Thermoelectric heat recovery could boost auto fuel economy
- PDF / 273,434 Bytes
- 2 Pages / 585 x 783 pts Page_size
- 44 Downloads / 186 Views
•
Energy Sector Analysis
Thermoelectric power, previously limited to spacecraft, is seeing improvements in efficiency that could lead to applications in passenger cars by 2020.
Thermoelectric heat recovery could boost auto fuel economy By Philip Ball Feature Editor Thierry Caillat
T
he internal combustion engine (ICE), inefficient and polluting though it may be, is going to be with us for some time to come. Battery-driven electric vehicles remain a distant prospect for routine use, especially for long-haul heavy transport and construction machinery, and while hybrid vehicles can reduce the consumption of fossil fuels significantly, they too will remain a niche technology in the immediate future. That doesn’t sound like good news for reducing vehicle carbon dioxide emissions. Yet reductions are becoming legally obligatory: In 2020, for example, the average fuel consumption of all new passenger cars in Europe needs to be at least 25 km/l (70 miles per gallon). If such targets are to be met, gasoline-driven vehicles will have to work much more efficiently. There’s certainly plenty of scope for improvement. Only a third of each gallon of fuel burnt in a conventional ICE vehicle is converted to useful mechanical power; the rest is wasted, being converted into heat. Some of this thermal energy could be converted directly into electrical energy by thermoelectric (TE) generators, to be used for propulsion and to drive the vehicle’s electrical components such as air conditioning, lights, windows, and—for transportation and construction vehicles—systems such as electric doors, platforms, and hydraulics. By reducing the load on the alternator (the electric-generating system that runs off the ICE), this sort of energy capture would ultimately improve fuel efficiency. TE conversion efficiencies of up to 15% have been recently demonstrated by the US National Aeronautics and Space Administration (NASA) for large temperature gradients—two to four times that of current commercial TE systems. If similar efficiencies could be achieved for the smaller temperature gradients typically in automobiles, then capturing 5–10% of a vehicle’s waste heat this way could reduce fuel consumption by 3–6%, which is potentially significant for both cost and emissions savings. The automotive industry is just one area in which TE conversion could provide a valuable boost for efforts to make energy generation cleaner and more efficient. Such systems could also recapture energy currently lost from the hot effluent of powerplant smokestacks, and could harvest the heat currently generated but not used by photovoltaic cells. TE generators are already used for energy generation in spacecraft. But because of the large scale of the automobile sector, the projections for future growth, and Thierry Caillat, Jet Propulsion Laboratory/California Institute of Technology Philip Ball, [email protected]
446
MRS BULLETIN
•
VOLUME 38 • JUNE 2013
•
www.mrs.org/bulletin • Energy Quarterly
the current inefficiencies it suffers, the use of TEs in vehicles loo
Data Loading...
