Grid Integration of Large-Scale Battery Storage Systems – Flexible Connection Agreements (FCAs), Grid Tariffs, and More
Example
You can read this year’s Elia Viewpoint Study here:
LINK TO THE STUDY
Background
By the end of 2025, grid operators had already received grid connection requests for large-scale battery storage systems amounting to 720GW [1]. Storage systems are set to play a key role in the future of electricity systems. However, due to Germany’s uniform electricity price zoning system, their use does not take the grid situation into account. As a result, storage systems risk overloading the grid or exacerbating congestion. 2024 saw the costs of congestion management measures (Redispatch) amount to approximately €3 billion [2].
In an analysis conducted for the Elia Group, the FfE examined the following questions:
- What impact do large-scale battery storage facilities in different locations across Germany have on redispatch requirements?
- How do different measures aimed at integrating storage systems into the grid affect storage operations and redispatch requirements?
This study served as input for the annual Elia Viewpoint Studie.
Methodology
The FfE compiled a shortlist of potential instruments for the integration of storage systems into the power grid and allocated them to various categories. From this list, five instruments were evaluated qualitatively in terms of their efficiency, effectiveness, regulatory compatibility (with Germany and Belgium), complexity of implementation, as well as their potential risks and trade-offs.
Two of those measures – the dynamic grid tariffs and the flexible connection agreements (FCAs) with capacity restrictions – were also analysed from a quantitative perspective for the year 2024. Using the FfE’s e-Flame model, their impact on redispatch requirements in three German regions at the transmission system operator (TSO) level, as well as on storage operators’ revenues, was evaluated.
Results
Redispatch-increasing and redispatch-decreasing storage patterns virtually cancel each other out. Depending on the location, storage facilities may coincidentally result in a marginal increase or decrease in redispatch effect.
The two examined measures – the dynamic safeguards and dynamic grid tariffs – reduce the net redispatch requirement in all studied regions (see Fig.1). The dynamic safeguard completely eliminates redispatch-increasing behavior and becomes predictable for grid operators. However, it also reduces part of the random redispatch-reducing behavior, resulting in a smaller net effect. Dynamic grid tariffs internalise redispatch costs for storage operators, allowing them to make their own decisions regarding their operational mode. They have a greater impact on net redispatch demand.
However, these measures not only change redispatch costs but also impact the revenues of storage operators as well as grid operators’ revenues through dynamic grid tariffs.
Figure 2 illustrates the effects of the measures on net redispatch savings (positive value = cost reduction) as well as on storage revenues. As dynamic safeguards severely limit storage facilities’ marketing opportunities, they lead to a decline in revenues ranging from 8% to 17%. Dynamic grid tariffs often improve storage facilities’ revenues, as they take advantage of periods of negative grid tariffs.
The effectiveness of these instruments depends to a large extent on their specific configuration. Our qualitative analysis underlines the general trade-off between instruments that offer grid operators greater reliability and those more restrictive for market-oriented BESS operation. A balanced approach – combining multiple tools – can help mitigate these trade-offs and balance out the different implementation timelines. While some instruments can be implemented immediately, others require regulatory changes or significant implementation efforts. Some tools can be deployed immediately, while others will require regulatory changes or significant implementation efforts.
More information
- eFlame – electric Flexibility assessment modeling environment
- This year’s Elia Viewpoint Study will be presented at an invite-only event: Elia Group Viewpoint-Studie “Storage for System Strength”
- https://elia.group/storageforsystemstrength
Literatur
[1] BDEW, „Netzanschlussboom bei Großbatteriespeichern erfordert schnell neue Regeln,“ https://www.bdew.de/presse/netzanschlussboom-bei-gro%C3%9Fbatteriespeichern-erfordert-schnell-neue-regeln/#:~:text=Angesichts%20des%20Netzanschlussbooms%20bei%20Gro%C3%9Fbatteriespeichern,von%2078%20GW%20bereits%20%C3%BCberschritten., 27 11 2025.
[2] Energiewirtschaftliches Institut an der Universität zu Köln (ewi) und BET Consulting, „Energiewende. Effizient. Machen. Monitoringbericht zum Start der 21. Legislaturperiode,“ BMWE, https://www.bundeswirtschaftsministerium.de/Redaktion/DE/Publikationen/Energie/energiewende-effizient-machen.pdf?__blob=publicationFile&v=24, 2025.
