Better gas mileage in town than on the highway
This is a characteristic of hybrid-electric vehicles. Regenerative braking explains it. Regenerative braking means that the energy of the moving vehicle is scarcely wasted. Instead of this energy appearing as heat in the brake pads, 85% of it is restored to the battery. Visualize a powerful bungee cord stretching and stopping the car. Then when the car takes off from the stop, the 85% stretched bungee cord miraculously appears in front helping the internal combustion engine. This additional acceleration does not require nearly as big a gasoline engine for expected performance. The gasoline engine needs only enough power for cruising, a big factor in the remarkably economical performance. The rest of the acceleration comes from the electric part of the hybrid. This arrangement depends on the fact that an electric motor can function equally well as a generator of electricity. So the energy saved during slowing down reappears as stored chemical energy in the batteries. All that is required is some sophisticated electronic circuits in a small black box (jargon for too complex for easy explanation). The black box also starts the internal combustion engine whenever the battery needs charging or full throttle acceleration is called for. Wind resistance increases very rapidly with increasing speed, so driving in town in a hybrid electric car gives the economy of driving slowly in spite of the stops and starts.
Small such vehicles have been in the hands of the public for several years and their reliability has been proven. Hybrid-electric SUVs and luxury cars are well along in the planning stage. A nationwide parcel delivery service has ordered a fleet of hybrid-electric delivery vehicles. They will get their extra investment back promptly as fuel economy. Watch for these vehicles. Even if they do not turn out to be a transition to the “hydrogen” economy, hybrid-electric vehicles are a substantial advance in reducing fossil fuel consumption.
November 15, 2003
Here’s an idea that came to me in the spring of 2006. Put the electric motor between the transmission and the automatic transmission in a hybrid electric vehicle. Program the "black box" to down-shift the transmission when a moderate pressure is put on the brake pedal--two down-shifts for more severe pressure short of a panic stop that would invoke the brake pads. The normal free-wheel at the engine would prevent the engine's participation. Much more energy would enter the battery with any ordinary driving technique without requiring practically coasting to a stop to get maximal regenerative braking because the electric motor, acting as a generator, would convert the kinetic energy of the vehicle’s motion to electricity at a much faster rate.