KAIST introduced environmentally friendly public transportation to Seoul Grand Park.
First step toward the commercialization of Online Electric Vehicle (OLEV)
An online electric vehicle (OLEV) developed by KAIST replaced a trackless combustion-engine train running inside Seoul Grand Park in Gwacheon City, South Korea. On March 9, 2010, Seoul City and KAIST celebrated the completion of OLEV that picks up electricity from power cables buried underground through a non-contact magnetic charging method, called electromagnetic induction. Electromagnetic induction is the process of inducing electric current in a coil with the help of a magnet.
The pickup unit installed underneath OLEV collects electricity from a roadway and distributes the power either to operate the vehicle or for battery storage. Whether running or stopped, OLEV constantly receives electric power through the underground cables. As a result, OLEV mitigates the burden of equipping electric automobiles with heavy, bulky batteries—OLEV’s battery size is one-fifth that of the batteries installed in electric vehicles currently on the market.
There is no need to establish massive charging stations or to set aside much time for recharging. If the underground power lines installed on road curbs, bus stops, parking lots, and intersections, the power system could support a substantial portion of public transportation: For example, KAIST estimates that by establishing 20% of the road infrastructure for a bus route in Seoul City, the city could offer its citizens the online electric buses.
The non-contact charging of vehicles while running, idling, or parking is an important and practical technology necessary for the development of commercialized electric vehicles. This technology solves many of the issues related to the current batteries of electric vehicles, including size, expense, and repair/maintenance. In addition, non-contact charging is safer because it prevents potential electrical hazards, such as electric shock, that result from direct contact with power sources. Furthermore, it is more convenient to drive vehicles without overhead wires directly connected to power lines, as is necessary for streetcars and trams.
The recharging strips are divided into several meters of segments in length, and vehicles receive the power each time they pass over one. In other words, a sensor is affixed within each segment. When a car with the pickup equipment drives over the segment, the sensor is turned on for the car to receive electricity. This means that when a car without the pickup equipment passes over the segment, it will not collect any electricity.
The power supply via on/off switch (sensors) relieves safety concerns about electromagnetic field (EMF). Pedestrians or cars without the pickup unit will not be exposed to EMF because the sensor embedded in the segments will not work, thus no electricity generated. In addition, even under the circumstance of EMF yield, the test results for OLEV are well below the 1998 the International Commission on Non-Ionizing Radiation Protection (ICNIRP) guideline, 62.5mG at 20khz. OLEV’s EMF test results range from 20mG (inside OLEV while running) to 50mG (around OLEV while parking).
When talking about a wireless energy transfer such as electromagnetic induction, the most critical issue is how to reserve an air gap of 12cm (in accordance with Korean law) between the surface of roads and the bottom of vehicles while having 60% power transmission efficiency or above. There was a similar research done in the US at University of Berkley—their research was considered unsuccessful because they obtained an air gap of 5-7cm with 60% maximum level of efficiency. Besides, their electromagnetic field (EMF) was quite high (2000A), and they were unable to bring down the high cost of installing power supply system. By contrast, for the first time in the world, KAIST has succeeded to obtain 12cm (and up to 17cm) of air gap with more than 70% efficiency level of power transmission. The EMF is also well below the international standard of 62.5mG. In a nutshell, KAIST has achieved a core technology in terms of capacity, efficiency, and EMF to develop electric vehicles for commercial use.
The city government of Seoul and KAIST signed a Memorandum of Understating (MOU) on the development of an online electric vehicle in August 2009. Against the backdrop of the public’s increased awareness of environmental pollution and the depletion of fossil fuels, the two organizations agreed to introduce eco-friendly vehicles to the city’s public transportation, beginning with the introduction of a trial version of OLEV to places like an amusement park, bus terminal, airport, shopping mall, and the like.
KAIST’s OLEV research team is made up of experts from a variety of fields, including electrical and electronics engineering, computer sciences, civil engineering, information technology, and mechanical engineering. OLEV’s success at Seoul Grand Park is a result of KAIST’s innovative initiatives on convergence research, and KAIST has submitted more than 120 applications for patents right in connection with the development of OLEV.
Online Electric Vehicle at Seoul Grand Park
In terms of power transmission efficiency, KAIST’s research team achieved a maximum pick-up capacity of 62kw/h, 74% with an air gap height of 13cm from a road to the bottom of a vehicle. Composed of one engine and three passenger cars, OLEV travels along a total length of 2.2km beltway. There are four sections of power supply infrastructure established on the route (Sections 1, 2, and 3: 122.5 meters long each, and Section 4: 5 meters long). The power supply cables were laid underground for a total of 372.5 meters, 16% of the total distance of the 2,200 meter route.