Local grid vs. global emissions: electric vehicle charging

Challenge

Electric vehicles (EVs) are expected to replace internal combustion vehicles in most countries, as a means to decarbonize transportation. This transition leads to an increased demand for electricity to charge the cars. When compared to a typical residential household or retail building, EVs may double or even triple the peak power drawn, depending on the capacity of the installed EV charger. The electrical grid, especially with regards to distribution level infrastructure, must be equipped to deal with this increased peak demand. Furthermore, even though EVs have lower lifetime environmental impact than internal combustion engine vehicles, emissions arising from charging are dependent on when, where and how cars are charged.

Therefore, the choice of charging strategy may involve trade-offs between overloading local transformers supplying residential households (and risking loss of load), and the resulting emissions from charging.

Approach

We simulate EV charging at home with three different charging strategies that vary in terms of the charging scheme (controlled or uncontrolled charging) and the time of plug-in of the EV for charging. We rely on real-world GPS-tracked mobility profiles measured across 909 internal combustion engine cars in Northern Italy over a period of almost two years for accurate mobility energy needs and parking locations and duration of the cars. Using the simulated demand, we estimate the overloading of the local distribution transformer under varying fleet sizes and EV penetration levels within an Italian neighbourhood, using typical residential load profiles. Finally, we estimate the emissions caused by EV charging in the three charging strategies, and report observed trade-offs between transformer overloading and carbon emissions, thereby providing suggestions on appropriate charging strategies to choose depending on the objectives of the local community operator.

Funding

This research is funded by the Bavarian State Ministry of Science and the Arts, in a program coordinated by the Bavarian Research Institute for Digital Transformation (bidt).

Team

Prakhar Mehta, Verena Tiefenbeck, Thorsten Staake (University of Bamberg)