An optimization framework for planning wayside and on-board hybrid storage systems for tramway applications

Electric mobility is gaining importance on pursuing decarbonisation of transport sector. In this context, electric tramways are recognised as a clean urban collective conveyance. Strong evidences manifest the advantages of storage systems in tramway applications. Despite its apparent benefits, the planning of such kind of systems for tramway applications has received few attention in literature. This work aims at filling this gap. To this end, a novel optimization framework for planning hybrid storage systems (batteries + super-capacitors) for tramway applications on either wayside or on-board configurations is developed, which incorporates an energy management tool to effectively coordinate the different storage technologies. Specific issues related with high resolution tramway demand measurements are addressed by using data dimensionality reduction techniques and temporal representation by representative trips. The new proposal is validated for a real Cuenca - Ecuador tramway for which extensive simulations are carried out with different storage system layouts (super-capacitors, super-capacitors + batteries), and configurations (wayside and on-board) including different electrochemical batteries technologies (lead-acid, nickel cadmium and lithium ion). The results obtained show the benefits of storage systems in tramway facilities (in fact, the total cost of the project can be reduced by 71%), highlighting the importance of fast-acting technologies such as super-capacitors to handle high peak demand consumptions, while batteries are primarily dedicated to providing backup long-term storage capacity. Wayside and on-board configurations are also compared, revealing that total weight of the storage system suppose the main barrier for large capacity installation in on-board layouts.