AUTOMATED RECHARGING SYSTEMS FOR EV’S MOVE FROM LABORATORY TO PUBLIC ROADSFebruary 21st, 2017
BY SARAH GIBBONS, in London AS the drive to encourage electric vehicle (EV) ownership gathers momentum, so does the desire to install automated recharging systems, such as devices built into roads that top up batteries as autos motor on.
The technology is known as ‘dynamic inductive charging’ and has been trialled in a range of scenarios across different continents. And one system, in South Korea, is now in operation on a live transport route, on roads in the towns of Gumi, in the country’s southeast, and Sejong, in central South Korea.
As it stands, high implementation costs coupled with the still intermittent take-up of EVs are the main factors hindering wider installation of this convenient technology, despite proof that it can work.
But industry experts believe that the technological development in the field is so fast-moving that in-motion charging will be commonplace within the next five to 10 years.
Indeed, California-based Lucid Motors recently unveiled its ‘Air’ luxury electric sedan, fitted with inductive charging, enabling battery life of up to 400 miles. Also, another Californian firm, Faraday Future, has launched a new FF91, an electric SUV with a 378-mile range that is compatible with wireless charging stations.
Dr Burak Ozpineci, group leader of the power electronics and electric machinery group of the National Transportation Research Center at the US federal government’s Oak Ridge National Laboratory said: “In a few years, drivers of traditional gas cars will be viewed by society in the same way as smokers,” and predicted wind and solar power would drive the next generation of wireless charging.
Mashrur Chowdhury, Professor of Transportation at the International Center for Automotive Research (ICAR) at Clemson University, South Carolina, said: “Utility companies will drive it. It will all depend on how many electric vehicles we see – if we see gas prices going up and governments interested in investing more in alternative energy, that will motivate the deployment.
“Within five years I think we will see it in place in many areas. When people see these roads in cities it will prompt more people to buy electric cars. It’s a two-way street.”
To achieve this – batteries will need to be cheaper and more effective. Battery costs – currently up to 50% of the price of an EV – have proved prohibitive for many drivers wishing to make the switch from traditional vehicles. Current batteries also provide a very limited driving distance between charges and are heavy.
The proposed electromagnetic technology involved in ‘dynamic inductive charging’ is the same principle as the Qi wireless charging system which powers a smartphone. This could remove storage requirements for a battery, reducing its weight – and cost.
South Korea switched on its first wireless road in 2013 for its OLEV (online electric vehicle) bus service and has been expanding its coverage ever since.
Researchers at the Korea Advanced Institute of Science and Technology (KAIST) developed the system based on ‘shaped magnetic field in resonance’ (SMFIR) technology designed for autos.
Electric cables installed under the road are used to generate electromagnetic fields which are picked up by a coil inside the device and converted into electricity. The receiving equipment can be up to 17cm (6.7in) above the road’s surface.
The power cable installed under the road surface can generate a 20kHz magnetic field when the cable gets electricity from the power converter, which receives electricity from the grid at a typical industrial level of 3-phase 440V. The pick-up coils fitted to the underside of the vehicle are tuned to 20kHz resonant frequency and designed to have maximum exposure to the generated magnetic field which has an optimised shape to prevent leakage outside the required area.
A powered track consists of various component segments of different cable lengths according to the road type, expected vehicle speeds and vulnerability to traffic jams. For example a short section just the length of a bus can be installed at pick-up and set-down points.
The vehicle is installed with the correct devices such as regulators and a power distribution unit to convert and deliver the electricity to the battery.
During a demonstration in Seoul Grand Park, south of the capital, just 17% of the 2.2km route was powered in three sections but this generated sufficient power to operate the OLEV.
It now powers a bus service between the train station in Gumi, to the city’s In-dong district; a bus route in the city of Sejong; and the shuttle bus service around the KAIST campus. Plans are underway to integrate it into a new town development around the new Beijing International Airport, in China. And a memorandum of understanding has been signed with the municipality of Medellín, Colombia, for OLEV buses.
Dong-Ho Cho, who led the KAIST team said: “OLEV buses will greatly contribute to decreasing the consumption of fossil energy by achieving a fuel cost reduction of 38 percent compared to their diesel counterparts and 33 percent compared to their CNG [compressed natural gas] counterparts.”
Elsewhere, in Mannheim, Germany, the PRIMOVE team from Canada-based Bombardier have performed a series of tests with a dynamically charged truck in a construction site. The 10 meter-long vehicle, weighing 10 tons, was inductively supplied with energy at a power of up to 200kW using four 20 meter long charging segments of underground cable. A spokesman said: “We are technically ready to install the technology in ‘real life’.”
In Utrecht, the Netherlands, and Milton Keynes, UK, buses are able to charge wirelessly at bus stops with static pads in the road connecting remotely to the underside of the vehicles.
A spokesman for Milton Keynes Council said: ‘The wireless charging allows the buses to run throughout the day enabling electric buses to do everything a diesel bus can do.
“The buses will remove five tonnes of particulates and noxious tailpipe emissions from Milton Keynes’s streets each year. Approximately 270 tonnes of CO2 will be removed from the atmosphere – significant figures.”
In the US, the Evatran Plugless charging system, compatible with the Chevrolet Volt, Nissan LEAF, Cadillac ELR and Tesla Model S EVs, is being introduced in private car parks allowing motorists to drive over a pad embedded in the ground and leave the vehicle to charge wirelessly.
Prajyot Sathe, industry manager in the power train and electric vehicle team of the mobility group at business analysts Frost & Sullivan said: “Magnetic resonance pads in the road which sync with pads on the underside of the vehicle will be readily available in three to four years.”
But he admits the technology is expensive, with the dynamic application estimated to cost USD1 million per kilometre, including cable and pads installation underground, resurfacing work and pads on vehicles.
“Wireless road technology would only come into the picture when we get a bigger market overall for electric vehicles,” he predicted.
“Inductive charging will only be in premium vehicles initially – for mass market vehicles it’s very unlikely in the short term but after five to seven years there will be more mass market applications.”