Figure 6 illustrates the monthly distribution of optimal PV module tilt angles across the country. A clear correlation emerges: higher latitudes necessitate larger tilt angles. The optimal tilt range spans from 0° in the summer months (June, July, August) to 47.9° in January. This suggests that maximizing solar gain during winter and autumn requires steeper PV module tilts. Conversely, shallower tilts are suitable for spring, while no tilt is needed in summer. Table 4 presents linear regression equations relating optimal tilt angle to latitude for the Erbs-Liu-Jordan model combination. Similar trends are observed in studies by Aksoy et al., Yunus et al., and Alhamer et al., confirming the latitude-dependent nature of optimal tilt angles for solar gain maximization (Aksoy Tırmıkçı and Yavuz, 2018; Yunus Khan et al., 2020; Alhamer et al., 2022).

Figure 7 illustrates the seasonal variation of optimal tilt angles across the country, based on 30 Erbs-Liu-Jordan combination models. The average optimal tilt angle ranges from 24.80° to 33.60° in winter, 17.53°–25.77° in autumn, 8.67°–16.00° in spring, and 7.47°–10.13° in summer. This trend, where higher tilt angles are required in winter and lower angles in summer for maximum solar gain, aligns with the findings of Ashetehe et al. (2022). The linear relationships between latitude and optimal tilt angle for each season are detailed in Supplementary Table S2–S5.

The analysis of 30 decomposition and transposition model combinations for optimal tilt angle estimation during autumn revealed significant variations in accuracy, with R² values ranging from 0.05 to 0.92. DISC-Reindl and Louche-Koronakis models demonstrated the highest and lowest correlations, respectively, emphasizing the importance of model selection. Anisotropic transposition models consistently yielded higher optimal tilt angles. Similar trends were observed for spring, with R² values ranging from 0.00 to 0.80. DISC-Koronakis, Orgill-Holland-Koronakis, Orgill-Holland-Liu-Jordan, Orgill-Holland-Hay, and Louche-Koronakis combinations exhibited the strongest correlations, while DISC and Erbs et al. with Liu-Jordan showed the weakest. In contrast, most models indicated a zero optimal tilt angle for summer, except for Boland-Liu-Jordan, Boland-Steven-Unsworth, DISC-Hay, Louche-Steven-Unsworth, and Orgill-Holland-Steven-Unsworth, which exhibited weaker correlations and non-zero tilt angles. This suggests the influence of the additional term in anisotropic models for diffused radiation coefficient. The winter season required substantial tilt angle adjustments, as evidenced by the higher slopes in the models compared to spring and summer. These findings underscore the importance of considering seasonal variations and model selection for accurate optimal tilt angle estimation and maximizing solar energy capture. Figure 8 illustrates the spatial distribution of seasonal optimal tilt angles across the nation.

The annual optimal tilt angle in Ethiopia, varying from 14.10° to 21.53°, is consistently higher than the latitude by 7°–10° as depicted in Figure 9. This observation aligns with previous research and highlights the positive correlation between latitude and optimal tilt angle, where higher latitudes necessitate steeper panel inclinations for optimal solar energy harvesting (Duffie and Beckman, 1980). The linear model equation used to calculate the annual optimal tilt angle is also presented in Supplementary Table S6 and Supplementary Figure S2.

Overall, while frequent solar PV panel tilt adjustments can boost energy production, the labor costs often overshadow the gains. Studies indicate that less frequent adjustments, like quarterly or annually, can still yield substantial energy increases, ranging from 0% to 19.49% across various locations across the nation (Al Garni et al., 2019; Machidon and Istrate, 2023; Osmani et al., 2021). This approach balances energy maximization with cost minimization. The optimal adjustment frequency varies based on geographic location, panel tilt, and local solar irradiance patterns. However, for most installations, quarterly or annual adjustments are sufficient to achieve significant energy yields. Frequent adjustments, though beneficial, often have diminishing returns on investment. Thus, a tailored adjustment schedule can optimize energy production while minimizing operational expenses.

Horizontally oriented PV modules in Ethiopia exhibit significant seasonal performance variations as illustrated in Table 5. Spring consistently yields the highest efficiency, ranging from 9.16% to 12.75%. Winter follows closely, with an efficiency range of 9.30%–12.34%. Autumn and summer exhibit lower performance, with efficiency ranges of 8.31%–11.93% and 6.88%–12.06%, respectively. A spatial analysis reveals that over 70% [i.e (area/total sum) × 100; for instance, the total sum of Ethiopia is ∼ 1.136 × 10⁶ km (Gao et al., 2016)] of the country experiences high efficiency (10.97%–12.75%) during spring. In contrast, over 50% of the landmass faces reduced efficiency (6.88%–9.47%) in summer. Winter and autumn demonstrate intermediate performance, with 55% and 67% of the landmass, respectively, experiencing efficiency ranges of 10.83%–12.34% and 10.52%–12.29%. Understanding this spatial and seasonal distribution is crucial for optimizing solar energy harvesting and site selection in Ethiopia. By considering these factors, stakeholders can make informed decisions to maximize the potential of solar energy in the country. For further insight see Supplementary Figure S3.

