Electric Cars as Part of the Energy Transition: Audi is Researching Bidirectional Charging Technology


Audi is the latest vehicle manufacturer to research bidirectional charging, in collaboration with the Hager Group. As the number of registered electric vehicles (EVs) rises, so too does the number of mobile energy-storage units. With this in mind, the joint research project seeks to create financial incentives for EV owners and offer greater security of electricity supply.

“The idea is as simple as it is genius: The high-voltage battery of the electric car not only is charged via the wall box at home but can also supply energy back to the house as a decentralized storage medium,” Audi says. “If the customer has a photovoltaic system, the electric car serves as a temporary storage medium for the domestically generated eco-electricity. When the sun is no longer shining, the vehicle can supply the stored electricity back to the house. Bidirectional charging at home—also known as Vehicle to Home (V2H)—has great potential to reduce the home owner’s electricity costs and increase network stability.”

In the test network, the electric model was operated with a DC wallbox that enables a charging capacity of up to 12 kW, as well as a flexibly expandable home storage unit with a capacity of 9 kWh. In the event of a possible series application, this might provide additional flexibility but is not a necessary prerequisite for bidirectional charging. Since both the home storage, the battery in the car, and the solar system operate on direct current, the CCS connection is used via the DC wallbox and no inverter is connected in between.

The electric car should store the surplus of the PV system not used by consumers in the house – of course only if the car is also in the garage during the day and connected to the wallbox. Later on, the car can supply electricity back to the house again. With the electric car battery as an additional energy storage device, the energy costs for the household should be able to decrease as well as the owner’s CO2 balance.

The developers made everyday usability a top priority. “Maintaining mobility is at the center of our attention. Customers, therefore, don’t need to restrict themselves in order to make bidirectional charging suitable for everyday use,” Dehm describes the focus of the development. “The intelligent charging management manages the optimum use of the battery, thereby maximizing the cost-effectiveness of the overall system. The system is very easy for customers to use – all they have to do is plug in the car, and the rest happens automatically.”

The joint research project with the Hager Group has proven two essential things: Customers who have their own PV system can design their mobility to be optimized in terms of cost and CO2 consumption while taking some of the burdens off the grid at the same time. As a positive side effect, customers who own an electric car from Audi can make an important contribution to the success of the energy transition. The intelligent use of the HV battery in the vehicle also opens up possibilities to use an existing resource that was previously used for mobility purposes alone in a sustainable way.

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