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Molten Salt-Based Solar Power Plant
Posted by
ScuttleMonkey
on Wed Jan 02, 2008 06:26 PM
from the would-you-like-fries-with-that dept.
from the would-you-like-fries-with-that dept.
rcastro0 writes "Hamilton Sundstrand, a division of United Technologies, announced today that it will start to commercialize a new type of solar power plant. A new company called SolarReserve will be created to provide heat-resistant pumps and other equipment, as well as the expertise in handling and storing salt that has been heated to more than 1,050 degrees Fahrenheit. According to venture capitalist Vinod Khosla 'Three percent of the land area of Morocco could support all of the electricity for Western Europe.' Molten Salt storage is already used in Nevada's Solar One power plant. Is this the post-hydrocarbon world finally knocking?"
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Pretty light on detail (Score:5, Informative)
Re:Pretty light on detail (Score:5, Informative)
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Re:Pretty light on detail (Score:5, Informative)
Heat engines also require a big temperature gradient to do work at high efficiency, which makes using steam directly a harder proposal. Molten salt is well understood in used as a coolant in some types of nuclear reactors, and it works well for this purpose, and that's why it's used.
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Re:Pretty light on detail (Score:5, Informative)
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Not that new... (Score:5, Insightful)
I don't see why you'd lose much efficiency. You'd chose a salt that was molten over the operating range, and no matter what, you cannot exceed the temperature limitations of the other materials you've built the thing from, so that's your design temp. Because of the T(t) smoothing effects, you'd be able to run the generator at maximum efficiency for most of the time. Thus, you can size your machinery to the average capacity rather than the peak available solar input. Not spooling the generator up and down as the sun waxes and wanes is great for efficiency.
For instance, you might pick a salt that has a liquid-solid transition just below your desired T_hot, ensuring even temperature until all the salt solidifies. This has the added benefit that, depending on the expansion characteristics of the salt in question, you have a number of ways to evaluate the remaining generating capacity.
With good insulation, and a fixed installation can be made arbitrarily well insulated, you would lose a lot less energy than storage in batteries, and it scales very well: the larger the installation, the thinner the needed insulation is relative to the total volume.
The main loss would be radiation from the absorption patch. Presumably you'd mitigate this by having some kind of louver or hatch that you could close to insulate that during the night and overcast days. You could also take advantage of the much lower-than-the-sun temperatures, and use a covering that is transparent to visible light, but reflective to lower frequency light. Although there would still be a fair bit of radiation in the visible at reasonably efficient temperatures.
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Nuclear's the future. (Score:5, Insightful)
While I would love to believe some form of solar power would meet the world's needs, it simply isn't feasible with current technology.
We'll probably have wormholes, sexbots and universal prosperity before solar can meet the demand.
Re:Nuclear's the future. (Score:5, Informative)
Much of the argument against solar is one of economics, but a company called Nanosolar has recently produced solar panels making energy more cheaply than coal. [grist.org] "Current Technology" is a moving target.
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Re:Nuclear is not the future.. (Score:5, Insightful)
It requires an absolutely tiny amount of uranium to run a nuclear plant, compared to the 10,000 tons/day that a 1GW coal plant uses. Uranium is rare, but you don't actually need that much *of* it. 95% of the fuel used in fission plants can be reprocessed. Coal producers are chopping off the tops of entire *mountains* in Appalachia;
"Disposal" isn't as big a problem as it's made out to be; reprocessing reduces the amount of waste produced tremendously, and storing a little waste for a time is a whole lot better than *not* storing it and dumping it into the atmosphere, as we're doing with coal.
There are other forms of power generation than nuclear, but at the moment it is the only proven, scalable, clean, and economical alternative to fossil fuels for power generation. Perhaps solar-thermal (as in this article) or geothermal or tidal power or some sort of wind power can be used to carry a lot of the load, but nuclear power is available now, and the only thing lacking is the political will to implement it.
France had that political will, and now they have the cheapest power and the cleanest air in Europe.
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Re:Nuclear is not the future.. (Score:5, Informative)
Um, no. You only need to do that if you're planning on building bombs. (And anyway, gas centrifuges don't heat the uranium to a gas but chemically convert it to uranium hexafluoride before centrifuging.)
There are plenty of reactor designs that run on unenriched uranium, including most of the nuclear power plants in Canada (CANDU) and places to where Canada has sold reactors.
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post hydrocarbon already here (Score:5, Insightful)
It was here 50 years ago with nuclear power. Thankfully, it's finally getting attention again.
