## 3 Results and Discussion
### Baseline Case Study of the Solar ORC System Performance
#### 3.1.1 Cycle Efficiency  
The cycle efficiency is evaluated to provide a broad indication of the influence of each factor on the performance of the ORC. The effect of mass fraction on efficiency depends on which fluid components make up the mixture. In general, increasing the hot source temperature will increase efficiency. Table 5 shows both the maximum and minimum values of the cycle efficiency with and without using the regenerator, respectively. It can be seen that the difference between the maximum and minimum cycle efficiency values can be as high as 10%, especially when the regenerator is used. It is observed that cycle efficiency with the use of the regenerator is higher than without its use. Using a regenerator is advantageous in the situation of the zeotropic mixtures due to their non-isothermal condensation. Zeotropic mixtures possess a better capacity to recuperate the low-temperature heat after the expander as against to the pure fluid. However, it is to be noted that these fluids are being operated at higher temperature than 85 \({}^{\circ}\)C; hence, in normal conditions of 85 \({}^{\circ}\)C, R245 fa/propane and isobutane/propane a have high cycle efficiency.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Working Fluid Mixture** & **Expander Efficiency (\%)** & **Mass Flow Rate (kg/s)** & **Super Heating Amount (\({}^{\circ}\)C)** \\ \hline \hline \multirow{4}{*}{R245 fa/R152a} & \multirow{4}{*}{0.2895; 0.3515; 0.429; 0.46} & \multirow{4}{*}{(for different mass} \\  & & 0.398; 0.46 \\ \cline{3-3} \multirow{4}{*}{R245 fa/hexane} & \multirow{4}{*}{80\%} & 0.15; 0.212; 0.274; 0.336; \\  & & 0.398; 0.46 \\ \cline{3-3} \multirow{4}{*}{R245 fa/propane} & \multirow{4}{*}{(for different mass} \\  & & 0.398; 0.46 \\ \cline{3-3} \multirow{4}{*}{R245 fa/hexane} & \multirow{4}{*}{80\%} & 0.15; 0.212; 0.274; 0.336; \\  & & 0.398; 0.46 \\ \cline{3-3} \multirow{4}{*}{R245 fa/heptane} & \multirow{4}{*}{(for different mass} \\  & & 0.15; 0.212; 0.274; 0.336; \\  & & 0.398; 0.46 \\ \cline{3-3} \multirow{4}{*}{R245 fa/hexane} & \multirow{4}{*}{80\%} & 0.15; 0.212; 0.274; 0.336; \\  & & 0.398; 0.46 \\ \cline{3-3} \multirow{4}{*}{R245 fa/heptane} & \multirow{4}{*}{(for different mass} \\  & & 0 for R245 fa) \\ \cline{3-3} \multirow{4}{*}{R245 fa/heptane} & \multirow{4}{*}{(for different mass} \\  & & 0.15 \\ \cline{3-3} \multirow{4}{*}{Butane/propane} & \multirow{4}{*}{0.15} \\ \cline{3-3} \multirow{4}{*}{Butane/hexane} & \multirow{4}{*}{Butane/heptane} \\  & & \\ \cline{3-3} \multirow{4}{*}{Isobutane/propane} & \multirow{4}{*}{150\%} & 0.15 \\ \cline{3-3} \multirow{4}{*}{Isobutane/hexane} & \multirow{4}{*}{5\%} & 0.16 \\ \cline{3-3} \multirow{4}{*}{Isobutane/heptane} & \multirow{4}{*}{5\%} & 0.16 \\ \cline{3-3} \multirow{4}{*}{R245 fa/heptane} & \multirow{4}{*}{5\%} & 0.16 \\ \cline{3-  
Figures 5 and 6 depict cycle efficiency as a function of mass fraction. It is observed that the relationship between cycle efficiency and mass fraction is non-linear for all the mixtures. However, it can be noticed that the mixtures with heptane and hexane as components undergo a drastic change in the cycle efficiency when the regenerator is added. For instance, isobutane/heptane has the lowest cycle efficiency with the composition of 0.25 of isobutane; however, with the regenerator it has the highest cycle efficiency with the composition of 0.4. For the remaining mixtures, the trend remains almost the same in that pure fluids have the highest cycle efficiencies and there is a local minimum, but when regenerator is added, the relationship between cycle efficiency and mass fraction for these mixtures becomes more