Comparison and selection of solar photovoltaic mounting bracket steel and aluminum

1. Material strength

Generally, Q235B steel and aluminum alloy extruded profile 6063 T6 are used as supports. In terms of strength, 6063 T6 aluminum alloy is about 68% - 69% of Q235B steel, so steel is generally superior to aluminum alloy profile in strong wind area and large span.

2 deflection and deformation

The deflection deformation of the structure is related to the shape, size and elastic modulus of the profile (an inherent parameter of the material), but not directly related to the strength of the material.

Under the same conditions, the deformation of aluminum alloy profile is 2.9 times of that of steel, the weight is 35% of that of steel, and the cost is 3 times of that of steel. Therefore, steel is generally superior to aluminum alloy profile in strong wind area, large span, cost and other conditions.

3 corrosion protection

At present, the main anti-corrosion mode of the bracket is hot-dip galvanizing of 55-80 μ m steel and anodizing of 5-10 μ m aluminum alloy.

Aluminum alloy is in passivation zone under atmospheric environment, and its surface forms a dense oxide film, which prevents the surface of active aluminum from contacting with the surrounding atmosphere, so it has very good corrosion resistance, and the corrosion rate decreases with the extension of time.

Under normal conditions (C1-C4 environment), the thickness of 80 μ m galvanized steel can be guaranteed to be used for more than 20 years, but the corrosion rate is accelerated in high humidity industrial area, high salinity seashore or even temperate seawater. The amount of galvanized steel needs more than 100 μ m, and it needs regular maintenance every year.

Aluminum alloy is far superior to steel in corrosion protection.

4. Comparison of other aspects with respect to corrosion

1) Appearance:

There are many surface treatment methods for aluminum alloy profiles, such as anodizing, chemical polishing, fluorocarbon spraying, electrophoretic coating, etc. It has beautiful appearance and can adapt to all kinds of strong corrosive environment.

Steel is generally hot-dip galvanized, surface spraying, paint coating and other ways. Appearance is worse than aluminum alloy profile. It is also inferior to aluminum profile in corrosion protection.

2) Section diversity

The general processing methods of aluminum alloy profiles are extrusion, casting, bending, stamping, etc. Extrusion production is the current mainstream production mode. By opening the extrusion die, we can produce any cross-section profile, and the production speed is relatively fast.

Steel is generally used in rolling, casting, bending, stamping and other ways. At present, rolling is the main way to produce cold-formed steel. The section needs to be adjusted by the roller group, but generally the machine can only produce the same kind of products after finalization, and the size can be adjusted, but the section shape cannot be changed, such as C-section steel, Z-section steel and other sections. The rolling production mode is relatively fixed and the production speed is relatively fast.

5 recovery of materials

The maintenance cost of steel structure increases by 3% every year, while the support of aluminum structure hardly needs any maintenance, and the recovery rate of aluminum material is still 65% after 30 years, and the aluminum price is expected to increase by 3% every year. After 30 years, steel structure is basically a pile of scrap iron, with no recovery value.

6 comprehensive performance comparison

1) Aluminum alloy profiles are light in weight, beautiful in appearance and excellent in anti-corrosion performance. They are generally used in family roof power plants with requirements for load-bearing and strong corrosion environment.

2) Steel with high strength and small deflection under load is generally used in ordinary power plants or components with large stress.

3) In terms of cost: generally, the basic wind pressure is 0.6kn/m2, and the span is less than 2m. The cost of aluminum alloy support is 1.3-1.5 times of that of steel structure support. In the small span system (such as color steel roof), the cost difference between aluminum alloy support and steel structure support is relatively small, and aluminum alloy is much lighter than steel support in terms of weight, so it is very suitable for home roof power station.