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
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
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.