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Quantum Mechanic posted:As far as I'm aware ~600C is where gas turbines in a combined cycle (i.e. connected to a traditional steam turbine running off waste heat) become markedly more efficient than a single steam turbine. Oh. You may want to do more research on generation technology, because conventional gas turbines can't be externally fired (they are internal combustion engines, whereas steam turbines are external combustion engines), and therefore are irrelevant in any discussion about running power generation from stored solar thermal energy. Basically, a conventional gas generator is an open cycle, inherently fossil-fuel based technology, while a steam turbine is a closed cycle that just requires some external heat source (and sink) to operate. The efficiency of either generator (indeed, of any generator) is always improved by pushing the temperature of the "hot side" of the heat engine higher. The reason gas turbines in a combined cycle are more efficient than steam turbines is because gas turbines get so much hotter than steam turbines that you can run a gas turbine and use its exhaust (so you've already extracted a significant amount of work from the gas) to run a steam turbine. John McCain fucked around with this message at 13:31 on Apr 2, 2013 |
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Apr 2, 2013 13:26
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TyroneGoldstein posted:I love how the toxic green sludge is coming out of the top of the cooling tower. She should have put the nuclear symbol wearing a witch's hat while stirring it like a cauldron for extra effect. Yeah it's so hilariously overstated. Don't they know benzene is colourless?
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Apr 2, 2013 13:36
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Flaky posted:Yeah it's so hilariously overstated. Don't they know benzene is colourless? That and the fact that there's absolutely no reason why benzene would be anywhere near a pure nuclear power plant (it will show up in real life since if you're dealing in hydrocarbons you can't escape it, and any power plant will have hydrocarbon-fueled backup generators), while it's a universal gasoline additive (and occurs naturally in most fossil fuels)!
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Apr 2, 2013 13:46
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John McCain posted:That and the fact that there's absolutely no reason why benzene would be anywhere near a pure nuclear power plant (it will show up in real life since if you're dealing in hydrocarbons you can't escape it, and any power plant will have hydrocarbon-fueled backup generators), while it's a universal gasoline additive (and occurs naturally in most fossil fuels)! I was making a joke about CSG.
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Apr 2, 2013 13:51
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John McCain posted:Basically, a conventional gas generator is an open cycle, inherently fossil-fuel based technology, while a steam turbine is a closed cycle that just requires some external heat source (and sink) to operate. As far as I'm aware a closed-cycle gas turbine can be run off a heat exchanger? http://en.wikipedia.org/wiki/Closed-cycle_gas_turbine e: seems I was wrong about the efficiency, it's more like 50%. Still a decent gain over a steam turbine?
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Apr 2, 2013 13:52
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Waaaah the Christians are out to get me
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Quantum Mechanic posted:As far as I'm aware a closed-cycle gas turbine can be run off a heat exchanger? http://en.wikipedia.org/wiki/Closed-cycle_gas_turbine This is exactly why I asked you about externally-fired gas turbines, because they're never what people mean when they just say "gas turbine" and are a noncommercial technology at this point. But like I said, there's no obvious reason why there would be a temperature limitation with a closed-cycle gas turbine because there's typically no phase change or anything. You could run one from a 900K heat source or a 500K heat source or a 2000K heat source.
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Apr 2, 2013 13:57
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John McCain posted:This is exactly why I asked you about externally-fired gas turbines, because they're never what people mean when they just say "gas turbine" and are a noncommercial technology at this point. But like I said, there's no obvious reason why there would be a temperature limitation with a closed-cycle gas turbine because there's typically no phase change or anything. You could run one from a 900K heat source or a 500K heat source or a 2000K heat source. As near as I'm aware the compression pressure of the turbine is related to the maximum temperature you can achieve, right? If so, because the thermal efficiency of a closed-cycle turbine vs. compression pressure isn't linear, you can get a marked difference in efficiency with a relatively small jump in temperature. You certainly CAN run one from a 500K heat source, but I don't think in that case it would be as efficient as the steam turbine.
