Technical Setup

Technical setup define the operational boundaries of a Battery Energy Storage System (BESS). They ensure that the dispatch and optimization models reflect realistic physical limitations rather than unconstrained, theoretical performance. Capturing these correctly is essential for producing credible forecasts of revenues and asset behavior.

Technical Parameters Interface
Figure: Interface for configuring BESS technical parameters

Power Limits

The power rating of a battery determines its maximum charging and discharging capability at any moment, typically expressed in MW. This rating is governed by inverter capacity, thermal design, and grid connection limits. In practice, this ensures that the BESS cannot instantly charge or discharge beyond its designed maximum power, even if energy is available.

Energy Constraints

Energy constraints govern the usable energy storage within the system:

  • Total capacity (MWh): Defines the energy reservoir available for shifting load or trading in markets.
  • State-of-Charge thresholds: Minimum and maximum limits (e.g., 10–90%) are applied to avoid full depletion or overcharging, which would accelerate degradation and void warranties.
  • Initial State-of-Charge (SoC): Sets the starting balance for dispatch simulations, often chosen to allow flexibility for both charging and discharging.
  • Round-trip efficiency: Real-world systems incur losses when charging and discharging. Typical lithium-ion batteries achieve ~85–92% efficiency overall, ensuring that modeled revenues account for these unavoidable losses.
  • Cycle limits: To safeguard asset life, daily cycling is capped at a realistic value (e.g., between 1–2 cycles per day depending on design and strategy).

Degradation

Battery degradation represents the gradual decline in usable capacity over time. It depends strongly on the number of cycles performed and the depth of discharge (DoD) applied in each cycle. Shallow cycling reduces wear, while frequent deep discharges accelerate it.

Battery Degradation with Cycles
Figure: Example degradation relationship between cycle depth and capacity fade

Typical patterns observed:

  • Shallow cycling (e.g., 20% DoD) extends lifetime, often allowing thousands of cycles before significant capacity fade.
  • Moderate cycling (e.g., 50% DoD) leads to noticeable degradation after several thousand cycles.
  • Deep cycling (e.g., 80% DoD) can result in much faster capacity loss, reducing lifetime to a fraction of shallow-cycle operation.

The Re-Twin dispatch model incorporates degradation to balance short-term revenue maximization against long-term asset value preservation. This ensures that financial projections are grounded in the physical aging of the battery, not just theoretical market opportunities.

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