I’ve always been fascinated by the thermocouple and its ability to generate electricity from heat. I’ve often wondered if we could put millions of thermocouples into places where heat is a byproduct of some other operation and capture it as electricity. That may soon happen.
From light.sci-toys.com: In 1821, physicist Thomas Johan Seebeck discovered an interesting effect when he heated a junction of two different metals. He found that they generated an electric current. Actually, he thought it was a magnetic effect, because what he had noticed was that a compass needle was deflected as the current flowed through the wire.
Today, we call the thermoelectric effect he discovered by his name — the Seebeck effect. He must have had a very sensitive compass, because the currents that are generated are very small. Unless the wires are formed into a coil around the compass, to increase the magnetism of the current carrying wire, it would be difficult to notice any movement.
But a modern voltmeter is sensitive enough to show the effect, as shown in the photo. Now that concept has literally taken a quantum leap.
From University of Arizona News – Quantum physicists turn waste heat into power
University of Arizona physicists have discovered a new way of harvesting waste heat and turning it into electrical power. Taking advantage of quantum effects, the technology holds great promise for making cars, power plants, factories and solar panels more efficient.
What do a car engine, a power plant, a factory and a solar panel have in common? They all generate heat – a lot of which is wasted.
University of Arizona physicists have discovered a new way of harvesting waste heat and turning it into electrical power.
Using a theoretical model of a so-called molecular thermoelectric device, the technology holds great promise for making cars, power plants, factories and solar panels more efficient, to name a few possible applications. In addition, more efficient thermoelectric materials would make ozone-depleting chlorofluorocarbons, or CFCs, obsolete.
The research group led by Charles Stafford, associate professor of physics, published its findings in the September issue of the scientific journal, ACS Nano.
“Thermoelectricity makes it possible to cleanly convert heat directly into electrical energy in a device with no moving parts,” said lead author Justin Bergfield, a doctoral candidate in the UA College of Optical Sciences.
“Our colleagues in the field tell us they are pretty confident that the devices we have designed on the computer can be built with the characteristics that we see in our simulations.”
“We anticipate the thermoelectric voltage using our design to be about 100 times larger than what others have achieved in the lab,” Stafford added.
Catching the energy lost through waste heat has been on the wish list of engineers for a long time but, so far, a concept for replacing existing devices that is both more efficient and economically competitive has been lacking.
Unlike existing heat-conversion devices such as refrigerators and steam turbines, the devices of Bergfield and Stafford require no mechanics and no ozone-depleting chemicals. Instead, a rubber-like polymer sandwiched between two metals acting as electrodes can do the trick.
Car or factory exhaust pipes could be coated with the material, less than 1 millionth of an inch thick, to harvest energy otherwise lost as heat and generate electricity.
The physicists take advantage of the laws of quantum physics, a realm not typically tapped into when engineering power-generating technology. To the uninitiated, the laws of quantum physics appear to fly in the face of how things are “supposed” to behave.
The key to the technology lies in a quantum law physicists call wave-particle duality: Tiny objects such as electrons can behave either as a wave or as a particle.
“In a sense, an electron is like a red sports car,” Bergfield said. “The sports car is both a car and it’s red, just as the electron is both a particle and a wave. The two are properties of the same thing. Electrons are just less obvious to us than sports cars.”
Bergfield and Stafford discovered the potential for converting heat into electricity when they studied polyphenyl ethers, molecules that spontaneously aggregate into polymers, long chains of repeating units. The backbone of each polyphenyl ether molecule consists of a chain of benzene rings, which in turn are built from carbon atoms. The chain link structure of each molecule acts as a “molecular wire” through which electrons can travel.
“We had both worked with these molecules before and thought about using them for a thermoelectric device,” Bergfield said, “but we hadn’t really found anything special about them until Michelle Solis, an undergrad who worked on independent study in the lab, discovered that, low and behold, these things had a special feature.”
Using computer simulations, Bergfield then “grew” a forest of molecules sandwiched between two electrodes and exposed the array to a simulated heat source.
