State Grid Corp, the largest power company in China, demonstrated the "vehicle-to-grid (V2G)" technology, which enables to exchange electricity between an electric vehicle (EV) and a charging stand, at the Expo 2010 Shanghai China.
"By using the rechargeable batteries of electric vehicles, it becomes possible to stably oparate the electricity grid," said Li Shu, Preparatory Department for Enterprise Pavilion of Shanghai Expo, Publicity and Promotion, Shanghai Municipal Electric Power Co, which is affiliated with State Grid.
For example, when the output from renewable energy sources such as solar power drastically drops, electricity can be supplied from several tens or hundreds of EVs to the grid to reduce the number of electric outages. Shu said that the full-fledged introduction of the V2G technology depends on the dissemination of EVs.
State Grid developed an EV rapid charger that supports the V2G technology. When an EV is connected to this charger, it automatically switches between charging and discharging in accordance with the supply and demand situation of the grid.
It is possible to check the remaining battery level and the electric flow on the monitor of the charger. For the communication between an EV and the rapid charger, the CAN (controller area network) in-vehicle LAN standard is used.
The charger can deal with direct-current electricity and has a maximum output of 30kW. Its voltage and current are 200-350V and 0-100A, respectively. It can charge a compact EV in about 30 minutes.
In addition to the rapid charger, State Grid exhibited a normal charger, which supports a single-phase alternating current and has a maximum output of 5kW. Its voltage and maximum current are 220V and 22A, respectively. To use the charger, a dedicated IC card has to be inserted in it.
This time, the company prototyped two rapid chargers that support the V2G technology, and they were installed at the exhibition site and a charging station in Caobao Road, China. The charging station is also installed with 11 normal chargers. A total of about 30 normal chargers were prototyped.
The EV used in the demonstration is the EV version of the Roewe 350, which was developed by Shanghai Automotive Industry Corp (SAIC). Equipped with a lithium-ion (Li-ion) rechargeable battery with a capacity of 35kWh, it runs 310km per charge.
The EV has a connector that enables to charge the vehicle with both the normal charger and the rapid charger. Judged by the connector's voltage and shape, the specifications of the chargers seem to be different from those being standardized in Japan.