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NanoCoolers: Clean Tech for Semis?
MIT and Boston College researchers have devised nanoscale coolers and power generators from alloyed materials. The thermoelectric efficiencies could paves the way for next-gen semiconductors, car exhaust systems and even solar power technology, research findings suggest.
The thermoelectric effect, is the direct conversion of thermal differentials to electric voltage and vice versa.
The researchers increased the thermoelectric efficiency by 40% of bismuth antimony telluride - a semiconductor alloy in commercial use since the 1950s. The experiments are noteworthy, researchers say, because success with inexpensive and environmentally friendly alloys means the work could quickly be applied to many real-world uses.
"We have found a way to improve an old material by breaking it up and then rebuilding it in a composite of nanostructures in bulk form," said Boston College physicist Zhifeng Ren, a project leader "This method is low cost and can be scaled for mass production. This represents an exciting opportunity to improve the performance of thermoelectric materials in a cost-effective manner."
"These thermoelectric materials are already used in many applications, but this better material can have a bigger impact," said Gang Chen, the Warren and Towneley Rohsenow Professor of Mechanical Engineering at MIT, another project researcher.
At its core, thermoelectricity is the "hot and cool" issue of physics. Heating one end of a wire, for example, causes electrons to move to the cooler end, producing an electric current. In reverse, applying a current to the same wire will carry heat away from a hot section to a cool section. Phonons, a quantum mode of vibration, play a key role because they are the primary means by which heat conduction takes place in insulating solids.
Other Industrial Uses for NanoCoolers
Thermoelectric materials have been used by NASA to generate power for far-away spacecraft. These materials have been used by specialty automobile seat makers to keep drivers cool during the summer. Further, the auto industry has been experimenting with ways to use thermoelectric materials to convert waste heat from a car exhaust systems into electric current to help power vehicles.
Bismuth antimony telluride is a material commonly used in thermoelectric products, and the researchers crushed it into a nanoscopic dust and then reconstituted it in bulk form, albeit with nanoscale constituents. The grains and irregularities of the reconstituted alloy dramatically slowed the passage of phonons through the material, radically transforming the thermoelectric performance by blocking heat flow while allowing the electrical flow.
"We have found a way to improve an old material by breaking it up and then rebuilding it in a composite of nanostructures in bulk form," said Boston College physicist Zhifeng Ren, a project leader "This method is low cost and can be scaled for mass production. This represents an exciting opportunity to improve the performance of thermoelectric materials in a cost-effective manner."
"These thermoelectric materials are already used in many applications, but this better material can have a bigger impact," said Gang Chen, the Warren and Towneley Rohsenow Professor of Mechanical Engineering at MIT, another project researcher.
At its core, thermoelectricity is the "hot and cool" issue of physics. Heating one end of a wire, for example, causes electrons to move to the cooler end, producing an electric current. In reverse, applying a current to the same wire will carry heat away from a hot section to a cool section. Phonons, a quantum mode of vibration, play a key role because they are the primary means by which heat conduction takes place in insulating solids.
Other Industrial Uses for NanoCoolers
Thermoelectric materials have been used by NASA to generate power for far-away spacecraft. These materials have been used by specialty automobile seat makers to keep drivers cool during the summer. Further, the auto industry has been experimenting with ways to use thermoelectric materials to convert waste heat from a car exhaust systems into electric current to help power vehicles.
Bismuth antimony telluride is a material commonly used in thermoelectric products, and the researchers crushed it into a nanoscopic dust and then reconstituted it in bulk form, albeit with nanoscale constituents. The grains and irregularities of the reconstituted alloy dramatically slowed the passage of phonons through the material, radically transforming the thermoelectric performance by blocking heat flow while allowing the electrical flow.