## 2 Methodology
### Estimation of PV Potential from PV-Powered EV
#### 2.3.1 Estimation of PV Potential Excluding Shadow Effect  
To evaluate the PV potential (excluding shaded areas), we used the System Advisor Model (SAM) software developed by the National Renewable Laboratory (NREL), which is a new and renewable energy system. SAM was used as an analysis tool because it has been used in numerous photovoltaic power output projects owing to its accessibility as a free and open-source software that produces reliable and diverse results [32]. SAM requires meteorological characteristics of the desired region, specifications (performance), and design values (type, installation conditions, and other factors) of the module/inverter as input data to evaluate the potential of the photovoltaic power output. To reflect the meteorological characteristics of the study area, typical meteorological year (TMY) data for the area near the study area were purchased and used on the SolarGIS website. TMY data are the meteorological data collected hourly for a year by selecting a representative year for each month based on the long-term meteorological database, including various meteorological factors such as insolation, dry bulb temperature, and wind speed. Table 2 lists the model names and physical specifications of the modules attached to the four sides of the vehicle. The smf-175W model was selected for module A with a rated capacity of 175 W, smf-100W model for module B with a rated capacity of 100 W, and fs40W model for modules C and D with a rated capacity of 40 W. For the inverters, the Enphase Energy Inc's IQ7 PD-72-2-US model was selected for modules A and B, and Enphase Energy Inc's IQ7 PD-84-2-US model was selected for modules C and D. The module was selected considering the area of each part of the vehicle. However, because this study aimed to analyze the differences and variations in the potential solar power output with the module attachment position, the results were presented assuming that all four module capacities were 100 W.  
The design values of the photovoltaic module include the type, installation inclination, installation azimuth, and the set design values, as listed in Table 2. However, this is based on the original characteristics of the module attached to the vehicle (i.e., when the vehicle is stopped on a flat surface). During actual driving, the slope and azimuth of the module change for each section based on the road characteristics, and the corresponding values are input to the SAM. As module A is flatly attached to the roof, only the inclination varies with the characteristics of the road, whereas in module B, the inclination and azimuth vary. In modules C and D, the azimuth varied; however, the inclination was fixed at 90\({}^{\circ}\). Thus, the generation potential of a PV-powered EV can be roughly evaluated using the three types of data and SAM software. Owing to the short driving time, we calculated the PV potential for each module in the unit of seconds. The PV potential for each section was evaluated by accumulating the driving time required for each section in seconds. However, this corresponds to the case wherein the shadow effect in the pathway is neglected, i.e., assuming 100% light-receiving efficiency. Therefore, the shaded area should be considered while evaluating the actual photovoltaic power output potential.