Installing photovoltaic (PV) panels on flat roofs is becoming increasingly popular, especially among homeowners and businesses. Selecting the right support structure is crucial for the efficiency and durability of a PV installation. This article explores how to choose an appropriate PV support structure for flat roofs, considering the various options available on the market and individual user needs.
Why Invest in Photovoltaics for a Flat Roof?
According to the 2023 report by the Renewable Energy Institute, Poland has become one of Europe’s leaders in solar energy development. In 2022, nearly 4.8 GW of new capacity was installed, placing Poland second in the EU in terms of PV market growth. By late 2023, the installed PV capacity in Poland was forecasted to reach 18 GW, with an annual increase of over 6 GW. Data from September 2024 confirmed these predictions, showing a total installed capacity of 19.9 GW, which accounted for 62% of the total capacity from renewable energy sources.
This rapid sector growth demonstrates the rising popularity and profitability of solar energy investments, particularly among businesses and homeowners. Thanks to technological advances, investors now have access to increasingly sophisticated solutions that enhance installation efficiency and reduce operating costs.
Installing PV panels on flat roofs makes full use of the available space, which is especially important for large commercial and industrial buildings. Support structures allow panels to be positioned at optimal angles and orientations relative to the sun, maximizing energy production.
Moreover, PV systems on flat roofs contribute to energy independence, shielding users from rising energy prices and stabilizing operating costs—particularly for businesses. Additionally, PV installations align with global sustainability trends, helping reduce CO₂ emissions and protect the environment.
Given these factors, investing in photovoltaics on a flat roof is both an economical and ecological solution that provides long-term benefits for investors and the environment. However, the key to a durable and efficient PV installation lies in selecting the right support structure.
Types of Support Structures for Flat Roof PV Installations
1. Ballasted Structures
Ballasted structures are among the most popular solutions for flat roofs, especially where roof penetration must be avoided. These systems have a simple design, relying on special frames weighted down by ballast (e.g., concrete blocks or metal weights). This provides stability and wind resistance without compromising the roof covering.
Installation Process:
The installation begins by preparing the roof surface. The frames are placed on special pads (depending on the roofing material) to prevent damage to the covering, such as a membrane or bitumen. The frames are spaced out and positioned at an optimal tilt angle, after which the ballast is added to secure the structure and prevent movement due to wind. The PV panels are mounted onto the frames using clamps that ensure stability even in harsh weather conditions.
Advantages of Ballasted Structures:
- No roof penetration—maintains roof waterproofing, critical for buildings with sensitive roof coverings.
- Ease of assembly and disassembly—ideal for installations that may need future expansion or reconfiguration.
- Versatility—suitable for various roof types, including PVC membranes, bitumen, and sheet metal.
Limitations:
Ballasted structures require adequate roof load-bearing capacity, as the additional weight can be significant. Therefore, a technical analysis of the building is essential before installation to confirm the roof can support the structure, panels, and ballast.
Use Cases:
Ballasted structures are well-suited for warehouses, office buildings, and other commercial properties with flat, large, unused roof areas. Their modular design allows customization to fit different installation sizes and investor needs.
2. Mechanically Fixed Structures
Mechanically fixed structures involve directly fastening the PV support frames to the roof structure using anchors, screws, or bolts. This method requires roof penetration but offers exceptional stability, making it ideal for areas with strong winds or heavy snow loads.
Installation Process:
The process begins with precise planning of the anchor points. The roof is drilled to attach brackets or supports that serve as the foundation for the structure. Proper sealing around the mounting points is crucial to prevent leaks and maintain roof waterproofing. The support frames are mounted onto the brackets, and the PV panels are installed at an optimal angle to maximize energy output.
Advantages of Mechanically Fixed Structures:
- Exceptional stability—highly resistant to strong winds and extreme weather conditions.
- Lighter design—since ballast is unnecessary, the overall roof load is reduced.
- Durability—solid mechanical attachment ensures the system’s longevity.
