Imagine if the smartphone in your pocket, gamepad in your hand, or watch on your wrist could charge wirelessly. No cables, no wireless charging pads. Just wireless power beamed through the air by a router, much like Wi-Fi. The potential benefits for medical devices, sensors, cameras, and a host of other battery-powered gadgets are easy to grasp. Wires and cables are awkward, and batteries are expensive to produce and difficult to recycle.
I first saw wireless power, also known as distance wireless charging, in action seven years ago and was amazed. A small transmitter panel wirelessly powered a light bulb up to 30 feet away across the room. Since then, I’ve seen similar technology powering everything from E Ink displays to earbuds and smartphones. But working prototypes and reference products are one thing. It’s been more than a century since Nikola Tesla proved wireless power over distance was possible, wowing crowds by demonstrating a large transmitter coil powering distant incandescent electric lamps. Implementing that technology in consumer products we can buy is a whole different ball game.
After taking a backseat for years, the technology made a bit of a resurgence in 2021 and at the CES 2022 technology trade show. There's progress, but you still shouldn't expect distance wireless charging in many of your household goods anytime soon.
Signs of Progress
Last year, Motorola showed off a smartphone charging wirelessly up to 10 feet away from a transmitter and four smartphones charging simultaneously at closer range. Xiaomi and Oppo teased similar technologies. This year, Samsung’s Eco TV Remote made our Best of CES 2022 short list. Its predecessor relied on solar energy, but the new model adds radio-frequency (RF) harvesting. It grabs the radio waves bouncing around your home, emitted by devices like your Wi-Fi router, and converts them to energy.
Developed by Samsung’s research and development division, this technology was refined by the TV group as a part of a companywide drive to be more environmentally friendly. Instead of a battery inside the remote, there’s a super-capacitor that charges up to 80 percent capacity in just 10 minutes by combining solar and RF harvesting.
This innovation is clever and exciting, but it works only for small devices that don’t require much power. That’s why many players in this space target gadgets like E Ink displays for supermarket shelves, wearables, and internet-of-things (IoT) sensors. Most devices need considerably more power than a TV remote, making a dedicated transmitter (that's not your Wi-Fi router) essential.
“The key behind our Cota wireless power technology is that we can power devices at distance, control the power, and prioritize which devices get it, but we can also power devices in motion,” says Hatem Zeine, founder, president, and chief technology officer at Ossia, one of the most prominent names in distance wireless charging.
Ossia announced a partnership with tablet maker Archos at CES 2022, showing off concepts for distance charging a smartwatch, camera, and SOS button to help care for the elderly. The idea is that wireless power can keep these monitoring devices charged to track the wearer 24/7. Ossia also unveiled the Cota table, powered wirelessly by a Cota panel on the ceiling, with Qi wireless charging pads and a battery inside (it can also host USB ports). The table is aimed at cafés and venues where running cables is tricky and the flexibility to change seating setups is prized.
The Cota system delivers a few watts of power at close range but drops down to milliwatts with distance and stops being meaningful at around 30 feet. Efficiency is a thorny issue, as there’s a large discrepancy between the power you spend and the power you recover. There are three parts to this: converting power from the outlet to RF, transmitting and receiving RF waves, and converting RF to direct current in the receiving device. Several variables make it tough to arrive at definitive figures, but for the percentage of power recovered, we’re talking about efficiencies in single digits up to high teens at best.
“One AAA battery may cost 50 cents and provide you with one watt-hour of energy,” Zeine is quick to counter. “If you buy power from the wall socket, you're buying one kilowatt-hour of energy for 10 cents, so a battery is 5,000 times more expensive.”
It’s a strong argument. The price of lithium is soaring because of battery demand. To realize the promise of IoT, we need an alternative to batteries, and wireless power could conceivably be it.
