V2G systems

V2G capability makes it possible for electricity to flow from the grid to a vehicle and from the vehicle to the grid. Since the output of an EV battery is DC, an inverter is needed to transform the current to AC, which is used on the grid. The inverter can be built into the EV (V2G-AC) or the charging station (V2G-DC). V2G-DC has already been successfully commercialised in the United Kingdom, Denmark and Japan using the CHAdeMO standard (IEC 61851-23, -24). Some V2G-AC examples also exist, such as school bus projects in the United States and Europe (e.g. the WeDriveSolar project in Utrecht). V2G systems are already technically viable, but regulatory, business and operational challenges remain.

Both V2G-AC and V2G-DC technologies are needed, but they have different uses – for example, DC for behind-the-meter optimisation and AC for public chargers. DC is the more straightforward option today because there already is a valid ISO standard that ensures home safety.

V2G charging offers major benefits beyond just mobility; for example, it is a way to dampen variations in loads and generation on the grid, it provides flexibility and balancing services, and it gives EV owners a potential source of revenue that reduces their ownership costs.