'Charging room' system powers lights, phones, laptops without wires


Date:
August 30, 2021
Source:
University of Michigan
Summary:
In a move that could one day free the world's countertops from
their snarl of charging cords, researchers have developed a system
to safely deliver electricity over the air, potentially turning
entire buildings into wireless charging zones.



FULL STORY ==========================================================================
In a move that could one day free the world's countertops from their
snarl of charging cords, researchers at the 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.


========================================================================== Detailed in a new study published in Nature Electronics, the 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. The team is also working on implementing the system in
spaces that are smaller than room-size, for example a toolbox that
charges tools placed inside it.

"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." The team, led by researchers at the University of
Tokyo, demonstrated the technology in a purpose-built 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.

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, the researchers
say. 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 cell phones. The researchers say 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.

"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."
A key to making the system work, Sample said, 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.



========================================================================== "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 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, travelling 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. Sample said it's likely, however, that it will be possible to deliver higher levels of power with further refinement of the system.

The researchers note that implementation of the system in commercial or residential settings is likely years away. They're currently working
to test the system in a building on U-M's campus. They'll implement
it as both a retrofit and new construction in a series of rooms that
use standard construction techniques, with a completion date set for
this fall.

The team also includes Yoshihiro Kawahara, professor of electrical
engineering and information systems at the University of Tokyo. The
research was supported by the Japan Science and Technology Agency and
the Japan Society for the Promotion of Science.

========================================================================== Story Source: Materials provided by University_of_Michigan. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Takuya Sasatani, Alanson P. Sample, Yoshihiro Kawahara. Room-scale
magnetoquasistatic wireless power transfer using a cavity-based
multimode resonator. Nature Electronics, 2021; DOI:
10.1038/s41928-021-00636-3 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/08/210830123220.htm

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