BATTERIES, FUEL CELLS, AND FLYWHEELS
Cars and trucks are responsible for using almost 30 percent of the fossil fuel energy consumed in the United States. Almost all of this energy comes from petroleum products. When gasoline and diesel oil is burned, it emits, as a byproduct, ozone and nitrogen oxides. Nitrogen oxides are largely responsible for the smog in large cities, and ozone is an irritant of the lungs, a serious irritant for those who have breathing problems.
There is a twofold purpose in seeking substitutes for fossil fuels in motor vehicles. One is to find a renewable source of energy in place of petroleum products. The other is to mitigate the environmental damage caused by the burning of gasoline and diesel oil. The serious harmful environmental impact caused by burning fossil fuels has not been adequately dealt with by society. The smog problem and the pulmonary irritation due to ozone have finally aroused the public and have led some state legislatures to propose serious measures for partially replacing automobile gasoline engines with electrical batteries.
Batteries are devices that convert chemical energy directly into electrical energy. While they solve the emission problem, they do not necessarily replace fossil fuels. Energy cannot be created out of whole cloth (unless the cloth is burned); the energy available in a battery must be supplied from some other source. At the moment