Breakthrough in converting heat waste to electricity

Jan 18, 2011 By Erin White

(PhysOrg.com) -- Researchers at Northwestern University have placed nanocrystals of rock salt into lead telluride, creating a material that can harness electricity from heat-generating items such as vehicle exhaust systems, industrial processes and equipment and sun light more efficiently than scientists have seen in the past.

The material exhibits a high thermoelectric figure of merit that is expected to enable 14 percent of heat waste to , a scientific first. Chemists, physicists and material scientists at Northwestern collaborated to develop the material. The results of the study are published by the journal Nature Chemistry.

"It has been known for 100 years that semiconductors have this property that can harness electricity," said Mercouri Kanatzidis, the Charles E. and Emma H. Morrison Professor of Chemistry in The Weinberg College of Arts and Sciences. "To make this an efficient process, all you need is the right material, and we have found a recipe or system to make this material."

Kanatzidis, co-author of the study, and his team dispersed nanocrystals of rock salt (SrTe) into the material lead telluride (PbTe). Past attempts at this kind of nanoscale inclusion in bulk material have improved the energy conversion efficiency of lead telluride, but the nano inclusions also increased the scattering of electrons, which reduced overall conductivity. In this study, the Northwestern team offers the first example of using in lead telluride to reduce electron scattering and increase the of the material.

"We can put this material inside of an inexpensive device with a few electrical wires and attach it to something like a light bulb," said Vinayak Dravid, professor of science and engineering at Northwestern's McCormick School of Engineering and Applied Science and co-author of the paper. "The device can make the light bulb more efficient by taking the heat it generates and converting part of the heat, 10 to 15 percent, into a more useful energy like electricity."

The automotive, chemical, brick, glass and any industry that uses heat to make products could make their system more efficient with the use of this scientific breakthrough, said Kanatzidis, who also has a joint appointment at the Argonne National Laboratory.

"The energy crisis and the environment are two major reasons to be excited about this discovery, but this could just be the beginning," Dravid said. "These types of structures may have other implications in the scientific community that we haven't thought of yet, in areas such as mechanical behavior and improving strength or toughness. Hopefully others will pick up this system and use it."

Explore further: A new approach to creating organic zeolites

More information: The title of the paper is “Strained endotaxial nanostructures with high thermoelectric figure of merit.” Paper online: www.nature.com/nchem/journal/v… /full/nchem.955.html

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User comments : 18

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Eikka
3.1 / 5 (10) Jan 18, 2011
14% over what temperature difference?

Why? Why can't they state that clearly? You obviously can't pull 14% of electricity from a cup of hot coffee, because it's simply not hot enough. Such a device would have to be theoretically perfect.

And that is the problem of waste heat recovery. How are you going to capture the waste heat of a lightbulb for example, without blocking the light or diluting the heat into so much matter that it's simply too cool to be used?
Occupodies
2.8 / 5 (4) Jan 18, 2011
Well buddy, this is what you call a FAIL article. Not only is this idea old, but people have been working with lead telluride systems for the last 10 years. Now, to answer your question the point of what they're talking about is the maximum ZT figure of merit, which i think in lead telluride system... huh 600k or higher? I can't remember. Anyways, the article also fails to mention that the 14% is with small scale systems, not with bulk material. Overall, this article shouldn't have even been posted considering it's not a breakthrough.
jselin
not rated yet Jan 18, 2011
The interfaces between the two phases provide interfacial or kapitza resistance to the flow of heat. Minimizing direct heat conduction across the device is part of the equation for the figure of merit. The name of the game is reducing phonon transport while encouraging charge carier transport.

Occupodies - Does the literature on lead telleride systems include this sort of nanocompositing to tailor properties? I believe that is what is being reported. I once sat in on someone presenting their work on this sort of thing but I don't recall what materials they were using.
Caliban
1 / 5 (1) Jan 18, 2011
Not to mention the toxicity of the materials themselves. Brilliant idea to be painting hot, usually vibrating objects/machines/assemblies with lead compounds dosed with Strontium and Tellerium.

That is a recipe for airborn metal poisoning if ever there was one. Really, what are these imbeciles thinking? Could it be the much sought after "Quick Buck"?

Dug
5 / 5 (2) Jan 18, 2011
Physorg needs either a more editors - or at least some more competent ones, because way too many of their articles are more PR releases than quality info.
ubavontuba
1 / 5 (1) Jan 19, 2011
There already are more efficient ways to capture heat energy. You could easily miniaturize some fancy things like Heat recovery steam generators...

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

Or, you could do like my buddies do when they're out 4-wheelin' and wrap some hot dogs (or whatever) up in foil and place them against the exhaust manifold, drive around a while and voila! Off-Road Racer's Delight! It cooks as you drive, so it's ready when you get there! Mmm-MMM! Delicious!