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Apr 2, 2013 14:13
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Since there are a lot of nuclear fission proponents in this thread, could you give me some pointers/links to how the highly radioactive waste products can be safely stored/treated? Not trying to argue, just genuinely interested, and I didn't find the answers on Wikipedia (nor in this thread).
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Apr 2, 2013 14:18
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CombatInformatiker posted:Since there are a lot of nuclear fission proponents in this thread, could you give me some pointers/links to how the highly radioactive waste products can be safely stored/treated? Not trying to argue, just genuinely interested, and I didn't find the answers on Wikipedia (nor in this thread). This would be what you're looking for.
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Apr 2, 2013 14:25
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CombatInformatiker posted:Since there are a lot of nuclear fission proponents in this thread, could you give me some pointers/links to how the highly radioactive waste products can be safely stored/treated? Not trying to argue, just genuinely interested, and I didn't find the answers on Wikipedia (nor in this thread). One thing to remember is that although the waste products are very dangerous, there aren't actually a lot of them. The energy density of U-235 is around 2 million times more than coal, so even if we produced all the worlds electricity from nuclear power, we'd be producing around 2,500 tons of waste a year. That sounds like a lot, but to do the same with coal would result in several billion tons of waste - globally, its not a huge amount. Note that this assumes reprocessing of waste to remove the fission products and recover useful fuel. While there are proliferation concerns over doing this (see above), they can be significantly mitigated by reactor design. What to do with it when we've got it depends on a number of factors - burying it deep underground is a perfectly viable solution engineering wise - we even have an example of how deep waste repositories behave over billions of years: http://en.wikipedia.org/wiki/Natural_nuclear_fission_reactor - turns out that even with water flowing through fractured rock the dangerous elements don't get that far. Vitrification http://en.wikipedia.org/wiki/Vitrification produces an even more stable waste form, so leaching is essentially a non-concern. If that option doesn't appeal, then there are several less-developed alternatives, such as transmutation : http://en.wikipedia.org/wiki/Nuclear_transmutation whereby longer lived elements are turned into shorter lived ones, reducing the amount of time you need to worry about the waste. In short, its largely a solved problem on an engineering and scientific front, the major holdups to disposal are political. (excuse the wiki articles, away from journal access at the moment)
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Apr 2, 2013 14:50
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CombatInformatiker posted:Since there are a lot of nuclear fission proponents in this thread, could you give me some pointers/links to how the highly radioactive waste products can be safely stored/treated? Not trying to argue, just genuinely interested, and I didn't find the answers on Wikipedia (nor in this thread). The general idea is to take long-lived isotopes and put them back into a reactor, where they can be bombarded with neutrons and converted to much shorter-lived isotopes. The problem is that short half-life means it's intensely radioactive - but not for very long. The intensely radioactive waste then rapidly decays into something relatively stable and easy to handle. Right now, we've got tons of relatively low-level waste that will remain radioactive for tens of thousands of years. It's going to be a problem for that long. We need to find something to do with it other than just sit around and look at it and worry about it. As far as long term disposal, the best suggestions I've seen are using them to make a form of glass - not encasing them in glass, literally making glass with them. The radioactive atoms won't easily leach out, it won't flow, it won't decay - it will just sit there, almost forever. They could be buried someplace where plate tectonics will eventually recycle them back into the mantle of the Earth.
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Apr 2, 2013 14:56
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StabbinHobo posted:I think you're right but there are two twists to it. We should be putting money into wind generation. We are currently rounding 3% national production and almost all of it is a result of investment from the last five years. 30% wind generation is a realistic renewable goal. All you have to do is tap the high wind areas off the Delmarva peninsula and create 1-2 HVDC links from PJM to the midwest. Cheesemaster200 fucked around with this message at 15:21 on Apr 2, 2013 |
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Apr 2, 2013 15:05
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StabbinHobo posted:I think you're right but there are two twists to it. Spent nuclear waste in America has generally been spending its free time at the bottom of pools at nuclear plants, letting the high-activity fission products burn themselves out, encasing the lower-activity rods in dry casks, and hoping the US Govt can get a plan together. I'd love to see a campaign get steam to start reprocessing. Nobody talks about it because few care/understand about it.
