'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."

Comments

power cars? technically no

[noh8rz10]

technically, you would still need an energy source (gasoline, natural gas, batteries) to power the cars. thermo electrics could make it more efficient by recycling waste heat. but the thermoelectrics themselves would not power the cars.

Re:power cars? technically no

[i kan reed]

Fuel provides energy. Power comes from the conversion rate of the engine. You "power" things with an engine, but the net energy comes from fuel. Some engines can handle multiple fuel types, e.g.

Re:power cars? technically no

[ShanghaiBill]

thermo electrics could make it more efficient by recycling waste heat. but the thermoelectrics themselves would not power the cars.

If they are sufficiently efficient, they could power a car directly. An internal combustion engine is typically only about 15-20% efficient, so the bar is not too high. Using thermoelectrics directly could have several advantages: being solid state, they would be reliable and require little or no maintenance; and since the fuel is just used to create heat, it could use cheaper grades of fuel.

Re:power cars? technically no

[noh8rz10]

ok but then the car is still powered by fuel. in your scenario you would still need an external combustion engine to produce heat.

Re:power cars? technically no

[stewsters]

Or a RTG

Re:power cars? technically no

[Anonymous Coward]

ok but then the car is still solar powered. in your scenario you would still need an external sun to grow the plants that fed the dinosaurs that died and turned into oil that was refined into gasoline.

Re:power cars? technically no

[fuzzyfuzzyfungus]

My (admittedly pretty hazy at this point) memory of heat engines is that their theoretical peak efficiency depends on the thermal delta they manage to achieve. Exactly the same resource that thermoelectric materials scavenge (albeit at miserable efficiency) into electricity.

Anybody who actually has some grasp of the matter want to chime in on where and why you would use thermoelectrics (and how efficient they would have to be) rather than simple insulation or one of the various waste-heat-recovery systems that transfer some amount of the heat remaing in outgoing exhaust gases into incoming working fluids?

Is the thermoelectric advantage purely that, assuming material reliability is OK, they are a 100% solid state, trivial to scale from 'handle with tweezers and magnification' to 'pretty large', and their output is easy to transfer and useful for all kinds of things after just a little DC-DC cleanup, or are there actually situations where they might be absolutely more efficient than insulation and heat recovery, rather than just easier to tack in almost anywhere in a design that you have a few extra cubic centimeters and expect a temperature difference?

Re:power cars? technically no

[noh8rz10]

point granted, the "powered by" slope is a slippery one. but saying the car is powered by thermoelectrics is like saying it's powered by suspensions.

Re:power cars? technically no

[jellomizer]

So say we can double that. That makes the fuel 40% efficient as we use some of the heat towards efficiency. That will double the gas mileage. However if you need a smaller engine, then it will be producing less heat. That is good if it is 1 for 1. However if their needs to be a particular heat starting limit then it may cause an issue. Unless you go with a bigger car.

The idea as the engine gets more efficient people buy bigger cars, is economically sound and proven. A large truck today can do about the same as a station wagon 30 years ago. But what happened is more people started buying trucks.

Re:power cars? technically no

[Anonymous Coward]

The lack of efficiency is precisely why NASA is looking into replacing thermoelectric generators with linear Stirling engines.

Re:power cars? technically no

[Anonymous Coward]

Thanks for telling us what the synopsis provided by Slashdot just told us.

Re:power cars? technically no

[gman003]

It is completely valid to say "a car is powered by an engine". The engine is powered by fuel, but the car's power comes from the engine. Replacing the reciprocating engine with a thermoelectric engine allows for the headline to, in fact, be an accurate statement.

Re:power cars? technically no

[noh8rz10]

if you have a "thermoelectric engine" then what is producing the heat to power the thermoelectrics?

Re:power cars? technically no

[Newander]

If the car is electric it could be powered by waste heat from industrial processes and primary power generation.

Re:power cars? technically no

[LifesABeach]

Maybe Solar Heat?

Re:power cars? technically no

[ShanghaiBill]

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.

Re:power cars? technically no

[ShanghaiBill]

if you have a "thermoelectric engine" then what is producing the heat to power the thermoelectrics?

A flame.

Re:power cars? technically no

[viperidaenz]

If the thermoelectrics are significantly more efficient that than internal combustion engine, removing it completely would save a lot of weight and may result in a more efficient system.

Re:power cars? technically no

[Guspaz]

It's not as silly as you might think. I believe you get roughly 500W of heat per kilo of plutonium-238. A Tesla Model S driving at normal speeds consumes something like 15KW. If you could get 50% efficiency for your thermoelectrics, you could build an RTG-powered model S with 60 kilos of plutonium. You'd need capacitors for surge demand, obviously.

Of course, this would be completely insane, but I don't see why it's not theoretically possible, since the battery pack on the car that you'd be replacing already weighs something like 600 kilos.

Then again, with sufficiently efficient thermoelectrics, you might see the military using RTGs.

Re:power cars? technically no

[Em Adespoton]

The power plant -- just like in Diesel Electric trains; you have the electric engines that power the train and the power plant that powers the engines. Diesel fuel powers the power plant, and it in turn was powered by solar energy. The sun is powered by hydrogen fusion reactions; the hydrogen fuel was provided by gravitational attraction, which was powered by time and space.

I'll leave it up to the reader to determine who/what powered time and space.

Re:power cars? technically no

[Anonymous Coward]

If I might nitpick, the ICE's 15-20% efficiency figure is the gas tank-to-wheels efficiency which includes substantial losses in the transmission and differentials. The ICE itself might be 30+% efficient. In diesel-electric applications, where the ICE is optimized to run at a single speed, efficiency can be even higher. Diesel-electric plus batteries for peaking (Even a Lincoln Navigator uses less than 20hp except when accelerating) with an all-electric drivetrain seems like an excellent immediate-term way to reduce fuel consumption; I wish it was more widely available.

As far as using cheaper fuel, the whole reason we use more expensive grades now is to reduce pollution. Remember back in the early 2000s when gas was reaching obscene new heights like $2.50 a gallon (*snert*), but diesel was like $1.50, then all of a sudden the price of diesel was >= gas? That's the price of desulfuring the diesel, because sulfur oxides are bad to breathe and are the main contributor to acid rain (sulfur trioxide + water = instant sulfuric acid).

Re:power cars? technically no

[noh8rz10]

what are you burning to produce a flame?

Re:power cars? technically no

[ShanghaiBill]

There are several problems with your scenario:
1. Current TEs are no where close to 50% efficient. More like about 5%.
2. Pu238 is available in very limited quantities from reactor fuel reprocessing
3. You can't "turn-off" an RTG. They have to run continuously.

Re:power cars? technically no

[Anonymous Coward]

Ecat

Re:power cars? technically no

[ShieldW0lf]

point granted, the "powered by" slope is a slippery one. but saying the car is powered by thermoelectrics is like saying it's powered by suspensions.

If it was pointed out to you that thermoelectrics operate anywhere there is a heat differential, and that you could technically "fuel" your car by pouring liquid nitrogen into the tank and have the thermoelectrics exploit the heat differential between the liquid nitrogen and the ambient temperature to generate work over time, aka power, would that be enough for you to concede that thermoelectrics are indeed what is generating the power?

Re:power cars? technically no

[sexconker]

Fuel. You've been bitching about the use of the word "power" when you're the one who's using it wrong. The word you want is fuel.

Thermoelectrics generate power in the presence of heat.
Internal combustion engines deliver power when shit explodes inside them.

Gasoline is a fuel, not a power source.

Re:power cars? technically no

[ShieldW0lf]

Fuel. You've been bitching about the use of the word "power" when you're the one who's using it wrong. The word you want is fuel.

Thermoelectrics generate power in the presence of heat.
Internal combustion engines deliver power when shit explodes inside them.

Gasoline is a fuel, not a power source.

If you built a car engine that delivered power by causing fuel to explode, you'd change the world. Car engines work through deflagration, not detonation. Detonation releases way, way more power. It's hoped that it will be the replacement for scramjet engines... envision a jet being driven by a series of explosions. No one has admitted to successfully making one, though. I've spent years doodling different ideas about how you might make one if we had the materials necessary, but it's like building a space elevator... fun to think about, but you'd need materials far stronger than anything we have available.

