Vehicle-to-grid application with hydrogen-based tram

Abstract

Hydrogen is acquiring a central role in energy uses, aiming to support and, then, replace conventional sources. Innovative smart-grids are based on new concepts of energy production and distribution, focus of research studies and preliminary prototypes. In this field, fuel cell-based vehicle-to-grid applications can be a useful system as a back-up power device during energy oscillations and as a transportation mode, especially in public service. In the present paper, a fuel cell hybrid tram is numerically tested, modelling dynamically each main component, with the aim to operate as a power and heat supplier, during the night, and as an urban light rail vehicle, during the day. The fuel cell model is developed, highlighting the principal elements of stack, auxiliary and heat-water management sub-systems. Performance improvements, such as regenerative braking and cogenerative processes, are taken into account, conceptualizing an innovative cooling method. In addition, a 3D CAD model is built to define a suitable layout for the hybrid powertrain, following safety guidelines. In the simulation campaigns, encouraging results are achieved for the case study analysed: for daily operations, the fuel cell-based powertrain provides approximately 2 MWh, consuming 108 kg of hydrogen (48 kg in vehicle-to-grid mode and 60 kg in mobility mode) and reaching an overall efficiency of approximately 43%. In addition, during vehicle-to-grid mode, the tram supplies thermal power capable of warming up at 45 °C almost 0.2 kg/s of tap water on average, obtaining a cogenerative efficiency that exceeds 60%. The promising performance achieved could represent the first steps of the proof of feasibility for this innovative technology.