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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

#61

Post by waterlesscloud »

techiferous wrote: post #32
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?

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.

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

#62

Post by angusgr »

Retric wrote: post #60
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…

IMO the most significant oversight efficiency of around 60% figure which is ridiculously high. Solar towers are vary low efficiency heat engines and have trouble reaching 1% efficiency (yes 1% efficiency ). 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. http://en.wikipedia.org/wiki/Solar_updraft_tower

I read their use of the term "60% efficiency" as what would more correctly be described as a Capacity Factor, in the sense used by Spyro above.

Whether they can actually average 120MW in operation, I don't know.

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

#63

Post by nixy »

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?

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

#64

Post by whatusername »

Eliezer wrote: post #22
gavinballard wrote: post #4

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". 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).

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

Building a new plant is always going to be more expensive than just digging out some more coal and burning it in an existing facility.

Also - we have lots of coal.

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

#65

Post by dalke »

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 also means less power generation in the morning. The thermal inertia in the base means it lags behind the air temperature, so there will be times when the base and top are the same temperature.

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

#66

Post by dalke »

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…

I'm trying to figure out how they would keep enough moisture in the "greenhouse." By definition there's a breeze so it's like using an air dryer on your garden - you would need to provide a lot of water to keep the plants and soil moist. That water has to come from somewhere. In addition, evaporative cooling reduces the amount of power the facility will generate and makes it heavier to lift out. Although the density of the air going through the turbines might compensate.

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

#67

Post by erikpukinskis »

dalke wrote: post #65
aik wrote: post #52

Earlier quoted context omitted.

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 also means less power generation in the morning. The thermal inertia in the base means it lags behind the air temperature, so there will be times when the base and top are the same temperature.

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.

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

#68

Post by erikpukinskis »

dalke wrote: post #66
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…

I'm trying to figure out how they would keep enough moisture in the "greenhouse." By definition there's a breeze so it's like using an air dryer on your garden - you would need to provide a lot of water to keep the plants and soil moist. That water has to come from somewhere. In addition, evaporative cooling reduces the amount of power the facility will generate and makes it heavier to lift out. Although the density…

Yeah, no way plants are going to survive in 180 degree heat with constant breeze wicking away moisture.

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

#69

Post by erikpukinskis »

ahlatimer wrote: post #57
tedkimble wrote: post #43

Earlier quoted context omitted.

So at $750 million a pop, that's a little over $550 billion to power US homes. Or, roughly 50% of the annual budget of the military to power all US homes for 80 years! Clearly back of the envelope numbers, but definitely something to be excited about.

Well, you can't only have these things powering US homes because I can't imagine they work that well at night.

They do actually.

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

#70

Post by erikpukinskis »

Eliezer wrote: post #22
gavinballard wrote: post #4

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". 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).

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

The trouble is no one's ever built anything like this yet, so it's still risky. That's part of why we need government incentives. Once we know it works the incentives won't be necessary, the market will be happy to finance more of them.
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