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Capturing Waste Heat with Quantum Mechanics
TheMatt writes: "There is a summary of a Phys.Rev.Lett. article up at Nature Science Update that describes a design for a 'quantum afterburner' that would improve the efficiency of an Otto engine. It improves the efficiency by using a laser and maser to extract energy from the hot exhaust of the engine. In fact, the process could enhance performance beyond that of the "ideal" Otto engine."
I used a laser and a maser to extract energy from the waste heat generated by my Athlon. I've been running everything in my house but my computer off that exhaust tap!
They that would sacrifice their
So I get that you convert waste heat into light, first with the maser to get microwaves, and then with the laser to get some other wavelength. What then?
Why not simply use an adsorption type "refrigeration" (ammonium hydroxide & water) system to cool the air/fuel intake charge to make it more dense and get some more efficiency out of the internal combustion engine? The waste heat going out the exhaust and radiator could run the adsorption-cycle cooling system.
The hot gases belching out of your car's exhaust are not just useless waste. They are a laser waiting to happen, says physicist Marlan Scully
I sure hope this doesn't change the global warming going on or all that beachfront-after-the polar-icecaps-melt property I bought will remain high and dry (scuba diving in downtown LA whoohooooo)
I Am My Own Worst Enemy
First off, so-called gas-dynamic lasers have been known for years if not decades, so this is old news. Secondly, the energy efficiency is not increased beyond the theoretical limit of an Otto engine.
I think this idea is genial, but the cost/effeciency on a car would be "hard" to achieve. What I find interesting, is that this duo laser/maser only require heat from an exaust : nearly the same thing as evaporated water from nuclear reactor. This could lead to a better efficiency of nuclear reactor, and the cost of such laser/maser would be minimal compared to electricity generated by that system.
Ideally, if the excess heat was converted back into electricity, I wouldn't need to waste electricity on the fan, and I could substantially extend my battery life. Oh well, I can still dream.
In this house you will obey the laws of thermodynamics! -Homer
But really are they saying they can improve the efficiency of a Carnot engine, or just the Otto cycle?
Veramocor
My first thought when reading this title (nothing to do with the article:
"Producing Hot Air with Quantum Mechanics."
-Paul Komarek
Cars with frickin' laser beams on their heads .. And for once I might actually get them :-)
I am Slashdot. Are you Slashdot as well?
Can be found here (in PDF form), for all those who like reading physicists physics.
There's no reason for a sig here.
Hmmm... could be modified to improve my car's performance...?
--Metrollica
After reading the article, its not as far fetched as it sounds, atleast at a low efficiency.
The problem as I see it though is this, what is the engine going to do with the laser light anyway? Laser light isnt that usefull in a car as an energy source. And I cant see the intensity of light being enough to do something cool, like dissasociate water to H2 and O. This is probably in the "neat-things" file for quite some time. Though maybe they can use this technology for fixed poer generation (coal, nuclear) where the gasses temperatures are higher and there is more volume.
Anyone who considers arithmetical methods of producing random numbers is, of course, in a state of sin.-John von Neumann
If you check the front page, the LinuxWorld story was already posted earlier today. Tim or whoever posted it must have relized it was a duplicate and pulled it down instead of having people post comments on it.
Maybe we can say the editors have improved.
Do Quantum Mechanics work for Maxtor now?
General Relativity: Space-time tells matter where to go; Matter tells space-time what shape to be.
Wow. This is a neat idea. But not really a new one. Not new that is in terms of trying to find some way to use all the wasted energy. Right now we are still using technologies that are terribly inefficient. All this heat going out the exhaust pipe of our vehicles. What about the heat exhaust from your furnace? Your gas water heater? It seems that if we can generate X amount of energy, we should be able to use every last scrap of it in some way, rather than just simply releasing it into the environment. Does anyone know of any other projects out there to reclaim and use some of this lost energy?
