Minimising fan use by improving ventilation flow

[Tesla]

Haven't tested yet, but had an idea today.
Been reading all the threads on alternators and power drain and noticed ventilation fan was often mentioned, so it got me thinking, how do you get more air in.
The air is drawn in at the base of the windscreen usually which is a high pressure zone, and usually extracted from the cabin somwhere on the sides, towards the rear. All vehicles have a low pressure zone somwhere at the rear, would it be feasable to set up a duct in the low pressure zone to pull air through.
I just tried a quick hand out the window test and airflow at 50km/hr is about the same as the ventilation fan on full, so it could virtually delete any need for a ventilation fan and reduce use of the alternator.
What do you think?