Solar Mounting Systems: Roof & Ground

When asking, “What goes into designing a home solar system?”,  some may be wondering about which solar panels we use. Although this is obviously important, the first design element to determine is the mounting location or structure; whether the panels will be mounted on the roof, ground or on a solar tracker. Traditionally, solar installations are mounted on a roof or on the ground. So for the purpose of this blog, we will focus on roof-mounted and ground-mounted systems.

Solar mounting or “racking”, is at the foundation of every solar system. Having the right kind of racking can make or break an installation, as this determines the stability of the overall system. In many cases it also affects the aesthetics,  as choosing the right racking system will give you the beautiful, low-profile system most homeowners desire.

Today, we are going to cover some of the different types of racking that you mainly see in the US, based on different roof types and ground mount applications. This blog is a part of a series of blogs coming where we will talk about other types of mounting options (solar trackers, carports, canopies, etc.), and the many ways they can be installed . Are you ready? Alright – let’s dive in!

RACKING FOR ROOF-MOUNTED SYSTEMS

Most home solar installations are done on sloped or “pitched” roofs.  There are many different options for mounting on a pitched roof. Here’s a breakdown of the most common options: railed, rail-less and shared-rail systems.

Railed Solar Mount

Historically, rail-mounted systems have been the most commonly installed solar racking systems. Rails are attached to an L-foot, that is mounted on top of a piece of metal flashing. This flashing is secured to the roof using a lag screw driven directly into the roof rafter. Both the lag screws and flashing are then sealed with waterproof caulking..  There are actually several techniques to install a properly waterproofed mounting system. We’ll cover that in another blog in this series.

By distributing the mounting across different rafters, the weight of the solar panels are equally distributed across the roof. Once the rails are mounted, the panels can be arranged in either portrait or landscape orientation and secured to the rails with specialty clamps, called mid and end clamps. Mid-clamps go between panels and end clamps are used on the ends of the rails. You probably guessed that one!

There are many manufacturers that specialize in rail-mounted systems. Some of the top industry names include SunPower Invisimount, IronRidge, and Snap N’ Rack.

Rail-less Solar Mount

Rail-less mounting systems are self-explanatory. Instead of the panels attaching to a rail, the frame of the module is attached directly to hardware that is connected to the roof itself. Though rail-less systems use the same amount of attachments as a rail-mounted system, removing the rails reduces shipping costs and shortens installation times. Whereas rails require the system to flow in a horizontal pattern, there is more flexibility in designing a system using rail-less mounting because there is no limitation to panel orientation. Brands such as Quick Mount PV, IronRidge, and Ecolibrium Solar are among a few manufacturers that offer rail-less solar mounting systems.

Shared-Rail System

In a typical rail-mounted system, if you have two rows of solar panels, there are 4 rails used to secure the panels to the roof (2 rails per row of panels). Shared-rail systems get rid of one rail and use clamps to connect the two rows of panels to one shared center rail. This approach means fewer penetrations into the roof are needed. Panels can also be positioned in any orientation using this system. Mounting manufacturers EcoFasten and Everest offer shared-rail mounted systems for both residential and commercial use.

Mounting for Flat Roofs

A “flat roof” generally means that the roof itself has little to no tilt at all (typically between 0 to 5 degrees). This is mostly seen on commercial buildings and factories, although some residential homes also have flat roofs (this is particularly true for triple deckers).

Solar mounting systems for flat roofs are mainly ballasted systems. Here’s how it works… A “foot” or tray-like apparatus is used as the base of the assembly. The panels are placed in the feet and then clamped into place. Small ballast blocks usually made of concrete hold the trays to the roof (reference photo above). The trays come pre-tilted, usually between 5 degrees and 15 degrees. The amount of ballast blocks needed depends on wind load requirements for that system and job site, which is determined during the design stage by an engineer. Depending on the type of ballast system, this method  usually requires fewer penetrations to the roof, if any at all. Some manufacturers of ballasted systems are UniRac, DynoRaxx, and Ecolibrium Solar.

RACKING FOR GROUND-MOUNTED SYSTEMS

The beautiful thing about a roof-mounted system is that you’re building your solar system on a pre-existing structure. But if you want to put your system on the ground or above a parking lot – you need to create the structure for the panels to sit! A ground-mounted system is usually placed in a field or an open area far from trees or tall structures.

Fixed Ground Mount

A fixed ground mount system is a stationary system, usually positioned for optimal solar access, with good southern orientation, at  the ideal pitch for the site. For example, here in Massachusetts, we are in the northern hemisphere with a latitude of about 42o. So for us, fixed mount system are oriented 180 degrees due south with a tilt between 30o-45o.  

When constructing a ground mount system, the first step is to determine the footing. There are different options: pour concrete, drive pipes 8 feet into the earth, helical piles, or even the Nuance System.  Each has its practical application, depending on location and the composition of the ground you are building on. We’ll discuss more about this topic in a future blog.

Once the footing is established, you build a frame, and from there, it is essentially the same as building a rail-mounted system.  Two rails usually support each panel, whether oriented in landscape or portrait. Sounds simple right? That’s why you see more and more huge solar farms springing up worldwide – there may even be one in your neighborhood.

Solar Trackers
A solar tracker helps to direct solar modules towards the sun by changing the orientation of the modules throughout the day to follow the sun’s path and maximize the amount of energy captured. Single-axis solar trackers rotate on one axis moving back and forward in a single direction. Dual-axis solar trackers continually face the sun by rotating on an axis that moves both vertically and horizontally to capture as much sunlight from any direction.

Utility-scale solar projects are opting more and more to install solar trackers because of the higher conversion efficiency and increased power production and efficiency. In addition, smaller residential and commercial applications have made use of the dual-axis trackers, especially in locations with high government feed-in tariffs.

Conclusion

As you can see, there are many variations when it comes to solar mounting options! In fact, we didn’t even touch on the growing trend of floating solar – yes, solar systems floating on water! The growing versatility of solar mounting options has made solar more viable in more diverse locations.

If you have any questions on these solar mounting methods, please feel free to give us a call at 617.564.3159.

References:

  1. https://www.solarpowerworldonline.com/2017/02/different-types-solar-mounting-systems-roofs/ “What are the different types of solar mounting systems for roofs?” ~ Solar Power World
  2. https://blog.pickmysolar.com/best-home-solar-mounting-racking-systems2018’s Best Home Solar Mounting Systems” ~ Pick My Solar
  3. https://www.solarpowerworldonline.com/2017/02/different-types-ground-mount-solar-racking-systems/What are the different types of ground-mount solar racking systems?” ~ Solar Power World
  4. https://news.energysage.com/solar-panel-mounts-unirac-ironridge-quick-mount-pv/ “Comparing Top Solar Panel Mounts and Racking Systems” ~ EnergySage
  5. https://www.solarpowerworldonline.com/2013/04/how-does-a-solar-tracker-work/ – “What is a solar tracker” ~ Solar Power World
  6. https://www.solarpowerworldonline.com/2017/08/earth-anchors-ground-mount-solar-profitable/
  7. https://www.solarpowerworldonline.com/2018/01/solar-trackers-find-new-home-roof/ – Solar Trackers for Rooftop Installations ~ Solar Power World
  8. https://www.nuanceenergy.com/solar-products/osprey-powerplatform – Osprey Power Platform ~ Nuance Energy
Bookmark and Share
  • Comments Off on Solar Mounting Systems: Roof & Ground

No comments so far.

No comments yet.

Sorry, the comment form is closed at this time.