Adoption of wireless charging has been fairly slow, but it could pick up if it worked over longer distances. Now, engineers at Aalto University have developed a new system that can allow more efficient wireless power transmission over longer distances.
Currently, wireless charging requires that a device be left on a pad or dock, which isn’t much better than wired charging. The ultimate end goal for wireless charging would be where we no longer even have to think about charging our devices – they’d just top up wirelessly while we’re in our homes. It’s the same way we don’t have to plug our phones in to receive data, since Wi-Fi takes care of it without us thinking about it.
The problem is, wireless charging efficiency drops off very quickly as the distance between sender and receiver increases, and radiation from the sending and receiving coils interferes with the transmission. So for the new study, the Aalto team developed a new dynamic theory of wireless charging that allows them to increase efficiency over longer distances.
The team tested the idea using two loop antennas, each 7.2 cm (2.8 in) wide. By tweaking the currents in the antennas, they were able to suppress the radiation resistance in the loops and increase the efficiency. Even when placed 18 cm (7 in) apart, the power transfer efficiency remained high at over 80%.
“We wanted to balance effectively transferring power with the radiation loss that always happens over longer distances,” said Nam Ha-Van, lead author of the study. “It turns out that when the currents in the loop antennas have equal amplitudes and opposite phases, we can cancel the radiation loss, thus boosting efficiency.”
The team says the new technique allows them to analyze, both in theory and in practice, any wireless power transfer system, allowing them to be optimized to maximize their efficiency. This could help usher in that useful future of devices that effectively self-charge over the air, without needing purpose-built rooms.
The research was published in the journal Physical Review.
Source: Aalto University
