Material Breaks Record For Turning Heat Into Electricity

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Material Breaks Record For Turning Heat Into Electricity

Posted by Soulskill on Wednesday September 19, 2012 @10:39AM from the hot-shocking-news dept.

ananyo writes "A new material has broken the record for converting heat into electricity. The material had a conversion efficiency of about 15% — double that of one of the most well-known thermoelectrics: lead telluride (abstract). For decades, physicists have toyed with ways to convert heat into electricity directly. Materials known as thermoelectrics use temperature differences to drive electrons from one end to another. The displaced electrons create a voltage that can in turn be used to power other things, much like a battery. Such materials have found niche applications: the Curiosity rover trundling about on the surface of Mars, for example, uses thermoelectrics to turn heat from its plutonium power source into electricity. That doesn't mean that the material is ready to be used on the next Mars rover, however: NASA has been looking at similar materials for future space missions, but the agency is not yet convinced that they are ready for primetime."

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heatsinks by Anonymous Coward · 2012-09-19 10:43 · Score: 3, Interesting

What stops this and materials like it from being used as heat sinks to recover some of the energy lost?
1. Re:heatsinks by schitso · 2012-09-19 10:45 · Score: 1
  
  Doesn't the answer to such questions usually turn out to be "cost"?
2. Re:heatsinks by Anonymous Coward · 2012-09-19 10:51 · Score: 5, Informative
  
  In a heat-sink you want to carry heat away from an object. A termoelectric is by definition a poor heat-sink because it requires a temperature gradient to work. This gradient means that the material is a poor conductor of heat. If it were a good conductor then both sides would quickly reach the same temperature and it would stop working.
3. Re:heatsinks by thejuggler · 2012-09-19 10:55 · Score: 1
  
  Nothing really - that would be a very creative use to recapture some lost energy dissipated as heat. But at 15% efficiency it's possible that it's not feasible to add into any device. Besides the thermoelectric material you have to have an addition circuit to capture the energy and a battery storage. If the device already has a battery then it needs to be rechargeable. Its likely that this would act more as a trickle charge than a full fledge charger. In my reading of TFA I did not notice a temperature range that these thermoelectric materials need to operate within.
4. Re:heatsinks by Rockoon · 2012-09-19 11:09 · Score: 2
  
  It should be noted that this article is about materials that perform the job of converting temperature gradients into electricity directly. Other methods of doing so are still more efficient (see your local coal, oil, gas, or nuclear plant.)
  
  --
  "His name was James Damore."
5. Re:heatsinks by Anonymous Coward · 2012-09-19 11:12 · Score: 5, Informative
  
  You seem to have a very poor grasp pf thermodynamics but to put it simple I will refer to the article itself.
  "Building a better thermoelectric depends on finding materials that conduct electricity, but not heat"
  There it is in plain language. Thermoelectrics are poor conductors of heat.
  Also, nearly everything you say in your post is simply wrong. You do not convert heat into electricity. You use a heat gradient to cause an electric field. The electrons flow out one side and return to the other. You are not "piping" heat anywhere.
  Thermo-electrics do not run on the heat gradient between themselves and the air. They run on the heat gradient between two sides of the material itself. I can have a block of ceramic at relatively uniform 1000C without it being 'maximally cool'.
6. Re:heatsinks by Rockoon · 2012-09-19 11:13 · Score: 1
  
  If both sides got to the same temperature then you would stop producing electricity, and your device would be maximally* cool
  ...or maximally hot.
  
  --
  "His name was James Damore."
7. Re:heatsinks by Baloroth · 2012-09-19 11:36 · Score: 1
  
  IIRC some laptops do exactly this to recover energy. However, it isn't terribly effective or cost-efficient. You certainly can, though (tends to reduce the effectiveness of the sink as well, although that depends on the exact design.)
  
