Quantum physicists turn waste heat into power

Sep 24, 2010 By Daniel Stolte
A "forest" of molecules holds the promise of turning waste heat into electricity. UA physicists discovered that because of quantum effects, electron waves traveling along the backbone of each molecule interfere with each other, leading to the buildup of a voltage between the hot and cold electrodes (the golden structures on the bottom and top). (Rendering by Justin Bergfield)

(PhysOrg.com) -- 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 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 more efficient, to name a few possible applications. In addition, more efficient thermoelectric materials would make ozone-depleting , 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.

Explore further: Team finds electricity can be generated by dragging saltwater over graphene

More information: Giant Thermoelectric Effect from Transmission Supernodes. Justin Bergfield, Michelle Solis, and Charles Stafford. ACS Nano Sept. 2010.

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Pyle
2.5 / 5 (12) Sep 24, 2010
They've got to be kidding right? Hyperbole. From the article they are suggesting that several nanometers of their Benzene coating on an exhaust pipe is going to improve efficiencies of an engine by 25%. Get out of here.

This is truly a huge leap forward in applying quantum effects if it works, but gross exaggeration such as this is not helpful. I applaud the scientists at UA, but let's keep it realistic.
krundoloss
2.6 / 5 (8) Sep 24, 2010
Pyle, think about it now, Capturing all the waste heat from a vehicle. Say goodbye to AC, Radiator, Cooling system, brake heating, heck you could even coat the whole car with it to suck up all that heat generated by sunlight. You could boost the car's efficiency even higher than 25%. I have thought of this kind of technology alot, and this is a dream come true.
crhine
4 / 5 (9) Sep 24, 2010
Pyle, considering the average car is about 17% efficient, bumping that up to ~21% seems reasonable, which is a 25% increase

(or even if they're referring to that raw number increase to 25%, it also is pretty reasonable if it can even convert 50% of the heat produced by the car)
Yevgen
2.4 / 5 (7) Sep 24, 2010
What they fail to mention that there are plenty solid
state thermoelectric generators out there already.
They are using different effects, namely Seebeck effect,
but the basic idea is the same - once there is an energy difference due to temperature, you can harvest it as electricity.
These devices don't use QM effects and efficiency is
not great, but for that they are easy to make, while making a forest of vertically standing molecules might appear to be easy only to a theoretist who is making his experiment on a simulator.
Nothing wrong with doing that of cause. It might become practical some day even if it is not now.
El_Nose
1.3 / 5 (6) Sep 24, 2010
So in a few years your refridgerator will help power your house... win / win or the heat from processors will help provide energy for the system...

the article states that wherever a temperture difference exits power can be generated and the greater the difference the more power it generates -- using that logic -- could you use the temp difference of the outside in winter to heat you house... and by raising the temp of your house effectively increase the amount of power available for heating the house to an even higher temp -- smells like a perpetual engine which means an assumption I am using is wrong and I messed up a conservation of 'blah' law in my thinking...

but houshold/commercial building heating by itself would pay for this technology to be everywhere if it works the way i think it says
pratekya
3.4 / 5 (5) Sep 24, 2010
So if I understand this correctly, the electrons are actually canceled out? I thought there was a conservation of charge law going on for most interactions. What happens to the charge and mass of the electrons when they cancel out?
I understand thinking of them as waves helps, and I understand destructive interference, but still these electrons are also particles with mass and charge.
Trim
1 / 5 (2) Sep 24, 2010
Why not use a catalytic heater and a heat exchanger and you could have a very efficient electric car with only water and co2 as exhaust gases if you used something like propane as a fuel. Indeed you could generate your home power and heat water with it to cool the heat exchanger powered by main or tank gas, especially when there was no wind or sun.
Trim
2.5 / 5 (2) Sep 24, 2010
I suspect it would have a good synergy with this.

http://www.physor...201.html
Empyre
3 / 5 (2) Sep 24, 2010
Why not take this idea further, and use this instead of a turbine to convert energy from burning fuel at a power plant? It is bound to convert that heat energy more efficiently, and completely.
Caliban
1 / 5 (3) Sep 24, 2010
Gotta wonder about toxicity, though- given that this technology would be used in high heat and/or high vibration environments, one would expect breakdown of the coating over time, resulting in loss of efficiency and bits and pieces of benzene floating around. Benzene is some pretty nasty stuff.

eachus
4.8 / 5 (4) Sep 24, 2010
Is this as potentially revolutionary as it sounds? Yes. Is some of the hyperbole in the story, and the comments hot air? Sure.

I'm going to guess that a practical version of this will have molecules grown upward from a conducting electrode. Now cause the growth medium to solidify, or at least jell into an electrical insulator. Finally sputter metal on top to create the second electrode.

Now you have your miracle material, at a cost measured in dollars per square foot--once it can be produced in volume. Wrap the exhaust pipe to replace the alternator? Sure. That could be cost effective. The fact that it saves on gas or whatever is nice, but the payback is immediate in lowering the cost (and weight) of the car.

You could also design it into roofing tiles. They would cost more--and cost more to install. (You do NOT want a nail through one.)

