Yunxin Liu, Zhen Qin and Chunshui Zhao from Microsoft Research's Beijing campus have developed a new system they call AutoCharge.

The researchers' paper said that "wireless power methods have several disadvantages, preventing them from being used in our targeted usage scenarios"

Electromagnetic radiation of wireless power is much higher than wireless communications (Wi-Fi or 3G). Thus, safety to human bodies is a big issue in wireless power. As a result, wireless power is usually used only in extreme scenarios such as in outer space, for military purposes, or in very short ranges.

Radio frequencies used in wireless power are much lower than the frequencies of light, it is hard to emit the radio waves within a straight beam. This causes energy waste if the receiver is not large enough and makes it hard to ensure safety.
The current crop of wireless charging solutions for smartphones typically require special phone cases and 'charging pads', and work using electromagnetic induction. Power is transmitted only over a few centimetres.

However the researchers came up with a way of using solar power techniques to charge smartphones.

Indoor surrounding light is usually much than the sunlight and thus cannot be used to charge a smartphone but instead of relying on the sun, the team built a prototype charger that can be mounted on a ceiling and automatically locate a smartphone lying on a table, then charge it using a directed beam of light.

The light charger has two modes. In the 'detection' mode, it uses a camera and image recognition software to detect objects with the size and shape of a smartphone lying on a table. The charger will rotate until it detects an object that looks like a smartphone.

The device then enters charging mode and turns on its light. The prototype used an UltraFire CREE XM-L T6 Focusing LED Flashlight.
Looks pretty cool to us.