# Analysis of Nanofluids Behavior in Concentrated Solar Power Collectors with Organic Rankine Cycle
## 3 Discussion and Analysis
This is followed by a discussion and analysis of the impact of the nanofluid concentration ranging from 1% to 50% of Al\({}_{2}\)O\({}_{3}\) in Figures 12-17 on the different characteristics of the CSP collector, such as: thermal energy absorbed by solar collector, thermal energy collected, thermal energy in storage tank, thermal energy supplied to the waste heat boiler of ORC, work produced at the ORC's turbine, and efficiencies of the CSP collector and the CSP hybrid system. On the other hand, Figure 5 compares the efficiency of the CSP collector and the efficiency of the hybrid system calculated on the basis of Equations (17) and (18), respectively. Figure 6: Efficiency of CSP collector and hybrid system at different angle of incidence and thermal oil as base fluid. Figure 7: Characteristics of the CSP collector and hybrid system at concentration of 5% of Al\({}_{2}\)O\({}_{3}\). Figure 8: Characteristics of the CSP collector and hybrid system at concentration of 20% of Al\({}_{2}\)O\({}_{3}\). Figure 10: Efficiencies of the CSP collector and hybrid system at a concentration of 20% Al\({}_{2}\)O\({}_{3}\). Figure 9: Efficiencies of the CSP collector and hybrid system at a concentration of 5% Al\({}_{2}\)O\({}_{3}\). Figure 11: Efficiencies of the CSP collector and hybrid system at different radiations and at a concentration of 20% Al\({}_{2}\)O\({}_{3}\). Figure 12: Work produced by ORC at different concentrations of Al\({}_{2}\)O\({}_{3}\). Figure 13: Thermal energy storage at different concentrations of Al\({}_{2}\)O\({}_{3}\). Figure 3.0 Efficiencies of the CSP collector at different concentrations of Al\({}_{2}\)O\({}_{3}\). Figure 3.1 Thermal energy supplied to waste heat boiler storage at different concentrations of Al\({}_{2}\)O\({}_{3}\). Figure 3.2 Power collected at CSP at different concentrations of Al\({}_{2}\)O\({}_{3}\). As expected, the data displayed in this figure show that those efficiencies are maximized at 12:00 p.m., with solar radiation of 599.674 w/m\({}^{2}\), as shown in Figure 3.3  
Furthermore, the predicted results of the CSP system Characteristics using nanofluid Al\({}_{2}\)O\({}_{3}\) are displayed in Figures 9-11. Nanofluid concentrations of 5% and 20% respectively showed that the CSP system characteristics including efficiencies are enhanced with the higher concentrations of nanofluid Al\({}_{2}\)O\({}_{3}\) over the thermal oil as base fluid presented in Figure 5 and are maximized at midday, when solar radiation is at its highest peak. Also, the depicted results of the efficiencies of the CSP and the hybrid system showed clearly that the CSP efficiency is higher than the hybrid system efficiency and peaked at the midday. Furthermore, Figures 12-15 demonstrate that the higher the concentration of the nanofluid Al\({}_{2}\)O\({}_{3}\), the higher the CSP system characteristics, such as ORC performance, thermal energy at the storage tank, and thermal energy supplied to the waste heat boiler of the ORC. Also, the maximum value was achieved by midday, at which point solar radiation is at its highest, at 599.67 w/m\({}^{2}\) measured at the site. However, Figure 14 shows that the CSP power collected and calculated by Equation (7) is not significantly influenced by the nanofluid concentrations, since Equation (7) is highly dependent on the thermal and piping losses given by Equations (3)-(6). Figures 16 and 17 display the efficiencies of the CSP collector and the CSP hybrid system, respectively, at different nanofluid concentrations. As expected, the results in these figures clearly indicate that the higher efficiencies of the hybrid system the higher the solar radiations, but, the CSP collector efficiencies are independent of the nanofluid concentrations, as per Equation (17). Figure 18 depicts the variation of the refrigerant mass flow rate of the ORC cycle at three different times during the day, and different angles of incidence of the solar radiation: 17.44\({}^{\circ}\) at 8:00 a.m., 77.44\({}^{\circ}\) at 12:00 p.m. and 137.44\({}^{\circ}\) at 16:00 p.m.