The resident eggheads at KAIST (the Korea Advanced Institute of Science and Technology, something like South Korea’s MIT) developed a technology called Shaped Magnetic Field in Resonance, or SMFIR. It consists of power cables operating at a specific frequency, which then generates an electromagnetic field. A coil placed within a certain proximity to that field can turn that resonance into electricity. It’s essentially wireless charging, but due to the intricacies of the KAIST design, they can achieve an astonishing 85% transmission efficiency.
What Gumi has done is lay SMFIR cable underneath select stretches of road, and then kitted out two electric public buses with the SMFIR coil. The batteries in the buses are quite small—about a third the size of what you’d find in a regular electric vehicle—and planners calculated that due to the high efficiency rate of SMFIR, they only needed to wire 5% to 15% of the bus’ route to provide the requisite juice.