The Mirai is a hybrid with no engine. Instead, it gets a hydrogen fuel cell – the first one on sale in the UK. Hydrogen and oxygen are pumped into either side of the membranes of the fuel cell, and a catalyst separates the electron from the hydrogen proton.
This travels around an electrical circuit back to the oxygen side, where it meets the proton, which is tiny enough to have popped through the membrane.
The electrons, protons and oxygen combine to produce water, the only emission.
The electricity powers the wheel motor, but a buffer battery enables hybrid tricks: more peak power from the motor, and regeneration for increased efficiency.