Optimization of Infrastructure Investment for Decarbonization of Public Buses Through Electricity and Hydrogen : The Case Study of Umeå

Abstract: Battery electric vehicles and fuel cell vehicles, i.e. hydrogen vehicles, are promising alternatives to internal combustion engine vehicles to reduce GHG emissions from the transport sector. EV charging and hydrogen refuelling infrastructure is crucial to the deployment of alternative fuels in transport. Although several studies have analyzed electric public buses infrastructure, fuel cell buses have not been the target of such extensive analyses. Additionally, there is a gap in the literature regarding the comparison of infrastructure for these two types of vehicles and their cost and refuelling schedule differences. The study aims to conduct a techno-economic analysis of electricity versus hydrogen refuelling infrastructure to decarbonize public buses, using renewable sources to produce renewable electricity and green hydrogen. The outcome is a proposed system design regarding the size of the refuelling station, storage system capacity, renewable energy capacity, on-site hydrogen production system size, and the optimized refuelling schedule. The system is modelled to minimize the overall system cost while maintaining the current bus service level. The impact of electricity market prices, demand charges and varying bus energy demand in the optimal system configuration and schedule is also addressed. Scenarios are developed to study different levels of new installed renewable capacity integration and how these affect the cost, bus refuelling schedules and infrastructure design. The mixed-integer linear programming problem was modelled using Python. The model is applied to the case study of one bus line in Umeå. One terminal station was chosen to place the refuelling stations. The results show that the most economical option is electrifying the line with electricity supply only from the grid. For scenarios with additional renewable energy capacity installed, the option with 50% integration of new installed capacity is the most economically viable. In both these cases, there is no installation of BESS at the charging station. Electric buses infrastructure is cheaper than hydrogen infrastructure in all scenarios, but these values converge as renewable energy integration increases. For hydrogen infrastructure, the scenario with 50% renewable energy integration is the least costly. Although electric bus infrastructure is more economical than hydrogen infrastructure, hydrogen buses present advantages in terms of significantly higher range and thus higher flexibility for refuelling. Therefore, in the decision-making process to replace a fossil fuel bus line with an alternative fuel bus line, one must consider the multi-dimensional level of the different options.