## 3 Electric Vehicle Impact Simulations
### Battery Energy Storage System (BESS) and Photovoltaic (PV) Models and Control Strategies  
Nowadays, Li-ion technology is dominating the market for portable devices, including EVs, but it is also increasingly used to support the RES management, in order to increase the hosting capacity. In case of a high penetration of DGs, it could be tough to properly manage the distribution grid. Therefore, in order to cope with this \"new\" problem, new solutions are under evaluation. BESSs are pivotal for some of the challenges of the modern society: the transition towards a renewable-based energy system; the rural electrification of developing countries and to facilitate the inclusion and the management of EVs charging processes. What is important is to identify which technology is the most suitable for the different final application, because no BESS is able to fulfil the needs of every possible service. In this case, it is necessary to focus on stationary applications. The higher are the two indicators, the better the performances of the battery will be. Lithium-ion technology has the best combination of energy and power performances, so it appears to be the most suitable chemistry for stationary application. However, lithium ion BESSs cover less than 30% of current stationary installations around the globe. The main reason is represented by the high cost of installation if compared with the other ESS technologies. BESS are well suited for almost all utilizations, but the most appropriate one is with particular tendency for renewable integration, frequency regulation, off-grid systems and peak-shaving. In particular, if the storage is deployed in conjunction with local generation, it ensures reliability by filling the gaps between production and demand. In this case, BESS can range from tens of kW up to tens of MW. The energy storage system is the component that allows being more flexible in the energy management throughout the day as the photovoltaic energy production is not always available. Lithium-ion battery energy storage systems are typically used for applications related to power plants due to the high energy density and the longer lifecycle compared to other battery technologies. Three PV alternatives are presented in Figure 5.  
For the purpose of selecting the nominal power and energy for the ESS, two parameters were evaluated, depending on the different PV technologies and Self Consumption (SC) thresholds, whenever \(P_{PV}>P_{Load}\) the maximum power difference \(P_{PV}-P_{Load}\) throughout a day; the maximum energy excess that could be stored in the typical 12 days of the year. The CIGS (copper indium gallium (di)-selenide, compound semiconductor) technology allows the lowest power difference and energy excess given a certain self-consumption threshold, which are respectively equal to 23 kW and 150 kWh for a \(SC=0.65\). In addition, two further considerations are needed to select the correct storage system size. First, it is necessary to consider the state of charge (\(SoC\)) of the energy storage system, computed as:  
\[SoC(t)=SoC(t-1)+\frac{P_{t}^{ESS}}{4\times E_{n}^{ESS}} \tag{1}\]  
whose operating window could be limited between \(0.2\leq SoC\leq 0.9\) following the charging and discharging process. Figure 5: Maximum (**a**) power and (**b**) energy of the different photovoltaic (PV) technologies (a-Si: amorphous silicon; CIGS: copper indium gallium (di)-selenide; mc-Si: multi-crystalline silicon). Then, for simulation purposes, a constraint on the daily operation of the \(E\!SS\) has been added. It is necessary to have the same \(SoC\) at the beginning and at the end of the day, in order to replicate the same performance each typical day of the year. In order to store the greatest amount of energy during the day, the best choice is to set the minimum level of \(SoC=0.2\). The energy constraint is the most important one to select the size of the \(E\!SS\).