Time series curtailment efficiencies

Modern turbine curtailment strategies, such as noise or bat curtailments, often switch mode of turbine operation dependent on time of day or year. To model this we must work in the time domain.

The power time series calculation calculation is capable of calculating the impact of curtailment strategies by utilising flexible curtailment rules that cause turbine mode switches based on a combination of rules evaluated against the turbine inflow conditions.

WindFarmer can derive an overall curtailment efficiency from all combined curtailment types or a breakdown of efficiencies per curtailment type.

Overall efficiency calculation

This calculation can be useful to quickly know the impact on energy production of all the defined curtailment types.

To calculate this efficiency per turbine and per farm, WindFarmer first calculates a power time series with all curtailments types active and identifies in which timestamps the turbines are not in the normal operational mode. Those time stamps are then recalculated without any curtailment types.

WindFarmer then calculates an AEP with and without curtailment types to derive the efficiency. The AEP is calculated using a sum of monthly mean energy production. This method is accurate as long as there isn't significant data coverage bias by time of day.

Breakdown efficiency calculation

To calculate the breakdown of efficiencies per curtailment type, an approach similar to the overall is used. First, the time series with all curtailment types active is calculated. Secondly, the time stamps where turbines are not in normal operation are successively calculated with one of the types removed by its priority order.

An AEP for each of the removed curtailment types is calculated and its efficiency derived by comparing it with the case in which it was applied.