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Discover How to Choose The Right Solar Panel Mounts

Selecting the right mounting structure is vital for optimal solar system performance, be it for a roof, carport, or ground installation. Tailored to factors like local weather and building structure, these structures significantly impact solar project efficiency. 

Understanding the site is crucial—from building type to weather—as these factors directly influence solar system effectiveness. To ensure project success, meticulous consideration of the pv mounting structure is essential to seamlessly align with site conditions.

Factors Affecting The Choice of Mounting Structure

Solar Panel Orientation

The way solar panels are positioned – whether on a roof, carport, or the ground – plays an essential role in determining the best time for power generation. This is especially the case when considering the directions the solar panels face.

For example, in Johannesburg, South Africa, the average duration of power production during peak sunlight hours in winter is around 5.5 hours, stretching to about 6.2 hours in the summer. 

The direction in which the PV Solar panels are pointed also determines power generation times. As an example:

  • Panels facing East generate power from roughly 7:00 AM till 12:30 PM.
  • Panels facing North generate power from around 9:00 AM till 3:00 PM.
  • Panels facing West generate power from about 12:00 PM until 5:30 PM.
  • Panels oriented towards the South are generally not productive, or at minimum, generate minimal power due to the lack of sun exposure.

These times can vary based on your specific location’s conditions, so be sure to keep that in mind during your solar system installation.

 

Available Space

The available space directly influences the design and viability of a PV solar system. Measured in square meters, this space determines the number of solar panels, impacting the system’s capacity, expressed in Kilowatt Peak (kWp). In essence, the available area sets the limit for the system’s overall power output capacity.

 

Shading

Shading and available space strongly impact PV solar panel installation. Considering each panel array’s physical space and the gaps between rows is crucial to prevent shading. Shading, caused by elevation, tilt, or surrounding structures, significantly affects system performance, necessitating specific mounting solutions. 

For optimal power generation, panels must receive consistent sunlight throughout the day. Even partial shading, from trees, buildings, or other sources, can adversely impact performance, though less severely than total shading.

 

Solar Panel Angle

Solar panel tilt significantly affects power generation, determined by geographical latitude and panel angle. The preferred tilt aligns with the location’s latitude; for instance, Johannesburg at 26°12′16″S suggests around a 26-degree tilt. Optimal tilt varies monthly due to the changing sun position, impacting total power output. 

Simulating averages with software ensures effective design, this helps to estimate the expected total power generation capacity related to site conditions. 

Advisably, avoid a flat 0-degree tilt, opting for 5 to 10 degrees for self-cleaning and peak efficiency.

 

Structural Integrity of the Site

Roof integrity and load capacity are crucial for a PV solar project’s feasibility. These factors determine the type of mounting structures, project viability, and return on investment. Larger buildings, especially with metal or concrete roofs, may exceed load-bearing limits due to panel and support structure weight. Engineers must conduct a detailed evaluation to specify solutions based on actual conditions, determining project feasibility.

 

Location

The site’s location critically influences the wind load considerations for the PV solar panel’s mounting structure. As per SANS 10160:3 regulations, the mounting structure solutions must accommodate respective wind loadings.

Most importantly, the performance of the mounting structure should align with the wind map of South Africa. This wind map categorises the country into various wind zones, with wind speeds ranging from 26 metres per second up to 44 metres per second measured at gust wind levels.

 

Terrain

The terrain plays a crucial role in determining the performance and design of solar panel mounting structures. In South Africa, there are four terrain categories:

  • Terrain A: Open farmland adjacent to a body of water.
  • Terrain B: Open land with little vegetation and buildings, such as a small plot of land.
  • Terrain C: Area with regular vegetation and buildings, like suburban areas.
  • Terrain D: Areas where at least 15% is covered with buildings, and their average height exceeds 15 metres.

Each terrain type influences the mechanical strength required in the mounting structure solutions and the structure’s performance requirements. Therefore, understanding and factoring in the land type where the project is located is essential for successful project execution.

 

Height

The height of the site, especially for rooftop installations, necessitates varied mounting structure strengths due to elevation-related changes in wind load and environment. A first-floor roof system faces different conditions than a 40-meter-high rooftop setup, requiring greater strength to endure higher wind loads and different surroundings. Consider height a crucial factor in project planning, impacting the mounting structure’s requirements.

