Electrification of Road Transportation - Implications for the Electricity System

Doktorsavhandling, 2019

It is incumbent upon the transport sector to reduce its CO2 emissions by replacing fossil fuels with low-carbon alternatives. Suggested strategies include electrification of the road transport sector through the use of electric vehicles (EVs) with static charging, electric road systems (ERS), and the use of electricity to produce fuels. Electrification of the transport sector will create new electricity load profiles that depend on the time of consumption and the amount of electricity used in EVs. EVs can also contribute with flexibility to the electricity system – a feature that will be of increasing importance with a higher share of variable renewable electricity (VRE) in the electricity system.

The overall aim of this thesis is to investigate how electrification of the transport sector affects the electricity system with respect to the demands for energy and power on different geographical and temporal scales. In this work, a vehicle energy consumption model is developed to estimate the variations of the energy and power demands according to time and location for the transportation work on a highway (the E39 in Norway). Furthermore, charging of passenger EVs and ERS is included in several electricity system models, to investigate how EVs influence investments in electricity generation capacity and VRE integration.  

Our results, using the Norwegian E39 highway as a case study, indicate that electrification of the road transport entails large variations in the spatial and time distributions of the energy and power demands along the road. Installation of ERS on all the European (E) and National (N) roads in Sweden and Norway would encompass more than 50% of the national vehicle traffic. Implementation of ERS on 25% of the total E- and N-roads (~6,800 km) would be sufficient to cover 70% of the traffic on these roads and would connect most of the larger cities in Norway and Sweden through ERS.

We conclude that with a cap on CO2 emissions from the European electricity system, which corresponds to 99% reduction by 2050, the demand from EV is mainly met by an increase in generation from VRE, e.g., solar power in regions with adequate solar conditions and wind power in regions with good wind conditions. Re-charging of EVs directly subsequent to driving or ERS will require increased investments in peak power (by up to ~15%), as well as, in thermal power plants compared to optimised EV charging. The model results show that an optimised charging strategy with vehicle-to-grid (i.e., discharging electricity back to the grid) that minimises the cost of the electricity system can: (i) avoid investments in other storage technologies; (ii) reduce the need for peak power capacity in the system; and (iii), for some regions, stimulate increased shares of VRE (mainly solar power), as compared to direct charging.

This thesis also shows that it is important to represent the heterogeneity of individual driving patterns in electricity system optimisation models when the charging infrastructure is limited to the home location and a battery capacity of 30 kWh or less per vehicle.