Researchers at the University of Michigan are taking a step towards more efficient recycling of waste heat into energy by using skutterudites in their new thermoelectric device experiments.

Skutterudite. From Wikipedia. Click image for the largest image.

The UM press release explains with an offering from Massoud Kaviany, professor in the Department of Mechanical Engineering, “Today’s state-of-the-art thermoelectric materials are only five percent efficient. Skutterudites, and the new knowledge about how best to arrange their atoms, could help improve their performance to 15 to 20 percent, at which point they become useful in many practical applications.”

The UM researchers studied skutterudites, a class of mechanically strong thermoelectric materials that, when combined with certain elements such as the metal barium, has the right mix of properties to effectively make the projected energy conversion: The material conducts electricity well, and conducts heat poorly. The researchers identified certain configurations of the atoms in the compound that drastically increase the materials’ efficiency.

That suggests a properly designed material wrapped around your car’s exhaust system could one day scavenge heat that would otherwise be wasted, turning it into energy to warm the cabin or recharge the battery.  The UM engineers and have taken a major step toward improving the efficiency of a promising candidate for recapturing a huge energy resource.

The research paper has been published in the current edition of Physical Review Letters titled “Structural Order-Disorder Transitions and Phonon Conductivity of Partially Filled Skutterudites.”

Ctirad Uher, professor in the Department of Physics at UM explains the main point of the paper, “We knew that skutterudites are promising materials. But we did not know what features we could manipulate to maximize the conversion of heat into electricity. In this paper, we propose that certain configurations of the filler element barium will be very effective in lowering the materials’ thermal conductivity and thus increasing their conversion efficiency. This is an important advancement in the sense that it provides guidance for the experimentalists to focus as they try to synthesize highly efficient thermoelectric materials.”

Kaviany adds, “We explained the physics of these materials for the first time. This will help to advance the development of these materials. If you are designing them based on fundamental physics and materials and not just by trial and error, then you need to know how they work so you can avoid haphazard experimentation.”  For lots of researchers as well as developers this is important, time saving and cost reducing work.

The UM press release quoting Uher also points out automobile manufacturers are extremely interested in this technology. The ideal environments for these materials are locations where large differences in temperatures exist. One such place is the exhaust pipe system of a car between the motor and the catalytic converter.  “That’s a big source of heat that you paid for already,” Uher said.

Not quoted yet contributing to the research is Anton van der Ven, an assistant professor in the Department of Materials Science and Engineering.

The funding for the research making the information available for everyone came from the University of Michigan’s Center for Solar and Thermal Energy Conversion, which is funded by the U.S. Department of Energy’s Office of Basic Energy Sciences.  Not every tax dollar is wasted it seems.

It very hard to get a handle on the amount of energy just lost as heat. On a cold day looking out over a electrical generation plant, especially one using combustion fuel one can see the great cloud of condensed water vapor radiating energy into the atmosphere and out into space.  It’s enough to make a physicist cringe.  The losses go on continuously, world wide, at great loss.

Gaining back even 20% seems delightful.  Even combined heat and power plants should be able to recover more for higher efficiencies.  Perhaps heat cycling can double up the 20% to 40%.  So much is lost that the bait is entrancing.  This is work worth doing, and doing quickly.  And maybe the 20% estimate can be made to be higher with further work.


8 Comments so far

  1. Musson on January 21, 2011 11:50 AM

    If you could gain enough electricy to forego an alternator/generator – efficiency would go up significantly.

  2. Uncle B on September 20, 2011 3:43 PM

    Astoundingly poor engineering practices where energy conservation is concerned in U.S. alarm scientists around the world! Over half an American reactor’s energy potential goes up the cooling towers, is wasted in low demand periods at night! Only Americans can justify this astounding sloth, nowhere else on earth are people so well off as to squander this and resource flows such as sewage, going to contaminate the waterways of their own country! Now in these harder times, and times of repentance to follow, will the great wasteful whore to all mankind change her ways or die in her own filth, nuclear wastes included?

  3. Uncle B on September 20, 2011 4:01 PM

    A Euro-styled Turbo Diesel is a full 40% more efficient (by the laws of thermodynamics, higher compression, gas rules – you Google you see!) than an American styled, low compression gasoline/alcohol engine, and therefore creates a full 40% less pollution from the get-go! P.S. Diesels can burn propane, methane, natural gas, L.P. Gas waste oil from restaurants too! Sadly rejected by the brainwashed American people, easily influenced by Scientists bought out by research grants and other coercion methods, writing papers that favor the large oil and Corporate interests to save their own behinds, get jobs, grants -These same bunch of ‘guys’ now show you how to save up to 20% heat energy lost! Imagine the efficiency boost this would give a Diesel/hybrid had they not lied them out of reach for the American people years ago! Just think: a Prius on Diesel steroids with even 20% engine/exhaust heat recovered. Build the body from light weigh Canadian hemp to make it even lighter more economical and rust proof too! Big Oil going to let you have these remarkable technologies? Dream on Yankee Doodle! Cynical am I? Google, torrent, the documentary, “Who Stole The Electric Car” you judge! Who was shafted here?

  4. Loreak on September 20, 2011 5:58 PM

    Uncle B, that was the best rant ever. But seriously you are pretty dumb.

  5. GreyGeek on September 21, 2011 11:41 AM

    The maximum thermodynamic efficiency of a heat engine operating between 450F and 100F is slightly less than 39%. The article doesn’t say if that “15-20%” improvement in performance is half of the maximum or only 1/5th of it. If the latter it would hardly be worth the expense, since solar panels built into the car could do better and wouldn’t require engine heat.

    Uncle B’s comments, while provocatively written in the style and terms of a religious fanatic, are pretty much spot on. His rant can be summarized by saying that corporate (multi-national, not just in America) concerns go no farther than the maximum short term privatized profit, while they bribe (a.k.a “campaign contributions”) Congress for legislation to socialize the losses and costs, that is, make them burdens of the taxpayers.

  6. Uncle B on September 21, 2011 11:42 AM

    Dumb as stone! Lots of questions – still no answers! Educate me, correct me, show me where my fears are unfounded, help,me feel better in these times of great sadness, these times of dissillusionment, these times of great sorrow for my people! We no longer have Oldsmobile’s, Packard’s, Hudson’s, Desoto’s, Pontiac’s, Nash, Studebaker’s, Mercury’s, Kaisers, Monarchs, Edsel’s, Corvair’s, Vega’s? After all these years of faith in these American brands we are crammed into Hyundai, Honda, Toyota, and the like. WTF?

  7. Uncle B on September 21, 2011 11:53 AM

    Uncle B drove a 1985 Jetta diesel at a time when diesel fuel sold for half the price of premium gasoline. The Jetta returned an astounding 42 mpg, calculated over 400,000. miles of driving. The engine is reported to still be running daily. My gasoline Ford Pinto returned a paultry 20 mpg over the 100,000. mile engine life. Re-work your mileage figures, Europeans report as I do, very high efficiencies for VW diesels, especially TDI diesels – Wrong? Possibly, please show me again, Why? For me the diesel engines performed faultlessly from – 40 degrees to the hottest days, rarely needed any attention from mechanics,and were much cheaper to run overall.

  8. David B. Benson on September 24, 2011 8:46 PM

    At the bottom end of the Rankine cycle the steam must be condensed back into water for pumping purposes. This means the heat of vaporization has to be removed, via the condenser. If a thermoelectric device could remove just 10% of that heat not only would some electricity be generated by the condensing system would be reduced in size for lower capital cost but also lower operating expense.

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