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Post by engineerpoet on Feb 6, 2013 11:50:04 GMT 9.5
Judging by the fact that we still don't have a working aircraft reactor That assumes we have been trying to build one. The effort was dropped when ICBMs became accurate enough to be a survivable deterrent. A B747 at cruise burns fuel at about 200 megawatts. At the 22 kW/l figures I'm seeing for MSR concepts, a 200 MW(t) reactor would not be all that large; 9 cubic meters at a density of 3 would only weigh 27 tons. The performance demands go down as the cruise speed is reduced and the wing aspect ratio increased. The longest-lived unstable isotope of aluminum heavier than 27 is Al-28, half-life 2.2 minutes. Typical alloying elements, copper and magnesium, are similarly resistant to neutron activation. Pray tell, what's going to be so nasty about this thing? A ground tug with a shadow shield could move it to parking, and mobile shields around the airframe would allow service; in the fuselage, water tanks fore and aft of the reactor(s) could be filled to provide shielding for the rest of the interior when on the ground. The airframe would have hardpoints for support when it was loaded with shielding water. As long as these things didn't have to ditch (dual reactors and triply-redundant flight systems, maybe?) you could service them just about anywhere. Get a few islands and fly them in monthly for service and fuel changes. I'd much rather go to Australia at 400 knots or even 300 knots than 40 knots. Halfway around the world at 300 knots is only 36 hours. You could beam power to an aircraft to get it to altitude if you didn't feel like burning fuel. Rendezvous with the nuclear towplane, catch the towrope using something like a probe-and-drogue system (with electric power supply to power aircraft systems), and you're good for transoceanic legs. Your fuel reserve needs only to get to the nearest emergency landing site with clear weather. It's not the fuel processing, it's the power to drive it and the reactors to generate it; a system sized to supply our current needs via synthetic fuel plants is going to consume more input power than our current grid. That needs a dedicated power supply (no off-peak rates here). That's the big problem with the Green Freedom idea. There are substantial losses in conversion, roughly equal cost of CO2 capture to hydrogen generation, and so on. Then you have to carry a full load of fuel for takeoff, climb and the first half of the longest leg, with the associated induced drag and its cost in fuel. A reserve fuel supply for a towed aircraft launched on beamed power need be sufficient only for the second half, descent and landing. And, of course, if everything works right you don't need to burn it; you don't care very much what it costs because it's strictly for emergencies. The rest of your useful load is payload, not fuel. I like the idea from a number of angles, I'm just not sure it makes economic sense when you can use a nuclear energy supply directly. If an SOFC/syngas system works as a battery, it would be a great thing. Hmmm. There's an idea, make the SOFC bi-directional. You feed it CO2 and H2O to generate a regular surplus of syngas for high-value products, but its main use is as an electrical power buffer on a daily cycle. You size it for the worst-case day/night demand differential. Converting nuclear power to (heavy, bulky!) chemical energy to be carried long distances loses many of the advantages of nuclear energy right there. Eliminate the middleman, if possible.
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Post by edireland on Feb 6, 2013 21:56:43 GMT 9.5
A B747 at cruise burns fuel at about 200 megawatts. At the 22 kW/l figures I'm seeing for MSR concepts, a 200 MW(t) reactor would not be all that large; 9 cubic meters at a density of 3 would only weigh 27 tons. The performance demands go down as the cruise speed is reduced and the wing aspect ratio increased. The hard part is not generating the heat. That, as you have shown, is rather easy. The hard part is the equipment that will heat the air at high pressure and without causing too much of a bottleneck that you require a huge pressure drop to force the air through it. That is the thing that caused all the trouble. Also you will need more than thermal equivalence since you are only able to provide lower quality heat than a modern gas turbine with its turbine blade cooling equipment. The longest-lived unstable isotope of aluminum heavier than 27 is Al-28, half-life 2.2 minutes. Typical alloying elements, copper and magnesium, are similarly resistant to neutron activation. Pray tell, what's going to be so nasty about this thing? A ground tug with a shadow shield could move it to parking, and mobile shields around the airframe would allow service; in the fuselage, water tanks fore and aft of the reactor(s) could be filled to provide shielding for the rest of the interior when on the ground. The airframe would have hardpoints for support when it was loaded with shielding water. Aircraft are not entirely made out of aluminium. (Indeed in the 787 the aluminium is only 20%, compared to steel at 10%) You will have sources of radioiron, radiotitanium (which is also a minor threat), radiocarbon in huge quantities. I'd much rather go to Australia at 400 knots or even 300 knots than 40 knots. Halfway around the world at 300 knots is only 36 hours. You could beam power to an aircraft to get it to altitude if you didn't feel like burning fuel. Rendezvous with the nuclear towplane, catch the towrope using something like a probe-and-drogue system (with electric power supply to power aircraft systems), and you're good for transoceanic legs. Your fuel reserve needs only to get to the nearest emergency landing site with clear weather. Well even Australia-Los Angeles overland takes 55 hours to the south coast of Timor Leste at 320kph, and if they manage to get 360kph HSR operation to work, that drops to roughly 50 hours. Then about 9 hours on a 40 knot nuclear vessel to Darwin, where presumably you would pick up your transport to wherever in Australia. So 59-64 hours from LA to Darwin, and then a handful more hours to wherever it is you want to go. Its slower to be sure but it doesn't require things like nuclear aircraft... and a US-Timor Leste high speed railway really would be an engineering marvel.... It's not the fuel processing, it's the power to drive it and the reactors to generate it; a system sized to supply our current needs via synthetic fuel plants is going to consume more input power than our current grid. That needs a dedicated power supply (no off-peak rates here). That's the big problem with the Green Freedom idea. Perhaps, but once you electrify everything that can be practically electrified, such as domestic and commercial use of natural gas and similar things. Your electricity demand will tend to double, which rather reduces the disparity. But lets assume we have to have a dedicated reactor train, that would increase the cost of the power to the nuclear breakeven at roughly ~5-6 cents/kWh. But it will reduce capital costs measurably since you now have a nigh on 100% capacity factor. Various studies I have found on the topic indicate that a price of ~$3.50-$3.75/US gal would be achievable. This is effectively in the same order of magnitude as todays fuel prices. (This study assumes a nonzero carbon dioxide capture price but I am unable to determine quite what it is). I like the idea from a number of angles, I'm just not sure it makes economic sense when you can use a nuclear energy supply directly. If an SOFC/syngas system works as a battery, it would be a great thing. Hmmm. There's an idea, make the SOFC bi-directional. You feed it CO2 and H2O to generate a regular surplus of syngas for high-value products, but its main use is as an electrical power buffer on a daily cycle. You size it for the worst-case day/night demand differential. Using it as a battery is such a waste. Enery storage is really rather pointless once you accept nuclear power. It becomes cheaper to build more reactors to deal with peak demand and find some useful way to disperse the excess electricity off peak (See this process and stuff like Solid State Ammonia Synthesis). Converting nuclear power to (heavy, bulky!) chemical energy to be carried long distances loses many of the advantages of nuclear energy right there. Eliminate the middleman, if possible. The advantages of nuclear energy in this case is it is cheap and available in effectively limitless quantities.
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Post by engineerpoet on Feb 7, 2013 10:23:22 GMT 9.5
The hard part is the equipment that will heat the air at high pressure and without causing too much of a bottleneck that you require a huge pressure drop to force the air through it. This is a solved problem. The nuclear turbojet was tested in the 1950's, and the heat exchanger tested by Skylon is capable of far higher performance than necessary for an atmospheric vehicle. Simply making heat exchangers in long folds a la air filters is one way to improve the throughput with minimal pressure drop. The burners in a combustion turbine are not free-flow passages either. Also, there are other ways to extract energy; there is no reason to stick to a strictly air cycle. If a vapor is used to carry heat from the reactor to the engine (heat sink), that vapor might be selected to use a Rankine topping cycle before condensing the fluid and returning it to the reactor. The air flowing through the engine could be removing heat in its primary role, with energy of expansion a secondary consideration. If you need 150 MW of heat dissipation, pumping about 750 kg/sec of air through a heat exchanger with a 200 K temperature rise would do it. The mass-flow of an LMS100 engine core is over 200 kg/sec; if you added some of the fan airflow in a fanjet, you'd get more than enough coolant. Fortunately, a nuclear-powered aircraft would not have any great constraints on this. Thermal efficiency takes a back seat to mission weight. You're doing Mössbauer spectroscopy on aircraft? C-14 isn't generated from C-12, it's made from N-14 via the (n,p) reaction. The solution to all of this is to use boron carbide composites as the structure, armor protection and refractory shielding around the reactors. B-10 + n -> B-11 B-11 + n -> C-12 + e- + ν or 3α + e- + ν LA to Darwin is 7880 statute miles. If you can make 400 kt, that takes 17 hours; at 300 kt, 23 hours. Your rail/water route takes more than twice as long as even the slow plane. The propeller-driven Tu-95 beat 500 knots. (Digging that up, I found this neat Tu-95 video) That's a point, but you still have the large losses in conversions (esp. the heat engine). If you can't meet the demand with the off-peak generation of a nuclear-powered grid built out to the most economical point, you're still going to be paying steep costs at the margin. A 30%-efficient synthesis system (ballpark if CO2 costs 1 MJ/mol) feeding 40%-efficient aircraft engines delivers just 12% of the electric input as useful work. Total US jet fuel supplied in 2011 was almost 3 quads; 10 quads of electricity to make it is about 3000 TWH, about 75% of total US grid consumption. There were over 16 quads of gasoline supplied in 2011. You're not going to build out capacity to supply another 16,000 TWH from our current 4,000 TWH demand to make synthetic gasoline; the idea is nuts. The Ludington pumped storage facility was built BECAUSE OF nuclear power. It makes sense to run a system with high capital and low marginal costs at 100% all the time. If you can use inexpensive storage to level the net demand curve, that can be cheaper than over-building generation. If the round-trip efficiency of an SOFC used as a battery is 50% and its max output power is 75% of the input power, a nuclear-FC system running with its reactor at 100% and FC input power of 40% could vary its net output from 60% to 130%. That might make sense, especially as a dual-use system; the FC would be a money-maker both at demand minimum and at peak demand. Simple-cycle peaking gas turbines achieve 46% (LMS100) or less, and they aren't even carbon-neutral. Don't forget that it's lightweight! But the systems to employ it aren't cheap, which is why I like the idea of putting them on robot aircraft which would fly continuously for a month or more at a time. Once you've made the investment, it should be working hard for you.
