Putting solar cells onto a car and/or using portable solar units to charge an EV are apparently a flash hot button issue for many electric vehicle advocates, some (many?) of whom patronizingly, in my view, immediately dismiss such efforts as “useless”.
I have long been very interested in the question of how much it (does not) matter(s) when one plugs one's electric vehicle in, especially if, like I do, I have the choice of plugging into a home rooftop solar system.
Many years ago, I wrote extensively on this web site/blog about the many intricacies and complexities of what I call "solar offset" charging of an electric vehicle vs. directly filling up with electricity that has been/is being produced directly by a (home rooftop) solar system connected to the same electrical box into which an EV charger and/or the wall-socket into which you're plugging your EV into.
The cohousing community that I live in -- Highline Crossing Cohousing -- here in Littleton, Colo. is FINALLY getting solar after a one-year wait for the installation and, prior to that, 18 months of me, and several other residents here in this community, working toward persuading our community to add a 20 kW solar system.