design and function of a solar photovoltaic system. They provide the structural support needed to sustain solar panels at the optimum tilt, and can even affect the overall temperature of the system.
Based on the selection of the mounting structure, the cooling mechanism will be different. Ground mounted solar panels will have better air flow from both sides, therefore, they will cool off easier than roof mounted panels, and this difference will affect the overall temperature control of solar panels and their efficiency.
Furthermore, the decision on the most appropriate type of the mounting system will also affect the final cost of the project. The installation of the roof mounting may even imply modifications to your house structure that could increase upfront costs.
Moreover, depending on the mounting system that you use, efficiency of the solar system can increase or decrease, as ground mounted systems provide better tilt maneuverability than roof mounted panels, and therefore, affect the total power output that your solar system will provide throughout the year.
It is important to know which type of solar panel mounting system is the best one for you.
This article explains each available option, while at the same time describes the technical process that involves its construction. By knowing how the installation is done, you will be able to choose the option that better suits your needs and expectations.
Ground mounted solar systems
As the name implies, your solar system will be located on the ground.
The main advantage of ground mounted systems is that there is a wide range of options to choose from, depending on your location, your needs and the proposed design.
Ground mounted solar racking options you can choose from are:
#1 Foundation mounts
Foundation mounts are the most common ground mounted structures.
Their installation consists of preparing the land for excavation. Excavation is needed to put vertical pipes or mechanical tubing surrounded by a concrete foundation in place.
This installation requires the site assessment and geotechnical analysis of the soil to the determine whether it is strong enough to hold the mounted structure. Depending on the type of soil (crystalline bedrock, sedimentary rock, gravel, sand, etc.), the foundation pressure will differ.
So, the soil type determines whether concrete foundation, helical pile or ground screws are needed to anchor the solar system in place [1,2].
#2 Ballasted footing mounts
If the soil is not suitable for drilling or excavation, the best solution is to use a ballasted footing mount structure.
This mounting consists of a pre-cast concrete block anchored to the ground.
This structure is widely used in residential installations .
#3 Pole mounts
Represent a simple and cost-effective solution to install small solar systems.
Pole mounts are ideal for residential purposes.
The advantage of pole mounting is that there is no need for creating a complicated foundation or level the land (necessary step for ballasted mounts). Instead just a simple steel pole with a concrete anchor is placed on the ground. This simple structure provides in general sufficient support to solar panels. In some cases, due to the unsuitable soil type or extreme weather conditions, special adjustments are required.
Among the available pole mounted schemes, you will often find Side Pole Mounts. These mounts are widely used for lightning purposes and very small solar panel installations.
Other option are Top Pole Mounts, which are generally designed with heavy steel mounting sleeves, elevation pivots and strong backs that allows them to endure hard weather conditions and support big solar panels arrays.
These structures allow to change the tilt angle very easily and come with a good variability range of 15° to 60° .
#4 Multi-pole mounts
These structures are based on the same principle as pole mounted ones. The only difference is that all solar panels are laid in a single horizontal line (instead of being separated).
This means that the solar system can be horizontally extended as much as desired with additional vertical pipe supports.
The advantage over other ground mounting systems is that these structures allow the installation of bigger systems with great and simpler tilt variability, needing only one adjustment for all the panels, unlike pole mounted which require adjustment for each set of panels, and do not require as many soil perforations as other traditional systems.
These systems are also ideal for carports or for shading purposes .
There is a new option currently on the market. It is known as a SmartFlower Solar System. It was developed as a ground mounted system that has a form of a flower with solar cells instead of petals.
The system opens each morning when the sun rises and closes in the evening.
The advantage of this option is high efficiency of petals. According to the product parameters, a 2.5 kW SmartFlower structure equals a typical 4 kW ground mounted system. The increased output is because solar cells are equipped with a dual-axis tracking system that ensures the optimum tilt angle to obtain the maximum irradiance. The downside of this technology is its high cost [4,5].
Regarding the installation of SmartFlower, it is far more simpler and faster (2 hours) than typical ground mounted systems, because solar cells and the mounting structure are already pre-assembled.
The installation involves:
- The definition of the active area of the solar flower (typically a cube of 16 x 16 x 16 feet)
- Drilling of 4 ground screws deep into the ground
- Fixing of the anchor to the tower back
- Placing the mounting structure over the installed ground screws
- Connection to the wind guard structure and wiring.
Ground mounted solar system installation
To give you an idea of the installation process of a typical ground mounted system, here is a breakdown of the most important steps, particularly for a foundation mount type.
First, it is required to establish the design of the system:
- Solar system dimensioning: Sets of 3, 4 or even 5 rows of panels. Depends on weather conditions and the electrical design.
- Evaluation of the soil condition: If it is sedimentary rock, gravel, clay, etc. Then, deciding on the foundation type based on weather (wind and snow) conditions as well as size and weight of solar panels.
- Selection of the foundation: Helical piles or concrete piers. Perforation of the ground will be required.
- Selection of the mechanical tubing or pipe size and material: Aluminum, steel, etc.
Once design considerations are completed, the installation starts:
- Excavation begins to create enough space for the concrete foundations or to place the helical piles.
- The base of the mounting system is fixed to the grounding foundation with the use of bolts.
