Arizona Technology and Innovation

Nov. 9, 2010

Transcript:

Ted Simons: A tremendous amount of heat is produced when you use your car. And it's not free. You pay for it at the pump. Now researchers are looking at a method to recapture wasted heat from any type of energy production and convert it to electricity using a quantum effect. Tonight we'll take a look at that research as we debut our new segment "Arizona Technology and Innovation". It's a multimedia effort that focuses on the people, ideas, businesses and technologies that are shaping Arizona's future. In these segments, you'll learn how Arizona is on the leading edge of high-tech innovation and how discoveries made today will impact lives for generations. I will talk to two University of Arizona scientists about their research. But first, Mike Sauceda tells us more about thermoelectricity.

Mike Sauceda: Whenever power is produced, much of it is wasted in the form of heat. Cars lose a lot of horsepower through engine and muffler heat. Solar panels are rendered less efficient because of waste heat. But scientists at the University of Arizona are working on ways to capture much of this heat making the production and use of energy more efficient. Thermo-electrical would use a quantum effect to recapture that heat and turn it into electricity with no moving parts. Right now the research mostly exists as a computer model but scientists are optimistic that the concept can be applied easily in the real world. Researchers take advantage of an effect called quantum interference. It's similar to the noise cancellation effect used on some headphones where two sound waves that are exact opposites cancel each other when they meet. Except instead of using sound waves, researchers use electrons which are conveyors of electricity. Those electrons even though composed of matter can exhibit wave-like properties. In the computer simulation, electricity is sent through a forest of polyphenyl ether molecules made of benzene rings. They act as molecular wires. The electrons falling down, split when they encounter a ring. The ring can be made so the electrons have to take a longer path on one side and that causes one side of the flow to arrive later than the other. When the two flows meet, they cancel each other out through quantum interference. More benzene rings means more electricity. A temperature difference is applied and that can float through the singular layer of molecules but the electricity cannot and it has greater voltage. A single layer of the molecules painted on metal electrodes would act as a thermo-electric device producing electricity.

Ted Simons: Here now to talk about his research into thermoelectricity is Charles Stafford, an associate professor of physics at the University of Arizona. Also joining me is Justin Bergfield, a doctoral candidate in the U of A's College of Optical Sciences. A doctoral candidate. I don't want to rush past that. That's a pretty big -- thank you for both joining us on "Horizon".

Charles Stafford and Justin Bergfield: Thank you.

Ted Simons: Capturing wasted heat, turning it into electricity. Is this a new idea?

Charles Stafford: Actually, no. It goes back quite some time. The problem is capturing it to make it useful.

Ted Simons: We had steam engine or something like that?

Charles Stafford: The steam engine is analogous to what we've come up with. Instead of steam, it's the electron waves themselves which are the medium. You heat up the electron waves and rather than do mechanical work, they do electrical work.

Ted Simons: Before getting into the nuts and bolts, this could have an impact on cars, power plants, factories. Tell us how.

Justin Bergfield: Basically there's waste heat from all sorts of factories. Like you said car exhaust, engine is typically warmer than the ambient air around it. The fact that you have a conversion and you take temperature and convert it to a voltage which can power any number of electrical devices you may be interested in powering.

Ted Simons: We have heat into voltage, voltage into power. We have the quantum thing out there. The minute people hear quantum, all of a sudden it's randomness. Talk to us about the quantum law that applies here and how it applies.

Charles Stafford: Okay. It's a tough one. It's a tough one to explain because it basically comes down to the fact that the electron can be a volt as a particle and a wave. As a wave it can interfere with itself. That interference affects the flow of charge and of heat differently and basically to get a thermo-electric voltage, you need to have a lot of heat to carry a per unit of charge. So essentially that's what is going on. Because of this quantum nature of the electronics, it's able to be a very efficient exchange of heat medium.

Ted Simons: You're talking about and correct me if I'm wrong, and benzene plays part of this as far as the conductor if you will. You're seeing what could be particles and/or waves going into a certain direction and boom, they collide and that's when things happen.

Justin Bergfield: In a sense, yeah. Matter, the things that we touch and the things we see are basically light and electrons, most of chemistry and all the things we're interested in. If you connect through a benzene ring and a so-called meta-configuration, you have two paths interfere and using the wave-like nature of the electrons that it gives a complete cancellation to the flow of charge. So if you were looking as an electron wave into this thing, it would basically reflect back. The interesting aspect is that heat is inherently incoherent. It has a disorder to it. It can't quite cancel completely. This gives a very efficient thermo-electric response.

Ted Simons: Take that thermo-electric response in what we've just heard. You both described, how did you get from that to this?

Charles Stafford: Well, it was quite -- it was serendipitous I would say. So Justin discovered it in this kind of meta-connected benzene ring you showed earlier. He found a very big voltage, about 20 times as big as anything that's been seen in these kind of junctions heretofore. Then we looked at if instead of one ring you had two rings. It went up to 300 volts per Kelvin. If we put in more rings, you could get bigger and bigger voltage. It became something that is technologically interesting.

