## 3 Results and Discussion
### Discussion and Major Findings for Sun and Wind Generation over Earth's Zones
In the case of the consideration of both generations(Figure 11c), the period of time with low generation is mainly given by the night period, so that we also have an interval very similar to the previous ones, being only 15 h.  
If, instead of analyzing the impact of fixing the low-generation threshold at 20%, it is examined how the maximum duration of DF events throughout the year is affected by considering lower threshold values, Figure 12. Naturally, this results in a decrease in DF event duration, with wind generation being most impacted by this change, as solar generation is largely determined by the day-night cycle. In general, across all locations, the duration of DF events for the solar generation begins at values slightly above 20 h and stabilizes around or slightly below 20 h. Exceptions are found in areas with low solar irradiation (Figure 12c), where these durations are initially higher but also converge to around 20 h for low threshold values. However, wind generation exhibits a much greater sensitivity to the chosen threshold. In locations with high wind resources (Figure 12-1), DF durations can initially exceed 20 h--reaching over 100 h in one case--but they rapidly decrease to just a few hours as the threshold is lowered to approximately 5%. Conversely, in locations with low wind resources (Figure 12-3), DF durations for a 20% threshold reach extremely high values (thousands of hours) but drop quickly with lower thresholds, eventually reaching tens of hours for thresholds around 2%. For locations with moderate wind resources (Figure 12b), DF durations start in the hundreds of hours at the 20% threshold and decrease to around 20 h for thresholds between 2% and 5%. Figure 10: Low-generation periods (DF events) for a region with low radiation and winds: (**a**) solar PV; (**b**) wind; (**c**) both added. When combining both wind and solar resources, the aggregate DF duration generally aligns with the shorter DF duration of the two resources. This is because, in most cases, when one resource's contribution increases, its generation comfortably exceeds the imposed threshold, ensuring that the combined generation surpasses the DF threshold. As highlighted, locations with low wind resources should generally be excluded from wind energy installations. Their low capacity, coupled with high variability, leads to prolonged periods of low generation, making their exploitation impractical. On the contrary, solar resources can still be viable even in locations with relatively low insolation. Although they result in lower CFs and longer DF durations, these remain manageable. For locations with medium to high levels of both resources, a combination of solar and wind is likely the optimal approach. However, it is crucial to note that in systems entirely reliant on renewable energy, even the observed DF durations present significant challenges for ensuring energy coverage. If the threshold is set at 20%, this implies that if the demand approaches this 20% threshold, five times the required capacity must be installed. This would lead to overgeneration and consequent electric surpluses during many periods of the year, while during others, generation would not be sufficient, causing possible blackouts if backup generation and/or storage systems to deal with energy shortages were not properly sized. Figure 11: Low generation periods (DF events) for a region with high radiation and winds: (a) solar PV; (b) wind; (c) both added. Another key consideration is that energy demand is not constant over time. As such, these findings should be viewed as a general reference for system behavior. Measures such as demand-side management (DSM) will be essential to better align generation and consumption, potentially reducing the requirements for backup and storage systems. Overall, this analysis highlights the behavior and evolution of DF events depending on the type of location and the characteristics of the solar and wind resources available in the area.