Twice the height of the Empire State - massive solar tower for AZ

Really? Very cool idea, but some of the claims sound downright ridiculous.<p>First, the zero maintenance claim that is touted at least 3 times by the article seems suspicious. You can't really leave anything out in the desert sun and not have to maintain or replace it. Sun will disintegrate a lot of material, not to mention wind and sand. Anybody have any info or insight into what material they are using to create the "greenhouse"?<p>Additionally, the claim that <i>"In fact, because you're creating a greenhouse underneath, it actually turns out to be remarkably good for growing vegetation under there."</i> does not seem to jibe at all with the claimed temperatures ("add in the greenhouse effect and you've got a temperature under your collector somewhere around 80-90 degrees (176-194 F)"). I'm not sure I'm familiar with any vegetation that grows in near 200 degree temperatures.<p>Does anyone have any actual experience with this kind of tech?

<p><pre><code> The Arizona tower will be a staggering 800 metres or so tall - just 30 meters shorter than the colossal Burj Khalifa in Dubai, the world's tallest man-made structure. </code></pre> Is there any reason why this can't be constructed to be 831 meters tall to edge out the Burj Dubai?

For any other Aussies that, like me, vaguely remember the plans for building this near Mildura but can't be bothered watching the video to find out why it didn't happen, the reason cited is a "complete lack of incentives".<p>Sad that something like this couldn't get a dime from the Australian government while the US "welcomed them with open arms" (and, presumably, truckloads of cash).

I love this technology <i>a whole lot</i>, but this is Hacker News so it is worthwhile to think critically about this kind of "press release"-style news posting. This article does a bit of hand waving with the numbers, and, while this is an amazingly cool project, I think that they are overselling its benefits.<p>First, let's get the terminology right. This plant has a capacity of 200 MW. That does not mean that it produces 200 MWh. The formula for converting MW into (annual) MWh is the following:<p>MWh = MWx365x24xCF<p>In the above formula, CF is the capacity factor. Capacity factor is basically the amount of energy that a plant is actually able to produce over the course of a year divided by the total capacity of the plant. Here are some common capacity factors for various industries (taken from a private document, so no sources but this stuff is easy enough to google):<p>* Coal - 65-95%<p>* Natural Gas - 35-65%<p>* Hydro - 25-65%<p>* Solar - 20-35%<p>* Wind - 20-35%<p>* Nuclear - 80%+<p>Capacity factors are never 100% for various reasons:<p>* Plants may need to be taken offline for refueling, maintenance, or inspection<p>* For renewables, the wind isn't always going at full speed and the sun isn't always shining<p>* A whole bunch of other things that I am too tired to list (read the references below, they have some more in them)<p>Now, let's look at this new project, and one of the claims made in this article.<p>According to the article, this plant will be able to provide power for 150,000 homes. According to the EIA, the average household annual energy usage is 10,896 KWh. Given this information and using a more generous solar capacity factor (35%):<p>Number of Homes Powered = (200x365x24x.35) / 10.896 = 56,278 homes<p>Hmm, well that's just a bit less than what the article claimed, so they must be assuming a really amazing capacity factor for this estimate. Let's solve the below for cf and see what we get....<p>(200x365x24xcf)/10.896=150000<p>cf = approx. 93%<p>Look, I'm all for scientific advancement and alternative energy, but can we try to be more sensible than this? This is a highly improbable capacity factor.<p>Documents available from Enviro Mission says that the simulated capacity factor will be more like 50%. When we plug that number into the equation we get about 80,397 homes, which is pretty sensible. However, we have to remember that these are only simulated numbers. There are no similar projects currently available that can be compared to this one, so the actual capacity factor may be either more or less.<p>Note: Please keep in mind that efficiency is a totally different concept from capacity factor. Efficiency is typically used to describe how well a plant transfers from its energy source into electricity^. The capacity of a plant is a number that already incorporates the plant's efficiency. The capacity factor is simply a measure of how much of that capacity is actually used on an annual basis on average.<p>^ I am not an electrical engineer. I am an economist, that is the best definition I can come up with.<p>Disclaimer: I am incredibly tired right now, so if any errors appear in the above posting please send me some coffee so that I can correct them before falling asleep.<p>References:<p>+ <a href="http://www.eia.gov/tools/faqs/faq.cfm?id=97&#38;t=3" rel="nofollow">http://www.eia.gov/tools/faqs/faq.cfm?id=97&#38;t=3</a><p>+ <a href="http://www.solarpaces.org/CSP_Technology/docs/solar_tower.pdf" rel="nofollow">http://www.solarpaces.org/CSP_Technology/docs/solar_tower.pd...</a><p>+ <a href="http://www.enviromission.com.au/IRM/Company/ShowPage.aspx?CPID=1090" rel="nofollow">http://www.enviromission.com.au/IRM/Company/ShowPage.aspx?CP...</a><p><i>Edit: Formatting was all messed up the first time. Forgot to include some additional information. Added clarification on efficiency.</i>

