Future network loading and tariffs with electric vehicles

Abstract: Electric vehicles have received a lot of attention lately and are expected to boom in the near future. In the power grid industry this raises concern on whether the grid is dimensioned to handle the power peaks related to charging. Solar cells are also a hot topic when discussing future energy supply and how it will impact on the grid. Initially this thesis gives insight to the current state of solar cells and electric vehicles, which charging techniques that are being used and future prospects of both technologies. There- after, investigation goes into how the grid is utilised today using mathematical statistics and what the load situation will look like with a large scale introduction of electric vehicles. A case study in a stressed grid with a high penetration of electric vehicles is also done to showcase impact of solar cells. Specifically loading of secondary substation transformers, cable loadings and voltage drops are analysed to find limitations. Key results are that the grid in general has sufficient capacity with good margin to the highest expected peak in power and that the current tariff structure would generate a large income stream if home charging would become more common. The results from the case study in a stressed grid shows that even if transformer loading is high , the cable capacities are sufficient to avoid overload. Also, the slightly larger voltage deviations are still well within E.ON guide- lines. Solar cells delivers most energy mid-day when charging does not occur, and therefore do not reduce power peaks. In conclusion, E.ON should not be concerned about a large scale introduction of electric vehicles, rather welcome it. The tariff should not be capacity based on account of electric vehicles since there is little risk that their charging will overload the grid. Moreover, the current tariff structure benefits greatly from an increase in consumption and higher peaks, which leads to more billable kilowatt-hours and upgrades of fuses. There are of course other arguments for a capacity based tariff, but these are not treated here. The calculated resulting annual revenues are 213 MSEK and 430 MSEK for 20% and 40% electric vehicles respectively.