Car engines run on boring old combustion. The difference in scale between combustion and detonation is not dissimilar to the difference between a compost heap and a bonfire.

Re:power cars? technically no

[Guspaz]

1. I realize that they're currently at 5%, the whole point of my scenario was examining what sort of changes a large increase in efficiency would produce... that's the whole point of the article, after all. Efficiency would need to be somewhere around 50% to justify replacing ICEs with thermoelectric engines. Is that possible? I've got no idea, TFA gives zero layman-friendly information about what sort of efficiency improvements are foreseen.

2. Supply isn't as big a problem as the incredible safety issues. I acknowledge in my post that the idea is totally insane, which is why I doubt that, even with a big improvement in efficiency, you'd probably never see RTGs used outside of military applications.

3. That's not necessarily a problem. They conveniently provide power that can be used for active cooling. Cooling them in a vacuum is an issue (hence the giant heat dissipation fins), cooling them in an atmosphere isn't as much of an issue.

I suspect that sufficiently efficient thermoelectrics might find their way into military UAVs, which could remain airborn for extended periods of time, for example. Or as an alternative to shipping diesel to remote outposts (although they're currently looking into robotic trucks to solve that problem).

Re:power cars? technically no

[Dare nMc]

> insulation or one of the various waste-heat-recovery systems that transfer some amount of the heat remaing in outgoing exhaust gases into incoming working fluids?

Several reasons this isn't done in the engine intake. The main power conversion in a ICE is through the thermal expansion of the gasses trapped in the cylinder, so heating it before the intake valve is closed only reduces the density of the air taken into the cylinder (PV=nRT so at the same Pressure and volume, the higher the temperature, the fewer molecules, less O2 available to burn.) Once the air is trapped in the cylinder all heat added will then be converted, so a cold intake, then a hot block helps contribute to efficiency. But then metals have limitations on the allowable temperatures (for at least the last 40 years Ceramic engines have been on the verge of a breakthrough making higher temp more efficient engines a reality, maybe next year.) Also combustion properties of carbon fuels create emissions problems when combustion occurs at too high of temperatures.
Power stations will harness the waste heat from Ng Generators, and pump that into a sterling engine, then take that waste heat into another conversion, then take that waste heat as warm water for buildings, etc. But that takes too much space, weight, and cost (I assume) to be put into a mobile vehicle (other than used as a heater in the winter.) Although I would hope Cruise ships, etc would utilize this waste heat as well.

Re:power cars? technically no

[tragedy]

1. Current TEs are no where close to 50% efficient. More like about 5%.

The article was about new, higher-efficiency materials. Still not high enough, and not near 50% efficiency, but certainly getting up there. Good enough so that, if you could get hold of the material, you could at least use it to charge your electric cars batteries currently, even if you couldn't power the car directly. Of course, at present, you'd be better off with a Stirling engine.

3. You can't "turn-off" an RTG. They have to run continuously.

Presumably, you could plug them into the power grid in most places you park them

Re:power cars? technically no

[sgt scrub]

Is an exothermic reactor considered internal combustion?

Re:power cars? technically no

[tragedy]

2. Supply isn't as big a problem as the incredible safety issues. I acknowledge in my post that the idea is totally insane, which is why I doubt that, even with a big improvement in efficiency, you'd probably never see RTGs used outside of military applications.

The safety issues aren't really that bad. You could put 60 kilos inside a casing that would easily block the radiation down to negligible levels and would be effectively indestructable in the worst conceivable accident. Worries about "dirty bombs" are ridiculous considering the large array of easily available substances that would be much more dangerous (not very) in such a bomb. As for a nuclear weapon, I'm not exactly sure how fissionable it is, but I do know that you would need a massively powerful nuclear weapon in the first place in order to actually induce fission in it, so it's not dangerous in that respect either.

So, right now, the supply probably is the biggest problem. At the rate the US is currently producing it, it would take 40 years to get enough for one car. Not that the rate of production couldn't be ramped up considerably, but it would still be so expensive it would only be useful for powering things in space or at the bottom of the ocean, or deep under the earth, etc. Places where power is otherwise impossible or incredibly expensive to obtain.

Re:power cars? technically no

[tragedy]

A detonation doesn't neccessarily release more power than a deflagration. That's apples to oranges. It's more a matter of intensity. For example, ANFO detonates, and has a specific energy of something like 3.7 MJ/kg whereas a gasoline/oxygen mixture in an engine typically deflagrates (although it can also detonate under the right conditions, which isn't good for the engine, as you point out) and has a specific energey of something like 9.7 MJ/kg (counting the gasoline plus the oxygen needed for combustion). Clearly averaged over time you can get more power out of an equivalent mass of gasoline/oxygen than from ANFO. Although, if you slice time thinly enough you can say that you get more instantaneous power out of the ANFO because you can get all of the power out of it faster than you can from deflagrating the gasoline/oxygen mixture.

Re:power cars? technically no

[dbIII]

I suppose so but that sounds very impractical since a bunch of candles would give you a larger heat difference. However I don't think many would call it a thermoelectric car just as a diesel-electric train is not called electric and a Prius is not called electric. It's probably best to accept that some people won't accept your proposed terminology and move on to discuss more than just semantics.

Re:power cars? technically no

[dbIII]

Am I missing something here or are you ignoring how diesel engines work? To me at least it looks like a series of small explosions.

Re:power cars? technically no

[confused one]

In your 60600 analysis you're forgetting the shielding and cooling requirements.

Re:power cars? technically no

[confused one]

damn /. parser. What I meant is 60 less than 600 (parser stripped the symbol)

Re:power cars? technically no

[newcastlejon]

Probably not. Internal combustion only means that the combustion occurs inside the engine. Contrast this to a classic example of external combustion: a steam engine, where the fuel is burnt well away from where the work is produced. Jet engines are internal combustion; most stirlings are external.

One might have a good case for arguing that thermoelectric engines are neither IC nor EC, since it needn't be combustion that provides the heat.

Re:power cars? technically no

[newcastlejon]

Anybody who actually has some grasp of the matter want to chime in on where and why you would use thermoelectrics (and how efficient they would have to be) rather than simple insulation or one of the various waste-heat-recovery systems that transfer some amount of the heat remaing in outgoing exhaust gases into incoming working fluids?

In IC engines you want the intake air to be cold so the density is higher (more oxygen); you may have noticed that cars with turbo charges often have something called an intercooler for this reason (compressing the intake air heats it). If you're going to scavenge anything from the exhaust gases it will be low-grade heat (delta-T is smaller, moreso with an efficient engine). Using heat from exhaust to pre-heat the intake is more commonly done with gas or steam turbines, where you want to reduce the amount of heat you need to put into the working fluid at the "cold" side.

I expect that the reason thermoelectrics haven't seen much use in cars is because the benefit you get from using a low efficiency method with a low delta-T just doesn't justify the expense of adding them. I wouldn't be at all surprised if one could gain more by attaching a generator to a turbocharger.

In fairness though, TEs are good if you want something low-powered and simple, but it's not that unusual for a diesel engine to last longer than the car it's put into, so the issue of reliability - one of solid state's big plus points - is rendered moot to an extent. For my own two penneth worth, if they're going to use TE devices to provide power for accessories (you'd never get enough to actually "power" a car without massive efficiency improvements - stupid title) you might as well use the very efficient alternator* you already have attached to the engine.

*Essentially an AC generator with some rectifiers attached. You can get upwards of 75 amps @ 12V if you really want to.

Re:power cars? technically no

[MachineShedFred]

you might see the military using RTGs.

Yeah, I can't wait to have explosive ordinance being flung at vehicles powered by a giant box of ionizing radiation. Great idea.

Re:power cars? technically no

[MachineShedFred]

When you plug in a microwave oven, do you say that it's powered by the wall socket, or that it's powered by coal / methane / uranium / solar / hydroelectric / wind / geothermal?

Because if you say the latter, you sound like an idiot. And, by the way, that's the exact semantical argument you're making here.

Re:power cars? technically no

[MachineShedFred]

I wish I hadn't already posted, or I'd be giving mod points just for the image that went through my mind of a vehicle that used ANFO as fuel...

Re:power cars? technically no

[ShieldW0lf]

It's probably best to accept that some people won't accept your proposed terminology and move on to discuss more than just semantics.

That's why I posted...

