## 2 State of the Art of Scientific Literature
### Photovoltaic Integration for Bus Charging  
Charging infrastructures of EBs are often supplied only by the utility grid [25]; however, [PERSON] et al. also included local PV production and/or electricity storage in order to improve the energy management [26]. Regarding a PV-storage-based charging station at the depot, the authors showed that limiting the supplied power from the grid to 5 kW can maximize the bus depot operator profit while minimizing the charging power causing transformer overloading. [PERSON] et al. also presented an optimal energy management system using a weighted multi-objective stochastic optimization to minimize the cost of electricity while aiming to reduce battery degradation [27]. [PERSON] et al. studied the stochastic energy management of bus charging stations for reducing charging costs with PV production and battery storage considering bus-to-grid energy flows [28]. [PERSON] et al. adopted another point of view, attempting to find an optimal bus charging schedule at line terminals or depots in order to locally smooth the PV production fluctuations [29]. The proposed method was compared to uncontrolled charging and a cost minimization strategy. Results showed that operating costs increased marginally compared to the cost minimization strategy, but that utility grid power fluctuations were significantly reduced.  
Concerning the design of PV power plants related to battery charging of EBs, [PERSON] et al. focused on the suitable locations of PV implantation at bus shelters [30]. Based on the solar irradiation, the potential of each bus shelter in Lisbon to supply electronic devices with PV panels was analysed. Almost 54% of bus shelters were found to be able to receive small devices such as lighting or remote small-scale sensors, but only 4% could provide at least 100 W and 2.4 kWh per day in order to supply a refrigerated vending machine. [PERSON] et al. performed an economic and environmental feasibility study about the installation of PV panels near a bus route [25]. With the right placement of PV panels, supplying EBs with PV panels was found economically and environmentally interesting. However, the investment cost can be huge, as shown by [PERSON] et al. who designed an off-grid PV system to balance the consumption of a bus depot in Malaysia [31]. Sizing results showed that 7350 PV modules (6.5 MWp in total), a battery capacity of 118,200 Ah, and 23,200 m\({}^{2}\) area were needed to offset a peak demand of 466.5 kW. [PERSON] et al. [32] determined the optimal size and location of rooftop PV panels and capacity of storage near the line terminals of neighboring communities. A case study in Hong Kong showed that the infrastructure (PV and stationary battery) deployment achieved the shortest payback period of 3.98 years and addressed the design issues such as battery oversizing with PV and battery misallocation. In [33], [PERSON] et al. focused on the optimization of the charging strategy in the same community-based bus network to increase the on-site consumption of PV production. All of these studies have showed the importance of both infrastructure location and charging strategy to lower the cost.