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'Thermoelectrics' Could One Day Power Cars
sciencehabit writes: "Fossil fuels power modern society by generating heat, but much of that heat is wasted. Researchers have tried to reclaim some of it with semiconductor devices called thermoelectrics, which convert the heat into power. But they remain too inefficient and expensive to be useful beyond a handful of niche applications. Now, scientists in Illinois report that they have used a cheap, well-known material to create the most heat-hungry thermoelectric so far (abstract). In the process, the researchers say, they learned valuable lessons that could push the materials to the efficiencies needed for widespread applications. If that happens, thermoelectrics could one day power cars and scavenge energy from myriad engines, boilers, and electrical plants."
Several vehicle manufacturers have been experimenting with supplemental power generation systems in their cars. BMW for instance has a steam turbine. Honda's doing thermal recovery more efficient than regenerative braking.
We better speed up this global warming thing so we can power our thermo cars!
That doesn't work. TEs aren't powered by heat, but by heat gradients. So if everything is uniformly heated by the same amount, there is no benefit.
Now, scientists in Illinois report that they have used a cheap, well-known material to create the most heat-hungry thermoelectric so far
Because it's soooooo hard to actually state what the well-known material is
Ultralow thermal conductivity and high thermoelectric figure of merit in SnSe crystals
Oh, I guess it's not hard at all. A salt made of Selenium and Tin.
I debunked this LAST time it was posted..
Look, these things are NOT going to get you thermodynamic efficiency gains on anything of value. Any system which is designed to be efficient now, will not benefit from this kind of heat to electricity device. Thermodynamic rules demand a maximum efficiency that is as good as you can do. Most industrial scale energy production is pretty darned good compared to the maximum possible. So you are NOT going to be able to just hook up these things and get electrical energy for *free* (even without the device costs). Any energy you manage to get, will be lost someplace else because you put these devices in the heat flow. Don't even bother trying this, it simply won't work. Don't let them fool you with all this "waste heat" garbage, at least until you understand the Thermodynamic laws that govern all this and can explain what a heat engine is.
As I concluded before, in situations where you have less than ideal conditions, like in cars with internal combustion engines, you MIGHT get a little bit of energy, but I ask you is it going to be worth it? Are you sure you are going get enough gain to make it worth the weight, cost and complexity? Where I'm not so sure that answer is a good one, I'm willing to entertain that it *might* be possible for internal combustion engines. Go ahead and work on that idea, but I'm fairly sure it's not going to work very well.
I'd also suggest that there are more efficient heat engines you might consider. These heat flow direct to electricity devices are horribly inefficient compared to the ideal.
"File to fit, pound to insert, paint to match" - Aircraft Maintenance 101
If the car is electric it could be powered by waste heat from industrial processes and primary power generation.
TEs are bound by the same Carnot efficiency limitations as any other heat engine. If you use low grade "waste heat" then you are going to get very little power.
E = (T2-T1) / T1
Everyone with an engineering degree knows this. Trying to extract much energy from low-grade heat at the output end of an engine is inefficient. This was figured out a long time ago. Here it is in The Manual of the Steam Engine. It's possible to increase steam engine efficiency by compounding, where the exhaust from each cylinder feeds a larger, lower pressure cylinder. This is cost-effective up to about 3 cylinders ("triple expansion"). Engines up to quintuple-expansion have been built, but the additional power from the last two cylinders in the chain isn't worth the trouble.