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Apr 2, 2013 15:12
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Quantum Mechanic posted:As near as I'm aware the compression pressure of the turbine is related to the maximum temperature you can achieve, right? Quantum Mechanic posted:If so, because the thermal efficiency of a closed-cycle turbine vs. compression pressure isn't linear, you can get a marked difference in efficiency with a relatively small jump in temperature. You certainly CAN run one from a 500K heat source, but I don't think in that case it would be as efficient as the steam turbine. This is kind of true but it has very little to do with the working fluid. You can think of it this way: the choice of working fluid is essentially a compromise that reduces various engineering challenges (size of turbine, corrosion, knowledge of properties, desirable/undesirable reactions). But the limiting factor on the efficiency of an engine will be, for the foreseeable future, the temperature at the high-pressure turbine inlet, which is limited by the material you make the turbine from. We've picked water as a working fluid for much of our power generation because it has a number of convenient properties (notably, a relatively high boiling point, which allows us to take advantage of condensation/evaporation heat exchange, as well as allowing us to pump water (which is essentially "free" energy-wise) rather than compressing a gas, among many other properties). But that limits our turbine input temperature because supercritical water does all sorts of nasty things to turbine blades, so we tend to avoid it (although supercritical water has come into use relatively recently as metallurgy has advanced: from a GE publication, "GE designed the world’s most powerful USC steam turbine rated 1050 MW operating at 250 bar / 600 C / 610 C (3626 psi / 1112 F / 1130 F)", which is well above the critical point). Yes, it would be silly to use a non-water working fluid for most applications at low temperatures, but the reason why isn't really efficiency, or not directly (though in a fully-gas cycle, efficiency will suffer considerably from having to compress a gas rather than a liquid).
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Apr 2, 2013 16:14
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CombatInformatiker posted:Since there are a lot of nuclear fission proponents in this thread, could you give me some pointers/links to how the highly radioactive waste products can be safely stored/treated? Not trying to argue, just genuinely interested, and I didn't find the answers on Wikipedia (nor in this thread). Leave it in the transport pods they stuff it in now, plop it on a chunk of uninhabited real estate somewhere, put a fence around it, and forget about it. Nobody's going to steal one of those and they won't break open accidentially.
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Apr 2, 2013 18:12
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John McCain posted:yields an efficiency directly proportional to a particular pressure ratio (which, since pressure and temperature are related, is the same thing as a temperature ratio). See everything I can find is that the efficiency isn't directly proportional, it's logarithmic. John McCain posted:This is kind of true but it has very little to do with the working fluid. But the fundamental difference between steam and gas turbines isn't just the working fluid, it's that one's pressure-based and the other is flow-based? John McCain posted:Yes, it would be silly to use a non-water working fluid for most applications at low temperatures, but the reason why isn't really efficiency, or not directly (though in a fully-gas cycle, efficiency will suffer considerably from having to compress a gas rather than a liquid). Again, every resource I can find indicates that the efficiency v. temperature of a gas turbine requires higher temperature operation to be more efficient. The CSIRO CST research generator uses an air-fed gas turbine and runs at ~1100K, where more traditional solar plants run at about 850. If I get a chance tonight I'll ask one of the BZE engineers about it.
