Photovoltaic (PV) Mounting Systems: A Comprehensive Guide
With the widespread application of photovoltaic power generation, the importance of PV mounting systems as the “skeleton” supporting the entire power generation system has become increasingly prominent. It is not only the physical carrier of PV modules, but also directly relates to the safety and power generation efficiency of the power station during its 25‑year or even longer operating cycle.
What Is a Photovoltaic Mounting System?
A photovoltaic (PV) mounting system is a specialized structural framework designed to support, secure, and position PV modules at specific tilt angles within a solar power generation system. Its core function is to ensure that the PV modules operate safely and stably under complex and variable natural conditions—such as high winds, heavy snow, and seismic events—while reliably transferring all imposed loads to the underlying foundation structure.
PV mounting systems are widely used in ground‑mounted power stations, building rooftops (including trapezoidal metal sheet roofs, flat roofs, and tile roofs), agri‑PV / fishery‑PV complementary projects, mountainous terrain, and floating PV stations on water surfaces.
What Parts Does a Photovoltaic Mounting System Consist Of?
The composition of a complete PV mounting system varies by type and application scenario, but usually includes the following core components:
1. Columns (Uprights/Posts)
A vertical supporting member of a structural frame that transfers the superimposed loads from the superstructure down to the foundation. Common materials used include C‑section steel, H‑section steel (or H‑beams), square steel tubes, and round steel pipes.
2. Main Beams and Purlins (Rails/Guide Rails)
The transverse load‑bearing members of the supporting structure that are directly connected to the PV modules. The purlin (or rail) serves as the key structural component for supporting and securing the modules. Common materials used include C‑section steel and aluminium alloy.
3. Diagonal Braces (Diagonal Supports)
A supporting member used to enhance the structural stability of the framework and to resist horizontal loads such as wind and snow.
4. Connectors and Fasteners
Includes nodal connectors that join various structural components into an integrated framework, clamps (end clamps and intermediate clamps) that secure the PV modules to the purlins, as well as bolts, nuts, and washers. To prevent corrosion, fasteners are predominantly made of stainless steel or surface‑treated metal components.
5. Foundation
The structural part that secures the supporting framework to the ground or rooftop. Common types include independent concrete footings, strip footings, helical piles, press‑in piles, and anchor bolts.
What Are the Main Types of PV Mounting Systems?
PV mounting systems can be divided into two main categories according to whether they are capable of tracking the sun’s movement.
Fixed PV Mounting System
The PV array is installed at a fixed tilt angle and does not rotate to follow the sun’s position. It is characterized by a simple structure, relatively low cost, good stability, and is essentially maintenance‑free.
- Fixed tilt at optimal angle: The optimal tilt angle is calculated based on the latitude of the project site to maximize the annual average energy yield.
- Fixed tilt on pitched roof: The PV modules are installed directly flush with the sloping roof surface. This configuration is commonly used in residential distributed PV systems.
- Adjustable tilt fixed mounting system: The tilt angle of the mounting system can be manually adjusted according to the seasons to achieve higher power generation.
Tracking PV Mounting System
The mounting system is driven by a control system that enables the PV modules to track the sun’s trajectory in real time, maximizing the capture of solar radiation and thereby increasing power generation.
- Horizontal single‑axis tracker (HSAT): The PV modules rotate about a horizontal axis oriented north‑south, tracking the sun from east to west. This technology is mature, cost‑effective, and widely deployed.
- Tilted single‑axis tracker: Axis tilted relative to ground; higher energy gain than HSAT, but structurally more complex.
- Dual‑axis tracker (DAT): Equipped with two rotational axes, this system can fully track both the azimuth and altitude angles of the sun. It offers the highest power generation gain among all tracking systems, but also comes with the highest cost and technical requirements.
Special‑Type Mounting Systems
In addition, according to application scenarios, there are also special‑type mounting systems such as flexible mounts designed for complex terrain (supported by prestressed steel cables, featuring large span and high clearance, suitable for fishery‑solar complementary projects), and floating solar mounts for water surfaces.
How Does a Photovoltaic Mounting System Work?
The core function of a PV mounting system is to withstand and transfer loads. Its working mechanism can be summarized as follows: Over a service life of more than 25 years, it reliably resists various external forces from the environment and safely transfers these forces to the foundation structure, thereby ensuring that the PV modules consistently maintain the design‑specified orientation and structural integrity.
Typical load transfer path:
Environmental loads (wind, snow, seismic) → PV modules → Clamps / mounting clips → Purlins (rails) → Main beams / diagonal braces → Columns (uprights) → Foundation → Subgrade (bearing stratum)
Key design considerations include wind loads, snow loads, seismic actions, as well as the self‑weight of the PV modules and the mounting structure. For tracking systems, additional attention must be given to the reliability and stability of the drive and control systems.
How to Choose the Right PV Mounting System?
Selecting the appropriate PV mounting system requires a comprehensive evaluation of multiple factors:
1. Project Type and Site Conditions
Is it a ground‑mounted power plant, a rooftop distributed PV project, or a fishery‑solar complementary project? Is the terrain flat, hilly, or mountainous?