  --
  "None can love freedom heartily, but good men; the rest love not freedom, but license." --John Milton
8. Re:heatsinks by macraig · 2012-09-19 11:53 · Score: 2
  
  No. You would be attaching a heat sink to one side of this material if, as is most likely, you were going to use it to cool something by driving current through it. That works in reverse when you "flip it over". The most likely first commercial uses of it would be to replace current "Peltier" thermoelectric devices in computer component "coolers" and the portable electric "ice chests" that are actually capable of heating or cooling contents. If this is a more efficient conversion without being much more expensive, then it realizes a power savings for those devices.
  The application TFS is describing for the material is analogous to turning a motor into a generator: instead of current being the input and a temperature gradient across the device being the output, temperature differential becomes the input and a generated current the output.
9. Re:heatsinks by Requiem18th · 2012-09-19 12:40 · Score: 4, Informative
  
  Poor AC getting so mean comments.
  Actually you ARE right, but only from a certain point of view. Firstly, you are right that thermoelectric materials take heat away, and thus cool down whatever they are attached to.
  The critical point here is that merely cooling down is not enough for a heat sink. The heat sink has to be cooled down FAST. Faster than it's heat source is heating it. Thermoelectrics just can't turn heat into electricity fast enough to let a heat sink do it's job.
  So it's not really a matter of thermoelectrics heating up heat sinks, they don't heat them up, they in fact cool them down, what is heating up the heat sink is the heat source (say a CPU or a power engine).
  The problem is that no thermoelectric so far can transform heat intro electricity faster than a CPU turns electricity into heat.
  
  --
  But... the future refused to change.
10. Re:heatsinks by sumdumass · 2012-09-19 13:41 · Score: 1
  
  Well, yes, but what if you can encase them in the lining of an industrial chimney or along the steam lines leaving the turbine generators of the coal, oil, gas, or nuclear plants.
  I think what the op was getting at was recovering energy from waste heat streams. The term heat sink I think was more illustrative of a process of waste heat rather then a function of gathering energy.
  Let's assume your hybrid electric car has a gas engine. What is we ran the exhaust alongside some materials like this so not only do you get a power boost when the engine kicks in to charge or add more power as needed, you get a charge from the waste stream of the process too (sort of like regenerative breaking for internal combustion engines).
11. Re:heatsinks by dbIII · 2012-09-19 13:53 · Score: 4, Informative
  
  Well, yes, but what if you can encase them in the lining of an industrial chimney or along the steam lines leaving the turbine generators of the coal, oil, gas, or nuclear plants.
  Interesting idea, but a similar thing has been done for a century+ with the outgoing steam being used to preheat the incoming water. There's orders of magnitude of difference in energy gained between that and thermocouples at huge scales. However at small scales a steam plant is not possilbe while a thermocouple is.
12. Re:heatsinks by microbox · 2012-09-19 14:11 · Score: 1
  
  The point is that removing 15% is extremely poor performance compared to what a heat sink gives you.
  
  --
  
  Like all pain, suffering is a signal that something isn't right
13. Re:heatsinks by jhol13 · 2012-09-19 14:33 · Score: 1
  
  But it might me usable in cars. AFAIK there are already systems which generate electricity from exhaust heat.
14. Re:heatsinks by Rei · 2012-09-19 15:09 · Score: 2
  
  One thing that this article isn't really consistent on is whether this is 15% of the Carnot efficiency for a given temperature gradient or 15% of the total difference in temperature between the two thermal reservoirs. Also, its performance under different temperature conditions can be very important for some applications, but that's not made clear.
  And for anyone saying "it's not an engine, Carnot doesn't come into account".... wrong. It amazes me how many people think this. Carnot's law applies to any generation of work from heat, period. If you can break Carnot's law, no matter with what sort of device, you can create a perpetual motion machine - that is, you could have your work generated from heat run a high-COP heat pump to pump heat back up against the gradient to keep your machine running. Remember that heat pumps can have COP notably greater than 1.0 - that is, they often can move several times more energy against the gradient than goes into running them. To put it another way, a heat engine will never be able to harness more work from a given temperature gradient than the maximal-efficient heat pump for the same temperature differential.
  
  --
  No, she's fine. My associate is vomiting for a totally unrelated reason.
15. Re:heatsinks by Anonymous Coward · 2012-09-19 16:05 · Score: 1
  
  Unfortunately, you are just incorrect.
  Thermal energy is not being converted. The whole thermocouple system ends up with the same or more heat no matter how much electricity is extracted. The energy is coming from an excited state (hot on one side, cold on the other) tending towards a base state (uniform temperature). It is just like extracting energy from a stretched rubber band, stretched it is in an excited state, you can extract energy from it as it unstretches, but there is still the same rubber band in the end.
  It takes energy to set up a temperature gradient in the first place, and that is the energy you are extracting with this, not the heat itself, but the stored energy of the temperature differential.
16. Re:heatsinks by Anonymous Coward · 2012-09-19 21:37 · Score: 1
  