Re:power cars? technically no

[ShieldW0lf]

Am I missing something here or are you ignoring how diesel engines work? To me at least it looks like a series of small explosions.

You're missing something. Diesel engines are internal combustion engines.

Re:power cars? technically no

[Anonymous Coward]

Diesels are compression ignition and work at higher pressures, but still don't have detonation of the fuel/air mix.

Re:power cars? technically no

[noh8rz10]

let's agree to disagree.

Re:power cars? technically no

[Newander]

Sure, but we can sum the very little power from many sources.

Re:power cars? technically no

[Guspaz]

This is different to throwing explosive ordinance at current vehicles powered by nuclear reactors how?

Re:power cars? technically no

[Guspaz]

The Tesla car already has a bunch of shielding (both as a casing and to protect against impact damage) and cooling (active water cooling, specifically). Considering that most RTGs are designed to operate in a vacuum (where you have no medium to carry away heat) in zero gravity (where convection doesn't work), I have no idea what sort of cooling and shielding you'd require for terrestrial RTGs.

Re:power cars? technically no

[MachineShedFred]

Those are above several thousand feet of water, usually hundreds of miles away from any population. If they get hit, they are contained by the ocean they just sank into.

A land vehicle powered by an RTG has an incredibly higher chance of contaminating a piece of land that someone cares about, or having a fire put radioactive particles into the air that someone might be breathing.

Re:power cars? technically no

[sexconker]

Fuel. You've been bitching about the use of the word "power" when you're the one who's using it wrong. The word you want is fuel.

Thermoelectrics generate power in the presence of heat.
Internal combustion engines deliver power when shit explodes inside them.

Gasoline is a fuel, not a power source.

If you built a car engine that delivered power by causing fuel to explode, you'd change the world. Car engines work through deflagration, not detonation. Detonation releases way, way more power. It's hoped that it will be the replacement for scramjet engines... envision a jet being driven by a series of explosions. No one has admitted to successfully making one, though. I've spent years doodling different ideas about how you might make one if we had the materials necessary, but it's like building a space elevator... fun to think about, but you'd need materials far stronger than anything we have available.

Car engines run on boring old combustion. The difference in scale between combustion and detonation is not dissimilar to the difference between a compost heap and a bonfire.

An explosion is anything that involves an outward motion and accompanying noise. It comes from the Latin explodere.
You can try to split hairs about burning, exploding, and whatever the fuck else you want, but ICEs run on exploding fuel. The expansion from the explosion is literally what drives them.
You would have had a better chance if you had tried to correct my usage of the word "shit".

Re:power cars? technically no

[strikethree]

Well, the Bugatti Veyron's engine generates 3 thousand horsepower. It can deliver 1 thousand horsepower to the wheels as kinetic force. That leaves 2 thousand horsepower on the table as wasted heat. If you were able to convert 10% of that wasted heat into kinetic force, that would be an extra 200 horsepower. That would be 20% more kinetic force applied to the wheels at no cost (energy wise).

Take it the other way and you get 20% better gas mileage. Still not shabby. Personally, I would go for more horsepower. :)

Hotter Earth

[neonv]

We better speed up this global warming thing so we can power our thermo cars!

Re:Hotter Earth

[ShanghaiBill]

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.

Re:Hotter Earth

[MozeeToby]

So... sink a steel pipe half a mile into the ground, it isn't that hard to create a heat gradient. That's of course, if it's possible to hit anywhere near decent efficiencies with standard materials, which is something I'll have to see in production before I fully believe.

Re:Hotter Earth

[Anonymous Coward]

Global warming + AC = free energy*

Re:Hotter Earth

[fuzzyfuzzyfungus]

Well, you could build a thermoelectric shell around the entire earth... Of course, if you can do that, 'stop global warming' is probably something you did in high school as a busy-work lab project at your school for particularly gifted hypersentient disembodied intelligences.

Re:Hotter Earth

[ShanghaiBill]

So... sink a steel pipe half a mile into the ground, it isn't that hard to create a heat gradient.

That would give you enough of a gradient to generate a micro-watt from a ton of TEs. In a perfect ideal TE, the efficiency is (1 - Th/Tc) where Th= Hot side in Kelvins, Tc = Cold side in Kelvins. Existing TEs are no where close to ideal, and the earth's heat gradient is about 0.025K/meter. A negligible amount of heat would flow through the TE, and far less than 1% of that would be converted to electricity.

Re:Hotter Earth

[Anonymous Coward]

I hope you are not talking about the kind of cars in Fallout 3.

Re:Hotter Earth

[ceoyoyo]

Why yes, I have been to Iceland.

Re:Hotter Earth

[Immerman]

Good luck with that. Human energy production is directly a miniscule factor in global warming - it's the CO2 byproducts that's the problem. In the 90+ years it takes for a unit of CO2 to be removed from the atmosphere it will capture roughly 1,000,000x as much solar thermal energy as was produced by the burning of fuel that created it. If we generated 1000x as much heat directly, but without producing the CO2, then global warming would be a non-issue.

Re:Hotter Earth

[StripedCow]

The problem with that is that it will cool down the inside of the Earth.
You can have a look at the movie "The Core" to see what will happen then...

Re:Hotter Earth

[BlackPignouf]

It's not that there's no benefit : it's a net loss. Any heat engine works better between 300K and 400K than between 400K and 500K, even though the temperature difference between two states is the same.
Pedantic remarks : There's no such thing as "heat gradient". You probably meant "temperature gradient". And thermoelectrics generators really are powered by heat.

Re:Hotter Earth

[MachineShedFred]

Because clearly 'The Core' is scientifically accurate in every way!

New in the US, not elsewhere

[Anonymous Coward]

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.

Ah, the clickbait

[Anonymous Coward]

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.

Re:Ah, the clickbait

[rogoshen1]

"Illinois scientist uses this one weird trick to generate free electricity from waste heat; oil companies hate him"

That's about what that sentence sounded like to me =/

Re:Ah, the clickbait

[K. S. Kyosuke]

A salt made of Selenium and Tin.

Apparently, the author is a lunatic from some tinpot university.

Re:Ah, the clickbait

[Anonymous Coward]

A "salt"? High school chemistry a bit far in the past, eh?

Re:Ah, the clickbait

[ceoyoyo]

It is hard when your job as a "submitter" consists of copying and pasting the first paragraph of the article. At least they usually remember to put quotes around it.

Re:Ah, the clickbait

[metaforest]

Apparently, the author is a lunatic from some tin-selenide-pot university.

FTFY

Re:Ah, the clickbait

[Anonymous Coward]

Whoosh...

not before i get my flying car!

[turkeydance]

...from my cold, dead hands...

This is amazing

[Anonymous Coward]

We just discovered on slashdot the other day that transistors, and therefore ICs, are actually thermoelectric devices that use heat to modulate conductivity. Will this mean we will see solid-state cars in the future?

Oh boy is this for the wrong crowd?

[50000BTU_barbecue]

You expect slashdotters to generate heat... on a mattress?

Re:Oh boy is this for the wrong crowd?

[PIBM]

I guess they could use your BBQ, in some ways ?

Re:Oh boy is this for the wrong crowd?

[Anonymous Coward]

No I do not, because it is more efficient to do it while standing.

Re:Oh boy is this for the wrong crowd?

[Immerman]

Oddly enough that is exactly the position portrayed in the article - on a mattress. Without spilling your wine. Which is also on the mattress.

Not so fast, Thermodynamic laws are pesky things

[bobbied]

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.

why cars as the first application

[u19925]

the first application of such devices would be more like a solar cell, power plant, backup generator etc. Putting a new device in car can take decades, but putting in these can be done much more quickly as the number of approvals needed is far few. Whenever, someone uses "car" where it is not justified, I know the innovation is most likely worthless showoff or it is decades away from practical use. Yes, one day all cars will run on fusion power. Thanks.

Re:why cars as the first application

[Anonymous Coward]

This is slashdot. We like cars. Maybe this will make them fly.
Nobody likes solar panels. Are you trolling? Yes that's it, you're trolling.
When you troll, usually it's in a boat. But for a full blown, drive by shooting you need a car. And a gun. But let's not get those folks involved.
If people start arguing about guns, i'll never get my flying car.

Re:why cars as the first application

[Anonymous Coward]

Because it's the USA, apparently. According to this, rather comical, list, everything being about cars is #6.

