Wireless Power Transmission Could Be Future of Electric Cars, Or Not
The recent EVS27 conference in Barcelona was an opportunity to explore a technology which has made headlines, but still needs a lot more careful thought and education: wireless charging. AT EVS, two companies displayed wireless solutions, Qualcomm and Brusa, an American start-up and a Swiss company with decades of experience in EV engineering. I went to both booths.
Everybody talks about wireless charging but that's not even the right name for the technology. This is actually wireless power transmission (WPT) via a magnetic field between a transmitting coil on the garage floor and a receiving coil on the underside of the car. The charging process is distinct, and only begins after the coil in the car has transformed the energy it received in electricity.
The parking pad has to be quite big, and actually, the bigger the better because the device needs a degree of tolerance for misalignment. Brusa's parking pad was a bit larger and thicker than the one from Qualcomm. The Brusa unit had a tough industrial look, while the Qualcomm pad looked more like a home appliance. The American company obviously spent more time on design, and it also displayed a whole range of vehicle receivers. Size matters here: 3.3 kW; 6.6 kW and even up to 20 kW. A strong current can be sent via a magnetic field but it will need a larger receiving pad fitted to the car.
Since I have a cat, my first question was about safety. This is not going to fry the cat, right? Both representatives from Qualcomm and Brusa said it won't. Both systems have an obstacle detection device built-in, and it will instantly switch off the magnetic field if it sees something interfering.
Both companies did many tests, indoors as well as outdoors, and safety should not be an issue for the foreseeable future. WPT will remain an add-on technology. All EVs will keep on having a standard plug. This is somewhat like computers. Wireless Internet is everywhere nowadays, but most computers still have an Ethernet port just in case.
That means that WPT will make EVs more expensive. Then there's the garage equipment. When some people think a wallbox is expensive, a parking pad for WPT costs three to four times more. But the worst problem is efficiency.
Electric vehicle fans are proud to say that an electric motor is much more efficient than an internal combustion engine. But WPT changes the efficiency equation.
Compared to a cable, WPT loses as much as 10 percent of the electricity it carries. In a Nissan LEAF, which uses 100 kWh per week, or 5,200 kWh per year, that's 520 kWh lost each year. The price of electricity varies a lot between regions, but to most people 520 kWh equals lunch money for several days.
So wireless power transmission may be more the future, because it's more convenient, but it's hard to think of a technology which makes EVs more expensive and less efficient as a progress. Ultimately, both Qualcomm and Brusa are clear-minded in the sense that they understand that WPT's success depends on who backs it. They're both waiting for a large car manufacturer to use the technology in a production model. EV fans will be waiting too, but not with as much attention as the wait for better batteries.
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