The role of photovoltaic brackets in photovoltaic systems is to support and fix photovoltaic modules to ensure that they can stably receive sunlight and convert it into electrical energy. At the same time, photovoltaic brackets can also adjust the angle and orientation of photovoltaic modules to improve energy conversion efficiency and protect the modules from damage by the external environment. These functions enable photovoltaic systems to operate more efficiently and reliably, providing people with clean and renewable energy.

The photovoltaic bracket foundation is an important part of the photovoltaic bracket system. It provides a solid support for the photovoltaic bracket to ensure that the photovoltaic modules operate safely and stably under various climatic conditions. The selection of photovoltaic bracket foundations needs to be determined according to the geological conditions, climatic conditions and engineering requirements of the installation site.

What is the photovoltaic bracket foundation?

The photovoltaic bracket independent foundation refers to a basic structure used in photovoltaic power generation systems to support photovoltaic brackets and solar panels, and bear the weight of photovoltaic brackets and solar panels as well as external loads such as wind and snow loads. Therefore, it needs to have sufficient bearing capacity and stability to ensure the safe operation of the photovoltaic power generation system.

The foundation forms commonly used by photovoltaic brackets include reinforced concrete independent foundation, reinforced concrete strip foundation, spiral steel pile foundation, reinforced concrete pile column foundation, rock anchor foundation, etc.

What is reinforced concrete independent foundation?

Reinforced concrete independent foundation is one of the earliest traditional photovoltaic bracket foundation forms, and it is also a foundation form with a wide range of applications. It is a reinforced concrete independent foundation set under the front and rear columns of the photovoltaic bracket, consisting of a foundation bottom plate and a foundation short column above the bottom plate.

The top of the short column is set with an embedded steel plate (or embedded bolt) to connect with the upper photovoltaic bracket, which requires a certain burial depth and a certain foundation bottom area; the foundation bottom plate is covered with soil, and the self-weight of the foundation and the gravity of the soil on the foundation are used to resist the upward pull caused by the environmental load, and the larger foundation bottom area is used to disperse the vertical load of the photovoltaic bracket downward, and the friction between the bottom surface of the foundation and the soil and the resistance between the side of the foundation and the soil are used to resist the horizontal load.

The advantages of reinforced concrete independent foundation are clear force transmission path, reliable force, wide application range, and no special construction machinery is required for construction. This foundation form has a strong ability to resist horizontal loads.

What is a reinforced concrete strip foundation?

A reinforced concrete strip foundation is a foundation beam set between the front and rear columns of a photovoltaic bracket, thereby moving the center of gravity of the foundation between the front and rear columns, increasing the anti-overturning arm of the foundation, and being able to resist the overturning moment of the photovoltaic bracket caused by wind loads only by the self-weight of the foundation; at the same time, because the strip foundation has a large contact area with the foundation soil.

A reinforced concrete strip foundation can be used when the bearing capacity of the surface soil of the site is low, and is suitable for areas with relatively flat sites and low groundwater levels. Since the cast-in-place reinforced concrete strip foundation can obtain sufficient resistance to horizontal loads through a large foundation bottom area, it does not require a large burial depth, generally a burial depth of 200~300mm, so the amount of earth excavation is greatly reduced.

This form of foundation, the reinforced concrete strip foundation, has better load resistance, does not require special construction machinery, and has a simple construction process.

What is a spiral steel pile foundation?

The spiral steel pile foundation, also known as the steel anchor, is an increasingly widely used photovoltaic support foundation. It uses hot-dip galvanized steel pipe piles with spiral blades under the front and rear columns of the photovoltaic support. The spiral blades can be large or small, continuous or intermittent, and the spiral blades and steel pipe piles are continuously welded. During the construction process, it can be screwed into the soil with professional machinery.

The upper part of the spiral steel pile foundation is exposed to the ground and connected to the upper support column by bolts. Its force mechanism is similar to that of the common screws in daily life. It is screwed into the soil with supporting machinery, and the side friction between the steel pipe pile side and the soil, especially the bite force between the spiral blade and the soil, resists the pull-out force and bears the vertical load, and uses the pile-soil interaction between the pile body, spiral blade and soil to resist the horizontal load.

The advantages of the spiral steel pile foundation are outstanding. It has a fast construction speed, does not require site leveling, and does not require earthwork excavation. A variety of forms can be selected according to the geological conditions of the photovoltaic field. It also has very good environmental performance, can protect the vegetation in the site to the maximum extent, has little impact on the environment, and is easy to restore to its original appearance.

The spiral steel pile is convenient for adjusting the upper bracket, and the bracket height can be adjusted according to the terrain. The galvanized layer on the surface of the pile body is corrosion-resistant, which can ensure that the spiral pile has considerable bearing capacity underground, so the spiral steel pile can be reused as needed.

What is a reinforced concrete pile foundation?

Reinforced concrete pile foundations are divided into cast-in-place reinforced concrete piles and prefabricated reinforced concrete piles.

The cast-in-place reinforced concrete pile uses a circular on-site cast-in-place short bridge with a diameter of about 300mm as the foundation for the rooting of the bracket. The length of the pile into the soil is about 2.0m, and it is exposed 300~500mm above the ground. The length of the pile into the soil is determined according to the mechanical properties of the soil layer. The top embedded steel plate or bolts are connected to the front and rear columns of the upper bracket.

The force mechanism of cast-in-place reinforced concrete piles is the same as that of reinforced concrete bored piles. The side friction between the pile side and the soil is used to resist the upward pull force generated by the bracket under the action of environmental loads, and the side friction between the pile side and the soil and the end force between the pile end and the bearing layer are used to jointly bear the downward load of the bracket.

Cast-in-place reinforced concrete piles are first drilled in the soil layer, then steel bars are inserted, and then concrete is poured into the hole. The advantages are material saving, low cost, and fast construction speed.

Prefabricated reinforced concrete square piles are usually prefabricated in factories, so the pile body is regular, the pile body quality is easy to guarantee, and the corrosion resistance is strong. Since prefabricated piles are generally hammered (or statically pressed) into the soil, their construction efficiency is high and the construction period is short.

In addition, because prefabricated piles are soil-squeezing piles, they have a compacting effect on the surrounding soil, thus having a strong pull-out resistance, which can effectively prevent the photovoltaic bracket foundation from being pulled out in strong winds.

What is a rock anchor foundation?

Steel anchor foundation is mostly used for harder soil layers, such as gravel and sand layers, bedrock, etc. The surface of the steel anchor is provided with blades or continuous spiral blades with a very small diameter. During construction, it is necessary to use machinery to pre-drill holes in the harder soil layer. The diameter of the hole is larger than the diameter of the steel anchor. After the steel anchor is inserted, cement slurry is poured, and the upper part of the steel anchor is connected to the support column. Steel anchor foundation is suitable for harder soil layers such as bedrock.

If a photovoltaic power station is to be built on a rock foundation (especially on a hillside rock surface), the rock anchor foundation will become the preferred foundation form. The rock anchor foundation has certain requirements for the rock foundation. The rock foundation needs to be moderately weathered rock or slightly weathered rock. Strongly weathered rock is not suitable for rock anchor foundation.

At the same time, it is also necessary that there should be no obvious joints in the rock foundation to prevent the rock from cracking along the joints during the construction process, thereby causing the rock anchor foundation to fail.

When conducting geotechnical engineering surveys for rock anchor foundations, the number of drill holes should be appropriately increased according to the specific situation to ensure that the rock formation information is comprehensive, detailed and reliable.