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Post by anonposter on Feb 7, 2013 10:54:34 GMT 9.5
Well even Australia-Los Angeles overland takes 55 hours to the south coast of Timor Leste at 320kph, and if they manage to get 360kph HSR operation to work, that drops to roughly 50 hours. Then about 9 hours on a 40 knot nuclear vessel to Darwin, where presumably you would pick up your transport to wherever in Australia. So 59-64 hours from LA to Darwin, and then a handful more hours to wherever it is you want to go. Its slower to be sure but it doesn't require things like nuclear aircraft... and a US-Timor Leste high speed railway really would be an engineering marvel.... Reminds me of the transglobal highway proposal. All you'd need is rail from LA to Alaska, then a tunnel under the Bering Sea to Russia, then rail all the way down to Malaysia or Singapore, then to Java. I'd still prefer a Vactrain.
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Post by edireland on Feb 8, 2013 3:11:57 GMT 9.5
There are far more useful things to use liquid fuels/syngas for than electricity generation.
Once you use the offpeak electricity to make the syngas it is more valuable to use as a chemical feedstock than as a source of more electricity generation.
Pumped storage being constructed to balance nuclear power generation was built before electrolysis cells became a feasible industrial technology again. Solid state ammonia synthesis can eat gigawatts of spare capacity relatively easily and turn peaking demand into baseload demand.
Electrolysis for syngas can easily swamp electricity consumption as you yourself have demonstrated.
It becomes cheaper to simply make more syngas whenever you are not at peak demand than attempt to make pump storage plants.
Pumped storage has weakenesses in unuusal grid load scenarios, whereas every single watt of your nominal generation capacity is available in a system where you overbuilt nuclear reactors for peak demand and then find other ways to disperse the electricity.
(That assumes you can even find sufficient hgih quality pumped storage sites, and I don;t think you can, especially in Europe).
As to nuclear aircraft.... while the vast majority of radiocarbon in the environment currently is produced via the aforementioned nitrogen route.... Carbon-13 will transmute to Carbon-14 under neutron bombardment. (And C-12 will transmute to C-13)
This is a known problem that has come up in the context of Magnox and AGR decommisioning since they can't just burn off the graphite moderator and trap the nonvolatiles.
EDIT:
And while syngas use for chemical production will require additional carbon dioxide taps many processes, like Pruteen production, produce highly concentrate streams of carbon dioxide themselves.
This carbon dioxide can be cheaply recycled back to the process, so you only have to pay for maek up carbon to replace whats in the product.
Carbon in high protein animal feed is rather more expensive than the carbon in carbon dioxide even from the more... energetic capture options.
(Perhaps its fittin that I like huge infrastructure projects...since $53/t excess cost for carbon dioxide from a cement kiln would need huge amounts of excess concrete ordered to make a difference)......
EDIT:
Transglobal Highway, Transglobal Rail (freight and High Speed) and a Transglobal Power Grid are going to be neccesities to move into a glorious brighter futuer.
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Post by trag on Feb 8, 2013 3:37:13 GMT 9.5
Aircraft are not entirely made out of aluminium. (Indeed in the 787 the aluminium is only 20%, compared to steel at 10%) You will have sources of radioiron, radiotitanium (which is also a minor threat), radiocarbon in huge quantities. How much of the carbon in modern aircraft is there because of the use of carbon composites in construction? Carbon composites are used to increase strength to weight ratio and reduce fuel consumption. If the aircraft is nuclear powered, is energy efficiency still such a concern? Mightn't the construction go back to being largely aluminum? Does the weight of the reactor increase linearly with the increase in its power output? The conclusion I'm angling towards is that there may not be much motivation to use carbon composites in a nuclear powered aircraft and therefore there may be very little carbon in its composition.
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Post by engineerpoet on Feb 8, 2013 10:19:08 GMT 9.5
There are far more useful things to use liquid fuels/syngas for than electricity generation. If your CO2 capture from the atmosphere costs over 1 MJ/mol, I don't think that many uses which return it to the atmosphere are on the list. For polymers, yes. But for motor and aircraft fuels? The Navy system appears to require over 1 kWh to get just 2 moles of carbon reduced to (CH2)n. Cycling the syngas back to its raw material avoids the energy cost of carbon capture. It's something like an inefficient flow battery; the bulk storage of energy outside the cell itself is potentially very cheap. The waste of energy in the cycle of capture, conversion and internal combustion means that this is the last place that nuclear power should be spent. Carbon emissions can be reduced more by applying it in just about any other way. Chlorine and caustic soda have been manufactured by electrolysis forever. Despite the hydrogen byproduct of many processes, using it to reduce CO2 to liquid fuels has not been common. It's worth asking why. And quintupling the capital cost of your electric generation system to provide drop-in liquid fuels is a mighty lame use of money. At $3000/kW, the extra 1800 GW of generation would cost $5.4 trillion. A population of 300 million is not going to earn or borrow the $18,000 per capita just to build powerplants. If you built out to the average 450 GW(e) demand, you might have 150 GW in excess of base load. That's only $450 billion. $1500 per capita is feasible. You claimed that storage was not a good match for nuclear power. I proved otherwise with a real-world example; I did not propose pumped storage as the general remedy. The neutron capture cross-section of C12 is in the microbarns. I'm unable to find a cross-section for C13. They're not being very imaginative; piping the gas through a mixture of slaked lime in water would capture the CO2 as calcium carbonate. Pruteen is another one of those high-value products, far better than motor fuels. It's worth spending 2 MJ/mol to make food (providing 3000 cal/day to 300 million people at 25% efficiency is only 170 GW). Given the troubles that have come with globalism, I question your judgement. I think trag may be right: cheap robot aircraft powered by nuclear plants built for simplicity and reliability rather than efficiency may not need any of the problematic construction materials. Radiation damage to fibers and the matrix material may make composites a bad idea in the first place. If you can power your aircraft directly, you don't need to make liquid aviation fuel.
