Green Technology

Research Frontiers, Inc's SPD technology uses suspended particles in glass to react to a small voltage to change from clear to nearly blocked. With voltage is applied the glass is clear.

This would allow for large glass windows for light and letting the same windows block direct sun to reduce A/C load and reduce UV damage to fabrics.

' ...provides exceptional control over solar energy..." 

" ... ability of architectural smart glass to improve the energy efficiency of buildings by effectively controlling solar heat gain and harvesting daylight ..."

Via:  Research Frontiers, Inc.  LINK and LINK