## 2 Materials and Methods  
The experimental system layout, as shown in Figure 1, consists of four 120W monocrystalline photovoltaic panels [24]; eight solar batteries (Gel Battery, 12V); two batteries each connected in series to obtain 24 V [25]; a 120W DC floodlight as an electric load for discharging the batteries; four PWM solar charge controllers [26]; an OMB data logger [27]; seventeen BST-TP01 [28] thermocouples; a pyranometer [29]; a multimeter [30]; a PV analyzer (PROVA 200A) [31]; a 0.15 HP pump; and a 100 L tank. Figure 2 shows the on-site experimental facilities, including the PV panels, loads, and control and measuring devices. The following are the descriptions of the components used in the experimental setup and approaches for the design or selection of each one. Figure 1: Schematic diagram of the system. Figure 2: Pictorial views of the experimental layout: (**a**) outdoor facilities, and (**b**) indoor load, control, and measuring devices. PCM selection: The experimental study was conducted at King Saud University in Riyadh, KSU, where the average ambient temperature is above 40 \({}^{\circ}\)C throughout the summer season. Therefore, the PCM melting temperature should be greater than the recorded ambient temperature of the location to stay in a solid phase. Consequently, the PCM subjected to the ambient air will perform its function only when the PV panel has a temperature higher than ambient. The PCM should also have high latent heat to maintain the PV panel's temperature around the melting point as long as possible. The second reason to consider a relatively high PCM melting temperature is to recover heat at a relatively high temperature when applying the combined passive\(-\)active approach in this study. Hence, Rubitherm RT-47 [32] was the best option for the current investigation based on its melting point temperature, which matches the ambient temperature in Riyadh. In addition, it has acceptable thermophysical properties that can lead to a better performance for the current system. The specifications of the obtained PCM are given in Table 2.  
Tube configuration: A copper tube with an outer diameter of 12.5 mm and an inner diameter of 10.4 mm was designed in a U-bend rectangular shape to cover the whole back side of the PV. The pipe configuration was made from one piece without any use of external fittings. LCPV design: The operation of PV cells under concentrated irradiance offers two main advantages: First, fewer solar cells are needed due to the objectification of an optic system to concentrate incident irradiance from the sun onto a smaller area of conventional solar cells. Second, the increase in the solar irradiation density incident on the PV cells increases their electrical output. A challenge in LCPV is the design and construction of an optical system that creates an invariant radiation profile. The electrical performance of PV cells is largely dependent on the uniformity of the solar irradiance profile, as non-uniform irradiance may lead to PV cell mismatch as well as power loss. The design of the LCPV is shown in Figure 3 and described by the following equations [33]. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \multirow{2}{*}{**Model No.**} & **Rated** & \multirow{2}{*}{**Tolerance**} & **Voltage** & **Current** & **Open** & **Short** & **Operating** & **Operating** \\  & & & **at Pmax** & **at Pmax** & **Circuit** & **Circuit** & **Clent** & **Clent** & **Temp.** & **Dimension** \\  & & & & & **Voltage** & **Current** & **Temp.** & & \\ \hline MS120M-36 & 120 W & 0\(\rightarrow\)5\% & 18.2 V & 6.67 A & 21.51 V & 7.19 A & 47 \(\pm\) 2 \({}^{\circ}\)C & \(-\)40 to +85 \({}^{\circ}\)C & 1020 \(\times\) 30 mm \\ \hline \end{tabular}
\end{table} 
Table 1: Specifications of the PV panels used in the experimental tests [32].