“As you increase the number of benzene rings in each molecule, you increase the power generated,” Bergfield said.
The secret to the molecules’ capability to turn heat into power lies in their structure: Like water reaching a fork in a river, the flow of electrons along the molecule is split in two once it encounters a benzene ring, with one flow of electrons following along each arm of the ring.
Bergfield designed the benzene ring circuit in such a way that in one path the electron is forced to travel a longer distance around the ring than the other. This causes the two electron waves to be out of phase once they reunite upon reaching the far side of the benzene ring. When the waves meet, they cancel each other out in a process known as quantum interference. When a temperature difference is placed across the circuit, this interruption in the flow of electric charge leads to the buildup of an electric potential – voltage – between the two electrodes.
Wave interference is a concept exploited by noise-cancelling headphones: Incoming sound waves are met with counter waves generated by the device, wiping out the offending noise.
“We are the first to harness the wave nature of the electron and develop a concept to turn it into usable energy,” Stafford said.
Analogous to solid state versus spinning hard drive type computer memory, the UA-designed thermoelectric devices require no moving parts. By design, they are self-contained, easier to manufacture and easier to maintain compared to currently available technology.
“You could just take a pair of metal electrodes and paint them with a single layer of these molecules,” Bergfield said. “That would give you a little sandwich that would act as your thermoelectric device. With a solid-state device you don’t need cooling agents, you don’t need liquid nitrogen shipments, and you don’t need to do a lot of maintenance.”
“You could say, instead of Freon gas, we use electron gas,” Stafford added.
“The effects we see are not unique to the molecules we used in our simulation,” Bergfield said. “Any quantum-scale device where you have a cancellation of electric charge will do the trick, as long as there is a temperature difference. The greater the temperature difference, the more power you can generate.”
Molecular thermoelectric devices could help solve an issue currently plaguing photovoltaic cells harvesting energy from sunlight.
“Solar panels get very hot and their efficiency goes down,” Stafford said. “You could harvest some of that heat and use it to generate additional electricity while simultaneously cooling the panel and making its own photovoltaic process more efficient.”
“With a very efficient thermoelectric device based on our design, you could power about 200 100-Watt light bulbs using the waste heat of an automobile,” he said. “Put another way, one could increase the car’s efficiency by well over 25 percent, which would be ideal for a hybrid since it already uses an electrical motor.”
So, next time you watch a red sports car zip by, think of the hidden power of the electron and how much more efficient that sports car could be with a thermoelectric device wrapped around its exhaust pipe.
Reference: Giant Thermoelectric Effect from Transmission Supernodes. Justin Bergfield, Michelle Solis, and Charles Stafford. ACS Nano Sept. 2010.
That table of Seebeck coefficients is nice to have; especially if one is doing highly sensitive DC measurements and wants to keep thermal EMFs at a minimum.
The Bismuth / Anti-money combination is one of the more common junctions used for thermo-electric generators.
About all that one can say about Bismuth, is that it is a very poor excuse for a metal.
I recommend that you stay away from the Tellurium though. I don’t care if I die, before I ever get a look at a piece of Tellurium.
We used to use about 5 ppm or thereabouts of diethyl Telluride in Hydrogen for N Type doping of Gallium Arsenide, and Gallium Arsenide Phosphide Epi layers for Red LEDs. Easily wins my vote as THE most obnoxious odor in the Universe.
“Like water reaching a fork in a river, the flow of electrons along the molecule is split in two once it encounters a benzene ring, with one flow of electrons following along each arm of the ring.”
I hope this awful analogy is from the article writer and not the researchers. It would have water flowing uphill!
Quite a few attempts have recently been made to recover exhaust heat energy from vehicle engines.
BMW has another concept to recover waste heat from the exhaust http://www.gizmag.com/go/4936/.
In this concept the exhaust is routed to a heat exchanger to create steam and drive a small steam engine. The steam engine is coupled to the transmission. Supposed to reduce fuel consumption by about 10-15%, but only when the car is mainly used for long distance driving.
The working fluid is an alcohol/water mix and runs closed loop with a condensor mounted up front.
