# Financial Optimization of a Solar-Driven Organic Rankine Cycle
## 3 Results and Discussion
### Parametric Analysis
#### 3.1.2 Financial Analysis  
The financial analysis is presented through some important indexes. Figure 4a,b shows results about the NPV. The NPV is an important parameter that shows the overall gain from the investment in all their lifetime. This parameter is usually used in the evaluation of the investments but it needs the use of some parameters, such as the discount factor and the project lifetime. These parameters are not known and they are estimated, something that makes the values of the NPV to be connected with the selection of some parameters. Figure 4a shows that the NPV is maximized for collecting areas in the range of 180 up to 240 m\({}^{2}\). The overall maximum NPV is 15.71 k\(\xi\) and it is found for a 220-m\({}^{2}\) collecting area and a 14-m\({}^{3}\) storage tank volume. Figure 4b indicates that the optimum storage tank volume is up to 14 m\({}^{3}\). Generally, it has to be said that higher collecting leads to higher electricity production, but, after a limit, the gain in electricity is not so high for counterbalance the extra cost.  
Figure 5a,b shows the LCOE for the examined cases. Generally, the minimization of the LCOE is found for collecting areas close to 140 to 160 m\({}^{2}\). For greater collecting areas, the LCOE increases and so the investment viability does not increase. The optimum storage tanks are about 12 to 14 m\({}^{3}\). The minimum LCOE is 0.0969 \(\xi\) kWh\({}^{-1}\) and it is found for a 14-m\({}^{3}\) storage tank volume and a 160-m\({}^{2}\) collecting area. Higher tank volumes are not beneficial for the investments and this fact has to be taken into account when these systems are designed. Generally, the LCOE has reasonable values that are lower than the electricity price. Thus, the investment of the solar-driven ORC is viable.  
Figure 4: _Cont._  
Figure 4: Net present value (**a**) for different collecting areas with the storage tank volume as the main parameter (**b**) for different storage tank volumes with the collecting area as the main parameter.  
Figure 5: Levelized cost of electricity (**a**) for different collecting areas with the storage tank volume as the main parameter (**b**) for different storage tank volumes with the collecting area as the main parameter.  
Figure 6a,b illustrates the payback period, while Figure 7a,b illustrates the simple payback period. The results have similar trends for these indexes because these parameters show the same thing but for different scenarios. The payback period takes into account the discount factor while the simple payback period does not take into consideration any other external parameters. In other words, the payback period may be a more realistic parameter than the simple payback period but the payback period is influenced by an estimated parameter which is the discount factor. However, the optimization with these parameters leads to the same overall optimum system. Moreover, it is important to state that, in the present work, the minimization of the LCOE is matched with the minimization of the PP and SPP. The minimum payback period is 8.37 years and the minimum simple payback period of 7.30 years. These values are found for a 14-m\({}^{3}\) storage tank volume and a 160-m\({}^{2}\) collecting area.  
Figure 6: Payback period (**a**) for different collecting areas with the storage tank volume as the main parameter (**b**) for different storage tank volumes with the collecting area as the main parameter.