Helical Screw Piles for Solar Racking: A Comprehensive Overview
2026-03-30
1. What Are Helical Screw Piles?
Helical screw piles are steel shafts with one or more helical plates (blades) welded to them. They are installed by rotating them into the soil using hydraulic drive heads or handheld equipment. Once installed, the pile derives its load‑bearing capacity from the interaction between the helical plates and the surrounding soil.
| Component | Function |
|---|---|
| Shaft | Transmits loads from the solar racking to the helical plates |
| Helical Plate(s) | Bears against the soil, providing uplift and compression resistance |
| Termination | Flange or bracket for attaching the solar mounting structure |
2. Key Advantages
| Advantage | Description |
|---|---|
| No Concrete | Eliminates concrete mixing, curing time, and formwork; reduces embodied carbon by up to 60% |
| Fast Installation | Typically 2‑5 minutes per pile; projects can be installed in days rather than weeks |
| Immediate Loading | Piles can be loaded immediately after installation – no waiting for concrete to cure |
| Removable & Reusable | Piles can be unscrewed and reused or recycled at the end of the project lifecycle |
| Minimal Site Disturbance | No excavation, no soil disposal; preserves topsoil and vegetation |
| Terrain Adaptability | Can be installed on slopes, uneven ground, and in areas with limited access |
| All‑Weather Installation | Can be installed in wet or freezing conditions where concrete is impractical |
3. Common Types of Helical Screw Piles
| Type | Configuration | Applications |
|---|---|---|
| Single‑Helix | One helical plate near the tip | Suitable for sandy or granular soils; moderate load requirements |
| Double‑Helix | Two helical plates spaced along the shaft | Higher load capacity; suitable for mixed or softer soils |
| Square Shaft | Solid square steel bar; welded helix | High torsional strength; common for residential and light commercial |
| Round Shaft (Pipe) | Hollow steel pipe; continuous or segmented helix | Larger diameters; higher load capacity; common for utility‑scale solar |
| With Flange | Pre‑welded top flange for bolted connection | Direct attachment to steel mounting structures |
| Adjustable Height | Threaded extension allows fine height adjustment | Compensates for terrain irregularities |
4. 2024 Technology Trends
| Trend | Description |
|---|---|
| 50% Steel Savings | Nextracker NX Anchor achieves 50% less steel and 70% less embedment depth compared to conventional piles |
| 30‑Year Maintenance‑Free Life | Hot‑dip galvanized to UNE EN ISO 1461 (≥80 μm) for corrosion protection; Zn‑Al‑Mg coatings provide self‑healing properties |
| GPS‑Guided Installation | Patented rigs (e.g., Ojjo Truss Driver) with GPS positioning ensure precise alignment and torque monitoring |
| Localised Soil Adaptation | Companies like Ground Screw Company offer custom helix designs for specific soil types (clay, rock, sand, soft soil) |
| 2‑Minute Installation | Modern equipment installs a pile in 2‑3 minutes; crews can install hundreds per day |
| Integration with Trackers | Piles designed specifically for single‑axis trackers with torque tube attachments |
5. Technical Specifications (Typical)
| Parameter | Small‑Scale (Residential) | Large‑Scale (Utility) |
|---|---|---|
| Shaft diameter | 48‑76 mm (2‑3 in) | 89‑219 mm (3.5‑8.6 in) |
| Wall thickness | 3.0‑4.5 mm | 4.5‑9.5 mm |
| Helix diameter | 150‑250 mm | 200‑450 mm |
| Pile length | 1.2‑2.5 m | 2.0‑6.0 m |
| Tensile strength | 20‑35 kN | 50‑150 kN |
| Compression capacity | 30‑60 kN | 80‑300 kN |
| Torque installation | 1,000‑2,500 Nm | 3,000‑12,000 Nm |
| Corrosion protection | Hot‑dip galvanized (≥65 μm) | Zn‑Al‑Mg coating or HDG (≥85 μm) |
| Design life | 25‑30 years | 30‑50 years |
6. Installation Process
| Step | Description |
|---|---|
| 1. Site Assessment | Soil testing (SPT, CPT) to determine helix configuration and required depth |
| 2. Layout | GPS or total station positioning of each pile location |
| 3. Pilot (optional) | Pre‑drilling may be required for very dense or rocky soils |
