# Energy Efficiency Improvement of Diesel-Electric Trains Using Solar Energy: A Feasibility Study
## 1 Introduction
Therefore, typically, installing PV solar panels in the rail sector improves energy-savings and emissions reduction in the rail sector, especially those based on primary fuel, and is a step forward to achieving the goal in 2050, mentioned previously. It is essential to note that railway transport has improved in energy efficiency from 1990 to 2014: 13% less energy is required to move a passenger 1 km and 19% less energy to move a ton load 1 km. As a result, from 1990 to 2009, total CO\({}_{2}\) emissions from the European railways were reduced by 32%. The passenger-specific emissions (per passenger-km) were reduced by 20% and freight-specific emissions (per ton-km) by 38% [15]. However, this is not yet enough, because the International Union of Railways (UIC) and Canadian Electrical Raceways (CER) have already established a new target for 2030. The UIC studied and documented the feasibility of the 2030 targets in the technical report \"Moving towards Sustainable Mobility: European Rail Sector Strategy 2030 and beyond\". The targets were set in December 2010 by the UIC and CER. Since 2011, the progress toward the 2030 targets has been monitored and reported on yearly by the UIC (technical document: \"Monitoring report to 2020-2030 UIC/CER strategy targets\") [16]. \begin{table}
\begin{tabular}{c c c c c c} \hline
**Global Installed PV Power (GW)** & **2016** & **2017** & **2018** & **2019** & **2020** \\ \hline OnGrid & 294.8 & 389.579 & 482.912 & 583.872 & 709.674 \\ OffGrid & 2.278 & 2.908 & 3.61 & 4.059 & 4.293 \\ \hline \end{tabular}
\end{table} 
Table 1: Global installed PV power (GW) [5]. The new recommendations were as follows:  
* Reduce the specific final energy consumption from train operations by 30% compared to 1990. * Reduce the specific average CO2 emissions from train operations by 50% compared to 1990. The railway sector includes diesel (shown in Figure 1) and electric trains. Although electrified vehicles have been in use in railway applications for over 100 years, trains with energy-independent, diesel-based drives are still primarily used in the world's railway networks. For example, until 2020, only 38% of the heavy mainline railways in Bretagne were electrified [17]. Therefore, the work to improve the energy efficiency of diesel-electric presents a fundamental challenge in the world, especially in reducing fuel consumption and GHG emissions. Installation of photovoltaic solar panels on the roof of diesel trains had already begun in 2011. Previously, the profitability calculation was based on the estimation of weather conditions and the theoretical efficiency of solar panels, which led to unsatisfactory results and difficulty in accessing data. The originality of this work is to propose a simple energy approach to calculate the feasibility and profitability of using PV solar panels in diesel-electric trains based on the use of RetScreen software. RetScreen provides easy access to weather conditions associated with the geographical position of the train. In addition, it provides the possibility to the user to select any photovoltaic solar panels and find the actual solar energy produced by the panels. Moreover, this software can complete feasibility studies by providing technical, financial, and risk analyses related to electricity produced using renewable sources. Nevertheless, in our case studies, the energy produced by PV solar panels will be used to replace the energy produced by the auxiliary generator used to operate the auxiliary equipment. Therefore, the profitability was measured as the percentage of solar energy from the total energy produced by the auxiliary generator of the train, either 0% (the energy produced does not cover anything) or 100% (fully covered). As a result, the RetScreen results are adjusted to the type of application in this study. This study is divided into six sections. Section 2 presents a brief literature review on using PV solar panels in diesel-electric trains. Section 3 presents the six studied cases of the train's journey worldwide in different climates.