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Apr 2, 2013 21:57
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Quantum Mechanic posted:See everything I can find is that the efficiency isn't directly proportional, it's logarithmic. That's my mistake, it's proportional to the temperature ratio (kind of: η = 1 - T1/T2), so it's log in the pressure ratio because of the power relationship between T and P. Quantum Mechanic posted:But the fundamental difference between steam and gas turbines isn't just the working fluid, it's that one's pressure-based and the other is flow-based? I have literally no idea what you're trying to say here. What exactly do you mean by "pressure-based" and "flow-based"? The turbine stage of gas and steam turbines is exactly the same, except conventional gas turbines run at much higher temperatures, and the expansion limit of steam turbines is limited by the fact that you don't want to expand too far into the saturation curve (need χ > ~0.9 because wet steam will tear the hell out of your turbine). In fact, the entire cycle is pretty drat similar: isentropic compression ---> constant pressure heat addition (for a conventional cycle, by internal combustion; for a CCGT, by a heat exchanger) ---> isentropic expansion ---> constant pressure heat rejection (via exhaust in a conventional turbine, in a heat exchanger for a CCGT) for the Brayton cycle and isentropic compression ---> constant pressure (and temperature!) heat addition in the boiler ---> isentropic expansion ---> constant pressure (and temperature!) heat rejection in the condenser for the Rankine cycle. Quantum Mechanic posted:Again, every resource I can find indicates that the efficiency v. temperature of a gas turbine requires higher temperature operation to be more efficient. The CSIRO CST research generator uses an air-fed gas turbine and runs at ~1100K, where more traditional solar plants run at about 850. If I get a chance tonight I'll ask one of the BZE engineers about it. This might be true because of the dramatic increase in compression work required in the compressor stage if you're dealing with a gas rather than with a liquid (which can be pressurized for very little energy), but the point I've been trying to make is that higher average heat supply temperatures will, as long as you're not breaking material limits, inherently lead to higher efficiency. It's not the fact that you're "able" to switch from a steam cycle to a closed cycle gas turbine, because (as far as I can tell), you can operate a CCGT at any arbitrary temperature range, it's just that because you've been able to boost the turbine inlet temperature by switching working fluids, you've been able to boost the efficiency. But the jump isn't going to be as dramatic as you've claimed because if CCGTs were economical everyone would be replacing their steam turbines with CCGTs.
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Apr 2, 2013 23:46
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John McCain posted:I have literally no idea what you're trying to say here. What exactly do you mean by "pressure-based" and "flow-based"? The turbine stage of gas and steam turbines is exactly the same, except conventional gas turbines run at much higher temperatures, and the expansion limit of steam turbines is limited by the fact that you don't want to expand too far into the saturation curve What I mean is the mechanism by which work is actually extracted from the heat cycles. I get that they're similar but that doesn't mean the same. It seemed that you were arguing before that using a gas turbine is irrespective of the input temperature, where you've just said there that gas turbines run at higher temperatures. John McCain posted:This might be true because of the dramatic increase in compression work required in the compressor stage if you're dealing with a gas rather than with a liquid (which can be pressurized for very little energy), but the point I've been trying to make is that higher average heat supply temperatures will, as long as you're not breaking material limits, inherently lead to higher efficiency. It's not the fact that you're "able" to switch from a steam cycle to a closed cycle gas turbine, because (as far as I can tell), you can operate a CCGT at any arbitrary temperature range, it's just that because you've been able to boost the turbine inlet temperature by switching working fluids, you've been able to boost the efficiency. But the jump isn't going to be as dramatic as you've claimed because if CCGTs were economical everyone would be replacing their steam turbines with CCGTs. Just to check, by CCGT do you mean closed-cycle or combined-cycle? Because closed-cycle might merely be more efficient at 1100K but as near as I can tell combined-cycle effectively can't run at less than that. To be fair I think I've been mixing up terminology as well, so I mostly think we've been talking past each other. Long story short though is as near as I can determine current market tech for concentrating solar wouldn't be able to run combined-cycle generation where with an extra 100-200K it could.
