Solar Panel Structure: Rooftop vs Ground Mount Solar
All solar panel structure arrays are mounted in a frame. An appropriate mounting structure contributes to the stability and performance of the photovoltaic (PV) modules. It ensures the correct tilt and direction of the panels, protecting the roof and/or the underlying landscape. This article covers the key types, materials, components and use cases of the solar mounting structures, for residential rooftop and ground mount solar plants.
What Is a Solar Panel Structure?
A solar panel structure or module mounting structure is the frame for fixing PV modules and attaching them to the roof or ground. It bears the weight of the modules and resists wind loads and other forces. Simply put, a solar module mounting structure is a mechanical connection between the PV modules and the building or ground where the solar panel is installed. A good mounting structure is optimised for a particular roof profile, soil type and module size, bearing capacity, and other factors.
Why Does the Mounting Structure Matter?
The Solar Panel Structures determines the ability of the whole solar panel system to resist various loads and the performance of the modules. A good solar module mounting structure will have a high wind-load resistance and allow the panels to face the sun at the best angle. The tilt and direction of the solar panel structure affect the amount of electricity produced by the PV modules.
The space between the rows of modules allows for the removal of rainwater and loosening of dirt and dust. An optimally designed structure provides good access to the modules for cleaning and maintenance. On a roof, it will evenly distribute the load on the building structure and protect it from water damage and the effects of the elements.
Types of Solar Panel Structures
Solar mounting structures can be divided into rooftop, ground mount and specialised structures for specific applications. Which type of solar panel structure to choose depends on the location of the solar plant, the area of the roof or the available land area, and the intended use of the solar power plant.
Rooftop Structures
The characteristics of rooftop solar systems are critical for selecting the solar module mounting structure for rooftop solar panels. The most common solution for concrete tile roofing is to use an elevated mounting frame with ballast. For metal sheet roofing, clamps are used, which are mounted on rails fixed on the profile of the metal sheets. For sloping tile roofs, special roof hooks are used. Using rooftop structures allows for using the existing buildings to gain the ability to produce electricity without additional land costs.
Ground Mount Structures
Ground mount solar structures are installed on large areas of land. They are used to install solar plants, solar farms, and commercial solar power plants. The frame of ground mount structures is usually made of steel or aluminium profiles and mounted on concrete foundations, driven piles or ground anchors. Ground mount solar structure can be optimised in terms of tilt and orientation to achieve the highest performance. Besides, they provide good access to the modules for cleaning and maintenance, and allow for future expansion of the solar power plant. The critical disadvantage of ground mount structures is the dependence on the availability of land for their installation.
Other Mounting Structures
When the available land or roof area is limited, alternative solar panel structures can be used: fixed-tilt frames, trackers, carports, elevated structures, pole mounts, floating mounts and facade mounts.
Materials Used in Mounting Structures
Hot-dip galvanized steel is the most commonly used material for large-scale solar mounting structures installations. This material is sturdy, dependable, and inexpensive, despite its weight. Coated steels like Galvalume and zinc-aluminum-magnesium alloys are more corrosion resistant.
Aluminum is approximately three times lighter than steel and inherently corrosion resistant, although it is more expensive and less robust. Additionally, it has a higher coefficient of thermal expansion. Stainless steel is commonly used for fasteners. The materials used in solar panel structures should be chosen based on a balance of strength, weight, cost, and corrosion resistance, taking into account the operating environment and estimated service life of 25 years or longer.
Key Components
A typical module mounting structure consists of the following components:
- Columns or posts: vertical elements that bear the load of the entire structure
- Rails or purlins: horizontal elements that hold the solar modules
- Rafters, braces: inclined and vertical stabilising elements
- Brackets: elements connecting the rails to the columns or to the roof
- Clamps: elements for attaching the modules to the rails
- Fasteners: bolts, nuts, and washers, usually galvanized
- Foundations and anchors: concrete foundations, piles, ground anchors, or roof anchors
Rooftop vs Ground-Mounted at a Glance
Here is a major difference between Rooftop vs Ground mounted at a glance.
| Factor | Rooftop | Ground mounted |
|---|---|---|
| Location | Existing roof | Open land |
| Foundation | Roof anchors, clamps or ballast | Footings, piles or screws |
| Space | Limited by roof area | Scalable with available land |
| Maintenance | Needs safe roof access | Easier, ground-level access |
| Typical use | Homes, offices, factories | Solar plants, farms, campuses |
How to Choose the Right Structure
When choosing a mounting structure for solar panels, the following factors should be considered:
- Roof type and load: different roof structures require different types of roof anchors and can bear different weights
- Wind speed: the higher the wind speed, the more challenges the structure will have to withstand
- Soil properties: the type of foundation is selected based on the properties of the soil
- Module size, tilt and orientation: the size and shape of the modules, as well as their optimal orientation, will affect the design of the structure
- Corrosion: coastal areas, industrial areas, and areas with high air humidity require extra protection of the mounting structure from the effects of the environment
- Project size: large-scale solar power plants will require a more complex design and engineering of the structures
It is a good idea to request structural calculations from solar panel roofer companies, not only cost estimates.
Installation: What to Keep in Mind
A competent installation of a solar panel structure begins with an assessment of the site and a structural analysis of the building’s roof (in the case of a rooftop structure). Based on this analysis, engineers select the optimal design of the structure, its anchoring or foundations, and the arrangement of modules taking into account the shadowing effects.
Then, the structure and modules are installed and adjusted: the modules are aligned, and all connections are made. And at last, a structural engineer inspect the installation quality and make final adjustments.
What Determines the Cost?
The cost of a solar panel structure depends on several factors at once: materials, structural design, roof or ground conditions, project size, wind load, foundation work, and installation. In large-scale commercial solar power plants, the cost of the mounting structure is about 10% of the total cost of the turnkey project, which is a relatively small share. When comparing prices, it is important to consider not only the price per kW but also the equipment and materials included in the project.
Residential vs Commercial Projects
Residential solar panel structures are usually relatively light: they are made of rails, clamps or ballasts and have a simple design that fits within the dimensions of one roof. Commercial solar mounting structures differ because they are installed on large-scale buildings such as warehouses or industrial halls.
The width of the spans, wind loads, and potential for roof reinforcement are taken into account when designing commercial solar mounting structures. Large scale commercial and industrial solar power projects require you to use custom structure, custom designs, custom engineering, and calculation of wind loads and roof reinforcement.
Frequently Asked Questions
Q1: How much does a solar panel structure cost?
Ans: The cost of a solar mounting structure varies by many factors such as material types, custom design, wind load analysis, foundation work, size of the projects, etc. Usually, the mounting structures are a small fraction of the total solar power plant cost.
Q2: How long does one last?
Ans: The service life of the solar panel structure largely depends on the quality of its manufacture and installation. A properly made structure will last as long as the solar panels themselves, that is, about 25 years or more.
Q3: Is rooftop or ground mounting better?
Ans: There is no global preference for rooftop or ground-mounted solar structures. Rooftop structures are advantageous in the presence of suitable roof areas, while ground-mounted structures are more suitable for large-scale solar power plants with a high capacity.
Q4: Which material is best?
Ans: The choice of the material depends on many factors: the location of the solar power plant, its size and design, wind load, and others. Galvanized steel provides good value for money for large-scale ground-mounted solar structures. Coated steel or aluminium is more advantageous in areas with a high risk of corrosion.
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