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

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

#121

Post by Detrus »

nitrogen wrote: post #89
Detrus wrote: post #42

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. From http://en.wikipedia.org/wiki/Solar_updraft_tower 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 exp…

When you have an almost comedic overabundance of uninhabited desert, a less efficient but cheaper technology may prove more economically effective. If, one day, the costs of more efficient technologies fall, or if suitable land becomes scarce, then efficiency will become a greater concern.

The whole point of these renewable energy projects is to be considerate to the environment. Covering up the desert, inhabited by tons of species (this is not the Sahara) in a greenhouse is an environmental disaster in a new skin.

Land use efficiency is a concern now for the environment. If renewable technologies have to cover up 60,000+ square miles of land not inhabited by humans, then coal and nuclear are the environmentally friendlier options.

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

#123

Post by juiceandjuice »

dalke wrote: post #83
erikpukinskis wrote: post #67

Earlier quoted context omitted.

Not necessarily. Lets say the lows at the top of the tower are maybe 40 degrees F. They're heating up the base to 180 degrees F during the heat of the day. Whether the thermal gradient ever inverts depends on whether the ambient nighttime temperatures are able to bring that 180 degree thermal mass (concrete? dirt?) down to 40 degrees in the time available before the sun comes back up. You'd have to do the math.

What you say is correct. If there's energy production at night using stored heat then it's pulling out power from the heat reserve and cooling it down. If, say, the system was 10% efficient at producing power directly and put 25% into heat reserves which are 80% efficient at releasing that heat and turing it into power, then yes, the bottom would, excepting rare cases (strange weather?), be warmer than the top. I don…

For working against the inversion, a simple solution would be to implement some venting along the sides and vent at the height of minimum temperature for a maximum differential, assuming that if the inversion was strong enough and the minimum temperature was lower in altitude than the max height of the tower. Yeah, you're gonna lose efficiency, but you'd still be able to generate some power, but I think even with that amount of thermal mass you could still maintain a decent differential I think. Also, southwestern and northeastern Arizona are pretty flat and the southwestern part is much much lower in altitude than Albuquerque.

Also, where from NM are you? I'm from ABQ and Farmington.

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

#124

Post by caf »

ChuckMcM wrote: post #33
ajkessler wrote: post #12

Really? Very cool idea, but some of the claims sound downright ridiculous. 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…

This will be an interesting project. Having lived in Las Vegas for a few years I can certainly see how they expect it to work. However planting grass inside the greenhouse seems a bit much. The plant will be limited by how much heat can be put into the air inside the 'greenhouse' and overall it will be interesting to see how the feed in replacement cool air without creating dust storms and sucking up birds and what n…

Your calculations are out by several orders of magnitude (don't forget that 1 km^2 = 1,000,000 m^2).

200MW at 10% efficiency and 800W/m insolation is 2.5 km^2 (I believe their claimed efficiency is considerably lower than that, though).

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

#125

Post by nitrogen »

Detrus wrote: post #121
nitrogen wrote: post #89

Earlier quoted context omitted.

When you have an almost comedic overabundance of uninhabited desert, a less efficient but cheaper technology may prove more economically effective. If, one day, the costs of more efficient technologies fall, or if suitable land becomes scarce, then efficiency will become a greater concern.

The whole point of these renewable energy projects is to be considerate to the environment. Covering up the desert, inhabited by tons of species (this is not the Sahara) in a greenhouse is an environmental disaster in a new skin. Land use efficiency is a concern now for the environment. If renewable technologies have to cover up 60,000+ square miles of land not inhabited by humans, then coal and nuclear are the envir…

From a strictly pragmatic perspective, I would argue that the loss of some desert habitat in an ecosystem that is not significantly linked with those used by humans for habitation, carbon sequestration, or agriculture is acceptable compared to the damage to higher-value ecosystems caused by air pollution from coal power. This assumes that environmental damage that causes long-term consequences for humans is considered more egregious than environmental damage that has no negative consequences for humans.