And so on. In the real world you have to look at all costs when figuring if a technology will make it to market.
kuro
1.5 / 5 (2) Sep 24, 2010
Heh cool. Except for the part that we'll see this in reality only if someone re-packages it as "anti-entropic weapon" and sells it to the military.
xamien
4.3 / 5 (4) Sep 25, 2010
The foregoing comments (excepting the spammer) seem to go to extremes.

Pyle, considering the average car is about 17% efficient, bumping that up to ~21% seems reasonable, which is a 25% increase

(or even if they're referring to that raw number increase to 25%, it also is pretty reasonable if it can even convert 50% of the heat produced by the car)


This is the most reasonable statement I see here, and also the most realistic understanding of what the researchers at UA are doing. Let's cut the hyperbole and arguments about hyperbole, please.
Husky
4 / 5 (1) Sep 25, 2010
I can easily imagine an all graphene equivalent of this as a flat sheet with specially forked slit/grid structures cut out, this should have superior capacity as it can hold many more space charges/temperature/higher voltages
Husky
4.7 / 5 (3) Sep 25, 2010
theoratically with graphene only quantum walk grids you could transcode photons into phonons and back and modulate or transcode allmost Electromachnetic signal, heat to electricity --> electricity to sound --> sound to light etc etc, think of DSP on steroids, it should therefor be possible to make graphene grid only PLC/logic gates/memory
genastropsychicallst
1 / 5 (8) Sep 25, 2010
... D umbra squark arma graviton c 5 firmament geddon generation group selectron axion factor W ...
Quantum_Conundrum
3.5 / 5 (4) Sep 25, 2010
I see the trolls are out in force today.

This looks like a promising breakthrough in efficiency both for hybrid and pure electric.

It would also seem to replace the Alternator in conventional engines if you applied this to the exhaust and the radiator, and basicly just coat the whole engine with this material. then you could charge your battery and power all of your electronic components without the use of an Alternator. This would further increase power of the engine because you cut out a belt and pulley.
Empyre
4.7 / 5 (7) Sep 25, 2010
I guess I misunderstood earlier and thought this was big news because it was more efficient than anything we have now. I see now that the benefit is using energy that would otherwise be wasted.

Here's another idea for you guys to probably reject. How about using it as a cpu cooler in a computer? It would actively draw heat away from the cpu, but never below ambient temperature, thus avoiding deadly condensation on the electronics. The electricity generated could be used to power a fan, further cooling the system, or fed into a specially designed power supply unit, which would clean it up and use it.
xamien
4.5 / 5 (4) Sep 25, 2010
Empyre, that's definitely the whole point and the idea you suggest is probably preeminently on the minds of most of the computer geeks reading this article. :)
suman2010s
3 / 5 (2) Sep 26, 2010
Looks like a brilliant idea, on paper but then there is a lot of difference between theoretical and practical concepts.
I sincerely wish that this concept works and if does then it would revolutionize the thermodynamics and power generation spaces. All the best guys...!!
sender
3.3 / 5 (3) Sep 26, 2010
This shall move thermocouples to power advanced mm-wave beam accelerated solid state non-blinking optical propulsion thrusters in 21st century spacecrafts and exo-suits which have better radiation shielding allowing for solar expeditions.

just grand
BrianH
1 / 5 (2) Sep 26, 2010
The applications are almost beyond counting. Even cappy old thermal power plants -- no steam cycle, just convert the heat directly into electricity! Unfortunately, that could reduce their CO2 footprint, and reduce our contribution to ending the CO2 famine.

But power costs would drop drastically, enabling far more economic activity and general wealth creation.
Ronan
not rated yet Sep 27, 2010
the article states that wherever a temperture difference exits power can be generated and the greater the difference the more power it generates -- using that logic -- could you use the temp difference of the outside in winter to heat you house... and by raising the temp of your house effectively increase the amount of power available for heating the house to an even higher temp -- smells like a perpetual engine which means an assumption I am using is wrong and I messed up a conservation of 'blah' law in my thinking...


You could use the temperature difference between your house and the outside to generate energy, yes--but that energy would be generated by decreasing the difference in temperature between inside and outside (so, by cooling your house, basically). Trying to heat your house by refrigerating it won't work so well.
Ronan
5 / 5 (3) Sep 27, 2010
So if I understand this correctly, the electrons are actually canceled out? I thought there was a conservation of charge law going on for most interactions. What happens to the charge and mass of the electrons when they cancel out?
I understand thinking of them as waves helps, and I understand destructive interference, but still these electrons are also particles with mass and charge.

The waves referred to here are the electrons' probability densities; when they destructively interfere, it doesn't mean that the electrons have ceased to exist, it just means that the electrons have zero probability of existing at wherever the destructive interference is taking place. They still maintain a nonzero probability of existing elsewhere, so the conservation of energy/mass isn't violated. You get a charge build-up because, thanks to the interference, the electrons aren't "allowed" to move along the molecular wires, and more electrons coming up behind them are similarly blocked.
jscroft
1.7 / 5 (3) Sep 27, 2010
I wonder how much power we could generate if we painted Washington DC with this stuff?
Pyle
1 / 5 (2) Sep 27, 2010
Alright, back to reality. Coating a car with a material that can generate electricity from heat differentials to achieve a 25% efficiency increase is ridiculous given automobiles as they exist today. RIDICULOUS!

