Carbon Steel for Solar Structures: The High‑Strength, Cost‑Effective Backbone of PV Mounting
2025-02-19
Carbon steel, with its outstanding strength, cost efficiency, and mature supply chain, forms the “skeleton” of PV mounting systems – especially for large‑scale ground‑mount power plants. It is the most widely used structural material in the industry.
The table below provides a quick overview of its core value:
| Feature | Description |
|---|---|
| High strength | Grades such as Q235B and Q355B offer yield strengths well above aluminum alloys, ensuring superior structural stability – ideal for high‑wind and heavy‑snow regions. |
| Cost‑effectiveness | The price per tonne is about one‑third that of aluminum, significantly reducing initial project investment. |
| Mature industry chain | Design, fabrication, and installation are highly standardised; components are pre‑punched and bolted – no on‑site welding – greatly shortening construction periods. |
| Recyclability | Scrap value after decommissioning is high (RMB 2,500‑3,000/tonne), further lowering the life‑cycle cost. |
| Well‑developed standards | Dedicated group standards have been issued for hot‑rolled and coated steel strips, ensuring consistent quality and performance. |
⚙️ Common Steel Grades
| Grade | Type | Yield Strength |
|---|---|---|
| Q235B | Ordinary carbon structural steel | ≥235 MPa |
| Q355B | Low‑alloy high‑strength steel | ≥355 MPa |
National standards recommend Q235 and Q355 grades. In large projects, Q355B is often used for critical load‑bearing components such as tracker columns because of its higher strength. The spread of high‑strength steel also allows thinner sections – for example, a corrosion‑resistant steel only 1.5 mm thick with a strength of 700 MPa has been trial‑produced to achieve lighter mounts.
🔩 Corrosion Protection Methods
| Method | Principle | Advantages | Applications |
|---|---|---|---|
| Hot‑dip galvanising (HDG) | Dipping steel into molten zinc to form a protective layer | Most mature technology, lowest cost, good overall performance | Widely used |
| Zn‑Al‑Mg coating (ZAM) | Zinc‑aluminium‑magnesium alloy coating with self‑healing ability | 5‑10× better corrosion resistance than HDG; protects cut edges | Harsh environments (high humidity, high salt spray) |
| Weathering steel | Alloying elements form a dense, protective rust layer | Can be used uncoated; green and maintenance‑free | Dry climates; emerging option |
Although national standards recommend an average hot‑dip galvanised coating thickness of at least 55 μm for steel mounts, the industry commonly specifies 65 μm to ensure a service life of 25 years or more. For Zn‑Al‑Mg coatings, corrosion resistance depends on the magnesium and aluminium content; sufficient coating weight must be selected to achieve 25‑year durability.
🏗️ Application Examples
Large‑scale projects: China National Petroleum Corporation launched a 3 GW PV mounting procurement in 2024, attracting 25 suppliers.
Export: Anyang Steel‘s self‑developed GF600ZJ steel for PV mounts was successfully exported to the EU for a solar project in Spain.
Overseas project: A 5.747 MW distributed project in Bangladesh used hot‑dip galvanised all‑carbon‑steel ground mounts.
New material: Angang Steel successfully trial‑produced AWP700, an ultra‑high‑strength corrosion‑resistant steel only 1.5 mm thick with a strength of 700 MPa.
🆚 Carbon Steel vs. Aluminium
| Aspect | Carbon Steel | Aluminium |
|---|---|---|
| Strength | Higher – Q355B yield ≥355 MPa | Lower – about 68‑69% of Q235B |
| Cost | Lower – approx. RMB 4,500‑6,000/tonne | Higher – 30‑40% more per kW |
| Weight | Heavier | Light – density ~1/3 of steel |
| Corrosion protection | Relies on coatings (but Zn‑Al‑Mg has greatly improved performance) | Natural oxide film, good corrosion resistance |
💎 Summary and Selection Recommendations
Large‑scale ground‑mount plants, high‑load applications: Carbon steel is usually the better choice because of its high strength and cost effectiveness.
Coastal, high‑salt, and other harsh environments: To guarantee a 25‑year service life, Zn‑Al‑Mg coated carbon steel (or another material with superior corrosion resistance) is recommended.
Inland, normal environments: Hot‑dip galvanised carbon steel meets requirements and offers the best cost‑performance ratio.
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