Products & Equipment : Racking

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Solar carports and canopies have proven to be a successful and marketable approach to PV system siting and deployment. In addition to generating power, these structures add significant value to frequently underutilized parking areas, providing shade during the sunny months and protection from precipitation during the wet ones. This article provides system designers, engineers, and procurement and sales teams with overviews of 17 companies that offer solar carports, canopies or awnings in their product and service portfolios.

Many of the companies profiled have long business histories working with steel structures. As the solar industry gained momentum and entered new geographical markets, these vendors optimized their designs to integrate with PV arrays. As evidenced by the substantial number of companies profiled, a competitive market has developed for solar carports and canopies, driving the designers and fabricators of these structures to advance their designs. Today, project developers, integrators and EPC firms have an impressive range of solutions in this product class with a high level of optimization and refinement.

Absolute Steel

Headquarters: Tempe, Arizona
Contact: absoluterv.com • 877.833.3237

Arizona Storage, a privately owned company that also does business under the Absolute Steel brand name, was founded in 1999. At its production facilities on company-owned properties in Arizona and Texas, Absolute Steel fabricates a selection of steel-frame solar-ready carport systems that range from small canopies with two parking spaces to large carport designs suitable for commercial applications. Its showroom in the metropolitan Phoenix area displays its steel buildings, carport systems, barns and storage sheds. Absolute Steel supports customers with site evaluation, structural engineering, on-site management and training, and domestic and international shipping services.

Baja Construction 

Headquarters: Martinez, California
Contact: bajacarports.com • 800.366.9600

In operation since 1981, Baja Construction is a privately owned and vertically integrated design and construction firm with an in-house engineering department as well as its own construction crews. The company specializes in prefabricated, pre-engineered, high-tensile light-gauge steel structures that include solar carports, ground mounts and electric vehicle charging stations, as well as nonsolar carports, and RV, boat and self-storage facilities. Its engineering services and custom designs enable Baja to develop structures that meet site-specific wind load, snow load and geotechnical requirements. The company operates regional offices in Fontina, California; Dallas; Holbrook, New York; Las Vegas; and Phoenix.

Baja’s product line includes four standard configurations. Designed to cover a single row of parking spaces, its Braced Single Post carport includes flat, upslope and downslope options. Full Cantilever offers the same slope configurations, with the carport posts located along one of the structure’s eves. Full Cantilever T covers two rows of parking spaces, with posts located along the structure’s centerline between rows, and is available in flat and sloped array options. Finally, Single Post Back to Back couples two single-post configurations installed adjacent to each other to create a common flat or sloped array surface that covers two rows of parking spaces. All four of these configurations allow for customer-specified design requirements such as eve height, array tilt angle and purlin spacing based on module dimensions, and facilitate both portrait and landscape module layouts.

Carport Structures

Headquarters: Oxford, Michigan
Contact: carportstructures.com • 800.442.4435

Carport Structures has been providing covered parking solutions and structural steel canopy products for commercial applications for more than 40 years. The privately owned and operated fabrication and construction company specializes in the design, manufacturing and installation of structural steel products such as multi-housing carports, walkway canopies and covers, shade structures, park shelters and RV carports.

In recent years it has developed solutions for commercial and utility PV applications, offering a range of services that include project quoting and presentation, site analysis, regional building code review and analysis, structural design, foundation design and layout, project management, foundation excavation and construction, steel structure erection and field fabrication, field painting, and PV racking and module installation. In addition to creating custom designs, it offers 11 standard carport products including single-column cantilever configurations, two-column configurations and louvered configurations that set each individual module row at a customer-specified tilt angle. All carport solutions are available for single-, double- and multiple-lane elevated structures.

Envision Solar International

Headquarters: San Diego
Contact: envisionsolar.com • 866.746.0514

Envision Solar International is a San Diego–based technology company with solar solutions for electric vehicle charging, media and branding, and energy security systems. Founded in 2006, the company went public in 2010 (ticker: EVSI). Envision Solar offers two specialty solar canopy lines: the EV ARC and the Solar Tree. Designed for stand-alone PV-powered electric vehicle charging, the EV ARC line includes several models, such as the EV ARC 3, which has a 3.4 kW canopy-mounted array coupled with 22.5 kWh of energy storage, and the EV ARC 4, which has a 4.1 kW array and 30 kWh of energy storage. Both models are equipped with dc chargers for plug-and-play electric vehicle charging. The EV ARC Digital model combines the EV ARC 4 with an outdoor-rated screen for advertising and branding. In addition, Envision Solar developed the EV ARC Bike/Moto, for electric bike and motorcycle charging. Like the EV ARC products, the Solar Tree line handles stand-alone power generation and vehicle charging. The Solar Tree DCFC (DC Fast Charger) is a compelling option for sites where customers desire fast dc charging for electric vehicles but utility power is not present or is expensive to access.

Florian Solar

Headquarters: Georgetown, South Carolina
Contact: floriansolarproducts.com • 800.356.7426

Florian Solar is a designer and manufacturer of integrated solar structures including sunrooms, greenhouses, canopies, awnings, skylights, and residential and small-scale commercial carports. The third-generation privately owned company was founded in 1947. It partnered with Sanyo, an early manufacturer of glass-on-glass bifacial modules, to develop its first line of solar structures in 2007. Florian’s product line features designs with a high level of aesthetic appeal that fill a niche market in the solar industry; for example, its sunroom and awning systems can completely conceal module interconnect and homerun conductors. While Florian can integrate most module types into its integrated structures based on customer preference, it frequently utilizes bifacial modules from Prism Solar Technologies and Sunpreme. Its structural designs do not shade the back side of installed modules, enabling the back-side generation potential of these products to be harnessed.

