# Analysis of Nanofluids Behavior in Concentrated Solar Power Collectors with Organic Rankine Cycle
## 3 Discussion and Analysis
Figure 3.8 CSP system hybrid efficiency at different concentrations of Al\({}_{2}\)O\({}_{3}\) and solar radiations. higher thermodynamic and thermophysical and heat transfer properties of the nanofluid CuO which contribute to outperform other nanofluids over the base fluid thermal oil. Figure 3.9 CSP system hybrid ORC work produced with different nanofluids at different concentrations. Figure 6:0 CSP system hybrid ORC refrigerant mass flow rate with different nanofluids at different concentrations. In particular, Figure 26 clearly shows that the nanofluid CuO has the highest ORC work produced among the other nanofluids under investigation. This results in enhancing the hybrid CSP solar collector system efficiency compared to the other nanofluids under study. It can also be concluded from the results presented in these figures that, in general, the higher the nanofluid concentration, the higher the hybrid system performance characteristics. One of the significant parameters for demonstrating the enhancement of the CSP solar collector system is the ORC refrigerant mass flow rate, since this parameter impact the work produced by the ORC and the hybrid system efficiency. Figures 27 and 28 show the impact of the various nanofluids considered in this study on the aforementioned parameters. It appears that the higher the concentrations of nanofluids and the higher the solar radiation, the higher the refrigerant mass flow rate and ORC work produced and consequently the CSP hybrid system efficiency. Furthermore, Figures 25-28 also indicate that the nanofluid CuO outperforms other nanofluids Al\({}_{2}\)O\({}_{3}\), Fe\({}_{3}\)O\({}_{4}\) and SiO\({}_{2}\) and has the highest CSP solar collector performance compared to the other nanofluids and thermal oil base fluid under study. Therefore, Figures 29-31 were constructed to illustrate the impact of the concentrations of nanofluid CuO in the performance of the ORC system and the CSP hybrid system under different solar radiations at midday: 500, 750, 1000 and 1200 W/m\({}^{2}\). As can be seen in Figure 29, the thermal energy supplied by the CSP collector to the ORC loop was enhanced with higher concentrations of this nanofluid at constant solar radiation; and consequently, the ORC work produced was also increased at higher concentrations. It is found that the thermodynamic efficiencies with CuO nanofluid, under optimum conditions, are higher than those obtained from the base fluid. Also, the results displayed in this figure show that the higher the solar radiation the higher the ORC output. On the other hand, Figure 31 shows that efficiency of the CSP solar collector hybrid system is increased with the increase of the solar radiation and as discussed earlier and is independent of the nanofluid concentrations as per Equation (18). Finally, our results conclude that the combination of the ORC with the CuO nanofluid is the optimum choice for the CSP solar hybrid system, which is in agreement with what has been reported in the literature, namely, [31, 35]. Figure 6:1 CSP system hybrid efficiency with different nanofluids at different concentrations. Figure 6:2 CSP system hybrid efficiency at CuO nanofluid and different concentrations. Figure 6:3 CSP system hybrid ORC work at CuO nanofluid and different concentrations. Figure 6:4 CSP system hybrid waste heat boiler thermal energy at CuO nanofluid and different concentrations.