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Tech That Will Save Our Species - Solar Thermal Power
NoMoreCoal writes "Salon has up a story by Joe Romm, former undersecretary of energy during the Clinton administration, discussing a lesser-known alternative energy solution. It's a technology that (he claims) is ready to provide zero-carbon electric power big, fast, cheap and (most importantly) right now: solar thermal power. 'Improvements in manufacturing and design, along with the possibility of higher temperature operation, could easily bring the price down to 6 to 8 cents per kilowatt hour. CSP makes use of the most abundant and free fuel there is, sunlight, and key countries have a vast resource. Solar thermal plants covering the equivalent of a 92-by-92-mile square grid in the Southwest could generate electricity for the entire United States. Mexico has an equally enormous solar resource. China, India, southern Europe, North Africa, the Middle East and Australia also have huge resources.'" Interesting stuff, even if he does mention the Archimedes Death Ray.
Thats 246 billion square feet.
Thats somewhere between the size of New Jersey and New Hampshire.
Talk about pie in the sky... its more realistic to be talking about microwave power stations in orbit!
... and without the radioactive waste.
www.timcoleman.com is a total waste of your time. Never go there.
Either way, neither of the two are complete solutions like so many want to believe. Relying on the sun for power is not feasible for anything other than base load stuff. When usage starts peaking there is no way to get the sun to send down more energy. A 92 square mile station wouldn't be any more useful than a much smaller station. Solar could only feasibly be a supplement to the grid.
It's nice that people are thinking, but the problem is that the government tends to grant subsidies irresponsibly and places too much importance on any one system. The media plays up the importance of biofuels or wind power, then government pork follows and sends science off on a tangent following a single system. The money should instead be going into research on how to find the best balance of technology. We are going to have use coal for a long time, that's inescapable. There is no one solution that is capable of completely supplanting coal. It's going to require efforts in lots of fields like nuclear, geothermal, and solar. Each has its own characteristics, advantages, and draw backs. It's all about finding the right combination.
I got a catholic block.
My guess would be that it would cost less than the Iraq war. Sounds like a good deal, no?
Before criticizing that type of technology, you really should read the article, you know. You might learn a thing or two.
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Really? There are places on earth that have no access to the sun? Where?
Second, even if it's not a suitable way of generating power EVERYWHERE, who cares? It's renewable and non-carbon emitting, and anything that reduces emissions is a good thing. And for places where it is suitable, the excess power can be sold to other places.
Generating the entire US's energy needs in one central location is only useful if you have a way to transmit the power to where it's needed.
I like the idea of making more, better use of solar energy, but the operation should be more dispersed, or else we're going to need to wait for a revolution in transmission (high-temperature superconductor would be wonderful if we had it).
You see? You see? Your stupid minds! Stupid! Stupid!
Show me some working, power-producing fusion and/or antimatter power plants.
I'll show you some working, power-producing solar-thermal power plants.
Geez. Heating water with solar power really isn't rocket science. The improvements proposed for these power plants are mainly in engineering. On the other hand, we're still working on the science for fusion and antimatter.
I have to question why you think a 92 square mile station wouldn't be more useful. More reflective area = more power.
Should we wait for the 'right combination' to magically appear, or should we start doing what we can right now and learn what works and what doesn't? This tech is dead simple, it's scalable, and it taps a power source that won't exhaust itself for 5 billion years or so.
Never underestimate the power of stupid people in large groups.
The problem with this plan is that it doesn't scale out. It's subject to the Windmill effect, where it's contesting with other uses for land, and eventually, it will be a source of clutter on the landscape.
We need to move our solar power generation to space. Something along the lines of this:
http://en.wikipedia.org/wiki/Solar_power_satellite
Except that this, too, does not scale.
However, if we modified the satellite to act as a go-between rather than as a primary collector, and placed our solar panels in orbit around the sun rather than in orbit around the earth, that would scale out indefinitely. By the time we ran out of room to grow, we'd have a Dyson sphere and be capturing the radiant energy output of the entire sun.
This is what we should do. If we could build such, it would herald a new golden age of mankind.
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When usage starts peaking there is no way to get the sun to send down more energy. A 92 square mile station wouldn't be any more useful than a much smaller station.
So that's like saying if you need more water then it wouldn't be any better to pull water out of the Mississippi with a bucket than a cup because you can't make the river flow any faster?