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Post by edireland on Feb 8, 2013 12:29:20 GMT 9.5
There are far more useful things to use liquid fuels/syngas for than electricity generation. If your CO2 capture from the atmosphere costs over 1 MJ/mol, I don't think that many uses which return it to the atmosphere are on the list. I doubt this figure of 1MJ/mol... since that leads to 22MJ/kg of carbon dioxide.... or 22GJ/t of carbon dioxide..... I just demonstrated in the last page that running a cement kiln only requires 4.8GJ/t of carbon dioxide produced from the calcining of calcium carbonate. Are you really saying digging up limestone and then dumping the clinker into the sea to remove the carbon dioxide from the atmosphere by oceanic dissolution is going to cost 15GJ/t? In reality at most we are looking at 200kJ/mol. At most. For polymers, yes. But for motor and aircraft fuels? The Navy system appears to require over 1 kWh to get just 2 moles of carbon reduced to (CH2)n. Cycling the syngas back to its raw material avoids the energy cost of carbon capture. It's something like an inefficient flow battery; the bulk storage of energy outside the cell itself is potentially very cheap. At the shown 4.8GJ/tonne value for the capture of carbon dioxide.. (ie. assigning no value to the absurd amounts of cement clinker being turned out by all those furnaces in the brute force solution) the cost of carbon capture would be ~$67/t. That adds approximately 17 US cents to the price of a litre of hexane (I am using that as a stand in for gasoline in this context)..... which is something like 60 cents/US gallon. Carbon dioxide price is irrelevant. What matters is energy cost of the syngas reduction, which can be shown to be relatively low compared to current prices of gasoline even using baseload electricity costs (not off peak). The waste of energy in the cycle of capture, conversion and internal combustion means that this is the last place that nuclear power should be spent. Carbon emissions can be reduced more by applying it in just about any other way. You complain about capital intensive solutions and yet you don't offer a way around the huge demand for motor fuels.... EVs and PHEVs are likely even more capital intensive. Chlorine and caustic soda have been manufactured by electrolysis forever. Despite the hydrogen byproduct of many processes, using it to reduce CO2 to liquid fuels has not been common. It's worth asking why. Chlorine and Caustic Soda also don't have the huge uses that carbon based produts have. Production of them has saturated all reasonable markets. There are also numerous other sources of those products. (Hell, I have just thought up another source of carbon dioxide... dig up those huge Trona deposits in Wyoming and Calcine them, then dump the Caustic Soda in the sea......). And the reason that reduction of carbon dioxide to liquid fuels has not been common is because we have this stuff called "Coal"... it is available at $50-70/t for the really good stuff and can easily be converted to liquid fuels with breakeven costs in the range of $50/bbl. And for areas where there is little coal they tend to have huge oversupplies of "natural gas" with a similar capability to convert into liquid fuels for similar price. Why spend the limited capital available to financiers on fuel that can just break even today when you can spend it on fuels that can make ridiculously enormous profits. And quintupling the capital cost of your electric generation system to provide drop-in liquid fuels is a mighty lame use of money. At $3000/kW, the extra 1800 GW of generation would cost $5.4 trillion. A population of 300 million is not going to earn or borrow the $18,000 per capita just to build powerplants. I think you don't understand just how high value the motor fuels market is. Currently the US alone spends something like $45bn every month on Gasoline alone.... that is something like $540bn every year. So that "absurdly expensive" reactor infrastructure is only worth ten years worth of gasoline production. And the reactors will all tend to last 60 years at the least. At the 70% electrical efficiency achieved by high temperature syngas electrolysis cells a tonne of gasoline comes out with something on order of 15.8MWh of electricty. Once you note that gasoline is a value added product compared to ordinary oil (non taxed prices come out in the region of $1100/t) you can see how it can produce production prices similar to todays. You claimed that storage was not a good match for nuclear power. I proved otherwise with a real-world example; I did not propose pumped storage as the general remedy. It was a "good match" a long time ago when the last major run of pumped storage plants was built. Technology has now moved on in the last 30 years. We have far more efficient ways to use our electricity than use it to pump water up hills and then let it run down later. If the value of the electricity you can sell later through your ~70% efficient system is less than value added ammonia production you acn make with the electricity now, you shoudl build more reactors and use the off peak electricity for ammonia or syngas instead. They're not being very imaginative; piping the gas through a mixture of slaked lime in water would capture the CO2 as calcium carbonate. So now you have a huge mound of radioactive calcium carbonate that weighs something like 7-8 times what the pile of graphite did and is probably less resistant to chemical attack. What do you do with it? (Its going to take isotope seperation for carbon becoming practical for any headway to really be made on that front, probably laser isotope seperation of fluorocarbons). Pruteen is another one of those high-value products, far better than motor fuels. It's worth spending 2 MJ/mol to make food (providing 3000 cal/day to 300 million people at 25% efficiency is only 170 GW). Indeed it is a high value product, but Pruteen is only rated as animal feed as it lacks the palatable product features of say Quorn. Although GM could produce a version of quorn that was capable of munching methanol.... Pruteen would probably consume something like 14MWh per tonne of finished product, which translates to something roughly on order of $700/t of electricity at 5 cents/kWh. Unfortunately the feed that it is most comparable to on a weight/weight basis is whole soybeans, which only have a price of roughly $560/t at the present time. Essentially pruteen is a lower value product than gasoline at the moment and can only be made viable using off peak electricity. Given the troubles that have come with globalism, I question your judgement. Globalisation is not yet complete. When it is truly complete there will be little or no difference in the Purchasing Power Parity index values for any country on earth. Every country will have first world levels of wealth. We are not yet there yet, we are in the rather depressing transistion where lots of rich people get even richer and western workers are squeezed while Chinese adn African workers catch up. I think trag may be right: cheap robot aircraft powered by nuclear plants built for simplicity and reliability rather than efficiency may not need any of the problematic construction materials. Radiation damage to fibers and the matrix material may make composites a bad idea in the first place. If you can power your aircraft directly, you don't need to make liquid aviation fuel. But nuclear powered vehicles are never ever ever ever ever cheap. They cost huge amounts.
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Post by engineerpoet on Feb 8, 2013 14:33:20 GMT 9.5
I doubt this figure of 1MJ/mol... since that leads to 22MJ/kg of carbon dioxide.... or 22GJ/t of carbon dioxide..... I got that straight from the figures in the Navy paper. 6.22 volts @ 0.94 amps, 140 ml/min @ 0.1 mgCO2/ml, 95% recovery. You do the math. Even at 1 MJ/mol of CO2, the electrolysis of water at 80% efficiency costs about the same amount of energy to produce the hydrogen to reduce it. 286 kJ/mol H2, 3 moles required for CO2 + 3 H2 -> CH3OH + H2O. The CO2 capture only doubles the electric input. On a carrier-based fuel factory, the ability to pull CO2 from the sea would be worth the overhead. As a general climate fix... don't kid yourself. I've seen figures as low as 44 kJ/mol, but not using electric acidification of seawater. IIRC the "Green Freedom" concept proposed potassium carbonate absorbers in the intake air for cooling towers. I'm sorry, when you say the price of anything is irrelevant you're off into cloud-cuckoo land. Small variations (esp. around "trivial") may be irrelevant, but not price in general. Then you beg the question, why isn't gasoline being produced that way? Even Green Freedom calculated a production cost in excess of $4/gallon, IIRC. Ah, here we go: $4.60/gallon. That's at the plant; transportation, taxes and profit are extra. Oh, and cost overruns! Proving that your idea is broken does not obligate me to fix it. If an idea is wrong, it's wrong. As it happens, I have a very simple way around this demand. Nuclear electric replaces coal and natural gas in powerplants, and electricity replaces most domestic and commercial NG consumption. The displaced NG is used to displace petroleum in the short term (10-30 years) via CNG and LNG motor fuel. Batteries are improving steadily; even at today's price/performance it won't take much of a fuel price increase to make PHEVs competitive for many uses. As Ulf Bossel will tell you, electrosynthetic gasoline suffers from the same problem as electrolytic hydrogen for fuel cells: it can't compete with its own energy source. If you can make gasoline at $4.00/gallon electricity cost and 50% efficiency, it means the juice costs about 6¢/kWh. But at 300 Wh/mile, a mile's worth of electricity costs 1.8¢ vs. 16¢/mile in a 25 MPG ICEV. Driving 10,000 electric miles a year, the difference is about $1400/year. You can amortize a $5000 battery pretty quickly at that rate. Red herring again. You said that electrolysis had gone out of style, more or less. Just admit you were wrong, it's easier. Yet nobody's doing it. Even Sasol has dumped coal gasification for steam-reformed natural gas as a feedstock. Rentech's gears shifted similarly a few years ago. But if you're going to use NG as a feedstock, why not use it directly as LNG/CNG (or Hythane, with H2 to improve the flame speed)? You can double your well-to-wheels efficiency and eliminate massive chemical plants with all their costs and emissions. The concentration on "everything must convert to gasoline" is some kind of mental disease. You mean, like converting NG that costs $3/mmBTU at the Henry hub to LNG that competes head-to-head with $30/mmBTU ULSD at truck stops? I think you don't understand just how long I've had my head in this stuff. The USA has long been burning between 130 and 140 billion gallons of "gasoline" (including E10-E85) each year (almost exactly 9 million bbl/day in 2010). It still makes little sense to convert mass quantities of electricity to gasoline. Consider the massive technological risk involved: one advance in something like metal-air batteries, and the investment in the chemical plants is suddenly worthless. Okay, consider an alternative scenario: we wire our highways to eliminate 90% of motor fuel demand with electricity supplied directly to vehicles. Trucks use overhead wires, light-duty vehicles use capacitive coupling to their steel tire belts from plates in the roadway. About 7 years ago I calculated that the average power delivered from US motor fuel consumption was in the neighborhood of 180 GW. Assume that something like the SOFC/syngas battery is used to buffer off-peak production to supply the rush-hour demands, and the average efficiency is 50%. Supplying 360 GW continuous at $3000/kW is $1.08 trillion, a fifth of the synthetic gasoline scenario. It also eliminates the chemical plants and all the air emissions and most of the noise of combustion engines. Which would you rather have? Wrap it in a torpedo-shaped polyethylene sheath with fins, and drop it in an oceanic subduction zone. Maybe ballast it with some iron to get a good descent speed, bury it nicely when it hits sediment. That's what I thought, a long time ago. I've learned that the rich are just playing the rest of the people off against each other. Nations rise as mercantilists and fall as free-traders. Yet the USA hasn't built a conventionally-powered aircraft carrier since when? Massive quantities of jet fuel aren't cheap either. A Dreamliner costs about $120 million. The single biggest line item in the operation of an airliner these days is fuel. If you can remove the factor of fuel, and also eliminate the reduction of cargo capacity with length of flight, there's potential for both saving huge amounts of money and adding revenue. Imagine the trans-oceanic airlines which bought fleets of nuclear towplanes and passenger/cargo "motorgliders". War in the Middle East? "Oh, great, we'll have business flocking to us while our competitors go out of business! Place some more orders, we'll have the new aircraft coming on-line about the time that demand rebounds." It would be a one-way ratchet, with the elimination of petroleum from the segment at the end.
