Dispatch down is a term used by the Irish power grid – EirGrid, as the transmission system operator – it refers to power that is produced but cannot be used. Renewable generation is prioritised by the power grid’s control centres. However, there will be times when it is not possible to accommodate all priority dispatch generation while maintaining the safe, secure operation of the power system. Security-based limits must be imposed due to both local network and system-wide security issues. It is necessary to reduce the output of renewable generators below their maximum available level when these security limits are reached. This reduction is referred to as ‘dispatch-down’ of renewable generation.
There are two reasons for the dispatch-down of wind and solar energy: constraint and curtailment.
- Constraint refers to the dispatch-down of wind and solar generation for localised network reasons (where only a subset of wind/solar generators can contribute to alleviating the problem).
- Curtailment refers to the dispatch-down of wind/solar for system-wide reasons (where the reduction of any or all wind/solar generators would alleviate the problem).