It's a regret that I'm late to the commenting party. This comment won't get seen, so I won't get any feedback.<p>However ...<p>I haven't been able to find out what the upflow airspeed will be. If it's large enough one could wear a winged suit and freefall in the funnel. That would be awesome.

This is just so cool. I'm curious about the local weather impact of something like this. Basically, what these guys are doing is creating a continuous, artificial thermal, the same type you use for flying hang gliders and sailplanes. I'm certain the guys have done the math, but I'm wondering if you won't get cloud formation above the tower due to condensation of the hot air rising through the tower.<p>Meteorological theory suggests that you would definitely get this if the airflow was not contained by the turbines, and cloud formation with the release of condensation heat would cause even more cloud formation which would basically result in a giant, permanent thundercloud above the power plant. This would obviously decrease insolation a lot.<p>Anyone in here who has done any theory on these kinds of projects? I'm just guessing based on my knowledge of gliding that a considerable amount of the energy collected from this power plant actually comes from the temperature differential between not just the solar energy collected directly underneath the tower. It isn't just the fact that hot air rises. Due to decreasing pressure, the air temperature of a mass of air decreases approximately one degree per hundred meters of altitude gained. But if the atmospheric temperature distribution due to meteorological conditions is such that the actual temperature in the atmosphere drops _more_ than one degree per hundred meters of altitude, you have an untapped energy source; any air mass set in motion upwards will actually accelerate instead of slowing down.<p>That we are making large-scale technology to exploit this is so ridiculously cool I have problems expressing it.

Big toy.<p>For one, maintenance will _not_ be low. Wind turbines (and nothing else is used here) do have quite some maintenance costs, and additionally, you need to keep the greenhouse clean.<p>The main problem I see is the capacity. 200 MW peak capacity at 60% efficiency translates to 120 MW peak electric energy. If we assume 50% capacity factor (which I suspect is _very_ generous), we arrive at 60 MWe average output. You would need 15 of these to substitute for a single 1 GW nuclear plant.<p>Big toy.

60%? Darn. I was hoping for better after the hype earlier in the article. Don't large steam plants approach 99%?<p><i>150,000 US Homes</i><p>Is that a lot? I hate to (continue to) be a cynic, but it doesn't sound like a lot.

I don't see it mentioned in the article, but the greenhouse must be colossal. These updraft towers use land far less efficiently than concentrated solar and those don't use land efficiently either.<p>From <a href="http://en.wikipedia.org/wiki/Solar_updraft_tower" rel="nofollow">http://en.wikipedia.org/wiki/Solar_updraft_tower</a><p><i>A 200 MW power plant with the same 1000-metre-high tower would need a collector 7 kilometres in diameter (total area of about 38 km²). The 38 km² collecting area is expected to extract about 0.5 percent, or 5 W/m² of 1 kW/m², of the solar power that falls upon it. Note that in comparison, concentrating thermal (CSP) or photovoltaic (CPV) solar power plants have an efficiency ranging between 20% to 31.25%</i><p>38 square kilometers, these things don't make sense if you don't use the greenhouse for something. Hopefully the wiki is outdated and they have a higher efficiency.

I see two insurmountable problems with this solar tower, in this age of rising environmental concerns and increasing influence of environmental pressure groups:<p>- The base of the tower covers a huge piece of land, which is now home to various desert creatures. Changing their habitat is unacceptable from the environmental protectionists' viewpoint. The precious creatures (probably some endangered species too) would probably die.<p>- Visual pollution. Nobody wants to have ugly structures in his backyard, let alone a half-a-mile-high tower which will be visible from a huge area. It detonates with the natural desert views of Arizona.<p>Because of these two reasons, this solar tower project will face years of litigation from environmental pressure groups, and in the end the project will probably stall.