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Post by anonposter on Feb 8, 2013 21:48:11 GMT 9.5
How much of the carbon in modern aircraft is there because of the use of carbon composites in construction? Probably most of it. Carbon composites are used to increase strength to weight ratio and reduce fuel consumption. If the aircraft is nuclear powered, is energy efficiency still such a concern? A nuclear powered aircraft is so close to the border between possible and not possible that it'd need all the help it could get. Every gram not used in structure is an extra gram that can go towards more shielding or payload. Does the weight of the reactor increase linearly with the increase in its power output? I suspect the required shielding mass would increase slower than power output (based on the square cubed law of scaling) which would argue for making it as big as possible if you were to actually build one (synfuels do look like a better idea).
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Post by engineerpoet on Feb 9, 2013 0:34:13 GMT 9.5
A nuclear powered aircraft is so close to the border between possible and not possible that it'd need all the help it could get. Actually, no. The measured power density of reactors built long ago is sufficient to run an aircraft, so long as its performance parameters are not extreme. Slowing down 100 knots would be death for a bomber, but cargo and passenger aircraft have been doing it with no design changes at all as fuel prices have gone up. If aircraft were designed for the lower speed, they'd be even more efficient. As I calculated before, a B747 at cruise burns fuel at a rate of about 200 MW(th). A reactor with a rather low power density of 22 kW/l would only need 9 cubic meters of core to generate 200 MW; at a density of 3, the core would weigh 27 tons. Gross lift-off weight of a B747 can be over 450 tons; the fuel load in some models can be 63,000 gallons, over 400,000 pounds. The price I'm seeing for Jet-A is around $5.50/gallon. If the airlines can get it for $4, that's $27 per GJ. On a 15-hour LA-Darwin flight at 450 knots, 180 MW of average Jet-A consumption would cost just shy of $270,000. Consider the nuclear-powered towplane pulling at 400 knots. It would cruise from LA to Darwin in 17 hours. If its reactors output 200 MW and cost $2000/kW(th), the reactors would cost $400 million. They'd recoup this in about 1500 flights; at 1 flight per day, it would take just over 4 years. If the towplane could fit in some side trips for the LA-Darwin run, such as Darwin-Taipei and back before picking up the Darwin-LA return flight, it could recover its cost even faster. A robotic towplane would carry no payload and need little shielding. Payload and passengers on the aircraft being towed would be shielded by atmospheric absorption and 1/r².
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Post by edireland on Feb 10, 2013 5:24:41 GMT 9.5
I doubt this figure of 1MJ/mol... since that leads to 22MJ/kg of carbon dioxide.... or 22GJ/t of carbon dioxide..... I got that straight from the figures in the Navy paper. 6.22 volts @ 0.94 amps, 140 ml/min @ 0.1 mgCO2/ml, 95% recovery. You do the math. You may not have noticed... but the United States Navy doesn't have access to billions of tonnes of limestone while its in the middle of the Pacific Ocean steaming at 30 knots. We have access to far lower overhead capture systems than the USN does at sea, on land we are not really mass or volume limited and we have acess to the aforementioned limestone/trona. Even at 1 MJ/mol of CO2, the electrolysis of water at 80% efficiency costs about the same amount of energy to produce the hydrogen to reduce it. 286 kJ/mol H2, 3 moles required for CO2 + 3 H2 -> CH3OH + H2O. The CO2 capture only doubles the electric input. On a carrier-based fuel factory, the ability to pull CO2 from the sea would be worth the overhead. As a general climate fix... don't kid yourself. But the figures you are using aren't applicable outside of the mass-limited high seas scenario. Attack it using actual figures if you are going to. I've seen figures as low as 44 kJ/mol, but not using electric acidification of seawater. IIRC the "Green Freedom" concept proposed potassium carbonate absorbers in the intake air for cooling towers. Not really applicable since I can't think of many processes that will still require large cooling towers if we accept the most efficient siting of nuclear plants in almost all cases is in a coastal environment. I'm sorry, when you say the price of anything is irrelevant you're off into cloud-cuckoo land. Small variations (esp. around "trivial") may be irrelevant, but not price in general. Alright then... it is effectively irrelevent in this case since it is such a small fraction of the cost of the fuel once you use reasonable assumptions rather than assuming we need a plant that is of sufficient output to be fitted onto an operational warship that must maintain hundreds of sorties by high performance jet aircraft every single day. Then you beg the question, why isn't gasoline being produced that way? Even Green Freedom calculated a production cost in excess of $4/gallon, IIRC. Ah, here we go: $4.60/gallon. That's at the plant; transportation, taxes and profit are extra. Oh, and cost overruns! That is 4 years ago, electrolysis equipment has come a long way since. They are proposing carbon dioxide hydrogenation rather than co-electrolysis of water and carbon dioxide in a single reactor. This has been shown to have various advantages in efficiency terms. This is an extremely fast moving field. As it happens, I have a very simple way around this demand. Nuclear electric replaces coal and natural gas in powerplants, and electricity replaces most domestic and commercial NG consumption. The displaced NG is used to displace petroleum in the short term (10-30 years) via CNG and LNG motor fuel. So you propose to build an effectively brand new motor fuel distribution infrastructure from scratch, only to then obsolete it in ~15-30 years time? With methanol synthesis and liquid fuel conversion most of the very expensive hardware (read reactors and electrolysis equipment) can be repurposed fairly easily to other things, such as the aforementioned pruteen and plastics production. (I expect plastics consumption to keep increasing now that we have access to polymer based composites with rather impressive characteristics). CNG and LNG also make really bad motor fuels. There is a reason that excess natural gas is largely going to end up being converted to liquid fuels instead of being used directly. Using the existing distribution infrastructure is a rather large benefit. Batteries are improving steadily; even at today's price/performance it won't take much of a fuel price increase to make PHEVs competitive for many uses. And yet you propose to build an enormously expensive fuel distribution infrastructure almost from scratch? (And before you say that there are CNG/LNG filler stations available now, they don't supply a significant fraction of total motor fuel consumption) As Ulf Bossel will tell you, electrosynthetic gasoline suffers from the same problem as electrolytic hydrogen for fuel cells: it can't compete with its own energy source. If you can make gasoline at $4.00/gallon electricity cost and 50% efficiency, it means the juice costs about 6¢/kWh. But at 300 Wh/mile, a mile's worth of electricity costs 1.8¢ vs. 16¢/mile in a 25 MPG ICEV. Driving 10,000 electric miles a year, the difference is about $1400/year. You can amortize a $5000 battery pretty quickly at that rate. Electrolytic hydrogen's primary problem as a transportation fuel is its absurdly low density, even if you handle it as a cryogen. Your battery, assuming its based on any existing chemistry (apart from maybe Na-S... and that would be insane even by my standards) will loose capacity too quickly for amortisation to occur over the life of the car. And 10,000 electric miles a year implies some very very deep cycling with current charging rates (which are primarily limited by the domestic supplies available to cahrge them, and drastically improving them to handle the kind of loads neccesary to match liquid fuel "recharging" would be insanely expensive, even assuming the batteries could handle it). Red herring again. You said that electrolysis had gone out of style, more or less. Just admit you were wrong, it's easier. Not gone out of fashion? Really. I didn't realise electrolysis fed europe any more (as it did before the invention of practical steam reforming). It is less important to the global economy than it has been in the past, as alternative routes to the original primary products of it have been discovered or demand for them has been much reduced. Aluminium and the Chlor-Alkali industry are two of the few remaining bastions of it. (And aluminium may not last much longer as it appears a carbothermic route to aluminium appears to have been developed) Yet nobody's doing it. Even Sasol has dumped coal gasification for steam-reformed natural gas as a feedstock. Rentech's gears shifted similarly a few years ago. But if you're going to use NG as a feedstock, why not use it directly as LNG/CNG (or Hythane, with H2 to improve the flame speed)? Apart from the Chinese? They are going big into coal liquefaction to escape the problems they have been suffering with fuel price increases recently. Especially with the ongoing pirate problems in the Straits of Malacca and the failure of the project to build the pipeline across the "neck" of Thailand/Burma. Natural Gas as a feedstock has various advantages, and one would expect Sasol to abandon col for natural gas at the first opportunity since they use an indirect process (Fischer-Tropsch) which is easily adaptable to any carbon source. Natural gas happens to be available in huge quantities at low prices at the moment and doesn't have any of the regulatory hurdles associated with coal. Shenhua Group is pursuing direct coal liquefcation technologies and have atleast one operating plant right now (about 20,000bbl day from the first train that I know for a fact has been operating for quite a while). You can double your well-to-wheels efficiency and eliminate massive chemical plants with all their costs and emissions. The concentration on "everything must convert to gasoline" is some kind of mental disease. Because diesel and petrol are far superior motor fuels to compressed or liquid natural gas? Well to wheels efficiency is all well and good but you have to build an enormous new natural gas distribution infrastructure and then you have to accept reduced range and the like. People aren't going to go for it en masse. Then there are emissions from the sloppy handling of motor fuels to account for, natural gas is a rather higher power greenhouse gas than hexane. (if hexane is even a greenhouse gas) and diesel doesn't even evaporate very quickly. You mean, like converting NG that costs $3/mmBTU at the Henry hub to LNG that competes head-to-head with $30/mmBTU ULSD at truck stops? And yet almost all the vehicles using CNG/LNG in the US are busses and other such vehicles (taxis) that never