## 3 Results
Experimentally obtained power was compared with the maximum power point  
Figure 3:3 Effect of the module temperature on daily efficiency of each PV technology calculated for a chosen sunny day of 2015. \begin{table}
\begin{tabular}{c c c} \hline \hline  & **Temperature Coefficients** & **Temperature Coefficients** \\
**Photovoltaic (PV) Technology** & **Calculated According to** & **Obtained Basing on** \\
**Manufacturer Data** & **Experimental Data** \\  & **[\%/\({}^{\circ}\)C]** & **[\%/\({}^{\circ}\)C]** \\ \hline Cadmium telluride (CdTe) & 0.0265 & 0.0152 \\ Copper indium gallium diselenide (CIGS) & 0.0391 & 0.0102 \\ Polycrystalline silicon (pc-Si) & 0.0616 & 0.0728 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Calculated and experimental values of the modules temperature coefficient. (MPP) value at 25 \({}^{\circ}\)C, taken from the manufacturer datasheet. Calculated results depict a strong dependency of output power on the temperature only for pc-Si modules. The variation of output power for pc-Si technology modules is around 18 W (7%) with the increase of temperature from 28 \({}^{\circ}\)C to almost 50 \({}^{\circ}\)C. In terms of thin film modules, the decrease of power with temperature is much smaller (0.2-2.0 %). The daily average energy yield of 1 kWp of each technology is presented in Figure 10. The shape of the energy yield profile is similar to the shape of irradiation profile for the studied year, as shown in Figure 2. The highest energy production was noticed in summer months for all technologies due to the best irradiance conditions. During the summer period (June-August) CIGS modules produced about 3% more energy than polycrystalline Si modules, which is in agreement with observations of temperature influence in this period. CdTe modules exhibit the lowest energy production, even in summer, in spite of the small value of temperature coefficient. Energy production by CdTe technology is lower in comparison with pc-Si of 1.1-8.9% which is probably caused by its small efficiency. An exception is June, when CdTe produced 0.2% more energy per kWp than pc-Si. Monthly performance ratio (PR) calculated for each studied module technology is shown in Figure 11. PR values of CIGS array were found to be higher than that of pc-Si (from 2.5% in June to 3.5% in August). Higher energy yield and performance ratio of pc-Si modules were noticed in colder  
Figure 10: Comparison of daily average energy yield of each technology modules in 2015. Figure 9: Photovoltaic (PV) output power of the different technology modules measured at 1000 W/m\({}^{2}\) vs. instantaneous temperature of the module. period of the year, i.e., from March to May (up to 4.8%), and from October to November (up to 4.6%). In terms of CdTe modules, lower monthly PR values were noticed in comparison to pc-Si technology for the whole year (from about 1% in May to even 14% in October), with the exception of June. During winter (December-February) PR values drop significantly due to occurrence of snow cover and decrease of inverters' efficiency at low input power levels. These two problems make it difficult to interpret the PR results obtained in winter, and thereby to assess the particular PV technologies in this period. Most of the months (March-October) are characterized by better insolation (Figure 2) and PR value above 80% (even 90% for pc-Si)