I wonder if I could then direct that laser at the moron who's tailgating me while yacking on his cell phone. b-)
:::Horrendous Experiences Make Amusing Anecdotes:::
...The Fast and the Furious? I mean they had everything else: NOS stickers, neon lights on the undercarriage, ad naseum. Why not a laser in the engine?
-- ;-)
Kuro5hin.org: where the good times never end.
It'll make me feel like James Bond, without being British, or having so many STD's...
Could the exhaust gas heat be used to make a car heater that doesn't take so long to fire up?
But MIRACL is using a far more reactive fuel at far higher temperatures than anything you find in auto exhaust.
If you can get enough energy out of the exhaust laser, you can use the radiation pressure of the light to get the car to go faster!
(I know the pressure produced would be minimal - the sun's light generates a force of what? 80 tonnes?)
This would sure give a new meaning to 'back-firing'.
Er, I otto nae break them, anyway.
You see? You see? Your stupid minds! Stupid! Stupid!
Are _ external _ combustion engines that can be run (with appropriate mods) from ANY heat difference.
Although displaced by the internal combustion engine, the stirling engine has still continued to advance. Modern Stirling engines can be smaller than a coin & used in satellites, or larger than a house.
They are ideal for the recovery of energy from waste heat, exhaust's, furnace flues, domestic heat, etc.
Just think, no more tailgaters once they get these lasers mounted!
Thinking of jacking my car? Think again! I'll shoot you with my..uh...mini me...stop humping the...
If this makes it into your average car, would you have to take it to a normal mechanic AND a quantum mechanic? The price of the devices used in research had better come down before it happens.
I can see it now...
QM: (Wipes hands on oily rag) Well, if you lookee here, yer muffler wall is causing the maser beam to create destructive interference.
Car owner: uhuh.
QM: That, combined with the alignment of the quantum magnetic dipole is causing yer car to stall.
Car owner: But how much will it cost?
QM: Yer salary fer the next two years.
I can see a possible application for this: speed detector jamming. Lots of people buy radar/laser/microwave detectors for their cars to try to beat the cops. There are even some on the market which claim to scramble the speed detector in such a way to disable the readout. With the quantum laser/maser setup, the faster you drive, the hotter your exhaust, and the hotter your exhaust, the more ferociously you jam anyone attempting to gauge your speed. Great!
Quantum Mechanics has been known to be a time-trasnlation invariant theory. In layman's term, it means that you can run the clock backwards and everything is fine. There is no "irreversible" process. (For the jargon-empowered, QM does not have a natural "arrow of time").
However, we know the Thermodynamics 2nd law tells us that even *ideal* processes are essentially irreversible if we do work, i.e. waste heat is inevitable.
So the idea to use QM to improve this "ideal"-ness (classically speaking) is an intersting step towards understanding the *other* big issue in science : which is how the 2nd Law fits into the grand scheme of things. (Grand Unified Theories do not incorporate 2nd law since microscopically are processes are essentially reversible. The 2nd law drove many people nuts, including Roger Penrose.)
So the point of the paper is not "get more $$$" for you engine. It's an interesting gedenken-experiment (sp?) that proves a point.
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Joshu answered, "Mu!" (No)
I think you mistranslated 'Woof' ;)
Reboot macht Frei.
It actually has a big point.
:).
Although what you say may be correct, you have to remember that either using this to cool the intake or even better using it as a below-ambient intercooler on turbos increases the power-to-weight ratio of the engine because you can obviosly get more charge in a cylinder.
Thus you can create a lighter car with the same power and overall the efficiency increases because you have that much less mass to accelerate and that much less rolling resistance on the tires. Granted the efficiciency of the *engine* does not increase, but the efficiency of the entire system [car] does -- and that's the thing in the end that truly matters.
What I'm waiting for is efficient low-temperature thermo-couples to become cheap. That way electricity can be generated from the wasted exhaust heat getting rid of the need for an alternator.