 

Surrounding Landscape

The project’s surroundings significantly impact mounting structure solutions for solar panels. While wind zones and terrain generally guide the requirements for mounting structure performance, unique landscapes like valleys or peaks may necessitate adjustments due to channelled winds. Areas with high-rise buildings exposed to greater winds may require stronger solutions than SANS stipulates. Project characteristics can reshape outcomes despite consistent terrain or wind zone, emphasizing the need for individual analysis based on varying landscapes and environmental conditions.

 

Heat

Heat can hinder solar panel performance, mainly due to installation factors, like the gap between the roof’s top sheet and the backside of the panels. Solutions designed for cooler regions (like Europe) may underperform in persistent heat, as seen in South Africa. 

Failing to adjust for hotter climates may place the mounting structure too close to the roof, raising panel temperature and reducing power generation. Prolonged heat, common in Africa, significantly impacts solar panel system performance.

 

Choosing a Mounting Structure: Points to Consider

Aluminium Temper and Tensile Strength

Aluminium temper refers to the treatment an aluminium alloy undergoes to achieve specific properties. There are five main temper designations, denoted as suffixes to the alloy identifier, with ‘T’ indicating thermally treated aluminium. 

Tensile strength in aluminium is determined through a process called “ageing,” involving additional toughening at specific temperatures and times in an oven. 

Tensile strengths range from T0-T6:

  • T0 – extruded immediately after shaping 
  • T4 – has a medium to low tensile strength but is suitable for shaping without surface damage. T4 aluminium naturally gains strength after fabrication, achieving higher tensile strength requires a process known as “ageing” in a controlled environment.
  • T5 – medium strength, 25-35% stronger than T4
  • T6  – highest strength, 25%-35% stronger than T5

 

Aluminium Alloys

An aluminium alloy is a mixture where aluminium is the main metal combined with elements like copper, magnesium, manganese, silicon, tin, nickel, and zinc. To create aluminium alloys, aluminium is melted, and the other elements are added, forming a uniform solid solution. These alloys exhibit low density, high electrical and thermal conductivity, and corrosion resistance in specific environments. 

The chemical composition of the alloy influences its tensile strength, and each aluminium product should indicate the type of alloy used in its chemical makeup.

 

Mounting Structure Metal Types

Metal finishes in mounting structure aluminium can fall under a few types:

  • Anodized aluminium: Treated by an electrochemical process for a decorative, durable, corrosion-resistant finish
  • Mill finish aluminium: Unpolished and untreated, a raw finish that is a better conductor than anodized versions
  • Powder-coated aluminium: Treated with a powder coating made from polyester or epoxy resin, providing a coloured finish

 

Comparing Aluminium Rail Parts

When comparing two aluminium rails as part of mounting structure solutions, it is essential to start with the price per running meter, then assess the actual rate per running meter (considering variations in length and ensuring disclosure of the total cost rather than just the overall price per meter), and finally, consider the weight per running meter. Heavier rails per meter generally indicate more material and tensile strength (depending on the shape and form). 

Additionally, differences in tensile strength, especially between T6 and T5 rails, can lead to varying mechanical performance, typically differing by 25-35% based on shape and size.

 

Bracket Fixing Considerations

When comparing mounting structures, ensure the number of fixing brackets and components per running meter is similar, regardless of rail tensile strength. Evaluate the tensile strength of each bracket and component, noting that lower T5 strength may require more components for equivalent performance. Comparisons between T5 and T6 should consider that many Asian imports are T5, exhibiting lower performance and mechanical strength than T6 counterparts.

 

Material Compatibility and Fixing Solutions

Another crucial consideration is the spacing between brackets and the fasteners used. In some South African imports, a part like the bolt or screw is made of stainless steel, while the complementary part, typically the nut, is machined aluminium. This configuration, where one material is harder than the other, can lead to difficulties during installation, potentially causing damage to the thread and risking failure at the connection point. 

Additionally, complex fasteners not readily available in the local market limit substitution options, unlike standard, locally available fixing solutions that offer more flexibility and fewer constraints for installers on site.

