development and design 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 panels. Actually, depending on the selection of the mounting structure, the cooling system will be different (ground mounted will have a bigger flow of air mass on the backside, and therefore a better cooling system than roof mounted), and such difference will affect the temperature control of the solar panels and their efficiency.
Furthermore, the decision on the most appropriate type of the mounting system will also affect the overall costs of the project. The installation of one type may even imply modifications to your house structure that could increase the 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 can provide throughout the year.
It is important to know which type of mounting is the best for you. Here we will explain each option that is available, while at the same time explaining the technical procedure that involves their construction and delivery of the total system. By knowing how the installation is done, you will be able to choose the option that better suits your needs and desires.
Ground mounted solar systems
As the name implies, this structure is located on the ground. The main advantage of ground mounted systems is that there is a wide range of possibilities to choose from, depending on the site location, your needs and the design of the installer.
Here we will discuss each of these possibilities:
#1 Foundation mounts
Foundation mounts are the most usual ground mounted structures. Their installation consists of preparing the land for excavation. Excavation is needed to put in place vertical pipes or mechanical tubing surrounded by a concrete foundation.
This installation requires the site assessment and geotechnical analysis of the soil to the determine whether the soil 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 type of the soil determines if 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 an evenly graded surface. This structure is widely used in residential installations .
#3 Pole mounts
Represent a simple and cost-effective solution to install small solar systems.
It is ideal for residential purposes.
The advantage of pole mounting is that there is no need for creating a complicated foundation or leveling the land for ballasted purposes. Instead just a simple unbending steel pole with a concrete anchor is placed. This structure is sufficient to provide a good structural strength. Although in some cases, due to the soil type or 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 is 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 sustain 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. 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 to install bigger systems with great and simpler tilt variability (only one adjustment for all the panels, unlike pole mounted which require adjustment for each set of panels) and do not require as many 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 the 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 when sunset comes.
The advantage of this option is high efficiency of petals. According to the product parameters, a 2.5kW SmartFlower structure equals a typical 4kW 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 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 procedure of the 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 the 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 the 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 the 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 between pre-drilled holes in the panels that you bought. Draw a reference line with the use of a chalk line.
- Checking of the requirement 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 by making sure that they are lined up and that they 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
The roof mounted option is the most common and usual selection for most households. The reasons for this are varied but the main one is the cost.
Generally, roof mounted systems are less expensive than a ground mounted system, because the main structure needed to sustain the panels is the rooftop itself. This fact saves costs that otherwise need to be covered by aluminum or steel structures.
Among the roof mounting type is also a set of possible options how to install the panels. They can be separated into two main groups: Sloped Roof and Flat 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 into 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 the panels are not 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 .
The trend on the market seems to be changing. Rail-less systems are more attractive for investment purposes than railed mounted. Mainly because the savings of rail-less systems seem to be much higher in the upcoming years 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 to be installed.
While in the railed systems for two solar panels row it is necessary to install 4 rails, but in the shared-rail it is only necessary to install 3 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. It 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 from the sloped roof.
The main mounting system used in these cases 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 overall system, while attaching panels and the mounting system by the use of clamps and clips.
Among the greatest advantages of this mounting type is the fast and easy installation procedure and particularly that there is no need (or in any case, 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, you must also know what the process of installation will be like. For such purpose we have developed a set of steps that the installer must follow to carry on the installation of a typical railed mounted 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 a 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 optimal solution if your roof design is not sufficiently strong to endure and support the weight of the panels in the hard 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 sloped or flat 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 better economical and sometimes even technical option.