PV Rack Innovations

Intermediate

Inside this Article

Eric Hansen of True South Solar
Eric Hansen of True South Solar fastens PV modules to a PV rack that includes a channel for keeping wiring tidy.
Unirac’s (E)volution Rack
Unirac’s new (E)volution rack, with I-beam rail and bonding-integrated mounting hardware, was designed to increase installation speed.
SnapNrack pitched-roof mounting system.
SnapNrack pitched-roof mounting systems have integrated wire management channels and flashing-integrated roof mounts. End clips fit under the module, so rails can be flush with the end of the module.
SnapNrack pitched-roof mounting system.
SnapNrack pitched-roof mounting systems have integrated wire management channels and flashing-integrated roof mounts. End clips fit under the module, so rails can be flush with the end of the module.
Schletter Gator mount.
Schletter’s Gator mount for composition roofs uses a flashing-integrated mounting block, which attaches via a single hanger bolt to the roof structure and the Gator Clamp solar rail attachment.
Quick Mount PV’s Quick Hook tile mount.
Quick Mount PV’s new Quick Hook tile mount is the first commercially available flashed tile hook mount.
Silicon Energy’s Cascade modules.
Silicon Energy’s Cascade modules are framed only along the long edges and attach directly to mounting feet rather than rails.
Zep Solar’s railless mounting system.
Zep Solar’s railless mounting system uses grooved modules and proprietary attachments.
Frameless Lumos Solar modules.
Frameless Lumos Solar modules are mounted on rails via hardware attached directly through the module, rather than to a metal module frame.
PanelClaw Polar Bear
PanelClaw’s Polar Bear is a ballasted low-slope roof solution that incorporates recycled rubber pads under the ballast trays.
Ecolibrium Solar’s Ecofoot2
Ecolibrium Solar’s Ecofoot2 is a ballasted system made of recycled plastic.
Renusol CS60
Renusol’s CS60 heavy-duty plastic ballast trays don’t need equipment grounding.
SunLink Core RMS
SunLink Core RMS is a low-slope roof rack solution that can combine mechanical attachment points with ballast weight.
DPW Solar’s top-of-pole mounts.
DPW Solar’s top-of-pole mounts, set at a low tilt for high summer production.
DPW Solar’s Multi-Pole mount.
DPW Solar’s Multi-Pole mount can be installed at tilts up to 55° and heights up to 14 feet above the ground.
Solar awning structure.
Silicon Energy Cascade modules incorporated in an awning structure.
Engineered carport canopy.
Left: Lumos Solar’s LSX engineered carport canopy.
Terrafix Solarpark earth screw
The Terrafix Solarpark earth screw is a fast foundation solution for large ground-mounted arrays. Using no concrete, they are easy to both install and remove.
SunLink’s ballasted ground-mounted rack.
Because it requires no ground penetration, SunLink’s ballasted ground-mounted rack is ideal for use where soil cannot be disturbed, such as at brownfield or landfill sites.
Eric Hansen of True South Solar
Unirac’s (E)volution Rack
SnapNrack pitched-roof mounting system.
SnapNrack pitched-roof mounting system.
Schletter Gator mount.
Quick Mount PV’s Quick Hook tile mount.
Silicon Energy’s Cascade modules.
Zep Solar’s railless mounting system.
Frameless Lumos Solar modules.
PanelClaw Polar Bear
Ecolibrium Solar’s Ecofoot2
Renusol CS60
SunLink Core RMS
DPW Solar’s top-of-pole mounts.
DPW Solar’s Multi-Pole mount.
Solar awning structure.
Engineered carport canopy.
Terrafix Solarpark earth screw
SunLink’s ballasted ground-mounted rack.

Whether roof-, ground-, or pole-mounted, PV rack and its associated parts, such as structural attachments, grounding, and wire management systems, are available in hundreds of styles and varieties. There has been a recent explosion of companies that offer PV racks.

Just as when you’re selecting PV modules or inverters, cost shouldn’t be the primary factor in choosing PV racks. Company sustainability and longevity, product warranties, aesthetics, the level of customer and engineering support, and Code-compliance—all of these factors should play a role in deciding what rack system to rely on. 

No two solar sites are precisely alike; both the built and natural environments affect an installation’s specifics. A thorough site survey quantifies these factors, and a quality system requires tailoring the design to the site specifics (see “Solar Survey” and “Optimal PV” in HP130). Working with PV rack companies can take much of the guesswork out of the process, as they will provide engineered designs to meet wind uplift forces, snow load, and soil or roofing material types. 

