Magnet-based wireless EV charger could be smaller, safer, and - SAE

16-Nov-2012 14:53 GMT

The new magnet-based wireless EV charger system has operated for about a year.

The prototype noncontact EV battery recharger proved it can withstand the Vancouver climate.

The new wireless EV charger technology could be installed in a street curb and under the hood.

The power-transmitter of the UBC charging system is basically a motor-driven permanent magnet.

An indoor demo version of UBC's magnet-based wireless EV charging system.

The new UBC wireless charger could fit into street curbs.

Electric?car?owners? least-favorite feature is probably the battery-charging cord. After all, no one is fond of having to remember to plug in their car every evening or fumbling around with the power cord each time.

It?s no surprise then that several companies such as Delphi, Infiniti/Nissan, Qualcomm, Plugless Power, and Rolls-Royce have either developed or tested wireless technology that requires motorists merely to park their EVs over a device that?s embedded in a garage floor or parking space, enabling them power up without even leaving their seats. Many auto industry marketing experts believe, in fact, that wireless battery charging is perhaps needed for widespread adoption of EVs in the U.S.

Existing EV charging systems are based on a well-known technique called electromagnetic induction to accomplish the task. A varying electric current in a conducting wire coil (transmitter) that is placed in the road bed produces via resonance a similarly varying current in a noncontacting coil (receiver) sitting just above in the vehicle. The transferred electrical power then feeds into the battery, recharging it.

Electromagnetic induction is not considered by all to be absolutely?ideal, however, because it can emit stray radio waves or heat up nearby metal objects (via ohmic heating) unless it is engineered correctly?two issues that evoke perceived public safety concerns. Makers also must be concerned with changing industrial safety codes and standards as research on such topics proceeds. The maximum power-transfer capabilities of radio wave-based systems can in addition be limited.

Researchers at the University of British Columbia (UBC) in Vancouver believe that they have developed a better, simpler way to wirelessly charge EVs. They have produced a safe, high-efficiency method that employs what inventor Lorne Whitehead, an applied physicist there, calls remote magnetic gears.

The new UBC noncontact power-transfer approach, Whitehead says, relies on magneto-dynamic coupling, or MDC?a magnetic field interaction between two rotating permanent magnets that are separated by an air gap of 4 to 6 in (102 to 152 mm). The system consists of a magnet on the transmitter side of the air gap between the road and the car, and another magnet on the receiver side. When a small electric motor turns the lower magnet, the upper one is caused to turn, ?much as a compass follows a changing magnetic field,? he explained. The top magnet then drives a small generator that charges the car battery.

?This magnetic field between them,? he continued, ?essentially acts as a mechanical coupling?an invisible magnetic pulley/belt system, but it requires no direct contact and is almost perfectly energy-efficient.?

In production, Whitehead added, the two magnets can be integrated, respectively, into the motor and the generator, making for a reliable and compact (better for packaging) power-transfer system. In addition, relatively cheap ferrite magnets can be employed rather than more costly and potentially supply-challenged rare-earth permanent magnets.

Tests show the system is more than 90% efficient compared to a cable charge, and perfect alignment of the car with the device is not needed. The new-fangled EV charging technology would be incorporated into low street curbs over which the car-borne magnet (which is installed under hood) would hang.

For around a year or so, four demonstration MDC systems have operated successfully at UBC, wirelessly charging electrically powered campus-service vehicles that have been retrofitted, Whitehead noted. He expects that the patent-pending technology will be licensed to other manufacturers, probably through a spin-off company.

?One of the major challenges of electric vehicles is the need to connect cords and sockets in often cramped conditions and in bad weather,? said David Woodson, Managing Director of UBC Building Operations. ?Since we began testing the system, the feedback from drivers has been overwhelmingly positive?all they have to do is park the car and the charging begins automatically.?

The novel EV charging system, supported by the Natural Sciences and Engineering Research Council of Canada?s Idea to Innovation Grant, was tested at UBC as part of its Campus as a Living Laboratory initiative.

Charging electric cars was not the inventor?s original goal. The idea arose from his general research interest in efficiently coupling electromagnetic energy across an air space for implanted medical devices, such as pacemakers. ?We?re also looking at other, smaller niche markets such as electric forklifts.?

?At this point we see no technological barriers to bringing this system to market and know no reason why it will not become the preferred mechanism for wireless charging of EVs,? he concluded.

Source: http://www.sae.org/mags/AEI/11554

alicia sacramone Don Grady ann curry euro 2012 Colorado Springs pga tour Nora Ephron