Limitations:
- Roof penetration—drilling into the roof carries a risk of structural damage and increased leakage potential. Proper sealing of mounting points is essential.
- Higher installation costs—the process is more time-consuming and requires precision, increasing labor costs.
- Limited flexibility—not all roofs are suitable for mechanical mounting, especially those with structural limitations.
Use Cases:
Mechanically fixed structures are ideal for industrial roofs and buildings in regions with challenging weather conditions. They are also a good option when a lighter system is required to avoid additional ballast.
3. Hybrid Structures
Hybrid structures combine features of ballasted and mechanically fixed systems, offering a balance between stability and minimal roof penetration. These systems use both ballast and point-based mechanical fastenings to provide optimal security while limiting the number of roof penetrations.
Installation Process:
The roof surface is prepared, and lightweight frames are positioned, with key points secured using special brackets for additional stability. The rest of the structure is stabilized using ballast, reducing the number of mechanical attachments. The PV panels are mounted onto the structure and positioned at an optimal tilt angle based on local conditions.
Advantages of Hybrid Structures:
- Stability and safety—combining mechanical fixing with ballast enhances resistance to extreme weather, such as strong winds and heavy snow.
- Minimal roof penetration—fewer drilled points reduce the risk of roof damage and leaks.
- Versatility—can be used on roofs with varying load capacities where fully ballasted or fully mechanical systems may not be sufficient.
- Even weight distribution—the structure and PV panels’ weight is evenly distributed, minimizing roof stress.
Limitations:
- Complex installation—requires precise planning and execution to integrate different stabilization methods into one system.
- Higher costs—due to the combination of two mounting technologies, hybrid systems can be more expensive to purchase and install.
Use Cases:
Hybrid structures are often chosen for large commercial buildings where stability and roof protection must be balanced. They are also ideal for roofs with uneven load-bearing capacities, requiring reduced point loads.
Factors Influencing the Choice of PV Structure for a Flat Roof
- Roof covering material: Different materials (e.g., bitumen, PVC membrane, sheet metal) require compatible mounting systems to ensure durability and waterproofing.
- Roof load-bearing capacity: The roof must support the additional weight of the PV system and ballast. A load-bearing assessment by a specialist is essential before installation.
- Weather conditions: Local factors, such as wind zones and snow loads, influence the choice of structure and panel tilt angle.
- Panel tilt angle and orientation: The optimal tilt angle in Poland is approximately 30°–35°, with a south-facing orientation maximizing energy efficiency.
Benefits of PV Installations on Flat Roofs
- Design flexibility: Flat roofs allow for adjustable panel positioning at the optimal angle and orientation.
- Efficient space use: Large flat roofs, especially on industrial or warehouse buildings, provide extensive unused space ideal for PV installations.
- Energy cost savings: A PV system can significantly reduce electricity bills and, in some cases, provide energy independence.
- Ease of maintenance: Flat roofs simplify access for system maintenance, cleaning, and monitoring.
Challenges of Installing PV Panels on Flat Roofs
- Roof load: Consideration of the added weight from the PV system and ballast is necessary.
- Water drainage: Poorly designed structures can impede rainwater flow, leading to water pooling.
- Shading: Even small obstructions, such as chimneys or vents, can cast shadows that reduce efficiency. Power optimizers can help minimize energy losses caused by shading.
Essential Features of a Flat Roof PV Structure
- Durability: The structure should be made of corrosion-resistant materials, such as aluminum or galvanized steel, to withstand harsh weather conditions.
- Tilt angle adjustment: The ability to adjust the panel tilt helps optimize energy production based on local conditions.
- Wind resistance: The structure should withstand high wind loads, and certified systems meeting durability standards are recommended.
- Ease of installation: Modular systems with well-designed components simplify and speed up installation, reducing labor costs.
Summary
Installing PV panels on flat roofs is an excellent solution for those seeking an efficient and flexible energy production system. The key to a successful installation lies in selecting the right PV structure that ensures stability, durability, and optimal system performance. Consulting experts and choosing proven solutions can help maximize the potential of a PV installation.
