Ohio Researchers Advance Heat Reclamation Technologies 124
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!'"
Yeah, frying ants with a parabolic is cool and all (Score:5, Interesting)
But I like this [enviromission.com.au] better.
Hot technology (Score:3, Interesting)
But there are a lot of areas where heat is produced, and some of this could be used to get extra electricity.
Maybe the most important point, at what cost? how rare/expensive is that new material? If is very, maybe the main use would be not for our normal lifes, but maybe for i.e. space probes.
Geothermal plug in (Score:3, Interesting)
Thallium (Score:3, Interesting)
Thallium accumulates in your testicles. I remember hearing stories about labs handling thallium where only women were allowed.
Themoelectrics Already Pretty Good (Score:5, Interesting)
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% [wikipedia.org]. That's a lot of wasted energy: about 4:1 waste:use.
But lots of combined cycle plants [wikipedia.org] (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 [llnl.gov].
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.
Re:For those who didn't RTFA: (Score:3, Interesting)
It's doped with thallium, that means that the thallium is imbedded in the metal alloy. I don't think it's going anywhere.
Re:What is the %Efficiency of a 1.5 zT? (Score:3, Interesting)
zT doesn't tell you the efficiency because that would depend on the delta T (next para), but it is roughly proportional to it for given operating conditions. zT = 1 materials have efficiency maybe around 5% under best conditions, for zt = 3 you might be around 20%. Notice that if you know S and delta T you know the voltage: you can do some simple circuit calcs with a matched impedance and get the power it will generate. Compare that to the heat energy you get from the delta T and the thermal conductivity and you can get an efficiency, but instead of that lets just throw out some round numbers.
Remember efficiency depends on the delta T due to the 2nd law of thermodyamics. The smaller delta T is the lower the max theoretical efficiency is. If the engine exhaust is at lets say 500F the max efficiency any device could get would be 1 - (492 + 72)/(492 + 500) = 43%. So that would be 78kW of your 180kW for a thermodynamically perfect device.
So if you can get maybe 20% out of thermoelectrics under the best conditions, the low-temp engine exhaust scenario would probably mean you could get at best 10%. So 20kW or so I'd guess. Once you design an actual system it would probably be more like 5 or 10kW.
Re:Technical point (Score:5, Interesting)
The Technology Review [technologyreview.com] 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:Thallium (Score:3, Interesting)
"I remember hearing stories about labs handling thallium where only women were allowed."
True. While I was at the U of I my chemistry professor was trying to stick thallium atoms to a cyclopentadiene molecules for some odd reason. The students working on it were all girls.