# Analysis, Evaluation and Simulation of Railway
## 3 Results and Discussion
### Cases of Study
#### 3.2.2 Hybrid Diesel-Electric and Electric Unit (HDEMU S-730)  
S-730 locomotive has been simulated through the same itinerary, studying possibilities for energy storage associated with the use of regenerative braking and changes in traction mode throughout the route Alcazar-Chinchilla. The configuration of coaches is Talgo, see Table 2. This hybrid locomotive of the HDEMU can develop a maximum speed of 180 km/h in diesel-electric mode. Speed profiles for the route are presented in Figure 11.  
Some results of the simulation for HDEMU S-730 are presented in Table 8.  
Figure 12 depicts the power demand and the regenerative energy profile on AJ-CH route.  
Figure 11: Speed profile for hybrid vehicle S-730: (**a**) From Alcazar to Cartagena; (**b**) from Cartagena to Alcazar.  
Figure 12: Power for hybrid locomotive S-730 and energy profile for the foresee ESS device. Energy draws the possibilities for storage behavior (dynamic braking fills ESS, and then these systems cover part of the demand to accelerate the unit): (**a**) From Alcazar to Cartagena; (**b**) from Cartagena to Alcazar.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Direction**} & \multirow{2}{*}{\begin{tabular}{c} **N\({}^{\circ}\)** \\ **Stops** \\ \end{tabular} } & \multirow{2}{*}{**Duration**} & \begin{tabular}{c} **Primary Energy** \\ **Consumption1** \\ **(kWh)** \\ \end{tabular} & \begin{tabular}{c} **Electricity** \\ **Demand** \\ **(kWh)** \\ \end{tabular} & \begin{tabular}{c} **Total Braking** \\ **Energy (kWh)** \\ \end{tabular} & \
\begin{tabular}{c} **Regenerative** \\ **Energy (kWh)** \\ \end{tabular} &
\begin{tabular}{c} **Average** \\ **Power** \\ **(kW)** \\ \end{tabular} \\ \hline Alcazar-Cartagena & 4 & 3 h 3 min & 5143.8 & 2702.6 & 1638.6 & 310.5 & 1020.0 \\ Cartagena-Alcazar & 5 & 3 h 13 min & 8997.0 & 3744.5 & 1335.1 & 442.4 & 1343.4 \\ \hline \hline \end{tabular}
\end{table}
Table 8: Simulation results for hybrid locomotive S-730.  
The maximum energy recovered after a braking period is 203 kWh. It is also calculated the energy that the train needs to accelerate the first minute after a stop (maximum traction effort), obtaining a value of 32 kWh (i.e., first energy up and down cycle in Figure 12).  
To store the regenerative energy and, in this way, reduce the train energy consumption, it is studied the possibility of installing an ESS based on Li-ion batteries, a HESS mixing batteries and supercapacitors, and only supercapacitors. Parameters of Li-ion batteries have been obtained from References [67; 68] and parameters of supercapacitors from Reference [69].  
The characteristics of the system are shown in Table 9.  
The state of charge of the battery energy storage system (BESS) and the hybrid ESS (HESS) is represented in Figure 13. In order to increase the batteries lifetime, the SOC remains between 30% and 80%, and the majority of the time, it is maintained around 50%. Red curves represent the supercapacitors values, and blue lines show the behavior of the batteries.  
The main problem that arises through the use of HESS-as on board energy storage system-is the higher rates of weight and volume per kWh of the supercapacitors compared with batteries (435 kg/kWh vs. 6.75 kg/kWh and 0.04 m\({}^{3}\)/kWh vs. 0.005 m\({}^{3}\)/kWh). On the one hand, excessive weight of the ESS could substantially modify the dynamic behavior of the train. On the other hand, if there is not enough space in the locomotive, it could be necessary to add a service/power car to the train to place the ESS (notice that this is not a problem for Talgo units, Table 2, because they usually integrate power coaches for diesel and electric units. In the case of Talgo IV, the reason is to cover \"hotel loads\" in the case the supply from locomotive is not available).