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Apr 3, 2013 00:16
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Quantum Mechanic posted:What I mean is the mechanism by which work is actually extracted from the heat cycles. I get that they're similar but that doesn't mean the same. It seemed that you were arguing before that using a gas turbine is irrespective of the input temperature, where you've just said there that gas turbines run at higher temperatures. Conventional gas turbines (i.e. fossil-fuelled turbines that make up probably 99.9999% of anything you'd ever call a "gas turbine") run at much higher temperatures than steam turbines simply because they are burning fossil fuels, which means they're inherently going to have a very hot combustion chamber. They are impossible (!!) to run from concentrated solar power because they are internal combustion engines. The type of "gas turbine" you'd have to run from a concentrated solar plant would be a closed-cycle gas turbine, an external combustion engine. "Pressure-based" vs "flow-based" is not a distinction that makes any sense. I can't come up with any possible reasonable definition of those terms that makes any sense. It's like if you said to me "Isn't it true that gas turbines are purple-based, while steam turbines are orange-based?". Quantum Mechanic posted:Just to check, by CCGT do you mean closed-cycle or combined-cycle? Because closed-cycle might merely be more efficient at 1100K but as near as I can tell combined-cycle effectively can't run at less than that. Combined-cycle power generation (it doesn't really make any sense to say "combined-cycle gas turbine", even though the term is in wide use) could conceivably run at almost any reasonable output temperature from the gas turbine. You could boil water at atmospheric pressure or near-atmospheric pressure and condense it through a steam turbine to extract some power. The question is not "Will sticking a steam turbine on the output of my gas turbine increase my efficiency?", because the answer is almost always "yes". The question is "Does sticking a steam turbine on the output of my gas turbine make economic sense?". Quantum Mechanic posted:To be fair I think I've been mixing up terminology as well, so I mostly think we've been talking past each other. Long story short though is as near as I can determine current market tech for concentrating solar wouldn't be able to run combined-cycle generation where with an extra 100-200K it could. Like I said, the question isn't really whether you will gain a positive Δη from sticking a steam turbine on the outlet of your gas generator, or whether you can even run one (for really low outlet temperatures you could even switch from steam to e.g. a hydrocarbon-based Rankine cycle if you were really obsessed with efficiency at any cost), the question is whether it makes economic sense to do so. Theoretical efficiency is going to be a smooth function of combustion temperature. And practical efficiency (which is a function of capital outlay vs marginal return) for large generators isn't going to ever see a dramatic jump from 45% --> 60% because it would become economical to add a steam turbine well before that. John McCain fucked around with this message at 00:47 on Apr 3, 2013 |
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Apr 3, 2013 00:45
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John McCain posted:Conventional gas turbines (i.e. fossil-fuelled turbines that make up probably 99.9999% of anything you'd ever call a "gas turbine") run at much higher temperatures than steam turbines simply because they are burning fossil fuels, which means they're inherently going to have a very hot combustion chamber. They are impossible (!!) to run from concentrated solar power because they are internal combustion engines. The type of "gas turbine" you'd have to run from a concentrated solar plant would be a closed-cycle gas turbine, an external combustion engine. I thought from context it was fairly clear that I wasn't referring to an internal combustion gas turbine, did you really need to have that explicitly spelled out? I am a physicist and I have done at the very least basic thermodynamics, you do not have to treat me like an idiot and assume that I don't know how heat inputs work? Just to establish, are you agreeing or denying that CLOSED-CYCLE (since I apparently need to make that clearer) gas turbines have a higher practical efficiency than steam turbines? John McCain posted:"Pressure-based" vs "flow-based" is not a distinction that makes any sense. I can't come up with any possible reasonable definition of those terms that makes any sense. It's like if you said to me "Isn't it true that gas turbines are purple-based, while steam turbines are orange-based?". It was my impression that gas turbines were more reliant on concentrating nozzles for the gas stream where steam turbines were less directed and relied more on bulk pressure, but I was mis-remembering the turbine structure. John McCain posted:Combined-cycle power generation (it doesn't really make any sense to say "combined-cycle gas turbine", even though the term is in wide use) could conceivably run at almost any