## 4 Experimental Results
### Optical-Energetic Analysis of a Concentrating PV System with the Developed Solar Tracker  
Despite the gain in energy production of a PV panel by using STSs, these systems are not usually used because of their high cost [41]. In contrast, in CPV and CSP systems, the STSs are mandatory because of the implementation of optics elements that redirect the Sun's rays towards a specific target, which establish a significant angular dependence of the systems [42]. CPV technology has a higher performance than conventional photovoltaics since it can reach conversion efficiencies of over 47% [43]. Its construction and implementation, however, is more sophisticated. Energy generated by a CPV module is mainly affected  
Figure 12: Solar tracking on 20 October 2021: (**a**) azimuth and zenith axes STEs and (**b**) DNI. by changes in irradiance levels, temperature, spectrum and, above all, by the misalignment of the module towards the Sun's rays, as with any kind of PV device [44]. It is well known that the solar tracking accuracy tolerance depends on the acceptance angle of the CPV module, which commonly is tenths of a degree. Small STEs could generate  
Figure 14: DC energy generated: fixed-tilt PV system versus PV system with solar tracking. Figure 13: Net PV electricity generation per day: **(a)** 21 March 2022, **(b)** 24 June 2022, **(c)** 20 September 2022 and **(d)** 21 December 2022.  
a significant decrease in optical efficiency, and thus, a less useful energy production in these systems [45]. In this work, Tonatiuh software was used to analyze the performance in a CPV module with the developed STS, which is an open source ray tracer tool for the optical simulation of solar concentrating systems [46]. Figure 15 depicts the schematic of a CPV module based on a point-focus Fresnel lens that was employed in the simulation. This lens reorients the Sun's rays towards a secondary optics element that uniformly distributes the radiation in the CPV cell. In Figure 15a, the CPV module is perpendicular to the Sun's rays: STE = 0\({}^{\circ}\). In Figure 15b, the module has a misalignment (STE \(\
eq\) 0\({}^{\circ}\)); thus, the Sun's rays can fall outside the cell because of tracking error. The script model followed in this simulation considers a CPV module with a 280 \(\times\) 280 mm polymethylmethacrylate (PMMA) point focus commercial Fresnel lens and a 220 mm focal length. As a receiver, a flat surface of 10 \(\times\) 10 mm is considered, simulating a multi-junction (MJ) solar cell. Four scenarios with different misalignment levels between the incident rays and the Fresnel lens were simulated in Tonatiuh software [47] to estimate the radiative flux distribution in the MJ cell, as shown in Figure 16. Considering an ideal situation in the first case, where the STE = 0\({}^{\circ}\), the normalized radiative power (NRP) is equal to 1, and the irradiance distribution is higher at the center of the MJ cell than at the edge, as Figure 16a illustrates. In the second case (STE = 0.3\({}^{\circ}\)), the STS presents a slight deviation; hence, the incident flux distribution moves towards an edge of the receiver, resulting in a 2% loss in the normal radiative power; see Figure 17. This behavior prevails as the STE increases, as shown in Figure 16c,d, with an STE of 0.5\({}^{\circ}\) and 1\({}^{\circ}\), respectively. For these cases, the normal radiative power decays 7% and 33%, respectively. Figure 17 summarizes the relationship among normal radiative power and the STE. Note that the NRP decreases as the CPV module misalignment error increases. In addition, observe that the NRP decreases drastically when the absolute STE exceeds 0.6\({}^{\circ}\), which corresponds to an NRP = 0.9. This fact is linked to the acceptance angle of a CPV module, defined as the STE at which power generation decreases below 90% [45]. As seen in Figure 17, the NRP in the CPV cell is with the developed STS. On the one hand, with the mean STE achieved in sunny days (STE = 0.39\({}^{\circ}\)), the NRP is equal to 0.96.