Lumos Solar

Headquarters: Boulder, Colorado
Contact: lumossolar.com • 303.449.2394

Established in 2006, Lumos Solar is a privately held company that designs and manufactures two lines of frameless, glass-on-glass modules, as well as integrated rail systems and wireways that conceal conductors, protecting them from damage while improving the visual aesthetics of the array in the built environment. Integrators commonly deploy Lumos systems in solar awning, canopy and carport systems. The Lumos in-house design and engineering team assists customers with conceptual renderings, PE wet-stamped engineering drawings and packages to streamline project permitting.

Lumos Solar developed the LSX and GSX module and rail systems for integration with elevated solar structures, both of which integrate with most third-party solar carport and canopy structural array support systems. The LSX system includes frameless, glass-on-glass 60-cell modules rated at 265 W, 270 W and 275 W at standard test conditions. These modules integrate with the LSX Rail 1.1 system, which includes an integrated wireway. The recently launched GSX Bifi system uses 60-cell bifacial GSX modules rated at 300 W STC for front-side power production and a combined front-side and back-side rating of 330 W per IEC bifacial measurement standard (IEC 60904-1-2 TS). Its mounting and racking system conceals the module junction box and creates a waterproof array surface.

M Bar C Construction

Headquarters: San Marcos, California
Contact: mbarconline.com • 760.744.4131

MBar C Construction is a family-owned and -operated manufacturing and construction firm. The company was founded as M Bar C Carports in 1975 and began developing and installing carports for solar applications in 1997. In 2005, it reestablished itself as M Bar C Construction. The company specializes in both light- and heavy-gauge steel prefabricated and custom parking lot and structure canopies for large-scale projects. It incorporates elevated steel structure design, manufacturing and installation, as well as commercial and industrial electrical services through its M Bar C Electric division. In addition to manufacturing structural steel elements for carports and canopies, M Bar C Construction has developed the SOLAR F.I.T. (Fast Install Track) SYSTEM, which uses a channel system rather than top-mount clamps to secure modules to a substructure. This approach allows installers to mount modules from below and eliminates some of the OSHA safety concerns associated with typical top-mount systems. M Bar C Construction primarily serves the Western US, including Arizona, California, Colorado, Hawaii, Nevada and Oregon. Approximately 90% of its installations are design-and-build projects.

Orion Solar Racking

Headquarters: Commerce, California
Contact: orionsolarracking.com • 310.409.4616

Founded in 2009, the privately owned Orion Solar Racking develops and manufactures solar-mounting solutions for residential, commercial, industrial, agricultural and utility-scale projects. Orion Solar offers three standard product models for carport systems: KRONOS, LETO and TITAN. The KRONOS model is primarily intended for single-parking-space residential systems and is available with clearance heights from 8 feet, 5 inches, to 11 feet, 5 inches. Custom colors are available. Its galvanized steel, curved single-post design supports six or eight modules in portrait orientation at tilt angles of 0°, 5° or 10°. The LETO carport system is a steel double-column single-cantilever carport designed to span two parking spots for a total of 18 feet. Intended for commercial applications, LETO structures allow side-by-side installation to shade larger areas. The system’s columns and beams are available with galvanized or primed finishes. Orion Solar’s TITAN carport system is a double-column, double-cantilever tee-style carport designed to cover four parking spots in a two-by-two parking configuration. The LETO and TITAN systems are available with an array tilt angle of 0°, 5° or 10° and feature purlins that allow slide-in module mounting. Options include area lighting under the canopy and electric vehicle charging stations. Orion Solar also offers custom-designed solar carport solutions.

Quest Renewables

Headquarters: Atlanta
Contact: questrenewables.com • 404.536.5787

Quest Renewables is a privately owned company launched in 2014 to commercialize solar racking products developed by the Georgia Tech Research Institute under the US Department of Energy’s SunShot Initiative. The company’s QuadPod Solar Canopy uses steel top and bottom chords connected with a series of tubular web struts to create 3-D trusses, which support elevated-structure solar arrays such as carports and canopies. This design can handle 60-foot spans between piers, 30-foot cantilevers and array capacities of 30 kW per pier.

The QuadPod’s modular design streamlines shipping costs and provides flexibility on-site. Installers assemble the truss components using bolted hardware, and they then secure and prewire modules on-site at ground level. They use a crane to lift the completed assemblies atop the piers’ tubular support columns. This pick-and-place approach minimizes overhead work and improves jobsite safety. Quest Renewables offers an east-west configuration of its QuadPod system that enables a 15% higher power density than south-facing QuadPod canopies provide and that allows integrators to optimize inverter capacities when sizing for east-west array production curves.

