I Just had an idea for passive solar windows. Instead of counting on fallible and busy humans to open and close shades on south facing windows, can somebody disign an automatic system? I'm thinking of a system that uses sring loading or gravity to hold them closed, when the sun hits a pv panel a small motor would wind it up and hold it as long as the sun was out. You would need some kind of manual overide. Just a thought I figured i would throw out there. Hopefully someone smater than me can run with it.