reasonable output temperature from the gas turbine. You could boil water at atmospheric pressure or near-atmospheric pressure and condense it through a steam turbine to extract some power. The question is not "Will sticking a steam turbine on the output of my gas turbine increase my efficiency?", because the answer is almost always "yes". The question is "Does sticking a steam turbine on the output of my gas turbine make economic sense?". If the term is in wide use you can see why I wanted to clarify, right? And that's why I said "effectively can't run." Yes, if you really want to stick a steam turbine on waste heat from a gas turbine running at 400K you might be able to squeeze a couple of watts out of it. If you want to be achieving that magical 60% efficiency which is the whole point of running a combined-cycle in the first place then as far as I'm aware you basically have to be running your input at 1100K+ and that's what solar's trying to aim for. If we can consistently produce solar towers that concentrate to 1100K with better mirror tracking algorithms, more effective materials or better maintenance practices (since there's diminishing returns on each new heliostat) then we can consistently produce solar towers that can run combined-cycle generation at its peak effectiveness and essentially improve efficiency by an extra quarter to a half above and beyond the gain in efficiency from just making it hotter. John McCain posted:large generators isn't going to ever see a dramatic jump from 45% --> 60% because it would become economical to add a steam turbine well before that. I'm seeing a LOT of interest in building new combined-cycle generators and investing in making the technology cheaper. It might have more to do with the fact that we're growing so obsessed with gas combustion, but it's obviously getting closer to the point, if not already passing it, where running combined-cycle instead of building a whole new turbine makes more economic sense. Quantum Mechanic fucked around with this message at 02:13 on Apr 3, 2013 |
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Apr 3, 2013 02:08
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Quantum Mechanic posted:
This is probably true at some point (although I'm becoming more and more skeptical about it for achievable concentrated solar temperatures as I think about it, since the work penalty associated with gas compression is very substantial, and a well-designed steam turbine can get into the low 40s for efficiency). Basically, though, the point I've been trying to make all along is that I strongly doubt that there is a magic number as far as solar collector temperature goes that suddenly produces an enormous jump in efficiency. Actually, I think the more likely option as we go forward will not be pure solar thermal plants, combined cycle or otherwise, but using solar thermal to substitute for some (but not all) fossil fuel use in more-or-less conventional power plants.
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Apr 3, 2013 04:05
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KaiserBen posted:You can't compare "future solar" with "70s nuclear" (which is what's currently being run in the US) and end up with anything remotely honest. Comparing "today's solar" with "today's nuclear" would make far more sense (eg: PV solar using current best efficiency vs AP1000 reactors). If you want to say "future solar will improve to X% efficiency", use something like a scaled up LFTR for comparison, or any of the Gen IV reactor ideas. The difference is we've been seeing real improvements to real solar power systems deployed in the last few years, while all the talk from nuclear fantasists is about next-gen reactors that don't exist except on paper.
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Apr 3, 2013 04:51
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The Insect Court posted:The difference is we've been seeing real improvements to real solar power systems deployed in the last few years, while all the talk from nuclear fantasists is about next-gen reactors that don't exist except on paper. Like what? Applied where? (Honest question, not sarcasm) The standard i'm using for comparisons is the Andasol plant, has anything better been built in the last 3-4 years?
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Apr 3, 2013 05:00
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Aureon posted:Like what? Applied where? (Honest question, not sarcasm) http://ivanpahsolar.com/ Ivanpah isn't complete yet but it's had first flux (i.e. is operational) and is on track to be completed late this year. IIRC there's also one going up in the UAE?
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Apr 3, 2013 05:31
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Aureon posted:Like what? Applied where? (Honest question, not sarcasm) I don't know anything about solar thermal technologies, but the cost of solar cells per watt has dropped by a factor of two since 2005. It currently is still not low enough now to be competitive without subsidies, but is predicted to be competitive without subsidies in many areas of the US by the end of the decade. That is real improvement.