Ted Simons: What we're looking at here -- what are we looking at here? Looks like you have a little bit of cancellation. What is happening here?

Justin Bergfield: The two big things on the left and right-hand sides are gold electrodes, for example. STM tips or something like that. It can be a broken fragment of wire. There's a biphenyl molecule in the center. It's a 3, 3 biphenyl junction, it's two of these meta-connected benzene rings. The electron wave if you consider coming from the left-hand side, sort of circles around and cancels out the bridge between the two. That in turn cancels I guess you could say, that's not entirely --

Ted Simons: Sure.

Justin Bergfield: But the point is the thermo-electric response, you increase -- a number of these rings increases, so you can have a scalable thermoelectric device which is a big advantage of this technology.

Ted Simons: How do you get more volts? Is it bigger rings? What?

Charles Stafford: Essentially making bigger rings will not increase the voltage. But putting more rings in series. Like making kind of a necklace with more and more rings, that makes the voltage go up, even more than in proportion to the number of rings.

Ted Simons: And the heat, the temperature variation makes a difference as well, correct?

Charles Stafford: Yeah, the more temperature variation you have, the more voltage you can.

Ted Simons: I think we've got it as far as the quantum aspect. Take us from that to, again, the concept of applying this on an everyday item, like a car.

Justin Bergfield: So we're interested in general and single molecule electronics. We're interested in basically when they connect to a single molecule, which is very hard to do. A fellow here at ASU is one of the leaders of it. So what we propose is basically you can deposit these as a mono layer or a layer of molecules where you've engineered the chemistry that one end bonds to one conducting plate and the other bonds to another one. I showed on the side of a factory a cartoon whereby I had one plate on the hot side of the exhaust fan or exhaust of a factory and the other on the air. So if there's, say, you know, 20 degrees Celsius temperature variation between those two, based on the thermo-electric response, you can generate a large voltage potentially.

Ted Simons: What kind of size are we talking about? If you're going to further it on the car, it has to be pretty small.

Charles Stafford: Well, the idea would be ideally with the correct chemistry you could just make like a polymer that could be painted on, literally coated on your surface, any metal surface and then you would just put another electrode on top of that and that would be your device.

Ted Simons: That wouldn't be much at all, would it?

Charles Stafford: It would be very thin, you're right. It would only be a few nanometers thick.

Ted Simons: How far have you gotten in the lab on this? What are you seeing?

Justin Bergfield: At the moment we're talking with various chemists and they say that mono layers of this type are, quote, easy to make. They assure us that it's doable and that this is mostly a conceptual breakthrough whereby in the lab engineering may have associated pitfalls but at least to their eye they see it being a fairly straightforward technology to test.

Ted Simons: How soon before we can see some maybe real world tests?

Charles Stafford: A matter of months I would say.

Ted Simons: Really?

Charles Stafford: Yeah.

Ted Simons: I know solar is a big deal in Arizona. A lot of folks are trying to make it a big deal. This could be a big deal regarding solar, could it not?

Charles Stafford: It could. The solar spectrum peaks in the near infrared. Infrared is what we call heat, right? So most of the light is not useful for photovoltaic conversion because it's not above the band gap of the semi-conduct silicon they're using. You could focus it with a mirror lens on to a little thermoelectric device and that would convert the heat directly into electricity. That part of the spectrum which is just wasted by normal photovoltaic.

Ted Simons: Are you sensing that as small and as portable as it might be right now, you could even make it smaller and better?

Justin Bergfield: Well, maybe. It's only a few nanometers --

Ted Simons: Can't get much smaller, can you?

Justin Bergfield: Can't get much smaller. They're solid state. They're small. A lot of cars have solid state heating or your wine cooler has a solid state cooler in it. This principle, this device works in both ways in terms of being able to refrigerate and being able to extract from a heat difference electricity.

Ted Simons: And the idea of no moving parts has to be huge, correct?

Charles Stafford: Right. Yes. But I mean the key I think is cost. Because, as you said, the thermo-electrics do exist. BMW and Volkswagen have demonstration projects where they've upped the overall efficiency by 5%. The problem is these semi conductor thermo-electrics are expensive and not efficient. Our materials on the other hand should be cheaper because they're like rubber-like polymers and they're much more efficient. That could be the key, you know, to going big with thermo-electrics.

Ted Simons: Getting much attention out of this?

Justin Bergfield: We've gotten a lot of calls. We've talked to a lot of potential investors. We're excited. It's exciting.

Ted Simons: I guess folks listen to this and say hey, something is going on.

Charles Stafford: Yeah. Some forward thinking venture capitalists and companies are interested in pursuing this further.

Ted Simons: Always nice to slip in quantum physics on "Horizon". Thank you for joining us.