A parabolic solar dish, which maginfies sun by collecting and pointing it to one spot could be mounted outside or on the roof (around 5 feet in diameter would be sufficient).  As the sunlight is magnified, the concentrated (and hot) light could be fed into mirrored tubes (or maybe fiberoptic cables?) and into the ceiling fan on the inside of the building/home.  This heat could power small, simple stirling engines that spin the fan blades to circulate and cool the air inside.  When the sun is hot, they would kick on automatically.  When things cooled off outside, they would shut off automatically.  No electricity required -- completely solar powered and driven.