Western Australia is building one of the world's most ambitious solar pipelines. The structural engineering challenges of large-scale solar farms in WA require rigorous analysis that goes well beyond standard practice.
Western Australia is in the middle of the most rapid solar energy buildout in its history. Driven by mining companies decarbonising their Pilbara operations, state renewable energy targets, and the emerging hydrogen export sector, the WA solar pipeline has grown from aspirational to fully active within three years. The engineering supply chain challenge that comes with it is substantial, and the structural engineering component, which is often treated as routine, is anything but in the WA context.
Solar farm structural engineering in WA is not the same as solar farm structural engineering in temperate European or east-coast Australian climates. The Pilbara and Goldfields regions where most large-scale WA solar development is occurring present a specific combination of environmental conditions, soil types, and operational requirements that demand specialist structural analysis. Wind loading in Wind Region D, cyclone design compliance, expansive clay soils, extreme temperature cycling, and remote site logistics all add layers of engineering complexity that a generic tracker system specification will not address.
This article sets out the key structural engineering considerations for utility-scale solar farms in WA, the design standards that apply, what can go wrong when structural engineering is treated as a procurement checkbox, and how Grispen Australia supports solar EPC contractors and developers in this market.
The scale of WA's solar development programme is significant enough to warrant naming the key projects driving it. These are not aspirational announcements, they are projects in construction or advanced development right now:
Fortescue's 440 MW Solomon Airport Solar Farm, when complete, will be the state's largest solar development. Fortescue's Solar Innovation Hub at Cloudbreak is being used as a 500 MW test bed for emerging technologies, with ARENA investing up to AUD 45 million to trial innovations including automated pile-driving robotics and rapid-deployment Maverick solar technology.
Rio Tinto has committed to building two 100 MW solar facilities in the Pilbara with 200 MWh of on-grid battery storage, with solar panels built to withstand the Pilbara's cyclonic conditions, as part of a 1 GW renewable energy target.
This is the pipeline that WA structural engineers are being asked to support. The question is whether the engineering supply chain is equipped for the structural complexity the WA environment demands.
The Pilbara and Goldfields regions where most large-scale WA solar development is occurring are among the most structurally demanding environments for solar infrastructure in the world. The combination of high wind speeds, cyclone exposure, expansive clay soils, and extreme temperature cycling creates a set of structural engineering requirements that are significantly more complex than those encountered at equivalent solar sites in southern Australia or Europe.
Most of the Pilbara and coastal WA falls within Wind Region D under AS/NZS 1170.2, the highest wind loading classification in Australia. Design wind speeds at 500-year return periods in Region D can reach 85 m/s (306 km/h) for cyclone conditions. Solar tracker structures designed to generic temperate-climate specifications will not be adequate in Region D without site-specific cyclone analysis and stow position verification.
Single-axis tracking systems, which dominate utility-scale solar installations for their energy yield advantage, are aerodynamically complex structures. The torsional resonance behaviour of tracker arrays under wind loading, particularly at intermediate tilt angles or in stow position, must be explicitly analysed. Vortex-induced vibration and galloping instability are real failure modes at WA wind speeds that generic tracker datasheets do not adequately address.
Significant areas of WA's agricultural and semi-arid zones have highly reactive clay soils (Class E and P under AS 2870) that expand and contract with moisture variation. Foundation design for solar tracker piles in reactive soil must account for differential movement, soil suction effects, and the cumulative fatigue loading on pile-to-purlin connections over the project's 25-30 year design life.
Pilbara ambient temperatures regularly exceed 45°C in summer and can fall below 5°C at night during winter. Steel tracker structures, aluminium panel frames, and their connections experience significant thermal expansion and contraction cycling over a 25-year design life. Bolted connections, bearing assemblies, and torque tube welds must be designed for the full thermal strain range, not a temperate-climate default.
The Pilbara operates in a red dust environment with iron ore particulate. Combined with high UV radiation and occasional salt-laden coastal winds, the corrosion environment for steel solar structures is more aggressive than metropolitan or agricultural solar sites. Coating specifications, galvanising thickness, and stainless steel fastener selection all require site-specific assessment rather than generic product specification.
Large WA solar sites are often hundreds of kilometres from the nearest structural fabrication facility. Structural elements must be designed for efficient transport (road train compatibility, pile bundle configurations), fast installation with limited crane capacity, and tolerance for workmanship variation in high-temperature remote conditions. Constructability engineering is not optional in the Pilbara.
