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University of Delaware

Vehicle-to-grid (V2G) technology enables electric vehicles to not only charge from the grid, but also to discharge to the grid, and with appropriate controls, to also provide valuable grid services. The University of Delaware demonstrated at the ESIF the V2G characteristics of electric vehicles, including a TransPower school bus and BMW MiniE, as well as four V2G charging stations and an optimizing aggregator, provided by Nuvve Corporation. The aggregator technology communicates through an open-source protocol designed to enable entities to interact with and dispatch an abstract fleet of V2G or smart-charging vehicles, facilitating the optimization of electric system resources to allow greater amounts of distributed and variable renewable resources on the grid. 

Electric school bus under study at the Energy Storage Lab at NREL's Energy Systems Integration Facility, featuring vehilce-to-grid integration capabilities enabling it to feed power back to the grid and essentially serve as a mobil power generator.

Photo by Dennis Schroeder

The ESIF research examined the basic electrical characteristics of the V2G vehicles, such as the round-trip efficiency of providing grid services, their robustness during voltage transients and electrical faults, the latency between sending a control signal to the vehicles and seeing a response in power output, the maximum rate of increase in power output, the maximum and minimum up time for the vehicles, and power quality as the battery discharges. The research also quantified the vehicles' response to simulated utility control signals and demonstrated autonomous operation for grid support based on local frequency and voltage measurements, using a grid simulator in the ESIF. In addition, the vehicles were controlled to level the power production from home-sized photovoltaic systems. This included two modes: first to minimize power injected into the grid, then to level solar power output by storing power during peak solar output and discharging after sundown.