
Audi, Hager team for bidirectional charging
The number of mobile energy storage units is increasing with the rising number of electric car registrations. A great potential – if the storage capacity is made intelligently usable. For this reason, Audi and the Hager Group have jointly developed a solution approach that creates financial incentives and offers increased security of supply: bidirectional charging. “The battery of an Audi e-tron could supply a single-family home with energy for around a week on its own. In the future, we would like to exploit this potential and make the e-car part of the energy turnaround as a power storage device on four wheels,” says Martin Dehm, technical project manager for bi-directional charging at Audi.
The electric car’s high-voltage battery can be used as a decentralized storage medium to deliver energy to the home. If the customer operates a private photovoltaic system on the roof of his house, the electric car serves as a temporary storage facility for the green electricity he generates himself. If the sun is not shining, the vehicle can then release the stored electricity back to the house. Bidirectional charging at home – also known as Vehicle to Home (V2H) – has great potential to reduce the homeowner’s electricity costs and increase grid stability. As a further expansion stage, almost complete energy self-sufficiency and increased supply security in the event of a blackout is possible in combination with a home storage system.
In practice, however, this requires a high level of technical intelligence and the coordinated interaction of various technical components, both on the infrastructure side and in the vehicle. An Audi e-tron with near-series charging technology was used in the research project. In the test network, the all-electric Audi model operated with a DC wallbox, which enables a charging capacity of up to 12 kW, and a flexibly expandable home storage unit with a capacity of 9 kWh. In the event of possible series production use, this could provide additional flexibility, but is not a necessary prerequisite for bidirectional charging. Thanks to the DC voltage level in the overall system, the connection between the PV system and the vehicle does not require an inverter.
With bidirectional charging, the focus is primarily on use cases in which homeowners charge their own generated electricity with their own photovoltaic system in a cost-effective manner. At night, when electricity is cheap, the car is then charged again with cheap electricity until the desired target SOC (State of Charge) is reached.
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