Wireless power system charges devices up to 20 feet away

A plethora of firms are racing to develop a feasible method for delivering power wirelessly, but thus far the best we’ve managed are short-range standards like Qi and PMA. A company called Energous is on hand at CES with a demo of its new wireless power system known amusingly as WattUp.
It uses a mix of Bluetooth and RF to combine the convenience of wireless power with the security of a wireless network. If it all pans out, WattUp could juice up your phone from up to 20 feet (6.1 meters) away. The heart of WattUp is a hub that’s basically a powerful RF transmitter station. Devices that want to receive power from the hub announce their presence via Bluetooth 4.0.
WattUp then uses that connection to direct the wireless power signal to the device. It operates in the same unlicensed spectrum as WiFi, which makes me wonder about possible interference in busy wireless environments. Assuming the connection holds, though, the WattUp signal is absorbed and converted to DC power in the phone or tablet by a receiver chip.
Whenever you’re sending an electromagnetic signal through the air, you have to worry about signal drop-off as dictated by the inverse square law. The gist is that signal strength decreases at a rate equal to the square of the distance. For example, a device twice as far away from a source only gets one-quarter of the energy. Some experiments in long-range wireless power have simply brute forced their way through this problem to the point that they actually heat up the air around the transmitter.
WattUp combats this problem with a type of beam-forming technology. That Bluetooth connection is used to focus a tight cone of electromagnetic waves on the target, and it can even track the device and recalibrate as needed. A standard Qi wireless charger is about 90% efficient, but Energous claims it can hit 70% at much greater distances.