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In my Scientific American column this month, I tried to figure out what’s holding up distance-charging technologies, which purport to recharge your phone, tablet, watch, fitness band, and so on through the air.
Here’s a status snapshot of the companies leading the way.
PowerCast. Shipping FCC-approved distance charging products since 2010—for industrial use. Sends only microwatts or milliwatts (not enough to charge a phone). Device must remain stationary, placed in a predefined spot; the transmitter can’t follow it in space.
WiTricity. Uses magnetic resonance to charge the receiving devices; the company says that this technology is safe, capable of passing through stone, glass, concrete or wood, and can transfer power with the same efficiency, and in the same amounts, as a cable. Focused on charging pads for electric cars, having teamed up with companies like Toyota, General Motors, and Nissan, although its technology also powers a new Dell laptop that charges from a pad.
uBeam. Uses ultrasound waves, not radio waves, to send power to prototype consumer devices. The receiving gadget must have line of sight to the transmitter—not blocked by your body, clothing, or furniture. The company needs FCC approval, and former employees have described its technology as unworkable.
Ossia. An array of hundreds or thousands of antennas charges a device that you’re carrying or wearing anywhere in the room. Your phone (for example) sends 100 “beacon” signals per second, which lets the antennas locate it. The transceivers then send power back along the same pathways, bouncing off of floors, ceilings, and walls if necessary (no line of sight required). The company says it expects to get FCC approval, and has equipment-makers signed up as customers.
Energous. This system works much like Ossia’s, except that the gadget’s Bluetooth circuitry identifies its position in the room. The transmitter’s array of antennas sends a “pocket of energy” to the device. The company says that it can provide a phone in the middle of the room with, at best, a “trickle charge.” Energous expects FCC approval for its desktop “midfield” transmitter (two- or three-foot range, ideal for cordless keyboards and mice) by the end of 2017.