Also, with solar thermal, you can store surplus heat. Plus there's the nice coincidence that in warm climates energy usage tracks insolation (e.g. airco).
Nuclear is not the magic bullet you seem to think it is. There's still a few major issues I see with nuclear:
* Waste that is toxic for hundreds of thousands of years
* The profit motive leading to corners being cut and safety being a casualty
* NIMBY (not in my back yard)
* Security - these plants are prime targets for terrorism
I know that other countries have made nuclear work (France is the most cited example.) However, those countries have been able to regulate the plants more closely without conservatives jumping all over their governments for 'promoting socialism' and 'over-regulation'. Our plants are (and would be) operated by for-profit companies. More corners being cut = more profit, so you better believe they'll cut those corners.
Never underestimate the power of stupid people in large groups.
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Is there enough material on the face of the earth to construct a Dyson sphere? Oh, and just to ask that question, I had to dig through three layers of ridiculousness. Are you sure you're not after a sci-fi forum?
I hate printers.
I would love to see $600 billion poured into alternative fuels. It would be a boon to our economy, it would be a great opportunity for scientists and engineers, and it would isolate us from oil politics. Not to mention that it is an ethical thing to do, if we care about our planet.
I've been reading and researching renewable energy for some time now. And honestly one of the biggest weaknesses each of these systems has is claiming they are the "magic bullet" to our energy woes.
The fact is one technology will not replace coal fired electricity, just like one technology will not replace oil (and I'm not talking just for vehicles here).
What we need is a more balanced approach combining, solar, wind, biomass, tidal etc... The beauty of combining these technologies into the electrical grid is you can invest less in one particular type and still get the results you want. Diversify is the key.
Germany has already discovered this. They have some towns and villages that leverage a grouping of diverse technologies and produce more power than they require, in turn they sell it back to the grid making the town an energy producer rather than consumer.
Check out these videos on the subject of Germany and renewable resources:
http://www.youtube.com/watch?v=_ikDjh8tDx8
http://multimedia.boston.com/pub/m/19358244/germany_s_solar_experiment.htm
We have to start working collectively if we are to see any real sustainability in the future.
You'd never 'throttle back' free solar power (just like you'd never run a nuclear power plant at less than optimum output -- if you don't use the fuel, it's wasted).
The sun costs $0, so even if the best thing you can do is sell the generated power at $0.00001/kWh to a place 500 miles away you make a profit.
One way to use up excess energy is to pump water upstream above a hydroelectric power station. http://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity
Either way, neither of the two are complete solutions like so many want to believe. Relying on the sun for power is not feasible for anything other than base load stuff.
So this unlimited and completely pollution free* power source can only completely provide for the base load of the entire country (if you make zero attempt to solve the problem)? Oh, how terrible!
Nobody pushing for alternative energy is really that attached to the idea of a "complete" solution. It's the nay-sayers who are always harping on any particular weakness of any one technique and saying "well it can't do everything, what's the point?"
It's nice that people are thinking, but the problem is that the government tends to grant subsidies irresponsibly and places too much importance on any one system. The media plays up the importance of biofuels or wind power, then government pork follows and sends science off on a tangent following a single system.
No the problem is that people naturally stick to the status quo unless whatever the new thing is a "complete solution", so it often takes the government, for better or worse, to get people out of their comfort zone. In some cases, for better, like wind power, which is a fantastic source of power in many places (like west Texas where the farms are going up all the time), and is providing an increasing percentage of electricity, without trying to be a "complete solution". This is exactly what you seem to be asking for -- diversity, using appropriate tech where appropriate -- but it's an example of government pork gone bad?
Not that I believe most of them are subsidized; it's apparently fairly profitable to own a wind farm even without government help.
The money should instead be going into research on how to find the best balance of technology.
That makes no sense. The money required to 1) develop alternative energy sources and 2) do the feasibility studies on where and how they can be deployed and 3) actually build them, is vastly more than the amount of money required to take all those feasibility studies that have already been done and decide which tech to deploy where. "finding the best balance of technology" is pointless if you haven't spent the money to develop the tech, no?
We are going to have use coal for a long time, that's inescapable. There is no one solution that is capable of completely supplanting coal. It's going to require efforts in lots of fields like nuclear, geothermal, and solar. Each has its own characteristics, advantages, and draw backs. It's all about finding the right combination.
