[RedDevil]

I believe I read somewhere the air speed close to the radiator is 1/6th of the velocity of the vehicle. Which, if true, means that the energy that could be derived of that fan is 1/6^3 of what it could have been in full wind.
Which is as close to nothing as anything; it would be a real challenge to harvest more than a few milliWatt out of that.

One could stick a row of TEGs to the radiator with a copper strip on the back and harvest a few Watt from the Seebeck effect. That in comparison would be way less uneffective.

I've been thinking about a micro turbine on the air intake to harvest energy from the vacuum draw on partial load, only to find no suitable turbines and generators for such a tiny draw exist. There's a potential of several hundred Watt there, but even that proved to be elusive.

I wish I could have given off a happier signal.