UBeam went onto further claim that its technology can transfer energy through the air to a device comparably or faster than a wire.
“I find that hard to believe,” said Robin Cleveland, an Oxford University professor of engineering science and PhD in mechanical engineering. “It’s going to be very hard to put that sort of power to a cellphone through the air. Almost anywhere wireless tech is going, I find it very hard to compare against a direct copper wire connection.”
Moreover, even at uBeam’s minimum charging claim of 1.5 watts - a trickle charge for an iPhone - energy losses would likely be large, he said.
“It’s not going to be environmentally green because much of the energy will be lost in the air and not converted into power in the cellphone,” said Cleveland. “I just don’t think the numbers work.”
“It will be interesting if they ever open the kimono and let us have a look inside,” said Leonard Bond, a physicist and professor of aerospace engineering at Iowa State University. “It seems a very inefficient way to do it. Maybe they have some magic to do it.”
In order to hit a cellphone with an ultrasonic beam while it moves through a room, Perry told TechCrunch that uBeam is trying to build a device tracking and beam-focusing technology. That means an intense beam would only transmit when a clear line of sight is established.
But such a system would still have functionality problems, as well as complexity and cost issues, say experts.
“You’d have to align the transducer very much into the beam because if it’s not well-aligned you’re going to have problems. The bulk of the energy is going to reflect off the case,” said Bond, who was also once the editor of the journal “Ultrasonics” and is a board member on the International Congress of Ultrasonics. “They’re going to an awful lot of trouble to generate this 1.5 watts of electricity to charge a cellphone.”
Furthermore, if uBeam’s receiver is not perpendicular to the ultrasonic beam, additional energy would fall out of focus and be wasted, experts said. In the TechCrunch blog post, uBeam also acknowledged it could not transmit through cloth or human flesh, meaning it would have difficulty charging a cellphone in your pocket or in hand.
“Presumably, the receiver surface is on the back of the phone where your hand is, so that’s going to cover that up,” said Pompei.
In essence, it appears an uBeam-equipped cellphone could only receive a trickle charge while flipped face down in your hand or on a table. That might make the system less useful than a PowerMat or Qi near-field wireless charging system, which charge face up.
Pompei said he sympathizes with all the skepticism Perry and uBeam are receiving, as his own ultrasonic technology was once doubted by experts. Pompei said he answered those skeptics with a live demonstration and by submitting a paper on his technology to a peer-reviewed journal.
“I didn’t have to show the inner workings, but I demonstrated that it worked,” he said. “You have to do that. You can’t go on for years and make all sorts of claims and not back it up with a real demonstration.”