BMW aims to put rocket science in your car
By Christiaan Hetzner
GENEVA (Reuters) - Germany's BMW wants to use NASA technology to boost the fuel efficiency of its luxury cars and lower emissions of harmful greenhouse gases.
Engineers at the BMW's high tech experimental lab in Palo Alto, California are attempting to adapt the thermoelectric system for cars that NASA scientists employ to help power their deep space probes navigating the far reaches of the solar system, BMW's director of vehicle integration told Reuters.
The NASA probes use so-called radioisotope thermoelectric generators (RTGs) which transform heat emitted from naturally decaying plutonium into electricity. BMW wants to bring this concept back to earth by reclaiming the thermal energy released in engine combustion.
"I firmly believe that when you look at this technology in 20 years, this will be the key issue that will replace everything else," Hans Rathgeber told Reuters in Geneva.
Rathgeber said simple physics prevents a conventional combustion engine from ever exceeding one-third efficiency. A motor with an output of 200 kilowatts (kw) generally creates 400 kw thermal energy as a waste by-product.
Recycling this abundant energy source would require replacing the plutonium in a RTG with a non-hazardous material that conducts electricity while resisting heat, not an easy task since most metals become hot when a current is applied to them.
BMW settled on a semiconductor element called Bismuth Telluride as a link between the car's engine coolant and its exhaust gas manifold to fuel the thermoelectric cycle.
Simply put, a charge is induced when you heat and cool two separate ends of a closed circuit. The amount of electricity generated is proportionate to the difference in temperature at the two points -- a property known as the "Seebeck Effect." Continued...