Researchers have developed a system to safely deliver electricity over the air, potentially turning entire buildings into wireless charging zones. The technology can deliver 50 watts of power using magnetic fields.
In addition to untethering phones and laptops, the technology could also power implanted medical devices. Heart implants, for example, require a wire that runs from the pump through the body to an external power supply. The new technology could eliminate that, reducing the risk of infection and improving patients’ quality of life.
The technology could also open new possibilities for mobile robotics in homes and manufacturing facilities. The team is also working on implementing the system in spaces that are smaller than room-sized; for example, a toolbox that charges tools placed inside it.
The team demonstrated the technology in a purpose-built aluminum test room measuring approximately 10 feet by 10 feet. They wirelessly powered lamps, fans, and cellphones that could draw current from anywhere in the room regardless of the placement of people and furniture.
The system is a major improvement over previous attempts at wireless charging systems, which used potentially harmful microwave radiation or required devices to be placed on dedicated charging pads. Instead, it uses a conductive surface on room walls and a conductive pole to generate magnetic fields. Devices harness the magnetic field with wire coils, which can be integrated into electronics like cellphones. The system could easily be scaled up to larger structures like factories or warehouses while still meeting existing safety guidelines for exposure to electromagnetic fields.
The innovation could be implemented in new construction; however, retrofits also would be possible. 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 applied.
A key to making the system work was building a resonant structure that could deliver a room-size magnetic field while confining harmful electric fields, which can heat biological tissues. The team’s solution used devices called lumped capacitors. Placed in wall cavities, they generate a magnetic field that resonates through the room while trapping electric fields inside the capacitors themselves. This overcomes a limitation of previous wireless power systems, which are limited to either delivering large amounts of power over a few millimeters or very small amounts of power over long distances.
A second hurdle was how to generate a magnetic field that reaches every corner of the room — 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.
To make that happen, the system generates 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.
Tests with anatomical dummies showed that the system could deliver at least 50 watts of power to any location in the room without exceeding FCC guidelines for electromagnetic energy exposure. It is likely, however, that it will be possible to deliver higher levels of power with further refinement of the system.
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