## 4 Results and Discussion
### Sensitivity Analysis of a Typical Result  
Through the description in Section 4.2, it can be found that the simple recuperated cycle has incomparable advantages in S-CO\({}_{2}\) power generation cycles using solar energy by a parabolic trough solar collector. Even though it is difficult to carry out a complete investment recovery analysis through the specific work and the cost of core equipment, we can still conclude that the simple recuperated cycle has the best economy among the three cycle types. Therefore, a typical optimization result in the simple recuperated cycle is selected for sensitivity analysis in this section.  
The parameters in typical optimization results selected are shown in Table 6, and the rest of the parameters of the system are shown in Table 4.  
First, the cost of each core component is compared with histogram and cumulative proportion, as shown in Figure 14. It can be seen that the cost of turbine machinery, including turbine and compressor, is the main component of equipment cost. This is because the technology of other components in S-CO\({}_{2}\) power is mature, while the manufacturing of turbine machinery using S-CO\({}_{2}\) is relatively difficult and the cost is high. Therefore, it can be concluded that reducing the manufacturing cost of the turbine machinery can achieve higher economic benefits.  
Secondly, sensitivity analysis is considered on the cost of the core equipment and specific work. Since the cost of turbine machinery accounts for the main part, and the compressor inlet temperature after optimization is rather low (which resulted in less change space), the analysis variables are mainly turbine inlet temperature, turbine inlet pressure, compressor inlet pressure, isentropic efficiency of turbine, and isentropic efficiency of the compressor. The five parameters vary by -5% and +5%. The results of the sensitivity analysis are shown in Table 7.  
\begin{table}
\begin{tabular}{l l l l} \hline \hline
**Variables** & **Value** & **Variables** & **Value** \\ \hline Turbine inlet temperature & 382.76 \({}^{\circ}\)C & Cost of core equipment & 183.98k\$ \\ Turbine inlet pressure & 17.15 MPa & & \\ \hline Compressor inlet pressure & 8.82 MPa & & \\ Compressor inlet temperature & 32.35 \({}^{\circ}\)C & & \\ \hline \hline \end{tabular}
\end{table}
Table 6: System parameters in typical optimization results.  
Figure 14: Comparison of core equipment cost.  
Through the sensitivity analysis, it can be found that most of the changes of these variables only affect the cost of a single component, so the overall cost is not sensitive to them. The specific work is still sensitive to these variables. For the cost of core equipment, the change of pressure will cause great fluctuation; this is because the change of pressure affects the performance of two types of turbomachinery (turbine and compressor), resulting in a great change of cost. As for the specific work, in addition to the compressor efficiency, the influence of other parameters is more obvious, which is also reflected in Section 4.1. The influence of the system design parameters on the cost of core equipment is less than that on the specific work of the system. Therefore, in the actual process, more consideration should be given to the thermal performance of the system regarding the selection of system parameters, and the structural optimization and layout optimization of components should be adopted to reduce the system cost.