Of course, any competent mechanic can easily bybass the steam engine and convert that car into a mobile moonshine still. Seems like a concept NASCAR would love.
Another way to recover the waste heat from an internal combustion engine that I find interresting is the 6-stroke Crower engine:
http://en.wikipedia.org/wiki/Crower_six_stroke
In this engine, instead of exhausting the burned gas directly out the exhaust pipe, it is recompressed (5th stroke) and at the end of that compression cycle water is injected directly into the combustion chamber. This water flashes into steam and allows the engine to produce another (6th stroke) power cycle before the (then relatively cold) mixed gas is exhausted.
Of course the problem there is that it requires a water tank or large condensor, and the remaining exhaust heat is too low to operate a catalytic converter.
Eric Gisin says:
September 29, 2010 at 7:55 am
I hate it when reporters say N football fields or 200 X 100W. Just say 20KW.
A small ICE producing 10KW will propel a small car on the highway. I does produce 20KW+ of waste heat. But most of it is low quality, not the high temp of exhaust. All heat engines become less efficient with small heat difference, I expect thermocouples have a max theoretical efficiency too. I doubt thermocouples on the exhaust can produce more that a few KW electricity.
You may well be correct, but at the moment we use Mechanicly driven Alternators to do the same thing and they sap energy from the engine that could be going to the wheels.
So if it is free energy and can replace the Alternator I disagree with
George E. Smith says:
September 29, 2010 at 8:03 am
Not only could this reduce waste, it could also eliminate the need for nuclear plants to build cooling towers. That would make them more competitive.
Could it maybe drain excess heat from computer chips?
As a chemist, I’d predict that those molecules will lie flat on the bottom electrode surface, to maximize contact. That would be the most stable configuration of a polymeric molecule.
I can’t see how they’d get a “forest” of those molecules standing up like that. People make electrodes covered with a “lawn” of molecules, but typically the way it’s done is to make the molecule linearly asymmetric.
One terminus of the molecule is made to have far more affinity for the electrode than the rest of the molecule. So, the low-energy position is to stand on end. I don’t see any modification of the molecular terminus to achieve that status in the picture, but maybe they’ve simplified it for publication.
I can also see how the current might bifurcate around the molecular rings. But notice that the longer path will also be higher resistance. So, the amplitude of current is unlikely to be bilaterally symmetric around the ring. That means the phase cancellation won’t be complete. Presuming the device works as advertised, the incomplete cancellation may impact the available energy.
As usual, the engineering study will tell the tale.
Only ONE way to handle this announcement:
http://www.solargeneral.com/humor/bs-meter.gif
Please note the position on this HIGHLY SCIENTIFIC DEVICE!
Enneagram says:
September 29, 2010 at 9:29 am
A weirder idea?
Not at all. Solar energy vs earth gravity.
At night balloon will cool down (pV=nRT), loose volume and drop down a bit (so you can use some of the energy stored while was going up) to partially wind it back, next day sunshine will worm it up, increasing the volume, and balloon goes up again. Lots of free energy!
Steamboat Jack says:
September 29, 2010 at 7:12 am
“But, the distance between Th and Tc is the thickness of the polymer coating: “…less 1 millionth of an inch thick”.
Yeah. If they think it’ll work on an exhaust pipe those aren’t very hot either for a useful thermopile. I’m presuming you spray it on metal and need the usual radiator fins. I’d sure love to see the performance curves they think they’re going to get. Something 20% efficient at say 160F that was much cheaper to produce than solar cells would be a bit earth shaking. 160 is easy to get with solar. Just heat water in an insulated tank to that temperature and draw it off through the thermopile as needed. You could use a propane or natural gas fired water heater as a backup or to top off the temperature if the sun wasn’t doing it. Hell even 10% efficient and same price as a solar cell would be awesome as you can’t power a solar cell from stored hot water. That alone would make it hugely attractive since it makes energy storage inexpensive, long lived, and almost maintenance free.
Dave Springer- “Something 20% efficient at say 160F that was much cheaper to produce than solar cells would be a bit earth shaking.”
