Someday fleets of shared autonomous cars will shuttle passengers rapidly around cities, picking them up and dropping them off without the need for parking lots, garages, or even personal vehicles. But without a place to sit and charge, or the time to do it while individual owners are at work or at home asleep, how will these vehicles get the energy they need to do their jobs? Who will feed the robot cars?
“There’s no one to plug them in. There’s no driver. They need to be able to go on demand, charge themselves as the batteries get low,” says Alex Gruzen, CEO of the Massachussetts-based wireless charging company WiTricity.
Over the last eight years, WiTricity has shifted its business model from consumer electronics and phone chargers to focus almost exclusively on the question of how we power cars. The answer, according Gruzen, features power transmitted through the air, via a system built into the cityscape. Toward that eventual end, WiTricity has partnered with BMW to release the first consumer-ready remote charging system for an electric vehicle.
This type of charging, which happens via a process called magnetic resonance, dates back to the mid 2000s, when Marin Soljačić, WiTricity’s founder and an MIT physics professor, decided to invent a better way to charge a phone. He experimented with several ways of moving energy, including radio frequency, ultrasound and even induction, before settling on magnetic resonance as the best combination of efficiency and convenience. He applied for a patent in 2006, which he ultimately received in 2010, and started WiTricity in 2007 to help the cell phone industry make the charging mats compatible with some phones. (You can even buy one from Tesla, though the company has not yet announced any plans to charge their cars this way.)
Resonance isn’t unique to electrical charging; it’s the same phenomenon that describes the oscillation of a child on a swing, and its transition back and forth between potential and kinetic energy. A parent pushing, or a kid pumping, can contribute energy to the system—but only if they move at the right frequency and in the right direction. Similarly, an electromagnetic coil can transfer energy to another, provided they are in the same orientation and resonate at a matching frequency.
As the years passed, WiTricity—the only licensee of the technology—partnered with more and more companies to develop it. Many were aimed at consumer electronics, but Toyota licensed it for the Prius hybrid and eventually invested in WiTricity, and Honda, Hyundai, Nissan and GM all worked on prototypes. BMW’s 2018 530e iPerformance, though, is the first to hit the market, offering a luxury package with a wireless charging mat to German buyers (with plans for release in the U.S., U.K., Japan, and China) at around 3,000 Euros.
But the 530e is a hybrid, points out Dominique Bonte, an auto industry analyst with ABI Research. It’s got a small, 9.2 kWh battery, one that can be charged in a couple hours via WiTricity technology, but has just a 16-mile range. Wireless charging, even at the 90 percent efficiency that WiTricity has been able to achieve, is still relatively slow. Look at Tesla, for example: A Model S comes with either a 100 or a 75 kWh battery, and the WiTricity system puts out somewhere around 11 kW, which means it could take an entire day to fully charge a Tesla. Thus, the company has chosen to focus on its Superchargers, which can deliver a much faster charge.
“You cannot support the same power transfers wirelessly and with fixed charging stations,” says Bonte. “That’s not going to change, they kind of admit. It will go a little higher, maybe 20, 30 kW, but it won’t support 50 to 60 kW. That’s not even foreseen in the standard.” However, he also points out that the vast majority of EV usage would not require a full charge each night — full batteries are only really required for long trips.
Still, a shift is happening in the auto industry, says Gruzen, thanks in part to VW’s diesel car emissions cheating scandal, the dropping costs of batteries, and Tesla making EVs sexy. “All these things come together, and right now what you’re seeing is an extraordinary race among all the automakers to commit to a breadth of electrified platforms,” says Gruzen. “The market is taking off.”
WiTricity isn’t as alone as their hundreds of patents might suggest. (In 2014, the company received a patent for the wireless energy transfer technology as it pertains to vehicles.) A company called Plugless Power is making aftermarket charging mats, featuring a magnetic coupler that gets installed on an off-the-shelf EV. And Qualcomm’s Halo uses an inductive charging akin to that in an electric toothbrush that is functionally similar to Witricity’s version despite using different technology, and is pursuing dynamic charging to charge vehicles in motion.
But it’ll take more than automakers and their suppliers to get consumers to change their behavior, as many of the trepidations they have for electric vehicles are still present. Range anxiety has driven the push for bigger batteries, and the need for rapid charging. But distributed charging throughout the cityscape could alleviate that, and government-mandated phasing out of combustion engines could force the issue. “For us to really have a big impact on the environment, we need way more than just early adopters to be buying electric vehicles,” says Gruzen. And to do that, charging has to be easier than refueling. It’ll start with a mat in your garage, he says, but it’ll end with magnetic resonance charging being integrated into public parking, taxi queues, and just about anywhere a car can take a break for a quick “power snack.”
More important is the city level, when fleets are shared and wireless and autonomous, and when any down time is lost business. WiTricity and Qualcomm are already working with SAE (know as the Society of Automotive Engineers) on a set of global standards that will allow cars from different manufacturers to charge via different wireless systems. This will even enable fleets to act as battery banks, storing energy for the city and distributing it back as power needs vary throughout the day.
“In such an environment, in such a car-as-a-service environment, wireless charging would actually almost become a necessity,” says Bonte.