Following our best caveman instincts, we've built our personal transportation system around fire-the shrewdly controlled combustion of fossil fuels within piston (and a few rotary) engines. Unfortunately, the most efficient gasoline engines have an energy-conversion efficiency of only 35 percent. Pour a gallon of gas in your tank, and only about one-third of the energy contained in that fuel reaches the transmission to drive the wheels. Another third goes out the exhaust pipe as waste heat, and the remaining third is dumped to the cooling system or radiated to the atmosphere. Diesels also waste their share of energy, although their conversion efficiency is moderately higher, at about 43 percent.
The better way is electricity. AC motors commonly operate at 90 percent energy-conversion efficiency. They produce and waste minimal heat. Furthermore, energy that comes from an outlet instead of a pump is generally cleaner and cheaper. Charging the batteries for a forty-mile drive in the Volt or eighty miles in a Leaf costs only a few pennies per mile. Every kilowatt-hour of propulsion energy drawn from a plug diminishes both tailpipe emissions and the amount of oil we must import. After decades of faithful service in our trains, elevators, refrigerators, and power tools, electric motors are ready to hum under the hoods of our cars.
This is not to suggest that Ferrari's screaming eight- and twelve-cylinder engines are obsolete. Nor that hybrid vehicles, which marry hot and cold energy-conversion devices, are passé. But we are convinced that electric propulsion is ready to finally assume a significant role as one of several powertrain options for the future.
We're not alone in that opinion. A recent study by Credit Suisse, a financial services company, forecasts a global fleet of five million electric cars by 2020. As electrics roll out this year, we expect early-adopter enthusiasm to finally muzzle the skeptics.