  Read your own second law more closely.
  Clausius statement
  The German scientist Rudolf Clausius laid the foundation for the second law of thermodynamics in 1850 by examining the relation between heat transfer and work.[5] His formulation of the second law, which was published in German in 1854, is known as the Clausius statement: "Heat can never pass from a colder to a warmer body without some other change, connected therewith, occurring at the same time."[6] This may be restated as[4]
  âoe No process is possible whose sole result is the transfer of heat from a body of lower temperature to a body of higher temperature. â
  Heat cannot spontaneously flow from cold regions to hot regions without external work being performed on the system, which is evident from ordinary experience of refrigeration, for example. In a refrigerator, heat flows from cold to hot, but only when forced by an external agent, the refrigeration system.
  Kelvin statement
  Lord Kelvin expressed the second law as "It is impossible, by means of inanimate material agency, to derive mechanical effect from any portion of matter by cooling it below the temperature of the coldest of the surrounding objects.[7] This may be restated as[4]
  âoe No process is possible in which the sole result is the absorption of heat from a reservoir and its complete conversion into work. â
17. Re:heatsinks by Thammuz · 2012-09-19 22:25 · Score: 5, Interesting
  
  Long time lurker, commenting because I know something about this one (doing my PhD in thermoelectrics).
  First of all, you _can_ use thermoelectrics to cool things like CPUs or fridges, but don't expect to generate any energy from them when you do it because you need to be putting electricity into the system, essentially carrying the thermal energy with it. You will cool one end and heat the other end. If you've ever heard of a Peltier cooler then you know what I am talking about.
  A good background can be found here: http://thermal.ferrotec.com/technology/thermal/thermoelectric-reference-guide/
  Second, this is something people have been messing around with the nanostructure of tellurium alloys for ~20 years or so, with the sole purpose of reducing thermal conductivity. The figure of merit for thermoelectrics is ZT = thermopower^2 x electrical conductivity x temperature / thermal conductivity. You can't increase electrical conductivity without reducing thermopower and increasing thermal conductivity (as there is a lattice and an electrical contribution). Thermopower is more or less a function of the number of carriers (lower is better) and their effective mass, so this is difficult to increase without durastic changes in the crystal structure or killing electrical conductivity. This leaves thermal conductivity. If you increase disorder in the material you make it harder for thermal energy to travel through it, which as lead to lots of research on how you manage this without messing up your carrier conduction. These are known as PGEC (phonon glass electron crystal) materials.
  Third, there are lots of applications of these (in heating/cooling and power conversion) if they can be made efficient and cheap. Anywhere you have a heat source pretty much. To use the classic car analogy, BMW, Ford, GE (amongst others) are looking at using a thermoelectric module to generate power for the car from the waste heat in the exhaust gases from the engine. This would increase the power of your engine by removing the alternator and also make the car lighter.
  The problem is the efficient and cheap part. These kinds of thermoelectrics are based on tellurium, an element about as abundant in the earth's crust as platinum, but to my knowledge isn't specifically mined for. Most other elements involved are toxic heavy metals (Pb, Sb, Bi, etc.)... so these aren't exactly nice things to have around or to make.
  This is where oxides come in. Made of lighter, more abundant, less toxic elements they are much cheaper to make (not just sourcing the materials, heath and safety too etc.), and are stable at much higher temperatures. As you know from Carnot, the higher the temperature a heat engine works at the more efficient it becomes; rather than 900 K (600C) you're looking at more like 1300 k (1000C) and upwards. Current high ZT oxides are things like NaxCoO2 and Ca3Co2O6, which have layered structures; one part is great at absorbing thermal energy (due to Na disorder for example) and the other is good at conducting electricity (like the CoO2 portion of NaxCoO2)
  TL;DR
  The way I see this paper: great proof of concept, PGECs are doing what they say on the tin and this will be great for low T applications. But for high power generation we need something more like the oxides which are cheaper, easier to produce, and work at higher temperatures.
18. Re:heatsinks by serviscope_minor · 2012-09-19 22:40 · Score: 2
  
  The second law of thermodynamics states that you can't convert thermal energy into any other form. Sorry.
  Wow, this is one of the more bizarre claims on slashdot today.
  By the way, do you own a car with an internal combustion engine?
  
