Wireless charging of multiple devices simultaneously

Mobile phones and tablets allow us to stay in touch regardless of our location, yet they still rely on plugs, sockets and charging pads to power up. New technology developed at Aalto University may be the key to true wireless charging for these and other electronics in years to come.

While researchers around the globe are working on free-position wireless charging — which would unchain devices from set charging points — the most common solutions involve complex control and detection functions. A transmitter traditionally has to first detect a device presence and position to be able to send energy in its direction, usually done with cameras or sensors, adding bulk and cost to the device.

The Aalto-developed transmitter bypasses this need by creating power transfer channels in all directions, automatically tuning channels when receiving devices are in motion. Devices like phones, laptops and other small appliances equipped with a new receiver can simultaneously receive energy to charge batteries or directly power their functions — without ever being in physical contact or being brought to a specific place.

“What sets this transmitter apart is that it’s self-tuning, which means you don’t need complex electronics to connect with receivers embedded in devices,” said team member Dr Prasad Jayathurathnage, a postdoctoral researcher at Aalto University. “Since it self-tunes, you can also move the device freely within a wide charging range.”

The team has achieved the effect through the design of the coils used in the transmitter. By winding the coils in a specific way, they create two kinds of electromagnetic fields: one going outwards and the other around. These fields couple the receiver and transmitter to achieve efficient power transfer.

Components of the device. Image credit: Prasad Jayathurathnage/Aalto University.

Currently, the transmitter is highly efficient at 90% at up to 20 cm distance, but it continues to work at longer distances — just with a lower efficiency of energy transfer. In principle, the peak efficiency range could grow as the technology is refined.

“For now, the maximum range at peak efficiency is dependent on the size of the transmitter and receiver,” Dr Jayathurathnage said. “With the right engineering, we could shrink them down.”

While the team has demonstrated proof of concept, safety tests are still needed to confirm that the electromagnetic field generated by the transmitter is not harmful to humans. It is, however, clear that the resulting electric field, which is known to be the main cause for potentially harmful effects, is minimal as the technology relies on magnetic fields.

The researchers have already applied for a patent for the transmitter, having published their findings in IEEE Transactions on Industrial Electronics. The same group is also developing wireless charging possibilities for industrial applications through the Parkzia project, which turns any waiting point for robots like e-movers into a charging spot.

Top image credit: Prasad Jayathurathnage/Aalto University.

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