Re:Not so fast, Thermodynamic laws are pesky thing

[sconeu]

Lisa, in this house, we obey the LAWS OF THERMODYNAMICS!!!!

better peltiere devices

[Anonymous Coward]

I think this would be more likely to be quickly seen in Peltier devices... CPU heatsinks, car airconditioners.
Seeing as bismuth telluride has a ZT of 1.4, that's a 185% improvement of over common implementations today.

Hybrid Engine That Doesn't Power The Car?

[Anonymous Coward]

From TFA:

If anyone succeeds in producing a high-ZT material, Heremans says, it could lead to new, cheaper hybrid car engines in which the internal combustion engine doesn’t power the car, but rather generates heat that thermoelectric devices convert into electricity to power an electric motor.

This doesn't make sense to me. If the ICE isn't going to power the car, why not skip the engine and just burn the fuel to create heat, then thermoelectrics to turn heat into electricity?

Nasa RTGs would get the first benefit

[Anonymous Coward]

Any small improvement in efficiency would be best used in current RTG applications where the thermo couples are only about 30%. A 1KW heat source would produce an extra Watt for every percentage point increase.

Re:Not so fast, Thermodynamic laws are pesky thing

[Anonymous Coward]

Nuclear power plants are very efficient, yet they still use cooling towers and still run millions of gallons of heated water through cooling ponds. This technology is about capturing waste heat, which is the product of a process which has already obeyed all the rules of thermodynamics.

Eh.

[Ober66]

A high FoM on this compound but take that with salt. Thermoelectrics still have a long way to go and there are plenty of groups, called ZT hunters, looking for something that could be useful. The best TE, including the reported values here, are still not what we would consider efficient. Also, there are many ways to....'influence' the ZT for best results. Good for them; it's always nice to nab a Nature paper, but dont expect to see this impact any commerce. Unless you have a lot of TE micro-fridges in your car.

Who shot Mr Burns?

[Thud457]

you guys just really don't get it, do you?

Global warming is a non-issue. Elon Musk is going to put up a orbital sunshade and hold the world ransom to turn the lights back on.
And there's NOTHING you can do to stop him.

Re:Who shot Mr Burns?

[MachineShedFred]

Didn't we see a Bond movie about that? Or maybe it was the opposite of that, where it focused the sun into a ORBITING SOLAR DEATH RAY.

Re:Who shot Mr Burns?

[Bob the Super Hamste]

I thought it was a Simpsons season finally cliffhanger.

Cheap Solar Power

[nwaack]

Why not use this in place of expensive solar panels? Sun + focusing device + black metal + thermoelectric = cheap electricity.

Re:Cheap Solar Power

[dbIII]

Because the photoelectric effect moves a lot of electrons around while the thermoelectric effect doesn't move as many around for the same input from sunlight. The very expensive type of photovoltaic cells are used with lenses in some applications.

Re:Not so fast, Thermodynamic laws are pesky thing

[rasmusbr]

The one application that I've heard about that sounds semi-plausible is sandwiching something like this between a solar cell and a liquid cooler. The difference in temperature between the PV cell and the cooler might be enough to yield meaningful amounts power and the waste heat that the cooling system captures could be used for heating.

Piezoelectric cars?

[Anonymous Coward]

Given the bouncing fat asses in modern cars, perhaps their kinetic energy could be converted into electricity by piezoelectric components.

I for one welcome our Steam Overlords

[WillAffleckUW]

Oh, wait, isn't the energy density and storage ratio far lower than compressed air?

Re:Not so fast, Thermodynamic laws are pesky thing

[Anonymous Coward]

Many systems currently designed to be as efficient as possible are still short of the maximum efficiency allowed under thermodynamics. How to best improve that efficiency, whether refinements of the original technology or using a mixture of techniques can be quite subtle and depend heavily on what situation and purpose, which is a long way from something being a matter of being debunked.

E = (T2-T1) / T1

[Animats]

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.

Re:E = (T2-T1) / T1

[Anonymous Coward]

I don't disagree with your larger point, but technically speaking, getting anything out of waste cannot be called "inefficient". In this case, it simply does not add much to the total efficiency of the system.

Re:E = (T2-T1) / T1

[Herder Of Code]

Well, steam engines were *mostly* immobile and powering crap like pumps or press so yes it would not be less efficient. However in the case of a steam carriage, sorry I mean a car, the additional weight might actually make it *less* efficient.

Re:E = (T2-T1) / T1

[joe_frisch]

In mobile systems (cars, planes, etc), the extra hardware to extract energy from the waste heat adds weight and can reduce the overall efficiency of the vehicle. In fixed power-plant type applications they already extract energy down to pretty low discharge temperatures.

This idea has been around for a LONG time - I remember in the early 70s reading an article in popular science on a system to extract waste heat from car engines. It "worked" but the added weight and expense made it not worth the effort.

An interesting tidbit is that modern aircraft jet engines are LESS efficient than piston aircraft engines in terms of mechanical energy delivered for the fuel used. Almost all modern transport aircraft use jets because the power to weight is so much higher than for piston engines that the overall efficiency of the aircraft is better than with piston engines.

Re:E = (T2-T1) / T1

[Anonymous Coward]

You realize nuclear, coal, and natural gas fired powered plants are "steam engines" right?

Re:E = (T2-T1) / T1

[jinchoung]

nobody talking about steam engines....

http://en.wikipedia.org/wiki/T...

Re:E = (T2-T1) / T1

[SleazyRidr]

The same principle apply to steam engines as to thermoelectric devices. Steam engines are very well studied, so there is a lot more data/manuals/advice/working knowledge about them. We choose which knowledge to use and which to discard based on their applicability to the task at hand.

The thermoelectric effect is dependent upon a difference in temperature. To get more power, you need a bigger difference in temperature. Engines do produce a lot of waste heat, but they generally do not get to a high enough temperature to reasonably extract enough of it to justify your capital costs. Thus the comparison to waste steam from steam engines, you can collect and use it, but often you won't get enough out of it to be worthwhile.

Re:E = (T2-T1) / T1

[SleazyRidr]

Looking up at the title, I notice that it claims thermoelectrics could one day power *cars*.

Also, power plants use a closed loop, so talking about putting multiple expanders on them is silly, as the waste pressure/energy gets recycled completely anyway.

Re:Not so fast, Thermodynamic laws are pesky thing

[Anonymous Coward]

Before you make a bigger ass of yourself, please look up what "waste heat" actually is and familiarize yourself with the "Thermo" in thermodynamics.

Engines run HOT. Every bit of heat that travels into the metal and outside the engine is lost energy. Capturing bits of that lost energy and putting it to good use is the concept here. This is waste heat, so it is free, just as eating food out of the garbage bin is "free food" -- someone else paid for it, but they threw it out so it is "free" for you. It's not disobeying thermodynamics any more than burning a gallon of gasoline to make a car move 30 miles is disobeying the laws of thermodynamics.

For other automotive-related things that defy your idiotic concept of physics, please see turbochargers and hybrid cars.

Because like standard panels

[raymorris]

> Sun + focusing device + black metal + thermoelectric = cheap electricity.

With a four foot diameter focusing lens, you could almost power an iPod.
With a lens a mile across, you could power a house. Of course the lens would cost $XX million. Rather than "cheap electricity", this would be "outrageously expensive electricity".

> Why not use this in place of expensive solar panels?

Indeed, why not. The idea has a lot in common with typical c-Si solar panels: extremely expensive, and provides power for several hours per day, but only on sunny days. I bet you can get the government to give you half a billion dollars to start thinking about maybe someday producing them.

Re:Because like standard panels

[Anonymous Coward]

Luddite. Hard drives got better, therefore everything else will too. Especially when you put them in space. Then they really get better.

Prius does better

[Anonymous Coward]

The toyota prius engine is about ~38 percent efficient. The prius also has some prius specific stuff to get its mpg higher, but hybrid synergy drive can be applied to a variety of vehicles. oh yes, internal combustion engines are quite cheap... i imagine thermoelectrics are useful in deep probe probes.

Re:Not so fast, Thermodynamic laws are pesky thing

[Anonymous Coward]

Yeah, but extracting the heat from that warm water is not going to really get you any current worth measuring. What makes this work is a high delta-T between the two sides of the thermoelectric. A few degrees is as good as worthless.

