»C/sells« Evaluation of a cellular energy system

An important result of the energy transition is the decentralization of electricity production. It is a great challenge to design a decentral, intelligent energy system (smart grid) as robust and efficient as central networks with powerful large power plants. In the project »C/sells« scientists from Fraunhofer ISI, together with 60 partners, investigate how decentral energy systems, made up of many small energy sources can work reliably and efficiently. Fraunhofer ISI helps to shape the project’s guiding principles and, among other things, evaluates the developed solutions.


The project C/sells is based on the vision that in future a large number of power plants produce electricity from different renewable sources which is fed into a common grid. In order to design a reliable energy system for the whole of Germany from the interaction of many local renewable energy sources, C/sells is planning to connect the individual plants in cells with each other.

Such a decentral, cellular energy system is currently tested in Southern Germany. In a model region the interaction of decentral electricity production and consumption is tested in 35 demonstration cells. The cell is the central building block of this energy system. One cell can comprise one or several units which generate, consume or store electricity. The individual systems within one cell as well as the cells themselves are interconnected.

Cellularity as a central building block of the energy system

Cells can be of a geographical nature such as the quarter Franklin in Mannheim, but also individual objects like the airport Stuttgart. A decentrally controlled inexpensive energy system is to be developed by exchanging data and energy within the cells as well as between the cells themselves.

On the one hand the scientists are evaluating the solutions in order to better coordinate consumption, production and grid load inside and outside of the cells. On the other hand they are investigating the willingness of the public, enterprises and organizations to actively participate in a cellular energy system.

The energy system of the future: participative, varied and cellular

Fraunhofer ISI designs important parts of C/sells, including the guiding principles, which describe in what way the energy transition is implemented in C/sells. Apart from the property cellularity the guiding principle describes two more properties of such an energy system. First, participation: C/sells wants to motivate the public and enterprises to realize the energy transition themselves, for example by selling self-generated electricity on the market or by adapting their own consumption to the availability of renewable energies. Here also innovative solutions are tested such as for example blockchain technology which makes direct transactions without an intermediary possible. Connected to this is also the hope that members of the public who are actively participating in the energy system are supporting the energy system as a whole and shape it. In as much and under which conditions this is successful is one of the questions in the project. Second, diversity: C/sells unites a large number of actors, technical solutions and needs. Not only the cells and the systems also the project structure and organization of C/sells are highly interconnected. The sum of the individual solutions creates a big, working whole.

Fraunhofer ISI is responsible for evaluating the results of C/sells. The team develops a quantitative and qualitative evaluation instrument in order to assess the concepts developed within C/sells. Not only different technical solutions can be evaluated but also business models and incentives which for example are to guarantee that the electricity trade in which owners of private energy facilities participate is rule consistent.


2017 bis 2020


Bundesministerium für Wirtschaft und Technologie (BMWi)


  • Fraunhofer ISE Freiburg
  • Institut für Energiewirtschaft und Rationelle Energieanwendung (IER) Stuttgart
  • Institut für Nachhaltige Technische Systeme (INATECH) der Universität Freiburg
  • Öko-Institut e.V.
  • Forschungsstelle für Energiewirtschaft (FFE)
  • Deutsches Zentrum für Luft- und Raumfahrt (DLR)

and other


See ISI-Publica, search keyword "c/sells"