Meredith Perry has bold ideas.

For starters, there’s her notion to replace intercity car commuting with rides on small personal blimps. Then there’s her idea to mix shampoo with a material used to waterproof electronics, so that you don’t need an umbrella when it rains.

But perhaps the boldest – and most controversial – is Perry’s attempt to wirelessly charge electronics, such as cellphones, using ultrasonic waves sent through the air.

That idea is being tackled by the 26-year-old’s Santa Monica startup, uBeam Inc., which has raised millions in funding from a number of big-time venture capitalists, including Menlo Park’s Andreesen Horowitz, Santa Monica’s Upfront Ventures, Peter Thiel’s Founder’s Fund as well as billionaire Mark Cuban and Yahoo Inc. Chief Executive Marissa Mayer.

However, despite being lauded as the next big thing in energy technology, the feasibility of uBeam’s plan is increasingly plagued by skepticism.

Converting ultrasonic waves into electrical energy is rudimentarily possible – and indeed not novel – experts say, but absent a technological breakthrough, they are doubtful it can perform as uBeam claims.

“It seems like an ungodly inefficient way to transmit energy,” said Leonard Bond, a physicist and professor of aerospace engineering at Iowa State University, who noted nothing could be deemed impossible until uBeam showed a working cellphone prototype, which it has not done. “Maybe these guys get an amazing award for having done something, but I’m not convinced yet.”

Despite such obstacles, uBeam has raised $23.2 million from investors. The company is ramping up to manufacture millions of units and will ship a product by the end of next year, said Perry in a September interview with the Business Journal. Perry previously said uBeam would be available in fall 2011 and also in spring 2013.

Unfortunately for uBeam, it is now working in the shadow of the recent Theranos Inc. debacle, and rightly or wrongly is being compared to it.

“It reminds me of other cases. There is this company Theranos,” said Bernard Boser, a professor of electrical engineering and computer science at UC Berkeley.

Palo Alto’s Theranos said it could detect a wide range of diseases with just a drop of blood, claims which attracted more than $400 million in investment and a valuation of more than $9 billion. However, citing a need to protect proprietary technology, the company refused to submit its work to a peer-reviewed medical journal. Last month, the Wall Street Journal reported a gap between what Theranos claimed publicly and the actual, dismal performance of its technology.

“I was very surprised about their claims,” said Boser about Theranos. “How could they possibly do that? Now we know they can’t.”

Resistance

Yet Perry, who holds a bachelor’s degree in paleobiology from the University of Pennsylvania, remains unambiguously confident.

“UBeam will be there just like you see free Wi-Fi in windows as you walk by shops,” said Perry in a USA Today interview in February. “It will be everywhere from your local coffee shop to the hotel to theaters to stadiums to airports. You name it.”

UBeam’s technology sends energy wirelessly through a multistep process.

Simply put, uBeam electrifies a crystal, which vibrates and creates ultrasonic waves that travel through the air, hitting another crystal fixed inside a cellphone case. The second crystal then turns the vibrations back into electricity. UBeam claims this system can generate at least 1 watt of electricity up to 15 feet away, enough to provide a trickle of electricity to an iPhone.

Ultrasound has been used to transmit energy before, said Henry Scarton, a mechanical engineer and director of the Laboratory for Noise and Vibration Control Research at Rensselaer Polytechnic Institute in Troy, N.Y. Scarton has built systems that project ultrasonic energy through metal submarine hulls to underwater listening devices and through oil-carrying pipe to sensors.

But under closely controlled conditions, those systems only generate a maximum of 50 percent efficiency, he said.

“In air, it would be ridiculously small. Not practical,” Scarton said.

Moving ultrasonic energy through air, rather than water, metal or even human flesh – as in medical exams – is inefficient, experts say.

Other factors, such as humidity – or denim pants pockets – could further reduce efficacy, experts say.

To generate a trickle of charging power, a large amount of electricity would have to be pumped into uBeam’s transmitter, explained Mike Bailey, a senior principal engineer at the University of Washington’s Center for Industrial and Medical Ultrasound in Seattle. “There’s a lot of loss in converting electrical energy to acoustic energy and then receiving it and converting it back.”

When the university’s engineers heard about uBeam’s approach to wireless charging a month ago, the concept sparked a discussion about a textbook exercise they teach their students, he added.

“There’s a problem in an acoustics textbook: How long would you have to yell at a cup of coffee to make it boil?” said Bailey. “It’s something like 10 years.”

Invention

Perry said she dreamed up wireless charging after being frustrated with the chore of plugging her laptop into an outlet during an undergraduate class in college.

“How does a palaeobiology major at Penn learn how to convert ultrasound into electricity? Well, I literally just Googled it,” said Perry in a 2012 Tedx speech, “How to Be a Technology Innovator Without an Engineering Degree or Asperger’s.”

Using Wikipedia and help from electrical engineers, Perry later produced a bulky proof-of-concept prototype that was demonstrated at the Wall Street Journal’s now-defunct All Things D tech conference in 2011. National media attention further helped Perry spin the idea into a venture capital-backed startup.

Yet, despite touting uBeam’s technology in numerous interviews since, Perry has yet to unveil a follow-up prototype or release much technical information. In fact, uBeam investor Cuban acknowledged to Fortune in July that he hasn’t seen a cellphone prototype.

When asked to address skepticism, even without disclosing product specifications, Perry declined to be interviewed by the Business Journal but sent a statement.

“Like most consumer electronics companies, we will not release product specs prior to launch,” Perry said in that statement. “We look forward to sharing our product details at launch when the world can experience the power of uBeam.”

Public statements and patent filings show uBeam is trying to combat efficacy problems. The startup is trying to build technology to concentrate and direct an ultrasonic beam at a cellphone receiver being tracked within the room, meaning the beam would only transmit when a clear line of sight is established.

That type of system would be complex, said the University of Washington’s Bailey.

“What if you’re sitting in front of your phone or there is a table?” he asked. “Do they have a bunch of these (transmitters) around the room that can focus and find a clear path? It seems pretty farfetched.”

UBeam’s larger problem might be the expense of manufacturing such a complex ultrasound system for price-sensitive consumers, said Pierre Mourad, senior principal physicist at the university’s Center for Industrial and Medical Ultrasound.

“If it’s only a trickle charger, who’s going to buy it? I’m less worried about the tech, more worried about cost problems,” said Mourad, who also teaches an entrepreneurship class. “To make 10,000 or 100,000 (units), can they do it in a way where the costs of goods support their business model?”

Costs might also bleed into consumers’ power bills, because uBeam’s inefficiency could be a problem for the electrical grid, said Berkeley’s Boser.

“If we adopted that for all of our electronic devices that would create a huge problem, because that would mean we would have to build a gazillion new power plants,” he said.

Without more information, he said the public is hard pressed to assess uBeam’s claims.

“It’s very difficult to say something is impossible,” he said. “It sure would be nice if they had a little bit more solid evidence that what they are trying to do works.”

Technology reporter Garrett Reim can be reached at [email protected]. Follow him on Twitter @garrettreim for the latest in L.A. tech news.