## 5 Discussion and Analysis
This observation is attributed to the fact that the CuO higher thermo-physical properties, which are the main driver for the higher cooling effect produced and consequently, the enhancement of the hybrid system efficiency with the CuO. Figure 11: Cooling load effect produced with SiO\({}_{2}\) at different temperatures. Figure 12: Cooling load effect produced with Fe\({}_{3}\)O\({}_{4}\) at different temperatures. Figure 3:0 Cooling load effect produced with CuO at different temperatures. Figure 3:1 Cooling load effect produced with AI\({}_{2}\)O\({}_{3}\) at different temperatures. Figure 3:2 Cooling load effect for CuO at 5% concentration. In particular, Figure 16 clearly illustrates that the higher the nanofluid concentration, the higher the cooling effect produced. It has been reported by [PERSON] [18], [PERSON] et al. [19] and [PERSON] et al. [20] that transport properties such as the density, specific heat, heat capacity, viscosity, and thermal conductivity of nanofluids are function of the nanofluids concentrations and significantly impact the convective heat transfer of nanofluids [18] and obviously the cooling effect produced presented in the aforementioned figures. A comparison between the different nanofluids under investigation is presented in Figures 16-18 under different heat transfer fluid temperatures and volume concentrations: 5%, 10% and 20%. To illustrate the effect of different nanofluids on the efficiency of the hybrid system composed of PV-Thermal and ORC. The depicted results as well as others obtained showed that the nanofluid CuO as heat transfer fluid experiences the highest hybrid system efficiency compared to the other nanofluids and water as the heat transfer fluid. These findings have been reported by other references, as discussed elsewhere in the paper, namely [PERSON] [18, 28]. Clearly, it was also shown that the higher the temperature of the heat transfer fluid, the higher the efficiency of the hybrid system. This is an important finding since just by selecting the right nanofluid for a specific ORC design, the hybrid system efficiency can be significantly enhanced, irrelevant of the solar radiation, heat transfer fluid temperature and the nanofluid concentration. Obviously, as can be illustrated in these figures, the higher heat transfer fluid temperature and the higher the nanofluid concentration the higher the hybrid system effciency. Figure 3:3 Hybrid system efficiency for different nanofluids at 176 \({}^{\circ}\)F.  
Moreover, as discussed above, the cooling effect produced by this hybrid system is an important feature of the proposed concept since ORC systems are intended only to produce power. Moreover, as illustrated in this paper, the cooling capabilities are impacted by the different parameters of the PV-Thermal and ORC hybrid system; therefore, Figures 19-21 were created to demonstrate the impact of the different nanofluids and their conditions, heat transfer fluid temperatures and nanofluid volumetric concentrations, as well as solar radiations, on the cooling effect produced by this new hybrid system concept. It is quite clear from the results presented in these figures and others results obtained that the higher the solar radiation and the higher the heat transfer fluid temperatures, the higher the cooling effect produced. However, the data presented in these figures also show that the higher the nanofluid concentrations and the higher heat transfer fluid temperature, the higher the cooling effect produced. Moreover, it was also observed from the results obtained that a higher cooling effect can be produced with the use of the nanofluid CuO compared to the other nanofluids under investigation and water as the heat transfer fluid. This finding is consistent with what has been reported in the literature. It is worth noting that the heat transfer fluid temperature is not a good indicator of the heat transfer fluid temperature.