Powers Solar Frames

Headquarters: Phoenix
Contact: powerssolarframes.com • 888.525.0180

Powers Solar Frames is a division of privately owned Powers Steel and Wire, a manufacturer of steel structures, lintels, masonry products, rebar and solar racking systems. The solar product line includes driven-pile and ballasted racking systems for commercial, industrial and utility-scale projects, as well as solar carport frames. Powers Solar Frames’ carports use galvanized structural elements (columns, rafters and purlins) that do not require on-site painting. In addition, all structural members have bolted connections that eliminate field welding and weld inspections.

Power Solar Frames offers two carport designs, its semi-cantilever box-beam model and its tee box-beam model. Both systems use 10-gauge 16-inch-by-8-inch galvanized structural members for the carport’s columns and rafters. The tee box-beam model’s rafter can span up to 39 feet. Both carport models permit modification for tilt angle, clearance height and site-specific requirements such as snow load, wind load, and geotechnical and seismic requirements. Power Solar Frames’ carport structures feature its patented steel Super Purlin. The purlin’s profile creates a channel that allows installers to slide in modules from the carport system’s gable ends. This approach eliminates top-down module-mounting hardware and fall hazards associated with working above the array plane. Each module requires four UL 2703–certified gator clamps that install from the underside of the array to secure the module to the adjacent purlin.

RBI Solar

Headquarters: Cincinnati
Contact: rbisolar.com • 513.242.2051

RBI Solar designs, engineers, manufactures and installs solar mounting systems for commercial and utility-scale solar projects. The privately owned company operates US offices in Atlanta; Temecula, California; and Washington, North Carolina. It completed two notable acquisitions in 2014, including PV carport manufacturer and installer ProtekPark Solar, and Renusol GmbH and its subsidiary, Renusol America. RBI Solar’s services include design, engineering drawings for all 50 states, project management and nationwide installation.

RBI Solar offers pre-engineered solar carport structures, including single-slope, gable, inverted and full-coverage designs. It typically utilizes the two-slope gable configuration for north-south orientation with panels sloping 5° on the east and west array faces. This inverted design provides increased clearance at the structure’s eaves while promoting water and snow movement toward the center column row of the structure. RBI Solar also offers a full-coverage design suitable for protecting large parking areas, including the drive aisles between parking rows. Typical applications for the full-coverage carport configuration are parking garages, drive-throughs, and bus or truck loading and unloading zones. RBI Solar carport systems do not require field welding, drilling or other on-site fabrication. The company offers customized designs as well as numerous options including galvanized and epoxy-coated finishes.

Schletter

Headquarters: Shelby, North Carolina
Contact: schletter.us • 888.608.0234

Schletter GmbH has a 40-year history in the design and manufacture of steel and aluminum products. The privately owned company founded its US subsidiary in 2008 with the launch of a sales and manufacturing facility in Tucson, Arizona. Its solar product portfolio includes mounting structures for carports, roofs and ground-mounted PV applications in the utility, commercial, industrial and residential markets.

Schletter’s Park@Sol carport line includes three standard configurations that accommodate single and double rows of parking. Its carport structures do not require on-site welding or cutting. Multiple foundation options are available, such as cast-in-place concrete ballasts, concrete pillars and micropiles. The micropile foundation, which allows a streamlined foundation design, uses a hollow metal rod that the construction team installs to an engineered depth to minimize concrete requirements while meeting high wind- and snow-load requirements. Schletter has an in-house staff of engineers and geotechnicians to assist with site-specific carport system engineering. It offers multiple options for its Park@Sol structures, including cable management, subdecking, inverter mounts, custom designs and color options, and branding solutions.

S:FLEX

US Headquarters: Denver
Contact: sflex.com • 303.522.3974

With its global headquarters in Hamburg, Germany, privately owned S:FLEX GmbH was founded in 2009. S:FLEX’s product lineup includes solutions for pitched and low-slope rooftops, ground-mounted systems and solar carport applications. Its standard carport products include full cantilever, partial cantilever, and tee upslope and downslope configurations, as well as an inverted configuration that channels precipitation runoff to the structure’s center. S:FLEX carport systems provide several module-row configuration options and are compatible with both framed and frameless modules mounted in portrait or landscape orientation. Standard array tilt angles of up to 15° are available

While S:FLEX engineers its column spacing and spans based on site-specific wind, snow and seismic load requirements, designs typically space columns at 27 feet on center and place them between every three parking bays, creating individual parking spaces that are 9 feet wide. Its carports are compatible with multiple foundation types, including spread footings and foundations with embedded helical piers. Carport options include integrated electrical grounding and industrial painting of steel structural components. S:FLEX supports carport projects with project-specific design and engineering, as well as installation support.

Skyline Solar

Headquarters: Gilbert, Arizona
Contact: skylinesolaraz.com • 480.926.0122

Skyline Solar is a division of Gilbert, Arizona–based Skyline Steel. Founded in 1983, Skyline Steel designs, manufactures and installs commercial covered parking structures. It recognized the added value that solar offered many of its carport customers and entered the solar industry in 2002, establishing Skyline Solar in 2009.

Skyline Solar offers products for solar applications including carports; large-area canopies for parking garages; bus and truck parking; RV, boat and self-storage facilities; electric vehicle charging stations; and commercial and utility-scale low-slope–roof and ground-mount structures. A design-build firm, Skyline Solar typically provides products and services to integrators, developers and EPC firms that are responsible for the installation and commissioning of solar power systems. Its services include project estimating and management, conceptual project renderings, structural plan sets and certifications in all 50 states, foundations, steel construction and erection, and PV module installation.