Combine that with regenerative breaking and a few bucks on gas can definately be saved
So, um, how do you use this combo maser/laser beam to do soemthing usefull?
If Mr. Edison had thought smarter he wouldn't sweat as much. --Nikola Tesla
if you could route the laser back to the combustion chamber, you could use it in turn to burn extra fuel (similar to the way nos affects combustion). the increased fuel being burned would create more exhaust. wash, rinse, repeat until nearly 100% of the fuel in the chamber is being burned and the car reaches maximum feasible efficiency. probably not all that feasible though, since routing lasers is expensive at best.
.cig - what you do after winning a good flame war
If I understood this article correctly, the laser transforms heat (disorganized energy) into laser light (more organized?). Wouldn't this cause a net decrease on entropy in the system?
Something similar to this was posted a bit ago on Slashdot, but what the hell.
With a turbine engine, kinetic energy is extracted by hot-air through turbines, which in turn suck in air, compress it, combust it, etc. Cyclic compression and expulsion creates thrust, or rotational energy on the turbine shaft (which is what turbo-prop airplanes, APU's, helicopters and generators use).
This technology might have applicability for turbines which use rotational energy from the shaft. For instance, the APU on a 777 is a fairly large turbine engine. Would it be possible to lower its running RPM by using converted heat from the exaust stream as a secondary source of power? This would of course lower fuel consumption while the APU is running, as well as extend the time between overhaul for it.
Anyhow, essentially: this technology, if viable, could have serious use within turbine engines, since they waste a significant amount of heat in operation.
So, what's stopping you?
Home Power magazine is a good place to start for ideas and things.
And if you come up with something that runs a net surplus, sell the power back to your local government mandated utility. Most government grants of monopoly for electrical power include a requirement that the utility buy back what you as a private individual produce.
Not all, you can be sure, but HomePower has good information sources on that.
You could, of course, spend a decade lobying governments and buying influence with the politicians, but that would just make you another Enron. It's much more efficient to just build it yourself.
Bob-
The Ludwig von Mises Institute. The reasoning individuals economics
The whole idea seems like a good way to write a paper, get published and generate hot air, but not a good way to increase energy efficiency. Kinda like our current projects to build a fusion reactor ("We've already got one, fer Christ's sake! It's called the sun.").
There is no trap so deadly as the trap you set for yourself
-Raymond Chandler, The Long Goodbye
What you are refering to is VE(Volumetric Efficiency). VE is a major factor in the specific output(PS/Liter or HP/Cubic Inch). Regardless of VE, what we really are looking at is raising BSFC. That is Brake Specific Fuel Consumption. This number shows how much gasoline is required to produce horsepower. New electronically-actuated valves will do much to raise this. On a 4-valve cylinder, over 20% of the engine output is used soley to spin the camshafts and plunge the valves up and down quickly.
Turbocharged engines help by absorbing some of this engine's exhaust and 'reinvest' this kinetic and thermal engergy in the intake. However, it is a losing proposition; even with an intercooler, the more boost you pump, the hotter the intake charge gets. You quickly develop a cycle where you must retard timing to reduce preignition and detonation thus raising exhaust temp's even more. The retardation of the ignition severely reduces power output thus nullifying any boost pressure you are running anyways.
No, turbochargers are good for increasing VE , but do little to alter the fundamental(thermal) efficiency of an engine.
We need a revolution.
You can't legislate goodness. Let each to his own destiny, by will of his freely made choices.
Yes, we do, actually.
And all these years I thought quantum mechanics just meant when you get one part on your car fixed, another part breaks.
and it is a pretty interesting idea. I'm not sure about the practical feasibility of the concept for reasons I'll get into below. But, it shows that quantum effects might be usefully exploited to make better engines and will probably prompt a fair amount of thought and experiment into the matter.
... thanks lameness filter ... less than signs could never be useful).