  --
  SJW n. One who posts facts.
19. Re:heatsinks by deroby · 2012-09-19 23:24 · Score: 2
  
  This is kinda interesting... Having read all above I think most of the confusion is in semantics, especially about the term 'heat'. Wikipedia describes it as " energy transferred from one system to another by thermal interaction" and that doesn't really make it easy to talk about it. So for my own mental sanity I'll allow myself to rather abuse the term 'heat-transfer' then which makes it easier to understand although at the same time I realize that it's akin to saying something like 'a fluid liquid' which sounds wrong too if you start thinking about it.
  Anyway, in order to satisfy my (very naive) curiosity : let's assume the following experiment :
  1) a 'small block' of copper is squeezed in between two equally sized vessels of water, one having a temperature of 10`C, the other 90`C.
  2) a 'small block' of the article-material is squeezed in between two equally sized vessels of water, one having a temperature of 10`C, the other 90`C.
  3) a 'small block' of the article-material is squeezed in between two equally sized vessels of water, one having a temperature of 10`C, the other 90`C and the 'wires are attached' resulting in a small lamp being powered in the next room.
  It seems fair to assume that situations 1 and 2 will both result in everything ending up at about 50`C assuming the 'small blocks' are really very small in relation to the vessels of water and hence have (virtually) no effect on the "calorimetric sum" of the entire setup. The main difference being that they probably will require a (very?) different time-span to reach equilibrium. I guess we have no issues there ?
  Likewise, it seems 'logical to me' that the energy required to light the lamp must come from 'somewhere' in situation 3. Hence, the end-state of the third setup then must end up with a lower total energy because some of it was piped away in the form of electricity. This leads me to assume that in the end, the system will end up in an equilibrium of somewhere in the upper forties degrees C at what time no electricity will be 'generated' any more.
  Given that in the last setup the 'cold' side ends up at a lower temperature than in the first two setup, I too 'feel' that less heat is transferred. However, from a point of view of the (initially) hot vessel in situation 3, actually MORE heat was transferred as the end situation is at a lower temperature than the other setups so more energy was drained from it.
  So both sides are correct : both less AND more heat was transferred =)
  Right ?
  
  --
  If there is one thing to be learned on slashdot, it has to be sarcasm.
20. Re:heatsinks by RaceProUK · 2012-09-19 23:35 · Score: 1
  
  The second law of thermodynamics states that you can't convert thermal energy into any other form. Sorry.
  So, power stations run on magic?
  
  --
  No colour or religion ever stopped the bullet from a gun
21. Re:heatsinks by scary_jeff · 2012-09-20 01:20 · Score: 1
  
  Don't forget that heat in a chimney is often not wasted energy. When burning fuel, you can lose more in the reduction in burner efficiency, caused the lack of draw that results from a cool chimney, than you gain from 'recovering' energy out of the chimney.
22. Re:heatsinks by jank1887 · 2012-09-20 01:24 · Score: 1
  
  "What is we ran the exhaust alongside some materials like this"
  you mean like this:
  http://www.gentherm.com/page/automotive-0
  http://phx.corporate-ir.net/phoenix.zhtml?c=107768&p=irol-newsArticle_print&ID=1326140&highlight=
  http://www.greencarcongress.com/2011/08/bmwthermal-20110830.html
  or this:
  http://www.serdp.org/Program-Areas/Energy-and-Water/Energy/Conservation-and-Efficiency/EW-1651
  http://www.navysbir.com/10_3/8.htm
  http://adsabs.harvard.edu/abs/2012SPIE.8377E..15S
  The problem is usually in actually getting that level of total conversion efficiency. By the time you take all of the efficiency chain fractions into account, you're far below the theoretical 15% (which only occurs at peak, steady conditions).
23. Re:heatsinks by jank1887 · 2012-09-20 01:25 · Score: 1
  
  I would love to know which laptop models are using this or similar heat recovery technology.
24. Re:heatsinks by jank1887 · 2012-09-20 01:26 · Score: 1
  
  because the 2nd law's a bitch. you lose in the end.
25. Re:heatsinks by Baloroth · 2012-09-20 02:10 · Score: 1
  
  Hmm, now that I google it looks like my memory may have been bad. I remember there was plans to do this on some laptops (ultrabooks specifically, I think), but looks like they never followed through. Or I just can't find them.
  
