Electricity is amazing. You spin a coil of wire through a magnetic field and next thing you know everyone with access to an outlet has clean, quiet, instantaneous, and virtually unlimited power at their fingertips, whenever they need it. Wild.
It does have a couple of drawbacks, though.
One, mobile electronic devices — lawnmowers, phones, electric vehicles (EVs), drones, what have you — still have relatively big batteries and limited range. Two, electronic devices that aren't mobile have to be plugged in, leading to a tangle of wires behind every computer, TV, and kitchen appliance.
Wouldn’t it be cool if all those devices could be continually charging, without wires or cables?
That brings us to wireless charging.
Charging electronic devices at a distance seems a little bit like magic, but it’s now on the verge of a whole new range of commercial applications, which will be rolling out over the next few years. It’s entirely possible that you’ll never have to plug in your next laptop or EV.
Wireless charging is already here
It’s already possible to charge small electronic devices like toothbrushes and cell phones wirelessly. You just buy the right device and set it on its charging pad.
Most wireless charging today uses inductive coupling; resonant coupling is the next big thing
Your electric toothbrush, like most other wirelessly charged devices available on the market today, charges via inductive coupling.
Inductive coupling is simple: You run a current through one coil of wire (the transmitter); the current creates a magnetic field; the magnetic field induces current in the receiving coil. Electricity is transmitted from one coil to the other.
Problem is, the magnetic field is omnidirectional — it just shoots out in every direction. The receiver has to be very close to the transmitter to pick up much power; that’s why you have to set the device on the pad.
In 2007, some MIT nerds demonstrated resonant coupling. In this case, the transmitter and receiver are tuned to the same frequency, or “strongly coupled.” This allows the magnetic field to be directed at the receiver, increasing the distance it can travel and the end-to-end efficiency of the process.
Home wireless charging is pushing for greater distance with wacky new technologies
Resonant coupling will allow a charger to charge a device a few feet away. But some companies think wireless charging won’t be successful until it hits distances of 10 or 20 feet — enough to cover a room, basically.
New technologies promise those kind of distances, transmitting power via microwaves, radio frequency waves, ultrasonic beams, and even, yes, frickin’ lasers.
All these techs face limitations. Some only work with a direct line of sight between charger and receiver. Some offer relatively low efficiency. But there are companies pushing all of them and products beginning to trickle out to market.
Resonant coupling will be enough to make wireless EV charging popular
There is already at least one wireless EV charging product on the market (Plugless). Others are coming.
The way it works is pretty simple. A charging pad, connected to a wall-mounted power adapter, sits on the ground. The car parks over it. On the underside of the car is a receiver.
Once the charger detects the receiver within range, it automatically couples and starts charging. Easy.
Right now, the receivers are after-market — they must be bought and attached to a vehicle. But EV manufacturers are starting to build them into production vehicles, rolling out in 2017 and 2018 models. Alex Gruzen, the CEO of wireless charging company Witricity, predicts that "by 2019 it's ubiquitous, in terms of all the major automakers having wireless charging cars, all operating on a global common standard."
One promising application of wireless charging is public transit
Imagine an electric bus equipped with a wireless charging receiver. Along its route, at regular intervals, wireless chargers are embedded in the pavement. Whenever it is stopped, the bus is charging — no need to gas up, no need to plug in, and no need to connect to any awkward catenary wire. It’s a perpetual-motion bus.
Such buses are already being tested in the UK, Italy, the Netherlands, and South Korea.
Another is shared fleets of self-driving electric vehicles
How do those vehicles charge themselves? Will we keep humans on hand to plug them in?
Instead, imagine wireless charging pads in parking garages and curbs, places self-driving vehicles can simply return and park for a while to charge. It would be a perpetual-motion fleet.
Long story short, wireless charging is about to begin a transition from novelty to core infrastructure, in our homes and in our cities. Get excited.