Thermoelectric Generators
In an internal combustion engine, fuel is burned to power the engine, but as a result a lot of heat is also produced. Most of that heat in ordinary vehicles is wasted; but what if you could catch the energy from the heat, turn it into electricity, and use it to increase your fuel efficiency?
Well, that's exactly what one thermoelectric device-maker, BSST in Irwindale, California, is planning to do. BSST and GM are both independently assembling their first prototype thermoelectric generators for tests in commercial cars and SUVs. The thermoelectric equipped BMW and Ford cars (BSST), and a Chevrolet SUV (GM), will be road testing the thermoelectric devices by the end of summer.
GM researchers are putting the final touches on their prototype, which uses a new class of thermoelectrics called skutterudites. The unit looks promising thanks its lower cost of production materials, cobalt arsenide compounds and rare earth elements such as ytterbium, which also appear to be performing better at higher temperatures. So far, computer models show that a Chevrolet Suburban test vehicle could generate 350 watts, which help improve fuel economy by three percent.
The largest challenge is finding a balance for creating good electrical and thermal contacts. To produce electricity the thermoelectric device requires a large temperature gradient using by two unlike materials. At the same time the difference creates more resistance which causes the contacts to heat up. Heat also a acts as stress and just like an overheating engine, it degrades the entire system.
This is where BSST's research comes into play. BSST is currently looking into another family of thermoelectrics using a blend of hafnium and zirconium. So far it's proven to work well at high temperatures and has increased generator efficiency by about 40 percent.
