Samsung Transparent LCD Window
Regular LCD panels need BLUs (Back Light Units) as a light source in order to display an image; without a light source, nothing would be visible. Transparent LCDs lack BLUs, usesing instead other light sources available (sunlight, in-door lighting). In darkness you can activate the transparent BLU, designed specifically for transparent panels, as a light source.
An advantage to the transparent display is its energy efficiency. When the transparent BLU is not activated, the transparent LCD uses only 10% of the electricity used by a regular LCD screen of equivalent size. Rumor has it, it’s going into mass production in just a few months.