A day in the maze

Every quarter-hour is a turn. We already know the way.

ChargeWe buy when energy is cheap: the minimum of the day, with solar surplus.
WaitIn-house and third-party forecasts: we hold on until the spread pays off.
SellWe discharge at the day's peak and into the balancing services.
Re-optimiseEvery new forecast or price move recalculates the position.

Illustrative example: battery with 10 MWh usable, 1 cycle. It does not represent actual historical results.

In the market

How the electricity price moves in a day

Spanish day-ahead market prices, by quarter hour. A battery charges when power is cheap and discharges when it is expensive.

Day low119€/MWh▲ 60 % vs 30-day average

Day high300€/MWh▲ 7 % vs 30-day average

High–low spread181€/MWh▼ 12 % vs 30-day average

Average price of the day186€/MWh▲ 2 % vs 30-day average

Max–min spread of the curve181 €/MWh

Charge: 4 cheapest hoursDischarge: 4 priciest hours

Drag across the chart or use the arrow keys to see every quarter-hour.

Public OMIE data (day-ahead market, Spain). Latest day available: Nov 13.

Active management

Slide to see what changes in the two units of a 5 MW battery when someone re-optimises after the day-ahead market.

Illustrative example · 5 MW / 10 MWh

Day-ahead marketIntradayTechnical constraintsTertiary reserve

Without active managementDay-ahead schedule, never re-optimisedWith active managementRe-optimises after every market

Delivers energy to the grid

Takes energy from the grid

1,990 € · Day total

3,018 € · Day total

+1,028 €

more that day with active management (+52 %)

Second cycle In the intraday market it buys at night and sells into the morning peak, on top of the day-ahead cycle.
Technical constraints After the day-ahead market, REE checks that the schedule is safe for the grid and can ask specific units to produce more or less. The battery bids into that process: if REE calls it, the change becomes part of its firm schedule and is paid at the bid price.
Tertiary reserve Part of the battery stays available for REE to activate in real time, at that market's price.

Made-up example to explain the mechanism: values close to reality, but not data from any asset, company or real day. 5 MW / 10 MWh battery.

An asset's day

D-1 · 12:00
Day-ahead market96 quarter-hour periods of the next day
D-1 · ~14:00
Technical constraintsREE rebalances the schedule
D-1 15:00 · 22:00 · D 10:00
Intraday · auctions3 European auctions
24/7 until 1 h before
Intraday · continuous24/7 operation, contract by contract
D-1 17:00 band · D energy
Secondary reserve (aFRR)Reserved band and automatically activated energy
D · until 25 min before
Tertiary reserve (mFRR) and real timeUp and down on REE's request

How it works

Needs