Wind Stow

Summary

Wind Stow is a protective mechanism that commands single-axis trackers to a specified angle when wind conditions exceed safe operating limits. PlantPredict supports two wind stow implementations: PlantPredict Wind Stow (threshold-based comparison using wind gust speed) and Array Technologies Wind Stow (external API-based calculation using proprietary algorithms). Wind stow has the highest priority in the tracker angle determination hierarchy, overriding both base tracking and irradiance optimization.

Inputs

Name	Symbol	Units	Description
Wind Gust Speed	$v_{gust}$	m/s	Wind gust speed from weather data
Wind Stow Threshold	$v_{threshold}$	m/s	Threshold for stow activation
Stow Dwell Time	$t_{dwell}$	min	(PlantPredict mode only) Minimum time $v_{gust}$ must stay at or below $v_{threshold}$ after a stow before normal tracking resumes
Current Tracker Angle	$\alpha$	degrees	Tracker rotation angle before wind stow check
Wind Stow Angle	$\alpha_{stow,wind}$	degrees	Stow position

---

Outputs

Name	Symbol	Units	Description
Commanded Tracker Angle	$\alpha_{final}$	degrees	Final tracker rotation angle after wind stow logic

---

Detailed Description

Override Hierarchy

Wind stow has the highest priority in PlantPredict’s tracker angle determination. When wind stow is activated, it overrides both the base tracking angle and any irradiance optimization adjustments.

The terrain-aware backtracking algorithm is not compatible with the irradiance optimization and wind stow algorithms; it operates as a standalone tracking mode.

PlantPredict Wind Stow

PlantPredict’s built-in wind stow activates when wind gust speed exceeds the configured threshold:

$$v_{gust} > v_{threshold}$$

When triggered, the tracker moves to the stow angle while preserving its east/west orientation:

$$\alpha_{final} = \text{sign}(\alpha) \times \alpha_{stow,wind}$$

This mode requires WindGust data in the weather file; wind gust values are not synthesized from mean wind speed.

Stow dwell (reset delay)

After a stow event, the tracker remains at the wind stow angle until $v_{gust}$ has been at or below $v_{threshold}$ for a continuous period of $t_{dwell}$ (minutes). Elapsed time is accumulated using the weather file timestep; if a gust again exceeds the threshold before the dwell completes, the timer resets. This models operator delay to avoid rapid stow/tracking cycling.

A Stow Dwell Time of zero minutes reproduces the prior behavior of resuming in the same timestep in which the gust is below the threshold. The input appears on the DC Field Table tab when Wind Stow Model is PlantPredict (not for Array Technologies mode). The default for new DC Fields is 30 minutes; a null value is treated as 0 for existing projects. See also Table.

Array Technologies Wind Stow

When configured to use Array Technologies mode, PlantPredict sends tracker configuration and weather data to the Array Technologies API. The service performs proprietary wind stow calculations and returns time-series of stow angles. PlantPredict applies the returned angles directly, overriding internal tracking calculations. The Array Technologies algorithms are proprietary and not documented here.

---