... more molecules must be in one of the upper states than in the lower states. However, in a gas at thermal equilibrium, this is usually not the case ... the probabiliy of finding a given quantum state in state with energy E is proportional to exp(-E / kT ). Here, k is Boltmann's constant and T is the ambient temperature. At low temperatures, the ground state will be where most of the molecules are.
... "b" molecules to preferentially transistion into the ground state (state "c"). However, the "a" population won't be able to come to equilbrium that fast (provided the spontaneous emission rate is sufficiently low and the maser cavity isn't tuned to enhance the transition rate out of "a" state). This net impact of the maser is to create a population inversion between the "a" and "b" states. By passing the non-thermal maser cooled gas into a laser cavity tuned to the "a"-"b" transition, this inversion can be extracted as laser energy. This is the quantum afterburner part.
... involving passing the gas back and forth through two pistons. I'm pretty sure that materials and a simplified engine design could be made to validate the claims though.
Warning: Ph.D. punditry follows.
Suppose a molecule has three possible states ("a", "b" and "c") with energies E_c, E_b, E_a respectively (E_c is the ground state and E_b is the between E_a and E_c
Suppose further, microwave (maser) energy transitions are possible from state "b" to "c". Optical (laser) transitions are possible from "a" to "b".
For lasing to occur, you must have a population inversion
If the hot exhaust gas is first passed through a maser cavity tuned to the "b"-"c" transition containing a radiation field at the temperature of the cold reservior, the "b" and "c" populations will quickly come to thermal equilibrium with the low temperature radiation field
From a quantum standpoint, nothing is particularly new here. Using rapid cooling of a selective population to create inversion is pretty unique but nothing that can't be explained with the standard laser rate equations.
From a purely statistical mechanics standpoint, the net effect is to extract extra useful work from internal degrees of freedom of the working fluid. Statistical mechanics is not my forte so I can't really say if this is particularly out there.
From a practical standpoint, it might be hard to find gases at engine temperatures and gas pressures where the low spontaneous emission lifetimes necessary to sustain the inversion is possible. My intuition says that collisional de-excitation (high temp and pressures) would wipe out the inversion. Also, the exact scheme discussed in the paper is more complicated
As a thought experiment, though, this shows that it may be possible to improve the efficiency of an Otto engine. (By the way, the paper notes that a Carnot cycle efficiency doesn't get a boost from the technique.)
Kevin
Every time I see that Ben Franklin quote, I'm reminded that while many Americans risked (and lost) their lives to throw off British rule, Franklin "suffered" by staying in France during the revolution. I guess he didn't mind his own safety being secure while other people fought. Hypocrite.
-jon
Remember Amalek.
Nit to pick: you mean time-reversal invariance, not time-translation. Symmetry under time-translation is related to conservation of energy, not reversibility.
Not to start whining again about the second law of theromodynamics, but the laser and the maser also have to be powered. Since one uses the laser to depopulate the second excited level, the laser emission has to come from the 1-> 0 transistion. The emitted laser emission is probably of less energy than the first one.
Also laser and maser have to be powered and somehow I think this takes a whole lot of energy more than a normal car enigine can supply.
Then also the fact remains as already noticed by other replies what does one want to do with the laser-light obtained? (this also follows the 2nd Law)
Same with classical mechanics, and more so, as QM has the "destructive measurement" hypothesis, that by merely measuring that an object is in a given state, you collapse any state superposition in which it might have been. Besides, Statistical Physics and Thermodynamics have borrowed quite a lot from QM (particles being in given states among a number of possible ones, etc.)
Yes, this comes from the fact that there exists a great many more possibilities that waste heat will be irrecoverably produced. It might stay in a usable form, just as you might open a bottle of ink under water, and the ink might flow out and then all crawl back into said bottle. It is just highly unlikely.
There is no need for an arrow of time at the microscopic level for that.
As for the paper itself, if I understand the summary correctly, it is ingenious but I'd look for a catch, such as the maser requiring at least as much power to function as that you can extract from the waste heat... Wouldn't that be annoying?