The Thermoelectric efficiency is ultimately limited by the Carnot efficiency, which is eff = T(hot) – T(cold))/T(hot), all in degrees Kelvin. This is the limit for an infinite Thermoelectric figure of merit. Assuming T(cold) = 273 K, and T(hot) = 160 F = 345 K, the best you can do is 21%. So as you say, it would be earth-shaking indeed.
“”” A C Osborn says:
September 29, 2010 at 10:08 am
Eric Gisin says:
September 29, 2010 at 7:55 am
I hate it when reporters say N football fields or 200 X 100W. Just say 20KW.
A small ICE producing 10KW will propel a small car on the highway. I does produce 20KW+ of waste heat. But most of it is low quality, not the high temp of exhaust. All heat engines become less efficient with small heat difference, I expect thermocouples have a max theoretical efficiency too. I doubt thermocouples on the exhaust can produce more that a few KW electricity.
You may well be correct, but at the moment we use Mechanically driven Alternators to do the same thing and they sap energy from the engine that could be going to the wheels.
So if it is free energy and can replace the Alternator I disagree with
George E. Smith says:
September 29, 2010 at 8:03 am “””
Well in a well designed alternator, the input energy is “real” ordered mechanical energy; the exact same sort of energy that is getting the car along the road. Very little of that energy is wasted as mechanical friction losses in the bearings, and belt drive; although they don’t exactly bend over backwards to get it to absolute minimum.
And the conversion into electric energy (from mechanical) is also very efficient. Well for practical reasons to keep the thing small, they tend to run the copper wire at a relatively high temperature; just to keep the amount of copper required at a minimum. And for the same reason; they run the magnetic flux density in the magnets at a fairly high level to reduce the amount of good magnetic steel or other alloy. So they typically run the total mechanical to electrical energy exchange efficiency at some compromise level that keep the size and cost down; but inherently the conversion from mechanical to electrical is almost 100%. It is in the extraction of the electricity from the alternator, that one incurs losses due to electrical resistance, and magnetic hysteresis and eddy current losses.
So good luck on getting your thermo-electric converter to even approach the efficiency of an automobile alternator efficiency; I’ll stick with what has been proven to work; but if thermo converters eventually take over; I’ll switch. I would rather spend the research effort trying to improve the efficiency of the car’s engine; so it didn’t make so much waste heat in the first place.
And remember that those polluting internal combustion greenhouse pollution producing engines are going to be replaced by free clean green renewable electric cars anyway; so there isn’t going to be any hot exhaust pipe to scrape thermo electricity from.
But I’m always happy to have people disagree with me; that way if they get richer than me; they can take over paying some of the taxes I have to pay; because my employer wants to keep me working.
I liked the references to Freon and CFCs. Don’t they know that these materials have been phased-out as refrigerants already, and that a 2nd generation of replacements will be introduced in the next 3-5 years that essentially have no ozone-depleting effects or greenhouse effects either (first generation replacements were HCFCs and HFCs).
Metryq says: September 29, 2010 at 4:20 am
“@Kaboom, before you poke fun at someone else’s typos (although your gags were funny”
No offence taken, and it was funny.
I’ve done worse.
Try leaving the ‘l’ out of public when the context is “there should be more public access at the meetings”. Spell checks ok, but…
“With a very efficient thermoelectric device based on our design, you could power about 200 100-Watt light bulbs using the waste heat of an automobile,” he said. “Put another way, one could increase the car’s efficiency by well over 25 percent, which would be ideal for a hybrid since it already uses an electrical motor.”
I am surprised that nobody has yet commented that the above claim is complete and utter nonsense. It violates the laws of thermodynamics and is simply a 21st century version of that age-old chestnut: the perpetual motion machine.
To the extent that the thermopile generates electricity, it derives that energy from the car’s fuel and in so doing it make the internal combustion engine proportionately less efficient, thereby reducing its power output. This is essentially a zero-sum game with no efficiency benefit whatsoever. (And in practice there would actually be an efficiency loss due to having to convert the electricity generated back into motive power.)