Coal is not inescapable, it's not the perfect fuel with no drawbacks in theory, it is itself not a "complete solution" in practice. If you're going to put nuclear on the table, then there's your opportunity to completely replace coal right there.
* In operation of course, not during manufacture, but seriously who cares? Our entire society is built on manufacturing, with the commensurate pollution. If they didn't build thermal solar plants, it's not like nothing else would be built. The comparatively minuscule environmental cost of building the plants is just noise compared to the benefits of running them pollution-free for years.
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Or, you can just store the energy in batteries, and use them at night.
http://www.mhall119.com
Now that you mention that, you could always use the surplus energy to run a desalinisation plant.
There are many alternative concepts for low- or no-carbon energy in the drawers. Hoewever, most of them still have the status of an unproven technology. They are perceived as being driven mostly by tree-hugging nerds who can't do the math, or mad-scientist type of guys who are desperately fighting for a silly idea.
For some this may be true, for some it certainly is not. But to know which tech belongs to which category, a serios research investment needs to happen.
Now imaginge that a country of the size of the United States would invest just the cost of 1 month worth of Iraq war into the development of alternative energys. A research facility town in a desert, funded with anything they need to prove whatever technology promises to deliver clean energy on a larger scale, and invest what is necessary to solve the problem, or dismiss the technology, could probably do more for the world climate and world economy than most other measures.
The Manhattan project was an example of an must-do project where absolutely anything needed to solve a complex technical problem was done, investing any manpower and money possibly needed to solve the task.
Now think of doing the same, but this time not to build the most destructive weapon on the planet, but to get rid of oil as the primary energy source, lose the handcuffs of oil dependency, and save the climate.
Yes, you are right there. -- Another glass of champagne?
Solar is a near perfect power source requiring minimal systems to exploit it, totally renewable and producing no waste. The fact that people in countries with year-round sunshine are heating their water with gas or electricity is ridiculous. The oil and gas people are exploiting their leverage to maintain their monopoly, regardless of the consequences.
Even in the grey UK there are people heating most of their water with solar. I just wish I had the spare cash to set up my own system.
If you reprocess it and burn the actinides it is 300 years for uranium ore levels of radioactivity. Besides, many chemicals we tolerate in other energy systems ( such as photovoltaics ) are toxic indefinitely ( Lithium, Arsenide, Gallium ). If you can tolerate photovoltaics or the molten salts used in solar thermal plants, then nuclear waste is not a problem.
Argument by fear. In the entire history of civilian nuclear power in the US there has been one major accident which didn't kill anyone, this is far better than virtually every other industry in the country. If you were to apply the same irrational argument to other parts of the infrastructure society would grind to a halt.
This is a problem with all energy generation and not specific to nuclear. It applies just as well to windmills and solar as it does to nuclear plants. Furthermore this is a legislative problem, not a technical one.
Not really, the plants are well guarded and the containment structures are designed to survive a direct hit by a large airliner. An attack that would be a danger to a nuclear power plant would likely cause much more damage if directed towards an urban area or other piece of infrastructure ( such as a train station or airport ). Furthermore if terrorist attacks are an issue then a few nuclear power plants are relatively easy to guard and difficult to attack. It is also unlikely a terrorist organization that had the ability to launch a sufficiently fierce attack would pick a nuclear power plant as a target since there are far more vulnerable sites available.
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You're kidding, right?
Right now the sunlight hits the dirt, is partly absorbed and reradiated, and partly reflected.
In the proposed system, the sunlight hits a mirror, is mostly reflected to a collector, at which point it is mostly absorbed and reradiated, and partly reflected.
There will be a potentially significant local effect, and a probably mostly insignificant larger effect. The speed at which the heat is reradiated may be a little different.
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
So is China, North Korea, Iran, and every other country.
the thing that will kill your idea is power transmission. The US together with Canada has a huge well interconnected grid, and yet, it is really 2 grids separated by the Mississippi river with a few interconnects across it. It's then broken down into several smaller grids, like the one that supplies most of the Mid Atlantic states and parts of Ontario Canada. As you might remember, that sub-grid went down about 4 years ago even though the rest of the US/Canada grid was fine. That grid failed because we didn't have enough transmission lines to transmit all the power around the sub-grid when one large transmission line was knocked out due to an accident.