Re:Not so fast, Thermodynamic laws are pesky thing

[bobbied]

Lisa, in this house, we obey the LAWS OF THERMODYNAMICS!!!!

LOL Why yes, yes we do. Like it or not.

Could I use these to cool my data center?

[mmell]

Replace current refrigeration/cooling technology (essentially heat pumping or heat moving) with this - I get paid to provide cooling or refrigeration, not in cash but in Watts. Put in calories (which I wanted to get rid of anyhow), pull out watts.

And - no, I don't want to hear about perpetual motion. The only perpetual motion machine in the Universe is the Universe, and the jury's still out on that one.

Sounds fishy

[exploder]

they have used a cheap, well-known material to create the most heat-hungry thermoelectric so far

Did they do it with one weird trick discovered by a mom?

And they will fly too!

[Anonymous Coward]

I'm sure we will get this technology in cars right after we all get flying cars.

Re:Not so fast, Thermodynamic laws are pesky thing

[DerekLyons]

Any energy you manage to get, will be lost someplace else because you put these devices in the heat flow.

You sir, are ignorant as fuck. It's a sad comment on the state of affairs that a clueless bullshit comment like your could be moderated informative.

We've been extracting energy from waste heat, without incurring extra losses, for over a century now - it's been a standard practice in steam engineering since the 1800's. In the same way, if you put these devices in an IC engine's exhaust you can recover energy that would otherwise simply be vented into the atmosphere without incurring any losses "someplace else".
 

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.

Before cautioning others to educate themselves, first pull your head out of your own ass and educate yourself.

Re:Not so fast, Thermodynamic laws are pesky thing

[cusco]

There's a lot of energy available from an IC engine. If you doubt me let your car run for anything more than two minutes and then touch the exhaust manifold. Bumped one with my arm when I was in high school and it took twelve years for the scar to fade.

Re:Not so fast, Thermodynamic laws are pesky thing

[bobbied]

Any energy you manage to get, will be lost someplace else because you put these devices in the heat flow.

You sir, are ignorant . It's a sad comment on the state of affairs that a clueless bullshit comment like your could be moderated informative.

We've been extracting energy from waste heat, without incurring extra losses, for over a century now - i

Calm down and think about what I said. Your average power plant is pretty darn good efficiency wise (which is what I said if you don't mind reading), which is exactly what you are saying too. Yea, we've come a long way from just dumping waste steam, we have optimized things very well actually. I'm saying that there is very little room for improvement left at this point and there is NO FREE LUNCH here. These devices that convert heat flow directly to electric power are NOT going to increase the efficiency of industrial scale power plants. These devices are simply NOT EFFICIENT enough and will disrupt the current efficiency we've already designed in, they will only disrupt the heat flow, raise entropy and result in less power output for the same input. They don't help.

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.

Before cautioning others to educate themselves, first pull your head out of your own ass and educate yourself.

What on earth did I say that was incorrect? I admit to having struggled with thermodynamics class, but I believe I captured the essence of heat engines and efficiency. So you want to step down off the pedestal and discuss exactly what you think I have wrong in my understanding of thermodynamics? Or are you going to stay up there and keep yelling about how stupid everybody else is?

Re:Not so fast, Thermodynamic laws are pesky thing

[bobbied]

There's a lot of energy available from an IC engine. If you doubt me let your car run for anything more than two minutes and then touch the exhaust manifold. Bumped one with my arm when I was in high school and it took twelve years for the scar to fade.

Which is why I stipulate that these heat to electricity devices MIGHT be of value for internal combustion engines. The heat dumped by them is significant and the temperature differential quite high. There is at least opportunity to get something that would normally just get dumped. I just openly wonder if for a car or truck it will be worth the cost, weight and complexity it will add. I strongly suspect that it's not worth it, but I'm not totally sure.

percentages

[Anonymous Coward]

Anyone have some percentages as to how much of the chemical energy of fuel gets turned into sweet, sweet electrical energy? If its anywhere near a ICE, we got a winner.

Re:Not so fast, Thermodynamic laws are pesky thing

[Anonymous Coward]

The waste heat is rarely free in modern engines, at least in any practical quantities. By adding devices to recover a small amount of power, you necessarily increase the temperature the engine block runs at which may cause efficiency problems elsewhere, whether from causing changes in the thermodynamics of the main operation of the engine, or necessitating changes in design to handle the higher temperatures. Turbocharges are not the greatest example, because they have the analogous problem of creating back pressure that makes the engine run less efficiently, but over comes this by using more fuel. It is a net gain in power, but not in efficiency.

Re:Not so fast, Thermodynamic laws are pesky thing

[bobbied]

Nuclear power plants are very efficient, yet they still use cooling towers and still run millions of gallons of heated water through cooling ponds. This technology is about capturing waste heat, which is the product of a process which has already obeyed all the rules of thermodynamics.

Here we go "waste heat". Please learn a bit more about thermodynamics and heat engines. Power is generated from the TRANSFER of heat. Power plants are huge heat engines, that produce electrical power by taking heat from a high temperature source, transferring that heat to a low temperature sink. There is very little WASTE in a power plant (nuclear or otherwise). Yes you have to dump heat to generate power, but it is not like you are just wasting power when you dump heat. This "waste heat" is not a free resource you can exploit to get more power from the plant.

Adding any other devices in the path of the heat flow will only impede the heat flow and drive down efficiency. I contend that the loss of efficiency will be more than the power you can generate using devices that directly convert heat transfer to electrical power. These devices are not nearly as efficient as what we have already in a modern power plant, thus there is zero chance they will be better.

Re:Not so fast, Thermodynamic laws are pesky thing

[bobbied]

I'm not sure how the cooling works for PV cells. But, if they are actively cooling the liquid there is little to be gained from this arrangement and it is likely going to lead to hotter cell temperatures and cooler liquid temperatures.

So it *might* work, but only if the temperature differential they can stand is high enough and they are not expending energy to cool the liquid through some heat engine.... (I.e. if they use something like a swamp cooler or something.)

Re:Not so fast, Thermodynamic laws are pesky thing

[bobbied]

Until these devices they describe approach the current efficiency of a power plant, there is zero chance they will be helpful on an industrial scale. Modern power plants are usually within a few percentage points of ideal so these devices are going to have to come way up the efficiency scale, and they are horrible now. Given how they work at the subatomic level (holes, electrons etc) I seriously doubt we are in any danger of reaching this level.

Re:Not so fast, Thermodynamic laws are pesky thing

[Immerman]

The maximum limit on an an arbitrary heat-conversion system is that doesn't break accepted theory is the Carnot-cycle heat engine, where eff 1 - T_cold / T_hot (as measured from absolute 0). But it's a rare real-world engine that gets anywhere near the Carnot efficiency limit - a car engine might run at 1100K for an ideal efficiency of around 73%, but the reality in most cars is closer to 25%. Being solid-state a thermoelectric device could potentially operate at very near the ideal (no mechanical losses), roughly tripling the efficiency. Assuming 90% efficient electric wheel motors the total system efficiency could be nearly as high.

Re:Not so fast, Thermodynamic laws are pesky thing

[bobbied]

Before you make a bigger ass of yourself, please look up what "waste heat" actually is and familiarize yourself with the "Thermo" in thermodynamics.

Engines run HOT. Every bit of heat that travels into the metal and outside the engine is lost energy. Capturing bits of that lost energy and putting it to good use is the concept here. This is waste heat, so it is free, just as eating food out of the garbage bin is "free food" -- someone else paid for it, but they threw it out so it is "free" for you. It's not disobeying thermodynamics any more than burning a gallon of gasoline to make a car move 30 miles is disobeying the laws of thermodynamics.

For other automotive-related things that defy your idiotic concept of physics, please see turbochargers and hybrid cars.

If you read my post.... (and apparently you didn't) ... I specifically stipulate that automotive applications *might* be successful and worth of investigation. The reason I say this is because of the huge amounts of heat transferred out the tail pipe and radiator in a modern internal combustion engine at sometimes very high temperature differentials leaves something to recover. This is totally unlike a modern power plant, where heat transfer has been carefully engineered to be as efficient as possible, thus leaving little room for thermodynamic improvement. However, my doubts about automotive application are over costs, weight and complexity not about the Thermodynamics of the application.

