## 2 Materials and Methods
The results of the calculations show that the cosine of the Sun's rays falling on double-sided panels with an \"East-West\" orientation of the vertical stationary PV-modules during the day reaches a minimum at noon (Figure 6). This is due to the fact that such modules at noon, in the flow of the Sun's rays, are located parallel to the flow of the Sun's rays, with a deviation in this parallel flow in summer and in winter. In the morning and in the evening, the cosine of the Sun's rays falling on the double-sided panels with an \"East-West\" orientation of the vertical stationary PV-modules reaches its maximum value. This is because, in the morning and in the evening, double-sided panels with an \"East-West\" orientation on vertical stationary PV-modules are located perpendicular to the flow of the Sun's rays. The deviation of their location in the flow of the Sun's rays occurs both in summer and in winter. It was established that the weighted average daily installation efficiency of double-sided panels with \"East-West\" orientation on vertical stationary PV-modules have the same value as that of PV-modules with a \"South\" orientation (Table 3). However, greatest interest is given to the fact that these installation options have a value that mirrors that of the cosines of the Sun's rays falling on the surface of the solar panels on PV-modules (Figure 7). For double-sided panels with an \"East-West\" orientation on vertical stationary PV-modules, the maximum values of the cosines of the angles of incidence of the Sun's rays on the surface of such a panel will occur in the morning and in the evening. At the same time, PV-modules with a \"South\" orientation reach their maximum value for the cosine of the Sun's rays falling on the surface of the vertical stationary PV-module panel only at noon. It should be noted that there is a significant disadvantage suffered by vertical stationary PV-modules with double-sided panels with an \"East-West\" orientation compared to PV-modules with a \"South\" panel orientation. It consists in the fact that the production of the same amount of electricity requires twice the number of PV-modules. The daily positions required to reach the maximum values of the cosines of the Sun's rays falling on the surface of the panels of the PV-modules determine the practical value of using vertical stationary PV-modules with a double-sided panel with \"East-West\" orientation. Namely, such solar PV-modules are recommended for consumers who have morning and evening load peaks. First of all, these include household consumers. It should be noted that, for domestic electricity consumers, the morning peak of electricity consumption coincides with the peak of electricity production by vertical stationary PV-modules with a double-sided panel with an \"East-West\" orientation. However, the evening peak of electricity consumption is shifted relative to the electricity production by such PV-modules later during the day, when the solar panel of the module is no longer exposed to sunlight. Another option for the use of vertical stationary PV-modules with a double-sided panel with \"East-West\" orientation is their location along highways that run perpendicular to the parallels. In this case, their compactness is useful. There may also be an option of combining vertical stationary PV-modules with a double-sided panel with an \"East-West\" orientation with PV-modules with a \"South\" orientation. The results of our analytical calculations (Tables 1 and 2, as well as Figures 2-7) are indirectly confirmed by the results of experimental studies by the authors of [38,45,46]. Papers [38,45] provide a comprehensive evaluation of PV-modules with the \"East-West\" orientation using a modeling approach. The model integrates the geographical location of the PV-modules and the corresponding solar irradiance data. A comparative analysis is carried out between \"South\"- and \"East-West\"-oriented PV- modules, focusing on energy cost efficiency and technical requirements.