Start with what the array sits on
The surface decides the family of structure, and the family decides most of the cost and risk.
| Surface | Structure | Material | What it solves |
|---|---|---|---|
| Concrete flat roof | Anodized aluminium 6063 T5 (L2, L3). SS400 iron, galvanized or painted (elevated shed). | Adds tilt to a flat surface. An elevated shed lifts the array above rooftop obstacles and cuts shading losses. | |
| Shell roof (arched concrete) | SS400 iron, hot-dip galvanized to ASTM A123, 90 microns. | Built for the low load capacity of shell roofs and the direction of the beams. | |
| Steel or corrugated sheet roof | Anodized aluminium 6063 T5, SS304 fasteners. | Keeps weight low and the roof watertight. | |
| Open land | SS400 iron, hot-dip galvanized to ASTM A123, 90 microns. | Sets tilt and row spacing freely and keeps modules easy to reach for cleaning. Concrete piles suit rocky or sandy soil where pile drivers are not suitable. | |
| Car park | SS400 iron, hot-dip galvanized to ASTM A123, 90 microns. | Gives shade for vehicles and generates power above them. | |
| Garden, terrace or farm | SS400 iron, galvanized or painted. | A gazebo gives a usable space below an east-west array. A mono pole is a manual dual axis tracker for irrigation and pump systems. |
Every FERO structure is designed to a standard wind speed of 35 m/s (126 km/h), customizable. Every FERO structure carries a 10 year warranty, galvanized iron and anodized aluminium alike. Galvanized iron is hot-dip coated to ASTM A123 at 90 microns, the basis of the warranty. Ask us for the written terms and we will send them with your quotation.
Wind decides the section sizes
Wind is usually the governing load on a solar structure. Uplift on the edges and corners of a roof array is greater than in the middle, so connections matter more than the main members. A design wind speed is set from the site location and the height of the structure, and exposed sites need a higher basis. Our standard design basis is 35 m/s, about 126 km/h, and it can be customized. Ask any supplier what wind speed their quote assumes and whether it applies to your site.
Check what the roof or soil can carry
A roof carries the weight of the modules and structure, plus the uplift and the ballast or anchors that resist it. A structural engineer should confirm the roof capacity before a design is final. For soil, the foundation type depends on the soil bearing capacity and the load: driven piles suit many soils, while concrete piles suit sites where driving is not practical. Foundation type is therefore decided from the site, not taken from a catalogue.
Roof and soil load checklist
- The weight of the modules and the structure.
- Wind uplift, which is greater at the edges and corners of a roof array than in the middle.
- The ballast or anchors that resist that uplift.
- For a shell roof, the direction of the beams: north to south or east to west.
- For open ground, the soil bearing capacity, which decides between driven piles and concrete piles.
- A structural engineer's confirmation of the roof capacity before the design is final.
Pick the material for the job
- Hot-dip galvanized iron suits long spans and heavy loads. Galvanizing after fabrication covers cut edges, holes and welds. ASTM A123 sets the minimum zinc thickness by steel thickness. FERO galvanized structures carry a 90 micron coating.
- Anodized aluminium 6063 T5 is lighter and does not rust, which helps on roofs with limited capacity and in humid or coastal air.
- Painted iron can lower the first cost, but the coating needs maintenance and will not protect a cut or a weld as well as galvanizing does.
Use compatible fasteners. Mixing metals without care invites corrosion at the joints.
Plan for cleaning and access
Dust is a recurring source of lost output in Pakistan. A structure that people cannot reach, or that leaves too little row spacing for a cleaning crew, makes cleaning slower and more expensive for the life of the plant. Tell the designer how the array will be cleaned before the layout is fixed.
Set tilt and spacing with the shading in mind
Pakistan runs from about 24 degrees latitude at Karachi to about 34 degrees at Peshawar. A fixed tilt near the local latitude gives the highest yearly energy, but a lower tilt reduces wind load and lets rows sit closer together. The right tilt is a trade between yield, wind and roof area, and the designer should show the shading calculation behind it.
- Karachi
- About 24 degrees latitude
- Peshawar
- About 34 degrees latitude
- FERO standard tilt
- 10 to 45 degrees, customizable
Common mistakes
- Choosing by steel weight alone. A heavier structure is not a stronger one if the connections are weak.
- Accepting a structure with no stated wind speed or galvanizing standard.
- Fixing the array before a structural engineer has checked the roof.
- Mixing metals and fasteners without checking compatibility.
- Leaving no path for cleaning.