Energy harvesting for on-board railway systems

Greenhouse effect due to CO₂ emission is a global emergency issue affecting all human activities, including transportation systems. With the aim of reducing greenhouse gas emissions of the transport systems, the evolution of railway systems is toward environmental sustainability and energy efficiency. In this paper, a study about the use of energy harvesting to integrate the powering system of trains is presented. Currently available technologies are analyzed and photovoltaic systems are selected being technologically mature, since until now only big solar plants are considered as energy source for railways, and few studies have investigated solutions local to the trains. However, these studies date back to the early 2000s when photovoltaic technology was not sufficiently mature for this field of application. Taking advantage from the technology evolution the presented evaluation show by simulation that the electricity production can be increased until 400% with respect to the early 2000s. Furthermore, simulation results show that new power optimization solutions based on micro-inverters and on decoupling the PV modules of a string allow overcoming the limitation due to not optimal panel orientation on the train roof, train movement and shadows, increasing the production from 2 to 25%. The proposed approach can make the railway system more attractive for users sensitive to environmental issues and can promote intermodal connections with other green solutions for urban and local transport.