Wind stow losses happen when single-axis trackers move to a protective safe angle because measured wind is above the controller threshold. While the rows are off-angle they capture less sunlight. In the data you see intermittent output dips during gusty weather even though irradiance is good. These losses are easy to miss when they get lumped in with availability, curtailment or weather variance. Energy models built on hourly wind data can understate this loss, because controllers react to short gusts that hourly averages smooth out. Counting gust-driven stow can raise annual production losses by up to 4%. To confirm it, pull the tracker controller logs showing stow commands, return-to-track events, wind speed and the active threshold. Line these up with SCADA production, irradiance and inverter status so you can rule out clipping, curtailment, outages and sensor faults. Where you can, use high-frequency wind data such as three-second gusts or met mast records instead of hourly averages. Check the wind thresholds and the return-to-track logic. Do not lower stow thresholds to win back energy unless the tracker supplier and the structural engineer confirm the change stays within the design limits. Compare actual stow hours with the energy model assumptions, then update forecasts and variance reporting so the loss is tracked in its own category.
caused_byc1 verified · fact High winds
Stow is triggered when measured wind or short-duration gusts exceed the tracker controller threshold; hourly averages may stay below it.
sec=h4 h=65b80c7f6952sec=h5 h=3f9ef9562906verified by: joshuahamsaverified on: 2026-10-16
affectsc2 verified · fact Single-axis tracker
Rows move to a protective high-tilt or safe angle and capture less irradiance until they return to tracking.
sec=h4 h=65b80c7f6952verified by: joshuahamsaverified on: 2026-10-16
presents_asc3 verified · fact Low output despite irradiance
Intermittent, weather-correlated dips, especially when rows stow repeatedly in gusty weather.
sec=h4 h=65b80c7f6952verified by: joshuahamsaverified on: 2026-10-16
detected_byc4 verified · fact Wind gust data review
Three-second gusts, one-minute moving averages or met mast data explain tracker behavior better than hourly averages.
sec=h2 h=3c102c6647a1sec=h6 h=733de3a75bd0verified by: joshuahamsaverified on: 2026-10-16
c5 drafted · lead Performance monitoring
Compare SCADA production and POA irradiance-normalized output during windy periods against stow events.
sec=h2 h=3c102c6647a1sec=h6 h=733de3a75bd0mitigated_byc6 verified · fact Energy model update
Model stow losses with high-frequency gust statistics and reconcile actual stow hours against P50/P90 assumptions.
sec=h2 h=3c102c6647a1sec=h7 h=47f98047fafdverified by: joshuahamsaverified on: 2026-10-16
c7 verified · fact Production forecast update
Update forecasts when recurring gust-driven stow was not represented in the original model.
sec=h7 h=47f98047fafdverified by: joshuahamsaverified on: 2026-10-16
c8 verified · fact Tracker stow strategy
Verify wind thresholds and return-to-track logic; change thresholds only if the tracker supplier and structural engineer confirm it stays within the design envelope.
sec=h2 h=3c102c6647a1sec=h7 h=47f98047fafdverified by: joshuahamsaverified on: 2026-10-16
c9 verified · fact Loss factor separation
Track stow loss as a defined tracker operating mode rather than lumping it into availability, curtailment or weather variance.
sec=h4 h=65b80c7f6952sec=h7 h=47f98047fafdverified by: joshuahamsaverified on: 2026-10-16
distinguished_fromc10 verified · fact Inverter clipping — told apart by Tracker command log review
Aligning stow events with SCADA production, irradiance and inverter status separates stow loss from clipping.
sec=h6 h=733de3a75bd0verified by: joshuahamsaverified on: 2026-10-16
c11 verified · fact Grid Curtailment Yield Losses — told apart by Tracker command log review
Stow loss coincides with logged stow commands and high wind; curtailment shows in inverter or grid status without stow events.
sec=h6 h=733de3a75bd0verified by: joshuahamsaverified on: 2026-10-16review note: support check: partial - Separation from curtailment via aligned logs is stated, but the specific signature (curtailment shows in inverter or grid status without stow events) is not.
typical_power_lossc12 verified · fact ≤ 4 PERCENT
Conditions: Additional annual production loss when gust-driven tracker response is accounted for, compared with models using hourly wind data only (2026 kWh Analytics Solar Risk Assessment).
sec=h5 h=3f9ef9562906verified by: joshuahamsaverified on: 2026-10-16
explains c2distinguished_from c6