As of this Tuesday (August 6th) the South Korean city of Gumi’s transit system will see the addition of two electric buses that draw their power from the road. It’s the latest step in the development of the Korea Advanced Institute of Science and Technology's (KAIST's) Online Electric Vehicle (OLEV) system, in which electric cables embedded in the asphalt provide power to vehicles traveling on its surface.
The appeal of OLEV lies in the fact that electric vehicles using the system don’t have to be equipped with large, heavy batteries, they don’t have to stop to recharge, and messy overhead trolley lines aren’t required. Instead, the cables in the road produce magnetic fields, which receiving devices in the vehicles’ undersides pick up and convert into electricity. It can be a continuous process, or cables can be placed in separate locations along the road, providing ongoing top-ups to a relatively small battery within the vehicle. Typically, only about 5 to 15 percent of the road surface needs to be excavated for the embedding of the cables.
The buses will run a 24-km (15-mile) round trip route in Gumi’s inner city between the train station and the In-dong district. They will maintain a 17-cm (6.7-in) gap between their underbodies and the asphalt the whole time, receiving 20 kHz and 100 kW (136 horsepower) of electricity at a maximum power transmission efficiency of 85 percent.
EMF (electromagnetic field) levels within the buses are reportedly well within safe limits, plus the cables in the road only switch on when they detect the presence of one of the buses overhead – this should minimize pedestrians’ and other vehicles’ exposure to the magnetic fields, and will also save power.
Although this will mark the first time that OLEV is used in a public transit system, the technology has previously been tested in a tram at an amusement park in Seoul. Assuming all goes well with the two buses in Gumi, the city plans to add an additional 10 such vehicles to its fleet by 2015.