Running the fan directly from the solar panel in full sun works decently; enough to push air at an acceptable rate. It is a "permanent" setup, with the fan and solar panel always being connected.
My question is: Would there be a premature aging issue to either fan or panel if there is only partial sun?
There is a bit of hysteresis because it of course takes more power to start the fan than to keep it running. So if it stalls, it can stay stalled for quite some time before it gets going again (if at all before next sun-up).
I think the panel will be fine, as I've read that short-circuits are not inherently bad for them, so the increased stall current should be no issue.
However, I'm more concerned about the fan circuitry. Since they are designed to run from a regulated 12V supply, I wonder if the drivers will have an issue running with only partial power and a stalled fan.
I realize that it can depend on the specifics of the fan I'm using, and that the innards are not disclosed. I imagine the fans are typically similar though, so anyone who has an understanding of how a typical PC fan works may be able to shed some wisdom as to why it would or would not be an issue to stall a PC fan for extended periods.