The days of scrambling around for a phone charger could soon be over. Instead, gadgets using everything from ultrasound to magnetic fields could beam power through the air as people keep their smartphones tucked tightly in their pockets.
"We’re at the beginning of the mass market adoption phase for wireless charging technology right now," David Green, a wireless power researcher for IHS Technology, told NBC News.
Last year, around 55 million wireless charging receivers — which let consumers take advantage of wireless chargers — were sold, according to IHS. In 2015, the research firm expects that number to triple.
Yes, wireless charging has existed for a while. Gadgets like Duracell's Powermat use inductive charging, the same technology that powers electric toothbrushes. It works, but phones need to be aligned perfectly on top of the device, making them not much more convenient than traditional chargers.
Now, companies like uBeam, WiTricity, Energous and Ossia are fighting to replace inductive charging with technology that gives smartphone users a lot more freedom.
Dorm room inspiration
Meredith Perry came up with the idea for using ultrasound to power devices in 2011 while she was a student at the University of Pennsylvania. Now based in Los Angeles, Perry and her team at uBeam have made her initial vision into something real.
"I was standing in my dorm room holding my 15-foot laptop charger," Perry told NBC News. "I thought, 'This is annoying, why does my laptop require this enormous wire?'"
Her solution was something called ultrasonic transduction. A transmitter converts power from an outlet into ultrasonic sound waves, which travel through the air until they hit a receiver, and those sound waves are converted back into electrical energy.
The end result is the ability to charge a smartphone outfitted with a special case from 15 feet away. Put a transmitter in a living room or the local coffee shop, and people could keep their batteries full without even thinking about the device in their pocket.
The company has already raised millions from top venture capital firms like Andreessen Horowitz. It plans to release a smartphone case for consumers "within the next calendar year," according to Perry.
And in five years? Her prediction: "Every device, from your smartphone to your tablet to your flat-screen TV, will be powered by uBeam."
WiTricity is hoping that magnetic fields beat out ultrasonic sound waves. It was founded in 2007 to market a method of magnetic resonance charging developed by a group of MIT scientists.
"I like to use the analogy of an opera singer and a wine glass," Grant Reig, senior product manager at WiTricity, told NBC News. "The opera singer sings at a very specific note, and a wine glass filled with liquid might shatter at that specific note because you hit the resonant frequency."
Instead of a singer and a wine glass, WiTricity's technology involves a transmitter that induces an oscillating magnetic field at a specific frequency. A receiver tuned to that frequency then converts that magnetic field into an electric current.
Attached to the bottom-side of a table, a transmitter could rapidly charge a laptop and phone no matter where on the table they were placed.
In fact, the technology can transmit so much power so quickly that WiTricity is working with automakers on a transmitter that could be installed in garages, letting people wirelessly charge their electric vehicles.
With mobile devices, an extra millimeter would have to be added to integrate the company's receiver — no small change considering the iPhone 6 is only 6.9 millimeters thick. Convincing smartphone makers that its method of magnetic resonance charging is worth the effort could be the key to WiTricity's success.
"I would love to see it flood the market instantaneously," Reig said. "A lot of it is going to come down to the device manufacturers and market demand."
The future of power
Right now, inductive charging is the most mature wireless charging technology, used by everyone from Samsung to Ikea. There are two major players in this game: Qi, backed by an organization called the Wireless Power Consortium (which includes such members as LG and Toshiba), and Duracell's Powermat.
It's not clear which technology will overtake it. The ultrasound method from uBeam might not transmit tons of power, but it's always working in the background, so there is no need to think about it as you watch Netflix on the couch.
WiTricity's magnetic resonance charging is more powerful, but has less range, meaning you still have to think about where your phone is placed. There is also radio frequency technology from Energous and Wi-Fi charging from Ossia. All of them promise the ability to charge from a distance.
It's a pretty good bet, Green from IHS said, that something will replace what exists now, possibly as soon as 2019. By then, he said, around 30 percent of devices should support both inductive and some kind of magnetic resonance charging. A major move by Apple could go a long way in settling which technology becomes the industry standard. Not that ordinary people are watching too closely.
"The consumer doesn’t care what technology is used," Green said, "they just want it to work correctly the first time they try it."