Impacts of heavy duty electric vehicles on electric power distribution grid

Abstract

A promising way to decarbonize transport and reach global climate goals is to replace internal combustion engines with electrically driven ones powered by on-board batteries. These can be charged with renewable electricity, greatly decreasing the operational emissions of the vehicle. The charging of such battery-electric vehicles will produce new demand in the electricity grid that the grid operators did not have to take into account in the past. This can present new challenges to the stable operation of the grid, especially for the case of heavy-duty electric vehicles (HDEV), which have a significant power and energy demands.

The goal of this thesis is to create a model for assessing the impacts of HDEV charging on the electricity grid. The model is then applied to the particular case of the electricity distribution grid in the city of Oulu to gain insights into the possible challenges faced by the grid operator. The model is created by combining an open-source power flow toolbox with a model for vehicle traffic and existing electricity demand in the city of Oulu and allows to assess the stress on the individual grid elements. Two families of scenarios are investigated, corresponding to the estimated state of electrification in early 2030s and around 2040. Both light and heavy transport electrification is taken into account. Several locations of charging stations in the city are considered.

The results show that low-level electrification expected in early 2030s presents a possible risk of exceeding transformer power if all HDEVs are charging at a single charging station, chosen to be in the industrial area near the harbor of Oulu. In the 2040 scenario with higher-electrification, several transformers are exceeding their rated capacity even when multiple charging stations are deployed around the city to spread the demand. These impacts can be lessened by employing local battery energy storage at the point of the charging station, or shifting demand to the overnight charging. The results indicate that within the next decade the grid of the city of Oulu has sufficient capacity to handle the increased demand due to the electrification of transport. By 2040 a need for development of new infrastructure can be expected, to satisfy the growing demand. The developed model is general and can in principle be applied to assess a general urban grid provided sufficient data are available.