The Impact on The Power System of Grid-Connected Electric Vehicles : Best4Grid

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Two ways of decreasing greenhouse gas emissions are using electric vehicles and renewable energy sources. The electrification of the transport sector will lead to a higher electricity demand and could amplify existing peaks in the distribution grid. A larger share of intermittent energy sources can cause a mismatch between consumption and production, which then requires backup power which can increase the electricity price and greenhouse gas emissions. In recent years, a new concept called vehicle-to-grid has been developed. The idea is that the battery of electric vehicles can be used to supply the grid with power when needed. An ancillary service vehicle-to-grid can be used for is peak shaving by supplying power at times of high power demand, and therefore decreasing the strain on the electric grid. The electric vehicle owners in turn can earn money by allowing their vehicle to be used in vehicle-to-grid by selling electricity when the electricity prices are high. With the increasing number of electric vehicles in the world, and more intermittent renewable energy sources, the potential of vehicle-to-grid becomes larger. In this thesis vehicle-to-grid is modeled and evaluated for 24 hours using 2 cases, the first case is with one household load and one EV, and the second case is with 10 household loads and 10 EVs. Two different driving profiles were used to determine how vehicle-to-grid is dependent on usage patterns. One profile represented a person working from 8 am to 4 pm, and the other profile worked from 9 pm to 5 am. The results showed that the peak shaving potential was high for both types of user profiles in the single load case and the 10 household case. The optimal combination would be to utilize both user profiles at the same time, as one can peak shave while the other one is unavailable and vice versa. The economic revenue from vehicle-to-grid is highly dependent on the electricity price. To maximize the revenue, working from 8 am to 4 pm was the best for the chosen load data, since most peak shaving occurred during the evening. When 24 hours passed, there was still sufficient state of charge for further usage of the electric vehicle.