# Energy Efficiency Improvement of Diesel-Electric Trains Using Solar Energy: A Feasibility Study
## 5 Results and Discussion
### Comparison and Analysis  
The profitability results for the six cases shown in Table 5 are in terms of ROI (years), capacity factor (%), annual solar production (MWh), and CO\({}_{2}\) emission reduction revenues ($).  
Figure 8: GHG emission reduction’s inputs in the case of the London, United Kingdom.  
Figure 9: Financial inputs in the case of London, United Kingdom.  
Case 4 has the highest capacity factor and annual solar production (MWh). The location of case 4, in North Africa (Egypt), benefits from a very high solar resource. On the other hand, case 1 has the lowest annual solar production (MWh) in the UK, resulting from the lowest solar energy availability. Additionally, the cases located in cold climates produce slightly less energy than the others, such as cases 2 and 3.  
The ROI (years) is inversely proportional to the annual solar production (MWh) as well as CO\({}_{2}\) emission reduction revenues ($). In detail, the ROI values range from 2.5 years (case 4) to 9.1 years (case 1), while the CO\({}_{2}\) emission reduction revenues range from $460 to $998 per year. Therefore, the ROI values are appropriate for such a project, except for the first case, where the ROI is considered very high. Table 5 shows the annual solar energy production for each case study.  
As mentioned in the introduction, installing PV solar panels on the train roof reduces fuel consumption associated with auxiliary diesel generators. Figure 10 shows the profitability of using this technique regarding the percentage of each wagon's consumption, as provided by solar energy/journey (ratio). The minimum fuel reduction of auxiliary generators per year is above 0.5, proving this solution's feasibility and reliability.  
According to Figure 10, cases 3 and 4 are the best, with over 100% of the energy provided by PV solar panels in all the wagon's classes. This performance is due to the lower energy consumed in these two cases, which depends on the number of trips per week. However, the energy production in case 4 is considerably higher than in case 3 because the available solar resource in Egypt (case 4) is significantly higher than in Quebec (case 3). Inversely, cases 1 and 2 are the worse. Only the third class wagon's energy can be covered at 100 % from PV production due to the higher annual energy consumed in these two cases. Energy production for case 2 is better than for case 1 as solar irradiation is higher in southern Canada (case 2) than in the United Kingdom (case 1). Moreover, case 5 is characterized by high annual energy consumption and significant PV energy production.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \begin{tabular}{c} **Case** \\ **Number** \\ \end{tabular} & \begin{tabular}{c} **Journey** \\ **Factor (\%)** \\ \end{tabular} & \begin{tabular}{c} **Capacity** \\ **Factor (\%)** \\ \end{tabular} & \
\begin{tabular}{c} **Annual Solar** \\ **Production** \\ **(MWh)** \\ \end{tabular} &
\begin{tabular}{c} **ROI (Years)** \\ **Reduction** \\ **Revenues (S)** \\ \end{tabular} \\ \hline
**1** & \begin{tabular}{c} **From London to** \\ **Edinburgh** \\ **From Toronto to** \\ **Montreal** \\ **From** \\ **3** \\ **Schepf-Iles to** \\ **Schefferville** \\ **4** \\ **From Luxor to** \\ **Aswan** \\ **From** \\ **5** \\ **Stydney to** \\ **Henty** \\ **From** \\ **6** \\ **Champaign to** \\ **Chicago** \\ \end{tabular} & \begin{tabular}{c} 9.9 \\ 13.9 \\ 11.6 \\ 12.4 \\ 21.5 \\ 17.0 \\ 15.3 \\ 13.2 \\ \end{tabular} & \
\begin{tabular}{c} 8.6 \\ 9.1 \\ 4.9 \\ 6.0 \\ 2.5 \\ 2.5 \\ 3.5 \\ 4.2 \\ 4.2 \\ 4.2 \\ 4.2 \\ \end{tabular} &
\begin{tabular}{c} 9.1 \\ 460 \\ 644 \\ 574 \\ 998 \\ 790 \\ 71