By integrating electric vehicles into the domestic power grid to reduce electricity costs, increase grid stability and at the same time conserves the climate – Hager Group and AUDI AG pursue their vision as part of an innovative research project.

In the first half of 2020, the proportion of green electricity as a percentage of the total electricity mix in Germany exceeded 50 percent for the first time. As this proportion grows, however, the basic dilemma associated with these renewable energy sources remains: firstly, the problem that electricity cannot always be supplied when it is required and secondly, on sunny days and in high-wind conditions, there is often a lack of capacity for storing the energy generated. Hager Group has therefore joined forces with AUDI AG on a research project that could make an important contribution to resolving this dilemma: bidirectional charging at home, otherwise known as Vehicle to Home or V2H for short.

The idea is as simple as it is ingenious: the electric vehicle’s high-voltage battery is not only charged from the home electricity supply for use as an energy source for the vehicle, it can also be used as a decentralised storage medium for the home power grid.

According to Ulrich Reiner, e-mobility expert at Hager Group, “A vehicle battery can store about as much energy as an average household needs in a week”. The potential storage capacity is therefore considerable.

In the future, the new charging infrastructure will theoretically allow an electric vehicle’s high-voltage battery to be charged from any home connection and also to deliver energy back into the home power grid. Property owners who produce their own electricity from rooftop photovoltaic panels, for example, will be able to store it in their car and then return it to the home as required. The official name of this two-way charging process is Vehicle to Home (V2H).

 “V2H has major potential for reducing electricity costs of homeowners and increasing both grid stability and supply security in the event of a blackout,” explains Ulrich Reiner. “Using the battery of thousands of electric vehicles to make a significant contribution to climate protection is a vision that has fascinated us from the very beginning.”

A technically complex project

What sounds simple in theory is in practice extremely technically complex, requiring perfect coordination between the various technical components – hence the joint project between Hager Group and AUDI AG.

Hager Group, through its subsidiary E3/D3, an expert in photovoltaic home power stations, is contributing the technical know-how behind the charging infrastructure, which will use the battery of the vehicle prototype, based on the Audi e-tron, as an energy storage system for V2H. This is only the start, however. A bidirectional charging system that is suitable for everyday use requires much more: a smart home energy management system to manage the energy exchange with the vehicle when the sun is shining or when electricity is required in the home, for example, and of course a charging station. Hager Group was also able to offer suitable solutions from its product portfolio for this. Implementation of the CCS charging standard was supported by US partner company IoTecha.

Focus on suitability for everyday use

The developers placed great importance on suitability for everyday use. “Preserving mobility is our priority. Bidirectional charging should impose no limits on the customer,” explains Martin Dehm, technical project manager for bidirectional charging at AUDI AG.

“The intelligent charging management system controls the optimal use of the battery and thus maximizes the economic efficiency of the entire system. For the customer, operation is extremely simple - plug in the car and the rest happens automatically.”

Contributing to the success of the energy transition

Ulrich Reiner is confident of the project’s potential, “In the future, an increasing number of homeowners will have a car in the garage or outside the home that is able to store energy generated by the home’s own PV system”. By combining a PV system with a home power station and vehicle battery, homeowners will be able to manage self-sufficiently for days on end – while at the same time relieving strain on the electricity network. This will make an important contribution to the success of the energy transition.