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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."
Can be found here (in PDF form), for all those who like reading physicists physics.
There's no reason for a sig here.
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.
I interned at Delco Electronics (now Delphi Automotive) who develop HVAC and electronic systems for automobiles, and I asked a similar question. Why not pipe the exhaust through the seats and use it to quickly heat the interior? It turns out that the risk of leaking exhaust fumes into the cabin is too great to allow such a design. The exhaust could quickly overcome the driver, and lead to an accident or death, even if parked.
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
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
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.
(And many thanks to all the scientists who publish on arXiv).
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!
Guys, have none of you ever heard of Carnot cycle, how it outputs only 1 unit of work for about 3 units of heat supplied? (the reverse also holds, with 1 unit of work you can pump about 3 units of heat) And that an ideal Carnot cycle is the most efficient heat pump? Otto, diesel, rankin and all other cycles output less amount of work than carnot for a given amount of heat. So it is perfectly OK for something to beat an ideal otto cycle as long as it doesn't beat Carnot.
Repeat after me:
1- Heat->Work conversion is never 100% for even the most efficient ideal machine. It doesn't even come close.
2- An ideal Otto cycle is not the most efficient cycle around. Ideal Carnot beats it, and every other cycle too.
3- No, the device+otto doesn't beat carnot. Normality restored, no laws violated.