Design of a Hybrid Storage for Road Public Transportation Systems

Cost and reliability of energy storage systems are key factors for the electrification of road vehicles such as buses. In this work, authors propose a hybrid storage system in which a relatively small electrochemical battery is coupled with an array of super-capacitors. Super-capacitors are sized in order to store the energy needed to perform the travel between two bus stops. Each bus stop is equipped with a fast recharge system able to completely recharge super-capacitors in about thirty-sixty seconds. In this way on board batteries are used only as a backup source to compensate some unavoidable tolerances in the design of the system and to assure a residual autonomy that should allow a robust behaviour of the system respect to real perturbed mission profiles. In this work, proposed storage technology is applied to an existing electric bus as an advanced retro-fit kit. The aim of this activity is to demonstrate the feasibility of the proposed solution on a small cost prototype, using a technology that should be massively introduced also on existing vehicles with sustainable conversion costs. This work is mainly focused on the design of the system that have to be installed on the chosen prototype for future experimental activities.