Skyline Solar offers a wide range of standard solar carport and canopy models as well as custom designs. Its prefabricated one-column SkyTree shade structure, supporting array capacities of up to 18 kW at a tilt angle of 5° or 10°, is well suited for small covered-parking installations. For large-scale projects, Skyline Solar offers single- and double-cantilever tee designs that support modules at tilt angles of 5°, 10° or 15° in portrait or landscape orientation. Its dual- and multiple-post solar canopies are intended for large parking areas, garage tops, school playgrounds and bus parking lots, and they allow module-mounting options including flat canopy, 5° canopy or louvered module installations at tilt angles of 5°, 10° or 15°. Skyline Solar also offers fastener solutions such as its SkyBite clip (ETL certified to UL 467), which permits installers to secure and electrically bond modules to the carport or canopy structure’s purlins from underneath the array.

Solar Carports

Headquarters: Sarasota, Florida
Contact: solarcarportsllc.com • 941.702.2342

With manufacturing facilities in California and Virginia, Solar Carports specializes in the design and installation of structural canopies to support solar power systems. It offers several pre-engineered designs as well as custom carport and canopy designs. Standard models include partial cantilever, full cantilever and tee upslope and downslope configurations, as well as inverted configurations. Options include galvanized and painted finishes, watertight canopies, gutters, downspouts, and LED canopy under lighting. Solar Carports’ affiliate, Sarasota-headquartered Region Solar, provides full EPC and project management services for installations deploying Solar Carport’s structures.

Structural Solar

Headquarters: Chicago
Contact: structuralsolar.com • 708.275.9030

Structural Solar provides solar carport and canopy design-build and contract manufacturing services to solar developers, integrators and EPCs based on site-specific and project-specific requirements. Its services range from solar structure design and engineering to fully manufactured and installed structural systems in locations nationwide, including Hawaii and Puerto Rico. In addition to providing carport and canopy designs, Structural Solar offers waterproof structures for frameless glass-on-glass bifacial PV module installations.

SunPower

Headquarters: San Jose, California
Contact: us.sunpower.com • 800.786.7693

Publicly held SunPower designs, manufactures and deploys high-efficiency PV modules and systems worldwide for residential, commercial and utility-scale projects. Founded in 1985, SunPower announced its initial public stock offering in 2005 (ticker: SPWR). In 2015, SunPower acquired Solaire Generation, a well-established solar carport and canopy design, fabrication and installation firm founded in 2008.

Solaire by SunPower’s product line includes patented solutions for large-scale parking lot and garage-top applications. Its carport configurations include single-column, single-cantilever and double-cantilever tee designs on a single incline; dual-incline inverted designs; and dual-column long-span designs. For example, its Long Span 360 product covers two parallel parking rows and an internal drive aisle with one contiguous PV-covered canopy that has an array inclination angle of 1°–10°. Another example is its 360 D model, which has a dual-incline configuration that safely directs snow and ice to the center of the structure. It features a standard minimum drive aisle clearance of 13 feet, 6 inches, and is available in widths of 34 feet to 41 feet, column-to-column spacing of 18 feet to 32 feet and inclination angles of 1° to 15°.

In 2015, SunPower launched its highly integrated Helix PV system platform for commercial and industrial low-slope rooftop, carport and tracked PV systems. The system is standardized but configurable. It incorporates five major value-engineered component groups: modules, mounting hardware, cable management, power stations and energy analytics. Several configurations of the Helix Carport Structure are available, and all feature the Helix platform’s integrated approach. Components and features include high-efficiency SunPower panels, a mechanical mounting and electrical system, a column-mounted plug-and-play inverter power station, SunPower EnergyLink Monitoring hardware and software, and LED lighting. Design options include painted columns and beams, snow guards, and decking and branding solutions.

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More than 600 solar equipment and service providers will display their products at the Solar Power International conference and expo in Las Vegas September 13–15. In this preview article, I highlight 17 companies that provide a wide range of solutions for system integrators. Some of the equipment detailed here recently launched or is set to launch at the event. Some is time-tested in fielded systems across the US. And some represents new or out-of-the-box ideas that may or may not take hold, but that nonetheless represent the dynamic innovation that keeps the solar industry moving forward.

Modeling, Measurement and Testing

Aurora Solar - Booth WSUA12

Aurora Solar develops cloud-based software that enables sophisticated solar project engineering design, provides workflow management functionality, and facilitates sales and customer acquisition for solar installers and financers. The company launched in 2013 with the backing of the US Department of Energy’s SunShot Initiative. The Aurora design platform includes features such as 2-D and 3-D modeling, 3-D visualizations, irradiance maps and annual shade values, automatic roof setbacks, electric bill and financial analysis, sales proposals and remote shading analysis, as well as engineering features such as performance simulations. Monthly and annual per seat pricing is available, as are enterprise-scale packages. The basic subscription is $159 per month, per seat, and includes the features listed. The premium-level product costs $259 per month, per seat, and offers additional features including monthly shade values, site modeling with LIDAR, NEC validation, single-line diagrams, BOS components and detailed bills of materials.
Aurora Solar / aurorasolar.com