Solar farm structural engineering in WA sits at the intersection of several codes, some mandatory, some industry-standard, and some specific to individual developer or EPC requirements. Understanding the hierarchy and interaction between these codes is a prerequisite for producing a structurally adequate and certifiable design package.
| Standard | Title | Application in WA Solar | Notes |
|---|---|---|---|
| AS/NZS 1170.2 | Structural Design Actions, Wind Actions | Primary wind loading standard. Region classification determines design wind speed. | Region D (most of Pilbara): highest category |
| AS/NZS 1170.1 | Structural Design Actions, Permanent and Imposed | Dead load, maintenance load, panel load combinations for tracker sizing | Include maintenance personnel load cases |
| AS 4100 | Steel Structures | Member capacity checks for tracker columns, torque tubes, purlins and bracing | Primary steel design code for WA |
| AS/NZS 4600 | Cold-Formed Steel Structures | Purlin and rail design where cold-formed sections are used | Required for thin-walled tracker components |
| AS 2159 | Piling, Design and Installation | Driven pile design for tracker foundations | Including pull-out capacity for wind uplift |
| AS 2870 | Residential Slabs and Footings (Soil Classification) | Soil reactivity classification for foundation design in expansive clay areas | Class E and P sites require specific foundation approach |
| AISC 360-16 | Specification for Structural Steel Buildings | Applicable where US-based EPC or tracker manufacturer's design basis references AISC | Reconciliation with AS 4100 required |
| ASCE/SEI 7 | Minimum Design Loads for Buildings | Where US-based EPCs use ASCE for wind loading instead of AS 1170.2 | Always verify against AS 1170.2 Region D for WA |
| IEC 61400 / AS | Wind turbine structural standards (reference) | Referenced for cyclone-rated tracker certification documentation | Tracker vendor certification documents |
Many solar tracker manufacturers and US-based EPC contractors present structural certifications based on ASCE/SEI 7 wind loading. In temperate US climates, ASCE 7 design wind speeds are broadly comparable to AS 1170.2 Region A2 or B. In the WA Pilbara (Region D), they are not. An ASCE-certified tracker that meets V = 50 m/s (ultimate, 700-year return) may be structurally inadequate at the site-specific WA design wind speed. Certification to ASCE in the US does not constitute certification to AS 1170.2 Region D in Australia. This distinction must be confirmed before any tracker procurement is finalised.
When a solar EPC contractor or developer commissions structural engineering for a WA solar farm, the scope is broader than many project managers initially anticipate. Here is what a complete structural engineering package for a WA utility-scale solar farm covers:
Site-specific wind region classification, terrain category assessment, topographic multiplier evaluation, and design wind speed derivation to AS/NZS 1170.2. For Region D sites, cyclone design wind speed and direction factors must be separately assessed.
Verification that the proposed tracker system's structural certification is valid for the site's wind region, soil conditions, and pile spacing. Tracker vendor test data must be reconciled against AS standards, not assumed to be equivalent.
Driven pile design for tracker foundations based on site geotechnical investigation data. Includes pull-out capacity for wind uplift, lateral load capacity for horizontal wind force, pile embedment depth for required soil type, and pile spacing optimisation.
Structural design for inverter stations, transformer bays, switchgear buildings, and substation structures. Steel frame design to AS 4100, connection design, crane load path analysis for maintenance access.
Structural design of cable tray support structures, underground conduit systems, and inter-row cable management. Wind and self-weight loading in high-temperature conditions, stainless or galvanised steel specification.
Structural design of security fencing, gate structures, CCTV mounting frames, and access control infrastructure. Wind loading per AS 4687 (temporary fencing) and AS 1725 (permanent fencing) for cyclone-exposed sites.
Structural design of O&M facilities, control rooms, and storage buildings. AS 4100 steel portal frame or masonry wall panel construction for remote Pilbara sites. Cyclone tie-down design for roofing systems.
Review of structural design for Pilbara construction conditions: road transport compatibility, pile installation equipment access, tolerance management for high-temperature erection, and connection sequence for remote workforce capability.
Preparation of structural certification documentation for building permit submission and EPC contractor QA requirements. Includes calculation reports, structural drawings, material specifications, and NCC compliance statement.
Of all the structural engineering challenges in WA solar farm design, the cyclone stow position analysis is the most frequently underestimated. It is also the one that carries the most severe consequences if it is wrong.