In the olden days, boiler operators used to do stuff like this all the time. They even depicted it in the movie "Titanic."
bugmenot23
5 / 5 (2) Jan 19, 2011
For a detailed article, with info on the temp range etc.

nextbigfuture.com/2011/01/nanocrystals-of-rock-salt-into-lead.html
Jim1138
5 / 5 (2) Jan 19, 2011
rock salt is Strontium Telluride? No wonder my I have garlic breath.
HaveYouConsidered
3 / 5 (2) Jan 19, 2011
There needs to be a $10,000 fee for each use of the word "breakthrough" by any university researcher or their PR department. These stories are always full of hype and ignorance about barriers to commercialization and eventual, usually disappointing, product performance. The real story: "we need funding".
Ricochet
3 / 5 (2) Jan 19, 2011
At this rate, Physorg would need to make sure that all their editors and staff had PHDs in their respective fields. Give them a break, ppl.
Caliban
5 / 5 (1) Jan 20, 2011
At this rate, Physorg would need to make sure that all their editors and staff had PHDs in their respective fields. Give them a break, ppl.


Agreed.
But how else will they become aware of their editorial shortcomings? I don't know about you, but plenty of my comments have been removed by virtue of my usage of "excess verbiage", so it seems fair enough to me that we complain of a stench when it smells, yes?

Occupodies
not rated yet Jan 20, 2011
The interfaces between the two phases provide interfacial or kapitza resistance to the flow of heat. Minimizing direct heat conduction across the device is part of the equation for the figure of merit. The name of the game is reducing phonon transport while encouraging charge carier transport.

Occupodies - Does the literature on lead telleride systems include this sort of nanocompositing to tailor properties? I believe that is what is being reported. I once sat in on someone presenting their work on this sort of thing but I don't recall what materials they were using.


Yes there has been plenty of work done creating nano composites inside of thermoelectric materials, lead telluride being one of the bigger ones b/c the materials are relatively cheap comparatively and there's also bismuth telluride, silver telluride, and other calcogenides.
Occupodies
not rated yet Jan 20, 2011
There already are more efficient ways to capture heat energy. You could easily miniaturize some fancy things like Heat recovery steam generators...

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

Or, you could do like my buddies do when they're out 4-wheelin' and wrap some hot dogs (or whatever) up in foil and place them against the exhaust manifold, drive around a while and voila! Off-Road Racer's Delight! It cooks as you drive, so it's ready when you get there! Mmm-MMM! Delicious!

In the olden days, boiler operators used to do stuff like this all the time. They even depicted it in the movie "Titanic."


I think you fail to see the size and viability of thermoelectric materials which makes them of key importance to improve.
ubavontuba
2.3 / 5 (3) Jan 20, 2011
I think you fail to see the size and viability of thermoelectric materials which makes them of key importance to improve.
Naw, I was just making fun.

I'm sure they'd have all sorts of interesting applications if they could be made of safe and environmentally friendly materials.

In the meantime, regenerative technologies will have to suffice.
jselin
1 / 5 (1) Jan 21, 2011
I'm sure they'd have all sorts of interesting applications if they could be made of safe and environmentally friendly materials.

In the meantime, regenerative technologies will have to suffice.


As a materials scientist, I find this kind of focus on toxicity silly and frustrating. Everything is toxic in its own way and functional materials are extremely hard to develop even when you have the full periodic table to work with. When you cross off 90+% and say no, thats poisonous, you're really doing everyone a disservice by stalling progress. It should just be a rule of thumb to avoid eating thermoelectric devices or disposing of them in drinking water reserviors.
ubavontuba
2.3 / 5 (3) Jan 22, 2011
As a materials scientist, I find this kind of focus on toxicity silly and frustrating. Everything is toxic in its own way and functional materials are extremely hard to develop even when you have the full periodic table to work with. When you cross off 90+% and say no, thats poisonous, you're really doing everyone a disservice by stalling progress. It should just be a rule of thumb to avoid eating thermoelectric devices or disposing of them in drinking water reserviors.
The problem with that position is it's too often the case where those doing the disposing are less ethical than we would desire.

And, decrepitation of these substances through normal use, can lead to widespread environmental contamination.

But I'm not saying the technology shouldn't be pursued. It just need to be carefully pursued.

And hopefully (with progress), the benefits will eventually far outweigh the consequences.
Occupodies
1 / 5 (1) Jan 22, 2011

The materials aren't even really toxic by the time you're done mixing in tellurium and whatever other composites you want to dope in, including nano composites, though the excess from the mixtures (if made in bulk) would obviously be toxic, but there are several lead devices already out, such as fricken car batteries that are much more toxic.
Caliban
not rated yet Jan 22, 2011

The materials aren't even really toxic by the time you're done mixing in tellurium and whatever other composites you want to dope in, including nano composites, though the excess from the mixtures (if made in bulk) would obviously be toxic, but there are several lead devices already out, such as fricken car batteries that are much more toxic.


Somewhat true.

What you are failing to take into account is the likely SCALE of deployment of this tech, if it takes off, which would be massive, as virtually any powered device or power generating device would be equuipped with it.

In other words, just about everything, just about everywhere. Toxicity would not be confined to the life cycle end.