Safety and Certification
All these technologies have a handshake process between the transmitter and receiver that cuts off the radio frequency beam if an obstacle—like a person—gets in the way. Companies are required to jump through hoops for Federal Communications Commission certification to prove their technology is safe, but this is granted on a per-device basis following practical tests conducted by an independent third party (one reason why research moves at a very slow pace). The lack of a common standard is another stumbling block. Consider how long it took for the Qi standard to win out and become ubiquitous in the closer contact wireless charging scene.
But a decade on, Ossia has little to show beyond concepts. After I asked where its technology is in use today, Zeine tells me that Walmart is piloting Cota in distribution centers for inventory tracking and asset management. Toyota is testing its viability to replace wiring in cars, where it could power sensors and make replacing them easier. The partnership with Spigen (announced at CES 2019) to develop wireless charging phone cases has yet to bear fruit.
It’s a similar story with Energous, which has announced an impressive range of partnerships and demonstrated its WattUp technology many times but has yet to reach consumers. Technovator hasn’t gone to market. Witricity pivoted into electric vehicles. Powercast was one of the first companies to release a consumer device, a wireless charging grip and transmitter for Nintendo Switch Joy-Con controllers, but it costs $150 and has a range of only around one foot. A killer product to drive adoption remains elusive.
GuRu, the company behind Motorola’s demo, might be a few steps ahead of its peers. It employs RF lensing to send focused beams from a generating unit (Gu) to a recovery unit (Ru). Ali Hajimiri, GuRu's cofounder and chief scientific adviser, shows me a pair of tiny chips with built-in antennas about the size of a Lego block and says the company has developed flexible materials that enable the technology to work in different types of devices.
“We are the only company that can do multiple watts of power to multiple devices at multiple meters, at the same time,” Hajimiri says.
I first met GuRu at CES 2020 to see Rovi, a mobile transmitter resembling a robot vacuum that moved to charge different devices, getting close enough to beam a useful amount of power. The company has made progress since then. Its technology combines an integrated ASIC (application-specific integrated circuit), an intelligent algorithm that can focus energy rapidly and efficiently in a small spot, and, crucially, a higher frequency to deliver more power at a longer range.
Most of these technologies started out at the 2.4-GHz frequency we are familiar with from Wi-Fi, and that’s also the frequency that charges up Samsung’s new remote most effectively. Energous uses the 915-MHz frequency, and Ossia is transitioning to 5.8-GHz with its Cota technology. A part of GuRu’s secret sauce is its ability to operate at 24 GHz. This jump doesn’t just mean more power and longer range, it also allows for smaller transmitters and receivers. A generating unit the size of a smartphone can charge an earbud over a distance of several feet.
“It's like a magnifying glass where you can focus energy in one spot, but that spot can move, and you can make multiple spots,” Hajimiri says.
Chicken and Egg
This need for transmitters and receivers embedded into our products hampers the early adoption of wireless power over distance. It sounds convenient, but who will spend hundreds of dollars on a power router that supports a limited range of devices or requires another retrofit add-on to work?
“I think a good analogy for this technology is Wi-Fi,” Hajimiri says. “In the early days, you had to buy this big, clunky PCMCIA card to put in your laptop, and a lot of people would say, ‘I would never use Wi-Fi because my ethernet cable is 100 times faster.’”
Wi-Fi has improved enormously, and we accept a performance hit for the convenience of going wireless. Power could follow the same trajectory, and there are other potential benefits.
“As wireless connectivity became ubiquitous, it not only changed the way we connect, it changed the nature of storage,” Hajimiri says. “You no longer had to carry all of your data with you; it moved to the cloud.”
For power over distance, that benefit is batteries. If you can get rid of batteries or make them smaller, you can drastically reduce the volume and weight of devices and realize new flexible forms. Reducing our reliance on batteries also counters some of the arguments made about the poor efficiency and potential wastefulness of wireless power.
It’s easy to get swept away with the potential of a wire-free future, but it’s hard to say how distant that horizon is. Realistically, we are still many years away from ubiquitous wireless power. While companies like Samsung and Motorola stepping in feels like real progress and will set a fire under competitors, proprietary technologies must do battle, standards will only slowly emerge, and there’s a long way to go before the name WIRED is anachronistic.
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