Unlike many other models, the Natural Light Solar Powered Attic Fan has an adjustable Photo panel. My house is on a NE/SW line, which means that my roof slope is NW/SE, with the back being NW - not a good direction to catch the sun. However, with the adjustable panel, I was able to install the fan just below the ridge on the back (NW) side, but angle up the Photo panel to effectively face SE. Works fine so far, after 4 months.
Even in no sun, it does act as an over-sized passive vent, which is what most regular houses use anyway.