Compressed air car The principal disadvantages are the steps of energy conversion and transmission, because each inherently has loss. For combustion engine cars, the energy is lost when chemical energy in fossil fuels is converted by the engine to mechanical energy. For electric cars, a power plant's electricity (from whatever source) is transmitted to the car's batteries, which then transmits the electricity to the car's motor, which converts it to mechanical energy. For compressed-air cars, the power plant's electricity is transmitted to a compressor, which mechanically compresses the air into the car's tank. The car's engine then converts the compressed air to mechanical
Potential energy distance at which "U" becomes zero: formula_34 and formula_35. The choice of formula_36 at infinity may seem peculiar, and the consequence that gravitational energy is always negative may seem counterintuitive, but this choice allows gravitational potential energy values to be finite, albeit negative. The singularity at formula_34 in the formula for gravitational potential energy means that the only other apparently reasonable alternative choice of convention, with formula_36 for formula_34, would result in potential energy being positive, but infinitely large for all nonzero values of "r", and would make calculations involving sums or differences of potential energies beyond what is possible