I have a solar panel connected to a fan in my room and I was curious what would happen if I would open a window to let in some light. Is it permitted If I had intention to let in the light to activate my fan on Shabbat? Is it permitted if my intention was just to open my window and have more air?

Exposing a solar panel to sunlight creates an electric current flow which may be a Torah prohibition. Operating a fan this way is not considered Grama (indirect action) but a Ma’aseh B’Yadayim (direct action) because this is the way of operating it. Therefore one should not expose a solar panel to sunlight, whether his intention is to activate the fan or just to have some more air in the room. One should make sure to cover the solar panel before opening a window so it should not be activated. (For sources in detail see my article in Hebrew "Solar Fan on Shabbat").