A key material to convert heat into electrical energy

[Axil]

http://nanopatentsandinnovations.blogsp ... le-of.html

Breakthrough Reveals Another Example Of The Strategic Importance Of Rare-Earth Elements

Automobiles, military vehicles, even large-scale power generating facilities may someday operate far more efficiently thanks to a new alloy developed at the U.S. Department of Energy’s Ames Laboratory. A team of researchers at the Lab that is jointly funded by the DOE Office of Basic Energy Sciences, Division of Materials Sciences and Engineering and the Defense Advanced Research Projects Agency, achieved a 25 percent improvement in the ability of a key material to convert heat into electrical energy.

[Giorgio]

Unfortunately the article does not mention the starting efficiency or the ZT figure of merit so is difficult to understand if it is something that might have some real world application or just material useful for research use.

TAGS 85 is a first generation thermoelectric material that can be manufactured in a broad range of efficiencies.
It was used in the famous SNAP19 generators, the one that gave power to the Nimbus, Pioneer and Viking satellites. Those generators had a conversion efficiency of around 6.5% at 500 C.

Overall the research looks interesting, but it cannot be evaluated unless the starting or ending ZT (or the efficiency) is disclosed.

If someone has a link to the paper I'll love to read it.

[qraal]

Unfortunately the article does not mention the starting efficiency or the ZT figure of merit so is difficult to understand if it is something that might have some real world application or just material useful for research use.

TAGS 85 is a first generation thermoelectric material that can be manufactured in a broad range of efficiencies.
It was used in the famous SNAP19 generators, the one that gave power to the Nimbus, Pioneer and Viking satellites. Those generators had a conversion efficiency of around 6.5% at 500 C.

Overall the research looks interesting, but it cannot be evaluated unless the starting or ending ZT (or the efficiency) is disclosed.

If someone has a link to the paper I'll love to read it.

Next best thing - a write up at Next Big Future

[Giorgio]

Uhm, I highly doubt that they got to a ZT of 1.85 with TAGS-85 as NextBigFuture is stating.

As I said before TAGS85 comes in a variety of different compounds with different efficiencies values. Applying modifications that increase ZT to a certain compound does not necessary mean that the same modifications will have the same effect on a different TAGS85 compounds.

Now I am even more eager to read that paper

[Giorgio]

After some googling I found the lab that manufactured the compounds used in the tests, and they show the experiment results on the website:
http://www.ameslab.gov/dmse/highlight/t ... -materials

Using that picture as a reference we can quickly calculate ZT.

We have for reference TAGS85 at 700K a ZT of around 0,85
We have for the doped TAGS85 at 700K a ZT of around 1,05

We will see if their doping technique will be able to increase the ZT value of other TAGS85 compounds, but for now is not really something so exciting.

My preferred candidates for a bulk material with a ZT>10 are still skutterudites and zinc antimonides.


Edited to add:
For the one who are interested into this field I suggest also to give a look to the field of nanoscale patterning that is very promising:
http://www.rti.org/page.cfm?objectid=5A ... 2FD#energy

Especially patterning of bismuth telluride (Bi2Te3) has given excellent results with reported ZT figures of 2,4 and conversion efficiencies of 20%.
Still too little literature to understand exactly what's going on, but looks promising.

[Nik]

Uh, presumably the idea is to put thermo-electric material up-stream of the hot loop cooling system to 'skim the cream' of the available power.

I doubt the material would benefit from the radiation flux which, IIRC, is several orders of magnitude higher than the space missions' systems.

[morganism]

Actually the UofAz cats just found that by chaining together regular benzene atoms in an offset pattern, they could convert heat directly to a current.

The electrons racing down the chain arrive at each junction at a different time, creating a current. Patent in the works.

Saying a paintable/printable formula by next year. Planning on coating resistors with it, putting it under LED's, and painting exhaust systems with it too. A "string" version for inserting into boards via's will be coming also.
Just have to have a metalic surface on the top/bottom for conduction of current. Mylar will prob work.

Going to be HUGE for spacecraft systems. No more radiators required, and no transfer systems or fluids. Going to be sweet on solar thermal collectors and thorium systems will be even simpler.

Some interesting side bars to this too......

[hanelyp]

No more radiators required

That breaks known laws of thermodynamics, which are way up there on the confidence scale. To produce high grade energy like electricity from heat you need a cold side.

[KitemanSA]

Actually the UofAz cats just found that by chaining together regular benzene atoms in an offset pattern, they could convert heat directly to a current....
Going to be HUGE for spacecraft systems. No more radiators required, ...

Please remember that in thermodynamics, "HEAT" is the FLOW of thermal energy. Such flow requires a hot side and a cold side. The cold side requires a radiator.

[ladajo]

Here we go again.

[D Tibbets]

Actually the UofAz cats just found that by chaining together regular benzene atoms in an offset pattern, they could convert heat directly to a current....
Going to be HUGE for spacecraft systems. No more radiators required, ...

Please remember that in thermodynamics, "HEAT" is the FLOW of thermal energy. Such flow requires a hot side and a cold side. The cold side requires a radiator.

I'm not sure there is not wiggle room. If the local heat is transformed locally into electricity and conducted away, at least locally the idea of a cold side may be represented by the power of the resultant electricity (I may be ignoring what drives the thermocouple- the thermal gradient). If this probably flawed reasoning holds, then the question becomes what you do with the energy in the electrical current. You have to get rid of this somehow- doing work with resultant generation of heat, or dumping electrons and ions off of the space craft (ion engine). To say radiators are not needed is probably wrong. Saying much smaller radiators are needed is probably right, either because of my above unrealistic reasoning, or more acurately by saying you need less heat to generate the same amount of work. It is not that you are saying that you are reducing the cooling concerns per unit heat output of your heat source, but that the heat source itself can be proportionately smaller and thus less of a load on the cooling system.

Dan Tibbets

[morganism]

Exactlly.
Can convert to more horsepower, or other work in communications, and if too much still, could pump a laser and send it off into the dark.

[Giorgio]

Here we go again.

You took the words out of my mouth