Why don’t electric / hybrid cars have “RATS”, ram air turbines (like some jets)?


Or even a little vent that is synced with brakes/speed sensing logic (pitot static system) that has turbines inside that will spin with the induced air and charge the battery a bit?

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If you try and recover energy from air while driving you also create drag (which is where the energy comes from), which means you need to put more power to the wheels, making the RATS pointless.

If you do it while braking any energy you could recover from air can be recovered much more efficiently, and without extra hardware by braking with the motors.

RATS on an airplane are for emergency use only to power critical systems and keep the plane controllable when things have gone terribly terribly wrong. In an electric car you would just lose power steering and should still have a mechanical emergency brake.

Electric vehicles have something better:

Regenerative breaking.

When you break and actively try to slow down an EV, the car uses the turning of the wheels to power a dynamo that creates electricity to re-charge the battery.

Getting your energy directly from the wheels is far more efficient that trying to get it from air resistance.

It is the same reason why cars are usually propelled forward by having a motor turn their wheels rather than a propeller or jet engine. Friction with the road rumps friction with the air.

Planes don’t have much choice because they are not anywhere near the ground most of the time and only can brake and accelerate themselves by interacting with the air around them. Cars have the advantage of being on the road.

Of course if you don’t want to slow the vehicle down, trying to get extra energy from the movement of the vehicle is a fools errand. the laws of thermo dynamics mean that any extra energy you get out of it is less than what you put in.

Regenerative breaking though works and works well.