Curb - Booth W902

Launched in 2012, Curb is a new entrant to the solar and energy efficiency market. Its home energy monitoring system offers integrators a compelling option for circuit-by-circuit energy use monitoring and visualization at a low price point ($399). Curb designed its data acquisition system for mounting in a home’s load center. The system includes 18 CT sensors for individual circuit monitoring. This level of monitoring granularity facilitates specialized tasks—for example, determining how much energy electric vehicle charging is consuming. The Curb system can measure on-site energy generation from PV systems and integrate production values with home consumption data. Curb includes a variety of notifications for events, such as when a user has accidentally left on a given appliance. Additional features include a power budget manager that allows users to track progress against a monthly energy budget. The software identifies changes in consumption and provides suggestions for conserving energy and money. With the upcoming launch of its home energy intelligence product, Curb plans to take its platform a step further with functionality that aims to predict appliance failure and identify required maintenance for components such as HVAC or refrigerator compressors.
Curb / 844.629.2872 / energycurb.com

Folsom Labs - Booth 3053

At the core of San Francisco–based Folsom Labs’ design efforts is the principle that every PV system design decision can and should be quantified in terms of its yield and financial implications. To further this goal, Folsom Labs develops HelioScope, a PV system design tool that integrates system layout and performance modeling to simplify the process of engineering and selling solar projects. The platform integrates easy-to-use design tools and bankable energy yield calculations. A core differentiator for HelioScope is that it is designed on a component-based model, which separately models each piece of the system (individual module, conductor or inverter, for example). Folsom Labs offers both monthly and yearly subscription rates. The cost of a single-seat monthly subscription is $79 and includes automatic CAD export, energy simulation, shade optimization, one-click sharing, a component library of 45,000 items, global weather data and PAN file support. Solar professionals can use HelioScope to design and model PV plants with capacities of up to 5 MW.
Folsom Labs / folsomlabs.com

Seaward Solar - Booth W824

Seaward Solar is a division of the UK-based Seaward Group. Its line of PV test equipment is one of the more recent development efforts in the company’s 75-year history in electrical safety test measurement instruments. Seaward Solar’s offerings include products used in PV system commissioning and operation verification, such as conductor insulation testers, irradiance meters and I-V curve tracers. The company recently announced the launch of its new PV210 multipurpose PV tester, which combines installation and commissioning tests with the ability to perform I-V curve analysis. Simple push-button operation allows users to conduct all the electrical commissioning tests required by IEC 62446, including open-circuit voltage, short-circuit current, maximum power point voltage, current and power, and insulation resistance. In addition, the PV210 performs I-V curve measurements in accordance with IEC 61829 to determine whether the measured curve deviates from the expected profile. For full, detailed analysis, users can transfer measured data from the test instrument to an accompanying PVMobile Android app to create high-definition color displays of the I-V and power curves for individual PV modules or strings.
Seaward Solar / 813.886.2775 / seawardsolar.com

Modules

LG Solar - Booth 1447

LG’s activity in solar module development dates back to 1985, when it (under the brand GoldStar Electronics) conducted its initial multicrystalline PV cell R&D. Since then the South Korean company, part of the global LG Group, has rebranded and become a household name in appliances and personal electronics. Another LG Group subsidiary, LG Chem, is on the front lines of designing and manufacturing lithium-ion batteries for use in stationary solar-plus-storage systems. LG Solar initiated mass production of its PV technology in 2010. It recently announced the US availability of its NeON 2 72-cell module models, developed for commercial and utility-scale installations. The three models—LG365N2W-G4, LG370N2W-G4 and LG375N2W-G4—have rated power outputs ranging from 365 W to 375 W. The new models expand LG’s high-efficiency PV lineup, which includes the 60-cell NeON 2, with rated power outputs of 305 W–320 W and module efficiencies of 18.6%–19.5%.
LG Solar / lgenergy.com

SolarWorld - Booth 911

SolarWorld has more than 40 years of history in solar module design and manufacturing, dating back to Bill Yerkes’ founding of Solar Technology International and ARCO Solar’s development efforts in the 1970s, the assets of which SolarWorld acquired. Today, SolarWorld offers a full line of Sunmodule products, including two glass-on-glass bifacial Bisun models, as well as system packages that incorporate Quick Mount PV’s railless Quick Rack system and power electronics from vendors such as ABB, Enphase and SMA America. In July, SolarWorld announced the launch of its 1,500 Vdc–rated 72-cell SW 340–350 XL MONO module line, which is available with 340 W, 345 W and 350 W maximum power. The introduction of the high-voltage XL product positions SolarWorld to take advantage of the expanding deployment of 1,500-Vdc PV power plants in the US.
SolarWorld / 503.844.3400 / solarworld-usa.com

Sunpreme - Booth 2125

Headquartered in Sunnyvale, California, and launched in 2009, Sunpreme is differentiating itself from commodity module vendors with the development of thin-film, high-efficiency, bifacial, double-glass frameless modules. The company bases its unique cell architecture on its patented Hybrid Cell Technology (HCT) platform, which utilizes four amorphous silicon thin-film depositions on surface-engineered silicon substrate. The frameless double-glass module design does not require electrical grounding. Sunpreme’s Maxima GxB module line includes five modules, two of which integrate Tigo Energy’s TS4-L (long-string) dc optimizers. The highest-power module, the GxB 370W, has a power output of 370 W STC and a module efficiency of 19.1%. Sunpreme specifies a bifacial output for the GxB 370W of 444 W, with a 20% boost in power from the module backside and a resulting module efficiency of 22.9%.
Sunpreme / 866.245.1110 / sunpreme.com

