Solutions for Retrofitting Catenary-Powered Transportation Systems Toward Greater Electrification in Smart Cities

Highlights: What are the main findings? Catenary-powered transport systems do not need substantial infrastructure updates to support a huge increase in load demand that can reach up to 4 times the current daily energy demand. A neutral impact on the overall operational efficiency of the catenary system can be achieved if the round-trip efficiency of the converter–battery block is at least 90.0%. Some scenarios with bigger battery pack capacity require 94.4% of round-trip efficiency. What is the implication of the main finding? Scalability of catenary-powered systems: The work demonstrates that trolleybus networks (case study) are a scalable, robust, future-proof option for cities looking to electrify or expand their public transportation without incurring significant costs related to infrastructure reinforcement. Efficiency requirements for battery systems integration: Achieving the mentioned levels of round-trip efficiency for the converter–battery block might become more challenging, potentially requiring more stringent system monitoring and optimization. Catenary-powered networks are expected to play a pivotal role in urban energy transition, due to the larger deployment of electric public transport, in-motion-charging (IMC) vehicles, and catenary-backed electric vehicle chargers. However, there are technical challenges that must be overcome to ensure the successful utilization of existing networks without compromising vehicle performance or compliance with network standards. This paper aims to validate the use of battery energy storage systems (BESS) built from second-life batteries as a means of retrofitting catenary-powered traction networks. The objective is to increase the network robustness without creating a negative impact on its overall operational efficiency. Consequently, more electrification projects can be implemented using the same network infrastructure without substantial modifications. Furthermore, a power management scheme is presented which allows the voltage and current range allowed in the catenary network and the BESS maximum charging rate to be controlled from user-defined values. The proposed control scheme is adept at customizing the BESS size for the specific application under consideration. Validation is performed on a case study of the trolleybus system in Bologna, Italy.