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Wireless charging: the key to unlocking an electric vehicle revolution

plugless system
Look, ma, no plugs.
Plugless

Radical changes are coming to transportation.

Earlier this month, I wrote a post about three ongoing technological revolutions — vehicle electrification, autonomous (self-driving) vehicles, and distributed energy — that are going to intersect in powerful ways.

Since then, I've become convinced that I should have included a fourth: wireless electric vehicle charging (WEVC).

Getting rid of plugs and cables doesn't get nearly the hype of the other three trends, but it's a necessary precursor to unlocking their full potential. And it is a lot closer than most people realize.

Why we need wireless charging for electric vehicles

Consumers, most of whom are still fairly unfamiliar with electric vehicles, have certain anxieties about them.

One, so-called "range anxiety," is the worry that batteries won't carry them as far as they want to travel (or might want to travel — one never knows).

The other is the hassle of plugging in the car every night. For people in apartments or condos, there may not be outlets. And even for people with garages, it's still kind of a pain in the ass. Pumping gas at gas stations is a pain, too, but at least it's only once every week or two.

Alex Gruzen, the CEO of the wireless charging tech company WiTricity, told me one automaker has done an internal survey of its plug-in hybrid-electric vehicle (PHEV) owners and discovered that 70 percent of them never plug in. They use the vehicles as ordinary hybrids, sacrificing an enormous amount of fuel economy (which they paid extra for!) just because nightly plugging in is a hassle.

(Gruzen can't reveal which automaker, so I can't confirm the survey, but this study and this one support the conclusion that PHEV owners plug in far less than would be optimal.)

plug-in car
Maybe not so simple after all.
(Shutterstock)

EV manufacturers know about these anxieties, which is why all of them are working to extend range and all of them are working toward wireless charging.

So WEVC is going to ease consumer anxieties and accelerate EV adoption. It's also going to be a boon to public transit. And it's going to serve as a key enabler of self-driving vehicles and vehicle fleets. We'll get to all that in a minute.

First, a quick tech primer.

The wireless charging tech involved in EV charging (so far)

One key technology is pushing WEVC toward broad adoption.

Today, most commercially available consumer device chargers, like all those toothbrush or cellphone charging pads, use inductive coupling: One coil of wire (the transmitter) converts electricity into a magnetic field, and another (the receiver) converts it back into electricity. The magnetic field is omnidirectional — it's not aimed or directed — so the receiver has to be quite close to the transmitter to pick up much power.

A recent advance in induction is known as magnetic resonance, in which the transmitter and receiver are "strongly coupled," tuned to the same frequency, which allows the magnetic field to be directed, increasing the distance it can travel and the end-to-end efficiency of the process. Magnetic resonance was demonstrated by a team at MIT in 2007 (the team that went on to found WiTricity).

Think of them as wireless charging 1.0 and 2.0. The first magnetic resonance products, including laptop chargers, will hit the market later this year.

The advantage of magnetic resonance is mainly convenience: The transmitter and receiver can couple at any orientation and at greater distances, so the device doesn't have to be quite so precisely positioned over the charging pad.

It's also incredibly efficient. The larger coils in EV chargers, operating at higher frequencies, attain end-to-end efficiency of 90 percent or even a little higher, roughly equivalent to the efficiency of a plugged connection.

Note: Many stories on EV chargers still use lazily use "induction," but they're usually referring to magnetic resonance.

How magnetic resonance charging works.
How magnetic resonance charging works.
(WiTricity)

There are other wireless techs that might enter the EV space sometime — microwaves, in particular — but they are more speculative. It's magnetic resonance that's going to have an impact in the next few years.

(For more background on wireless charging — the science, the technologies involved, the companies trying to commercialize in the consumer device market — check out this earlier post.)

Wireless charging will boost consumer EV adoption

EV owners who don't want to plug their car in every night currently have only one option, the only WEVC product on the market today: Plugless, by Virginia-based Evatran.

Here's the system, charging a Nissan Leaf:

plugless power (Plugless)

There's a small charging pad connected to a wall-mounted power adapter. On the underside of the vehicle is a receiver. At least for now, receivers have to be custom-made for each vehicle type; currently they are available for the Nissan Leaf, Chevrolet Volt, Cadillac ELR, and (later this year) Tesla Model S.