  --
  "None can love freedom heartily, but good men; the rest love not freedom, but license." --John Milton
26. Re:heatsinks by evilviper · 2012-09-20 03:21 · Score: 1
  
  Carnot's law applies to any generation of work from heat, period. If you can break Carnot's law, no matter with what sort of device, you can create a perpetual motion machine
  While I don't see anything technically incorrect in your post, I'd just like to point out that Carnot doesn't apply to photovoltaics.
  And PVs are very relevant both because they can operate on infrared (something which the unsophisticated would just call "heat"), and also because they have been eyed for quite some time as a replacement (or supplement) for TECs in RTGs and similar applications.
  
  --
  Slashdot gets worse every day... Pipedot: News for nerds, without the corporate slant
27. Re:heatsinks by strikethree · 2012-09-20 03:40 · Score: 1
  
  I suspect what they were getting at is using waste heat from the CPU (and GPU). So instead of calling this material a heat sink, you have it draw heat away from the heat sink. It would only be one source of heat draw so the heat sink will still be efficient at what it does... but, you recover some energy in the process.
  You could use the energy for cool lighting effects in the case or to help power a cooling solution (fan?), or just feed it back in to the power supply to reduce the draw at the wall outlet. *shrug* I dunno. Just running with it.
  
  --
  "Someone needs to talk to the tree of liberty about its ghoulish drinking problem." by ohnocitizen
28. Re:heatsinks by marcosdumay · 2012-09-20 05:45 · Score: 1
  
  Yes, it does apply to photovoltaics. Altough they can operate at the infrared, they can't turn into energy the emisions of a body at the same temperature that they are. And they lose efficiency when the gradient reduces, above what Carnot's law postulate as a minimum (in iother words, they are always worse than Carnot cycle).
  They'd be interesting at nuclear batteries because the origial radiation of a nuclear reaction has an extremely hight temperature. If you can deal with it without turning it into heat, you can achieve great efficiencies.
  
  --
  Rethinking email
29. Re:heatsinks by chilenexus · 2012-09-20 05:54 · Score: 1
  
  These devices need a difference in temperature, so in use they actually have heat sinks of their own on the cool end of them - they sit between a heat source and the heat sink, but I don't know that they'd conduct enough heat to the heat sink to be used on something like a processor. The use of thermoelectrics isn't new - much of the equipment the astronauts used on the moon were powered by RTGs, and the CIA lost some spy equipment in India that was spying on the Chinese back in '64 ( http://www.damninteresting.com/spies-on-the-roof-of-the-world/ ).
Very cool by multiben · 2012-09-19 10:46 · Score: 1

But what I can't tell FTA is whether or not the process of dis-ordering the material to prevent heat transfer also degrades the electrical conductivity. Obviously there is an over-all benefit, but I can't imagine that it is not affected at all.
1. Re:Very cool by mspohr · 2012-09-19 11:41 · Score: 1
  
  The article states that dis-ordering the material reduces heat transfer but not electrical conductivity. (They added some sodium to improve electrical conductivity.)
  
  --
  I don't read your sig. Why are you reading mine?
Re:Sounds Pretty Good Actually.. by rroman · 2012-09-19 11:09 · Score: 1

Well, I wouldn't agree that this material could be used in so many places to retrieve the used energy back. For example you might need to wrap it around the light bulb to get the energy back, but the material might not be transparent.
Re:What's the rationale of using it in Curiosity? by Githaron · 2012-09-19 11:10 · Score: 1

I am guessing they were trying to lower system dependencies. The more parts you have (especially moving parts) the more chances for failure.
Re:Hooray for global warming! by Githaron · 2012-09-19 11:12 · Score: 1

If maximizing heat trumps everything else, why not just push the planet into the Sun?
Efficiency in sensible units by johndoe42 · 2012-09-19 11:20 · Score: 4, Informative

TFA does a good job of using units that are incomprehensible to anyone who isn't an expert in thermoelectrics. But we can convert them...

Considering a thermoelectric device with a cold-side temperature of 350K and a hot-side temperature of 950K, respective waste-heat conversion efficiencies of ~16.5% and ~20% are predicted.
For a hot-side temperature of 950 K and a cold-side temperature of 350 K, the Carnot efficiency (i.e. the maximum possible efficiency of any device) is ~63%. So this is somewhere between 1/4 and 1/3 as efficient as it could possibly be. Large generators, such as combined cycle gas turbines are considerably more efficient, but these devices are small and silent. In other words: not bad.
1. Re:Efficiency in sensible units by locofungus · 2012-09-19 19:34 · Score: 1
  
  Yes they are!
  A Carnot engine is reversible.
  Tim.
  
