## 3 Results and Discussion
### Discussion  
The results presented here have shown that the design and fabrication of a small-size, low-cost and low-maintenance CPC collector is feasible, which could be used for residential applications, and at the same time promote a lower environmental footprint and sustainability by using solar energy for water heating. Among the technical advantages of the proposed CPCs are their small size and low weight. The area and weight of the proposed CPCs is 0.22 m\({}^{2}\) and \(\sim\)5 kg, respectively. This is in contrast with the area and weight of 1.1 m\({}^{2}\) and 30 kg, respectively, for the flat plate collector previously developed by the authors [41] or with the area and weight of 1.6 m\({}^{2}\) and \(\sim\)30 kg, respectively, for a commercial evacuated tube collector [42]. The small size and low weight of the proposed CPCs give them an advantage to be used in low income and remote areas, where the rooftops of some houses are small and are made of nonstructural materials. Another advantage of the proposed CPCs is the low maintenance and its associated costs because the materials for the fabrication of the CPCs are locally available and the repairs are not complicated [15]. An economic advantage of the proposed CPCs is the low fabrication  
Figure 15: (**a**) Predicted maximum temperature difference \(\Delta T\) versus mass flow rate and (**b**) predicted thermal efficiency \(\eta_{t}\) versus mass flow rate \(\dot{m}\), on 1 March 2020, with a constant inlet temperature of 27 \({}^{\circ}\)C for the different CPC absorbers. cost, which can be seen in Table 3, in which the estimated fabrication cost of the CPCs with an absorber without fins and with segmented fins as well as a flat plate collector are presented. Moreover, the retail price of a commercial evacuated tube collector is presented for illustration purposes. It can be seen that the fabrication cost of the proposed CPCs is lower than the other options. The cost of the CPC with an absorber with segmented fins is 40% higher than that of the CPC with an absorber without fins; however, the measured average efficiency of the CPC with segmented fins is 37% higher than that of the CPC without fins on a late winter day, when the need for hot water increases. It is acknowledged that a comprehensive techno-economic analysis of the proposed CPCs should be performed to carry out a fair comparison with other CPC systems available and for the assessment of the incorporation of fins to the absorber due to the high price of copper. It is also acknowledged that further studies should be performed to optimize the performance of the CPC in the wintertime, when the water is cooler, to reach a larger temperature difference between the inlet and outlet temperatures. These studies should include numerical simulations and experimental work to obtain the optimum mass flow rate, using a pump to achieve higher temperatures, without limiting the availability of hot water. The thermosiphon effect should also be investigated [41]. Further work should also include the assessment of geometrical parameters, such as fin position and size, and absorber diameter and length, and their optimization. The numerical methodology--which included the mapping of the solar power (energy), obtained via ray-tracing analysis, on the absorber surface of the FEM model and a coupled thermal FEM-CFD analysis to estimate the temperature of the water--was capable of describing the thermal performance of the CPCs with and without fins, and it could be used to predict the thermal performance of other CPCs with different geometries and configurations in order to obtain optimized designs prior to manufacturing and experimental testing. The numerical results showed that the mapping of the heat flux on the CPC absorber surface with fins should be used to obtain more accurate predictions when compared to an analysis using homogenous heat flux on the surface of the absorber.