Tracker stow

Tracker stow means moving a tracker to a safety position so that weather does not put critical loads on its parts and shorten their life. On a TerraTrak tracker with a plus or minus 60 degree range of motion, stow is triggered by the weather station wind speed, overnight stow at end of day, SCADA overrides, lost signal from the network controller, or snow and flood sensors. Operators can also command a global stow. On the DuraTrack HZ v3 they pick a preset angle of -52, 0 or +52 degrees to prepare for hail or severe weather. On GameChange trackers stow is enabled through Modbus registers that hold the stow angle. Night stow angles are set per site, and the vendor documents disagree. One Array source recommends 10 to 15 degrees, another recommends 0 to 10 degrees, and both say never to stow at or near the travel limits. Wind stow protects the structure from torsional divergence, resonance and fatigue. Do not lower stow thresholds to recover energy unless the tracker supplier and the structural engineer approve the change. The off-angle stow position cuts irradiance capture, so frequent gust-driven stow shows up as intermittent output dips. These are easily misfiled as availability or weather variance, and actual stow hours should be compared with the energy model assumptions. For hail, IEA PVPS describes defensive hail stow as a proven way to reduce damage. Where the manufacturer allows it, hail stow should override other stow modes, and sites should have several anemometers for good wind data.

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• sentence 2: support check: partial - Triggers match the list, but the passage doesn't name the product as TerraTrak.
• sentence 3: support check: partial - Presets and Modbus enable-stow registers with stow angle are stated, but the passages don't name DuraTrack HZ v3 or GameChange for these.
• sentence 4: support check: partial - The 10-15 and 0-10 recommendations and the never-stow-near-limits advice are present, but the 'never near limits' advice appears only in the first source, not both, and 'per site' is not stated.
• sentence 4: review: partial - Both recommendations (10-15 and 0-10 degrees) are present, but only the first source warns against stowing at or near the limits, and 'set per site' is not stated. -->