## 3 Results & Discussion
The extra costs for auxiliary components during the system installation almost treble the establishment cost of such a SOFC-based project, being as high as 1500-2000 \(\upepsilon\)/kW approximately [32]. More precisely, the capital investment contains the FC-stack, fuel and water valves, pumps, flow meters and pressure regulators, power electronics in combination with FC-ECU (electronic control unit), heat exchangers and burners, assembly and final components for plant's balance such as DC/DC converters, wirings, and connectors, system controller, bus bar, fuses, and several sensors all over the paths. All the above assumptions have been incorporated in Table 3, for a 5-kW FC-stack that supports the innovative natural-gas-fed power station for the AEV's charging needs. Now, regarding the above presented costs, it is important to note that a grid-connected power station is encumbered with the STLGE (special tax for low gas emissions), which is calculated by multiplying the consumed electric load measured in kWh by 0.02487 \(\upepsilon\)/kWh. For each project, the CO\({}_{2}\) emissions, presented as CEMI in Table 3, have been quantified as cash flow according to the European Union by calculating the pollutant emissions in CO\({}_{2}\). Finally, the salvage value constitutes a positive feedback for the innovative FC-based power station at the end of the project lifetime specified at 5 years, which is calculated by excluding the operating hours of the FC-stack from its lifetime (more than 40,000 h of continuous operation), and the remaining percentage can be translated as a positive cash flow. For the already-presented costs and cash flows, as Tables 2 and 3 show, it is important to estimate the discounted prices for a detailed calculation of NPC (see Table 4), which will judge the financial feasibility of the presented project. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Costs** & **Petrol Engine 208** & **Grid Connected e208** & **FC-Based 208** \\ \hline CAPC (\(\upepsilon\)) & - & - & - \\ RC (\(\upepsilon\)) & - & - & - \\ OPMAC & ENVTX (\(\upepsilon\)/year) & 156 & - \\ - & INSUC (\(\upepsilon\)/year) & 350 & 500 \\ - & SERVC (\(\upepsilon\)/year) & 150 & 60 \\ - & TYKEC (\(\upepsilon\)) & 400 & 400 \\ FUC & PETRC (\(\upepsilon\)/year) & 2100 & - \\ - & ELLDC (\(\upepsilon\)/year) & - & 369.36 \\ - & STLGE (\(\upepsilon\)/year) & - & 91.43 \\ - & CEMI (\(\upepsilon\)/year) & 78 & 66.84 \\ SAL & - & - & - \\ \hline \hline \end{tabular} RC is the replacement cost, OPMAC is the operational and maintenance cost and FUC is the fuel cost.  
\end{table} 
Table 3: Nominal cash flows. At this point, it is appropriate to mention that the initial investment (zero year) to own an electric car is excessively increased regardless of the chosen charging case, compared to a traditional ICE technology vehicle. On the other hand, the total annual costs for an AEV project are diminished up to 70% by using the innovative FC-based power station fed by natural gas (Figure 1), while the salvage value of such an innovative project at the end of the fifth year is raised up to 350% compared to that of owning a petrol engine vehicle. Finally, it is important to note that the assessment of the environmental footprint in annual cash flows is almost at zero level by using the FC-based charging station.