Re:post hydrocarbon already here (Score:5, Insightful)
Essentially, proponents of solar power usually like to fantasize about theoretical advances in solar technology, while simultaneously refusing to recognise advances in nuclear technology. As an example, electric cars are usually touted as being CO2 neutral "if the electricity comes from renewables". It is outright obvious that this remains true with nuclear as well, but that is scary and hence rarely mentioned. Similarily advances in electric storage is usually touted as a means of allowing solar to be used for baseload, but rarely is it pointed out that the same tech coudl allow nuclear to deliver peak-energy at increased efficiency by running the plant at its maximum output even when demand is low.
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A few notes and questions (Score:5, Insightful)
2. As you know, nuclear proponents continually ignore the major immediate problem with nuclear power -- waste storage. Nobody wants more glass-encased nuclear waste in their neighborhood, and presently nobody wants some other neighborhood's nuclear waste being transported through their neighborhood. The nuclear industry has got to find technical and political solutions to these problems before society will embrace nuclear as a green solution. I'm not arguing that burning coal or oil is safer or cleaner than nuclear, just that any change to a status quo requires more than a slight or obscured imbalance, which is how the public currently perceives the status quo.
3. What is Hubbart's Peak for uranium? I have no idea, but it surely must have one.
4. Which nations have substantial amounts of useful uranium? What would the balance of power be if those nations became the new Saudi Arabia of energy?
5. Solar off-peak is simply not a problem, not for a long time. Peak demand is highly correlated with sunshine in most of the world -- solar could serve quite effectively as the peaking plant, relying on other types of generation for base load. Electric storage is just not a major issue for solar -- it might become one for wind but it wouldn't be that hard to operate other green energy plants in a negative correlation to wind, ie burn woodchips when the wind isn't blowing, but not when the wind is blowing.
6. That said, plug in cars might change that formulation substantially, since most people would plug in their cars at night thereby adding demand off-peak [and off-sun]. If/when that happens, much of (5) becomes moot and there'd be some shifting of nighttime use [industrial, it's cheaper] to daytime and there'd be encouragement for folks to charge during the day [plug in jacks at car parks] to help keep demand during the day higher, when production due to solar is higher.
7. Ultimately, this doesn't matter. Solar production in the US is well less than 1%. Even at 10% there won't be a necessary substantial change in infrastructures or demand shaping. So, until then, more of every kind of renewable electricity generation is better, and none of it will create challenges. And, of course, nuclear may or may not be greenish, but it is not renewable.
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Re:A few notes and questions (Score:5, Insightful)
4. Ignoring seawater? Australia by far, at 24% of known reserves. Other significant sources include Kazakhstan, Canada, South Africa, Namibia, Brazil, Russia, the US, and Uzbekistan.
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Re:A few notes and questions (Score:5, Informative)
2. It'd be mighty expensive but you could just mix it back with the non-uranium rock you dug out and put it back where you found it... A lot of that waste also isn't waste, it's fissionable material that politically isn't used (because doing so gives you plutonium easily used in weapons).
3. In 20 years we'd run out if we just used uranium in nuke plants for all our electricity. Again allow breeding to plutonium and it turns into 2000 years...
4. The top 5 known recoverable uranium holders are: Australia, Khazakhstan, Canada, USA, South Africa - they make up about 2/3rds of the total. From a Western world perspective, that's a much nicer set then the oil top 5: Saudi Arabia, Canada, Iran, Iraq, Kuwait...
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Re:A few notes and questions (Score:5, Insightful)
And to further elaborate on this: There is this concept called Energy Returned on Energy Invested [wikipedia.org]. (And even more refined indicators).
I have heard this flawed argument against nuclear power so often that it is not really funny anymore.
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Re:A few notes and questions (Score:5, Insightful)
I would encourage you to read up on nuclear power - while a lot of what you are saying is true, it really doesn't capture the reality of the situation.
1. No, nuclear, by itself, is not carbon neutral. However, neither is any other alternative energy. However, when you have the extra electrical power, you can construct "factories" that will scrub the carbon dioxide out of the atmosphere. Now, we might not have the political will to carry it out, but nuclear alone is still way better than what we have now.
2. Fast breeder reactors can run on our current nuclear waste and the waste from those reactors doesn't last nearly as long. So we get to reduce the amount of waste and what's left doesn't last as long. The reason we don't use them is that reprocessing can create weapons-grade plutonium. Again, this is a political issue instead of a technological one.
3. With today's "wasteful" reactors using Uranium-235 it is estimated between 80 and 300 years. If we use breeder reactors so we can use U-238 and Thorium, it can be billions of years at current energy levels.
