Market types in detail
A battery can serve several markets — but not all at once. Here are the sub-markets of the Irish electricity system, from Day-Ahead to reserves and capacity. They are hourly ALTERNATIVES, not stackable revenues.
Day-Ahead market (SEMOpx)
The reference market: a daily auction run by SEMOpx for the 24 hours of the following day — the basis of every arbitrage calculation.
Intraday market (SEMOpx)
Continuous adjustment after Day-Ahead: three intraday auctions plus a continuous market up to close to delivery, with finer granularity.
Balancing market (SEMO / EirGrid)
Near-real-time balancing run by the system operator EirGrid through SEMO — the all-island imbalance market that prices the balancing actions taken.
Imbalance settlement
Deviations between schedule and delivery are settled at the imbalance price — which makes the quality of imbalance settlement decisive.
Frequency regulation (FCR-type)
Fast frequency and reserve services (historically procured via EirGrid's DS3 programme): reserved capacity to stabilise frequency around 50 Hz, paid on capacity.
Secondary reserve (aFRR)
Automatically activated reserve (aFRR): controlled activation to restore the balance zone by zone, within the ENTSO-E framework.
Manual reserve (mFRR)
Manually activated reserve (mFRR): capacity mobilised on the transmission operator's instruction.
Capacity (Capacity Remuneration Mechanism)
The all-island Capacity Remuneration Mechanism (CRM) pays for guaranteed availability in peak periods, allocated through T-4 / T-1 auctions overseen by the SEM Committee.
Revenue stacking — alternatives, not additive
At hourly granularity these markets are ALTERNATIVES: the same MWh cannot serve arbitrage AND reserve at the same time.
Sources and regulation
The regulatory detail of each market falls under Irish law and is not asserted here in general terms.
References
Day-Ahead and intraday markets: SEMOpx (the all-island power exchange). Balancing market, system services and reserves: SEMO and EirGrid (transmission system operator, all-island with SONI). Regulatory framework: CRU (within the SEM Committee). The regulatory detail evolves — to be verified against the primary sources. Rules summary: /ie/rules/.