## 5 Conclusions  
In this work, the latest scientific findings on the operating conditions of bi-PVs and their modeling techniques were collected and discussed. Following the review, one of the discussed modeling approaches was used to investigate the influences of the ground albedo coefficient, module height, and weather conditions on the optimal tilt angle for a fixed-tilt bifacial PV application in Bologna, Italy. Differing from previous studies that investigated multiple design/operating conditions on the equivalent incident irradiance, this paper focused on each component of the incident irradiance separately. In this way, the differences between \(\gamma_{\text{opt,r}}\), \(\gamma_{\text{opt,r}}\), and \(\gamma_{\text{opt,eq}}\) based on the magnitude of \(G^{\text{beam}}\), \(G^{\text{diffuse}}\), and \(G^{\text{ref}}\) were emphasized. Among those studied, the ground albedo coefficient was the most influential parameter. In fact, the energy yield increased by 60.5% (from 2200 kWh/m\({}^{2}\)year to 3533 kWh/m\({}^{2}\)year) when the albedo was increased from 0.1 to 0.75. The component of incident irradiance that was most affected by the ground albedo was the rear component. In fact, increasing \(\alpha\) from 0.1 to 0.9 resulted in a 431% increase in \(G_{\text{rear}}\). On the contrary, \(G_{\text{front}}\) showed only a 13% increase for the same increase in ground albedo. As \(\alpha\) increased, both \(\gamma_{\text{opt,r}}\) and \(\gamma_{\text{opt,r}}\) maximized the exposure of the surface to ground-reflected radiation. At low ground reflectivity, \(\gamma_{\text{opt,r}}\) instead shifted toward \(38^{\circ}\) in favor of \(G^{\text{beam}}_{\text{front}}\), while \(\gamma_{\text{opt,r}}\) shifted toward \(90^{\circ}\) in favor of \(G^{\text{ref}}_{\text{rear}}\). The resulting \(\gamma_{\text{opt}}\) was \(39^{\circ}\), indicating that at low ground albedo coefficients, \(\gamma_{\text{opt}}\) was the same for bi-PVs and mo-PVs. Considering the module height, this showed that even though the rear incident irradiance changed by 22%, \(\gamma_{\text{opt}}\) was not affected. A module height of 2 m was proven to be sufficient to ensure most of the gain (i.e., 4.3% of 5.5%, possible with 5 m). Moreover, such a module height allowed us to avoid the consideration of \(NU\)-related issues, as emphasized in the literature review. Likewise, weather conditions were shown to have a marginal effect on the optimal tilt angle. In fact, the difference between the annual energy yield at \(\gamma_{\text{opt}}\) and the second best  
Figure 14: Insolation magnitude (bars, left axis) of the front (blue) and rear (green) surfaces, and \(\gamma_{\text{opt}}\) (line, right axis), in different weather conditions. \(\gamma_{\text{opt}}\) was only 0.05%. In fact, weather conditions affected the resulting \(\gamma_{\text{opt}}\) only if \(G^{\text{beam}}\) was negligible with respect to \(G^{\text{diffuse}}\), as emphasized in the literature review. Therefore, it is reasonable to investigate the influence of weather conditions on the optimal tilt angle only when higher deviations, i.e., \(C_{\text{dir}}\) and \(C_{\text{diff}}\), are considered. Concerning the latitude of the scenario, if it varies within a reasonable range, the highlighted trends and relationships remain valid, even though the numerical results may naturally change. In fact, these trends hold as long as the location exhibits \(\gamma_{\text{opt,r}}\) and \(\gamma_{\text{opt,r}}\), which favor \(0^{\circ}\) and higher tilt angles (here, \(>\)38\({}^{\circ}\)), respectively, implying that \(\gamma_{\text{opt}}\) is obtained as a combination of the first two, leveraged on \(G_{\text{front}}\) and \(G_{\text{rear}}\) magnitudes. In summary, it can be stated that most optical models are designed for utility-scale applications, prioritizing reduced computational effort over a detailed module- or string-level analysis. However, the increasing deployment of photovoltaic modules highlights the need for models specifically tailored to O&M activities.