E-cars as energy storage devices: enormous savings potential

With so-called bi-directional charging, vehicles absorb excess and therefore cheaper solar and wind energy from the grid during the day and supply it back in the evening or at night. The Fraunhofer Institutes for Solar Energy Systems and for System and Innovation Research, on behalf of the EU Transport and Environment Association, have calculated the cost benefits that this two-way charging could bring to network operators and consumers.

Accordingly, in the most beneficial scenario, the extensive use of electric cars as electricity storage would reduce the investment need in the European energy network by more than 100 billion euros between 2030 and 2040. To achieve this, however, approximately half of all electric cars and battery trucks would have to be able to supply electricity back to them by 2030. If this flows directly to the entire network, this is called vehicle to grid (v2g, i.e. from car to network).

Use a car battery for your own household
Also, owners, especially in single-family homes, have the option to use the electricity stored in the car battery for their own household (vehicle to home, or v2h). The electric car could then become an energy supplier in the particularly energy-intensive evening hours and reduce electricity costs. It is then recharged at night when demand is low and electricity is cheap.

In Germany, this would allow a four-person household to save more than 700 euros per year, the study authors calculated. If it is introduced into the entire network, any compensation for the car owners would also have to be paid.

Obstacles caused by inconsistent standards
But there are some obstacles to the widespread spread of two-way technology. On the one hand, there is the power conversion problem. When charging electric cars, the alternating current in the network must be converted into direct current and vice versa. On some models this happens in the car. Others need a more expensive wall box to connect the car to. The study authors recommend a uniform standard to which manufacturers can adapt.

There are no political preconditions
Moreover, according to the research, there is a lack of regulatory and political preconditions to make the existing niche technology marketable on a large scale. A few days ago, German Economics Minister Robert Habeck (Greens) announced at an industry meeting that bi-directional vehicles and services could be commercially available from 2025.

“As mobile electricity storage devices, electric cars can make a huge contribution to stabilizing the electricity system,” Habeck said. “Their batteries can be used to temporarily store electrical energy, providing additional flexibility.”