MIT researchers have made advances toward more efficient wireless power delivery. New research has shown that efficiency improves when multiple devices are charged at once, while individual devices could achieve less than 20 percent efficiency in power transfer, the scientists discovered charging two devices at once increased the combined efficiency to more than 30 percent. As more devices are added the efficiency should continue to rise, climbing toward a theoretical limit of 100 percent.
Although predicted by theory, the increase in efficiency when powering two devices at the same time had not been previously demonstrated in experiments. The team that carried out the recent work — Kurs, Moffat and Soljačić — found that when powering two devices at once, which individually could achieve less than 20 percent efficiency in power transfer, the combined efficiency climbed to more than 30 percent. The two receiving coils resonate with each other as well as with the transmitting coil, and help to reinforce the strength of the magnetic field. Kurs says that the efficiency should continue to rise as more devices are added, climbing toward a theoretical limit of 100 percent. The research has been funded by the NSF, the Army Research Office, DARPA, and a grant from 3M.
The amount of power transmitted in the latest experiment was on the order of 100 watts, but Kurs says that is only limited by the amplifier used for the transmitting coil, and can easily be increased. “It could be several hundred watts, or a kilowatt,” he says — enough to power several typical household devices at once, such as lamps, computers or television sets. “You could feed power to a medium-sized room, and power a dozen devices,” he says.