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R&D project develops bidirectional charging management for e-cars

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By Christoph Hammerschmidt


In the recently launched research project “Bidirectional charge management – BDL”, companies and institutions from the automotive, energy and scientific sectors are jointly developing technological solutions with which electric mobility can become more comfortable for users, cheaper and with lower emissions. The aim of the interdisciplinary project partners is to link vehicles, charging infrastructure and power grids with each other in a holistic approach in such a way that the most comprehensive possible use of regeneratively generated energy is promoted and at the same time the security of supply is increased.

The bi-directional charging capability enables electric vehicles, when connected to a charging station or wallbox designed for this purpose, not only to take up electrical energy for the high-voltage battery, but also to feed it back into the power grid in the opposite direction. The batteries of the electric vehicles thus become mobile energy storage units that can also supply electricity if required. Such an integration of electric vehicles into the power grid requires a series of innovations in the areas of vehicle technology, charging hardware, charging management and communication interfaces to energy industry stakeholders as well as with regard to legal framework conditions. These are created as part of the research project in which, in addition to the consortium leader, the BMW Group, Kostal Industrie Elektrik GmbH (development of charging hardware), the transmission grid operator TenneT and the Karlsruhe Institute of Technology (KIT; research on electricity market and grid repercussions) are also involved.


According to the research consortium, the increasing number of electric vehicles on the road will require a small increase in the amount of electrical energy required. However, there is a growing need to control energy flows intelligently in order to make optimum use of electricity from renewable sources.

BMW is contributing its experience with similar projects in California to the research project. Building on this, BMW has developed an innovative solution for use in the German energy grid in cooperation with the grid operator TenneT, with which the charging strategy of electric vehicles takes into account not only the mobility plans of the customers but also the availability of green electricity and the utilisation of the electricity grid. In response to signals from the grid operator, connected vehicles can interrupt the charging process and continue it at a later point in time. Now the project partners want to go one step further and achieve stronger control effects: Parked electric vehicles connected to a charging station or wallbox can thus be used as flexible power storage devices. In phases of particularly high demand for electrical energy, they feed additional electricity into the grid.

In contrast, their high-voltage batteries are charged primarily at times when the general energy requirement is lower. This means that electricity from renewable energy sources can be absorbed and stored exactly when it is available. And the stored energy can be used exactly when it is needed – for electric driving or to support the electricity networks. In the view of the project consortium, electromobility can help to stabilise the electricity grid, reduce the need to expand the grid and keep electricity prices stable.

At the same time, the intelligently controlled integration of e-vehicles into the power grid can further increase the share of renewable energy in total consumption. By using the storage capacities provided in the vehicle batteries, supply and demand in the area of green electricity can be better coordinated. This creates an energy buffer for wind and solar power plants.


If, for example, there is a temporarily oversupply of solar power, it can be stored in the batteries of the electric vehicles and later used to drive or feed it back into the customer’s building at home (“vehicle to home”) or into the power grid (“vehicle to grid”) in order to cover sudden bottlenecks even without the additional use of fossil fuels in power plants.

As part of the “Bidirectional charging management – BDL” research project, technologies for energy management systems as well as hardware and software for controlling charging processes are being developed in addition to regenerative systems for vehicles and wall boxes. In addition, legal and regulatory framework conditions will be evaluated. The practical phase of the project will begin in 2021. During a one-year pilot phase, 50 private and fleet customers will be equipped with BMW i3 regenerative power supplies, suitable charging hardware and associated digital services in order to test the customer benefits and user-friendliness of the solutions developed to date under real conditions. The aim is to create a basis for the later widespread use of the technology to integrate electromobility into the power grid.

The research project under the auspices of the German Aerospace Center (DLR) is funded by the German Federal Ministry of Economics and Energy and is scheduled to run for three years.

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