Analysis and Dimensioning of Battery Switching Stations

The development of Smart Cities worldwide and the increasing issues related to sustainability and to the environment have pushed towards the electrification of transports, promoting a rapid advent of electric vehicles (EV) in the market. EVs are leading polluting emissions in the transport sector on a path towards zero, however, the charging of EVs’ battery has an enormous impact on power grids. High penetration of EVs can result in extreme loads that can alter electricity prices and suddenly increase bulk generation, which in turn generate more CO2 emissions if power plants still rely on fossil fuels. Therefore, high penetration without supervision and control strategies pose a threat to the sustainability of distribution networks. At the same time, EVs are not just challenging the sustainability of the power grid, but they are also stimulating and promoting its upgrading, becoming enablers of the Smart Grid. It is true that EVs impose new constraints due to the extra demands they create, but they also generate opportunities thanks to their flexibility as mobile storage devices. If battery charging is properly coordinated, EVs can play a positive role in enhancing the evolution of the smart grid. In a plausible scenario of a smart city where electric vehicles are widely used, Battery Switching Stations (BSS) might replace the current gas stations, as they provide services that allow to extend the travelling time of EVs. Within this context, the present thesis work studies the dimensioning of a BSS system and the possibility to exploit renewable energy sources (RES), particularly solar power, as main resource for the charging of batteries. Using battery to grid (B2G) technology to achieve high coordination with the grid, the battery switching station could accomplish multiple benefits. In addition to providing EVs users with battery swapping services, the BSS can also serve as an energy storage station or controllable load, becoming an active contributor of the smart grid. The complexity of this study case in terms of number of parameters is such that mathematical modelling did not represent an effective approach. Therefore, a process-based discrete-event simulator was specifically designed to study the object of this thesis. The simulator creates a digital prototype of the BSS and allows to study its performance through notions of queueing theory. Moreover, the BSS simulator can perform hourly comparisons of energy prices with RES generation profiles, with the aim of creating policies that improve the efficiency and management of the grid. By adjusting the charging and discharging times of batteries in coordination with generation from PV panels installed on the BSS, the load fluctuation is reduced and the penetration of renewables is improved as well. This cooperation between RES and BSS could not only benefit the power grid, but also promote the development of renewables industry and electric vehicle industry.