  --
  God said, "div D = rho, div B = 0, curl E = -@B/@t, curl H = J + @D/@t," and there was light.
2. Re:Efficiency in sensible units by Thammuz · 2012-09-20 02:40 · Score: 1
  
  I'm afraid it does - here the electrons are your gas
Re:What's the rationale of using it in Curiosity? by hrvatska · 2012-09-19 11:24 · Score: 1

My guess would be that while the efficiency is low the reliability is extremely high, due to a lack of moving parts.
Re:Plutonium Power Source?! Sweet by sphealey · 2012-09-19 11:26 · Score: 3, Informative

Discovery in fact uses a radioisotope thermal generator (RTG) with plutonium as the power source. It used a substantial fraction of the Pu-238 available for space missions.
sPh
Niche applications by sphealey · 2012-09-19 11:29 · Score: 1

- - - - Such materials have found niche applications: - - - -

Niche applications: other than about 387 billion thermocouples measuring the temperature of everything around the globe.
sPh
1. Re:Niche applications by FunkDup · 2012-09-19 13:52 · Score: 1
  
  other than about 387 billion thermocouples
  You can't realistically generate electricity with a thermocouple. With this thing you can.
  
  --
  Great spirits have always encountered violent opposition from mediocre minds -- Albert Einstein
2. Re:Niche applications by blueg3 · 2012-09-19 14:52 · Score: 1
  
  Thermocouples are generally made out of non-novel materials because they don't need to be efficient. (In fact, any pair of dissimilar metals joined correctly will form a thermocouple, but some are better suited than others.)
3. Re:Niche applications by EmagGeek · 2012-09-19 23:20 · Score: 1
  
  Thermocouples are not that common. Much more common are simple diodes.
Re:What's the rationale of using it in Curiosity? by Formalin · 2012-09-19 11:59 · Score: 1

They're talking about the thermocouples inside the RTG power source, I presume... 15% is shitty, but it's still 'free' power. Beats the alternatives of batteries, unwieldy solar panels, etc.
MMRTG
Temperature != Heat by mosb1000 · 2012-09-19 12:05 · Score: 1

Heat is the transfer of energy. It is not the the energy itself.
1. Re:Temperature != Heat by mosb1000 · 2012-09-19 16:15 · Score: 1
  
  In physics, "heat" is by definition a transfer of energy and is always associated with a process of some kind.
Solar Cells by mosb1000 · 2012-09-19 12:09 · Score: 1

If the cost is low enough, you could use this to replace conventional solar cells. Just place a thermocouple between two pieces of metal (paint the top one black). The top one will get hot and the bottom one would be shaded and air cooled. Instant solar cell. You wouldn't need to worry about keeping it clean or directing it toward the sun or anything like that.
1. Re:Solar Cells by __aaltlg1547 · 2012-09-19 13:15 · Score: 1
  
  Hard to get the hot side hot enough and to keep the cool side cool enough.
2. Re:Solar Cells by Anonymous Coward · 2012-09-19 14:02 · Score: 1
  
  Hard to get the hot side hot enough and to keep the cool side cool enough.
  Duh, you just set up a heater to heat the hot side and an air conditioner to cool the cold side.
3. Re:Solar Cells by Belial6 · 2012-09-19 15:26 · Score: 1
  
  Put the cool side on the North facing side of the roof, and the hot side inside the attic. Even in a properly ventilated attic, it is almost always noticeably hotter in the attic than outside. The only question would be whether it was cost effective.
4. Re:Solar Cells by rrohbeck · 2012-09-19 15:27 · Score: 1
  
  The efficiency is way lower than PV right now.
  But you can stick one on the back side of a solar panel with a heat sink. Those solar cells get quite hot in full sun.
  If it would be cost effective is another question of course.
  