get v ery far from the home depot. This cannot be said for personal vehicles and road hauliers. Okay, consider an alternative scenario: we wire our highways to eliminate 90% of motor fuel demand with electricity supplied directly to vehicles. Trucks use overhead wires, light-duty vehicles use capacitive coupling to their steel tire belts from plates in the roadway. I already modelled this in the context of the United Kingdom. Using the projected cost of the Siemens "eHighway" system, I generated an enormous cost to the taxpayer even if gilt issues were used to pay for the conversion of all motorways and other trunk roads (carrying over half of all Large Good Vehicle vehicle-miels). You end up having to charge so much for electricity that the LGV owners have no incentive to use the highway rather than liquid fuels. (This i s to avoid blowing a collosal hole in the British governments' finances by losing the revenue from fuel duty as well as to apy for the repayments on the infrastructure). You have to reduce the cost of the infrastructure by an order of magnitude before it becomes viable even only putting it on one lane in each direction of motorways/trunk roads. Supplying 360 GW continuous at $3000/kW is $1.08 trillion, a fifth of the synthetic gasoline scenario. It also eliminates the chemical plants and all the air emissions and most of the noise of combustion engines. Which would you rather have? The electricity cost is not the dominant factor. The dominant factor is the cost of the overhead wiring required to make all that viable. And capactive coupling from the roadway has its own set of issues, unlike with overhead wiring you can't easily see who is using the power at any one time. You could have problems with people using easily equipment by the roadside to "steal" electricity. It would be far easier to conceal than some suspicious cables that are hooked up to the high tension switchgear at the substation or to the overhead wiring for all to see. Wrap it in a torpedo-shaped polyethylene sheath with fins, and drop it in an oceanic subduction zone. Maybe ballast it with some iron to get a good descent speed, bury it nicely when it hits sediment. If that sort of disposal was considered politically acceptable it woudl be simply just to crush the graphite, bond it with epoxy and put that in the disposal "torpedoes". You have to dispose of far less volume. That's what I thought, a long time ago. I've learned that the rich are just playing the rest of the people off against each other. Nations rise as mercantilists and fall as free-traders. I don't think the rich playing people off against each other is sustainable, the earnings gap between the workers in China and those in the West is narrowing daily. Soon labour arbitage will not be a highly profitable practice. Yet the USA hasn't built a conventionally-powered aircraft carrier since when? It effectively has one fitting out right now. The America is effectively a carrier... part of the USMCs ongoing campaign to get itself its own flattop... its an amphib without a well deck. But anyway.... the carriers are still very expensive compared to conventional decks, hence why the CVF ended up as being gas turbine powered and it now appears the new French deck will also be gas turbine. The costs may amortise but remember the original USN decision to go nuclear was based upon a comparison with oil fired steam turbines. The calculation is rather different now, this is one of the reasons that the USN has not ordered a nuclear powered cruiser since the Arkansas in 1980 (CGN-41). They have a rolling programme for nuclear decks so there is little reason to change, but it has affected other navies that were looking at nuclear surface ship propulsion. (The French effectively did it just to prove that they could). Massive quantities of jet fuel aren't cheap either. A Dreamliner costs about $120 million. The single biggest line item in the operation of an airliner these days is fuel. If you can remove the factor of fuel, and also eliminate the reduction of cargo capacity with length of flight, there's potential for both saving huge amounts of money and adding revenue. Imagine the trans-oceanic airlines which bought fleets of nuclear towplanes and passenger/cargo "motorgliders". War in the Middle East? "Oh, great, we'll have business flocking to us while our competitors go out of business! Place some more orders, we'll have the new aircraft coming on-line about the time that demand rebounds." It would be a one-way ratchet, with the elimination of petroleum from the segment at the end. Even if we accept that Airliners will not be powered by synthetic kerosene in the future, there is always the Reaction Engines A2. With some very crude calculations I think the A2 could cover LAX-Brisbane with 300 passengers using approximatley fifty tonnes of hydrogen as fuel. (Range seems to scale by the square root of the fuel load) Journey time would be something on order of 1hr50 minutes including a slight dogleg to avoid overflying Vanuatu. If we use the crude estimation for low cost electrolysis cells of ~50kWh/kg Hydrogen and use our estimate of 5 cents/kWh, we get ~$2.50/kg hydrogen (other costs like compression and cooling the hydrogen have to be accounted for but are minor in comparison with the electricity price, this will give us a first order estimate). 50t of hydrogen is about $125,000 of fuel, which sets the fuel component of a one-way ticket from LAX to Brisbane at something like $416. Or about 3.8 cents/km travelled. That isn't awful. Also with a conservative 90 minute turnaround time (Southwest manage 30 minute at major hubs apparently, but handling cryogenic fuels is always fun) you might be ale to make 2 full return trips per day. (This leaves only 2hr30 for extra maintenance at night, but conventional airliners manage similar levels of readiness). 2 return trips per day, whereas at 400 knots you will not be able to manage one. I am not sure if the cost of the fuel eats up the cost of your reactor aircraft (which is certain to cost a comparable amount to an airliner), but I don't know. (Also with regards HSR at 320/360kph, if you are interested in speed Transrapid has been shown to do 505kph and the Chūō Shinkansen will achieve those speeds in regular service).
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Post by engineerpoet on Feb 12, 2013 21:29:18 GMT 9.5
You may not have noticed... but the United States Navy doesn't have access to billions of tonnes of limestone while its in the middle of the Pacific Ocean steaming at 30 knots. You might have noticed that I'm open to other possibilities, and even named one. However, mining and calcining a few billion tons of limestone per year is going to have some negatives. No. I propose to re-purpose the existing natural gas distribution network from the provision of space heat and DHW to motor fuel. One of the benefits is better year-round averaging of usage. Eaton is/was designing a home-scale CNG compressor in the $500 price range. Gas can also be used as a backup for electricity if the grid fails or is overloaded. It's only worthwhile as long as you have competitively-priced natural gas to use in it. I don't see gas remaining cheap for very long. It's strange that you should say this, because a network of LNG fueling stations started being built out at the nation's truck stops some time ago and is well on its way to completion. The net cost of LNG is a fraction of the price of ULSD. Entire fleets of CNG buses are being purchased in California. Cummins Westport has a line of natural-gas engines for heavy vehicles. If the stuff makes such bad motor fuel, why are they bothering? Hint: your premise is wrong. Because it's the only way oil companies can make money on it. Unfortunately for them, if they build plants based on today's feedstock price of $3/mmBTU they'll get burned badly when the shale-gas bubble collapses and prices head towards $10 or even higher. If you view CNG as the gas-fuel answer to the PHEV, you'll see that there's no such expense. If we take Eaton's $500 compressor as a given, and 3500 PSI 80 ft³ SCUBA tanks for under $200 retail also, you can use natural gas the way a PHEV uses electricity: as the energy supply of first choice until the tank is empty. Since the average daily commute is 22 miles, it doesn't take very much capacity to replace a large fraction of liquid motor fuel use. A $1000 system can pay for itself in about a year. What you need is something to perform the job that natural gas would have done at home. Heating water and air is easily done with electricity, and nukes are carbon-free. Depends on the chemistry; there are Li-ion electrodes with very long cycle lives coming down the pike. Several claim very low degradation despite 100% DoD per cycle. It is physically identical to SMR hydrogen. Its real biggest problem is cost. 33 miles a day, 300 days a year. At 250 Wh/mi at the terminals, 8.25 kWh out of the battery. A 12 kWh battery is sufficient for this, less than 90 kg at 140 Wh/kg. Braking performance: 6 C is 72 kW, which is a lot of braking power. The Fusion Hybrid Energi claims 70 kW power in EV mode. Charging a 12 kWh battery at C/10 can be done twice a day with an extension cord. They would have a better time dealing with both their fuel price problems and air-pollution problems if they just distributed syngas as town gas for heating and also compressed as motor fuel. It eliminates all the downstream chemical processing, its costs and its losses. The flame speed of CO mixtures improves with increasing H2 content. Because diesel and petrol are far more expensive than CNG and LNG, and do not burn nearly as cleanly. Let me remind you here that the only way to improve the environment and standard of living is to substitute cleaner energy for dirtier, and cheaper energy for costlier. Uranium is extremely cheap and clean, NG is intermediate in cleanliness, oil is costliest and a distant third to NG for pollution, and coal an even more distant fourth in cleanliness (though next-cheapest to uranium). That is changing very rapidly; many truck stops along major routes already have LNG dispensers. I'd hyperlink the announcements but that seems to guarantee that the comment disappears forever. What I have on electrification of railways is, IIRC, around $1 million a mile. There's only about 35,000 miles of Interstates in the USA, and $35 billion in capital cost would likely be repaid in fuel savings in the first year. Heavy trucks should probably be diverted from pavement anyway; dual-mode schemes like Bladerunner would put them on cheaper, more durable rails which can be maintained with hand tools. You need to review your EM field theory. You aren't going to get significant amounts of power except with a very tightly-coupled plate; anything on the roadside would be lucky to collect milliwatts. How to pay for it: road tolls. That wouldn't separate the transuranics and fission products from the graphite. The CaCO3 scheme is just to sequester C-14. The artists' concepts are very pretty, I admit. I'll wait for them to prove that the Skylon engine isn't another SSME before betting on it.