2. Environmental Loads
The basic wind pressure, basic snow pressure, and seismic fortification intensity at the project site are the key parameters that determine the strength and structural design of the mounting system.
3. Module Specifications and Layout
The dimensions, weight, and series/parallel configuration of the PV modules directly affect the span spacing and load‑bearing design of the mounting system.
4. Materials and Corrosion Protection Requirements
Based on the environmental corrosivity (e.g., coastal areas, industrial zones), select appropriate materials (such as aluminium alloy or carbon steel) and corrosion protection processes (such as hot‑dip galvanizing or zinc‑aluminium‑magnesium coating).
Common Materials and Surface Treatment Processes
Common Materials
Carbon steel: High strength, relatively low cost, and the mainstream choice for large‑scale ground‑mounted PV power plants.
Aluminium alloy: Lightweight, excellent corrosion resistance, and aesthetically pleasing. It is commonly used in rooftop projects with high requirements for load‑bearing capacity and corrosion protection.
Stainless steel: Primarily used for fasteners and special high‑corrosion environments.
Surface Treatment
Hot‑dip galvanizing (HDG): Steel components are immersed in molten zinc to form a thick, durable protective layer. It is currently the most widely used corrosion protection method and can meet the requirements of high‑corrosivity environments such as C5.
Zinc‑aluminium‑magnesium (ZAM) coating: A new type of high‑corrosion‑resistance coating with excellent self‑healing properties and superior anti‑corrosion performance.
Anodizing (for aluminium alloy): An anti‑corrosion process intrinsic to aluminium alloy itself.
Quality Inspection Key Points for PV Mounting Systems
When procuring and accepting PV mounting systems, the following aspects should be given priority attention:
1. Material certificates
Verify the material certificates for steel/aluminium alloy to ensure that the grade and thickness comply with the design requirements.
2. Dimensional accuracy
Check whether the length, hole spacing, and shape of columns, purlins, and connectors conform to the fabrication drawings.
3. Coating quality
Check whether the galvanized coating is uniform and smooth, and free from defects such as bare spots, zinc runs, and white rust. Also verify that the coating thickness meets the specified requirements (e.g., average 85 μm for hot‑dip galvanizing to achieve C5 corrosion resistance).
4. Structural strength
For large‑scale projects, on‑site pull‑out tests may be required, or bearing capacity verification shall be performed in accordance with the design drawings.
Frequently Asked Questions (FAQ)
What is a PV mounting system?
A PV mounting system is a dedicated structural system used to support and secure PV modules. It must possess the performance capabilities to resist wind, snow, seismic, and corrosion loads, ensuring the long‑term stable operation of the power plant.
What is the difference between a PV mounting system and a conventional steel structure support?
A PV mounting system is custom‑designed for specific PV module layouts and environmental loads. It must precisely match the module dimensions and installation tilt angle, while meeting weather durability requirements of over 25 years. Its design standards and load considerations are consequently more stringent and specialized than those of conventional structures.
Which types of projects require PV mounting systems?
Virtually all photovoltaic (PV) power plants require mounting systems. From large‑scale ground‑mounted power plants, commercial and industrial (C&I) rooftops, and residential PV systems, to special‑application scenarios such as agri‑PV (agriculture‑complementary), fishery‑solar complementary projects, and floating PV stations on water surfaces — all rely on PV mounting systems.
What are the components of a PV mounting system?
The main components include columns (uprights), main beams, purlins (guide rails), diagonal braces, connectors (nodal joints), module clamps, fasteners, and foundations (such as concrete footings, helical piles, etc.).
Which is better — a fixed mounting system or a tracking system?
It depends on project objectives. Fixed‑mounting systems feature low investment and high stability, making them suitable for projects with limited budgets or stable electricity tariffs. Tracking systems require higher upfront investment, yet they can significantly boost power generation output. They are ideal for large‑scale flat‑land power stations pursuing higher generation returns.
What materials should be chosen for PV mounting systems?
Carbon steel offers high strength and excellent cost‑effectiveness, making it the mainstream choice; aluminium alloy is lightweight and corrosion‑resistant, suitable for rooftop and similar applications. The specific selection should be determined comprehensively based on loading, environmental conditions, and economic factors.
Does a PV mounting system require corrosion protection?
Corrosion protection is essential. The 25‑year design service life in outdoor environments presents a significant challenge for corrosion resistance. The most commonly used method is hot‑dip galvanizing (HDG); alternatives include zinc‑aluminium‑magnesium (ZAM) coating or anodizing for aluminium alloy components.
How to determine the selection of a PV mounting system?
It cannot be determined solely by module power rating. A comprehensive assessment is required — taking into account the site’s geological and topographical conditions, wind/snow loads, module dimensions, array configuration, available installation space, cost budget, and applicable local building codes.
Can PV mounting systems be installed on rooftops?
Yes — and it is very widely applied. Dedicated mounting systems and waterproof connection solutions must be selected according to the roof type (flat, pitched, or trapezoidal metal sheet), and it is essential to ensure that the roof structure has sufficient load‑bearing capacity.