The current Plugless model is 3.3 kW, which charges about as fast as a standard Level 2 (240-volt) household plug. It will charge a Leaf from empty to full in about eight hours.

The company is also close to introducing a 7.2 kW model especially for Teslas. If it's adapted for other cars, it would cut Leaf charging time about in half, to four hours.


As the first consumer-facing company in the WEVC space, with two years of selling product, Plugless shared some of its thoughts on the market in an interesting blog post.

It turns out consumers love WEVC. Naturally Plugless is going to say so, and share the most positive reviews, but it's something I've heard over and over again in stories and discussions: Once charging becomes automatic and worry-free, it's hard to imagine going back. Plugless says it has talked with a number of consumers for whom wireless charging was the catalyst to finally switch from gas cars to an EV.

Interestingly, Plugless consumers are not generally demanding higher-power chargers or faster charging. Evatran has been involved in experiments at Oak Ridge National Laboratory (ORNL) getting up to 20 kW out of similar chargers, but the company doesn't see much market for it, at least not in the home.

There are several reasons for that. For one thing, as this big study by Idaho National Laboratory found, the vast majority of charging — about 85 percent — is done at home. When the car is parked, it's charging, so it's always "topped off." There just aren't many use cases when people a) drive so much in a day the battery is entirely drained and then b) need to charge it really quickly.

Also, the typical house's circuit can't handle much more than 7 kW; beyond that, the electrical system would have to be upgraded, imposing additional cost for modest advantage.

It's the convenience consumers love with WEVC; the speed only needs to match a plugged connection.

(See also Qualcomm's "Halo" WEVC system, now being used to charge Formula E cars, soon to enter wider production.)

China is racing toward WEVC

Plugless is soon going to have lots of competition. In a market report on WEVC technologies, Navigant Research had this to say:

It is now clear that several major automakers are planning to bring wireless systems to market within the next few years, and a significant portion of the industry believes that wireless technology represents the future of plug-in electric vehicle (PEV) charging. …

Within a decade, wireless charging could be the leading way of charging EVs. Navigant Research forecasts that wireless charging equipment for light duty vehicles will grow by a compound annual growth rate (CAGR) of 108% from 2013 to 2022, reaching annual sales of slightly less than 302,000 units in 2022.

That's fast:

EV wireless charging market (Navigant Research)

As you can see, Navigant (and everyone else I've talked to) thinks the biggest growth is going to be in China, which is — little-known fact — expected to become the world's biggest EV market this year.

(See also this IDTechEx report.)

Infrastructure is the key to unlocking WEVC

One reason WEVC is going to take off in China is that China's policies deliberately favor EVs. But there's another reason too: The biggest accelerant of EV adoption won't just be home WEVC, it will be WEVC infrastructure, and China, unlike the US, is still making big, bold infrastructure investments.

Imagine, a few years hence, when the bulk of EVs are outfitted with standards-based, interoperable WEVC receivers. Charging pads could be embedded in parking garages, parking lots, street curbs, rest stops, even under select traffic lights.

I talked to engineer Omer Onar at ORNL about whether this "charging in motion" scenario is realistic, and he said there's absolutely no physical barrier; the only problem is cost.


He said to keep cars charged all the time would require filling about 75 percent of road surfaces with 10 kW chargers, which obviously isn't practicable. But if the chargers can be boosted to 100 kW — entirely within the realm of the possible — that number falls to 7.5 percent.

And if you focus on the best spots, places where people stop or slow down frequently, you can get that down to 2 or 3 percent. That's still an enormous project, but not something outside what a big city might attempt.

There's an actual study underway in the UK of highways with embedded wireless charging, though honestly that seems like a crazy idea. (Why charge where people are moving fastest? You'd have to fill miles and miles of road with chargers.)

WEVC highway in England
Getting low on power? Pull into the charging lane for a while.
(Highways England)

The first steps for WEVC infrastructure are likely to be less ambitious than this, though, finding a foothold in office parks, among shared vehicle fleets (like electric company meter readers), and in public transit (more on that in a second).

