How it works
Dispatch starts with a forecast of the blocks ahead: generation from each asset, prices in each market, and any load to serve. An optimiser then picks the actions that maximise revenue or minimise cost within the plant's limits. Those limits include the export cap at the connection, the battery's power rating and SoC band, ramp rates, contracted schedules and any grid instructions. The result is a set of setpoints in MW, one per asset per block.
Dispatch runs at several timescales. The day-ahead plan sets bids and the declared schedule. Intraday, the plan is re-run as forecasts update. In real time, the plant controller follows the latest setpoints and corrects for what the meters show, every few seconds. The grid operator can override any of it with curtailment or a dispatch instruction. Afterwards, actual results are compared with what a perfect-foresight plan would have earned, which measures how much of the available value the strategy captured.
Why it matters
A project's financial model assumes a dispatch strategy, often an idealised one. The plant earns only what the real strategy captures, with imperfect forecasts and real limits. The gap can be large for batteries, where timing is the whole business. Developers need dispatch modelled realistically at design stage to size storage. Asset managers need it measured in operation, because a weak strategy loses money every day while nothing on the plant looks broken.
A worked example
A 20 MW, 40 MWh battery charges 40 MWh between 1 pm and 3 pm at $25/MWh, costing $1,000. At 88% round-trip efficiency it can discharge 40 × 0.88 = 35.2 MWh. Sold from 7 pm to 9 pm at $90/MWh, that earns $3,168, a margin of $2,168. Had it waited until 8 pm to 10 pm, when the price averaged $110/MWh, it would have earned 35.2 × 110 = $3,872, a margin of $2,872. The plan captured 2,168 ÷ 2,872 = 75% of the available value.
Illustrative figures.
Across markets
In US organised markets, the system operator dispatches centrally. Plants submit offers and receive setpoints, typically every five minutes. Most of Europe uses self-dispatch. Each party schedules its own plants to balance its position, and the grid operator steps in for balancing and congestion. In India, generators declare 15-minute schedules to the state or regional load despatch centre, which approves them and can order curtailment.