http://www.nytimes.com/2001/11/27/technology/27HEAT.html?todaysheadlines
November 27, 2001
A Practical Way to Make Power From Wasted Heat
By KENNETH CHANG
cientists at M.I.T. and a small company in Salt Lake City are scheduled to
announce today that they have developed technology that can efficiently and
inexpensively transform heat pollution into electricity.
Although only a few crude samples have been built, Dr. Yan Kucherov, director
of research and development at the Salt Lake City company, Eneco Inc., and
Dr. Peter L. Hagelstein, professor of electrical engineering at M.I.T. and a
technical consultant at Eneco, say that their devices improve the efficiency
of the conversion by more than half.
"It's really first-generation, very primitive implementation," Dr. Hagelstein
said. "Potentially, it's an enormous deal. This opens a door."
While the heat generated by car engines and power plants usually does nothing
but warm the surrounding air, scientists have long dreamed of building
so-called thermoelectric devices that can capture the wasted heat and convert
a portion of it into electricity.
Such devices could significantly increase the electrical output of existing
power plants or power the electrical systems of automobiles, replacing
alternators and increasing gas mileage.
The Pentagon, which partly financed the new research, has been interested in
using the devices for silent motors. Operating in reverse, thermoelectric
devices can also be used as refrigerators.
Another advantage of thermoelectric devices is that they produce electricity
without generating additional pollution.
Current thermoelectric technology converts only about 10 percent of the heat
it absorbs into electricity, too inefficient a return for widespread use. The
new devices, however, reach about 17 percent, and Dr. Hagelstein said future
devices should be able to improve upon that significantly.
It is impossible to transform 100 percent of the heat into electricity. The
laws of physics dictate a theoretical maximum of about 50 percent at the
temperature a thermoelectric device operates at. Current commercial
thermoelectric devices, at 10 percent efficiency, get only one-fifth the
maximum. Using the new technology, future devices should be able to achieve
more than half the maximum.
The researchers are presenting their findings at a meeting of the Materials
Research Society in Boston. Scientific papers describing the experiments have
been submitted to the journals Physical Review Letters and Applied Physics
Letters.
If borne out, the findings would be significant, said Dr. George S. Nolas, a
professor of physics at the University of South Florida and an organizer of a
symposium about thermoelectric devices at the Materials Research Society
meeting. Dr. Nolas had not seen the Eneco paper but said the reported
efficiency was high enough to find practical use and "would be pretty good
news."
Eneco's thermoelectric device is a sandwich of three layers of semiconductor.
One outer layer is heated; the other is kept at room temperature. The middle
layer acts as an insulator to maintain the temperature difference.
The heat causes electrons to shoot out, some crossing the sandwich to
generate an electrical current. The Eneco researchers added impurities — a
process called doping — to the heated layer to increase the flow of
electrons.
"The region near the hot part is heavily doped, so it boils off electrons,"
Dr. Hagelstein said. "We get more voltage and more current."
He added: "The underlying technology is really very simple. It should be a
very practical, relatively cheap technology."
Leroy Becker, marketing director of Eneco, which is not associated with the
Dutch utility Eneco Energie, said the company hoped to produce a prototype of
a practical device within a year and sell it within two years.
Eneco, a privately held company, was created in 1991 to seek to license
patents on cold fusion after the controversial claim of two University of
Utah scientists that they could produce almost limitless amounts of energy in
a room-temperature flask of water. Eneco also financed follow-up research on
cold fusion, including work by Dr. Hagelstein. The claims for cold fusion
were far overstated, and several years ago, Eneco shifted its focus to
thermoelectric devices.
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