German Dispatch Model

How the model optimizes 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

Footroom Reservation

For the day-ahead step, the model implements footroom reservation to preserve capacity for intraday opportunities:

  • Footroom: Battery’s capacity to discharge, calculated as:
\[F_t = \frac{\text{SoC}_t - \text{SoC}_{\min}}{\Delta t}\]
  • Reserves capacity for potential high-price periods in later markets
  • Constrained by available state of charge:
\[F^{\text{reserved}}_t \leq \frac{\text{SoC}_t - \text{SoC}_{\min}}{\Delta t}\]
  • Constrained by available power:
\[F^{\text{reserved}}_t \leq P^{\max} - P^{\text{discharge}}_t\]
  • Limited by daily cycling limits:
\[\sum_t F^{\text{reserved}}_t \cdot \Delta t \leq E^{\max} \cdot N_{\text{cycles/day}}\]
  • Revenue calculation:
\[R_{\text{footroom}} = \sum_t \left( \pi^{\text{intraday}}_t \cdot F^{\text{reserved}}_t - \lambda_{\text{risk}} \cdot F^{\text{reserved}}_t \right) \Delta t\]

Symmetric FCR Provision

For FCR services, the model enforces symmetric provision:

  • Equal capacity must be reserved in both charging and discharging directions
  • Implemented as a constraint:
\[P^{\text{FCR}}_{\text{charge}} = P^{\text{FCR}}_{\text{discharge}}\]
  • Applies a derating factor of 0.8 to account for the symmetric requirement
  • Maximum FCR capacity limited to:
\[P^{\text{FCR}}_{\max} = P^{\max} \cdot 0.8\]

Intraday Market Saturation

The model accounts for intraday market saturation effects as battery penetration grows:

\[M = \min\left(1, \left(\frac{\rho_{\text{BESS/RES}}^{\text{base}}}{\rho_{\text{BESS/RES}}^{t}}\right)^\beta\right)\]
  • Where \(\beta\) is 0.5, replicating the empirical square root law in finance
  • Where RES is total Renewable Energy Generation, which is directly proportional to balancing needs
  • Adjusts intraday revenue down because average prices get impacted as trade sizes become larger (more competition from flexible technologies)
  • Reflects diminishing returns as more batteries participate in the market

aFRR Energy Activation

The model accounts for expected energy activation in aFRR:

  • Uses historical activation probabilities by time of day and direction
  • Energy payments calculated based on activation probability and energy price
  • Impact on battery state of charge included in the optimization
  • Throughput calculated as:
\[E^{\text{aFRR}}_t = P^{\text{aFRR}}_t \cdot p_{\text{activation},t} \cdot \Delta t_{\text{activation}}\]

Flexible Connection Agreements (FCA)

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 FCAs impact battery operations and dispatch optimization.