Personally, I think a thorium nuclear power plant in an isolated desert is a much more environmentally preferable approach than most renewable power sources.

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

#126

Post by caf »

sliverstorm wrote: post #9
caf wrote: post #5

Earlier quoted context omitted.

99%? No. The Carnot limit is much lower than that for the temperatures at which steam turbines operate. Besides, the thermodynamic efficiency isn't particularly relevant for technologies like this anyway - you're not paying for the input, after all. The efficiencies you care about here are watt/area, energy payback time and, ultimately, $/watt.

thermodynamic efficiency should correlate pretty strongly to watt/area because the device harvests sunlight.

For this technology, but not for the competitors that you'd want to compare them with.

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

#127

Post by Detrus »

nitrogen wrote: post #125
Detrus wrote: post #121

Earlier quoted context omitted.

The whole point of these renewable energy projects is to be considerate to the environment. Covering up the desert, inhabited by tons of species (this is not the Sahara) in a greenhouse is an environmental disaster in a new skin. Land use efficiency is a concern now for the environment. If renewable technologies have to cover up 60,000+ square miles of land not inhabited by humans, then coal and nuclear are the envir…

From a strictly pragmatic perspective, I would argue that the loss of some desert habitat in an ecosystem that is not significantly linked with those used by humans for habitation, carbon sequestration, or agriculture is acceptable compared to the damage to higher-value ecosystems caused by air pollution from coal power. This assumes that environmental damage that causes long-term consequences for humans is considere…

It's better to make coal powerplants run cleaner too. Thorium will require serious effort to develop, a decade perhaps, but sure would be nice to have. Modern uranium is not that bad either.

There was some solar thermal project in California that ran into a lot of problems trying to use the desert land. Old power companies are paying environmental groups to protest those sprawling projects. Divide and conquer those hippies!

High altitude wind is the best source of renewable energy. It's concentrated and takes up airspace instead of land. They're taking their time though.

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

#128

Post by nixy »

Luyt wrote: post #72
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?

The sun doesn't shine underground...

But it shines on the ground, so instead of putting the heat source at the bottom of the cylinder, you put it on top and see temperatures drop as you go further down underground.

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

#129

Post by dalke »

juiceandjuice wrote: post #123
dalke wrote: post #83

Earlier quoted context omitted.

What you say is correct. If there's energy production at night using stored heat then it's pulling out power from the heat reserve and cooling it down. If, say, the system was 10% efficient at producing power directly and put 25% into heat reserves which are 80% efficient at releasing that heat and turing it into power, then yes, the bottom would, excepting rare cases (strange weather?), be warmer than the top. I don…

For working against the inversion, a simple solution would be to implement some venting along the sides and vent at the height of minimum temperature for a maximum differential, assuming that if the inversion was strong enough and the minimum temperature was lower in altitude than the max height of the tower. Yeah, you're gonna lose efficiency, but you'd still be able to generate some power, but I think even with tha…

But there isn't much power there, and we aren't good at extracting power efficiently from lower temperature differentials. I read that wind power goes as the cube of the wind speed, so you really want to maximize this system to extract power during the day time (when the temperature difference and hence wind speed is most), and not the night. Even if it can support 1/2 the wind speed, that's only 1/8th of the power production.

Yeah, ABQ's in the valley so it's probably more prone to thermal inversions. I get the idea (eg, from http://www.arizonensis.org/news/sonorandesertedition/news03_... "PHOENIX, Az. ... The perfume is most noticeable after dark when temperature inversions trap it close to the ground.") that mountains aren't required, and that it's a common feature of deserts, but I wasn't able to track down numbers.

I was in Santa Fe for 8 years. I come back about once a year for my green chile fix. ;)

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

#130

Post by geni08 »

corprew wrote: post #86
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…

On the other hand, this is probably precisely why this is being built in Arizona and not in California.

I agree.
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