## 3 Results and Discussion
### Financial Analysis, Environmental Analysis and Further Discussion  
Section 3.5 is devoted to presenting a basic financial and environmental analysis of the examined configuration, as well as discussing the found results in detail. The default design scenario has been assumed and the total results are summarized in Table 9. In this case, the yearly electricity production is 81.16 MWh and the total production in the 25-year life of the installation is about 2029 MWh, while the mean efficiency is 19.80%. The capital cost of the investment is 118.55 k\(\xi\), the yearly income cash flow is 15.05 k\(\xi\) and the NPV is 143.5 k\(\xi\). The simple payback period and the payback period are found to be 7.88 and 9.12 years respectively, while the IRR is 11.94%. The CO\({}_{2}\) emissions avoidance is found 48.7 tons on a yearly basis and 1217.5 tons during the total life of the project. The aforementioned results indicate that the studied investment is viable, and the financial parameters are promising, especially for a renewable-based energy system. Moreover, significant amounts of CO\({}_{2}\) are avoided, and this fact proves that the system has a positive environmental impact. At this point, it is essential to compare the present system with other similar systems and other literature studies. Firstly, it has to be said that the present system is more efficient than a respective typical solar-driven ORC with PTC. More specifically, an extra simulation has been done by using a system with toluene as the working fluid and thermal oil in the PTC field, as it has been studied in Ref. [44]. The same parameters have been used in the new evaluation as in the present one and it is found that in steady-state conditions the conventional CO\({}_{2}\) has a system efficiency of 21.69% while the present system with CO\({}_{2}\) has 24.27% system efficiency. Therefore, an efficiency enhancement of 11.89% was found; a significant improvement that proves the importance of the suggested idea. In another work about a solar-driven ORC, [PERSON] et al. [45] have found system efficiency up to 15.78% which is a very lower value compared to the results of the present analysis. Moreover, another work by [PERSON] and [PERSON] [44] proved 15.38% system efficiency which is also lower than the present study. In other studies, relatively low system efficiencies have been found such as 8% with PTC-ORC [46; 47] and 12.5% [48]. The financial analysis shows that this work has a payback period of 7.88 years, while Ref. [45] found payback period around 9 years so this work has also beneficial financial evidence. Ref. [46] shows that the payback period is about 8.4 years and Ref. [49] about 12 years, values which are also higher than the values of this work. Therefore, the use of a CO\({}_{2}\)-based transcritical cycle is an idea with important energy efficiency gains and also positive financial performance compared to other ORCs. In the end, it is important to state that the examined unit faces some limitations. There is a need for operation in high-pressure levels which creates the need for designing properly the devices and the tubes in order to withstand these pressure levels. Moreover, the high-temperature levels in the PTC and in the turbine inlet create the need for using suitable materials. Another problem regards the storage technology that can be applied in \begin{table}
\begin{tabular}{c c} \hline \hline
**Index** & **Value** \\ \hline Yearly electricity production & 81.16 MWh \\ Total electricity production & 2029 MWh \\ Yearly system efficiency & 19.80\% \\ Capital cost (C\({}_{0}\)) & 118.55 \(\xi\) \\ Yearly cash flow (CF) & 15.05 \(\xi\) \\ Simple payback period (SPP) & 7.88 years \\ Payback period (PP) & 9.12 years \\ Net present value (NPV) & 143.5 k\(\xi\) \\ Internal rate of return (IRR) & 11.94\% \\ Yearly CO\({}_{2}\) emissions avoidance & 48.7 ton \\ Total CO\({}_{2}\) emissions avoidance & 1217.5 ton \\ \hline \hline \end{tabular}
\end{table}