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Post by edireland on Feb 13, 2013 3:02:07 GMT 9.5
You may not have noticed... but the United States Navy doesn't have access to billions of tonnes of limestone while its in the middle of the Pacific Ocean steaming at 30 knots. You might have noticed that I'm open to other possibilities, and even named one. However, mining and calcining a few billion tons of limestone per year is going to have some negatives. Apart from having a series of giant holes in the ground where the limestone used to be, I can't really think of that many. The arguments against mining of limestone often revolve around things like the dust from thousands of mining lorries and the like. Since the calcining plant can be constructed on the site and supplied by the supergrid at ultra high voltage the only thing going out will be trainloads of cement to the coast or to construction sites. One train a day extra on the railway line (plus another of empties) is not going to cause many of the ecological nightmares associated with massive scale quarrying. No. I propose to re-purpose the existing natural gas distribution network from the provision of space heat and DHW to motor fuel. One of the benefits is better year-round averaging of usage. Eaton is/was designing a home-scale CNG compressor in the $500 price range. Gas can also be used as a backup for electricity if the grid fails or is overloaded. It's only worthwhile as long as you have competitively-priced natural gas to use in it. I don't see gas remaining cheap for very long. Problem with that is the existing domestic natural gas grid that is what currently goes near most fuel stations, certainly in the UK, is the low pressure "last mile" system. Trying to load huge demand spikes on the system (such as when lots of vehicles want fueling in rapid succesion - such as in rush hour) would lead to nasty pressure drops and all sorts of problems. Really you would either need a huge LNG staging tank where the existing petroleum tanks are, but that is likely to have planning and permitting problems since such a tank is likely far more unstable than a petrol tank in a case of a fire or whatnot or you would need to directly connect the fuel station to the high pressure grid which could require a few miles of extra pipework for each station. It's strange that you should say this, because a network of LNG fueling stations started being built out at the nation's truck stops some time ago and is well on its way to completion. The net cost of LNG is a fraction of the price of ULSD. Entire fleets of CNG buses are being purchased in California. Cummins Westport has a line of natural-gas engines for heavy vehicles. If the stuff makes such bad motor fuel, why are they bothering? Hint: your premise is wrong. And yet, despite the enormous subsidies thrown at compressed natural gas vehicles in the United States, and elsewhere, its use in long distance vehicles appears to remain a rounding error. (And note that the busses in California will tend to make runs that only ever take them a few miles from their home depot, making range concerns moot). Why is this? It is simply a political statement designed to claim that they are doing something to reduce oil dependency while not actually spending any money. LNG is apparently "taking off" as well, but trying to run a cryo plant in every single filling station is going to be far more troublesome than a simple compressor. That is definitely going to require some new infrastructure, or simply resort to LNG deliveries by truck/lorry.... but that is going to require an enormous fleet of cryogenic-rated trailers. Because it's the only way oil companies can make money on it. Unfortunately for them, if they build plants based on today's feedstock price of $3/mmBTU they'll get burned badly when the shale-gas bubble collapses and prices head towards $10 or even higher. You mean like it is in Europe right now? The import price for natural gas into the UK today is $11.87/mmBTU. The only place with such insanely depressed natural gas prices is the US, while most synthetic fuel production capacity is focussed on places like Qatar, where they are building synthetic fuel plants because they calculate it is better value to build those and make value added goods than it is to export liquid natural gas with all the infrastructure that has to bebuilt for that. The amount of energy in one US of natural gas in the UK is about 88MJ, compared to about 48MJ for one dollar of diesel or petrol. (These are the wholesale prices). Unfortunately distribution of natural gas is rather more expensive, especially when you have to deliver a compressed/liquefied product at the end. It tends to erode natural gas' price advantage. You might end up marginally cheaper but is hardly a game changer that is going to make everyone jump for it. (In europe almost all lorries are diesel which means they are not convertible). If you view CNG as the gas-fuel answer to the PHEV, you'll see that there's no such expense. If we take Eaton's $500 compressor as a given, and 3500 PSI 80 ft³ SCUBA tanks for under $200 retail also, you can use natural gas the way a PHEV uses electricity: as the energy supply of first choice until the tank is empty. Since the average daily commute is 22 miles, it doesn't take very much capacity to replace a large fraction of liquid motor fuel use. A $1000 system can pay for itself in about a year. If people just wanted to use cars for the average commute, they would already be using electrics since they could charge up at the destination and make the return journey with even something like a Leaf. People like the freedom a car gives them in that they can drive 30 miles to go for a day out or shopping and then drive back without worrying about locating a charging point or similar once they arrive. And it might pay for itself compared to a PHEV, but PHEVs are a looong way from being viable at the present time. A 3500psi Scuba tank... is about 240bar, which makes the density of the natural gas..... 0.160kg/L. This translates to an energy value of 7MJ/L compared to ~40MJ/L for petrol or diesel. You are looking at six times the fuel volume for CNG compared to diesel or petrol. And then since Natural Gas requires the use of a spark ignition type engine this means you are hamstrung by the Otto cycles inferior efficiency. Leaving you ~20% down compared to the diesel cycle. (this also erodes your fuel cost advantage compared to diesel) (As an example, a fifty cubic feet tank ends up having an energy capacity equivalent to roughly one litre of liquid fuel). Even LNG ends up with an energy density half that of diesel. What you need is something to perform the job that natural gas would have done at home. Heating water and air is easily done with electricity, and nukes are carbon-free. Indeed it is, air source heat pumps can do space heating more efficiently than anything I know of. (with air to air pumps we are looking at COPs of ~5). Although if you do use an air to air system this means that the cheapest solution for hot water is to use a simple immersion heater on "Economy 7" electricity, atleast in the UK, since the capital cost of air-to-water heat pumps is absolutely enormous (compared to £30 for the heater) and the COP isn't brilliant anyway. Depends on the chemistry; there are Li-ion electrodes with very long cycle lives coming down the pike. Several claim very low degradation despite 100% DoD per cycle. I've seen those, some of them appear to be yet more benefits from the discovery of things like Graphene (its more bragging rights for me snice that nobel prize went to people from my department ). Unfortunately many of them seem to be quite a long way away and I worry that they won't arrive in time. It is physically identical to SMR hydrogen. Its real biggest problem is cost. Hydrogen generally has some enormous problem as a motor fuel, its even more problematic than natural gas. (80kg/m 3 for a cryogenic fuel, even one with such a high heating value, is insane). 33 miles a day, 300 days a year. At 250 Wh/mi at the terminals, 8.25 kWh out of the battery. A 12 kWh battery is sufficient for this, less than 90 kg at 140 Wh/kg. Braking performance: 6 C is 72 kW, which is a lot of braking power. The Fusion Hybrid Energi claims 70 kW power in EV mode. Charging a 12 kWh battery at C/10 can be done twice a day with an extension cord. Those estimates of 250Wh/mi tend to assume rather tepid driving at low speeds with none of the auxiliaries turned on, a more accurate figure as far asi can tell is ~500Wh/mi. (once engine efficiency is accounted for that gives you similar energy consumption to a mid sized conventional vehicle). And another thing I didn't note earlier, you still hae to account for the absurd purchase price of most electric vehicles. You will end up with a Nissan Leaf in price terms once you add in a safety margin at the higher and more reasonable energy consumption. They would have a better time dealing with both their fuel price problems and air-pollution problems if they just distributed syngas as town gas for heating and also compressed as motor fuel. It eliminates all the downstream chemical processing, its costs and its losses. The flame speed of CO mixtures improves with increasing H2 content. Unfortunately the density of syngas in energy terms ends up even more dire than natural gas due to the oxygen atom that is hauled along with the carbon monoxide and the low molecular mass of the average mixture (which leads to low densities, even when compressed at very high pressures). Because diesel and petrol are far more expensive than CNG and LNG, and do not burn nearly as cleanly. They aren't really that much more expensive once you use European natural gas values which are likely to be the average once the shale gas shock works its way through the system in the US. The particulate and nitrogen oxide emissions from diesel engines have been improved to a very large degree by a combination of gas bag filters and selective catalytic reduction using products like "AdBlue". And before you ask how much extra AdBlue costs... almost nothing. If you buy in bulk it is ~45cents/L, and is used up at ~4% of diesel consumption which means it adds effectively 1.8 cents to the price of a L of diesel, which is rather small. Let me remind you here that the only way to improve the environment and standard of living is to substitute cleaner energy for dirtier, and cheaper energy for costlier. Uranium is extremely cheap and clean, NG is intermediate in cleanliness, oil is costliest and a distant third to NG for pollution, and coal an even more distant fourth in cleanliness (though next-cheapest to uranium). Coal elimination is the most important thing by miles in my opinion. I calculated that without synthetic fuel production ro anything like that nuclear could cut carbon dioxide emissions in the UK by ~65%. But you need something like synthetic fuel to do anything about the last 35% since it is basically motor fuels. That is changing very rapidly; many truck stops along major routes already have LNG dispensers. I'd hyperlink the announcements but that seems to guarantee that the comment disappears forever. According to the DoE's Alternative Fuel Data Centre , there are a total of 28 LNG capable fueling filling stations in the entire continental United States. What I have on electrification