More than 60% of the energy produced by cars, machines, and
industry around the world is lost as waste heat—an age-old problem—but
researchers have found a new way to make “thermoelectric” materials for use in
technology that could potentially save vast amounts of energy.
And it’s based on a device found everywhere from kitchens to
dorm rooms: a microwave oven.
Chemists at Oregon
State University
have discovered that simple microwave energy can be used to make a very
promising group of compounds called “skutterudites,” and lead to greatly
improved methods of capturing wasted heat and turning it into useful
electricity.
A tedious, complex, and costly process to produce these
materials that used to take three or four days can now be done in two minutes.
Most people are aware you’re not supposed to put metal foil
into a microwave, because it will spark. But powdered metals are different, and
OSU scientists are tapping into that basic phenomenon to heat materials to
1,800 degrees in just a few minutes—on purpose, and with hugely useful results.
These findings, published in Materials Research Bulletin, should speed research and ultimately
provide a more commercially-useful, low-cost path to a future of thermoelectric
energy.
“This is really quite fascinating,” says Mas Subramanian,
the Milton Harris Professor of Materials Science at OSU. “It’s the first time
we’ve ever used microwave technology to produce this class of materials.”
Thermoelectric power generation, researchers say, is a way
to produce electricity from waste heat—something as basic as the hot exhaust
from an automobile, or the wasted heat given off by a whirring machine. It’s
been known of for decades but never really used other than in niche
applications, because it’s too inefficient, costly, and sometimes the materials
needed are toxic. NASA has used some expensive and high-tech thermoelectric
generators to produce electricity in outer space.
The problem of wasted energy is huge. A car, for instance,
wastes about two-thirds of the energy it produces. Factories, machines, and
power plants discard enormous amounts of energy.
But the potential is also huge. A hybrid automobile that has
both gasoline and electric engines, for instance, would be ideal to take
advantage of thermoelectric generation to increase its efficiency. Heat that is
now being wasted in the exhaust or vented by the radiator could instead be used
to help power the car. Factories could become much more energy efficient,
electric utilities could recapture energy from heat that’s now going up a
smokestack. Minor applications might even include a wrist watch operated by
body heat.
“To address this, we need materials that are low cost,
non-toxic and stable, and highly efficient at converting low-grade waste heat
into electricity,” Subramanian says. “In material science, that’s almost like
being a glass and a metal at the same time. It just isn’t easy. Because of
these obstacles almost nothing has been done commercially in large scale
thermoelectric power generation.”
Skutterudites have some of the needed properties,
researchers say, but historically have been slow and difficult to make. The new
findings cut that production time from days to minutes, and should not only
speed research on these compounds but ultimately provide a more affordable way
to produce them on a mass commercial scale.
OSU researchers have created skutterudites with microwave
technology with an indium cobalt antimonite compound, and believe others are
possible. They are continuing research, and believe that ultimately a range of
different compounds may be needed for different applications of thermoelectric
generation.
