###### Abstract
Most of the aforementioned studies on CPC collectors have been performed experimentally, which in some cases could be costly due to the manufacturing process to obtain an optimal design and/or the necessary equipment and instrumentation to monitor temperatures in the CPC system. Numerical modeling is a useful tool to complement experimental studies that have been employed to better understand solar collectors and improve their design. [PERSON] et al. [18] used ray tracing simulations to obtain the optical and thermal performance, along with the energy distribution around the absorber of a CPC to improve the geometry design of a solar water heater integrated with a CPC collector; they proposed a new system design, with an improved optical performance and a concentration ratio of 1.34, that reached a maximum temperature of 65 \({}^{\circ}\)C. [PERSON] et al. [19] developed a ray tracing model to analyze the thermal performance and efficiency of a CPC collector with a concentration ratio of 3.06. They found that their model predicted a maximum efficiency of \(\sim\)57% with a relative error of less than 10%, when compared to the experimental results. [PERSON] et al. [20] carried out computational fluid dynamics (CFD) simulations to investigate the thermal performance of a flat plate solar collector. They found that the CFD model could predict the outlet water and absorber temperatures with a maximum relative error of 5.4% and 2%, respectively, when compared to the experimental measurements. [PERSON] et al. [21] used CFD simulations to investigate the performance of a solar flat plate collector with fins integrated with a layer of phase-change material (PCM). They found that the average solar collector efficiency increased from 33% to 46% on a summer day when a PCM with a melting temperature of 35.4 \({}^{\circ}\)C was used. They also found that the incorporation of fins increased the storage capacity of the system. [PERSON] and [PERSON] [22] used ray tracing analysis and CFD simulations to study the thermal and optical performance of a CPC collector and to optimize its design. They found that temperature gain from the inlet to the outlet predicted by the simulations on a spring day only diverged by 6.7% on average from the experimental results. They also proposed a modified reflector geometry that improved the optical efficiency of the collector by 5.74%. [PERSON] et al. [23] employed ray tracing simulations to calculate the solar irradiance on the receiver of a CPC collector equipped with a transparent polymer foil. They also used CFD simulations to predict the temperature rises of the collector in the range of 20-81 \({}^{\circ}\)C with a relative error of less than 3.7%. They found that the installation of the foil increased the thermal efficiency of the CPC collector when compared to a collector without foil. [PERSON] et al. [PERSON] et al. (2018) combined an optical simulation with a finite element method (FEM) simulation to improve the design of a medium temperature non-tracking CPC collector with a pentagon absorber. They found experimentally that the solar collector had an optical efficiency of 64% and a thermal efficiency of 50% at 200 \({}^{\circ}\)C, and a stagnation temperature of 378 \({}^{\circ}\)C, which was also predicted by the numerical simulations. [PERSON] et al. [PERSON] et al. (2019, 2020) used FEM simulations to perform a heat transfer analysis on a CPC system, with solar cells, and with and without a cover, to optimize its geometry and increase the efficiency of the system. They found that the FEM simulations predicted the temperature, power and efficiency of the whole system with average discrepancies of less than 12% with respect to the experimental data. They also found that the best performing configuration was the uncovered CPC.