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Apr 3, 2013 05:47
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CombatInformatiker posted:Since there are a lot of nuclear fission proponents in this thread, could you give me some pointers/links to how the highly radioactive waste products can be safely stored/treated? Not trying to argue, just genuinely interested, and I didn't find the answers on Wikipedia (nor in this thread). I highly recommend several chapters of this book: 
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Apr 3, 2013 06:58
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The Insect Court posted:The difference is we've been seeing real improvements to real solar power systems deployed in the last few years, while all the talk from nuclear fantasists is about next-gen reactors that don't exist except on paper. "We shouldn't build a modern nuclear power plants because we haven't built any modern nuclear power plants yet."
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Apr 3, 2013 07:01
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We see improvements in nuclear reactor design all the time - we just don't see it in the United States. Canada, for instance, is regularly updating its CANDU designs to create a very safe and secure blueprint. The EU has its own standardized designs that are being built throughout the continent. The US is simply disinterested, and is building gas and oil power plants instead.
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Apr 3, 2013 07:13
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The Insect Court posted:The difference is we've been seeing real improvements to real solar power systems deployed in the last few years, while all the talk from nuclear fantasists is about next-gen reactors that don't exist except on paper. The next-gen reactors are old. We have had Gen III reactors since the 90's. Gen III+ reactors are pretty much set to be built today. Gen IV test reactors are being built right now and we are working on the foundations for commercial Gen IV reactors.
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Apr 3, 2013 07:55
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The problem is that the licensing and stuff takes so incredibly long that it takes decades for a new design to be implemented. And then you have to deal with the NIMBY crowd, who manage to shut down reactors before they are even started. If we could streamline that process, for instance with EU or US wide design approval, we can certainly cut that time to say 5 to 10 years. Public opinion needs to change too. Fukushima didn't help in that regard obviously. At some point we need to realise as a people of earth that no, in fact we do not have a perfect power generation technology, renewables can get us a long way there, but we will still need some kind of baseload generating capacity for the foreseeable future, fossil, and especially coal, is the absolute worst way to do that. Maybe one day we can shut down all fission reactors and the world will be better off for it. (Well maybe we need a few for making isotopes)
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Apr 3, 2013 08:57
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Thanks for all the info on nuclear waste and disposal, I think I understand the issues a little bit better now.Gimby posted:The energy density of U-235 is around 2 million times more than coal, so even if we produced all the worlds electricity from nuclear power, we'd be producing around 2,500 tons of waste a year. That sounds like a lot, but to do the same with coal would result in several billion tons of waste - globally, its not a huge amount. Note that this assumes reprocessing of waste to remove the fission products and recover useful fuel. Gimby posted:we even have an example of how deep waste repositories behave over billions of years: http://en.wikipedia.org/wiki/Natural_nuclear_fission_reactor - turns out that even with water flowing through fractured rock the dangerous elements don't get that far. I'm more or less convinced that electricity generation by nuclear fission is not the doomsday technology that some make it out to be. The best way to deal with all the nuclear waste produced till now seems to recycle it in breeder reactors to reduce the total mass (and thus required storage room) and the remaining amount of actinides; is that correct? But to invest in the R&D, reactors and infrastructure required to satisfy most of the energy demand? That just seems wrong to me. I don't want any significant fraction of energy produced by nuclear power by 2050. The faster we get away from nuclear and coal the better, and any large investment in nuclear power diverts money away from developing clean, renewable energy sources and storage methods. Note: I'm not favoring coal over nuclear. QuarkJets posted:I highly recommend several chapters of this book: I'll watch it as soon as I have 75 minutes for myself, which won't be before Saturday  vvvv CombatInformatiker fucked around with this message at 11:42 on Apr 3, 2013 |
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Apr 3, 2013 11:12
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CombatInformatiker posted:I've read 1.5 chapters of that book (Google didn't let me read any further), and it seems to be a little simplistic (multiplying the chance of an accident by it's severity and conclude that there's no increased danger? Come on, you can't be serious!) and clearly biased towards nuclear energy, so it's not something I'm looking for. Watch the video: https://www.youtube.com/watch?v=5BHdsjo-NR4
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Apr 3, 2013 11:31
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CombatInformatiker posted:Well, 2500 tons of highly toxic waste per year is still a lot, and this is even under the condition that none of the fuel is wasted. And some fission products still have a half-life of several decades, so it will take hundreds of years until that stuff is mostly harmless. If it was lead or cadmium or arsenic that was produced as waste it would be hazardous until the sun dies. It needs to be disposed of safely, and the length of time it will be radioactive shouldn't be a significant part of the equation, because waiting it out has never been a practical strategy for dealing with it.
