We congratulate Therese Lundberg, Chalmers University of Technology, on a successful PhD defence!
Title: “Energy Infrastructure for Road Transport Electrification”
Abstract:
This thesis analyzes the interactions that occur between electricity and road transportation systems. It explores the infrastructure required for the indirect electrification of heavy transport using hydrogen as an intermediary energy carrier and the direct electrification of passenger vehicles. Multiple models were developed and applied to study the infrastructural requirements for the supply of hydrogen to refueling stations and the electricity grid capacity required for home charging of electric vehicles (EVs).
A comparison of the different hydrogen supply systems, all of which use electrolysis to produce hydrogen, reveals substantial differences in the costs for supplying hydrogen to refueling stations. For the Swedish case studied, a system in which electricity is supplied from the electricity grid with onsite production at the refueling station is found to be the least-costly option, as compared with centralized hydrogen production with transportation to the station. The most-expensive option is to produce hydrogen using local solar PV and/or wind power instead of connecting to the electricity grid.
A model of the Swedish low-voltage (LV) electricity grid was developed to study the impacts of EV home charging on the LV grid as the share of EVs increases, as well as the ways in which these impacts are influenced by different network tariff designs. The results show that the number of power system violations in the LV grid (defined as exceeding the operational limits for thermal capacity and voltage magnitude) increases as the share of EVs in the vehicle fleet grows. However, the number of occurrences with violations varies significantly across geographic regions in Sweden and across EV charging cases. Even with a high level of EV penetration, some areas have zero violations, while in other areas, violations are recorded already at small EV fleet shares.
Implementing different network tariff designs significantly impacts when and to what extent it is cost-optimal to charge EVs. Thus, there are impacts on the loading of the LV grid and the flexibility that EV charging can provide to the electricity system by adapting to variable electricity spot prices. Cost-minimizing EV charging with no network tariff or a tariff for the monthly peak power demand of individual households during daytime hours provides the highest level of flexibility for EV charging from the electricity systems’ perspective, but also the highest loading on the LV grid. Having a network tariff based on the monthly peak power of individual households, including all hours of the day, results in the lowest loading on the LV grid, but also entails the lowest level of flexibility. Combining the results, a trade-off emerges between adapting EV charging to low electricity spot prices and reducing the loading on the LV grid. Implementing a network tariff for the combined peak power of all modeled households provides an alternative that lowers the loading on the grid, yet retains greater flexibility than when the cost is implemented at the household level.
Given that EV charging behavior strongly impacts the loading on the LV grid, different charging strategies in a fully electrified vehicle fleet lead to significant variation in the required transformer capacity and, thereby, the extent of LV grid reinforcement.