Re:Not so fast, Thermodynamic laws are pesky thing

[bobbied]

The maximum limit on an an arbitrary heat-conversion system is that doesn't break accepted theory is the Carnot-cycle heat engine, where eff 1 - T_cold / T_hot (as measured from absolute 0). But it's a rare real-world engine that gets anywhere near the Carnot efficiency limit - a car engine might run at 1100K for an ideal efficiency of around 73%, but the reality in most cars is closer to 25%. Being solid-state a thermoelectric device could potentially operate at very near the ideal (no mechanical losses), roughly tripling the efficiency. Assuming 90% efficient electric wheel motors the total system efficiency could be nearly as high.

Don't be fooled that "hey they are solid state and convert directly to electricity". Deep down, it's still a physical process that produces electricity, even if the moving parts are not something you can see. In actual practice, what happens with these things produces horrible efficiency.

These electronic devices are semiconductor junctions that you get heat to flow through in hopes the electrons will bounce their way across the junction into the cooler side and get stuck... They are not efficient from a thermodynamic perspective, and unless my physical understanding of how they work is totally wrong, they are never going to approach the efficiency of even an internal combustion engine, from a thermodynamic perspective anyway.

Re:Not so fast, Thermodynamic laws are pesky thing

[cusco]

Then I misunderstood your previous post, which I took to mean that there wasn't enough to bother with. It would be interesting to me to see an estimate of how much it would cost to make an exhaust manifold of thermocouple material, and what the estimated output would be. With hybrid vehicles like the Prius, which just uses the IC engine to charge the batteries that actually propel it, it might well be worth it.

More distractions...

[Anonymous Coward]

We have cars that run on compressed air. If we REALLY wanted to end our dependence on fossil fuels, we'd have done so by now.

All this is, is another bullshit attempt to get us to believe we are actually looking for fuel alternatives. Meanwhile, the oil companies continue to shove their corporate cock up our ass and then laugh about it while vacationing with their families in the Bahamas.

Fuck this worthless research and fuck anyone who disagrees.

Mod me a toll, i don't even care. Truth is truth, regardless of ignorance.

there is no such thing as wasted heat

[Anonymous Coward]

The universe is dark and cold on average.
On average, I am a poor, Chinese female.
I am counting on you overclockers, you're our only hope.

Screw cars... cool/power my server room

[Anonymous Coward]

Anything that can take heat and turn it back into electricity for the machine room sounds good to me.

Let me give an example of "might"

[dbIII]

Back a few years there was a quest for an all ceramic car engine. Fuel could burn a lot hotter so your could get a lot more power per litre. It seemed obvious. A few partial successes happened and then Mercedes actually built one. On a test bed the performance was wonderful. In a car the extra weight required to keep it cool made the performance of a 1936 Chevy look better. In the end some ceramic parts are in use, mostly in trucks, but making it all ceramic to get those higher temperatures is impractical in something that has to move it's own weight around.
So it all comes down to physical contraints instead of yelling OMG flying car! Please forgive us for not being instant fanboys until we know something about what is going to distinguish this thing from reverse peltier effect devices we already know about. The thing has got to be able to add more performance than it reduces by weight for it to be worth it.

Re:Not so fast, Thermodynamic laws are pesky thing

[jinchoung]

why is waste heat "garbage"?

are you denying that there is such a thing? that we are currently actively cooling parts and attaching heat sinks and radiators for merely decorative purposes?

and if waste heat is an actual phenomenon... why NOT harvest energy from it? complexity is low with no moving parts. price is currently high but as with most things, that can come down with research.

so waste heat exists. power can be harvested.

i don't see what the point of your tirade is.

Re:Not so fast, Thermodynamic laws are pesky thing

[jinchoung]

nothing to do with heat engines. THERMOELECTRICS.

read article first

[jinchoung]

1. http://news.sciencemag.org/che...
2. NOT HEAT ENGINE. THERMOELECTRICS!

Re:Not so fast, Thermodynamic laws are pesky thing

[Vellmont]

Umm.. so the article was focused on the abstract idea of increasing efficiency of thermoelectric generators. The practical idea (and even the article title) was about how it might be able to power a car more efficiently. But yet you focus right in on how it's never going to work. (Why yes, I DO understand the carnot limit of heat engines).

The article never talked about massive gains in heat efficiency for power plants, just scavenging waste heat. Right now we have massive cooling towers at power plants to get rid of waste heat, which sometimes provides problems for increased temperatures of waterways. If you could make an efficient thermoelectric device like this you might be able to take some of that waste heat and turn it into usable electricity, reducing your cooling needs and producing power at the same time. A 600MW coal plant going from a 33% efficient to 34% would produce an additional 18MW. That's not bad. At .02 a kilowatt hour, that's nearly $9000 a day.

So no, there's nothing really to "debunk" here, since no claims are really made about large gains in efficiency.

Gasoline Thermal Efficiency is now ~40%, Diesel ~4

[Anonymous Coward]

For example,
http://www.greencarreports.com/news/1091436_toyota-gasoline-engine-achieves-thermal-efficiency-of-38-percent

Re:Not so fast, Thermodynamic laws are pesky thing

[Anonymous Coward]

So still no pew-pew laser cannons that use these as heatsinks and to increase energy efficiency since about 95% of the energy is used to keep the laser process running, heating up all that stuff?

That makes me sad. I suppose I have to continue using those Peltier elements for temperature regulation instead of harvesting all of that juicy waste heat :(.

Re:Not so fast, Thermodynamic laws are pesky thing

[confused one]

One could argue that it can be modelled with thermodynamics...

Re:Not so fast, Thermodynamic laws are pesky thing

[Anonymous Coward]

While it should be obvious, due to thermodynamics, why we can't stop heat from going to 'waste', perhaps you should explain how thermoelectrics work, since this might be the confusing part for some people.

Thermoelectric generation is all about heat gradients. Basically on one side you want it hot and on the other side you want it to be a lot 'less hot', like a low temperature sink. One might call that TRANSFER of heat.
At least in theory you could use them to power a car. Sure you need some fuel to generate heat, but it doesn't have to be from a classical heat engine. The Mars rover Curiosity uses a radioisotope thermoelectric generator, which, dumbed down is a thermoelectric element fueled by a radioactive source. Practically this would be insane in a human environment, but in theory and on Mars it does work.

Re:Not so fast, Thermodynamic laws are pesky thing

[Anonymous Coward]

Cooling like in PV thermal hybrid solar collectors? First, there is no 'waste heat' in these systems, since heat is utilized by the thermal collector.

Yeah, sure, you could increase the gain in electrical energy, it sounds reasonable to increase efficiency here, but it would drive down the efficiency of the thermal collector. Always think about the fact that when you take out energy here, then you will have less energy somewhere else. Certainly there is more use for electrical energy than for thermal energy but the huge problem here is how to store electrical energy. While thermal storage is rather easy, since all matter acts like a thermal capacitor, with various degrees of efficiency, we certainly have problems storing 'electrons'.
Energy from the thermal collectors is directly used to heat water in a house. Water that is used for bathing, showering, laundry, dishes and it lowers the energy needed for cooking. The big practical question here would be if the energy harvested by the thermoelectric components would be more efficient to heat water for bathing, showering, laundry and dishes than the energy harvested by the thermal collectors.

Re:Not so fast, Thermodynamic laws are pesky thing

[lisaparratt]

Build deep thermally insulating foundations, pump the excess heat into the earth underneath the property, then use thermoelectrics to bleed it off and produce electricity at night when the photovoltaics won't work.

Re:Not so fast, Thermodynamic laws are pesky thing

[StripedCow]

Unless it is haunted by a Maxwell demon.

Not usefull for waste heat

[Neil Boekend]

Waste heat is often a lot and usually needs to be moved away fast.
If you let the heatflow of a car pass through these tiles you's need a lot more surface area to get sufficient heat out of the engine.
If you try to cool a CPU through these things the CPU will overheat quite soon.
These things have "Ultralow thermal conductivity" according to the article. That means they act as thermal insulators. Not what you want when using waste heat.
This is useful for other places.
1. Places where you can replace insulation. A house has too low delta T, but I could imagine the inside of the burn chamber of a central heating installation.
2. Places where heat is generated for the specific purpose of powering these thermoelectric tiles. Then you have less losses from normal thermal conductivity.

