'Charging room' system powers lights, phones, laptops without wires
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.
Study abstract: Room-scale magnetoquasistatic wireless power transfer using a cavity-based multimode resonator
JOURNAL
Nature Electronics
High-power wireless vehicle charging technology licensed by HEVO
IMAGE: ORNL HAS LICENSED ITS HIGH-POWERED WIRELESS VEHICLE CHARGING TECHNOLOGY TO HEVO, INCLUDING THE LAB’S UNIQUE, COMPACT POLYPHASE ELECTROMAGNETIC COILS THAT PROVIDE THE HIGHEST SURFACE POWER DENSITY AVAILABLE. view more
CREDIT: CARLOS JONES, OAK RIDGE NATIONAL LABORATORY/U.S. DEPT. OF ENERGY
The U.S. Department of Energy’s Oak Ridge National Laboratory has licensed its wireless charging technology for electric vehicles to Brooklyn-based HEVO. The system provides the world’s highest power levels in the smallest package and could one day enable electric vehicles to be charged as they are driven at highway speeds.
HEVO intends to work with ORNL to continue development of this critical technology to increase power levels and efficiency of existing charging techniques.
“Highly efficient wireless charging is a breakthrough technology that can alleviate EV range anxiety and facilitate the U.S. effort to decarbonize the transportation sector,” said Xin Sun, associate laboratory director for energy science and technology at ORNL. “We are excited to see another one of our technologies move into the private sector where it can create new green jobs and support the nation’s clean energy goals.”
The license covers ORNL’s unique polyphase electromagnetic coil that delivers the highest surface power density available, 1.5 megawatts (1,500 kilowatts) per square meter — eight to 10 times higher than currently available technology. This surface power density supports higher power levels in a thinner, lighter coil, resolving the issue of adding range-sapping weight to electric vehicles.
The license also includes ORNL’s Oak Ridge Converter, which eliminates one of the power conversion stages needed for wireless power transfer, resulting in more compact and less costly stationary infrastructure.
The ORNL technology enables very fast hands-free charging and even in-motion charging so vehicles could be reenergized as they’re driven at interstate speeds over specially equipped roadways.
Under the license, HEVO will work with ORNL to further develop the technology, including making it ready for commercial manufacturing.
In a recent announcement supporting deployment to the marketplace, Secretary of Energy Jennifer Granholm unveiled a DOE Technology Commercialization Fund award in which HEVO and ORNL will co-develop and demonstrate a 300-kW wireless charging system based on the ORNL converter and associated power electronics.
“EV charging must be simple, seamless and safe in order to accelerate mass adoption and prepare for an autonomous future,” said Jeremy McCool, HEVO founder and CEO. “Our collaboration with ORNL utilizes HEVO’s strength in designing, developing and commercializing wireless charging technology and software as the first and only company in the world that is compliant with both SAE and UL safety and performance standards.”
“Together, we are developing the fastest and most universal wireless charging platform in the world,” McCool added. “From only one device mounted on the vehicle, a driver will now have the advantage of wirelessly charging at all levels up to 300-kilowatts, powering their home through a vehicle-to-grid interface, and even charging while driving at highway speeds with grid-to-battery efficiency of 90-96.5%. All of this functionality is built into a vehicle-side package the size of a medium pizza box and the ready-made capability to charge electric vehicles without a human behind the steering wheel.”
DOE has set a goal to develop hands-free, automated wireless electric vehicle charging that is at least as fast as conventional refueling as it seeks to decarbonize the nation’s transportation sector. High-power charging also encourages buy-in by consumers concerned about driving range and the availability of charging infrastructure. In wireless charging, EV batteries are energized when vehicles are parked over a charging pad or driven over specially outfitted roadways while power is transferred across an air gap between magnetic coils embedded in the ground and installed on the car.
CAPTION
ORNL has licensed its high-powered wireless vehicle charging technology to HEVO, including the Oak Ridge Converter, which reduces the size and increases the efficiency of grid-to-vehicle power transfer infrastructure.
CREDIT
Carlos Jones, Oak Ridge National Laboratory/U.S. Dept. of Energy
Resolving range, infrastructure challenges
Enabling very high power levels is essential for practical charging.
Most of today’s commercially available light-duty EVs have battery packs rated anywhere from 30 kWh to 60 kWh, and most of the higher end, longer range electric vehicles come with 100 kWh battery packs. Reaching a 15-20 minute charge time for a 100-kWh battery pack requires a 300-kW charging system. Targeting an even faster 5-10-minute charge time means power must be scaled up to half a megawatt or more. Heavy-duty vehicles like electric semitrucks would require battery packs with several hundred kWh energy storage capacity, which would require megawatt-level charging, ORNL researchers noted.
“Opening up new parts of the transportation sector to electrification is a key benefit of this technology,” said Burak Ozpineci, section head for Vehicle and Mobility Systems Research at ORNL. “It’s not just about charging your vehicle really fast. It’s also about being able to convert to electricity long-haul trucks, which burn a significant portion of the vehicle fuel used in this country.”
The dynamic charging system being developed at ORNL likewise supports electrification of heavy-duty trucks. “Right now, those big trucks would require massive battery packs that add significant weight and cost to the vehicle,” said Veda Galigekere, who leads ORNL’s Electric Drives Research Group. “But with dynamic wireless charging on interstates, for instance, you can reduce the onboard battery capacity needed while alleviating range anxiety.”
The Oak Ridge Converter will be part of the TCF project and is included in the HEVO licensing agreement. It directly converts 60-hertz AC power from the grid to high-frequency AC without taking an intermediary conversion to DC power. The converter design reduces the weight, volume and size of stationary, grid-side infrastructure by as much as 50%.
“That means you could park another vehicle in the space saved in a city garage, for instance, and we would need less construction to embed charging pads under roadways or parking spots,” noted Omer Onar, leader of the ORNL Vehicle Power Electronics Research Group. ORNL also actively works on shielding technologies to ensure system safety and reduce interference with other vehicle components.
“With ORNL’s advancements, wireless charging is becoming more feasible, practical, and safe,” Onar said.
“The world of automotive is going to change faster in this decade than it has in the past century, and we need a step change in EV charging to unlock the full potential of this burgeoning multi-trillion-dollar industry,” said McCool. “We believe this is the leapfrog technology that will change people’s way of living and doing business across the globe. HEVO is excited to be at the forefront of this movement.”
The ORNL research and development team also includes Erdem Asa, Gui-Jia Su and Mostak Mohammad. The work was supported by the DOE Office of Energy Efficiency and Renewable Energy’s Vehicle Technologies Office and the ORNL Laboratory-Directed Research and Development program. Researchers used capabilities of the Grid Research Integration and Deployment Center and the DOE-designated National Transportation Research Center user facility at ORNL.
For ORNL licensing information, visit www.ornl.gov/partnerships.
UT-Battelle manages ORNL for Department of Energy’s Office of Science, the single largest supporter of basic research in the physical sciences in the United States. The Office of Science is working to address some of the most pressing challenges of our time. For more information, please visit energy.gov/science.
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