 

Imported Mounting Structures

While there’s a common misconception that solutions designed in countries like Europe are inherently of superior quality, the key factor lies in the compatibility of a solution with locale-specific conditions. Installing a solar system on a roof involves integrating it into the existing roof, which has technical characteristics tied to the substructure. 

For example, European roofs, designed to withstand snow loads, have larger and closer-together substructures, like beams and purlins, ensuring sturdiness. However, South Africa’s metal roof sheeting is typically thinner (0.4mm to 0.5mm) than Europe’s average (approximately 1.5mm), indicating that solutions for different weather conditions may be based on a stronger building substructure and a thicker roof surface than what’s standard in South Africa. 

 

Rail Splicing

Another aspect to consider is the splicing of rails, involving connections to extend their length. The supporting brackets at the splice points should be closer together compared to the regular spacing when the rail runs in full length. Bracket spacing varies for different types and sizes of rails based on factors related to mechanical and tensile support and strength.

 

Bimetallic Corrosion

It’s crucial to consider bimetallic corrosion, also known as galvanic corrosion, which occurs when two different metals contact each other in a corrosive electrolyte like moisture and oxygen. In this process, one metal becomes an anode, corroding faster, while the other becomes a cathode, protected from corrosion. The most severe corrosion happens at the joint between the two metals, and the rate depends on the electrical potential difference and electrolyte conductivity. For mounting structures on roofs, where stainless steel and aluminium are commonly used to minimize corrosion, caution is needed. Some non-expert companies offer galvanized rails and components, accelerating corrosion between galvanized material and aluminium, making them unsuitable for roof applications, especially when metal roof sheeting is used.

 

Railed vs. Rail-less Mounting Structures

When choosing between railed and rail-less mounting structures, it’s crucial for installers and customers to consider the specific requirements. Railed solutions support panels with a full-width rail, while rail-less solutions use four points within the supporting frame. 

Non-experts should note that installing panels without rails requires the roof substructure and sheeting to meet load-bearing parameters, preventing excessive deflection. This solution is suitable for areas with strong roofs that can handle loads without deflecting. In South Africa, where roofs are designed for small wind loads, a structural engineer should assess the site for the feasibility of a rail-less solution to avoid potential failure and substandard performance. Alignment with values related to longevity and mechanical performance is essential for determining the best option based on site conditions.

 

Considerations Beyond Hardware Costs

Another significant error installers and end customers make is solely comparing hardware costs when evaluating mounting structures. This approach falls short, particularly in larger projects, where the overall project cost involves various elements beyond material expenses:

  1. Availability of the product: This is linked to the standing time on-site, and potential penalties may apply if the project has timeline commitments.
  2. Transportation cost: Some solutions differ in overall size, impacting the cost of transporting products.
  3. Installation time on-site: The actual time required for installing the solution is a critical factor
  4. Versatility of the solutions: This refers to how easily the same solution can adapt to obstacles or changes on-site without compromising the final result and performance. Using a minimum number of components for various solutions is also crucial.
  5. Flexibility of the mounting solution: Accessibility to local fixing components is essential. If specific components are only available from specific suppliers and not freely accessible in the local market, it can lead to complications and cost impacts when site conditions change or the supply is insufficient.
  6. Ability to have standard components for non-standard installations: Many imported solutions are designed for only 2 or 3 roof types, while the South African market has close to 17 roof types in use. The ability to accommodate various roof types is crucial for successful installations.

 

Conclusion

Selecting the appropriate mounting structure for a solar installation is a critical decision that involves a thorough understanding of various factors. From the orientation and available space to structural integrity, location-specific conditions significantly influence the effectiveness of a solar system. Beyond hardware costs, considerations like material compatibility, bimetallic corrosion, and the distinction between railed and rail-less structures play crucial roles. Installers and end customers must look beyond the price tag, considering factors such as product availability, transportation costs, and installation time. 

By aligning the mounting structure with site conditions and addressing these comprehensive considerations, one can ensure the success, longevity, and optimal performance of a solar project. Always consult with industry experts for a well-informed decision and a solar solution that stands the test of time.

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