Using this technology to generate some electricity from the exhaust produced by a car is an interesting idea, but how do you maintain the air flow to keep the current inefficient process working while capturing the heat necessary for the new quantum effect driven process? There has to be a differential, so if everything is hot it doesn't work. Engine efficiency increases the larger the differential, which means flow. A nanometer coating on an exhaust pipe, or just about anywhere, isn't going to do what is necessary. New engine designs, new exhaust, new type of car. No painting benzene on stuff to get 25% more out of your gas guzzler. Hyperbole.
Pyle
2.5 / 5 (2) Sep 27, 2010
I do like the idea with the CPU and think that is a great potential application of this technology that is much closer to realization than the automobile application. The solar energy applications also seem like something that we are much more likely to be seeing should this technology prove viable.

Again, great research. Ease up on the outlandishness.
BrianH
1 / 5 (1) Sep 27, 2010
Good for the undergrad! But it's "lo and behold", not "low". ;)

If this could be used in power plants instead of boiling water, it will crash the price of energy.
Quantum_Conundrum
1.5 / 5 (2) Sep 28, 2010
BrianH:

It would never totally replace the boiling of water of the use of generators.

What it could do is capture more of the heat and convert it to electricity after the steam as passed the turbines.

As far as a house goes, it would make more sense to use this to COOL a house in the south during the summer, since presumably the colder the house becomes the more efficient the electricity production would be.
KomMaelstrom
3 / 5 (1) Sep 28, 2010
What, so Mister Stafford is the man that receives the credit for discovering the effect? Sounds like he's an idiot looking for credit. He even made such stupid associations such as the relationship between red and car on a red car are the same as a particle and a wave. No. It's that their concepts are fucked. A particle IS a wave, it's merely a perspective on it's properties and it's situation. I'm sorry, but red is not a car.

Anyway, the effect seems promising, however I'm not sure how difficult it is to produce. Possibly nanowires would provide a more practical solution to the problem of waste heat.
BrianH
not rated yet Sep 29, 2010
BrianH:

It would never totally replace the boiling of water of the use of generators.

What it could do is capture more of the heat and convert it to electricity after the steam as passed the turbines.

...

If the heat from steam can be captured, why bother going through the steam phase? The steam is heated by the reactor; if you can cool it directly with thermoelectrics, why not do so?
GregHight
5 / 5 (1) Sep 29, 2010
The most practical way to use this application would be to create a box of some sort that is packed with layers of the thermoelectric grids then divert heated gases or liquid (exhaust or engine coolant) through this and use it as a sort of heat exchanger. You could use a low tech system using circulating water through tubing on a roof then run it through the thermoelectric generator to generate electricity and also cool the surface or other source of unwanted heat.

It could also be adapted to keep solar cells cooler and extract more energy increasing it's conversion efficiency. I'd be interested to see how much heat can actually be removed and converted to electricity. I can think of so many applications and uses but trying to coat things like engines and exhaust systems sounds like a nightmare. I'd focus on low tech ways to concentrate the heat then run it through a thermoelectric heat exchanger.
lengould100
1 / 5 (1) Sep 30, 2010
Don't forget Carnot. The maximum portion of energy which can be extracted from a source of heat is (sourceT - sinkT)/sourceT (All in degrees K). I presume sinkT would typically be ambient temp, since it is implied that if eg. the car's exhaust pipe or radiator circuit was at ambient temp than no power would be generated.

For eg. an auto radiator rejecting perhaps 1/3 of the potential 300 kw in the fuel put into a car engine at 100 degC (373 degK) with a 25 degC (307 degK) ambient, or 100 kw, the most such a system could collect would be (373 - 307) / 307 * 100 kw = 17.7 kw At an optimistic real-world achievement of 1/2 of Carnot possible, that's 8.85 kw.

For the exhaust operating at perhaps 350 degC, the figure is a little better, 50.72 kw possible, 25.36 kw probable.

IF this system is do-able and affordable, and works very near to theorectical possiblity, then PERHAPS it will be very nice to have. But we've seen many similar and have none yet.
justinb
not rated yet Oct 06, 2010
Pyle - I suggest you read our paper and the associated references therein, some of which are experimental measurements, if you are interested.
Pyle
1 / 5 (1) Oct 06, 2010
Justin,
I commend you, Ms. (Dr?) Solis and Dr. Stafford on your work to find a practical application of quantum theory. I was able to find more detail on your work and I found it very interesting but beyond my technical expertise. While I don't doubt the efficiency figures you cite, I feel that there will be a significant time delay before we see this technology applied.
As such, I believe that promising 25% efficiency gains on internal combustion engines sends the wrong message about the timeliness and immediate applicability of this technology. Your findings show what great strides are possible when we start designing at the molecular/quantum level. Be sure that many of us will be eagerly awaiting future developments in this technology.

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