h a l f b a k e r yA riddle wrapped in a mystery inside a rich, flaky crust
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Refined aluminum has got a lot of power in it. You can let that out with a thermite reaction. It is amazing they let the general populace walk around with that kind of potential energy in their hands, full of beer.
Here at BUNGCO we got tired of seeing that energy hauled away by the recycling
folks, sniggering all the way. So after the big fundraiser party we collected all the cans (mostly Strohs) and loaded them into the ceramic hopper of the TPSC. A turn of the key triggered the magnesium ignition and away we went!
It turns out that while iron oxide is a handy O source, it is hard to turn this reaction off or cool it down. Cooling with water diverted from the reservoir was a one time experiment. But it turns out that once up to heat, you can use atmospheric oxygen if you provide large amounts, then control the aluminum oxidation reaction based on the amount of oxygen allowed ingress.
The TPSC is painted green with little flowers, because this alternative fuel car emits no CO2 or other emissions except puffy white clouds of mother steam. And no nukes! And no hawks flying into windmills, yet.
Cars could run on aluminium, say US boffins
http://www.theregis..._fruitful_research/
Gallium catalysed aluminium rusting by water with production of hydrogen. [Loris, Sep 24 2013]
Steam Turbine Locomotives
http://www.douglas-...yturbn/whyturbn.htm
From The Museum Of Retro Technology [8th of 7, Sep 24 2013]
Enthalpy of formation for iron oxide.
http://www.youtube....watch?v=20Dh5IBnkX8
[bungston, Sep 30 2013]
Aluminum engine
Aluminum_20Combustion_20Engine
acurafan was there before me [bungston, Apr 19 2015]
[link]
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You had us at Thermite ... [+] |
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The efficiency of this overall energy cycle is
horrible. Lots of electricity is needed to separate
the aluminum from the oxygen. They mostly do
that using hydropower as the source of electricity
(90%+ efficient), but the actual electrolysis process
is perhaps only 66% efficient. When oxidized to
generate heat, the efficiency at which the heat is
used, such as in a steam car, is at most 40-45%.
So, from the original potential energy of falling
water, only .9x.66x.43 or 25.5% gets used to move
the steam car. |
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Now consider an ordinary electric car using
batteries or fuel cells. Efficiencies of charging and
discharging batteries have improved in recent
years, to perhaps 75%. If the electricity originally
comes from an ordinary large fuel-burning power
plant, the generation efficiency is 50% or so. So,
.5x.75x.75 or 28.1% of that energy gets used to
move the car. |
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Now consider a flywheel-powered car. The
conversion efficiency is 90%+ between electrical
and mechanical energy. Given the same ordinary
power plant, the numbers are .5x.92x.92 or 42.3%
of the original energy goes to move the car.... |
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What you say is incontrovertible, [Vernon]. |
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However, the fundamental problem with both
electric cars and those driven by flywheels is that
they don't use thermite. |
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Magnesium is normally used as an igniter for
thermite - the magnesium can be ignited fairly
easily, and produces enough heat to trigger the
thermite reaction. |
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Metallic potassium is much better as an
igniter, MUHWHAHAHAH ! |
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// the fundamental problem with both
electric cars and those driven by flywheels is
that they don't use thermite // |
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Neither do they use extruded double-base
propellants, fuel-air explosives, pyrophoric
powdered metals or chlorine trifluoride. |
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Which we see as a shortcoming in oh so
many ways ... |
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This reminded me of the linked article. |
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It's not quite the same; that version is likely more efficient and workable. |
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//this alternative fuel car emits no CO2 or other emissions except puffy white clouds of mother steam.// |
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You mean it doesn't grit the road with alumina as it goes along?
