Magnetic field breakthrough leads the race for wireless charging

THE advent of wireless charging was heralded as a panacea for modern life, making it possible to recharge phones and other electronic items rapidly without the need for a cable. However, it was a false dawn, as it works only when a phone is placed on top of a charging pad plugged into the mains.

Now, scientists have managed to fulfil the early promise of wireless charging after building a room which can wirelessly charge all compatible devices whether they are on the table, in someone’s pocket, or even under the sofa.

Takuya Sasatani, an electrical engineer at the University of Tokyo, built a room (10ft x 10ft x 6.5ft) and wired it so that there are two magnetic fields bouncing around inside the space.

This technique, dubbed multimode quasistatic cavity resonance (M-QSCR), involves various conductive surfaces placed around the room, and a smattering of capacitors. It builds on previous technology which found that using a pole in the centre of a room, a single magnetic field can be generated which can charge devices.

However, the previous method had dark spots where the magnetic field did not reach and therefore where devices would not charge. The new method fixes this by using two magnetic fields which target different areas of the room. One focuses on the centre, and the other is strongest around the walls.

“The system forms a 3D powering range, and the two modes successfully complement the null zone of each other,” the researchers write in their study, published in Nature Electronics.

This technique, they say, means that in 98 per cent of the room a device will charge at least 50 per cent efficiently. In the remaining 2 per cent a battery will still charge with at least 37 per cent efficiency. It doesn’t matter if the device is in motion, either, the researchers say, as the battery still receives charge while on the move.

Analysis found that the single-magnetic-field method manages an efficiency above 50 per cent in only 57.5 per cent of the room and efficiency plummets to just 1 per cent at the walls.

Researchers furnished the room with various objects, including a chair, lamp, sideboard, table and plant, and found the wireless charging worked just as well as before, with the system powering a fan, lamp and mobile phone. The authors also believe that in future, the technique can be refined so the central pole can be removed.

“We expect that our technology should be widely applicable in a range of scenarios, including charging cabinets, wireless charging rooms and untethered factories,” they write.

The two magnetic fields are of such low energy that they pose no threat to human health, they add.