The incorporation of the electric car into the domestic power grid is at the core of an innovative research project on bidirectional charging that Audi
and the Hager Group
This technology offers major advantages in combination with a photo-voltaic (PV) system in particular, with excess PV electricity being stored temporarily and output as needed.
In the first half of 2020, renewable energies contributed more than 50% to the German electricity mix for the first time. However, the increasing percentage is also accompanied by a basic dilemma of wind and solar power — that the generation of electricity 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.
However, as the number of registered electric cars increases, so the number of ‘mobile energy storage units’ also increases, which is why Audi and the Hager Group are working on bi-directional charging.
Martin Dehm, technical project manager for bidirectional charging at Audi, said: “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.”
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.
The technology 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 supply costs, the electric car can supply the entire house at times when electricity prices are high. At night, the car uses low-rate electricity to charge up to the desired target SOC (state of charge).
Mr Dehm added: “The intelligent charging system manages the optimum use of the battery, thereby maximising the cost-effectiveness of the overall system, which has been designed to be very easy for customers to use — all they have to do is plug in the car, and the rest happens automatically.”