The other product is of course molten iron. You could cast things on the way. |
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Oh, and what is the TPSC? |
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//The other product is of course molten iron.// I
think the post describes reacting aluminium powder
with air, rather than with iron oxide, so there'd only
be alumina produced. |
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And at a guess, I'd say "TPSC" was "thermite powered
steam car". |
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//So, from the original potential energy of falling water,
only .9x.66x.43 or 25.5% gets used to move the steam
car.//. |
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True, but the first two stages are being done regardless to
produce the beer cans, so it isn't fair to attribute all the
inefficiencies and energy bill to the TPSC. |
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A more apt comparison would be the relative gains or
losses between using the recycled aluminum/aluminium to
power to TPSC or just melting it down to make more Strohs
cans and minimizing the need for virgin
aluminum/aluminium. |
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I'd just like to point out that nuclear detonations
were left off of [8th]'s list of possible fuels. There's
no reason you couldn't make an Orion car. |
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Not really recommended for short trips. |
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Short in distance or short in duration? |
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//"thermite powered steam car"// |
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For some reason I was imagining some stationary general-purpose steam-engine acting as a prototype. (On re-reading, the reason looks like stupidity.) |
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Interesting link about using Al to produce H2 from H2O. This thermite idea is much more direct: burning the Al with air rather than oxidizing with water to produce H2 then buring that. But interestingly you are still using water for the steam engine... |
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Now it occurs to me that heat engines are more efficient at higher temperature, and Al burns very hot. I'm no expert on steam engines, but The Wiki says that the Rankin cycle (typical steam turbine) operates over a fairly small temperature range, so perhaps some hot air engine would take better advanatage of this. |
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The thing to keep in mind about steam turbines is they work best when exhausting to a much lower pressure and temperature than the working fluid input, which ideally is superheated dry steam. |
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Power generation stations, and ships, achieve high efficiency because they can run a closed system using ultrapure water, and can stand the weight penalty of condensers, secondary cooling circuits, condensate recovery and feedwater pumps. |
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If the working fluid is free-vented to atmosphere, even through a multistage turbine, it's still going to be very wasteful. Steam turbines have been tried on locomotives <link> but never proved a success. |
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/some hot air engine/
I wonder if you could do this with the hot nitrogen left over after O2 is used for combustion? Unlike an internal combustion engine burning carbons where hot gases are produced from combustion (and used to do work), Al+O makes no gas. But any gas around is going to be very hot, and maybe that would suffice to turn the piston. |
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The alumina will indeed be deposited on the road, where it will serve to improve traction as it will be hot enough to melt into the asphalt. |
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If you're going to insist on running it mainly as aluminium with air then it's not really a thermite engine. Thermite is metal powder mixed with metal oxide. |
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From an environmental viewpoint the aluminium you put through your engine isn't being recycled and requires further alumina to be mined and turned into aluminium. Unless you can sell the byproduct (which sounds doable: there has to be quite a bit of mining and purification effort saved by that route). So, is the price of aluminium minus the rebate of alumina greater than an equivalent amount of gasoline/diesel ? |
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What's the enthalpy of combustion of aluminium ? |
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Aluminium is actually very common in your planet's crust. |
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Your current transport fuel systems rely on volatile hydrocarbons, and release CO2. |
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Liquid fuels can be produced from biological sources such as corn and rape seed oil. But they too release CO2 back into the biosphere. |
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Aluminium, now ... burns hot, no gaseous by-products. Produced by electrolytic refination - fine, that can come from solar or fission power. Effectively, it's converting electrical energy into a safe, stable solid fuel that can be burn in powder form. |
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Compared to electrolytic hydrogen, or batteries, this is starting to sound dangerously sensible. |
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I was expecting tethered termites on a treadmill,
feverishly trying to reach a forever receding queen. |
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// a forever receding queen // |
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A sort of red queen's race, then ? Cherchez la femme, as they say in detective novels. |
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What's the energy density of aluminum vs. zinc? It looks like the price per pound is pretty close. Zinc-air batteries are a fairly active area of research. Any idea whether the zinc or the aluminum market would better handle a huge jump in volume for energy storage purposes? |
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Though again zinc-air also suffers from a lack of thermite. |
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/dangerously sensible/
I was actually thinking that same thing. Thermite powered care sort of sounds like dynamite powered pogo stick. But aluminum really would be a safe solid fuel for reasons 8ths lists. The alumina could actually be returned and reduced as Flyingtoaster notes. |
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So what is the problem with using aluminum as a fuel? Is it that it is too hot? |
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It would lead to front mounted hoppers on cars and trucks
that seek out aluminum bicycles for fuel. Really it's an
irresponible idea for the danger it poses to cyclists, whose
body parts would have to be sifted from the aluminum
after passing through the shredder. You really should be
very ashamed. |
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I don't think anything's particularly wrong with it,
except that it only works with an external
combustion engine (steam), and we don't really
have the infrastructure or mature technology for
personal vehicle scale steam engines. |
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It won't work for IC engines because the
combustion products are lower volume than the
raw components unless I am mistaken. |
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There's also the question of whether it would
actually be more efficient than a pure electric
vehicle, because, like H2 or batteries, it's a
storage medium rather than a fuel source. |
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What [rcarty] said except for the "ashamed" bit. |
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'Round here, even without trying, I could pick up a couple bicycles a day on-the-fly by simply not bothering to jam the brakes on when one of those idiots, illegally riding on the sidewalk, goes barrelling through a sidestreet intersection, also illegally, without stopping to dismount. |
