IN COUNTRIES where mains electricity is unreliable or nonexistent, placing a grid of heat-resistant thermocouples onto a cooking stove could generate enough power to run a few light bulbs or a television.
The idea comes from Mike Rowe at Cardiff University, who has been working on ways to improve the efficiency of generators that use the 鈥渢hermoelectric effect鈥�. In a loop made of two dissimilar metal wires joined end-to-end, current will flow if the junctions between the metals are maintained at different temperatures. And the process is reversible: applying a current causes a temperature change at the junctions.
Thermoelectric generators were first used in the 1970s. NASA used them to power its twin solar system explorers, Voyager 1 and 2, which are still going strong. A decaying radioisotope provides the heat source.
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But the thermoelectric effect hasn鈥檛 been used to generate power except in space because it is so inefficient. In many developing countries, however, worries about efficiency concerns are very low down the list. Any electricity is better than none, says Rowe.
Working with Gao Min at Cardiff, and Rida Nuwayhid at the American University of Beirut, Rowe investigated whether thermoelectric devices could be used to mop up waste heat from a simple wood stove. There are tens of thousands of homes in Lebanon with this sort of stove, but no reliable mains electricity.
For their domestic stove-based generator to work, they had to modify a type of thermocouple made of bismuth telluride and aluminium. Bismuth telluride is a semiconductor that can be doped with electron-rich substances to help produce a bigger current.
By linking a number of these modules, and making them more resistant to high temperatures so they could withstand the heat produced by a stove, the researchers managed to produce about 100 watts, enough electrical power to light a room or run a small television.
They work so well, Rowe told New 杏吧原创, the prototypes can even use hot waste water from a bath to power a television for about an hour. 鈥淲e are actively collaborating on the rural development of this technology,鈥� he says.