PV modules mounted at optimal angles exhibited seasonal performance variations across the nation as illustrated in Table 6. Winter proved to be the most productive season, followed by spring, autumn, and summer. Efficiency ranged from 11.59% to 14.27% in winter, 9.59%–13.36% in spring, 8.81%–12.60% in autumn, and 6.88%–12.06% in summer. This optimal tilting yielded solar gains of 0%–19.49% compared to horizontal mounting, with no tilting required in summer. To further analyze performance, landmass coverage was assessed. Over 70% of the nation experienced 12.94%–14.27% efficiency in winter, while over 50% faced 6.88%–9.47% efficiency in summer. Spring and autumn showed intermediate performance with 11.54%–13.36% and 10.72%–12.60% efficiency over 69% and 58% of the landmass, respectively (see Supplementary Figure S4). Supplementary Figure S5 also shows the increased solar energy gain achieved by mounting PV modules at the optimal tilt angle compared to a horizontal mounting.

Vertical-axis tracking significantly enhances solar energy capture, particularly during winter, as evidenced by the increased efficiency (15.11%–18.69%) compared to optimal tilt angle (11.00%–15.71%) and horizontal mounting (0%–30.68% gain). While autumn performance improves, summer benefits are minimal (0% gain). Notably, over 64% of the nation experiences high winter efficiency (16.91%–18.69%), contrasting with summer’s widespread low efficiency (6.88%–9.47%) across 50% of the landmass. Intermediate performance occurs in autumn (13.36%–15.71%) and spring (13.37%–15.63%) across 55% and 61% of the landmass, respectively (see Supplementary Figure S6). Table 7 details the seasonal performance of a vertical-axis tracking PV modules/panels. Supplementary Figure S7 also demonstrates the increased solar energy gain achieved by mounting PV modules using vertical axis tracking compared to the use of an optimal tilt angle or horizontal mounting.

Adjusting PV modules at an optimal tilt angle or implementing EW/IEW tracking significantly improved winter performance, with efficiencies ranging from 15.91% to 19.37%. This outperformed spring (13.37%–16.59%), autumn (12.83%–17.20%), and summer (9.82%–15.44%) seasons. EW/IEW tracking increased solar energy gain by 33.36%–63.00% compared to horizontal mounting, 33.36%–40.22% compared to optimal tilt, and 4.40%–33.36% compared to vertical-axis tracking. In winter, over 66% of the nation experienced 15.05%–16.99% efficiency, while summer saw a significant drop to 9.82%–12.63% over 50% of the landmass. Spring and autumn had intermediate performance, with 15.03%–17.20% (69% landmass) and 14.99%–16.59% (57% landmass) efficiency ranges, respectively (see Supplementary Figure S8). Table 8 provides a detailed breakdown of the seasonal performance of east-west axis tracking solar panels. Additionally, Supplementary Figure S9 illustrates the significant increase in solar energy yield achieved by employing an east-west tracking system for mounting solar panels compared to vertical axis tracking, optimal tilt angle positioning, or a horizontal mounting configuration.

NS tracking was found to be ineffective for low-latitude countries like Ethiopia, as confirmed by previous research Bahrami et al. (2016). PV modules with NS tracking exhibited the best performance in the spring season, with efficiency ranging from 6.42% to 10.70% as illustrated in Table 9. In contrast, winter, autumn, and summer seasons showed lower efficiency, with maximum losses of 63.00%, 40.22%, and 33.36%, respectively, compared to horizontal, optimal tilt, vertical axis, and IEW tracking (see Supplementary Figure S11). Over 56% of the nation experienced 6.42%–8.56% efficiency in spring, while winter, autumn, and summer seasons had lower coverage rates of 64%, 51%, and 56%, respectively (see Supplementary Figure S10).

Dual-axis tracking significantly enhanced solar energy generation, especially in winter, compared to other tracking mechanisms or fixed-tilt installations. Winter PV module efficiency ranged from 15.91% to 19.37%, surpassing spring (13.69%–16.99%), autumn (12.82%–17.27%), and summer (10.29%–15.82%) as illustrated in Table 10. The maximum solar energy gains relative to fixed-tilt, vertical-axis, IEW, and NS tracking were 62.99%, 40.26%, 37.71%, and 14.64% in winter, respectively (see Supplementary Figure S13). Notably, dual-axis and EW/IEW tracking yielded similar performance, particularly in winter and autumn, suggesting that EW/IEW tracking is a cost-effective alternative. Over 66% of the nation experienced high winter efficiency (17.65%–19.37%), while spring, autumn, and summer saw 70%, 57%, and 51% of the landmass with efficiency ranges of 15.35%–16.99%, 15.02%–17.27%, and 10.26%–13.04%, respectively (see Supplementary Figure S12).

The annual performance efficiency of PV modules ranged from 8.73% to 17.19%, with dual/full tracking yielding the highest performance, followed closely by EW/IEW tracking as illustrated in Figure 10. Compared to horizontally mounted modules, dual/full tracking increased annual solar energy gain by up to 50.62%, while EW/IEW tracking increased it by up to 1.22% as presented in Figure 11. This suggests that implementing yearly optimal tilt angle for south-facing PV modules with EW/IEW tracking might be sufficient, potentially eliminating the need for specific IEW tilt angle calculations. Table 11 provides a detailed breakdown of the annual performance of PV module/panel at different scenarios.

Solar tracking systems can significantly enhance solar energy harvesting, but their maintenance and operational costs pose significant challenges (Lorilla and Barroca, 2022; Sadat-Mohammadi et al., 2018). The moving parts of these systems are prone to wear and tear, particularly in harsh environments (Walker et al., 2020). Complex electrical components are also susceptible to failures and degradation. Access to skilled technicians and spare parts, especially in remote areas, can further increase maintenance costs and downtime. Therefore, a thorough evaluation of these factors is crucial to assess the overall cost-effectiveness of solar tracking systems in specific applications.