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Audi is carrying out a research project with electric vehicles and bidirectional charging with the aim of increasing network stability, lowering electricity costs and contributing to climate protection.
This offers major advantages in combination with a photovoltaic system in particular as excess PV electricity can be stored temporarily and output as needed.
In the first half of 2020, renewable energies contributed more than 50 percent to the German electricity mix for the first time. However, the generation of electricity by wind and solar power is not always constant. On sunny days and periods with strong winds, there is often a lack of capacity to store the generated energy that the grid cannot use.
As the number of electric cars increases, the number of mobile energy storage units also rises. This offers great potential, provided that the storage capacity can be used intelligently. Audi and the Hager Group have developed bidirectional charging that creates financial incentives and offers greater security of supply.
“Electric mobility is bringing the automotive industry and the energy sector closer together. The battery of an Audi e-tron could supply a single-family home with energy for around one week independently. Looking ahead, we want to make this potential accessible and make the electric car part of the energy transition as an energy storage device on four wheels,” says Martin Dehm, technical project manager for bidirectional charging at Audi.
The high-voltage battery of the electric car is not only charged via the wall box at home, but it can also supply energy back to the house as a decentralised storage medium. If the customer has a photovoltaic system, the electric car serves as temporary storage for the domestically generated 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.
It’s also possible to achieve near complete energy independence and increased security of supply in the event of a blackout.
What sounds simple in theory requires a high level of technical intelligence and coordinated interaction between different technical components in terms of infrastructure and in the vehicle. An Audi e-tron was used in the research project.
In the test grid, the fully electric Audi model operated with a DC wall box, which enables a charging capacity of up to 12 kW, and a flexibly extendable home storage unit with a capacity of 9 kWh.
Thanks to the DC voltage level in the overall grid, the connection between the PV system and the vehicle does not require an inverter.
Bidirectional charging focuses mainly on use cases where home owners use their own photovoltaic system to benefit from cost-optimised charging with their domestically generated electricity. The electric car stores the excess electricity from the PV system that is not used by appliances in the house. If the customer has variable rates, the electric car can supply the entire house in phases where electricity prices are high. At night or during non-productive times of the rate, the car then uses inexpensive electricity to charge.
In the event of a blackout, the system can supply the house with energy via the battery or it can even operate a building without a grid connection independently.
The joint research project with the Hager Group has proven two things: Customers who have their own PV system can design their mobility to be optimised in terms of cost and CO2 consumption while taking some of the burden off the grid at the same time.
Audi has committed to the objectives of the Paris Climate Agreement and is working on making its vehicle fleet CO2-neutral by 2050. In order to achieve this aim, the brand is pursuing a broad electric offensive that involves launching around 20 fully electric models by 2025.
