Power play: Wireless charging at a distance arrives
- 31 October, 2012 15:36
It feels a bit like being at a magic show, watching David Schatz hold a light or smartphone feet above a power pad to demonstrate how magnetic resonance wireless technology can charge any device over distance.
Schatz, director of business development at WiTricity in Watertown, Mass., can even show off the wireless "room of the future," where lamps, cell phones - you name it - can all be powered through the air, no matter where they are in the room.
WiTricity, however, won't be selling any of the wireless products it demonstrates. Instead, the company's future is in selling licenses for others to use its patented designs to build products. WiTricity has few, if any competitors, for its flavor of wireless charging, which it calls highly resonant wireless power transfer.
"They were one of the first to showcase this resonance wireless power transfer, which offers greater distances between coils versus inductive charging, which requires tight coupling between transmitter and receiver," said Jason dePreaux, a principal analyst for the Power & Energy Group at IHS Research. "My impression of WiTricity is that they're keeping it very open [for the market]."
China-based 3DVOX Technology claims it successfully developed a "3D Power System" in March 2012 that -- from a single 1.5-foot by 1.5-foot box -- can power an entire room full of electronics. The company claims its Widely Magnetic Field Launching and Focus Magnetic Field Receiving technologies are powerful enough to magnetically resonate power over many feet.
Inductive vs. resonance wireless charging
To date, products on the market have been built around magnetic induction charging techniques, which require that a mobile device be in contact with a charging surface, such as a charging pad. The leading charging pad supplier has been Duracell's Powermat technology.
Resonance charging like WiTrcity's allows an enabled device to be placed up to several feet away from a power source for charging.
Resonance charging is based on the same transmitter/receiver coil technology as magnetic induction, but it transmits the power at a greater distance. So, for example, a mobile device could be charged when laid next to a laptop with resonance charging capability or, in the case of WiTricity, it could be charged from feet away.
Lots of possibilities
The consumer product possibilities are endless for WiTricity's technology, from office desks and kitchen cabinets with embedded wireless chargers to pads buried in concrete that can charge electric cars parked in home garages and parking lots. WiTricity has even built a receiver for a solar panel, which eliminates the need to have any wires pass through a roof.
Imagine a wireless television, fed both power and media content (using Bluetooth) wirelessly. WiTricity has one.
Medical devices could also be powered with the technology WiTricity offers. For example, artificial heart pumps today must be hardwired to a battery pack worn by a patient. Wireless charging could be less invasive, helping to avoid infections in the areas where wires pass through a patient's skin.
During a recent visit to WiTricty by Computerworld, Schatz demonstrated how a new prototype wireless charger called "Prodigy" can power a device from about 10 inches away. The black, oval-shaped Prodigy charger looks much like any charging pad told in stores today and sells for $995. It is essentially a demo kit for engineers, researchers and entrepreneurs who would use it to develop their own charging products.
Schatz showed how a black rubber pad he called a "repeater" can boost a charging signal to make charging over greater distances viable. (The charging distance with a repeater is about two feet.)
Just like the powered wireless charger, the rubber repeater has a copper coil embedded in it, but its coil is passive -- it doesn't have to be plugged into anything. "Repeaters are a structure that allows the energy to hop over distance without have to add any energy to it," Schatz explained.
While the copper coils embedded in repeaters today are made of wire, Schatz said they the coils can also be printed on a flat sheet like any printable circuit. WiTricity has already produced printed coils and demonstrated them in smartphones without adding any thickness to the device. The printed coils can also be used in household products as common as shelf paper in a cabinet.
Using a wire-based, shelf-paper repeater, Schatz demonstrated how under cabinet lighting could be installed without wires, or how commercial soap products, such as Tide laundry detergent boxes, could be illuminated from within to draw a shopper's attention in a store.
WiTricity's technology can also charge directly through solid objects, such as wood or Formica surfaces. To demonstrate, Schatz held a charging pad beneath a wooden conference table, proving it could power a light atop the table. It is this technology that holds the promise of wireless charging embedded in desks and other furniture.
The wireless charging market
A recent report from Pike Research estimates that worldwide revenues from wireless power devices will exceed $15 billion by 2020, and that systems based on highly resonant wireless power transfer will account for more than 80% of the total market. WiTricity holds the fundamental patents related to highly resonant wireless power transfer in its portfolio of over 270 granted and pending patents worldwide.
Both magnetic induction and magnetic resonance charging use copper coils: a transmitter coil and a receiver coil. Alternating current in the transmitter coil generates a magnetic field, which induces a voltage in the receiver coil.
