Bidirectional charging: TransnetBW turns e-cars into charging boosters

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Bidirectional charging: TransnetBW turns e-cars into charging boosters-charging

In a two-year pilot project as part of the “Bidirectional Charging Management” (BDL) project, TransnetBW is investigating two use cases of V2G technology. Bidirectional charging means that an electric car can not only charge the vehicle battery with electricity from the electricity grid, but also feed electricity from the vehicle battery into the electricity grid.

Bidirectional charging of the e-car fleet optimized in this way ensures, for example, that increased energy requirements do not overload the grid connection. In this case, the electric cars serve as storage and thus for a short-term increase in performance in order to quickly supply specific other vehicles in the fleet with electricity. E-cars thus become charging boosters and relieve the grid connections.

In addition, by means of CO2-optimized charging, preference should be given to refueling with green electricity, thus reducing the CO2 footprint of vehicle fleets – not only in terms of balance, but also in absolute terms. Using a predicted CO2 index, the software charges the vehicles when the power plant park currently feeding into the grid has low emissions of CO2 equivalents.

With these two use cases, the project wants to make an important contribution to a successful energy transition and the achievement of climate goals.

A basis for many other applications

For the implementation, the transmission system operator uses special wall boxes from the manufacturer Kostal for bidirectional charging in connection with three correspondingly technically modified BMW i3. According to a current announcement, these will be integrated into the TransnetBW vehicle fleet without restrictions and used accordingly. Fraunhofer ISE is developing special optimization software and providing support in setting up the data infrastructure for targeted vehicle control.

The project at TransnetBW thus also forms the basis for further use cases in relation to grid flexibility, such as the provision of redispatch capacity or the support of the grid frequency through balancing power.

TransnetBW is involved as an associated partner in the three-year project funded by the Federal Ministry for Economic Affairs and Energy; The responsible body is the German Aerospace Center (DLR).

The project participants – including BMW, FfE, Kostal and the University of Passau – are testing a total of 14 use cases. Together they are pursuing the goal of developing a holistic, user-oriented offer for the integration of electric cars into the energy system in Germany. In addition to user-friendly technological solutions, this requires intelligent interaction between vehicles, charging infrastructure and power grids. In their position paper on the provision of system services from electric vehicles with bidirectional charging management, the consortium partners specifically consider the use cases of primary control reserve and congestion management.

Electric cars as smart electricity storage

As a pioneer in Germany, TransnetBW wants to integrate electric mobility into the intelligent power grid of the future and founded the Mobility4Grid competence center for this purpose in 2020. The goal: pooling the competencies of the various parties involved, such as network operators, vehicle manufacturers, research institutes and other innovators, and leveraging synergies. In several pilot projects, the transmission system operator is testing the possibilities of electromobility as smart electricity storage in network and system operation and is developing the tools for their use.

The aim of the “Bidirectional Charging Management – BDL” project is to develop and test a holistic, user-oriented offer for the integration of e-cars into the energy system in Germany. This is because regenerative electric vehicles can be used to support the grid by optimizing the absorption of energy from renewable sources into the public power grid and keeping it stable at the same time. Above all, this requires intelligent interaction between vehicles, charging infrastructure and power grids.

In addition to the consortium leader BMW Group, the partners Kostal Industrie Elektrik GmbH, TenneT, Bayernwerk Netz GmbH, KEO GmbH, FfE Munich, Karlsruhe Institute of Technology (KIT) and the University of Passau are involved. The project is funded by the Federal Ministry for Economic Affairs and Energy. Project sponsor is the German Aerospace Center (DLR).

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11 thoughts on “Bidirectional charging: TransnetBW turns e-cars into charging boosters”

  1. It is obvious that bidirectional charging has its charm for the network operator as the number of connections increases. But what about the vehicle owner? In order to apply this on a large scale, one could of course install something like a toleration obligation for vehicle owners. With appropriate lobbying, that would certainly be feasible. Wouldn’t be new territory for the big energy suppliers..

    But what if the owner wanted bi-directional charging because there was a guarantee that this would not damage the vehicle battery in any way and there were direct advantages (e.g.B. Bonus kWh, special DC rates…) would beckon? So classic win-win, where both sides benefit?

  2. However, the owner of the electric car must be paid handsomely so that he is willing to make valuable cycles of the expensive battery available to the grid.

  3. An example from Central Switzerland: Company x has solar cells on the roof, so employees can charge their cars during the day and pay less for it than for electricity from the grid. In the evening they drive home and use electricity from the battery at home in the house. Company x also finances solar cells on the roofs of the MA. Since electricity is cheaper than grid electricity, no one discusses compensation nonsense or my electricity is not your electricity or ridiculous win-wins. This is how the future works. And it works.

  4. Because of my already very good today, more than 10 years of experience with a lithium iron phosphate (LFP) battery, I would also want to buy a V2G-capable [future] e-car with this same technology in order to with a network-friendly bonus to be able to use!

  5. I don’t think the battery will be damaged if you supply a normal house with it. When driving, the battery is constantly discharged and recharged when braking. That doesn’t appeal to a fat battery at all. High currents and 100% or 0% SuC are critical.

  6. I’ve been reading about tests like this for years. It started with Nissan and Chademo. How often and how long do you have to test something like this before it finally becomes reality? In principle, this technique shouldn’t be that insanely difficult.
    Apparently it’s just a matter of issuing a press release that attracts the public every now and then.

  7. A simple implementation would be possible in the area of ​​home storage / balcony power plant. So only small power of about 500W. This is usually enough to supply the house. 12h without sun would only be 6kWh and therefore only 10% of a normal car battery. This would then also require no adjustments to the electricity meter.

  8. I’m sure that bidirectional charging and using the many e-cars standing around as a swarm battery will solve many of our electricity problems. I would immediately make 50% of my battery capacity available for it. It must:
    1. Provide a financial incentive between charging up electricity at night and making electricity available at peak times.
    2. Possibility to set the % of the available battery capacity. So normally 50%, if a longer journey is pending 0%

    I assume that battery technology will improve significantly over the next few years.

  9. The big electricity companies want no decentralized power supply or storage. You don’t make any money doing that. Therefore, for more than 10 years, only tests have been used and subsidies have been tapped for them.
    The solution could be so simple. Define a standard and let the market offer V2H products. Many e-car and PV owners would buy them. The rest then takes care of itself.
    But stop without the energy giants and without the state. And both are unthinkable in Germany 🙁

  10. The technology is simple and in direct current at every hybrid inverter with data interface (to. EEBUS) can be connected. This is just a matter of tapping into funding for a new study. It’s not about doing, unfortunately. We’ve seen this story for years.

  11. With bi-directional loading, all questions come up like here in the chat history. In the joint research project “Bidirectional Charging Management” (BDL) https://www.bdl project.en/
    we investigate all these questions and test the developed solutions with our pilot customers. Take a look at our project homepage from time to time, then you can look over our shoulder.


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