Ten K Solar - Booth 759

Ten K Solar, founded in 2008, leverages a unique nonserial architecture with its module and integrated system design.  Its Apex module line includes the Apex 500W Mono (500 W monocrystalline) and the Apex 440W Poly (440 W polycrystalline). Both modules utilize 200 half-cells connected in a matrix (serial and parallel connections). This structure allows current to flow through multiple pathways within a module, improving partial shade performance, reducing the impact of soiling and hot spots, and eliminating a single point of potential failure within the module. Module-level power electronics convert the internal module voltage (<18 Vdc) to an operating voltage of 35 Vdc–59 Vdc. Ten K expands on this shade- and fault-tolerant low-voltage parallel architecture with its ballasted DUO PV system for low-slope roofs and ground-mounted arrays. The DUO system configuration, which integrates groups of parallel-connected microinverters on a shared dc bus, places rows of modules in tandem, back-to-back, to maximize power density and energy yield per square foot.
Ten K Solar / 952.303.7600 / tenksolar.com

Power Electronics

Delta - Booth 2259

Delta Group is the world’s largest provider of switching power supplies and dc brushless fans, as well as power management equipment, networking products and renewable energy solutions, including solar inverters. Historically, Delta has positioned itself somewhat behind the scenes in the US solar market, as other vendors have rebranded the OEM’s inverter products. However, Delta is developing its presence in the US, introducing new solutions to the market. Two recent examples are its 7 kW RPI H7U single-phase inverter and its 80 kW M80U 3-phase string inverter. The UL-certified RPI H7U features a secure power supply for limited daytime power production when the grid is not present, and 4 MPP trackers with a full-power MPPT range of 185 V–470 V at 240 Vac and a wide operating voltage range of 30 V–500 V. Integrators continue to deploy high-power 3-phase string inverters in increasingly large multimegawatt PV plants. Delta’s 80 kW M80U inverter will support this upward capacity trend. The inverter has a maximum input voltage rating of 1,100 V, a full-power MPPT range of 600 V–800 V and an operating voltage range of 200 V–1,000 V. Options for connection on the dc side include 16 source-circuit fuseholders, two 3/0 AWG terminal blocks and 18 pairs of MC4 connectors for wire harness compatibility. With a unit weight of 180.6 pounds or less, depending on configuration, the M80U is light enough to permit a two-person installation.
Delta / delta-americas.com

OutBack Power - Booth 2825

OutBack Power designs and manufactures inverter/chargers, charge controllers, integration equipment and monitoring solutions for stand-alone and utility-interactive battery-based renewable energy systems. Currently a member of the Alpha Group, OutBack was founded in 2001. Battery-based PV systems are inherently more complicated than grid-direct ones. The accumulated experience of established power electronics companies such as OutBack is a valuable asset for integrators when applications require advanced system configurations. In 2011, OutBack released its Radian series of hybrid, utility-interactive split-phase 120/240 Vac inverter/chargers. Available in 4,000 W and 8,000 W power classes, the Radian features two ac inputs for grid and ac generator connectivity and a high degree of component integration. With the recent introduction of four VRLA storage batteries optimized for specific applications such as float service or regular deep cycling, OutBack now offers a comprehensive product family for energy storage applications listed to the relevant UL standards.
OutBack Power / 360.435.6030 / outbackpower.com

SMA America - Booth 959

SMA Solar Technology was founded in 1981. Its US subsidiary, SMA America, was the first inverter manufacturer to offer high-voltage string inverter models in the US market. In addition to developing single- and 3-phase string inverters, SMA has also devoted significant resources to the development of high-power central inverters for multi-megawatt medium-voltage utility-scale PV plants. As the US and global inverter markets have evolved, more manufacturers are focusing on either string inverters or central inverters. SMA is one of a shrinking group of inverter vendors that continue to create solutions in both product classes for utility-interactive applications. One example is its second-generation Medium Voltage Block for utility-scale applications deploying its Sunny Central 1850-US, 2200-US and 2500-EV central inverters. SMA’s 3-phase inverter lineup, the Sunny Tripower series, currently includes six models with rated power capacities of 12 kW–60 kW and 480 Vac output. The company has also been redesigning its single-phase inverter family. It recently launched updated Sunny Boy 3.0-US, 3.8-US, 7.0-US and 7.7-US models, which join the 5.0-US and 6.0-US models it introduced earlier this year, to provide integrators with greater design and installation flexibility. SMA plans to release a high-voltage Tesla-compatible battery inverter for the US market in early 2017. It has also made a significant investment in incorporating MLPE technology from Tigo Energy into its systems, in anticipation of module-level rapid-shutdown requirements in NEC 2017.
SMA America / 916.625.0870 / sma-america.com

