Abstract
Although rail is one of the most sustainable transport systems, there is still room to reduce its energy demand. In particular, during the braking of DC powered trains, a significant amount of energy is wasted. The recent developments in energy storage system technologies, combined with the widely used technique of regenerative braking, can considerably increase energy saving. This paper explores this theme, quantifying the amount of braking energy that can be potentially recovered in a real case study, starting from the experimental data measured on-board train. A simplified numerical model of the recovery process has been implemented. Adopting it, the energy that can be saved, with one or two energy storage systems, has been quantified for each possible position along the track. The procedure allows to determine the optimal position. Further findings about the impact of voltage level on the efficiency of the recovery process have been reported. The optimal level of voltage has been determined, also considering the additional losses in the catenary, both during the traction and braking phase of the train. Moreover, it allows dimensioning of stationary storage systems considering two different energy management strategies and their impact on the peak of stored energy. The proposed approach will be presented with reference to the concrete case of a specific route on the Italian rail network, analyzing a train in normal commuter service and the obtained results will be discussed. In the best situation, about the 73% of the braking energy can be recovered.
Highlights
The modern railway system is widely recognized as one of the most sustainable modes of transport
Several complementary strategies that improve the energy management can be employed: timetable optimization, reversible substations or ESSs [2,3,4]. All these energy recovery strategies are based on the regenerative braking
This paper paper discusses discusses aa methodology methodology based based on on experimental experimental data data measured measured on-board on-board. This train quantifying the amount of energy that can be recovered adopting ESSs located in train quantifying the amount of energy that can be recovered adopting ESSs located in supply substations along a well-defined railway line
Summary
The modern railway system is widely recognized as one of the most sustainable modes of transport. From the energy analysis performed on experimental data recorded during the monitoring of different railway traction-units in commercial service, it results that a value ranging from few percentage points up to 50% of the traction energy is dissipated, and it can reach several hundreds of kilowatts per hour for a single journey These shares vary remarkably with line characteristics, towed mass and supply voltage amplitude; the recovery of such amount of energy could improve efficiency of the electric transport reducing overall CO2 emissions. About 44% of the railway networks are supplied in DC [5], where the braking energy can be reused only by other trains within the same network that need energy at the same time, since the traditional supply substations are unidirectional They are equipped with diode rectifiers to transfer the power from the main AC grid to the overhead contact line [6], which carries the power to the trains through the pantograph [7].
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