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Professor Mercouri Kanatzidis holds up his device that can harvest 14 percent of waste heat as usable electricity.  (Source: Northwestern University)
New lead-based compound could see a variety of scenarios -- including helping power the machines in the absence of sunlight

A new material from researchers at Northwestern University could offer a way to capture and recycle waste heat better than ever before [press release].  The material can convert a record 14 percent of the waste heat passing through it to usable electric energy.

When manmade devices perform work, be it a computer or a car, they produce heat.  That heat is ultimately lost, reducing the energy efficiency of our devices.  Some have cleverly exploited this fact, using waste heat to offer desirable comfort heating.  But ultimately, the only good solution is to try to somehow recapture that heat in a usable form.  To do that, the right material was necessary.

Semiconductors have long been considered a promising candidate, as they can produce electricity when heated.  Lead telluride (composed of lead and tellurium ions on a lattice) was considered one of the most promising candidates, as it was relatively efficient in accomplishing the heat to electricity transformation.  

But attempts to improve that efficiency via various techniques, such as nano-inclusions resulted in an undesirable side effect -- increased scattering of electrons, reducing overall conductivity.  Obviously, if you're converting heat to electricity, you have to funnel it out of the device, so this was unacceptable.

The NU team, lead by Chemistry professor Mercouri Kanatzidis discovered that by using a special type of nano-inclusion, the scattering could actually be reduced.  The trick was to use special crystals of rock salt (SrTe).  Professor Kanatzidis sums up, "It has been known for 100 years that semiconductors have this property that can harness electricity. 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."

Materials Science professor Vinayak Dravid also assisted in the study.  He describes the results, stating, "We can put this material inside of an inexpensive device with a few electrical wires and attach it to something like a light bulb. 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 study on the promising material earned a place [abstract] in the prestigious peer-reviewed journal Nature Chemistry.

So the material seems great, but what about its commercialization prospects?

Well, lead telluride is relatively rare , but occurs naturally in mountain deposits as the mineral Altaite.  Significant deposits have been found in the Altai mountains of northeast Asia;  Zyrianovsk, Kazakhstan; the Ritchie Creek Deposit in Price County, Wisconsin; the Koch-Bulak gold deposit in Kazakhstan; Moctezuma, Mexico; and Coquimbo, Chile.

Given that air or liquid bearing waste heat can be channeled through a relatively small area, a little telluride (say in a heatpipe on a computer component) could go a long ways, recycling almost a sixth of the wasted energy.

Strontium is very abundant, so coming up with sufficient quantities of the nano-inclusion material shouldn't be as big an issue.

Aside from making existing devices more efficient, the material could be used to make new low voltage electronic devices, powered by waste heat from the human body.

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By chang3d on 1/19/2011 8:15:02 PM , Rating: 2
my cpu from a couple of years ago could provide power to its cpu fan! too bad that my new cpu runs cool and is capable of passive cooling.

my servers, on the other hand, could use this!

RE: cpu
By Stoanhart on 1/19/2011 8:26:19 PM , Rating: 3
The neat thing is that the fans would automatically speed up as load increases.

RE: cpu
By RamarC on 1/19/2011 8:48:15 PM , Rating: 2
my 3.2ghz p4 turned my PC into a space heater! in the winter months, i didn't even need to turn on the heat when i worked from home (florida) but during the summer, omg was that room hot!

RE: cpu
By superPC on 1/19/2011 9:18:42 PM , Rating: 2
CPU? hell this can help in everything. solar panels (the back of it get quite hot. slap a few of this material and we get 14% of that heat for electricity. since solar panel only has about 20-30% efficiency the additional energy from this material can help boost it. how about insulator? your boiler and pipe can be lined up with this thing and generate electricity from the escaped heat. put it in a hybrid car engine and heat from the ICE can help recharge the battery and the electric motor can be use more often.

RE: cpu
By FaaR on 1/19/2011 9:35:35 PM , Rating: 3
Most likely this process requires a significant temperature differential to generate electricity - IE, you couldn't just stick it to a hot surface and expect to get free electrical current. So you probably don't want to line your hot water pipes with this stuff, as that would lead to heat leakage and a loss of energy (the compound is only 14% efficient, remember?)

It'd be better used where you WANT to get rid of the heat, like in series with a heat exchanger for example, but not neccessarily on hot ICs, as introducing an extra layer of unknown thickness across the IC would reduce the cooling capability of the chip. This stuff doesn't neccessarily transfer heat all that well, so it wouldn't make sense to cook our CPUs just to produce a few watts of electricity.

RE: cpu
By superPC on 1/19/2011 11:07:48 PM , Rating: 3
thermoelectric effect is described in here: as you can see it all depend on S = delta T / delta V. since all thermoelectric generator before this has an efficiency of less than 10% ( ) that means a low S value. this though must have a higher S value so it can achieve a higher efficiency. therefore it needs less temperature difference (delta T) to generate the same amount of power. even with less than 10% efficiency they manage to generate 255 watt from an ICE engine ( ). so maybe lining pipes (since this thing is such a good heat isolator) and boiler heatsinks with this thing is not such a bad idea after all.

RE: cpu
By FITCamaro on 1/20/2011 10:57:53 AM , Rating: 2
Solar panels have at BEST 20-30%. Most of the panels you get at home are a lot less than that.

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