Over the past 15 years, energy storage technologies for vehicle traction systems have improved dramatically. This technology is finding its way into commercially viable hybrid, electric and plug-in hybrid vehicles. Vehicle-to-grid (V2G) prototype vehicles are being developed and tested at the National Renewable Energy Laboratory (NREL). Utilizing bi-directional power electronics can allow a vehicle to not only charge its batteries from the electric utility grid during charge but also can provide power back to the grid during discharge. The possible uses of V2G vehicles for distributed energy applications are to provide power to utility/local loads, regulate voltage and frequency, offer spinning reserves, and enable electrical demand management. Electric, plug-in hybrid and V2G vehicles will have the potential to absorb excess electricity produced by renewable energy sources (e.g., wind or photovoltaics) when the grid is operated at low load conditions.
A V2G vehicle provides an electrical connection to the grid resources via an electrical plug-in interface. Such vehicles often also offer a communication and control interface to the utility. Some V2G vehicles may have on-board data acquisition systems to monitor parameters such as power and battery state of charge (SOC). V2G vehicles will utilize a reliable, high-power, high-energy battery pack with bidirectional power electronics and controller. The controller module controls the power electronics to operate in charge, discharge, or standby modes. The first commercial V2G vehicles are expected to use either a nickel metal hydride or a lithium-ion battery pack to obtain high energy density....(read more..)