## 2 Material and Methods
### System Description  
In the present experiment, a dual-axis tracking system equipped with modules using concentrator photovoltaic (CPV), amorphous silicon (a-Si), polycrystalline (p-Si) and monocrystalline (m-Si) PV technologies was examined under real meteorological conditions at the same measuring point. The CPV module on the monitoring system assisted only with the accurate sun adjustment in this research (Table 2, Figures 3 and 4). \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Country (City/Town)** &
\begin{tabular}{c} **Gain in Yearly Real Energy** \\ **Production Achieved by Using** \\ **a Double-Axis Tracker System (\%)** \\ \end{tabular} & **Reference** \\ \hline Turkey (Mugla) & 30.8 & [22] \\ Canada (Vermilion) & 31 & [49] \\ Spain (Palencia) & 30.5 & [50] \\ Greece (average) & 34.5 & \\ Greece (Ilia) & 21 & \\ Greece (Serres) & 27.4 & \\ Greece (Kardis) & 37.3 & \\ Greece (Evros) & 42.2 & [19] \\ Greece (Kilkis) & 34.5 & \\ Greece (Trikala) & 34.6 & \\ Greece (Magnisia) & 39.1 & \\ Greece (Rodopi) & 42.2 & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The gain in yearly real energy production compared to optimally positioned south-facing crystalline photovoltaic (PV) systems. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Module Type** & **CPV** & **a-Si** & **m-Si** & **p-Si** \\ \hline
**Model** & **CX-75-III** & **G-EA050** & **SM636-50** & **SL50 TU-18P** \\ \hline Nominal power (Pmax) (W) & 75 & 50 & 50 & 50 \\ Performance tolerance (\%) & \(\pm\)5\% & \(\pm\)10\% & \(\pm\)3\% & \(\pm\)3\% \\ MPP voltage (Vmp) (V) & 135 & 67 & 18.18 & 19.12 \\ MPP current (Imp) (A) & 0.55 & 0.75 & 2.8 & 2.62 \\ Open circuit voltage (Voc) (V) & 150 & 91.8 & 23.17 & 22.68 \\ Short circuit current (Jsc) & 0.64 & 1.19 & 3.08 & 2.80 \\ Efficiency (\%) & 27.2 & 5.3 & 14.4 & 13.7 \\ Temperature Coefficient (\%/\({}^{\circ}\)C) & 0.15 & 0.27 & 0.5 & 0.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Technical information of the PV modules. (standard test conditions: air mass 1.5; cell temperature 25 \({}^{\circ}\)C; irradiance = 1000 W/m\({}^{2}\)/m-Si, p-Si, a-Si modules; irradiance = 850 W/m\({}^{2}\)/concentrator photovoltaic (CPV) module). Figure 4: Fisheye view of the measuring station surroundings in the summer afternoon. Figure 3: The measuring station in Keszthely (1, HYTE-ANA-1735 humidity module [measuring air humidity]; 2, Pt 100 sensor; 3, manual/automatic tracking control unit; 4, m-Si module; 5, CPV module; 6, photosensors; 7, Eppley Black and White pyranometer; 8, a-Si module; 9, p-Si module; 10, Hukseflux LP02 pyranometers; 11, EMS 11 Silicon PV detector; 12, DS-2 Sonic anemometer; 13, OTT TRH relative humidity sensor; Orange dot: Pt 100 sensors). A professional multimeter (Voltcraft VC607) (Conrad Electronic SE, Wernberg-Koblitz, Germany), verified on a LT1021 (Linear Technology Corporation, Milpitas, USA) precision reference, was used for the calibration of the current and the voltage. During the measurements oscillation true maximum point seeking (TIPS) devices were used to optimize the current (A) and the voltage (V) of the PV modules. With these devices it was possible to manually check the maximum power point of the PV modules, thus allowing a correct measurement precision (Figure 5). Moreover, it was also possible to measure the V and A values directly without any loss in the TIPS devices. Within the scope of the present study for the collection of environmental and technical data a GB HOBO (Onset Computer Corporation, Bourne, USA) four-channel analogue data logger, a CR1000 measurement (Campbell Scientific, Inc., Logan, USA) and control datalogger, a PicoLog 1012 (Pico Technology, St Neots, United Kingdom) data acquisition system and a PicoLog 1216 (Pico Technology, St Neots, United Kingdom) acquisition system were used (Figures 5 and 6).