WiTricity's main competitors are companies such as Duracell, with its Powermat technology, as well as products that carry the relatively new Qi certification. While Qi products are limited to wireless power pads and near-proximity resonance charging, they do allow multiple devices to be charged on a pad at the same time, regardless of positioning.
For example, Qi-certified wireless charging vendor Fulton Innovation has power pads that accept up to three devices anywhere on a charging pad using magnetic inductive technology.
"And, I have to place a device very precisely on a charging pad. If it's off by 5 millimeters, it doesn't work," Schatz said, referring to Qi-standard products.
The Qi (pronounced "chee") standard was developed by the Wireless Power Consortium (WPC). Qi, which enables inductive or pad-style charging and short-distance (1.5cm or less) magnetic resonance charging, is widely supported by more than 120 companies who've been developing certified products. The list reads like a who's who of electronics, from LG Electronics and Sony Corp. to Nokia and Verizon Wireless.
Schatz believes Qi-certified products will not catch on because there's little advantage to charging a smartphone or other mobile devices on a pad or over miniscule distances. "They've been trying to push that technology for a few years," he said. "Go to a store and buy a charging pad, and you'll see that it's not really all that useful."
But Qi is not the only wireless charging specification out there.
The Alliance for Wireless Power (A4WP), backed by Qualcomm and Samsung, this week said its technical working committee has approved a more flexible wireless power specification that will allow consumers to charge their mobile devices on a variety of compatible surfaces using inductive and short-distance resonance wireless charging.
A4WP claims the specification will make it easier to charge electrical devices embedded in furniture, machines and vehicles. The technology comes from Qualcomm's acquisition earlier this year of a company named WiPower. WiPower claims its wireless charging has a longer range than Qi: up to 45mm, or about 1.7 inches.
The Qi standard wireless AC transmits to a device at a distance ranging from 5mm to 40mm (about 1.5 inches) from the power source.
Yet another wireless charging vendor, New Zealand-based Power by Proxy, today announced it acquired the key wireless power patent portfolio from the University of Auckland via its commercialization company UniServices. The portfolio includes 122 patents for portable consumer electronics devices, semiconductors and batteries.
Power by Proxi's co-founder and CEO Greg Cross said devices using the Qi specification require precise placement on a charging pad, while his company's "loosely-coupled" wireless technology allows multiple devices to be recharged at the same time, regardless of the position on an induction pad.
Unlike other wireless charging vendors, Power By Proxi got its start four years ago selling large-scale systems for commercial industries such as construction, telecommunications, defense and agriculture. For example, one product is a wireless control system for wind turbines. "As we've started to work with market analysts over the last couple of years, there's an increasing recognition that the potential size of the industrial components market is at least as large as products in the consumer electronics market," Cross said.
Power by Proxi is now focusing efforts on the retail market with miniaturized devices that fit inside a AA battery.
In contrast, WiTricity's technology offers charging from feet away.
To date, few companies have offered wireless charging at distance. In 2008, Intel Labs demonstrated chip technology that could wirelessly charge mobile devices. Intel's Wireless Charging Technology (WCT) would let a user charge a smartphone wirelessly from a notebook PC by placing it right next to the device. Last month, Intel announced a partnership with Integrated Device Technology Corp. (IDT) to develop chipsets for WCT products. Products using the chipsets are expected to arrive in 2013, Intel said.
Fujitsu had also announced it would be shipping magnetic resonance-based wireless charging systems this year. This week, however, a Fujitsu spokesperson said there was nothing new to report on the technology.
Menno Treffers, chairman of the Wireless Power Consortium, said that, in general, the distance a wireless charger can emit power roughly mimics a charging coil's diameter. So, for example, a 10-inch coil would be able to charge a device up to 10 inches away.
According to Treffers, charging capability "drops off a cliff" beyond a distance equal to the size of the coil. Power by Proxi's Cross agrees, and even said anyone trying to sell a room full of wireless power or saying it will be as ubiquitous as WiFi is being "dishonest."
"We don't think it's an efficient use of power or a safe use of power," Cross said. "We don't think it will be possible for a whole bunch of reasons: the size of the coils required to broadcast power at long distances, the levels of efficiency will quickly drop down to 10% or less. You can broadcast wireless power over six feet, but the amount of power received will be less than 10%."
Schatz, however, scoffed at naysayers.
For example, another of WiTricity's charging kits for developers -- the WiT-2000 -- is designed to transfer energy over distances ranging from less than a centimeter (directly on the surface of the charging pad) to distances totaling several tens of centimeters.
"We can demonstrate where a 10 centimeter coil can operate over 20, 30, 40 centimeters," Schatz said. "He is correct that when things are closer together they can be a bit more efficient, but they can still be efficient enough and very useful when they're at a longer distance."
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