GERMANY. Corporate fleets to become power plants: Research project on bidirectional charging of vehicle fleets

Batteries for electric cars and their charging stations will become an important component of the energy transition: In the future, they will be able to take on the task of stabilizing the energy system in the short and medium term by feeding electricity back into the grid when the vehicles are not needed. Scientists at the Fraunhofer Institute for Solar Energy Systems ISE, together with consortium partners, are researching how this bidirectional charging with vehicle fleets can be implemented technically and economically by companies in the project “BiFlex Industry – Bidirectional Flexibility through Fleet Power Plants in and around Companies”.

Das BiFlex-Industrie-Projektteam beim Kick-Off-Meeting am Fraunhofer ISE.

In addition to stationary storage systems, vehicle batteries are predestined for balancing load and generation in the energy system in the short to medium term. Electric vehicles have batteries with high electrical output, large storage capacities and usually have a long service life. In company fleets, they can buffer locally generated photovoltaic electricity and actively reduce load peaks. Thanks to the possibility of feed-back, the flexibility can also be made available to the higher-level power grid – as a so-called fleet power plant. Employees' vehicles can also be integrated into this concept.

In the project “BiFlex Industry – Bidirectional Flexibility through Fleet Power Plants in and around Companies”, a consortium of research, industry and users is working on solving the remaining challenges. The aim of the project is to holistically exploit the potential of regenerative vehicle fleets. Concrete advantages for companies and energy business models are to be worked out and demonstrated so that they can be integrated into existing systems on a large scale and become the nucleus for fleet power plants – for optimising the operation of the company and the higher-level power system.

Initially, the project will focus on company locations with company and employee vehicles. Demonstrators with 50 regenerative vehicles are planned at seven company locations, where various relevant use cases for bidirectional charging will be implemented. To this end, the partners will initially develop and commission regenerative charging stations, including adapted hardware and open communication interfaces to higher-level control systems and electric vehicles. You will develop concepts and procedures for determining and forecasting flexibility potentials through regenerative energy during operation. At the same time, the project partners are working on standardisation and the formulation of success factors for the transferability of project results.

The Fraunhofer Institute for Solar Energy Systems ISE in Freiburg is leading the project and is researching in particular the standardized system integration of the charging infrastructure. “With new approaches and our research work, the mobility infrastructure will not become a burden, but an important pillar of the energy transition that will bring efficiency, flexibility and stability to the energy system,” explains Dr. Robert Kohrs, head of the Intelligent Grids department at Fraunhofer ISE. “The practicability of the results to be developed in the project is ensured by the close cooperation of manufacturers, users, the energy industry and the support of applied research,” Kohrs continues. Fraunhofer ISE is involved in all work packages with four teams and will also expand its own fleet to include the aspect of regenerative capability. The institute's Digital Grid Lab will play a central role in this, where the digitalization of grid operations management can be developed and tested in a hardware-in-the-loop environment. Other focal points at Fraunhofer ISE are the investigation of flexibility potentials through market-based incentives such as dynamic charging tariffs and the integration of electric vehicles into fleet power plants through intelligent operations management algorithms that ensure a supply to the company's site in the event of a grid failure.

The project is funded with 14.9 million euros by the German Federal Ministry for Economic Affairs and Climate Action (BMWK), FKZ: MV23020.


Fraunhofer Institute for Solar Energy Systems ISE (consortium leader)

Ambibox GmbH

Chargebyte GmbH

German Commission for Electrical, Electronic and Information Technologies in DIN and VDE

ENIT Energy IT Systems GmbH

Fraunhofer Institute for Industrial Engineering IAO

Fraunhofer Institute of Optronics, System Technologies and Image Exploitation IOSB-AST

Karlsruhe University of Applied Sciences, University of Applied Sciences


MAHLE chargeBIG GmbH

Marquardt Group

Physikalisch-Technische Bundesanstalt, PTB


SMART/LAB Innovationsgesellschaft mbH

Thüga Aktiengesellschaft

Universität Duisburg-Essen