Germany is in the midst of implementing the energy transition; by 2030, at least 80% of our electricity consumption is to be covered from renewable energy – primarily from wind and solar power. Germany’s electricity system has to be largely climate neutral by around 2035 so that all remaining sectors can be climate neutral by 2045 – this is shown by scenarios from the International Energy Agency. This conversion will fundamentally change the supply of electricity in Germany. In future, there will be more and more hours in which 100% of electricity demand is covered by renewable energy.

This change in the generation structure also affects the operation of the system. Unlike conventional power stations, renewable energy installations tend to be connected to the distribution grid via inverters. This results in different requirements, but also new ways to ensure secure and robust grid operation.

Ancillary services, such as the regulation of the frequency and the voltage level of alternating current, play a key role in ensuring a secure operation of the electricity grid and maintaining system stability. For example, the synchronous generators of conventional power stations also provide an inertial reserve in addition to the generated power, and this has a stabilising effect on frequency changes in the electricity system. This means that in future, as conventional power stations come off the grid, their stabilising characteristics must be delivered in an alternative way. Renewable electricity generation installations and other installations, such as storage facilities and charging devices for electric mobility or installations of the grid operators will have to be developed further for this so that they can take over these tasks.

In general, this systemic change will entail fresh challenges for grid operators and market participants, and a need for further development for grid operation concepts and technical specifications of installations.

Against this background, the 2021 coalition agreement stipulated the drafting of a System Stability Roadmap, with this work to be led by the Federal Minister for Economic Affairs and Climate Action.

The System Stability Roadmap is a central component for the restructuring of the electricity system in the context of the energy transition. For the first time, it presents in a structured way the further developments which are needed to maintain system stability.

The System Stability Roadmap was drawn up in the period from autumn 2022 until the end of 2023; the broadbased participation process with the active involvement of the sectors was led by the Federal Ministry for Economic Affairs and Climate Action. In four thematic working groups with 11 sub-groups, and accompanied by an advisory board, the System Stability Roadmap was compiled on the basis of more than 70 meetings. In total more than 150 people from more than 80 institutions were involved, including representatives of transmission and distribution systems, equipment manufacturers, associations, standardisation bodies and academia. The process was coordinated by a project steering group consisting of the Federal Ministry for Economic Affairs and Climate Action, the Bundesnetzagentur (Federal Network Agency), ef.Ruhr GmbH and dena (German Energy Agency).

The core task for the roadmap was the question: WHO has to do WHAT by WHEN, i.e. to show at process level:

1. what steps need to be taken for a stable operation of the electricity grid with 100% renewable energy,
2. when these steps will be taken, and
3. which stakeholders are to coordinate the processes.

As a basis for the drafting of the roadmap, a shared target vision with the functionalities of the future electricity supply system was developed with the relevant stakeholders. This target vision was then used to describe the challenges of stable and robust system operation with 100% renewable energy. Processes were derived from this which need to be adapted or redesigned in order to achieve the target system. The processes were derived on the basis of the substantive work of the four working groups. Overarching processes were identified; all the processes were placed in a timeframe, and cross-relations between the various processes were identified.

The heart of the System Stability Roadmap is the “Milestone Plan”, which delivers a specific transformation path towards secure and robust system operation with 100% renewable energy.

The System Stability Roadmap was adopted by the Federal Government in December 2023. An English translation is available here (PDF, 5 MB).

As background information, thematic papers from the working groups are available as a download (in German) in addition to the System Stability Roadmap. They show the status of the discussions in the working groups.

The special added value of the System Stability Roadmap is that it shows for the first time a specific roadmap to attain secure and robust operation of the electricity system with 100% renewable energy. This comprises:

1. the identification of the necessary processes (What?)
2. the stipulation of the starting times and implementation periods for these processes (When?) and
3. the identification of the process coordinators (Who?).

Basically, one can say that the System Stability Roadmap provides a roadmap to saying “WHAT WHO WHEN”.