If anyone was curious about the funding for this (I was), EnviroMission has a press release on their site [1]. <i>"The Southern California Public Power Authority (SCPPA) has taken a call option to purchase the first of two EnviroMission 200MW Solar Tower power stations planned for development in La Paz County, Arizona."</i> It does seem odd, though, that they are building these in Arizona when California has its own deserts.<p>[1] <a href="http://www.enviromission.com.au/EVM/Company/ShowPage.aspx/PDFs/1281-79414176/USPowerAuthorityTakesCallOptiononSolarTower" rel="nofollow">http://www.enviromission.com.au/EVM/Company/ShowPage.aspx/PD...</a>

Even if this type of project only provides a small fraction of the energy we need, it is great to see funding and construction because experience building systems like the one in the article will lead to more effective systems in the future.<p>My wife and I live in Arizona (in the mountains) and we are having solar panels installed on our roof in 2 weeks that will furnish 100% or more of our electricity needs for about 10 months a year (and we will often make a little money back selling back power to our utility company) and cover about 50% of our needs the two months a year that we run our air conditioning.<p>A few friends have been critical of our decision for monetary reasons, and they may be right, but it is something we wanted to do. Also, if prices for energy, food, etc. increase dramatically, then we will break even on costs sooner rather than the anticipated 6 or 7 year time frame.

Wonderful if it works as described! That's quite a bit of power. I'd be very interested to know comparisons in terms of how long a traditional power plant takes to become profitable, and also how much initial investment this project is requiring.

You mean they're actually going through with it? Awesome! I hope it works as well as planned.<p>I'm <i>extremely</i> interested in the aftermath of all this. The building itself is clever and all, but what will the ecological impact be? Wind farms kill birds and bats and there's evidence the sound drives many more off, concentrated solar has a nasty habit of significantly heating the air around the plant and hydro-dams are <i>enormously</i> destructive no matter how you look at it. What's a 1/2-mile-tall heat pump going to do?

Since this seems to work on temperature differentials, could you run it up the side of a mountain? Seems you could get height differences of 5-7k feet in a lot of places with that approach...

This is a question out of pure curiosity, I'm not very well read on these subjects, so please forgive me if this is a dumb one.<p>Is there any reason why this can't be built as an underground structure? If it's working on temperature differentials, shouldn't you be able to achieve a more constant capacity by plugging it into earth where temperatures change less?

The article insists on the plant's low maintenance costs, so this may be a stupid question, but won't the greenhouse* have to be washed regularly of dust? I imagine the accumulation of detritus would significantly impact power production.<p>Edit: I previously had written mirrors. The concept art looked misleadingly shiny.

I wonder what effect this could have on the local climate. Pumping out hot air into cool air at height of 800 metres has got to have some affect.<p>Now if the base is used area is used for growing plants then the air emitted at the top would be moist, which I imagine would cause cloud formation as it meets the cold air.

This brings up an interesting possibility. What's stopping us from engineering these towers on to buildings once the technology is proven?

I've been following Enviromission for quite a while now (maybe since 2001?). I check out their website once a year or so to see how they are going. They have been championing this technology for quite a while.<p>I think it's sad that there are so many people doing back of the envelope calculations and wasting time typing them into Hacker News. There are 100s of millions of dollars involved people. Someone qualified will check the figures. And really it's not rocket science.

Surely building the tower is going to offset a non-insignificant amount of it's CO2 'savings' vs Fossils?

Why does it have to be that tall ? is it because the top end becomes much cooler with more height ?

For just $2trillion, we could build enough of these to supply power for 300m homes!

After I saw this story, I posted it to Facebook and my friend whose a journalist at Arizona's local news station picked it up and did a full blown story. <a href="http://www.azfamily.com/news/Massive-solar-tower-in-Arizona-to-be-worlds-second-largest-building-126157183.html" rel="nofollow">http://www.azfamily.com/news/Massive-solar-tower-in-Arizona-...</a>

The Empire State is New York State: <a href="http://en.wikipedia.org/wiki/Empire_State" rel="nofollow">http://en.wikipedia.org/wiki/Empire_State</a><p>Or did the article headline really mean the empire state BUILDING? <a href="http://en.wikipedia.org/wiki/Empire_State_Building" rel="nofollow">http://en.wikipedia.org/wiki/Empire_State_Building</a>