(And many thanks to all the scientists who publish on arXiv).
"Ya see, we're kinda afraid that if we observe the problem it might alter the system and give you a totally different problem..."
"Well, we're not quite sure where your car is, but we do know exactly how fast it's moving... Would you prefer the other way around? 'Cause I can do that instead if you want..."
--
Damn the Emperor!
Whilst this may be true for "plain old QM" as embodied in the Schrodinger equation, for example, the Quantum Field Theories of modern particle physics certainly are not time-reversal invariant.
QFTs such as the standard model are provably invariant under a symmetry known as CPT. This is the combination of three individual symmetry operations:-
The decay of neutral K-mesons (or kaons) measurably violates CP This implies a violation of T if CPT is to be preserved. The Standard Model (Glashow-Weinberg-Salam) incorporates CP violation, albeit in a kludgy manner (imaginary values in the Cabibbo-Kobayashi-Maskawa (CKM) mixing matrix)
Google for "CP-violation" for reference links
Paul Davies wrote a lay-persons book exploring the different "natural arrows of time" in physics including CP violation and 2nd Law of thermodynamics called (duh!) "The Arrow of Time" although I haven't read it (but have read other of his books).
OT: Flanders and Swann wrote a song (v. funny) about the first and second laws of thermodynamics.
if I understand correctly, this would amount
to a kW range infrared laser available
"for free" in the car. You can then
shoot down birds, 007 style (gives a new meaning to roadkill)
do some welding in the car while driving
punish tailgaters on the spot
have a very trendy cigarette lighter that saves some fuel
...
Google passes Turing test : see my journal
... you can always run SETI@Home.
--
"By the way if anyone here is in advertising or marketing... kill yourself." -- Bill Hicks
If you are the military that is.
1. Extracting waste heat reduces vehicle heat signature.
2. Even an extra few miles per gallon of feul means substantially less logistic headaches. The Gulf War, for example, was considered a triumph of efficient logitics because the Abram tanks were incredibly feul thirsty.
Ofcourse it should be "you CAN'T convert all heat energy..." rather than "you CAN convert..."
Gentlemen, you can't fight in here, this is the War Room!
Doesn't anybody else find it at least slightly funny that someone is proposing putting a Quantum Afterburner (TM) on a piston engine, the essential design of which is 125 years old? After all, there are other ways to recover waste heat in the exhaust that we could be using now, but aren't. Peltier junctions could be used to generate electricity to supplement or replace the function of the alternator once the engine was hot. Someone else here mentioned stirling engines. Maybe that'd be another way to increase the efficiency. Again, maybe you could drive the alternator with it. Of course, the alternator only uses maybe 1 or 2 horsepower anyway, so even eliminating that drag on the engine is only going to be a small improvement.
Than again... how many horsepower does a car use when cruising? Maybe eliminating 1 or 2 horsepower would make a difference. I would assume that this Quantum Afterburner (TM) would be able to recover a much greater amount of the waste heat, too, so maybe it would make quite a difference.
P.S. -- before anybody starts to rant on me for using horsepower, remember, there are metric horsepower too! According to my unit converter, one horsepower equals 1.01387 metric horsepower. Guess the French have different sized horses than the English! Cheers!
I'm no engine expert, but doesn't anything that impedes the flow of exhaust gasses interfere with the internal combustion process, making the engine less efficient? The two-poston contraption these guys are using would certainly seem to fall into that category, if they tacked it into the car's tailpipe.
Patrick Doyle
I mod down every jackass who puts his moderation policy in his sig. Oh, wait a sec....
Alas *this* paper has nothing to do with violating 2nd law. It is not a gedanken experiment either, its a real device. I guess you should read the article from time to time.