Trackers, Racking and Mounting

Array Technologies - Booth 2805

Array Technologies (ATI) began manufacturing solar trackers in Albuquerque, New Mexico, in 1992 and has continually evolved, redesigned and scaled its solar tracking equipment, systems and services in step with the solar industry, especially in the utility-scale PV plant market. ATI launched its third-generation centralized DuraTrack HZ v3 horizontal single-axis tracker in 2015 and continues to be a strong proponent of centralized tracking systems. The DuraTrack HZ v3 has an algorithm with a GPS input tracking method and a ±52° tracking range of motion with backtracking functionality. The system’s drivetrain has sealed gearboxes designed to be maintenance-free for the life of the plant. The DuraTrack HZ v3 has a 135 mph 3-second-gust exposure-C allowable wind-load rating. A passive mechanical wind protection system that does not require power to operate safeguards the tracker during high-wind events and eliminates the maintenance requirements associated with active stow components. Configurations for c-Si modules include one-up in portrait orientation and two-up in landscape orientation, as well as four-up in landscape for thin-film modules. To speed module installation, ATI has developed an innovative single-fastener module clamp with integrated grounding.
Array Technologies / 855.872.2578 / arraytechinc.com

Beamreach Solar - Booth 2941

Beamreach Solar (formerly Solexel, founded in 2007) showed the demo installation of its Sprint PV system to big crowds of curious onlookers at July’s Intersolar North America event in San Francisco. Developed specifically for weight-constrained, low-slope commercial rooftops with TPO membranes, the system integrates a 60-cell monocrystalline 290 W, 295 W or 300 W module with a composite frame and an integrated racking system. The weight per module, including its racking components, is 38 pounds. The system is not ballasted or penetrating, but rather adheres directly to the TPO roofing membrane. Each row of modules simply snaps into the back feet of the previous row. The lack of metal components eliminates the need for equipment grounding. For shipping, Beamreach packs 26 modules with integrated racking components on a single pallet. Time will tell whether the Beamreach Sprint system will gain traction in the field; however, its design clearly exemplifies the innovation that is happening across the PV industry.
Beamreach Solar / 408.240.3800 / beamreachsolar.com

SunLink - Booth 2037

SunLink launched its first racking systems for commercial rooftops in 2004 and helped pioneer the design and deployment of ballasted PV array mounting systems. More recently, the company has been expanding its product portfolio and expertise to include project development and O&M, SCADA and data monitoring services, and PV tracker systems. SunLink will launch its TechTrack Distributed single-axis tracker in Q3 2016. The self-powered tracker uses a slew drive, a 24 Vdc motor, a lithium-iron phosphate battery and an integrated PV module to drive the tracker. Its tracking range of motion is ±60°. Installers can mount modules one-high in portrait orientation, and array configurations are optimized for 90 modules per 30 kWdc row. A secure modified Zigbee mesh network provides on-site communication between the tracker controllers. The TechTrack Distributed system reacts intelligently to real-time conditions to increase generation and reduce the risk of damage to the power plant. Dynamic stabilization provides damping during critical events such as high winds. The tracker is designed for 105 mph and 5 psf standard loads and is configurable for wind loads of up to 150 mph and snow loads of up to 60 psf.
SunLink / 415.925.9650 / sunlink.com

Conductor Aggregation and Management

CAB Solar Booth 311

Under its CAB Solar brand, the Cambria County Association for the Blind and Handicapped manufactures a range of products that include cable rings and saddles for PV cable management, while providing rehabilitation and employment services to persons with disabilities living in Cambria County, Pennsylvania. Elevated cable systems are gaining popularity in utility-scale PV plants, and CAB was an early supplier to these projects. CAB Solar’s PVC-coated rings and saddles feature a high–dielectric grade, flame-retardant and UV-stabilized coating, applied to 100% of the product’s surface. The resulting rings and hangers are electrically insulated and durable in corrosive environments. CAB offers an extensive range of PV wire management solutions, including multicarrier hangers that provide physical separation between dc source-circuit conductors, ac cables and data transmission circuits. The company also manufactures high-visibility safety vests, bags, pouches and holders for the safe organization and transport of hand tools, cordless tool batteries, meters and communication devices in rooftop and other environments.
CAB Solar / 814.472.5077 / cabproducts.com

HellermannTyton - Booth 625

HellermannTyton is a global manufacturer of cable management, identification and network connectivity products. Its North American headquarters are located in Milwaukee, Wisconsin. Its products for PV applications include Solar Ties and Solar E-Clips that enable flexible and secure routing of conductor and cable bundles. HellermannTyton also offers Solar Identification printers, labels and software systems that provide professional and durable PV system labeling. Its Ratchet P Clamp is an innovative solution for cable management. The adjustable ratchet clamp mechanism is available in four sizes for cable bundles or conduit ranging from 0.24 inch to 2 inches. In addition, the product is available with three lengths of mounting plates and 15°, 30°, 90° and 180° angle orientations. The Ratchet P Clamp is designed for easy opening using a small flathead screwdriver. Installers can stack the clamps for parallel cable runs and offset applications.
HellermannTyton / 800.537.1512 / hellermann.tyton.com

SolarBOS - Booth 935

Founded in 2004, SolarBOS focused from the start on configurability, with its first product a configurable 600 Vdc source-circuit combiner box that allowed customers to specify the number of circuits and the NEMA rating of the enclosure. This approach remains a core feature of the extensive range of combiner boxes, recombiners, disconnects, battery connection panels and cable assemblies SolarBOS offers today, including many product versions listed for 1,000 Vdc and 1,500 Vdc applications. In 2015, SolarBOS rolled out its Wire Solutions products for deployment in the growing number of commercial and utility-scale systems that use pre-engineered wire harness and cable assemblies. The company’s product family for these applications includes overmolded Y harnesses with or without inline fuses, homerun cable assemblies and combiner box whips. All wire harness assemblies are custom manufactured to client specifications. Customers can choose from various wire gauges and conductor jacket colors, industry-standard connectors and custom labels at each connection point.
SolarBOS / 925.456.7744 / solarbos.com