Daft or what?
Wow, this is a bit of a game-changer, isn’t it. Makes it obvious what a nonsense subsidies for PV panels are. Looks like the best way to generate electricity from the sun will be to bury a field full of pipes, run water through them, and use the new tech to generate electricity from the temperature difference. Ground source heating -> electricity is a win, particularly considering it can be installed on agricultural land deep enough that it won’t interfere with agriculture – no land cost.
As Steamboat Jack has said “The greater the temperature difference, the more power you can generate.
But, the distance between Th and Tc is the thickness of the polymer coating: “…less 1 millionth of an inch thick”.
Yes, the driving force for any thermocouple is the delta T between the hot and cold junctions, so even thermocouples have to obey the Second law of Thermodynamics. It is implied from the way this article is written we can just directly convert any heat that is lying around into electricity, not true. So the skeptic in me wonders how they intend to maintain a heat difference between junctions that are angstoms apart.
Vuk etc. says:
September 29, 2010 at 10:33 am
Ho,Ho!, just don’t say it aloud!, that would work as a hanging up machine too 🙂
Pat Frank says:
September 29, 2010 at 10:19 am
As a chemist, I’d predict that those molecules will lie flat on the bottom electrode surface, to maximize contact. That would be the most stable configuration of a polymeric molecule.
Pat, I don’t know. I’m just speculating. But maybe there’s an entropic driving force for a forest. And from the viewpoint of enthalpy, maybe you get more of an advantage by sorbing many more molecules on end, in the sense of each absorption being stronger than an equivalent number of surface interactions from fewer molecules lying flat. A multiply-sorbed molecule has “less to give”.
Rhys Jaggar says:
September 29, 2010 at 12:09 am
The only question I would ask about that technology is how you create a ‘wire’ if the benzene ring side chains in the wire backbone are at positions 1 and 3
Rhys – There is an electronic preference for the (using your numbering scheme) 1 and 4 positions when the polyphenyl ether is formed, due to differences in electron density (and assuming the substitution is electrophilic). So, we don’t have to worry about the 3-position. I’m sure there is some chemical trick to getting consistent substitution at the 1-position. But I can’t tell you what that is, unless it’s a surface-catalyzed reaction that convinces the ring to lie on its side with the oxygen sticking away from the surface, leaving the 1-position accessible, but blocking the 4-position.
oeman50 says:
September 29, 2010 at 12:28 pm
Yes, the driving force for any thermocouple is the delta T between the hot and cold junctions, so even thermocouples have to obey the Second law of Thermodynamics. It is implied from the way this article is written we can just directly convert any heat that is lying around into electricity, not true.
I don’t understand. Are we talking about two different processes here? Look at the picture at the beginning of the article where a candle is directly heating the junction between two metals and is creating a voltage difference. That doesn’t seem to hinge on “the delta T between the hot and cold junctions.” Is the Seebeck Effect different from a thermocouple? Can someone clarify?
“”” David Socrates says:
September 29, 2010 at 11:38 am
“With a very efficient thermoelectric device based on our design, you could power about 200 100-Watt light bulbs using the waste heat of an automobile,” he said. “Put another way, one could increase the car’s efficiency by well over 25 percent, which would be ideal for a hybrid since it already uses an electrical motor.”
I am surprised that nobody has yet commented that the above claim is complete and utter nonsense. “””
Well David; you haven’t been reading very closely. Several people have commneted on the p[racticality of this scheme.
Actuallt it doesn’t have to violate the second Law; well of course it can’t so that is a non issue. But the second Law does place some restrictions on the amount of electricity one might recover from the waste heat.
It’s a bit like running a stable with a lot of horses that you feed hay to. The result is you end up with a lot of HS which is the Equine equivalent of BS.
So this thermo-electric scheme lets you burn the HS, for waste heat which you use to run your TE plant.
Well if you wanted to improve the efficiency of this stable; figuring out how to use up the HS effluent is not the answer.