  --
  thegodmovie.com - watch it
5. Re:Solar Cells by __aaltlg1547 · 2012-09-20 13:57 · Score: 1
  
  It takes a large temperature difference and a high heat flow to generate much electricity this way.
Re:What's the rationale of using it in Curiosity? by jadrie · 2012-09-19 12:17 · Score: 1

Not to mention that waste heat that doesn't get turned to electricity still gets used - by pumping it along the rovers extremities to help keep the temperature more tolerable for the equipment.
Better Options? by Dereck1701 · 2012-09-19 13:39 · Score: 1

I think even the simplest Stirling engines beat this thing out for efficiency, I think 30% is easily attainable and better engineered systems I believe can top 45%. The only issue with them is there is some maintenance (though NASA is working on eliminating that). I think the next generation of Radioisotope thermoelectric generators are supposed to use Stirling generators.
Re:Plutonium Power Source?! Sweet by FunkDup · 2012-09-19 13:41 · Score: 1

Did you mean

Curiosity in fact uses a radioisotope thermal generator...

--
Great spirits have always encountered violent opposition from mediocre minds -- Albert Einstein
Re:Temperature by mosb1000 · 2012-09-19 16:21 · Score: 1

No, it isn't. Heat is a transfer of energy. Read the Wikipedia article if you don't believe me.
Photovoltaic and thermoelectric combined by advid.net · 2012-09-19 21:06 · Score: 1

There's an on going thesis on this : Association of thermoelectric and photoelectric effects to improve the performance of photovoltaic
Terraforming by jimshatt · 2012-09-19 21:06 · Score: 1

Let's start terraforming the sahara desert! We just need some of that water of the melting ice caps and we can get going. We'll use the energy of these heat-to-electricy-thingies to pump melted arctic water to the desert. And while we're melting the polar caps we might as well do some terraforming over there (south pole and greenland). It's gonna be great guys!
Didn't break any records by EmagGeek · 2012-09-19 23:18 · Score: 1

Diesel-electric generators are far more efficient than 15% at converting heat into electricity.
America's Lament by ThatsNotPudding · 2012-09-19 23:51 · Score: 1

They had this in the McDLT*, and they threw it away! The fools!

* - "It keeps the hot side hot and the cold side cold!"
Sterling engines are a far better choice by evilviper · 2012-09-20 03:04 · Score: 1

NASA hasn't been pursuing better RTG materials, instead they've been developing Sterling engines to replace the Peltiers.
The future of RTGs is in Advanced Stirling Radioisotope Generators (ASRGs):
https://en.wikipedia.org/wiki/Advanced_Stirling_Radioisotope_Generator
See the "Proposals" section for a number of missions which planned (or currently do plan) to include them. With better luck, we could well have had them in current space-craft. Instead, it's one of those "any day now..." things. But once they are proven, I'd expect ASRGs to become the standard. The efficiency is just so much better, requiring less than a quarter as much radio-isotope fuel, and significantly reducing size and cost as a result.

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reverse heatsink by DarthVain · 2012-09-20 04:04 · Score: 1

Would this function sort of like a reverse peltier once used for cooling on CPU back in the day? So more like a reverse heatsink.
With a peltier, you actually applied current, and the current would produce heat on one side of the peltier (to be dispersed using a fan), whilst the other side would become cool, lowering the tempature of the CPU in question.
Here it would seem to work in reverse with these materials, whereby heat is applied to the material, and as a result of the poor heat conduction, an electical current is generated?
It is too bad the efficiency is so low, I can see many poissibilities for such a device simply using waste heat of various objects.
Re:Temperature by mosb1000 · 2012-09-20 10:01 · Score: 1

No, a energy transfer can be measured in joules. Take heat of combustion for example. It is usually measured in J/mol or J/kg. You couldn't possibly measure it in watts because you have no idea how long combustion takes to occur. Nevertheless it is a transfer of energy:

The heat of combustion is the energy released as heat when a compound undergoes complete combustion with oxygen under standard conditions.
In reality, this argument is not really about whatever common definitions physicists use. It is a philosophical one. There is little reason to consider how much energy may exist in a system unless such energy is available to use. That being true, any meaningful use of the term "heat" will refer to it in the context of transferring it from one body to another, so there is little reason to define heat in any other context.
As a chemical engineer, I find your claim that most physicists use your definition appalling, given the amount of training in thermodynamics you must have had. In any case, all the authoritative sources I've consulted have agreed with my definition.
Re:Plutonium Power Source?! Sweet by LifesABeach · 2012-09-22 08:59 · Score: 1

How much shielding is required for a RTG unit? How heavy is it? Not having to go to the gas station for 10 years could be worth something.

Just a thought, we could test this idea out using TSA staffers, they seem not to be to concerned about Fukushima Syndrome.