| 4. Screwing | Hydraulic drive head rotates pile to design depth; torque monitored in real time |
| 5. Torque Verification | Final torque confirms load capacity (correlated to soil strength) |
| 6. Height Adjustment | Piles cut or extended to design height; flanges welded or bolted |
| 7. Mounting Attachment | Solar racking bolted or welded to pile flanges |
7. Suitability by Soil Type
| Soil Type | Suitability | Recommended Helix Configuration |
|---|---|---|
| Sand / Gravel | Excellent | Single‑helix, larger helix diameter |
| Clay | Excellent | Double‑helix, smaller pitch |
| Silt | Good | Single or double‑helix; longer embedment |
| Soft / Organic | Fair | Double‑helix, deep embedment; may require pre‑drilling |
| Rock / Cobbles | Poor | Pre‑drilling or rock socket required; not recommended for standard screw piles |
| Frost‑Prone | Suitable | Helices placed below frost line; reduced surface area minimizes frost heave |
8. Application Examples
Example 1: Agrivoltaics (10 MW)
Soil: Clay loam
Pile: 114 mm diameter, double‑helix, 2.5 m length
Installation: 2 minutes per pile; 150 piles/day with 2 crews
Result: No concrete, no soil compaction; crops planted immediately after installation
Example 2: Utility‑Scale Tracker Plant (100 MW)
Soil: Sandy loam
Pile: 89 mm diameter, single‑helix, 2.0 m length; Nextracker NX Anchor
Installation: GPS‑guided rig, torque‑monitored
Result: 50% less steel, 70% less embedment; 40% faster foundation completion
Example 3: Residential Ground‑Mount (5 kW)
Soil: Rocky clay
Pile: 76 mm diameter, double‑helix, 1.8 m length, adjustable flange
Installation: Handheld equipment, 10 piles in 1 hour
Result: No excavation, removable at end of lease, minimal yard disturbance
9. Comparison with Concrete Foundations
| Factor | Helical Screw Piles | Concrete Piers |
|---|---|---|
| Installation time | Minutes per pile | Days (forming, pouring, curing) |
| Curing | Immediate loading | 7‑28 days cure time |
| Concrete volume | None | 0.5‑1.5 m³ per pier |
| Excavation | Minimal – no spoils | Required; soil disposal |
| Removability | Yes – can be unscrewed | No – demolition required |
| Cost (per kW) | $0.02‑0.04/W | $0.04‑0.08/W |
| Environmental impact | Low | High (cement CO₂, soil disturbance) |
| Terrain adaptability | Excellent (slopes, tight access) | Moderate (requires level access) |
10. Selection Guide
| Project Type | Recommended Pile | Key Considerations |
|---|---|---|
| Residential ground‑mount | 48‑76 mm, single‑ or double‑helix, adjustable flange | Yard disturbance, removable for future use |
| Agrivoltaics | 89‑114 mm, double‑helix, longer embedment | Avoid soil compaction, allow deep rooting |
| Utility‑scale fixed tilt | 89‑114 mm, single‑ or double‑helix, driven to torque | High production rates, GPS layout |
| Tracker systems | 89‑114 mm, designed for torque tube connection | Torsional resistance, precise alignment |
| Coastal / high corrosion | Zn‑Al‑Mg coated steel or stainless steel | Salt‑spray resistance, C5 environment |
| Temporary / leased site | 76‑114 mm, with flange | Removability, no concrete, minimal restoration |
11. Standards and Testing
| Standard | Scope |
|---|---|
| ASTM A572 / A500 | Steel material specification |
| ASTM A123 / A153 | Hot‑dip galvanizing |
| ASTM D1586 (SPT) | Soil penetration testing |
| ASTM D1143 | Load testing of piles |
| ICC‑ES AC358 | Acceptance criteria for helical piles (US) |
| UNE EN ISO 1461 | Hot‑dip galvanizing (Europe) |
In a Nutshell
Helical screw piles have become the foundation of choice for many solar projects in 2024, offering:
Concrete‑free installation – faster, lower carbon, removable
Immediate loading – no curing delays
Minimal site impact – preserves soil and vegetation
Proven performance – 30‑year+ service life with proper corrosion protection
Scalability – from residential to utility‑scale (100 MW+)
With innovations like Nextracker‘s NX Anchor (50% steel savings) and advanced Zn‑Al‑Mg coatings, helical screw piles are setting a new standard for sustainable, efficient solar foundations.
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