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The Importance Of Photovoltaic Support Bracket’s Selection Oct 23, 2018

First, the type of photovoltaic bracket

1, according to material classification

According to the materials used in the main force-bearing members of the photovoltaic support, it can be divided into aluminum alloy brackets, steel brackets and non-metal brackets, among which non-metal brackets are used less, and aluminum alloy brackets and steel brackets have their own characteristics.

 

2, according to the installation method

 

Second, the introduction of fixed photovoltaic bracket

The photovoltaic array does not rotate with changes in the angle of incidence of the sun, receiving solar radiation in a fixed manner. According to the inclination setting, it can be divided into: optimal inclination fixed type, inclined roof fixed type and inclined angle adjustable fixed type.

 

1, the best tilt fixed

Firstly, the best installation angle of the local area is calculated, and then all the arrays are fixedly installed with the inclination angle, and are currently widely used in flat roof roof power stations and ground power stations.

 

1) Flat roofing - concrete foundation bracket

The flat roof concrete foundation support is the most commonly used installation form in the current flat roof power station. According to the basic form, it can be divided into a strip foundation and an independent foundation. The connection between the support column and the foundation can be connected by anchor bolts or directly supported. The column is embedded in the concrete foundation.

 

Advantages: good wind resistance, high reliability, and does not damage the waterproof structure of the roof.

Disadvantages: It is necessary to make a concrete foundation first and maintain sufficient strength to carry out subsequent bracket installation, and the construction period is longer.

2) Flat roofing - concrete ballast bracket

 

Advantages: The construction method of the concrete ballast bracket is simple, and the bracket can be installed at the same time when the weight is made, saving construction time.

Disadvantages: The concrete ballast support has relatively poor wind resistance. When designing the weight of the weight, it is necessary to fully consider the local maximum wind power.

3) Ground power station - concrete foundation bracket

There are various kinds of concrete foundation supports for ground power stations. According to the geological conditions of unused projects, the corresponding installation methods can be selected. The following mainly introduces the most common types of cast-in-place reinforced concrete foundations, independent and strip concrete foundations, and precast concrete hollow column foundations. Concrete foundation installation form.

?? Cast-in-place reinforced concrete foundation

According to different basic forms, the cast-in-place reinforced concrete foundation can be divided into cast-in-place concrete piles and cast anchors.

 

Advantages: The cast-in-place reinforced concrete foundation has less earthwork, less concrete reinforcement, lower cost and faster construction speed.

Disadvantages: The construction of cast-in-place reinforced concrete foundation is subject to environmental factors such as seasons and weather, and the construction requirements are high. Once it is completed, it cannot be adjusted.

Independent and strip concrete foundation

 

Advantages: The independent and strip concrete foundation adopts the reinforcement extension foundation, the construction method is simple, the geological adaptability is strong, and the foundation embedding depth can be relatively shallow.

Disadvantages: The independent and strip-shaped concrete foundation engineering has a large amount of labor, requires a lot of labor, excavation and backfilling of the earth, long construction period, and great damage to the environment.

Precast concrete hollow column foundation

The precast concrete hollow column foundation is widely used in power plants with poor geological conditions such as water-light complementary power stations and tidal flat power stations. At the same time, due to the basic height advantage, it is also used more in mountain power stations and agricultural light complementary power stations.

 

4) Ground power station - metal pile bracket

Metal pile supports are also widely used in ground power stations, and can be mainly divided into spiral pile foundation supports and impact pile foundation supports.

Screw pile foundation bracket

The screw pile bracket can be divided into a flanged screw pile bracket and a flangeless screw pile bracket according to whether it has a flange or not; according to the shape of the cotyledon, it can be divided into a narrow-leaf continuous type screw pile bracket and a wide-leaf space type spiral pile bracket.

 

Screw piles with flanges can be used for single-column or double-column installations, while screw piles without flanges are generally only used for two-column installations.

 

The pull-out resistance of the wide-leaf-spaced screw pile bracket is better than that of the narrow-leaf continuous screw pile bracket. The wide-leaf-spaced spiral pile bracket should be given priority in the windy areas.

Impact pile foundation bracket

The impact pile foundation bracket, also called the metal fiber rod foundation bracket, mainly uses the pile driver to directly drive the C-shaped steel, the H-shaped steel or other structural steel into the ground. This installation method is very simple, but the pull-out performance is poor.

 

Advantages: For the metal pile foundation, the pile driver is used to drive the steel pile into the soil without excavating the ground, which is more environmentally friendly; it is not subject to seasonal temperature restrictions, and can be implemented under various climatic conditions including northern winter; the construction is quick and convenient. The construction period is greatly shortened, and the migration and recovery can be facilitated; the foundation in the piling process is easy to adjust the height.

Disadvantages: Piling is difficult in hard soil areas; piling is easy to break in piling with more gravel; corrosion resistance is poor in saline-alkali areas.

2, inclined roof fixed

Considering that the load-bearing capacity of the inclined roof is generally poor, most of the components on the inclined roof are directly tiled, and the azimuth and inclination of the components are generally consistent with the roof. According to the different sloping roofs, it can be divided into tile roof installation system and light steel roof installation system.

1) Tile roof installation system

The tile roof installation system is mainly composed of connecting members such as hooks, guide rails, pressure blocks and bolts.

 

2) Light steel roof installation system

The light steel roof, also called the color steel tile roof, is mainly used in industrial plants and warehouses. According to the form of color steel tile, it can be divided into angular relaxation light steel roof, upright seam steel roof and ladder light steel roof.

