Electric Roads Pave the Way for Smaller Car Batteries

If an electric car charges while driving, the battery size can be reduced by up to 70 percent, and the grid load can be spread throughout the day. Charging on the go works for most people, but not for everyone. This is shown by a new study from Chalmers University of Technology, Sweden, in which for the first time researchers combined the so-called electric road system with the real-life driving patterns of Swedish drivers.

The Swedish government has proposed a ban on new petrol and diesel cars from 2030 to reduce carbon dioxide emissions. The same trend is seen across Europe, as demonstrated by the rapidly increasing sales of electric vehicles. Along with these developments, challenges have also increased, including uneven grid loads and where to charge electric vehicles.

Multiple ways of charging vehicles on the go

Several countries, including Sweden, Denmark and Germany, are testing whether electric road systems (ERS) can be used to electrify the road network. ERS fills a moving vehicle with loops in or beside a road, or by cables strung over the vehicle, similar to trams and trains. All of the variants mean that the vehicle doesn’t need to be parked to charge, and a large battery that stores less energy overcomes “distance anxiety”, a term that refers to the fear or apprehension electric vehicle drivers experience about their electric distance. the vehicle can travel before the battery needs to be charged.

Now researchers from Chalmers have used data from more than 400 passenger cars to study actual driving patterns on various parts of Sweden’s national and European roads. They have used the data to calculate, among other things, the required battery size to complete all trips with possible charging options (stationary versus ERS), charging pattern and total cost including infrastructure and battery.

Smaller batteries result in lower costs

The results show that the combination of electric roads on 25 percent of the busiest national and European roads and home charging will be optimal. Batteries, which account for most of the cost of electric cars, could get much smaller, only a third of their current size at best.

“We saw that the required battery range can be reduced by more than two-thirds if you combine charging in this way. This will reduce the need for battery raw materials, and electric cars can also become cheaper for consumers,” said Sten Karlsson, who together with research colleagues Wasim Shoman and Sonia Yeh, was behind this research – “The benefits of an electric Road System car for Battery Electric Vehicles.”

Another positive impact is that the peak of electricity consumption will be reduced if car drivers do not rely solely on charging at home but also complement it with charging on the road.
“After all, many people charge their cars after work and at night, which puts a lot of pressure on the power grid. Instead of charging more evenly throughout the day, peak loads will be significantly reduced.

Limited benefit in sparsely populated areas

But different groups of riders also have different conditions for benefiting from the combination of stationary charging and ERS.
“There were big differences between groups, depending on driving patterns and proximity to electric roads. Even in the optimal case, some will manage only by charging the electric path, while others may not use the opportunity at all. For example, we see that those who live in rural areas will need almost 20 percent greater battery coverage compared to those who live in urban centers,” said Wasim Shoman.

This study also shows that small batteries do not automatically lead to charging via ERS.
“Just because you can charge doesn’t mean consumers really want to do it at every turn. Therefore, the business model is very important because benefits and costs can be distributed unequally. And nothing has been decided yet on what the business model will look like,” said Sten Karlsson.

Facts about electric roads in Sweden

There are several short test sections with different electric road technologies in Sweden, including at Lund and in Gotland, but the first pilots with permanent electric roads are underway. The Swedish Transport Administration is building a 21 kilometer stretch between Örebro and Hallsberg alongside the E20. The electric road is expected to be completed in 2026. You can read more about the project on the Swedish Transport Administration website.

Brief study

• The article “The Benefits of Electric Road Systems for Battery Electric Vehicles” has been published in the World Electric Vehicle Journal and was written by researchers Chalmers Wasim Shoman, Sten Karlsson and Sonia Yeh.
• While the Electric Road System, ERS, is primarily being considered for trucks to enable them to travel longer distances on smaller batteries, and to avoid waiting for charging, private cars could also benefit. This is the first study to simulate battery charging by studying in detail the movement patterns of 412 privately driven cars on sections of Swedish and European national roads.
• The goal was to study what potential benefits there might be with so-called electric road systems (ERS) in which cars charge while driving. Based on that data, they calculate, for example, battery requirements, charging patterns and total cost. The researchers compared three charging scenarios, one with stationary charging and ERS, one with stationary charging only, and one with proprietary ERS charging infrastructure. Trucks or buses are not included in the analysis, so any benefit to this will be added.
• The combination of ERS and home charging is optimal and reduces battery demand by 62–71 percent in a best-case scenario. The net savings for the car owner from the smaller battery outweighs the cost of ERS.
• The average range of batteries required by residents in sparsely populated areas is 15–18 percent larger than that of urban residents.
• Stopping stationary charging is possible for many but not all vehicles.
• Using ERS can also reduce peak charging by spreading charging throughout the day.
• This research was funded by Mistra and the Energy Area of ​​Advance, at Chalmers University of Technology.
• Additional reading on environmental impact related to ERS: “If Electric Cars Are Good for Reducing Emissions, Electric Roads Can Even Better”, Environmental Science & Technology