German Dispatch Model

Optimizing battery dispatch across German markets

For an overview of available revenue streams and market structures, see the Revenue Stack page.

Illustrative 15-min Dispatch

The model optimizes battery operations at 15-minute granularity, co-optimizing across energy and ancillary service markets:

Multi-market Optimization

The dispatch model solves across multiple market stages:

1. Day-ahead step – contracts volume in day-ahead, FCR, and aFRR capacity markets with perfect foresight
2. Intraday step – sequential optimization with 2-hour rolling horizon, honoring day-ahead commitments
3. Real-time step – sequential optimization with imperfect foresight for real-time and aFRR energy activation

Capacity is reserved at day-ahead for intraday opportunites.

Market rules are respected: symmetric provision of FCR charge and discharge is required, and the maximum FCR capacity is limited to 80% of the maximum power of the asset.

Intraday Market Saturation

The intraday markets represent a large revenue stream in Germany, with the highest traded volumes in Europe.

• Intraday traded volume grows over time as more storage, renewables, and non-physical traders enter the market
• More liquidity means more competition and fewer extreme price events
• Intraday trading opportunities become less valuable for each individual battery

The model accounts for this saturation effect with diminishing returns as battery penetration grows.

aFRR Energy Activation

The model accounts for expected energy activation in aFRR.

• It uses historical activation probabilities by time of day and direction
• Energy payments are based on these activation probabilities, and energy price
• Impact on battery state of charge is included in the optimization, as well as throughput into cycling constraints.

Data Sources for Ancillary Service Modelling

The frequency response inputs to the model come from published German market data:

The historical activation data is used to build the activation probabilities described above, so that modelled aFRR energy revenues reflect how often batteries are actually called on in practice.

Inertia (Momentanreserve) revenue is modelled as a ten-year contracted stream

Inertia is treated as a contracted, exogenous revenue stream rather than a co-optimized market product. Eligible assets receive a flat ten-year contract payment over the contract horizon, scaled by an assumed availability factor.

• Price source: the German TSO Momentanreserve published prices for 2 to 10-year contracts starting in the 2026-27 period
• Contract horizon used in the model: ten years, the upper end of the published 2 to 10-year contract range
• Availability assumption: 95%, derived from operational unavailability data observed in Great Britain (no equivalent German dataset is currently available)
• Qualifying capability: only the inverter’s overload capability — the megawatts that can be delivered above rated power for a few seconds — is monetized in inertia; no headroom is taken from the rated power of the asset
• No co-optimization: inertia revenue does not compete with day-ahead, FCR, aFRR, or intraday in the dispatch decision, because the volume is committed to the long-term contract

Fields and behaviour

To enable inertia revenue in a forecast run, two settings on the Battery tab of the forecast creation flow must be configured together:

If the grid-forming inverter toggle is off, no inertia revenue is modelled regardless of the Inverter Overload Capacity value.

Worked example

A grid-forming inverter that can deliver 130% of its rated power for a few seconds has a 30% Inverter Overload Capacity. With the grid-forming inverter toggle on and 30 entered into the field on an asset with 100 MW rated power, 30 MW of inertia capability is qualified for the ten-year contract. The reported inertia revenue covers those 30 MW across the full ten-year contract horizon, scaled by the 95% availability assumption.

Ancillary service capacity is capped by a single combined limit

The Maximum ancillary services capacity field on the Grid connection tab limits how much of the asset can be committed to ancillary services. It is entered as a percentage of nameplate power and is sometimes referred to as the ancillary services restriction.

The limit applies to the combined capacity across all ancillary service products, not to each product individually. In any period, the total capacity the battery commits across FCR, aFRR, and any other ancillary product cannot exceed the entered percentage of rated power. It is not a separate ceiling for each product.

The cap is applied to each direction independently:

• Discharge direction: the sum of all upward (discharge) ancillary capacity is capped at the entered percentage of rated power.
• Charge direction: the sum of all downward (charge) ancillary capacity is capped at the entered percentage of rated power.

The percentage is the maximum share available for ancillary services, not the share removed. A value of 75% means up to 75% of rated power can be committed to ancillary services combined; it does not mean participation is restricted to 25%.

This limit is distinct from two other constraints the model always applies:

• FCR symmetric cap: the maximum FCR capacity is separately limited to 80% of rated power, with symmetric charge and discharge provision required. This applies regardless of the ancillary services capacity setting.
• Per-market limits: individual markets can be capped or disabled independently, which is a finer-grained control than this single combined ceiling.

Fields and behaviour

Worked example

A 100 MW battery with Maximum ancillary services capacity set to 75% can commit at most 75 MW to ancillary services in the discharge direction and at most 75 MW in the charge direction. If it holds 50 MW of aFRR up, no more than 25 MW of any other upward ancillary product (such as FCR) can be added on top in that direction. The remaining rated power stays available for wholesale energy dispatch.

Flexible Connection Agreements

The model supports Flexible Connection Agreements, which impose operational constraints on grid-connected assets including ramping rate restrictions, export/import limits, and ancillary service participation constraints.

See the dedicated Flexible Connection Agreements page for detailed documentation on how they impact battery operations and dispatch optimization.