It would be better to breed a better kind of horse that uses the pristine hay more efficiently and doesn’t excrete as much HS. Or you could mix the hay that has already been once through the horse, in with the hay or oats and recycle it. Of course that kind of Hay comes quite a bit cheaper; but better to rerun it to create extra horse power than to just burn it.
Using up waste heat is old hat. Most of you are too young to remeber the North American Mustang (aptly named); otherwise known as the P-51 WW-II fighter. It had this weird radiator power bulge sticking out under its belly so that when it was engaged in strafing ground targets; the bullets could kick up stones off the road, to punch holes in the radiator.
Everybody thinks the P-51 radiator was a nifty design because when the air rushed through it and out the back, it was heated by the radiator cooling fluid, and that expanded the gas, and raised the exhaust velocity and momentum to give a slight jet engine thrust to the plane from that waste heat. This is often touted as one of the superior design features of the P-51.
Actually, it was a ho-hum thing. You see back in 1935 when Supermarine was developing the prototype for Reginald Mitchell’s Spitfire fighter, a chap by the name of Meredith who worked for the British Royal Aircraft establishment figured out the theory of such a radiator design; in fact is has become known to history as The Meredith Radiator.
Properly implemented the conversion of waste heat from the cooling fluid, into extra thrust, is so efficient that the generated thrust exceeds the aerodynamic drag caused by the crossection of the radiator and its housing.
And that very successful Meredith Radiator was implemented on K 5054 when it flew its maiden flighton March-5 1936, and every single Spitfire built thereafter hada Meredith Radiator tucked under one wing.
The extra thrust developed by the radiator from waste heat easily made up for the drag of having it out there in the open.
So the p-51 was a somewhat poorly executed copycat affair. But make no mistake it was an excellent fighter; among the best ever.
But Iprefer to raise the engine efficiency by lowering the exhaust Temperature, rather than wasting a lot of hay on inefficient horse that just convert most of it to HS.
FTA: “We anticipate the thermoelectric voltage using our design to be about 100 times larger than what others have achieved in the lab,” Stafford added.
That’s nice and all, but current/power capacity is what’s needed.
As someone who has actually done car exhaust work, I doubt an exterior pipe coating of less than a millionth of an inch will survive long enough to be useful.
Apparently these researchers don’t realize the confusing mess that is current vehicle exhaust systems. Catalytic converters need to be hot to work effectively. Nowadays engines can run very efficiently, relatively, which is a problem. Extra air can be added so there’s enough oxygen for the catalytic to work, which cools the exhaust thus reducing effectiveness. There are combustion products that require a hot catalyst to be converted, endothermic reactions. So, the engine runs slightly rich to let through some unburned hydrocarbons, providing exothermic reactions which yield sufficient heat. Some engine inefficiency is thus built in for pollution reduction.
You end up with exhaust being no hotter than it has to be, with water frequently seen dribbling out of tail pipes. There’s been a changeover to stainless steel due to exhaust pipes rusting away from the inside. There’s not much available energy anyway.
You might be better off on the other end, the radiator throws off a lot of heat. Even more with modern engines, as they run hotter to be more efficient. Thermostats, which set the temperature limit at which coolant is sent to the radiator thus control the engine temperature, used to be rather low, 160-180°F. Nowadays engines run so hot the limit is the coolant, they’re talking about switching to something other than water-based to go higher that 220°F with a pressurized system. The question becomes, is there enough energy available to make it worthwhile to switch to a thermoelectric energy recovery unit instead of a radiator?
But then I wonder how one can recover such “waste” heat, as the goal is to dump the heat to the atmosphere and do it quickly. How can that be done while extracting energy?
Dave Springer says:
September 29, 2010 at 4:45 am
Coat the radiator with this material also.
Picures of Russian Lamp thermoelectic generators
http://www.radiomuseum.org/r/unknown_thermo_generato_tgk_3tgk.html
Please Everyone! We Must Think Positively About All This! We went from vacume tubes to transisters to integrated circuits and 1.21 gigabites at the drop of a hat. Now it’s time for something new. Don’t be negative and put the quash on it. Think positive! This is the 21st Century!
😉