Sun & Solar Powered Clock

Light Gap is a concept clock with solars cells on its backside. You stick it on a window so sunlight can illuminate the slit on the face to form the hour hand. As day moves into night, batteries kick in to illuminate a row of LEDs in the slit, thanks to the aforementioned solar cells.
Light Gap is a Red Dot Concept Design 2010 winning entry.
Designers: Chengyuan Wei, Fangtian Ying, Duyin Qin, Pengxiang Jia, Fan Zhang, Huabiao Shan, Yu Zhang, Chen Zheng, Guanyun Wang & Lifu Yao