BACKGROUND: The German-American consortium of BMW, DaimlerChrysler and General Motors are developing a new type of two-mode hybrid system for a wide range of cars, trucks and SUVs, starting with the 2008 Chevrolet Tahoe available in fall 2007. Current hybrids perform well in stop-and-go city driving, but don't get as good mileage on the highway. The new hybrid version will get 25 percent better mileage in combined city and highway driving.
ADVANTAGES: Current hybrid engine systems have a single mode of operation, using a single gear set to split the engine's power into two systems -- routing it to drive the wheels or charge the battery -- for both city and highway driving. Like other hybrids, the two-mode combines the power of a gasoline engine with that of electric motors, capturing energy from braking that would otherwise be lost and shutting off the engine at a stop. The battery alone can power the vehicle at low speeds. The new technology can operate much more efficiently at highway speeds with a greater boost from the electric motors, shutting down half the cylinders when not needed, thereby improving gas mileage. The components of the new two-mode system are also lighter and more compact, making them especially useful for reducing overall fuel consumption.
BATTERY BASICS: Whenever one type of matter converts into another, as in a chemical reaction, one form of energy also changes into another. A battery has two ends, called terminals, one with a negative charge, and one with a positive charge. Electrons congregate on the negative terminal. Connect a wire between the two terminals, and the electrons will flow from the negative to the positive end as quickly as they can. Connecting the battery starts the flow of electrons, jumpstarting a series of chemical reactions inside the battery to create even more electrons.
HOW FUEL CELLS WORK: Just like batteries, a fuel cell is a device that uses chemical reactions to convert hydrogen and oxygen into water, producing electricity in the process. A battery eventually goes dead when all the chemicals are used up, but in a fuel cell, there is a constant flow of chemicals into the cell. The voltage produced by fuel cells can be used to power lights, electrical appliances, and laptops, as well as cars and trucks. Fuel cells are light, more efficient than internal combustion engines, and don't produce damaging emissions. They are currently expensive to manufacture, however.
The Institute of Electrical and Electronics Engineers, Inc., contributed to the information contained in the TV portion of this report.