Re:Not so fast, Thermodynamic laws are pesky thing

[Anonymous Coward]

The problem I see here is that there is a lot of energy conversion going on.
Now if you have a thermal capacitor underneath your house the question would be if that stored energy would be put to better use w/o converting it to electrical energy. Obviously, you can't run your TV on thermal energy, but pumping the heat back into the house and use it directly for heating purposes might be more efficient.
Here in Germany there are already a few passive houses, that store energy in a similar way and also utilize photovoltaics and thermal collectors. In addition to this thermoelectric generators could be used in future designs.

And there is also thermo-photovoltaics, which is a promising field when it comes to converting thermal to electrical energy. But considering the current temperatures respective emitters require to work properly, it's rather impractical for domestic use.

Re:Not so fast, Thermodynamic laws are pesky thing

[MachineShedFred]

We're talking about cars here, right? At least, TFA is.

Currently, cars dump hot exhaust gases out the back end without doing anything with the heat, because it's a byproduct of the mechanical force created through ignition of fuel. IC engines don't use the heat very much - they use the expansion of gases to create mechanical work, and the "waste heat" blows out the tailpipe as, you know, waste.

If you could harness that heat in some way to create electrical or mechanical power, you're more efficient than today where that heat (read: energy) is used for NOTHING. I don't know why you seem to think that it wouldn't work, because auto manufacturers seem to think that it will (BMW, Honda - links in a previous post from someone else), and are engineering systems to do exactly that.

Re:Not so fast, Thermodynamic laws are pesky thing

[bobbied]

The article mentions power plants near the end.

Where I'm dubious about the usefulness of this technology in cars, I would agree that there is at least a possibility it could help. Thermodynamics would allow it. However, in a power plant, Thermodynamics tell me they are not useful.

I also wonder if the original author and the researchers involved actually understand the issues, given they try and present this as a way to improve a power plant. On that point they are totally and obviously mistaken. If they are that far off on that point, I have to start questioning the rest of their ideas because they are obviously either ignorant or deliberately misleading.

Re:Not so fast, Thermodynamic laws are pesky thing

[bobbied]

The article never talked about massive gains in heat efficiency for power plants, just scavenging waste heat.

You are falling for the waste heat argument. Power is generated by the transfer of heat from a high temperature source to a low temperature sink. In a power plant, we've managed to engineer them pretty well and we get pretty close to the ideal. Any new device will have to exceed the existing efficiency or it simply will not help, but hurt. Remember it is the TRANSFER of heat that is used to produce power, not the heat energy itself. So the "dumping of waste heat" is not a power loss in the system where you can hope to get gains from.

If you are familiar with the ideal cycle, remember that this cycle requires the transfer of heat to and from the working fluid/gas at a constant temperature. The devices being described require fairly high temperature differentials to operate. They simply *cannot* be as efficient because of this, and if I understand the physics, they will never really be all that more efficient than they are now.

Re:Not so fast, Thermodynamic laws are pesky thing

[bobbied]

nothing to do with heat engines. THERMOELECTRICS.

Which are subject to the laws of Thermodynamics even if you don't think so....

Your claim is like saying because it's solid state, it has nothing to do with electric fields... Totally and completely false.

Claims like this is where perpetual energy scams get started. "Hey, look at this design, Energy for FREE! (Thermodynamics just *don't* apply.)"

Re:Not so fast, Thermodynamic laws are pesky thing

[newcastlejon]

why is waste heat "garbage"?

Because it's low temperature and high entropy.

...that we are currently actively cooling parts and attaching heat sinks and radiators for merely decorative purposes?

No, we do it because the devices need to be cooled and it's not worth the expense of slapping a thermocouple on them for the pitiful return one would get.

and if waste heat is an actual phenomenon... why NOT harvest energy from it?

See point the first.

complexity is low with no moving parts.

We've been making ICEs for a long time; we know how to make them reliable. Just because an alternative is presented that's solid state doesn't mean we should automatically jump on it.

price is currently high but as with most things, that can come down with research.

Then report a story that says "powers car" instead of "could one day power cars"

so waste heat exists. power can be harvested.

Never in dispute, but that doesn't mean it's worth doing. Look at it this way, would you go to the trouble of putting a heat exchanger between your bathroom plughole and the inlet for your heating system? There's waste heat there too, but not enough to justify the expense you'd be in for. That's to say nothing of the fact that it would be immensely more efficient than a theromelectric doodad.

i don't see what the point of your tirade is.

I'm guessing here, but maybe it's because the parent is frustrated that you don't appear to see that there's a reason it's called waste heat. Seriously, a large sink sitting slighty above ambient temperature may hold quite a lot of energy, but it's not practical to try and extract any work from it. As an exercise, read up a little on two things: Carnot efficiency, which has been covered nicely by posts above, and low grade heat, which is only really useful for heating something colder, not anything that needs a temperature differential (i.e. any heat engine, solid state or otherwise.)

Re:Not so fast, Thermodynamic laws are pesky thing

[bobbied]

You fell for the "waste heat" argument garbage didn't you... So sorry.

The conversion of heat energy to another form (electricity in this case) requires the TRANSFER of heat from a source to a sink. What we "dump" in the sink is called "waste heat" but that does not imply it is somehow useable to produce more power output from the plant (assuming a modern power plant). The most efficient conditions for an idea heat engine is when the heat is transferred at a constant temperature and in modern power plants they go to great lengths to approach this ideal.

Thermoelectrics generally require fairly high temperature differentials to operate. By the laws of thermodynamics, this means that they are never going to be efficient, and trying to use them in a power plant simply cannot be helpful to it's efficiency. Sorry, the laws of thermodynamics still apply here.

I hate personal definitions

[dbIII]

Ah, I see now. Differing definitions of what ignition under pressure and how the resulting sudden gas expansion is described. Where do the larger explosions such as sometimes occurs in the F1 engine in the Saturn V fit in your definition - are they also not explosions or is your line drawn somewhere between the two? Are you someone with the 1930s gunpowder engine idea or is it coming from somewhere else that actually considers that carrying around an oxidiser when you do not need to is a drawback?
To sum up - when you "correct" somebody it's best to consider which parts of your correction are based on your own gut feelings and which are more easily communicated. I'm intrigued by your explosion powered engine idea but suspect it's the same drivel dreamed up by people without a grasp on the topic that are missing a major flaw - if not please feel free to tell us exactly why they will "replace scramjets" - which as you should know are only there to replace rockets because they can save the weight of an oxidiser (so your explosive powered system sounds a bit like a step backwards).

Re:I hate personal definitions

[ShieldW0lf]

As far as the difference between deflagration and detonation, you may find this helpful:

http://en.wikipedia.org/wiki/D...

Why do I say it's hoped that they will replace scramjets? Because aerospace and military engineers are spending millions of dollars working on trying to engineer them as a replacement for scramjets and hoping they succeed:

http://en.wikipedia.org/wiki/P...

I was apparently mistaken about there not having ever been a PDE powered flight... looks like researchers flew one for 10 seconds at an altitude of 100 feet with engines that create detonations at a frequency of 80 Hz.

I imagine a power station that could harness the power of nitroglycerin. Nitro is cheap as hell to make and releases incredible power... I'd love to try and build a plant that's buried deep in bracing rock and uses a very dense inert metallic alloy as a hydraulic fluid to harness the incredible power of cheap organic explosives.

Re:I hate personal definitions

[dbIII]

I was apparently mistaken about there not having ever been a PDE powered flight

From France to London in the mid 1940s - get a grip before trying to lecture others who are not entirely keyboard jockeys.

Re:I hate personal definitions

[ShieldW0lf]

I was apparently mistaken about there not having ever been a PDE powered flight

From France to London in the mid 1940s - get a grip before trying to lecture others who are not entirely keyboard jockeys.

Do you have any more information? I can't find any references to a successful PDE powered flight outside of the work being done by the Air Force Research Laboratory and Innovative Scientific Solutions, Inc.

Re:I hate personal definitions

[dbIII]

V1

Re:I hate personal definitions

[ShieldW0lf]

I assume that picture was meant to be a German V-1 flying bomb? Those were pulse jet engines, but not pulse detonation engines. They used the expanding gas of repeated combustion reactions, they didn't cause fuel to detonate.