- Vertical mechanical tubing or pipes are placed and fixed to the base. Folded pre-assembled structures can also be placed.
- Installation of rails. Rails are attached to the structure.
- Installation of cross rails is an option that depends on the structural design considered for the system.
- Solar panels are adjusted into the rails with the use of middle and end clamps.
- Preparing all required components. Drilling, pencils, fall protection kit, chalk blocks, rails, clamps, bolts, screws and more.
- Determining the distance between the rails on the roof. According to the distance of pre-drilled holes in solar panels that you bought. Draw a reference line with the use of a chalk line.
- Checking in the guidelines of local authorities. Generally, these limits are related to the edges of the roof and will be necessary to take into account when setting the initial position of the rails and the panels.
- Finding rafters on the rooftop. Drilling a spot hole through the roof into the attic. After drilling and locating the position of the drill from the inside, the installer is able to adjust the center of the truss that will be the supporting spot for the rails.
- Mounting the flashings. After securing hole positions, the installer must mount the flashings (the supporting structures that will attach the panels to the roof). Bolts and caps are then used to connect these flashings to the rails.
- Mounting the racking. Rails are put in place. The installer also needs to make sure that they are lined up and are properly elevated with the help of the flashings.
- Wiring management clips and installation of grounding bolts. Grounding bolts are attached to the bare copper wire that goes to the grounding system of the house.
- Installing micro-inverters or power optimizers of each panel and attaching the wires to the management clips.
- Securing panels to the mounting system. Finally, the installer uses the clamps and T-bolts to make sure the panels are well-tight to the mounting system.
Now that we have covered the available ground mounting types and installation procedures we may proceed to the roof mounted option.
Roof mounted solar systems
Roof mounted solar panels are the most common selection for most households. Reasons for this vary but the main one is the cost.
Generally, roof mounted systems are less expensive than ground mounted systems, because the main structure needed to sustain the panels is the rooftop itself. This saves costs that otherwise would rise higher due to the aluminum or steel structures needed to support ground mounted panels.
Solar panel installation suitable for sloped roof
Most houses have a sloped roof design.
Therefore, the mounting structure needs to adjust solar panels to an inclined surface. In order to do so, manufacturers offer several options:
#1 Railed mounting system
The most common roof mounted structure of all. Consists of attaching a set of rails to the rooftop.
Each solar panel is then attached to the rails through a set of clamps.
The rails are secured to the rooftop by screws and bolts.
#2 Rail-less mounting system
This type of installation directly uses bolts and screws to secure each panel to the roof. Its advantage is that manufacturing and shipping costs are reduced, which makes the installation faster.
Solar panels can be placed in the way selected by installer, because they are not as limited in their positioning as they would be with the rails.
The main downside of the rail-less system is the learning curve of the installation. This requires installers to be experienced in performing rail-less mounting systems.
Furthermore, it is advisable to avoid the use of rail-less when the panels are to be installed on crooked or tile roofs. It is also important to know that rail-less systems imply more attachment points. At the end, this could end up with more holes in your roof .
However, market trends seems to be changing. Rail-less systems are becoming more attractive for investment purposes than the railed mounts–mainly because the long term savings of rail-less systems seem to be much higher than the rail mounted .
#3 Shared-rail mounting system
This type of mounting system works the same as the railed system. The difference lies in the number of rails needed to be installed.
While railed systems for two solar panels row use four rails in total, shared-rail systems use only three rails — by using two rails on the edges and one in the middle that shares the two rows.
Installation costs and time are reduced by using this technique, as one or two rails are no longer needed and neither are the mid and end clamps.
This system also implies less perforations to your roof .
Flat roofs are often found on commercial or utility buildings. But there are also many households with flat roofs that require different approach than sloped roofs.
The main mounting system used on flat roofs is known as the Flat Roof Ballasted Racking System.
This system consists of a previously assembled structure with a set of ballasted blocks that go to the bottom and act as the support for the system, while attaching panels and the mounting system by the use of clamps and clips.
Among the greatest advantages of this mounting type is fast and easy installation and no need (or if, very few) for perforations in the roof. It also offers some grade of flexibility to adjust the tilt typically between 5° and 15° [7,3].
Roof mounted solar system installation
Now that you have a good idea about the roof mounting systems options, it’s good to know how the installation is done.
The usual process begins with this set of steps that an installer needs to follow to install a typical railed mounting system:
We have introduced the most usual installation types and procedures of different mounting systems.
Now, the question that may arise is Which type is the best for you?
There are several parameters that underlie the selection of the mounting system and they differ according to every location. What would be the best design for one household, could be the least cost-effective option for another.
For instance, ground mounted systems tend to be more expensive than rooftop, but they could be the most suitable solution if your roof is not sufficiently strong to endure and support the weight of the panels in challenging weather conditions over the solar system’s lifetime.
In such case, the experience of your installer will be of the highest importance, as it is up to his professional judgement to evaluate local weather patterns and the soil type.
On the other hand, if your roof is a perfect fit and the consideration of a ground mounted system is too expensive or just annoying to deal with (due to excavation, loss of available space for recreation, etc.), then there is no problem at all with choosing a roof mounting system.
Consult with your installer the most feasible choice. Take into consideration that despite railed mounting systems are the most common installation, rail-less and shared rail are becoming a more economical and sometimes even technical option.