A zero emission engine, motor, process, or other energy source emits no waste products that pollute the environment or disrupt the climate.
These technologies almost in all cases include an electric motor powered by an energy source compact enough to be installed in the vehicle.
These sources include hydrogen fuel cells, batteries, supercapacitors, and flywheel energy storage devices.
This mechanical engine is then powered by a passive energy source like compressed air, or a combustible non-polluting gas like hydrogen.
For boats, energy sources such as nuclear power and solar panels can also be a viable option, in addition to traditional sails and turbosails.