Re:I hate personal definitions

[dbIII]

More than 10m/s expansion so explosion by your pet definition isn't it? I also suggest your read the wikipedia link you sent to me.

Re:I hate personal definitions

[ShieldW0lf]

Dude, you're the worst sort of person to argue with. You've demonstrated poor reading comprehension and a willingness to hand-wave away the distinction between similar words if you don't think they are relevant to you or serve your position. You seriously make me wonder why I even bother trying to express myself precisely

I never used the word explosion. I used the word detonation. I contrasted it with the deflagration that occurs in internal combustion engines like we see in cars.

A detonation occurs when the shock wave expanding out of the reaction zone compresses the unburnt fuel ahead of the wave, and the compressive heating raises the temperature in the unburnt fuel above it's autoignition temperature.

10 m/s is well below the threshold. Try 2000 m/s.

Detonation produces a more efficient combustion than deflagration, gives higher yields, and generates more kinetic force relative to the thermal energy released. It's a whole different kettle of fish.

Re:I hate personal definitions

[dbIII]

Yes - someone pointing out that you are arguing from a position of ignorance really sucks doesn't it? Especially after you have delivering a patronising putdown to someone who knew more about the topic than yourself twenty years ago and has moved on since.

Re:I hate personal definitions

[dbIII]

I never used the word explosion

I used the word explosion and then you delivered your patronising "correction".

Re:I hate personal definitions

[ShieldW0lf]

You're not really going to humiliate yourself by continuing this, are you?

Re:I hate personal definitions

[dbIII]

I think you have got that somewhat backwards Mr keyboard jockey :)
You are supposed to read and understand before cutting and pasting.

Re:I hate personal definitions

[Anonymous Coward]

Such a statement is never anything but a total and unconditional surrender.

garbage

[Anonymous Coward]

So tired of garbage science. You can't transport a ceasar salad 7,000 miles on waste heat.

A bit too insulting keyboard jockey

[dbIII]

Hey - IT dude - I first saw a working scramjet model in 1986 when I was learning how to be an engineer so don't need some lecture from you about that or some condescending shit about how I should learn about diesel engines (arbitrary definition shift at 100m/s) from someone who doesn't know about them himself or some stuff about people in very early stages of attempting to revive the V1 engine (fair enough, but stating it as if it's viable now - that is insulting the intelligence of yourself and the readers here).

Nitro is cheap as hell to make and releases incredible power

The world has moved on to better things that are a hell of a lot cheaper per watt (even ANFO needs too much energy input to be considered for routine use as a fuel), and for transport it would suck because it's extra weight for the same sort of energy density you get from something that you add available oxygen to. In the 1930s there was a lot of speculation about running aircraft engines on explosives which went as far as rocket planes and no more because of all that extra mass of fuel - the jet engine mostly killed off that idea apart from really fast planes, it's just not practical to take that extra weight unless you are in a huge hurry. The idea of a scramjet is like a rocket that needs less fuel since it can compress enough oxygen to burn out of the air - going back to a V1 style pulse jet is a step backwards since it means carrying a lot more fuel for little or no gain.

very dense inert metallic alloy as a hydraulic fluid

That's a bit too much. Are you deliberately pulling my leg here to make fun of me or are you just using real words as technobabble you do not understand to attempt to convey some other meaning about a molten tungsten mixture or something?

Re:A bit too insulting keyboard jockey

[ShieldW0lf]

Sorry, I'm not an engineer. I've worked in a fireworks factory and made my own model rockets, but I'm not a professional.

And no, I was thinking something like Galinstan, and not for propulsion, but for a power station.

Re:A bit too insulting keyboard jockey

[dbIII]

I'm sorry I was so blunt but your "correction" of my description of diesel was a bit annoying and appeared to both ignorant and patronising as such cut and pastes with understanding often do on the net.

The main downside of using explosives as a fuel at this point is that coal, oil, gas etc are very cheap and the energy cost of turning them into other stuff that explodes is higher than the energy you get out of the explosions. With nearly free electricity you can get nearly free hydrogen so the game changes, but until then it's the same dream from the time of Nobel that isn't much getting closer. As for transport the downside of explosives is you have all that oxygen in the tank, while with combustion the idea is to only carry half of an explosive.
IMHO the difference between a fuel air explosive and a diesel cylinder is scale. The term for a little explosion may be deflagration, but that's just describing the scale below an arbitrary cut-off point. Physically, chemically and mechanically the same thing is going on.
At least now think I get what you are going on about - rocket motors pushing liquid metal around? The very dense threw me initially and made me think you were referring to some sort of solid heavy metals - for instance lead flows really well at high pressures not far above room temperature, but not well enough to last long so a full liquid like you suggest makes more sense. If that's what you mean there are a few interesting challenges but at least some are being actively worked on (the nuclear industry is busy trying to solve some liquid metal problems, mostly in Russia and India).

Re:Not so fast, Thermodynamic laws are pesky thing

[metaforest]

If you could harness that heat in some way to create electrical or mechanical power, you're more efficient than today where that heat (read: energy) is used for NOTHING. I don't know why you seem to think that it wouldn't work, because auto manufacturers seem to think that it will (BMW, Honda - links in a previous post from someone else), and are engineering systems to do exactly that.

Oh you mean like a pair of turbo chargers do? That increases the intake pressure to improve the power efficiency of the ICE when it is running at high output? The turbo charger is a much more effective use of 'waste heat' than what Honda and BMW are doing. Oh and the 'waste heat' is also used to keep the catalytic converter active to break down all the partially burned hydrocarbons in the gas. Ask yourself why the turbine portion of the turbo-pump is as close to the exhaust-ports as practical? I'll give you a hint: for thermodynamic efficiency the input side of the turbine housing needs to be as hot as possible. Putting after the catalyst would reduce efficiency because the cat is consuming heat energy to oxidize the combustion products.

Heck, using the 'waste heat' from the coolant to warm/dehumidify the cabin, is a more efficient use than these tin selenide whiskers would ever be. So why do we use a rather bulky gas compressor for air-conditioning rather than a heat pump driven off 'waste heat'... After all PLG refrigerators (commonly found in RVs and RTs) have been using this technique for at least 40 years. Hint: it is more efficient to steal a few HP off the engine than to try and generate that energy off the coolant or the exhaust stream.

Bobbied is right, most of you here have no clue about thermodynamics... I know just enough to know most of you just don't get it.

What it really comes down to is there is simply not as much energy in the 'waste heat' from an ICE as most of you here seem to think.
That 15% to 25% efficiency in ICEs hides the source of the losses. Most of the inefficiency comes from reciprocating mass, friction and pumping losses. What little energy is available in the exhaust systems (exhaust and cooling) is already being used and after that there is just not much left.

I agree with bobbied all the way around. The only big win here is going to be increased efficiency of RTGs, and those are only used in power systems where there really is no other option.
 

Nuclear weapons use fission and/or fusion; hence '

[Anonymous Coward]

nt

Oh, Slashdot...

[Anonymous Coward]

...hence 'nuclear' weapons.

Re:Not so fast, Thermodynamic laws are pesky thing

[MachineShedFred]

Wrong.

Guess what? BMW turbocharges practically every engine they make, so I'm guessing their engineers know more about this than you. I have one that actually has two turbos - specifically the 3.0L inline 6 twin turbo N54.

They aren't close to the engine for heat reasons - they are close to the engine because the turbo needs to be close to the air intake and exhaust at the same time, and that only happens at the engine. A turbocharger works by having the exhaust gases coming out of the engine at pressure (not heat, still mechanical work) spin a turbine which is connected to an air pump in the intake by a shaft. This spins VERY fast (150k RPM) so they also need to use a fluid bearing, so being close to the engine allows the use of engine oil as well.

It has nothing to do with heat, and everything to do with not having oil, air, and exhaust lines crisscrossing the whole fucking car.

Re:Nuclear weapons use fission and/or fusion; henc

[tragedy]

Ummm, what?

Of course you did

[dbIII]

I never used the word explosion

What? The entire reason I got on this thread to be "corrected" was this text of yours.

If you built a car engine that delivered power by causing fuel to explode

Then for another thing, your pet word for the day is on this page - please learn that it is a form of explosion instead of your personal definition.
http://www.exponent.com/explos...

Don't accuse me of poor reading comprehension just because you have written something different to what you wished in hindsight.