Parameters affecting braking energy recuperation rate in DC rail transit

Rail systems are well-known for their energy efficiency. Energy resources used in mass rail transit systems is predominantly electricity around the world. Energy consumption of a wide mass rail transit network operator in a city can easily be the biggest electricity consumer of the city. Therefore, it is very important that the efficiency is increased. This is also an essential requirement for sustainable development. Some trains used in mass transit systems are equipped with regenerative braking. This allows trains to brake in regenerative mode and feed the other trains on the line, if there is a demand. Researches showed that up to 40 % of the total traction energy consumption could be supplied by this regenerative braking energy, if it is 100 % used. This usage rate depends on many different parameters such as train operation frequency (headway), train-set auxilary power consumption rate, nominal braking acceleration rate, braking effort vs. velocity curve of trains. Power system configuration such as substation locations and distances, catenary system resistance, and nominal power feeding voltage level has also considerable effect on recuperation rate. In the paper, some of these parameters' impacts will be examined with the help of a multi-train, multi-line DC rail system simulator. The results will be given in comparison tables and discussed. Lastly, new emerging technologies such as flywheels and super capacitors to capture the un-used braking energy will be briefly given.