Stationary and on-board storage systems to enhance energy and cost efficiency of tramways

• One important bonus of tramways comes from the reversibility of electric drives.
• Braking energy of trams can be recovered in storage systems.
• High power lithium batteries and supercapacitors have been considered.
• Storage systems can be installed on-board or along the supply network.
• A simulation tool has been realised to achieve a cost/benefit analysis.

Nowadays road transportation contributes in a large amount to the urban pollution and greenhouse gas emissions. One solution in urban environment, also in order to mitigate the effects of traffic jams, is the use of tramways.The most important bonus comes from the inherent reversibility of electric drives: energy can be sent back to the electricity source, while braking the vehicle. This can be done installing some storage device on-board trains, or in one or more points of the supply network. This paper analyses and compares the following variants:
• Stationary high-power lithium batteries.
• Stationary supercapacitors.
• High-power lithium batteries on-board trains.
• Supercapacitors on-board trains.When the storage system is constituted by a supercapacitor stack, it is mandatory to interpose between it and the line a DC/DC converter. On the contrary, the presence of the converter can be avoided, in case of lithium battery pack. This paper will make an evaluation of all these configurations, in a realistic case study, together with a cost/benefit analysis.