 19:09, 19 July 2006 (UTC)

Regarding the "land" underneath the greenhouse. There's not going to be any "land" as such under the greenhouse. As I understand they've set up some sort of partnership with an american company that is providing some sort of heat-absorbing material for underneath the greenhouse. I would imagine that by the time it is finished, the surface under the greenhouse will be mostly treated or managed in some way or another. At the very least they wouldn't want anything being picked up by the wind and blown into the turbines. Also it's going to be very hot. Finally near the centre it's going to probably be flattened and concreted. There's going to be constant very high winds. So don't think of it as land or ecosystem. Think of it as an industrial area. Adam Kennedy

I agree strongly that economics/investment/logistics should not be discussed in the article. It's OK to record sources of money (goverment grant of $X million under scheme Y to build a plant at place Z), but not compare economics of this technology to some other technology in that or some other place, unless explicitly citing the published analysis by the people who are building it (and noting that may be a primary source) or other qualified analysts. There are too many variables that are opaque to outsiders.

Solar dish power stations are older than you quoted - White Cliffs Solar Power Station was built in 1981, for example.

For example, is the 4-5c/kWh for coal-fired electricity based on plants like Hazelwood and Loy Yang built right on top of the coal mine and close to major consumption, or more remote plants like the one at Port Augusta which has a 250 km train line from Leigh Creek acting as the conveyor belt? Would a company building one expect to depreciate the total cost over only 20 years? I would expect a 50 or more year expected life. The sentence immediately after the one you quote is "When, e.g. by clever financial engineering, an interest rate of 6% and a depreciation time of 40 years is achieved, LEC drop to 0.06€/kWh, i.e. half the formerly calculated cost." which brings Schlaich's estimate back to the same as Sunlab's.

It is not for us to decide whether construction of the Solar Tower Buronga (or any other) is economically attractive or an efficient use of the available resources. This article is about how it would work if it were built.

The land under the proposed canopy s not irrigated now because it is high enough above the Murray River to be not economic to do so. The economic loss of building a 38 km² canopy is probably the feed for about 38 cattle.--Scott Davis ^Talk 02:33, 20 July 2006 (UTC)

Isn't is remarkable that you "agree strongly that economics/investment/logistics should not be discussed in the article", but that at the same time you don't have a problem with one of the first sentences in the article claiming that "Some sources indicate that full scale electricity production is feasible if initial investment and logistical hurdles to create the infrastructure are overcome.", without even taking the trouble to cite those sources? It is in perfect agreement though with the obvious bias of all your edits: Anything that doesn't make the Solar Tower look good is taken out, while at the same time stengthening things that make the Solar Tower do look good.
About interest rates: there is a direct correlation between risk and interest rates. Any investor who takes an impartial look at this will conclude that investing in this enterprise represents a high risk, and will therefore charge a high interest.
Again, your claim that the Tower may last for 50 or more years is not supported by any source whatsoever; indeed I could equally well claim that the thing is not going to last for more than one week, since by that time one of those induced vortices Mills is talking about will destroy it.
btw, it appears that it hasn't dawned on you yet that fragile desert ecosystems should be protected. JdH 18:29, 21 July 2006 (UTC)

Wikipedia does not necessarily expect the intro paragraph to be fully cited if it summarises the rest of the article. I'm happy to remove, change or cite that paragraph as you wish, but I believe it is summarising the Financial feasibility section, and is supported by ref 17 (Waterville), and even 16 (The Guardian). I concede the sentence is presently using weasel words. What do you suggest as a neutral alternative? --Scott Davis ^Talk 16:16, 22 July 2006 (UTC)

What about "Enviromission proposes to construct a full scale power station using this technology.[7]"? I suspect that's advertising Enviromission too much, but it clearly says who and avoids weasel words, yet keeps "proposes", as they haven't started yet. --Scott Davis ^Talk 23:44, 22 July 2006 (UTC)

Sounds fine, and a big improvement over the current version which JdH took exception to - accurate, concise and not speculative. Advertising doesn't strike me as a big issue - the article is mainly about this company, so a reference to their proposal is legitimate. --Singkong2005 ^talk 15:25, 23 July 2006 (UTC)

I don't think I have expressed an opinion here on whether fragile desert ecosystems should be protected, or that the area around Buronga is desert (it's not - it's Mallee). But I don't think a large greenhouse is going to cause any more damage to the ecosystem than digging a large hole and burning whatever is found at the bottom, as is required for a coal power station. Both cause localised environmental damage. Covering the landscape with a large mirror to power some other technology also prevents plants growing underneath. A conventional wind farm appears to create little environmental damage. --Scott Davis ^Talk 16:16, 22 July 2006 (UTC)

The Waterville reference is spam. Clearly, they had firsthand access to information from EnviroMission; they were probably hired by them to prepare this report. It is EnviroMission's POV in disaguise.
And what about the Guardian article? Well, just check the date on it: Monday August 19, 2002; it is about the 1 kilometer high tower that never got built. How wrong can you be?
Further: I strongly disagree that this article is about EnviroMission; we have, for better or worse, a separate article about them. This article is about the technology instead. JdH 17:09, 27 July 2006 (UTC)

Please remember to assume good faith. I think it's very clear that Scott Davis isn't a one-eyed supporter of EnviroMission here, so there's no reason not to be civil. If you disagree with the use of a source, say so, but don't make personal attacks.

that sentence "How wrong can you be?" refers to the news article, not to any one person in particular.
For a different view you may want to look at Zaslavsky D (2006). "Energy Towers". PhysicaPlus Issue No. 7, Online Magazine of the Israel Physical Society (IPS) "The Solar Updraft Chimney uses a solar collector to warm air, which then rises in a tall and large diameter chimney. It is easy to show that the electricity cannot possibly be cheaper than 25-35 cents per kWh, only because there is a use of a collector." JdH 14:23, 30 July 2006 (UTC)

Okay, I misread that. Thanks for the clarification, and the interesting quote. --Singkong2005 ^talk 04:19, 10 August 2006 (UTC)

I said that the article is mainly about EnviroMission - if that's overstating it, then at least they are very significant to the article, as the most high-profile proponents and intending users of the technology - thus a link to them is justified, though if there's a better link then of course use that instead. I don't believe this justifies an argument. --Singkong2005 ^talk 12:42, 30 July 2006 (UTC)