When might all this happen? I pressed WiTricity's Gruzen for predictions. He said cars with wireless charging are hitting the market in 2017 and 2018. "By 2019 it's ubiquitous," he said, "in terms of all the major automakers having wireless charging cars, all operating on a global common standard."

That is, as he notes, right around the corner, especially in terms of automotive design cycles. But WiTricity is in discussions with automakers all over the globe. (Toyota is a big investor as well as a licensee — the next-gen plug-in Prius will have wireless charging built in.)

Automakers are pushing hard toward EVs, and they all see WEVC as key to opening up the market. Once the standards and vehicles are in place, infrastructure will start to catch up, most quickly in China.

Wireless charging will be a boon to public transit

One of the first places WEVC is going to have an impact, outside of individual garages, is in public transit. Public WEVC infrastructure will work best along fixed routes, which is what transit offers.

The fastest and easiest way to implement WEVC is for buses, which can easily be outfitted with receivers.

An "e-bus" from German company Primove.
An "e-bus" from German company Primove.
(Primove)

There's a public bus route being tested with WEVC in the UK; "similar systems are already being used in Turin and Genoa in Italy, Utrecht in the Netherlands and in Mannheim in Germany." Here's a story about a wirelessly charged bus line in South Korea from back in 2013. (That one used the OLEV system by KAIST, which is worth checking out.)

Over at Charged, a magazine covering EVs, Charles Morris has a nice feature on a Utah company called WAVE (Wireless Advanced Vehicle Electrification), which came out of Utah State University in 2011. It's making WEVC systems for buses:

WAVE currently has systems in operation in several cities, and [CEO] Masquelier told Charged that he expects to have at least 20 systems up and running later this year. "We’re in a position now where we can produce the systems very quickly."

WAVE systems, placed where buses stop frequently, usually at the beginning and the end of the route, are entirely automatic — no intervention from the bus driver is required. (Contrast this with stopping to plug in periodically or fiddling with those overhead catenary wires.) The advantage for buses on a WEVC-enabled route is that they can go farther and/or slim down on their batteries, making them lighter and cheaper.

Incidentally, earlier this month Utah State University unveiled its first public demonstration of charging in motion.

Last month, a Pennsylvania company called Momentum Dynamics announced that it would deliver a whopping 200 kW wireless bus charger in 2016, for municipal bus fleets in Washington and Maryland. And the CEO says, "Even higher power systems are in development."


What about public transit's perennial problem, the "last mile" between train or bus stop and home? Perhaps for that, cities could use fleets of electric, self-driving, self-charging vehicles — "pod cars."

Wireless charging is necessary for the spread of autonomous vehicles

Everyone is excited about the promise of autonomous electric vehicles (AEVs). There is great potential for self-driving buses, trucks, industrial equipment, and, of course, shared vehicle fleets.


But think about that theoretical fleet of Uber-like autonomous taxis. Who's going to plug them in? A staff of workers, waiting by charging stations for when they're needed?

No. If autonomous fleet vehicles are really going to work, they're going to need to charge themselves. How can they do that?

Here's one possibility, worked out by Tesla:


I think we can all agree, noooooooooo.

Aside from the abiding creepiness, that's a lot of moving parts, vulnerable to corrosion or theft. (Cables at EV charging stations are frequently robbed for copper in poorer countries.)

It's got to be wireless. AEVs can perfectly position themselves over WEVC pads for maximum efficiency. A fleet of AEVs can share a few common WEVC pads. AEVs can communicate among themselves, swapping out spaces over charging pads as needed.

Think about WEVC pads integrated into automated garages of the kind Westfalia makes, and how much more efficiently they could be used by AEVs:


Google is already testing wireless charging capabilities on its self-driving cars; other manufacturers are sure to follow.

How will it all fit together? Here's a Nissan video about the "fuel station of the future":


This is all the transportation revolutions coming together: self-driving electric vehicles, interacting with the energy grid, charging themselves.

Once AEVs — whether buses, cars, trucks, or marine vehicles — start charging themselves, transportation becomes like a perpetual motion machine, a ubiquitously available service that requires little human interaction.

Electric vehicles are by nature simpler and require less maintenance than internal combustion engine vehicles. Once they are driving and charging themselves, there's not much left for humans to do, except get where they need to go.