Ohio Researchers Advance Heat Reclamation Technologies

Downchuck writes "Researchers at Ohio State University claim to have synthesized a new material capable of delivering electricity directly from heat, at an efficiency far better than existing thermoelectric materials. Scott at ArsTechnica has an interesting take: 'Merge this with the new MIT solar dish and you're in business!'"

Comments

Yeah, frying ants with a parabolic is cool and all

[iminplaya]

But I like this better.

Finally!

[Anonymous Coward]

Finally, we have a truly renewable source of energy - we can just harness all the hot air coming from our politicians.

Technical point

[Bruce Perens]

It's not possible to make electricity directly from heat. It is possible to make it from a difference in heat between two points.

Re:Technical point

[ettlz]

Yes, on this site we obey the Laws of Thermodynamics!

Re:Technical point

[cnettel]

You make electricity directly from heat. You can't make electricity directly from temperature (or stored heat) though.

Re:Technical point

[Anonymous Coward]

It's not possible to make electricity directly from heat. It is possible to make it from a difference in heat between two points

heat != temperature

But you are right that you have to have a cold reservoir to get any work from the system. But heat in thermodynamics is not the same as temperature, and it generally denotes the amount of transfered thermal energy between two systems of differing temperature.

I'm assuming that the cold reservoir is the cooler temperature air surrounding the device.

Re:Technical point

[Anonymous Coward]

The other campaign may call it pandering, but I think the American people deserve a temporary holiday from the Laws of Thermodynamics.

Re:Technical point

[Doc Ruby]

But quadrupling them would. The old max zT these researchers were improving was about 0.87. They've now got it to about 1.5. And are targeting about 3.0 in their current research.

Freon refrigerators have a zT of about 3.0. Which makes these new materials look directly competitive with them for cooling when they reach that efficiency. Since zT 1 materials are about 10% efficient, zT 3 will be able to reclaim about 30% of waste heat. That would be about 20 points of the ~60% of gasoline energy wasted as heat in car engines. Since car engines are about 20% efficient now, that would mean doubling their fuel efficiency.

If these materials can be made, deployed, and recycled with close to (or less than) the energy inputs required now to make the car radiators/manifolds/exhaust systems they'd probably mostly replace, the benefits would be revolutionary.

Re:Technical point

[Doc Ruby]

The Technology Review article about the tech is more specific about the material's heat/electricity conversion efficiency. Evidently the current zT:0.87 material is about 6% efficient; the zT:1.5 material already achieved therefore is about 10% (about 10.3448276%) efficient. A zT:3.0 device is about 21% (about 20.6896552%) efficient.

10% of the 60% of gasoline's energy content wasted as heat is 6% of the gasoline's energy. If the car got the average 20% fuel efficiency, that extra 6 points would be 30% more than the original 20%. A zT:3.0/21% would be 12.6 points extra, or 63% more than 20% to 32.6%.

A 30MPG car today would get 39MPG tomorrow with the current version material. It would get 48.9MPG with the forecast zT:3 material.

What I'm really interested in seeing is how embedding the higher zT materials inside fuelcells boost their efficiency. Because fuelcells aren't heat engines, they're not limited to the Carnot Cycle's 40% max efficiency. They already get 50% efficiency or greater at "native" voltages (like 1.48V), where their max theoretical efficiency is 83%. But still, much of their 17%+ inefficiency is generating heat. So they can be even more efficient with heat reclamation, perhaps in practice actually approaching that 83% efficiency.

Re:For those who didn't RTFA:

[magus_melchior]

And since I can't make hyperlinks correctly on slashdot, I'll try again: thallium.

Nasty stuff, as its compounds are very easily absorbed through potassium uptake pathways in your body, but behave very, very differently from potassium. I seem to remember a chemist friend telling me that if you deal with thallium, you practically need an entirely separate lab for it.

Detailed Scientific Analysis Here

[Doc Ruby]

The article at the Green Car Congress site titled New Approach to Developing Thermoelectric Materials Doubles Efficiency" has a lot more scientific details than that article linked from the summary, especially on the actual formula that determines "zT", which is the thermoelectric conversion efficiency coefficient:

The dimensionless zT for thermoelectric materials is calculated by the formula zT= T*(S2)/), where S is the thermoelectric power or Seebeck coefficient of the TE material, and are the electrical and thermal conductivities, respectively, and T is the absolute temperature.

And also detailed nanomaterials engineering analysis of the quantum structure of the quantum chemistry's thermoelectric effects.

Re:Thallium

[value_added]

Thallium accumulates in your testicles. I remember hearing stories about labs handling thallium where only women were allowed.

Well, the article does explicitly state that "The material does all the work."

The comments attached to the fine article...

[Horar]

... contain a link to a possibly more useful article with some more comprehensible numbers:

http://www.technologyreview.com/Energy/21125/

e.g. The device could increase fuel efficiency of vehicles by approximately 10 percent.

Themoelectrics Already Pretty Good

[Doc Ruby]

Even though that article linked from the summary says that typical engines in cars get about 25% of the gasoline's energy content into car motion, it's actually about 20%. That's a lot of wasted energy: about 4:1 waste:use.

But lots of combined cycle plants (like CCGT gas turbines) reclaim a lot of their waste heat into more power. Taking a maximum mechanical power extraction of 60% of the gas' energy up to 85% by heating steam, which is an additional 25% of the original mechanical power.

CCGT reclamation tech is probably not practical for vehicles, so this new material is a welcome advance. Especially if the researchers get the zT from its new 1.5 high to its predicted 3.0 or so. But in fact DARPA has funded Trinh Vo at Lawrence Livermore National Labs to grow nanowires that already have a zT at 3.

More of that kind of material research is very welcome, because at zT 3, these materials can replace freon refrigerators with the same electrical efficiency. Since freon refrigerators require lots of energy to build, and then to recycle, replacing them with a simple material that can scale to any size (including very small, as in microelectronics), means a vast sector of modern industry, including transportation, could switch. If making the material is less energy intensive, and less reliant on a limited critical resource than the freon refrigerators or the CCGT reclamation systems, global energy efficiency could take a giant leap.

A leap that could be just around the corner, in Ohio.

Pity it sounds pretty poisonous

[D4C5CE]

thallium-doped lead telluride

An achievement made up of toxic elements, the first being rat poison, the last being the rarest there is. Chances are this won't be cheap to make nor to dispose of, and I wonder what hazards it would pose to the environment if released (vehicles do crash or get abandoned from time to time).