── What exactly is in-motion wireless charging?
Simply put, it is a system for sending electricity from coils embedded in the road to a moving vehicle; the vehicle is then powered by that electricity. The advantage of this technology is that it enables EVs to have smaller batteries.
Right now, if you want to increase how far an EV can travel, you have to install bigger batteries. The lithium ion batteries used in EVs are really wonderful, but they are heavy compared to gasoline and are still quite expensive. In addition, limited battery materials is another issue we will face as EV spread and battery production drastically increases, as well as the large volume of CO2 emitted when making them. It would be best if EVs needed fewer, smaller lithium ion batteries.
Electric trains, on the other hand, run without carrying batteries, right? That's because they receive electricity from power lines. If we could do the same thing with EVs, their batteries could be smaller. But unlike trains, cars don't follow a set of tracks and can move around freely, so we can't power them from fixed lines. That's why we want to try and send electricity wirelessly.
── Would coils need to be embedded all along the roads that cars drive on?
No. To consider where coils would need to be embedded, we drove cars around town near our research center to investigate where the cars were on the road and for how long.
We found that about a fourth of the time on the road is spent within 30 meters in front of a traffic light. So, if you drive for an hour, about 15 minutes is spent waiting at traffic lights. It might be even longer in big cities like New York or Tokyo. In other words, if we install coils under the 30 meters in front of traffic lights, it's very likely that EVs would get sufficient energy to run on a smaller battery.
If everything goes to plan, EV battery charge levels would hardly change at all. In other words, you wouldn't even have to bother with plugging your car in to charge it. After all, it's a pain to have to charge an EV after every drive, right? With in-motion wireless charging, though, we could get EVs that don't need to be plugged in. The whole current concept of an EV, as a car that can't go anywhere unless the user puts energy into it, will change, and people will be able to keep driving continuously without range limits. This technology will also be extremely important with the emergence of unmanned, autonomous driving vehicles.