Gentlemen, you can't fight in here, this is the War Room!
it is absolutely possible to increase the efficincy of even a perfect otto engine. that is because the best otto engine could never convert more than ~70% (?) of the input energy into mechanical output.
what it comes down to is that if you take just the exhaust pipe as a seperate system you have a differential in temperature, and such an energy potential can always be used to produce useful work
forgot about the less than sign in the title... seems like that should be automatically converted to < automatically with plain text submissions
oh well
Sort of on topic, considering the number of comments being posted about heatsink fans (even though the article has little to do with it): why noone ever figured out a way to use the hot air being expelled by the system fan to turn something that would generate electricity. Can't some of it be recycled back to power the system?
Alright, this thing is still strictly theoretical, right?
Correct me if I'm wrong, but isn't the internal combustion engine at the beginning of it's decline now? I mean, how long will it be before this effect is put to use? A decade? More?
I suppose since the article keeps talking about waste heat generated by the engine, rather than any features particular to the engine, there might be other uses than prolonging the life of a technology...but then why put everything in terms of "the Otto engine?"
Well, anyhow, I'm sure car buffs 20 or 30 years from now will be glad to have such a device to help keep their old 20th century vehicles street-legal.
related to the Otto Pilot?
You never really know how close to the edge you can go until you fall off.
Off topic, but the second law of thermodynamics only applies to systems in equilibrium with their active environment.
G. Nicolis and I. Prigogine, (1987), Exploring Complexity, Piper, Munich, 1987.
Gregoire Nicolis, "Physics of far-from-equilibrium systems and self-organization," Chapter 11 in Paul Davies, Ed., The New Physics, Cambridge University Press, Cambridge, 1989, p. 317-347.
Ilya Prigogine, The End of Certainty: Time, Chaos, and the New Laws of Nature, Free Press, New York, 1996, 1997.
Systems in disequilibrium with their environment are allowed to:
1. self-order
2. self-oscillate or self-rotate
3. output more energy than the operator inputs (the extra energy is received from its active environment)
4. power itself and its loads simultaniously
5. exhibit negentropy
Just a little FYI to get you up to speed with modern physics.
The only problem is these "quantum afterburners" are probably not going to be light... or small... or cheap... and they'd stop you at the airport and take it apart thinking it was a bomb, and then you'd be out a lot of money. Did you know they sell extra batteries for laptops? Maybe that's a better route! :-)
"Da ist ein Technölüst in mein Unterpanten!"
The Second Law is really a statement about probabilities and how you count macrostates and microstates, and so doesn't have to be present in microscopic physical laws because it doesn't mean much there anyway.
Hey, I never said it would be super efficient. Just way more efficient than sticking a laser on a tail pipe. For hybrid cars, where every Wh counts, stirling engines may be worth looking into though.
And yes, the best place for a Stirling engine is on a stick (above a parabolic reflector).
There is no trap so deadly as the trap you set for yourself
-Raymond Chandler, The Long Goodbye
It was the French who kept the British away from their reinforcements, otherwise the Colonists army would've been crushed by the second wave. As such, don't you think it was better for Franklin to be there to plead the Colonists case instead of dying in the mud? Without France, all the people who died would've died in vain.
Ah, finally an explanation for "The Emperor's New Mind"!
yes. you are right of course. I was talking about plain vanilla QM. In QFT, CFT is the symmetry that we should care about.
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Its called a turbo.
Granted its much less efficient than a quantum level interaction but thats what a turbo does; reuse the exhaust causes to spin up a turbine. The turbines used then to compress air coming into the engine and raise the efficiency of the engine.
I think all that jargon is what I called "do work". :P
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Heh.
:P.
RP came over here to Chicago to give a colloquim once and he went about telling us how all current theories (string theory, inflation, cosmology etc) are all wrong because they do not incorporate/violate the 2nd law in some form. There was a lot of glancing of faces and rolling of eyes
It was a very provocative talk though.
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Why hasn't anyone mentioned applying this technology to fuel cells?
What's powering the lazer-mazer combo?
Say, what's with thi anti Cmmander tach rhetoric?