## 3 Results and Discussion
In addition to the high global irradiance that may occur at these moments in time, it can be observed that lower ambient and module temperatures are recorded on these days, as shown in Figures 15 and 16, due to cloud cover between the peaks of increased irradiance. Due to the thermal mass of the PV panel, the change in operating temperature is slow in comparison to the changes in irradiance, so if there has previously been shading by clouds, there may be a situation where there is a peak in irradiance but at that moment, there is no temperature increase equivalent to the situation where there is no cloud cover. This shading and temperature reduction results in a decrease in temperature losses in the PV panel output (Figure 17). Figure 4.8 Daily irradiance profiles registered, every 5 min, from January to December 2011. Figure 4.9 Daily profiles of the direct current, \(I_{dc}\), produced in the set of 36 PV modules during 12, 14, and 7 May 2011. Table 2.0 Daily profiles of module temperature registered during 12, 14 and 17 May 2011. Table 2.1 Daily profiles of total in-plane irradiance during 12, 14 and 17 May 2011. Table 2.2 Daily profiles of ambient temperature registered during 12, 14 and 17 May 2011. As the temperature decreases at these time instants, due to the presence of cloud shading, the response in the I-V curve of the module results in an increase in the voltage of the panels, with respect to their values without passing clouds, as can be seen in Table 2.3 As a result of the increase in voltage and current, the power generated in the panels at these times with higher irradiance values can be up to 20% higher than in the case where the irradiance values correspond to clear days (Figure 19), and this leads to an occasional improvement in the working efficiency of the PV panels during these times, when clouds are passing and the CE effect is present (Figure 20). [PERSON] et al. had previously analysed the operation of a PV panel during CE events, showing that the power could be 30% higher than the nominal power [59]. With respect to the inverter performance for each of the types of days obtained in the classifications made in this work, Figure 21 shows that the type of day also influences the efficiency with which the inverter works. The average daily efficiency of the inverter was better on days with higher daily irradiance values (H days) and lower on M days, with the lowest values obtained on L days. In this case, as opposed to what happened with the modules, the inverter worked with a higher average efficiency on days with lower fluctuations in irradiance values. Table 2.4 Daily profiles of temperature losses in PV module obtained during 12, 14 and 17 May 2011. Table 2.5 Daily profiles of the working voltage of the PV modules during 12, 14 and 17 May 2011. Table 2.6 Daily profiles of the dc power generated by the PV panels during 12, 14 and 17 May 2011. Table 2.7 Daily profiles of module efficiency obtained during 12, 14 and 17 May 2011. Figure 22 shows the working status of the inverter on the days shown as an example, which is coded by the numbers 0, 3, 7 and 10. The inverter state goes from having a value of 0, when it is not operating because there is no energy production in the PV modules, to a value or state of 3, in which the modules are starting to produce energy early in the morning, and in this state the inverter is synchronising with the grid to start injecting energy into it. State 7 corresponds to the operation of the inverter in maximum power point tracking (MPPT) mode. In it, the inverter tries to maximise the energy yield by operating the PV generator in its MPP. It can be seen in Figure 22 that on a clear sky day, with no cloud cover, the inverter operates all day in this MPPT state, until the production is so low at the end of the day that it switches back to state 3 and finally to the non-operational state 0. However, on days with passing clouds and the presence of CE, there are intervals of time when the inverter operates above the MPPT mode, a state represented by the code 10.