Thermoelectrics — semiconductors that converts heat into electricity — haven’t been widely used because they are expensive and inefficient, but researchers have recently developed much more efficient thermoelectrics by adding trace amounts of thallium to lead telluride:
The added thallium doubled the material’s ability to convert heat into electricity by increasing the voltage that it produces. Heremans says that the improved efficiency could translate into a 10 percent increase in the fuel economy of cars if the devices are used to replace alternators in automobiles by generating electricity from the heat in exhaust.
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Conventional lead telluride thermoelectrics convert about 6 percent of the energy in heat into electricity. Once it’s incorporated into a thermoelectric generator, the more efficient thallium-enhanced material could increase this to 10 percent, once losses, such as those from making electrical connections, are taken into account.
One drawback is that thallium is extremely toxic.
Anyway, thermoelectrics could increase the fuel economy of cars, because cars waste a lot of energy as heat — almost all of it, in fact.
Currently cars use an alternator to transform mechanical energy into electricity — to recharge the battery, etc. — but thermoelectrics could transform some of that wasted heat instead.
(Hat tip à mon père.)