So what's my point, to do what you want would take A LOT more transmission lines. People don't want to build them, and environmentalists would be upset with all the land that would have to be given over to them.
The other problem is transmission loss. You lose power in a wire when you send electricity to it; it literally heats up the wire a bit. This is why you see those big transmission lines sag a lot in the summer, and a lot less the rest of the year. Sure, the summer heat does some to the wire, but most is the extra summer load. Superconductors would help, but we(humanity) can't make ones that work at room temperature; or even close to it. We're getting closer though, and are actually using them in limited places. NYC is currently installing them in parts of the city; along with the expensive cooling system to make the wires work. You also are starting to see them pop up within the sub-stations around the US. I think other countries are starting limited usage of them as well, but I can't recall any examples.
- Mike
Once you've lost your temper, you've lost the argument - Me
Ok so here is the difficulty that the world is having. We want cheap renewable energy so bad that we jump on the band wagon with anything we think might work. Well here's a news flash: NOTHING IS FREE!! I am an Electrical Engineer and I work in the field of Power Systems. In Colorado we have enough wind banks to take care of over 30% of our power consumption if they are all running. Well there is a problem with that...wind DIES occasionally. So unless you want your lights to flicker all day and your computer to constantly shut down because it can't stay on with the power fluctuations, we have to put in other sources of power. Coal and Nuclear can't be turned on and off that fast, so really the only solution is natural gas turbines. These are far more expensive than coal running around $55/MWh. So yeah wind and this new solar thermal are down as low as 6 cents. But guess what happens when a cloud comes over. Either your lights flicker or another generator has to come on to compensate. I was discussing this problem with a dispatcher in the local power company. He said that while wind power was running about $6/MWh, it cost them a total of 1.2 Million dollars in JANUARY to compensate for wind lost. That is 1 month worth of cost. So here is the deal, if you want to go around proclaiming that you have solved all the world's problems with a $0.06/MWh generator, you have to include the $1.2M/month cost that comes along with it. If you don't understand the complexity of the power generation industry then don't pretend like you do.
As for these big mirrors, deserts have plenty of empty space, and could probably use a bit if shade. In inhabited areas this is going to be a bigger problem. There, solar cells are probably easier: simply cover every roof with them, and you've got plenty of energy without sacrifing any space.
Turns out wikipedia even has a page about solar shingles.
That, as I understand it, is one of the advantages of thermal solar over photovoltaic and wind.... the heat stored in the molten salt acts as a buffer (a giant thermal flywheel, if you will), so that if the sun goes behind a cloud for a few minutes (or even a few hours), the plant's energy output doesn't immediately drop. Indeed, that's how the thermal solar plants are able to reliably generate power even during that regular solar outage we call 'night'. Combine that with the cost advantages (no expensive silicon required, just glass and concrete!) and I'd bet your UK tech guy would be a good deal more comfortable with thermal solar than he is with PV.
I don't care if it's 90,000 hectares. That lake was not my doing.
That isn't really a significant concern. There's plenty of empty, sun-drenched space in the desert that nobody wants to use for anything else.
Space-based solar, on the other hand, suffers from a much bigger problem: the cost of launching material into orbit is so outrageously high that space-based solar won't be economically feasible until a major breakthrough (say, a working space elevator) is achieved. And even then -- say, for the sake of argument, that we found a way to launch satellites into orbit for free -- it's not clear to me that the costs of simply maintaining a large fleet of solar power satellites in their orbits wouldn't be significant. After all the analysis, it's likely to be cheaper and easier to harvest solar power on the ground. Yes, you have to harvest more sunlight since its intensity has been reduced by the atmosphere, but on the plus side, when something breaks it's a lot easier to fix it. You also don't have to worry about your power plant accidentally de-orbiting and landing on someone's house...
If we could build such, it would herald a new golden age of mankind
I think that's a great plan for the 23rd century, but we need a plan that will get us through the 21st and 22nd intact, first.
I don't care if it's 90,000 hectares. That lake was not my doing.
Citation, please. Else, don't cite figures.
Citation, please. Certainly the article cited in the OP didn't make such claims. I'm not saying you're wrong, but you'll be a whole lot more convincing if you'd provide some citations.
