It sounds like something from a sci-fi movie, but the newly revealed Shadow-Effect Energy Generator (SEG) is a real prototype device. The fascinating concept could help us to transform the way renewable energy is generated indoors.

The SEG uses the contrast between darkness and light to produce electricity. It’s made up of a series of thin strips of gold film on a silicon wafer, placed on top of a flexible plastic base.

Whereas shadows are usually a problem for renewable solar energy production, here they’re actually harnessed to keep on generating power. The technology — which is cheaper to produce than a typical solar cell, according to its developers — produces small amounts of power and could be used in mobile gadgets, for example.