Jonathan bought a 64pixels kit and modded it into a green version. The three solar cells, that he uses are rated with: 2.7 volts (open circuit) @ 15mA (short circuit). He writes, it works well in bright sun light. His desktop lamp shines with 60 Watts and that seems to work as well.
He also used a socket to be able to pop out the controller, whenever he wants to program new messages or animations.