Coils under the pavement keep Gumi, Korea's buses moving

Boy rides a public bus in Seoul. Photo by Andrew Griffith.

Buses are the main public transit mode worldwide. In the U.S. alone, there are roughly six billion bus trips per day. Most of these run on diesel fuel, a potent greenhouse gas emitter. To save on fuel and pollution, transit systems around the world are turning increasingly to electricity to run their buses. Electric vehicles make for a safer, quieter, more environmentally-responsible ride.

To date, the main issue with electric vehicles is the large size and price tag of battery packs. But that may be changing.

Yesterday, the BBC reported on a new electric bus system in South Korea that wirelessly charges vehicles as they pause at stops. An initial 12-kilometer stretch of wireless charging electric buses has been outfitted in the southern city of Gumi, with 10 more on the way by 2015. Charging coils are placed under the pavement and reboot the buses wirelessly mid-route. The coils can complete a charge from a distance of more than a foot, with 90% efficiency.

Wireless charging (also known as inductive charging) is safer and more convenient for drivers, and keeps buses from having to travel to and from charging stations, which reduces service. It also allows battery packs to be sized three times smaller, increasing capacity and reducing vehicle weight.

Electric buses are certainly not new, and even inductive charging has been piloted before. Similar systems have been tested in Turin, Italy, in Mannhiem, Germany, in Vienna, Austria, and in the Los Angeles metro area.

As exciting as this technology is, however, it remains costly, as it requires the added investment of charging coils in both charger and bus, and requires a slower, less efficient charging process. Experts admit, it is mainly a demonstration technology. But on-going R&D could change that; investors may lie in wait to pounce on game-changing cost-effective electric bus designs.

A revelation could come in the form of rapid charging technology. This approach could marry the convenience of wireless with the reliability and affordability of stations.

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