Solar Tracker

Quick Facts

What is a Solar Tracker?

Solar trackers rotate PV modules through the day to track the sun’s apparent motion across the sky. By maintaining a near-perpendicular angle of incidence, they boost annual energy yield.

Types

• Horizontal Single-Axis Tracker (HSAT) — Dominant utility design. Modules mounted on a north-south torque tube; rotate east-west.
• Tilted Single-Axis Tracker (TSAT) — Tilted axis (often latitude-tilted) with seasonal rotation. Rare today.
• Vertical Single-Axis Tracker (VAT) — Rotates around vertical axis with fixed tilt. Used in northern latitudes.
• Dual-Axis Tracker — Rotates both east-west and seasonally. Niche use.

Yield Gain

These figures are typically modeled at P50 confidence in a yield simulation; lenders will usually also want to see the P90 and P99 downside cases spelled out in the yield report — our P50/P90/P99 explainer covers how that uncertainty band is built.

Backtracking

In early morning and late afternoon, naive tracking would aim modules at low sun, but front-row modules would shade back rows. Backtracking software rotates trackers slightly off-sun to avoid mutual shading.

Energy recovery: 3–5% annual. Implementation: tracker controller computes solar position + neighbor geometry continuously. For a closer look at the geometry and control logic behind this calculation, see our breakdown of the backtracking algorithm for solar trackers.

Engineering Deep Dive

Components

• Torque tube — Steel beam running north-south.
• Modules mounted on tube via clamps.
• Drive system — slewing drive or linear actuator.
• Controller — microcontroller with sun-position algorithm + backtracking.
• Foundation — driven piles, screw piles, or ballasted pads.
• Wind stow — automatic flat-stow during high wind.

Drive technology

• Slewing drive (worm-gear): high torque, simple control.
• Linear actuator (push-rod): cheaper, common in modern designs.

Foundation

• Driven piles (steel H-beam or W-flange): most common, fast installation.
• Screw piles: in poor soil.
• Concrete piers: in rocky or unstable soil.
• Ballasted: rare for tracker due to dynamic loads.

Pile depth and type selection should be driven by an actual soil report rather than a rule of thumb — our pile foundation design guide for solar ground-mount walks through the soil-to-pile decision process in more depth.

Geotechnical

Trackers transfer high overturning moments to the soil. Geotech investigation includes:

• Standard penetration test (SPT).
• Borehole drilling to 6–10 m depth.
• Lateral load testing on prototype piles.

ASCE 7-22 wind on trackers

Section 29.4.4 of ASCE 7-22 provides specific wind coefficients for solar trackers. New 7-22 provisions:

• Wind tunnel-derived GCp for stowed vs. operating positions.
• Aeroelastic flutter consideration for long torque tubes.
• Stow angle and stow wind speed specifications.

Design Considerations

• Site terrain. Trackers need flat ground (slope < 5%). Variable-tilt trackers handle 5–15% slopes; >15% needs terraced design.
• Row spacing. GCR 0.30–0.40 for trackers; lower than fixed tilt.
• Foundation type. Match to soil; budget 30–50% of tracker cost.
• Wind stow. Configure stow angles in tracker controller. Validate against site-specific 100-year wind.
• Soiling. Tracker can self-clean by stowing at night; helps in dusty climates.
• Snow. In snow-prone regions, configure aggressive stow tilt at night to shed snow.

Permitting & Compliance

• ASCE 7-22 for wind loads.
• Local geotechnical report.
• AHJ structural review of pile design.
• UL 3703 listing for tracker electronics.
• Interconnection: tracker SCADA reports operating status to utility.

Common Mistakes

1. Tracker on slope > 5% without proper variable-tilt or terracing.
2. Pile depth insufficient for soil conditions.
3. Stow logic not configured for site-specific wind.
4. Backtracking algorithm mis-calibrated for actual row spacing.
5. Ignoring snow load in northern climates.
6. Mixing module sizes on single torque tube (mismatch).

Best Practices

• Validate tracker site placement with detailed geotech investigation.
• Specify wind stow threshold per ASCE 7-22 site-specific calc.
• Commission backtracking with field validation (sun-position vs. tracker angle).
• Maintain controller firmware updates.
• Plan for module-replacement access (every 25 years).

Comparison Tables

Tracker vs. Fixed Tilt

Standards & Certifications

• ASCE 7-22 — Wind, snow, seismic loads.
• AISC 360 — Steel design.
• UL 3703 — Tracker listing.
• IEC 62817 — Tracker test methodology.

Key Takeaways

• Solar trackers rotate PV modules to follow the sun, boosting annual yield 15–25%.
• Horizontal single-axis tracker (HSAT) is the dominant utility-scale design.
• Backtracking software prevents row-to-row shading at low sun angles.
• Tracker + bifacial = 25–35% combined gain over fixed monofacial.
• Economical mainly at utility scale; foundation and structural design driven by ASCE 7-22.

Related Reading

Trackers only deliver their promised yield when the underlying simulation and structural work is done right. Our PVsyst tracker yield study methodology walks through modeling HSAT gains and backtracking losses in a near-shading scene, and the wider survey of PV yield simulation software options is a useful next stop for teams still choosing a tool. On the structural side, tracker torque tubes and driven piles see different load cases than fixed-tilt racking, so the comparison of SAP2000, STAAD Pro, and manual calculation methods is directly relevant to tracker foundation design. Readers deciding whether tracking is worth the added cost and land use for a given site may also want the primer on how auto solar tracking systems compare across designs.