 

The angle-relaxed light steel roof and the upright seam-type light steel roof are mainly fixed to the roof by means of a clamp as a connecting piece, and the ladder-type light steel roof requires a self-tapping bolt to fix the connecting piece to the roof.

Regardless of the type of roofing, it is necessary to carry out on-site measurements of "angle relaxation", "erect side" and "trapezoidal" dimensions when selecting connectors, to ensure that the joints and the roof are matched, and that the ladder-type light steel roof brackets are to be installed. Good waterproof measures to avoid water leakage at the bolt hole.

3, fixed tilt angle adjustable

The fixed tilt angle adjustment refers to the turning point of the sun incident angle change, periodically adjusts the fixed bracket tilt angle, increases the direct absorption of sunlight, and increases the power generation amount when the cost is slightly increased.

 

Third, tracking type photovoltaic bracket

The tracking type photovoltaic support moves the photovoltaic array with the change of the incident angle of the sun through electromechanical or hydraulic devices, so that the sunlight is directly directed to the component panel, thereby improving the power generation capability of the photovoltaic array. According to the number of tracking axes, it can be divided into: single-axis tracking system and dual-axis tracking system.

 

1. Flat single axis tracking system

The photovoltaic array can track the sun in an east-west direction with a horizontal axis, thereby obtaining a large amount of power generation, which is widely used in low latitude regions. According to the north-south direction, there can be divided into standard flat single-axis tracking type and inclined flat single-axis tracking type.

 

2, oblique single axis tracking system

The tracking axis rotates in the east-west direction while setting a certain inclination angle to the south, and the sun azimuth angle is rotated around the tilt axis to obtain a larger power generation amount, which is suitable for use in a higher latitude area.

 

3, dual axis tracking system

The two axes are rotated (vertical axis, horizontal axis) to track the sun's rays in real time to ensure that the sun's rays are perpendicular to the panel surface at each moment, so as to obtain the maximum power generation, which is suitable for use in various latitudes.

 

4. Comparison of several bracket operation modes

 

Comparison of photovoltaic bracket steel and aluminum and selection of material strength

The bracket is generally made of Q235B steel and aluminum alloy extruded profile 6063 T6. In terms of strength, 6063 T6 aluminum alloy is about 68%-69% of Q235 B steel, so the steel is generally superior to aluminum alloy in strong wind region and large span. Profile.

Deflection deformation

The deflection of the structure is related to the shape and size of the profile, the modulus of elasticity (a parameter inherent to the material), and is not directly related to the strength of the material.

Under the same conditions, the deformation of the aluminum alloy profile is 2.9 times that of the steel, and the weight is 35% of the steel. The cost is three times that of the steel under the same weight. Therefore, in general, the strong steel area, the span is relatively large, and the cost is better than the aluminum alloy profile.

Anti-corrosion

At present, the main anti-corrosion steel of the bracket is hot-dip galvanized 55-80μm, and the aluminum alloy is anodized 5-10μm.

In the atmosphere, the aluminum alloy is in the passivation zone, and a dense oxide film is formed on the surface, which hinders the contact of the surface of the active aluminum substrate with the surrounding atmosphere, so it has very good corrosion resistance and the corrosion rate increases with time. And decrease.

Steel under normal conditions (C1-C4 environment), 80μm galvanized thickness can guarantee the use of more than 20 years, but in high humidity industrial area or high salinity beach or even temperate sea water, the corrosion rate is faster, the galvanizing amount needs 100μm, Above and requires regular maintenance every year.

Aluminum is far superior to steel in terms of corrosion protection.

Other aspects compared to anti-corrosion

(1) Appearance:

Aluminum alloy profiles are available in a variety of surface treatments such as anodizing, chemical polishing, fluorocarbon coating, and electrophoretic painting. The appearance is beautiful and can adapt to a variety of environments with strong corrosive effects.

Steel is generally hot dip galvanized, surface sprayed, painted and coated. The appearance is worse than the aluminum alloy profile. It is also inferior to aluminum profiles in terms of corrosion protection.

(2) Cross section diversity

Aluminum alloy profiles are generally processed by extrusion, casting, bending, and stamping. Extrusion production is the current mainstream production method. By opening the extrusion die, any arbitrary section profile can be produced, and the production speed is relatively fast.

Steel is generally rolled, cast, bent, stamped, etc. At present, roll pressing is the mainstream production method for producing cold-formed steel. The cross-section needs to be adjusted by the roller set, but the general machine can only produce similar products after the shaping, the size is adjusted, and the cross-sectional shape can not be changed, such as C-section steel, Z-shaped steel and other sections. The rolling production method is relatively fixed and the production speed is relatively fast.

Material recycling

The maintenance cost of the steel structure increases by 3% per year, while the aluminum structure supports almost no maintenance and maintenance, and the aluminum material still has a 65% recovery rate after 30 years, and the aluminum price is expected to increase by 3% every year. The steel structure is After 30 years, it is basically a pile of scrap iron, no recovery value.

Comprehensive performance comparison

(1) The aluminum alloy profile is light in weight, beautiful in appearance and excellent in corrosion resistance. It is generally used in home roof power stations and strong corrosive environments where load bearing is required.

(2) The steel has high strength and small deflection deformation when subjected to load, and is generally used for ordinary power stations or for components with relatively large forces.

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