Can you mount a wind turbine or solar panels on the hitch? Like this but not touching the ground?
Wind turbine would be great, because it needs much less space than solar. But it needs to be very high above the ground to get enough wind (unless at the beach or in other extremely flat areas) and that's obviously difficult to accomplish with a low car. The leverage is just too high. Another downside are the prices here. It's much worse value for money than solar.
For now I'll keep my 48 V solar roof plus my 12 V square panel on the hood (since two weeks). The roof rack also incorporates lights all around (two high beams in the front, seven camping lights, four orange flashers and one illegal blue
) that can be switched individually.
I assume that the rack itself is actually responsible for the most drag. These racks are limited to 130 km/h for a reason... There are cases of ripping racks apart at 180! The wind forces are significant above 130 and increase by square. 150 mph are only possible over longer distances with the stock M3 because its body is shaped extremely aerodynamic. Otherwise overheating would occur much earlier. My times of driving that fast were over as soon as I started mounting the rack in June 22... But there will probably be a general speed limit of 130 in Germany soon anyway.
The solar roof itself (mounted on the rack) is so thin, that its wind resistance should be very low. It survived a storm already. At first I was very worried about the car being parked unprotected, but then I realized that the wind just goes through blowing from front or rear and over it from the side. And the complete construction on the roof is at least 100 lbs, so even strong gusts don't lift it. My current solar setup is definitely more storm-proof than the ones in the videos Atraf posted. You can't have it all...