# Energy Efficiency Improvement of Diesel-Electric Trains Using Solar Energy: A Feasibility Study
## 2 Literature Review on the Use of PV Solar Panels in Diesel-Electric Trains  
The Indian train UNESCO became, in 2011, the first diesel-electric train that installed solar photovoltaic (PV) panels on the roofs of its coaches. A 3 kW auxiliary generator and its accessories were removed from the train with this PV system. The generated energy from the solar PV panels is stored in batteries and is used to power seven 6 W LED lights in each of the coaches as well as charging mobile phones during a five-hour journey.  
In Australia, solar farms were installed along or near the railway in addition to rooftop solar panels. All generated energy is stored in batteries mounted on the diesel-electric train. The required 0.015 GW power needed to operate the train is generated by 8% from the train's rooftops, 58% from the solar farm, and 34% from the solar railway panels [19]. Figure 2 shows the UNESCO train [20]. While Figure 3 shows Australia's train with PV solar panels [21].  
After the success of the experimental tests in India and Australia, the train companies started to build solar panels on the tunnels above trains, such as the Belgian tunnel. This  
Figure 3: Australia’s train with PV solar panels [21].  
Figure 2: The UNESCO train with PV solar panels [20].  
solar tunnel connecting Schoten and Brasschaat was the first European tunnel. It comprises 16,000 PV panels, produces about 3.6 GWh, and reduces the annual CO\({}_{2}\) emissions by approximately 2500 tons [22]. Figure 4 shows the Belgian solar tunnel [23].  
Recently, [PERSON] et al. [24] developed and optimized Lithium-ion battery sizing for a hybrid diesel-electric train to decrease fuel consumption and related emissions. Furthermore, [PERSON] et al. [25] studied a comparative assessment of traditional diesel-electric and hypothetical battery-electric heavy haul locomotive operations regarding emissions reduction and fuel savings potential. In addition, various tandem locomotive configurations have been proposed and validated. Based on the results, fuel cost savings between 22% and 30% may be achieved. Moreover, according to [PERSON] et al., [PERSON] et al., and [PERSON] et al., PV solar panels, as a well-known asset in renewable structure, have been developed. Solar-powered trains are usually put in motion by placing photovoltaic panels close to or on rail lines. This method could provide several financial advantages by improving the energy efficiency of diesel-electric trains [26; 27; 28].  
With a growing lack of funds and the fact that it is harder to generate sufficient electricity from renewable sources to power the traction system of the trains during the journey, especially in a cold climate, this method remains limited in use. In this paper, and to be more realistic for practical applications, we focus on generating energy for the equipment on board, such as heating and lighting. As such, we are displacing energy otherwise produced using auxiliary diesel generators. The feasibility will, therefore, be assessed as a function of the percentage of displaced energy by the PV solar panels installed on the roof of the trains with different climate conditions. The following sections describe the methodology to evaluate the profitability of using PV solar systems on the roof of the trains and associated opportunities.