In 2005, the Congressional Budget Office estimated the cost of the war at $500 billion. That was three years ago. Others put the cost at $1 to $2 trillion in 2006. See this article from The Guardian (UK) for details. If you would like to provide some citations refuting these figures, please do so.
And your basis for this claim is...what, exactly?
From the article cited in the OP, "Commercial projects have already demonstrated that CSP systems can store energy by heating oil or molten salt, which can retain the heat for hours." That covers overnight hours. You'd locate the facilities in areas that typically don't have extended periods of overcast days (e.g., US Southwest, as mentioned in the article). Neither will provide 100% coverage, and so you'll probably still need existing power generation facilities, but they can be scaled back in operation the vast majority of time. What isn't discussed and probably needs to be is whether it is more effective to keep those facilities operating at bare minimum levels vs. come up with some other means to deal with extended poor generation periods.
First, the reference to the 92x92 mile grid says "Solar thermal plants covering the equivalent of a 92-by-92-mile square grid in the Southwest..." You might note that "plants" is plural. So we're not talking a single 92x92 mile plant, but a large number of plants that cover an equivalent area. However, it's unclear how large an individual plant in this scheme would be vis a vis the ones in operation today.
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You bring up an interesting point... If solar power (and other renewable energy sources) are truly as cheap and effective as supporters say they are, then why aren't we using them?
This comment not directed at parent - it's to the world in general: Just shut up and do it already!
If it works so well, why aren't you already paying $0 for your energy bills?!? Here: BUY SOME! Install them, and then (and only then), come back to slashdot and tell us how well they work, and how you don't pay anything for electricity anymore!
I understand our concern about the larger issue of how "everyone else" gets their energy. The discussion about large-scale renewable energy sources is an important and worthy conversation. But what better way to further that goal than to be an example of how this can succeed by just doing it for yourself?
I'm going to price out some solar panels for my house and see if I can make this work right now. In fact, if it *does* work out, maybe I'll look into buying a patch of land and installing a bunch of solar panels and selling the energy. But here's my concern: I'm not the first person to have thought of this. And solar panels aren't exactly a new invention. So why don't we see a bunch of little, private wind and/or solar energy farms? Is it because it doesn't work on a small scale, but does work on a larger scale? I don't buy that - the relationship between the amount of energy collected and the most significant resource that solar energy collection requires (land) is perfectly linear: One 10x10 solar panel optimally collects x KW/h of energy. y 10x10 solar panels optimally collect x*y KW/h of energy. If it's going to work on a large scale, it *must* necessarily also work on all smaller scales.
Like I said, I'm going to look into doing it for myself, but my suspicion is that the reason we're not all already doing this is because it just doesn't work.
The "base load/peak load" thing is a talking point, it's something that people are paid to feed to other people in hopes of creating a self-replicating meme like ladder stickers or the McDonalds coffee spill.
The person you've criticized may be an "innocent" victim of such a meme (aka, a chump) or a paid shill, or even a free agent attempting to protect his oil investments.
But seriously, it doesn't matter if he reads the article or not, he's either brainwashed or corrupt, like most oil shills are these days. The times when one could characterise anti-environmentalists as good people who are merely misinformed (that is, people who can be persuaded of their errors by revealing facts) are long over.
That would be 92x92 miles or 8464sq miles.
For comparison Yellow National park is "only" 3472sq miles.
So by undertaking the largest construction project ever and cover over that much area we can power the US with concentrated solar power.
I can only imagine the environmental impact statement required for such a project.
What's the backup plan for the cloudy days? Tucson,AZ has about 89 of them per year. Lots of local backup required.
All that power generation in one area creates a transmission problem as well.
I'd rather see a Pebble Bed Reactors or some other relatively clean nuclear power with plants spread around the the country.
Here's another thought with centralized power, centralized damage could take the whole thing off line. A ripe target prior to an invasion/attack or just to make us spend the money to build it again. Nope, while I'm not opposed to solar power, this massive project is just plain stupid.
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Most designs for solar thermal in a world that relies strongly on it are for either "combined cycle" plants, where solar either augments or completely replaces another heat source when the sun is out (and are capable of ramping output of the other thermal source up and down accordingly), or have some sort of energy storage system. Pumped energy storage, for example, can cost as little as 3-4 cents per kilowatt hour -- low enough that some places in China are using it in the opposite direction (using existing power plants to pump water at night and then letting it suppliment power during the day). If solar thermal can be made cheap enough, the energy storage issue can be compensated for.