of railways is, IIRC, around $1 million a mile. Wow, I haven't seen costs like that proposed for projects beyond the end of the 90s, and that was cut price ~25kV Mark 3D overhead wiring for British Rail. If only it was still that cheap today. A more reasonable estimate for overhead wiring these days is about ~$2-2.5m per track mile using Network Rail 'Series 2' equipment that been optimised for minimum life cycle cost. You then have to account for the fact that truck overhead wiring by definition has twice as much suspended conductor and must then substitute far stronger cantilevers with far longer reach and taller supports (because lorries have a far larger "loading gauge" than British railways do). Even electrifying only one lane in each direction you will strugle to get short of $5m/ route mile considering that you must use rather lower voltages than on railways for safety reasons, and must thus provide a lot more substations. (eHighway appears to use a ~3kV potential between the two conductors, which implies 1500V between each conductor and the ground). There's only about 35,000 miles of Interstates in the USA, and $35 billion in capital cost would likely be repaid in fuel savings in the first year. You are more likely to have to spend $175bn and there are significant maintenance costs to consider. And then there is the greater capital cost of the vehicles which means that many hauliers will be slower to transfer across, especially those that don't spend a huge proportion of there time on interstates. Heavy trucks should probably be diverted from pavement anyway; dual-mode schemes like Bladerunner would put them on cheaper, more durable rails which can be maintained with hand tools. Bladerunner-esque roadrailers failed because of the increased capital cost of the equipment and its maintenance compared to things like swap bodies. I unfortunately get the feeling that this latest "Bladerunner" concept has been produced by people who have absolutely no idea how a railway functions and how it gains its energy use advantage. It also claims that there would be little wear on the road, which unfortunately has been proven to be rather incorrect due to experience with Bombardier's GLT, since while this system will only put weight on the road wheels when accelerating, braking or climbing steep gradients, this will happen with the road wheels in exactly the same place. On steep climbs you will get horrifically concentrated road wear which is very expensive to repair, just as GLT has lead to all sorts of problems. You need to review your EM field theory. You aren't going to get significant amounts of power except with a very tightly-coupled plate; anything on the roadside would be lucky to collect milliwatts. I had to re-read your earlier statement.... attempting capacitive coupling to the tyre reinforcing is insane. I found a paper on it that suggests only 70% efficiency. That is rather lower than overhead wiring, and also reduces the effectiveness of regenerative braking since you would have to return the power to the road through that efficiency loss. Also you could still steal power by running a single cable along the sides of a dual carriage such that they are on the edge of the coupled roadway, that would likely be inconspicious at the high speeds prevalent on major arterial roads, although that is a rather minor concern. Road haulage can switch to overhead wires in principle but I think motorail has a better chance of cutting fuel consumption overall than capacitative coupling, all the extra substations neccesary to support that equipment could probably buy you enormous operating subsidies for such services. How to pay for it: road tolls. That is a political impossibility unfortunately, it is th world we live in. That wouldn't separate the transuranics and fission products from the graphite. The CaCO3 scheme is just to sequester C-14. There are no measurable transuranics or fission products in the graphite, how could there be? They would have to escape a metallic uranium rod, penetrate the magnesium alloy fuel cladding and then penetrate the magnesium alloy channel cladding. Across a gap filled with high pressure carbon dioxide coolant. The artists' concepts are very pretty, I admit. I'll wait for them to prove that the Skylon engine isn't another SSME before betting on it. The hardest bit of the SABRE/Scimitar engine technological has now been demonstrated, they tested a mock up pre-cooler assembly this summer and apparently it works as designed. The rest is fairly simple, and the Scimitar proposed for use in the A2 doesn't have any of the extra rocket type stuff that makes the SABRE complicated. I think they can do it if someone gives them the money.
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Post by engineerpoet on Feb 13, 2013 7:25:13 GMT 9.5
Trying to load huge demand spikes on the system (such as when lots of vehicles want fueling in rapid succesion - such as in rush hour) would lead to nasty pressure drops and all sorts of problems. Apparently you're reading something other than what I'm writing. A PHEV-style CNG system wouldn't require fast filling, because liquid fuel is always there as a fallback. The Eaton compressor is sized for home use; users would fill vehicle tanks overnight. 20 scf/hr isn't a very fast pace, but it would bring a pair of 80 ft³ tanks from empty to full between evening and morning. You'd connect the compressors in garages and carports, with lines sized for gas grills. The EIA's latest figures are for 2011 and have not yet captured the LNG buildout hitting its stride in 2012, but even there the NG figures show growth while diesel consumption is sliding. The 2011 figures show NG within striking distance of biomass. A year-old GCC article shows Clean Energy expecting to have 150 LNG fueling stations operating by the end of this year. The map shows decent coverage of every Interstate south of I-70. Dresser-Rand has licensed (from Expansion Energy LLC) the technology for engine-driven LNG plants producing as little as 1500 gallons/day. This has uses both in truck fueling and in exploitation of stranded gas at e.g. oil wells. The price of Brent crude at 5.8 mmBTU/bbl and today's spot price of $117.03 is over $20/mmBTU, and that's before refining. Why is that do you think? Maybe it's because most countries are foolish enough to NOT convert to NG at around half the cost. They could gain a substantial advantage, and exploit their own reserves of things like landfill gas (small as it is, it's something). Whoa, STOP RIGHT THERE! I have explained that the CNG range is NOT a limit for the vehicle any more than the battery range is a limit for a PHEV, and you keep getting this wrong (and then going on at length based on the faulty concept). The CNG system would be a tank pack that might not even be permanently installed in the vehicle. It could be in the car's trunk with a disconnect for its plumbing and wiring. If you needed the room, you could unhook it and stow it. When the tank pack was empty or absent, the car would run on liquid fuel. Commuting is usually done with only one person in the vehicle and no cargo. For this use, taking up most of the trunk space with gas tankage would not be a problem so long as it was easily removed by the owner. I don't think people care about that. They care about $/year savings. An investment which pays off in a year is going to get lots of buyers. Something that brings their gasoline consumption down to a gallon a week will be popular for that alone. Closer to half a gallon, one SCF of NG is about 1034 BTU. A pair of 80's would hold about 1.5 gge. At 25 MPG, that's the daily commute and then some for most people. Most of the time they would never need to burn liquid fuel. Nuclear electric replaces NG, NG replaces liquid fuel. That's the game plan. It's roughly the same as hydrogen gas. It depends what you want to use it for; it'll burn just fine in an Otto engine, and would work as well as NG as a port-fumigated fuel. If it takes a 3-pack of 3500 psi tanks to run the daily commute, who cares as long as they fit in the trunk? What you want is something that's both cheaper and cleaner than petroleum; if it makes the grade, good. If not, trash it. In the short term I'd aim at eliminating coal combustion. It may be too valuable as a source of the remaining carbon requirements to get rid of in the short term, though gasifying garbage might be able to do that instead. That's where a good hydrogen-rich town gas (syngas) would work nicely if batteries were still expensive. The syngas can be scrubbed of CO2 and has more energy per mole of carbon than any liquid. If you can make the syngas from garbage or biomass and nuclear electricity, the CO2 scrubbing can even make it carbon negative. This is one more technological route to the necessary end. 66 if you include the private ones, and the list could easily be out of date. A number of those on the list show just how easy it is to put LNG someplace; there's an LNG dispenser at an HEB (grocery store chain) site in Texas! Clean Energy LLC estimated 70 stations by the end of 2012, and they may have met that goal. Remember, you're talking about rubber-on-steel here. Wear is going to occur mostly on the rubber side. Besides, replacing a few segments of steel rail every few years is a heck of a lot faster and cheaper than replacing entire road surfaces. Why, so long as it works? Hanazawa measured 80% at 1 MHz, 55% at 13.5 MHz (year-old DOCX file containing an un-dated abstract from a paper). Note that this is without any attempt to optimize tire or pavement composition. Later efforts appear to have found efficiencies as high as 90%. Suppose for a minute that a system with practical power density can't do any better than 55%. Is that a killer? Hardly. If your delivered cost of power goes from 10¢/kWh to 18¢, it's still a long ways below the 30-40¢ that gasoline costs at the crankshaft. You don't feed braking power back to the road, it goes into the battery. You need a battery anyway, because power delivery is going to be in the region of 10-30 kW which is insufficient for acceleration. It may not even be adequate for continuous cruising, but that doesn't necessarily matter. What matters is being able to get to more or most destinations without having to stop to recharge en route. If you can deliver just 2/3 of cruise power via the road, a Leaf with a 90-mile unassisted range can make 200 mile legs with some range in reserve. Lighter vehicles with smaller batteries (say, 2-5 kWh) could be quite adequate commuter cars. If the pack costs $400/kWh, the $800 for a 2 kWh battery is quite a bit cheaper than an ICE powertrain. It may only be able to go 10 miles off the network, but if you charge at home, charge at work and have power delivered on the road, when would that be a problem? There's your $10,000 clean-air commuter car. There are tollways around many major US cities, Interstate 80 is a tollway from Indiana eastward, and there are new private tollways in states like Texas. People will pay tolls if they feel they're getting something for their money. You wrote, and I quote, "This is a known problem that has come up in the context of Magnox and AGR decommisioning since they can't just burn off the graphite moderator and trap the nonvolatiles." If the concern is trapping something other than C-14, what is it? You explain what you meant.
