Twice the height of the Empire State - massive solar tower for AZ • Hacker News Board

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

#91

Post by speleding » Mon, Jul 25, 2011, 11:18 AM UTC

aik wrote: post #52

Spyro7 wrote: post #40

I love this technology a whole lot , 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. First, let's get the terminology right. This plant has a capacity of 200 MW. That does not mean that it produces…

Appreciate the analysis, however I believe you made a fairly significant error with the solar capacity percentage. Unlike other solar power, the cool thing about this structure is that it doesn't specifically require constant sunshine to work effectively being that it works off the temperature differential through the tower, rather than pulling energy strictly from solar panels. Because of this, I would imagine capac…

It still needs a temperature differential to run, which will not be there at night, so the best you could get is about 50%. This is the number that Enviro Mission uses.

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

#92

Post by yaix » Mon, Jul 25, 2011, 11:23 AM UTC

kylec wrote: post #29

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. Is there any reason why this can't be constructed to be 831 meters tall to edge out the Burj Dubai?

Because "who has the longest" contests are... well, stupid.

Seriously, why would you build the tower higher than needed, only to "edge out" some empty building in the Arabian desert? Aren't there... sorry "ain't there" more important things?

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

#93

Post by speleding » Mon, Jul 25, 2011, 11:28 AM UTC

adaml_623 wrote: post #77

serichsen wrote: post #59

Big toy. 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. 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. Y…

Wish I could downvote your post for repetition and for just making up stuff. '200 MW peak capacity at 60% efficiency translates to 120 MW peak electric energy'. This sentence makes no sense. They are building a 200MW plant. That is the amount of electricity it will put out at peak. You made up the number for 50% capacity figure just then didn't you? You did. I just saw you. So your final figure is wrong.

I agree the 200MW is output, so no efficient factor should be added, but Enviromission says the capacity factor is 50%:

http://www.enviromission.com.au/IRM/Company/ShowPage.aspx?CP...

Makes sense, since half of the time it's night...

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

#94

Post by marvin » Mon, Jul 25, 2011, 12:14 PM UTC

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.

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.

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.

That we are making large-scale technology to exploit this is so ridiculously cool I have problems expressing it.

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

#95

Post by [deleted] » Mon, Jul 25, 2011, 12:22 PM UTC

cma wrote: post #44

Eliezer wrote: post #22

Earlier quoted context omitted.

That's not a good sign. I mean, ideally, you'd want the incentive to be, "It produces power cheaper than coal!"

Presumably it could if you factor in coal's carbon externalities.

[deleted]

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

#96

Post by innes » Mon, Jul 25, 2011, 12:23 PM UTC

cma wrote: post #44

Eliezer wrote: post #22

Earlier quoted context omitted.

That's not a good sign. I mean, ideally, you'd want the incentive to be, "It produces power cheaper than coal!"

Presumably it could if you factor in coal's carbon externalities.

What makes you think that?

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

#97

Post by nikcub » Mon, Jul 25, 2011, 1:15 PM UTC

waterlesscloud wrote: post #61

techiferous wrote: post #32

Earlier quoted context omitted.

I think that Burj Khalifa (formerly known as Burj Dubai) should be the tallest for economic reasons. The Arizona tower is simply infrastructure, so its goals are to produce the most energy for the least cost. Adding 31 meters may upset the cost/benefit ratio. Dubai, on the other hand, is a tourist destination, and having the tallest building in the world is good marketing.

I'm willing to bet Burj Khalifa wasn't built tallest for purely economic reasons. I have a suspicion ego was at least a tiny factor.

and then that ego was bruised when they had to change the name to the guy who runs the city next door because he bailed you out

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

#98

Post by jonknee » Mon, Jul 25, 2011, 1:38 PM UTC

Luyt wrote: post #73

I see two insurmountable problems with this solar tower, in this age of rising environmental concerns and increasing influence of environmental pressure groups: - 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 pr…

It's planned for an extremely remote portion of the country. As of the 2010 census, the population density of La Paz county was 4 per square mile. It's quite possible that only a handful of people could end up seeing the thing.

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

#99

Post by truthout » Mon, Jul 25, 2011, 2:02 PM UTC

nixy wrote: post #63

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. 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?

Yeah, it's called geothermal.

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

#100

Post by Andrew_Quentin » Mon, Jul 25, 2011, 2:11 PM UTC

nitrogen wrote: post #88

adaml_623 wrote: post #80

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. 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 wil…

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. I think it's sad that you think that. One of the fundamental qualities of science is that it can be independently verified, and one of the fundamental qualities of hackers is that they don'…

That is fair. I think you missed his subtle point though. For the person giving the millions it matters a lot if the numbers stuck up. For the hacker news bak of the envelope calculater estimates, round ups, even guesses suffice.

I think it is fair to say that while of course one should do the things you mentioned, one also would be wise to trust slightly more the "qulified" person, unless of course they want to go full blow on the matter and engage in thorough deep analysis.