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The organic component (the stupid part) would have to be disposed of though. |
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//It won't work for IC engines because the
combustion products are lower volume than the raw
components// |
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You could always add water to the aluminium
powder, thereby using the expansion of superheated
steam. |
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Fuel injection would be tricky, though. |
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/the combustion products are lower volume/
What about expansion of heated air? Could one turn a piston with that? |
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A stirling idea. But seriously, burning metal powders in air does cause an initial expansion, as the heat outweighs the consumption of oxygen. I remember finding this out by blowing a garbage can lid a surprising* distance into the air with a small canister of magnesium powder and (below stoichiometric) oxidiser. |
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* OK, about 1 foot into the air. But it surprised me, since I expected a flash but little or no explosion. |
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burning gasoline you only end up with 7% more gaseous molecules than what you started with, then 7% less when the steam condenses. |
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But aluminium oxidises rapidly in air so you'd want the dust to be pretty freshly made before you tossed it into the cylinder. |
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//What about expansion of heated air? Could one
turn a piston with that?// |
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Yes. but horribly inefficiently. Expanding hot air
doesn't develop that much force per unit of
energy used. You really want a phase change in
order to get a decent amount of expansion. You
have one in an ECE, and in an ICE you effectively
have one even though combustion isn't usually
described that way. |
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[MB]'s idea of water injection might work. |
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Which makes me wonder, has anyone developed
an "in piston boiler" external combustion engine,
where water is injected into a super hot cylinder
and flash boiled to produce the expansion? |
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// burning gasoline you only end up with 7%
more
gaseous molecules than what you started with// |
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Where do you get that number? I make it 26% for
octane, and 25% for heptane. (Assuming the fuel
is
fully evaporated before expansion starts, which I'm
not sure is true). |
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2C8H18+2502->16C02+18H20 (Octane)
(16+18)/(25+2)=25.9% |
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C7H16+1102->7C02+8H20 (Heptane)
(7+8)/(11+1)=25% |
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And the water won't condense inside the piston,
so
it's a non-issue. |
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I'm assuming the fuel isn't evaporated before it's injected. |
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// "in piston boiler" external combustion engine, // |
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// water is injected into a super hot cylinder and flash boiled to produce the expansion // |
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A reverse Newcomen engine ? |
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The thermal shock on the piston and cylinder is going to be severe. |
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Better going for a Sterling cycle, maybe using hydrogen as the working fluid. |
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Ah, well, if you're actually going to look at the real
world. |
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// painted green with little flowers, // |
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Can it come in NATO olive drab with little flecks of brown, khaki and black ? |
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How is "in piston boiler" a tautology? |
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Most ECE build up pressure in an external boiler. |
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And I think with care in the injector design, and
proper selection of the wall material and mass, I think
it would be possible to build this without the thermal
shock being a problem. After all, modern small scale
steam engines already use a flash boiler system, so
the design is solved to that extent. |
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Sorry, the "real world" comment was directed at [FT],
you got in between us. |
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de nada, I had to resort to counting on my fingers to figure out the ratio of CH2 to O2. |
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The fuel might be evaporated before the ignition starts but it's injected close enough to TDC as not to add much to backpressure on the piston afaik. |
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Even so, a 7% gain (for gasoline) versus a 20%
reduction (for aluminum) (assuming
near 100% oxygen use) is going to be a prety big
efficiency hit. |
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Pondering the use of oxidizable metals as fuel, I wonder if this could be done more cheaply with iron. There is lots of metallic iron around. There is plenty more in the crust. |
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I think 8th said something about Enthalpy up there. I remembered Enthalpy as Entropy's gainfully employed little brother. I am looking up specifics of how to use that to determine energy by weight of various fuels. |
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// How is "in piston boiler" a tautology? // |
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Referring to "in piston boiler" external combustion engine - it's either a boiler (where a working fluid is vaporised and then piped away for use) or a piston, where a fluid expands and in the process does work. |
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A boiler is a continuous-process device, normally connected to the "motor" by a valve or valves. |
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A piston is a cyclic (reciprocating) device. In an internal combustion engine, the pressure (in a simple engine) varies from below atmospheric (induction) to above atmospheric (power). |
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An "in-piston boiler" therefore implies continuous expansion, which further implies an infinitely long cylinder. |
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Hence the accusation of tautology. |
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The word you are looking for is oxymoron, and I
disagree. |
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1) a closed vessel or arrangement of vessels and
tubes, together with a furnace or other heat
source, in which steam or other vapor is
generated from water to drive turbines or
engines, supply heat, process certain materials,
etc.// |
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"Continuous" is not part of the definition. And
since the specific idea I was suggesting was using
it in an atypical way, it's hardly surprising that it
doesn't quite match the standard usage. |
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What about the power-to-weight ratio? Hauling around a hopper of Al powder, as well as the thermal insulation (ceramics are light, but...) could be an issue.
Also, could the hot, flowing Al2O3 be used magnetohydrodynamically to generate electricity? I can't find much on the electromagnetic properties of Al2O3, but a parallel of the geodynamo effect could come in to play too (hot, moving, metal). |
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