Researchers developed room-scale wireless charging technology that aims to power lights, phones, laptops without wires.
Wireless power transfer techniques are scaling up and freeing devices from charging cords and cables. But wireless charging uses potentially harmful microwave radiation or required devices to be placed on dedicated charging pads. Researchers from University of Michigan and University of Tokyo have developed a system to safely deliver electricity over the air, potentially turning entire buildings into wireless charging zones. The system uses a conductive surface on room walls and a conductive pole to generate magnetic fields.
The developed technology can deliver 50 watts of power using magnetic fields. Study author Alanson Sample, U-M professor of computer science and engineering, says that in addition to untethering phones and laptops, the technology could also power implanted medical devices and open new possibilities for mobile robotics in homes and manufacturing facilities.
“This really ups the power of the ubiquitous computing world—you could put a computer in anything without ever having to worry about charging or plugging in,” Sample said. “There are a lot of clinical applications as well; today’s heart implants, for example, require a wire that runs from the pump through the body to an external power supply. This could eliminate that, reducing the risk of infection and improving patients’ quality of life.”
Researchers from the University of Tokyo demonstrated this technology in an aluminum test room measuring approximately 10 feet by 10 feet. They wirelessly powered lamps, fans and cell phones that could draw current from anywhere in the room regardless of the placement of people and furniture.
 “Something like this would be easiest to implement in new construction, but I think retrofits will be possible as well,” said Takuya Sasatani, a researcher at the University of Tokyo and the corresponding author on the study. “Some commercial buildings, for example, already have metal support poles, and it should be possible to spray a conductive surface onto walls, perhaps similar to how textured ceilings are done.”
The technology involves lumped capacitors placed in wall cavities for generating a magnetic field that resonates through the room, while trapping electric fields inside the capacitors themselves. One of the challenges was that magnetic fields tend to travel in circular patterns, creating dead spots in a square room. In addition, receivers need to align with the field in a specific way to draw power.
“Drawing power over the air with a coil is a lot like catching butterflies with a net,” Sample said. “The trick is to have as many butterflies as possible swirling around the room in as many directions as possible. That way, you’ll catch butterflies no matter where your net is or which way it’s pointed.”
To implement that, the system generated two separate 3D magnetic fields. One travels in a circle around the room’s central pole, while the other swirls in the corners, traveling between adjacent walls. This approach eliminates dead spots, enabling devices to draw power from anywhere in the space.
The researchers comment that implementation of the system in commercial or residential settings is likely years away. But this system can pave the road for wireless charging in houses, and even structures like factories or warehouses.
The research appeared in the journal Nature Electronics.