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Apr 3, 2013 11:57
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CombatInformatiker posted:The faster we get away from nuclear and coal the better, and any large investment in nuclear power diverts money away from developing clean, renewable energy sources and storage methods. Thus, the production chain for a windmill is probably going to generate radioactive waste. Even if it does not, it's going to involve environmental damage and human suffering, simply as a consequence of the fact that mining in general is a fairly unpleasant activity. We need to look beyond simple categories ("clean" "dirty") and get into actual cost-benefit analysis. For example, someone posted a "deaths per kilowatt-hour, by energy generation type" chart upthread. IIRC it was pretty shoddy (essentially an unsourced blog post using back-of-the-envelope math) but it's indicative of the sort of mental work that you should do before deciding that "technology X deserves my support while technology Y does not."
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Apr 3, 2013 12:43
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Quantum Mechanic posted:http://ivanpahsolar.com/ Yes, as of last year it was semi-operational but having issues due to the dust storms common to that region. They were putting up barriers (cloth on fencing) to try to control it, but I left the UAE before they were done. It was getting pretty good efficiency numbers IIRC, as long as they kept the mirrors clean (which is a bit harder than it sounds). The Insect Court posted:The difference is we've been seeing real improvements to real solar power systems deployed in the last few years, while all the talk from nuclear fantasists is about next-gen reactors that don't exist except on paper. You mean like the AP1000? The one that's being built right now in several countries (including the US)? While I think the AP1000 is a rather half-assed "next-gen" reactor, it is a significant evolution from the 70s era PWR/BWRs that we currently operate. Some other oddball designs have been demonstrated on research scale; India's building a thorium fueled commercial plant as well and there are several different designs going up in China. Just because you don't follow the news doesn't mean it's not happening.
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Apr 3, 2013 13:43
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CombatInformatiker posted:I'll watch it as soon as I have 75 minutes for myself, which won't be before Saturday Don't forget because it's really good.
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Apr 3, 2013 13:58
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Adenoid Dan posted:If it was lead or cadmium or arsenic that was produced as waste it would be hazardous until the sun dies. GulMadred posted:Always beware of using glittering generalities like "clean," because they tend to conceal nuance. For example, the generators in high-efficiency wind turbines include powerful magnets composed of rare earth metals (such as Neodymium). Industrially-useful rare earth metals occur in ores alongside heavy elements such as Promethium and Thorium, which are radioactive. GulMadred posted:For example, someone posted a "deaths per kilowatt-hour, by energy generation type" chart upthread. IIRC it was pretty shoddy (essentially an unsourced blog post using back-of-the-envelope math) but it's indicative of the sort of mental work that you should do before deciding that "technology X deserves my support while technology Y does not."
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Apr 3, 2013 14:20
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That's to say that we've got a lot of hazardous crap around the world, and some more isn't a tragedy. It's barely a footnote. Also, nuclear proponents panic? what? (Prejudice, sometimes, but we're usually a pretty fact-based crowd)
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Apr 3, 2013 14:26
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CombatInformatiker posted:Well, that's not an argument against production of hazardous waste, not one for nuclear energy. It's an argument against "we should support x because it's not hazardous unlike Nuclear".
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Apr 3, 2013 14:44
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CombatInformatiker posted:I've read 1.5 chapters of that book (Google didn't let me read any further), and it seems to be a little simplistic (multiplying the chance of an accident by it's severity and conclude that there's no increased danger? Come on, you can't be serious!) and clearly biased towards nuclear energy, so it's not something I'm looking for.
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Apr 3, 2013 15:57
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