4. If necessary, fuel can be extracted from sea water making it a moot point.
5. There is also a peak in the evening when everyone turns on lights and TVs. Also, winter means a lot less sunlight in many populated areas so more demand for lighting and heating.
6. Moving power around might help, but there are just too many hours when power is needed and solar isn't available. Also, cloudy days affect production and can't be planned around. Limiting solar farms to areas with minimal cloud cover means increased losses from transport.
7. Nuclear doesn't have to be renewable if we have a few billion years, (or even a few million), years available. If we can assume a technology level that can protect us from extinction due to an asteroid or comet in that time period, we can assume a technology level that can mine the moon, mars or asteroids for more nuclear material.
While nuclear has its problems, they are really political instead of technological. I really hope we get past our fears of nuclear power so we have a chance of keeping our planet habitable for humans.
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Waste salt (Score:5, Funny)
vinod is late to the game (Score:5, Interesting)
I know this is somewhat OT (Score:5, Funny)
But the US Navy refused to build any sodium-cooled submarine reactors. Finally a Congressional committee hauled Admiral Rickover in to a hearing to testify as to why he wasn't making better use of taxpayer's money.
To which he replied "This is what happens when sodium gets wet," and he threw a chunk of sodium into some water.
Re:I know this is somewhat OT (Score:5, Informative)
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Article reads like a business deal. (Score:5, Informative)
Might be better with smart power... (Score:5, Interesting)
The concept of storing the energy as thermal is fine, but reducing the amount of energy swaps is going to be the more efficient way to use the power. The efficiency that they can store energy and re-convert it is going to determine how low a cheap power block can sell for.
Anyway, just a crazy rant.. enjoy,
Storm
salt - water heat exchanger: tricky (Score:5, Informative)
Anything has its chemical activity rise exponentially with temperature (the Arrhenius equation) so as things get hotter, they get more chemically aggressive. Molten glass will dissolve bricks and mortar. Molten sodium and chlorine ions are even nastier -- a sodium ion is a very small object [chemguide.co.uk], only a little larger than hydrogen -- and can diffuse into metals, weakening them and creating leaks.
Re:sun renewable? (Score:5, Funny)
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Re:Still limited by Carnot efficiency (Score:5, Informative)
As for the necessity of high efficiency, it's not neccessary. Even if just a small fraction of the world's urban area was paved with inefficient solar cells, it'd still power the world. I don't care to repeat this calculation yet again (I do it about once a month it seems), but look up China's total urban area (just China's) and do the math with 10% efficient cells (less than NanoSolar's) at, say, 20% coverage and an average 100W/m^2, then compare that to the entire world's electricity demand.
As for what potential efficiency we're capable of, it's actually looking up. But not for CIGS -- for more conventional semiconductor cells, which aren't likely to be cheap enough to panel the world. We're up to a staggering 42.8% now (Honsberg and Barnett) -- and the record keeps growing at a rather surprising clip. And there's more potential for that number to keep growing up to 60-70% or so. There are three technologies pushing this -- the ability to get multiple electrons out of a single photon, the use of integrated beam splitters so that different parts of the cell can be optmized to specific parts of the solar spectrum, and the use of phosphor coatings that can be excited to release photons in a desired energy range. These technologies may not end up running our grid, but they'll be running our satellites, our malibu lights, our self-illuminated highway signs, and so forth.
Back to the initial topic: Just to drive home the point as to how much photovoltaic prices have been dropping, let's put in some historical price points (in non-inflation-adjusted dollars):
1956: Bell solar cell: $300/W .
Early 1970s: Bergman's improvements lowers the price from then $100/W to $20/W
Specifically [unu.edu] (in 1994 dollars):
1976: ~$51
1977: ~$38
1978: ~$27
1979: ~$21
1980: ~$18
1981: ~$15
1982: ~$14
1983: ~$11
1984: ~$11
1985: ~$10
1986: ~$9
1987: ~$8
1988: ~$8
1989: ~$8
1990: ~$8
1991: ~$7
1992: ~$7
1993: ~$6
1994: ~$6
In non-inflation-adjusted dollars, solar prices were at a minimum in the early '00s (~4$/W, if I recall correctly), and rose up until this summer due to supply shortages, when they started to go down again. And with the CIGS companies, the prices can be expected to go down a lot over the next several years. Anyways, I really don't see how anyone can look at the numbers and act like solar hasn't been advancing by leaps and bounds since it was first turned from a laboratory curiosity into a commercial product in the '50s.
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