Single-axis tracking systems have a defined stow position, typically a flat (0°) or slightly tilted orientation, to which the tracker automatically moves when wind speeds exceed a threshold, usually around 15-18 m/s. The intent is to minimise wind loading on the panels in high-wind events. However, in a cyclone scenario, the stow position itself must be structurally verified for the extreme design wind speed, because the tracker will reach its stow limit and remain there for the duration of the event.
"The tracker stow position was certified to 45 m/s. The site wind design speed was 58 m/s. The certification was for a different wind region entirely. No one caught it until the structural review two weeks before construction."
Project engineer comment, Pilbara solar project, reported to Grispen Australia during a peer review engagementThe structural verification of the cyclone stow position requires:
A tracker structural certification that is valid for a WA Pilbara site should explicitly state: the Australian wind region (Region D), the site terrain category, the ultimate design wind speed in m/s, the stow tilt angle analysed, the aerodynamic coefficients applied and their source (wind tunnel test data preferred), and the applicable structural standard (AS 4100 or AISC 360-16 with reconciliation note). A certification that states only "certified to 45 m/s to ASCE 7" without Australian standard reconciliation is not adequate for Region D WA.
The most variable and site-specific element of solar farm structural engineering is the pile foundation system. Tracker systems are typically supported on driven steel I-piles or C-section piles at spacing of 4-8 metres along the tracker row, driven to depths of 1.2-2.5 metres depending on soil conditions and design loads.
In WA, three distinct foundation engineering challenges arise that are not commonly encountered on east-coast Australian or European solar sites:
Many Pilbara sites encounter laterite duricrust at shallow depth, often 0.3-0.8 metres below surface. This highly variable horizon creates significant pile installation challenges. Pile refusal before reaching adequate embedment is common. Foundation design must account for the possibility of early refusal, specify alternative pile configurations for laterite zones, and provide clear specification for when rock bolting or alternative foundation types are required.
Solar sites in southwest WA, including some of the agricultural and commercial zones being developed for utility-scale solar, encounter highly reactive clay soils classified as Class E or P under AS 2870. These soils can heave or subside by 40-70 mm seasonally depending on moisture. Driven pile foundations in reactive clay must be designed for the suction and heave forces that act on the pile as the soil moves around it, not just the static load case from panel and wind loading above ground.
In the Goldfields region, sites may encounter calcrete (caliche) or weathered rock at very shallow depths. The combination of high surface hardness and variable depth creates an uneven founding condition across a large array. Structural design must establish clear pile acceptance criteria, depth variation tolerance, and remedial procedures for pile installations that cannot achieve design embedment.
Grispen Australia's structural engineering team brings a combination of direct solar project experience, onshore structural analysis capability, and the AS 4100, ASCE/SEI 7, and AISC 360 design credentials required for solar farm structural packages in WA. Our onshore structural engineering experience includes skid-mounted process equipment (HOLT Industrial Systems Hybrid Solar Skid), process facility structural design, and industrial structure assessment under ASCE/SEI 7 and AS standards.
For WA solar farm structural engineering scopes, we provide:
Grispen Australia is a Perth-based structural engineering and project management firm supporting the WA solar energy market. We deliver site-specific structural engineering packages for utility-scale solar farms, with particular expertise in WA's cyclone-exposed Pilbara and Goldfields regions.
Our structural engineering is produced to AS/NZS 1170.2, AS 4100, AISC 360-16 and ASCE/SEI 7 standards using ANSYS Mechanical, Staad Pro and Mathcad Prime. We work directly with EPC contractors, developers, and tracker manufacturers to ensure that structural certification is valid for the specific site conditions of Western Australia, not generic temperate-climate defaults.
Western Australia's solar pipeline is real, large, and moving fast. The structural engineering that underpins it is more complex than many project managers and developers initially expect. Wind Region D classification, cyclone stow position verification, reactive soil foundations, and the ASCE vs AS 1170.2 certification gap are all areas where inadequate structural engineering creates risks that become expensive to resolve after procurement has been finalised or construction has begun.
The time to address these structural considerations is during FEED and early detailed design, before the tracker system is specified, before the foundation contractor is mobilised, and before the structural certification is assumed to be adequate because it passed review in a different climate. Getting the structural engineering right at the outset is one of the most cost-effective decisions a WA solar developer or EPC contractor can make.
Grispen Australia is available to discuss structural engineering requirements for your WA solar project at any stage of development. We respond to all genuine enquiries within one business day.
Bertrand leads Grispen Australia from Perth, Western Australia, with extensive experience in structural engineering and project management for energy, offshore and mining sectors across APAC and globally.