# Energy Efficiency Improvement of Diesel-Electric Trains Using Solar Energy: A Feasibility Study
## 4 Methodology  
This study evaluates six train journeys worldwide and under various climate conditions. The goal is to analyze the energy and financial profitability of installing PV solar panels on the roof of each the train's wagons for each of its trips. The PV solar panels are a supplementary source for the auxiliary diesel engine. These provide the train's auxiliary energy demand, such as the train lighting and operating electric tools such as TV, AC, refrigerators, and charging phones. Consequently, the study will concentrate on how much of the percentage of each wagon's consumption is provided by solar energy, which depends strongly on the train's location. The results of this study used RetScreen Expert software. This software is a comprehensive platform that intelligently enables professionals and decision-makers to rapidly identify and assess the viability of potential energy efficiency, renewable energy, and cogeneration projects. Therefore, upon using this program, users will be able to:  
* Quickly gauge a facility's energy performance using benchmarking and evaluate energy costs and savings, GHG reductions, and financing viability. * Determine the energy production and savings potential for any location in the world employing Archetypes. * Verify the performance of implemented projects and find opportunities for further energy improvements. Several parameters were considered for this study in RetScreen, as follows:  
1. The type of solar panels (PV) used: Most solar panels on the market today fit into three categories: monocrystalline solar panels, polycrystalline solar panels, and thin-film solar panels. Each of these types has different characteristics. However, according to [PERSON] [32], the polycrystalline technology panel presents the balance between costs and performance. As a result, their efficiency increased to 18-20% in the last several years. 2. The number of PV solar panels used: The solar panels are collections of solar cells. Multiple small solar cells spread over a large area can work together to provide enough power to be helpful. In the case of trains, the amount of energy produced depends on each PV solar panel's dimension and the available surface atop each wagon. For this study, one type of wagon was used: the 50-feet standard, which means that 54.49 m\({}^{2}\) are available on the roof of each train's wagon [33]. 3. The considered losses: Solar energy is subject to multiple losses in the conversion system. The solar panels' energy reaches the load and the batteries through the charge controller and the inverter. It suffers attenuation in each process whenever it passes through each component. First, solar panels (PV) can convert a small percentage, approximately 18%, of incoming solar energy into electricity. Second, the energy is stored in the solar batteries in the form of chemical energy, which can be used later to run the appliances, when there is no sunlight or during the night. Third, the battery provides energy by converting the stored chemical energy into DC electrical energy, \begin{table}
\begin{tabular}{c|c c c c} \hline \multicolumn{2}{c}{**Case Study**} & **3 rd Class (MWh)** & **2 nd Class (MWh)** & **1 st Class (MWh)** \\ \hline \multirow{2}{*}{**Case 1**} & **London to** & \multirow{2}{*}{8.06} & \multirow{2}{*}{12.14} & \multirow{2}{*}{16.21} \\  & **Edinburgh** & & & \\  & **Toronto to** & & & \\  & **Montreal** & & & \\  & **Sept-lies to** & & & \\  & **Schefferville** & & & \\  & **Luxor to Aswan** & & & \\  & **Sydney to** & & & \\  & **Henty** & & & \\  & **Champaign to** & & & \\  & **Chicago** & & & \\ \hline \end{tabular}
\end{table} 
Table 4: The annual energy consumed per each class of wagons for the case studies. with additional losses in the conversion process. Finally, the DC electrical energy passes through the inverter. The inverter's essential function converts DC electrical energy into AC electrical energy. Today's inverters have approximately 99% efficiency in converting DC into AC [34]. 4.