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Post by engineerpoet on Feb 13, 2013 9:06:14 GMT 9.5
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Post by David B. Benson on Feb 13, 2013 11:52:25 GMT 9.5
engineerpoet --- Don't hold your breath waiting for rf powered electric vehicles.
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Post by engineerpoet on Feb 14, 2013 3:43:30 GMT 9.5
engineerpoet --- Don't hold your breath waiting for rf powered electric vehicles. It's conceivable that something like this could be rolled out very quickly once the decision is made. Extruding asphalt with some heavy mesh conductors in it and rolling it onto an existing roadbed (perhaps scraping up and recycling the existing asphalt) is something that can be done at a rate of a mile or so per day. Power needn't be an issue either. If each vehicle can consume up to 20 kW, a single GE LMS100 gas turbine could power at least 5000 of them at once. That would serve demand until you got the nuclear capacity on-line to replace the NG. The main issue would be the storage or DSM required to handle the rush-hour demand spikes, not the RF gear. Stuff built for the HF ISM bands is going to be pretty cheap, though you probably want to work with the semiconductor suppliers to make sure they have enough capacity to build it at the rate you want it installed.
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Post by anonposter on Feb 14, 2013 4:36:06 GMT 9.5
More than a kilowatt per square metre of radiowaves is not something any sensible regulator would allow you to do in the middle of a road.
Just too much chance of cooking pedestrians.
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Post by engineerpoet on Feb 14, 2013 5:11:06 GMT 9.5
More than a kilowatt per square metre of radiowaves is not something any sensible regulator would allow you to do in the middle of a road. It's not "radio waves". It's a near-field capacitive effect and requires resonant coupling to be very effective. Someone walking across the road wouldn't be resonant and wouldn't pick up the energy. There's also the little detail that the presence of a vehicle can be sensed by the power drain, or even a coded signal (in a sane world, that signal would carry "digital cash" to pay the power bill). The RF amplifiers could and should be shut off when no vehicle was on the strip. Incidentally, the power flux wouldn't be ~1 kW/m², it would be many times that. The effective area is roughly equal to the tire contact patches, perhaps 100 in² for a passenger car. Pushing even 10 kW through that is about 160 kW/m².
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Post by engineerpoet on Feb 14, 2013 21:25:41 GMT 9.5
One thing I missed: Those estimates of 250Wh/mi tend to assume rather tepid driving at low speeds with none of the auxiliaries turned on, a more accurate figure as far asi can tell is ~500Wh/mi. Real-life range in the Leaf is ~90 miles, or 275 Wh/mi. The much larger Tesla Model S is rated at 265 miles on 85 kWh (330 Wh/mi) and in real-world driving was tested to go some 200 miles after some test driving before the start of the road trip (at most, 425 Wh/mi). 275 Wh/mi at 60 MPH is 16.5 kW. If something can deliver 20 kW to the vehicle, it can charge in motion; even if only 10 kW can be delivered, the remaining 6.5 kW allows a run time of roughly 4 hours and a range of over 200 miles. A vehicle lighter than the Leaf would have lower power requirements and could probably cruise on 10 kW or less. Power-from-the-road changes the game completely
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Post by Roger Clifton on Feb 17, 2013 18:29:38 GMT 9.5
There are some attractive aspects to extracting CO2 from a desalination process, whether seawater, groundwater or aerated grey water. For one thing, the process does not have to move vast volumes of air around to extract a few parts per million of CO2, because the CO2 has already preferentially dissolved out of the atmosphere to concentrate in the water surface. For another, it is low technology and might be placed anywhere accessible to a CO2-to-hydrocarbon plant. Another is that the energy used to separate the CO2 from the incoming water stream has already been committed by heating in the desalination process.
The CO2 must still be pumped out and presumably compressed to get it to whatever or whoever is going to convert it back into hydrocarbons, however I suspect there no more energy-efficient process for recycling CO2 from the greenhouse. The reasoning fails if the extra energy over desalination releases more CO2 than it collects.
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Post by trag on Feb 21, 2013 7:20:41 GMT 9.5
In case anyone missed the link to a new paper on why bio-fuels are a bad idea. Atomic Insights posted the link today. The paper is very thorough, or seems so to me. Of course, I haven't followed backwards and examined all the citations. phe.rockefeller.edu/docs/Kiefer%20-%20Snake%20Oil.pdfAnd no, I'm not saying that synthetic fuels using nuclear energy for energy input are a bad idea. It's relevant because there may still be those who think we won't need synthetic fuels because they think bio fuels are workable.
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Post by David B. Benson on Feb 21, 2013 9:57:58 GMT 9.5
I know of three successful Jatropha projects. The first two are plantings around fields tended by two groups of small villages in India, both off grid. In the first the stationary diesel electric generator was slightly modified to run on Jatropha oil. In the second a small refinery turns the vegetable oil into diesel grade fuel. In both cases there is enough fuel for one incandescent electric light per participating household during the evening and early night hours. One of the projects has enough power to also run streetlights at the same time.
The third is an actual plantation in Myanmar (Burma). The workers are paid a magnificent US$3 per day (6 days per week) [about three times the national average]. There is a rather substantial refinery as farmers from much of Myanmar bring their Jatropha oil to supplement the plantation's own oil. The resulting product can be mixed, in any ration, with petroleum based diesel. It is sold in Myanmar and also in Singapore.
I conclude Japtropha has a useful niche.
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Post by David B. Benson on Feb 21, 2013 10:00:31 GMT 9.5
I have read claims that pyrolysis liquids are suitable, as is, for stationary heating oils. Perhaps there will be a suitable niche market for biofuels via pyrolysis.
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Post by Roger Clifton on Feb 21, 2013 11:48:20 GMT 9.5
A desirable feature of starting nuke-to-avgas with CO2 rather than wood or hydrocarbon is that the operator cannot cheat by using the carbon resource as their energy supply. A process touted as "extraction of pyrolysis liquids for fuel" is likely to end up as an excuse to burn coal or wood.
Pyrolysis liquids have a long history as industrial fuel in the form of "hot wet gas", a short-lived intermediary between coal gasifier and furnace. Fresh from thermal cracking, the species in the liquids are too unstable/corrosive/toxic for further distribution without further refinement.
In 1950s, the Wundowie Charcoal Iron industry in the WAust. wandoo forest extracted methanol, acetic acid and acetone from their "pyroligneous acids". The main product was charcoal, in the 1940s for charcoal-driven cars, and in the 1950s for high-purity carbon steel.
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Post by engineerpoet on Feb 21, 2013 22:53:14 GMT 9.5
I have read claims that pyrolysis liquids are suitable, as is, for stationary heating oils. The problem is that there just isn't enough supply to get very far. IIRC, pyrolysis oil made from dry biomass has about half the heating value of petroleum. It contains a substantial fraction of water, is immiscible with petroleum, and is chemically unstable. Recently, GCC ran a piece claiming that bio-oil made from torrefied biomass had a much lower oxygen (acids/aldehydes/water) content.
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Post by edireland on Feb 21, 2013 23:02:32 GMT 9.5
I remember somewhere reading that even if half the entire landmass of the United Kingdom was devoted to growing biomass, it could produce sufficient material to allow roughly half our current domestic steel production, and nothing else.
We would need an order of magnitude more mass to do anything.
(Oh and there is interesting work on using hydrogen to reduce iron oxide directly which will leave the aforementioned motor fuels as the only major holdouts really).
There is a need for carbon anodes for aluminium manufacture that will have to be met though.
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Post by Roger Clifton on Feb 22, 2013 8:48:43 GMT 9.5
When smelting alumina, the carbon in the anodes comes off as concentrated CO2, which presumably could be recycled in processes similar to those already discussed. One shortcut that may be handy is the fact that CO deposits elemental carbon at middle temperatures.
Considering that the carbon is probably there to save on electricity, the presence of copious electricity may make it unnecessary anyway.
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Post by engineerpoet on Feb 22, 2013 12:28:08 GMT 9.5
When smelting alumina, the carbon in the anodes comes off as concentrated CO2 I believe it also produces some perfluoromethane, a very potent GHG. If that could be captured and e.g. reacted with metallic sodium, it would be a Very Good Thing. Or possibly the alternatives don't work very well, such as precious metals which still erode under electrolysis. Carbon has the virtue of being cheap. If you have enough energy you can react CO2 back to CH4, then use it to make pyrolytic carbon. Or maybe you can just take some charcoal, de-ash it in an acid bath, and consolidate it under heat and pressure to make carbon of the required consistency. The amount of aluminum used worldwide is much smaller than the available bio-carbon, so even at a 1:1 ratio it would not be a show-stopper.
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