BFD
Picture a foldaway ice rink, or a completely silent refrigerator, or an air conditioner so tiny it can cool microscopic hot spots on a computer chip. Far-fetched? Not anymore. After three decades of stagnation, the field of thermoelectrics is heating up.
We'll spare you an exegesis on thermodynamics. Suffice it to say that in 1834, a clever Frenchman named Jean-Charles-Athanase Peltier noticed that running electricity through two dissimilar conductors sets up a heat pump without any moving parts. The current pushes heat toward one end of the circuit, cooling the other end. A related phenomenon can also be exploited to turn heat into electricity. These thermoelectric effects have been harnessed to cool the lasers in fiber-optic lines, create greener refrigerators (like Igloo's SpaceMate), and fuel mini power packs for deep-space probes like those used in the Cassini mission to Saturn.
But the technology hasn't progressed much since the 1960s due to the thermoelectric limitations of most materials. Historically, the best conductors allowed for only 10 percent efficiency, meaning about 90 percent of the energy input is wasted. A good compressor-driven fridge runs at about 40 percent efficiency.
That's where scientists at North Carolina's Research Triangle Institute made their breakthrough. Funded by the Defense Advanced Research Projects Agency, RTI engineers concocted a heat pump using two atomically precise superlattices of bismuth telluride, one layered with antimony telluride, and one with bismuth telluride selenide. The result: a device that conducts electricity and insulates against heat transfer better than anything ever seen. Way better - it's 2.5 times more efficient and 23,000 times faster than the stuff it replaces. At 25 percent efficiency, the new coolers open a world of practical possibilities. "We've created the most compact and perhaps fastest refrigeration device in the world," says Rama Venkatasubramanian, who led the group in North Carolina. "With this, we can fully realize the power of existing technologies and provide entirely new capabilities."
The potential is huge. The materials can be fashioned into tiny heat pumps that will spot-cool processors. Microscopic cooling and heating can be put to use in biotech to regulate the localized temperature changes on DNA microarrays. The new system's ability to generate electricity could capture enough energy from a car's excess heat to power fuel-cell batteries and run the air conditioner.
Less exotic applications - such as refrigerators and home heating and cooling - are further off. But Venkatasubramanian says he's making progress on them, too. "At this point, we've got a very good material in one layer of the lattice," he says. "We still have to improve the other layer, the device design, and the manufacturing issues. That's where the big payoff will be." This time, it shouldn't take 40 years.
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