I'm a big backer of solar. Even more than solar thermal, I'm bullish about photovoltaics. CIGS is taking off like there's no tomorrow. There's sliver cells, there's silicon ink, there's dye-sensitized cells, there's super-efficient silicon cells, and on, and on, with each tech advancing by leaps and bounds (just yesterday in the news, dye-sensitized cells got a big boost by the demonstration of 2 1/2 times their previous record sensitivity via nanoscale "popcorn balls"). And on top of this, silicon cells -- the ever-pricy cells that are still growing at 30-40% per year -- should have their prices fall dramatically in the next few years thanks to an upcoming "silicon glut".
High purity silicon is traditionally made from CVD (Chemical Vapor Deposition), a slow and costly process. These plants take a while to build, so the solar boom has completely outstripped supply. To try and catch up for this high-profit raw material, many new plants are under construction and will be coming online soon -- enough that they could possibly create a glut on their own (let alone with all of the silicon-reducing panel techs underway). But now, a couple companies have announced techs for producing high purity silicon in metallurgical processes (I.e., molten silicon, not CVD). Which means far faster plant construction times and far lower product costs. And investors are lining up. So, by all measures, it looks like the silicon shortage will be turning into a silicon glut, which means cheaper panels all around.
*That said*, while I used to feel that low enough cost solar plus pumped storage (or advances in battery storage, which are coming pretty rapidly in their own right these days) could mostly power the future, I'd have to recommend strongly against that. All because I stumbled into this quote that reminded me of something I had not thought of:
"During this year a most dread portent took place. For the sun gave forth its light without brightness? and it seemed exceedingly like the sun in eclipse, for the beams it shed were not clear." -- Byzantine historian Procopius, 536 AD
Volcanoes. Unfortunately, volcanic events major enough to decrease the sun's light significantly are not rare, and some in human history have virtually blotted it out. Even in fairly modern human history -- for example, the Year Without A Summer, 1816, from the 1815 eruption of Mount Tambora, and later, the 1883 explosion of Krakatoa -- volcanic events have caused devastating blocking of the sun's light. When your civilization is relying on solar power, even a regional affect could be catastrophic on its own, let alone combined with poor harvests and the like.
As a consequence, while I feel solar may be a good way to offset our peak loads and even drive prices down, I'd hate to see our civilization become reliant on it. I think EGS is a much more reliable clean, renewable baseload power source. Let's hope it works out to be economical.
I'll BUILD someone to replace you. Some kind of gamma-powered monster, with a heart as black as coal!
Well you're half-right. Photovoltaics can't run overnight without storage, and that alone disqualifies them as baseload in the vast majority of cases. However, in many locations, peak power production from PV tracks peak demand pretty well, so PV's ideal use would be to displace peaking plants that burn fossil fuels. Even where it doesn't track peak use as well it can displace intermediate load plants. Anything that can't run overnight can ever be called a baseload plant, though.
Solar thermal plants store quite a bit of heat energy in their working fluid and do so very efficiently, so they can continue working overnight and are much more promising than PV as a baseload technology. Despite the low cost compared to many other technologies, though, solar thermal is still a little on the expensive side for baseload generation. Plus, the need to focus the sunlight on the working fluid ensures that it is only useful in areas with few clouds.
As it has always been. In the U.S. no one energy source has provided more than 55% of our electricity in a given year for at least 60 years.
It's 92 miles on a side, or 92x92=8464 square miles.
640 acres per square mile and the Nevada plant is 275 acres, so that's 2.3272 plants per square mile.
So we need 2.3272x8464=19698 of those plants, just like the original post said.
This article says the Nevada One plant cost $250 million to build: http://www.technologynewsdaily.com/node/7150
$250 million times 19,698 gives just under $5 trillion dollars in construction costs. Now at some point economies of scale will kick in and save us money, and by most accounts maintaining the solar plant is cheaper than constantly paying for more coal or nuclear fuel. But no matter how you slice it, that's a lot of money.
HTH.
An interesting anagram of "BANACH TARSKI" is "BANACH TARSKI BANACH TARSKI"