Roof-Mounted PV Arrays

Because of space limitations, ground-level shading, and the excavating and trenching required for pole and ground mounts, the least expensive and most frequent location for PV arrays is on a roof. (For a general survey of rack types, see “Rack and Stack” in HP124).

Roofs can be classified as either low- or steep-sloped—low slope generally means a roof with a pitch of less than 3:12 (less than 14°). Low-sloped roofs are often mistakenly referred to as flat roofs, but no roof is ever really flat, as a pitch is needed for shedding water. Even a roof that appears flat will have a pitch of at least 0.5:12.

Top-Down Innovations

On steep-sloped roofs, modules are almost always flush-mounted—mounted parallel to the roof plane. The most common technique for flush-mounting steep roof arrays is “top-down mounting.” Anodized aluminum rails are used to support modules, and stainless steel or aluminum compression clips hold the modules onto the rails, usually with a bolt and nut captured by slots in the rails. This speeds up installation, eliminating bolting through the mounting holes on the back of module frames as was once common. Now, installation is easily accomplished with the modules in position on the rails from above—thus, the description “top-down” (see “Modern PV Roof Mounting” in HP137). 

Recent design improvements in top-down mounting decrease materials and reduce labor. They include automatic grounding  (module bonding via the mounting clips—see the “New Criteria, Listings & Techniques” sidebar) and one-tool installation (all of the bolts have the same size head). 

SnapNrack, a pitched-roof mounting system developed by solar installers, was designed so one wrench fits all bolts. Snap-in nuts attach standoffs and top-down clips, the rails are height-adjustable, and there’s a built-in channel for wire management. In addition, both the mid- and end-clips have a universal design, meaning that regardless of module-frame dimensions, a single clip works with any module and the clips don’t have to be specified in advance.

Structural Attachments

Structural attachments from the array to the roof are a critical part of the installation. The attachment type and method will vary based on the roofing type (shingle, metal, tile, etc.) and with the roof’s structural design (wood trusses, structural insulated panels, metal purlins, etc.). 

Preventing roof leaks and meeting building codes for live and dead loads (including wind uplift, rack and array weight, and snow loads) are primary concerns. A properly installed array will meet these concerns and maintain the roof warranty. In nearly all installations, every roof penetration needs to be flashed for waterproofing. On a composition (asphalt) shingle roof, the metal flashing fits underneath higher rows of shingles, so water runs over the top of the flashing and around the roof penetration. For years, many installers relied solely on sealant for penetrations, but new structural attachments make installing flashed penetrations simple and quick. 

Quick Mount PV manufactures flashing-integrated brackets for a wide range of racks and roofing materials. Their newest products, the Quick Hook curved and flat tile mounts, are the first flashed tile hooks available. Quick Mount PV has also partnered with Schletter to create the Gator Mount—an aluminum-flashed mounting block that attaches to a composition roof and to the Schletter Gator Clamp via a single hanger bolt. Other companies offering flashing-integrated mounts include EcoFasten, SnapNrack, ThomsonTech, Unirac, and Zep Solar.Whether roof-, ground-, or pole-mounted, PV rack and its associated parts, such as structural attachments, grounding, and wire management systems, are available in hundreds of styles and varieties. There has been a recent explosion of companies that offer PV racks. 

Comments (7)

martin sattler_2's picture

Is there any way to figure out which Issue this article appeared in?

Scott Russell's picture

Sure thing, Martin. In the page header, just below the author's name, click on the blue "Issue date" link to display the issue in which this article was published. October/November 2012 in this case.

spriyanaren's picture

Good Article, but lack in step by step installation photos which will be very useful for entry level hobbyist & Enterprenur

Ben Root's picture

Michael is right, but look into other Home Power article like:
http://www.homepower.com/articles/p...
http://www.homepower.com/articles/p...
http://www.homepower.com/articles/l...
http://www.homepower.com/articles/r...
And others. Put " PV Racking" into the article search.

Michael Welch's picture

Hi there. Thanks for the feedback, it is appreciated. There are so many different rack solutions, so many different ways to put them on a roof, and so many different roofs; that it would be very difficult to do step by step instructions that would apply. One could write a book on the subject, but then the innovations are coming fast enough to quickly make the book outdated.

However, many rack manufacturers provide the basic instructions along with their products. Further, we recommend that if somebody is installing a rack for the first time, that they work with somebody that has done it before and knows all the myriad details and potential problems that folks might come across. Hope that helps explain it. Michael for HP.

fotovoltaika's picture

Interesting article

Scott Russell's picture

We're glad you think so. Racking is a highly innovative area of the solar equipment landscape. In recent years, it seems like Home Power is constantly publishing new articles on pioneering racking developments just to keep up.

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