The gasoline-powered piston engine has been around for over a century now and is currently the default power source for many applications. There are two major disadvantages to this engine: heavy pollution and a limited source of fossil fuels. Some automobile manufacturers are now testing hybrid engines, and have tried converting piston engines from gasoline to hydrogen power (For example, Suzuki and Mercedes-Benz).
2. Electric Motors
Solar panels have been used to power experimental electrical cars with little or no commercial prospect.
Several automobile manufacturers are experimenting with using fuel cells (nickel-metal hydride (NiMH) batteries) to power electric drive motors (For example, Honda FCX-V4, Toyota FCHZ-4, and Ford Focus FCV).
3. Wankel Rotary Engine/Otto 4-Cycle Engine
The Mazda automobile uses the gasoline-powered Wankel Rotary Engine and has had success with converting it to be fueled by hydrogen. There are still some hydrocarbons found in the exhaust.
We at The Bastian Motor Co. see the True Rotary Engine (TRE) as the next best step towards reducing pollution emissions and increasing engine efficiency.
The True Rotary Engine (TRE) would be much less complex than either the Wankel Rotary Engine or the Piston Engine, therefore much less expensive to produce. There are significantly less hydrocarbons in the exhaust making this engine much more friendly in living spaces.