In the System Stability Roadmap, a total of 51 processes are identified, and 18 central milestones stipulated up to 2030. The following illustration shows the central milestones. The specific processes and the central milestones are explained in detail in the System Stability Roadmap.

The central milestones can be consolidated in three paths:

• First path - defining the level of system security and determining the system demand: It is necessary to ascertain which areas of the electricity system already have defined security levels. In parts of the system where no such level has been defined, this must now take place. Building on this security level, “design-relevant cases” can then be defined. Design- relevant cases describe predictable and unpredictable events which may confront the system and which must be managed. The design-relevant cases defined make it possible to quantify the demand for the various ancillary services.
  
  
• Second path – covering the system demands: The second path is the coverage and structured procurement of system demands. To this end, suitable procurement measures must be introduced and implemented. In principle, there are three “pillars” for the procurement of ancillary services, which can also be pursued in parallel:
  Pillar 1: Ancillary services due to mandatory technical requirements to be met by the installations (Technical Connection Rules)
  Pillar 2: Voluntary paid provision of ancillary services by market players (market-based procurement)
  Pillar 3: Ancillary services from grid assets of the grid operators
  
  
• Third path – establishing grid-forming inverters: Grid-forming inverters are a key technology for maintaining system stability in the target system with 100% renewable energy. Installations with grid-forming inverters can actively provide a voltage for the electricity grid and inertia to stabilise frequency fluctuations (inertial reserve). This is a relatively new technology. It is therefore necessary to gather experience for a nation-wide rollout. This can take place in the context of research and pilot projects and of market-based procurement. On the basis of this experience, technical requirements for installations and the grid-forming inverters used in them can be defined or refined.

The compilation of the System Stability Roadmap under the leadership of the Federal Ministry for Economic Affairs and Climate Action with support from ef.Ruhr GmbH and dena was only possible due to the constructive and proactive involvement of many stakeholders in the various sectors. These include transmission and distribution system operators, equipment manufacturers, business associations, standardisation bodies and representatives of academia. It is only thanks to this stakeholder diversity and their hard work in the working groups and the advisory board that it was possible to draw up the System Stability Roadmap in this comprehensive form.

A total of 51 processes were identified in the context of the System Stability Roadmap. These now need to be initiated or adapted and implemented by the various stakeholders. Almost all the processes entail the involvement of several stakeholders, all of whom need to assume responsibility for parts of the process. Also, the processes are interdependent. The implementation of the System Stability Roadmap must therefore, as it was when it was drawn up, be actively and constructively supported by all the stakeholders. The overarching goal of a climate-neutral electricity system can only be achieved through good cooperation.

The Federal Ministry for Economic Affairs and Climate Action and the Bundesnetzagentur will continue to actively support the successful implementation of the Roadmap. For example, a System Stability Forum is envisaged for this. This will be a regular dialogue platform for the stakeholders responsible for implementation of the various Roadmap processes. The System Stability Forum is also to be used to monitor the implementation of the measures and processes of the System Stability Roadmap. One starting point here is the central milestones identified in the Roadmap. They are the key points of the transformation in the field of system stability and can therefore serve as points of reference for progress on the implementation.

Alongside the system operation and the maintenance of system stability, if the energy transition is to be a success it is also necessary to address the transformation of energy generation and consumption and the expansion of infrastructure for a climate-neutral energy system. The System Development Strategy (SES) provides an overarching framework for these processes. The System Development Strategy can thus provide a point of reference for follow-up processes, e.g. the Network Development Plans for electricity and gas/hydrogen.

The host of issues relating to ensuring system stability in an electricity system with 100% renewable energy is comprehensively addressed in a structured way for the first time in the System Stability Roadmap. This will ensure that system stability criteria do not impede the energy transition. The System Stability Roadmap and the System Development Strategy thus form additional pillars in the transformation of the energy system. Further information about the SES can be found at https://preview-bmwk.bmwk.de/Redaktion/EN/Dossier/energy-transition.html.