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At Solar Power International last year, a sales representative for one of our distribution partners inquired: “Why do so many of my customers order 30 A fuses in their source-circuit combiner boxes?” This is a good question. After all, most crystalline silicon (c-Si) PV modules have a short-circuit current (Isc) rating in the 8–9 A range and carry a 15 A–series fuse rating. This is so common that source-circuit combiners typically come standard with 15 A series fuses. Occasionally, an engineer might specify 20 A fuses to account for thermal derating. However, 30 A fusing assumes an Isc of roughly 18 A, which is an unprecedented series fuse rating for today’s PV modules.

So why do integrators request combiners with 30 A fuses? The answer is not a function of module ratings per se, but rather of how system integrators deploy these modules. Specifically, more and more installation companies use special Y-connector assemblies to parallel PV source circuits in the array field as a way to optimize electrical balance of system (eBOS) costs.

About Y-Connectors

Most industry veterans have seen parallel branch connectors or Y-connector assemblies at conferences or pictured in trade publications or product catalogues. For example, both Amphenol and Multi-Contact offer male and female branch connectors rated for 30 A, as well as overmolded Y-connector assemblies with optional inline fuses. Many eBOS companies also offer customizable Y-connector assemblies. What these connectors and assemblies all have in common is that they have two inputs and one output, allowing installers to make plug-and-play parallel connections within the array.

Until recently, paralleling source circuits within an array was most common in thin-film applications. Compared to c-Si PV modules, thin-film technologies tend to have a higher Voc and a lower Isc. As a result, it behooves integrators to use wire harnesses with inline fuses to parallel thin-film PV source circuits prior to landing them in a combiner box. This practice is cost-effective because it improves conductor utilization within the array and limits the number of combiner box inputs.

Designers can apply these same principles to c-Si PV arrays. After all, touch-safe fuseholders in combiner or inverter wiring boxes are generally 30 A rated, whereas most PV modules have a 15 A series fuse–rating. Therefore, integrators may be able to improve project economics by using Y-connectors to parallel a pair of source circuits ahead of these fuseholders. Before evaluating the potential cost savings associated with this approach, let us review some practical considerations.

Code implications. NEC Section 690.9 requires overcurrent protection for PV modules or source circuits, except when there are no external sources of fault current, or when the short-circuit currents from these sources do not exceed the ampacity of the conductors and the maximum series fuse rating. To make a parallel connection ahead of a combiner box, designers need to account for potential sources of fault currents as well as the module manufacturer’s series fuse ratings. Generally speaking, parallel connections within the array require Y-connector assemblies with inline fuses. In effect, designers need to relocate 15 A series fuses from the combiner box out into the array wiring.

Since parallel connections increase current, designers also need to evaluate conductor ampacity between the Y-connector and the dc combiner or inverter-input wiring box. To achieve the desired cost savings, integrators need to be able to parallel source circuits within the array without unnecessarily incurring the expense of larger-diameter conductors. To avoid having to step from 10 AWG to 8 AWG copper conductors, for example, designers should avoid or minimize situations that require conductor ampacity adjustments according to Article 310. The two most common ampacity adjustment scenarios relate to the number of current-carrying conductors (see Table 310.15[B][3][a]) and distance above the roof (see Table 310.15[B][3][c]). When paralleling source circuits within the array, therefore, it generally makes sense to limit the number of conductors bundled or grouped together to no more than three and to maintain a distance above the roof of at least 12 inches.

Manufacturer limitations. While most of the finger-safe fuseholders for 10 mm by 38 mm fuses found in combiner boxes are manufacturer rated for 30 A, the busbars connected to the fuseholders are not always capable of carrying 30 A of current. Integrators should check with the combiner or inverter manufacturer to ensure that the product is compatible with the use of 30 A fuses.

In some cases, equipment manufacturers require an allowance for heat dissipation where fuseholders are fused at 30 A. The concern is that a lack of space between fuseholders can cause a fuseholder to overheat, potentially melting the plastic and causing a fault. This is not an issue when inputs are fused at 15 or 20 A, as is typical of most string inverter or combiner box applications. However, it may become an issue under continuous loading at full power with 30 A fuses. Landing input conductors on alternating fuseholders, as shown in Figure 1, and removing the unused fuses is one way to improve heat dissipation.

Commissioning and maintenance. From a commissioning and maintenance perspective, incorporating Y-connectors into the PV array wiring does compromise convenience somewhat. After all, landing individual source circuits in combiner boxes provides commissioning agents and service technicians with a convenient means of isolating individual circuits, both to validate proper installation and to establish baseline performance parameters. Using Y-connectors pushes some of the parallel connection points into the array, which can complicate some routine maintenance and troubleshooting procedures, such as taking Voc measurements on a single source circuit.

Arrays fielded with Y-connectors may also require specialized diagnostic tools. After array commissioning, source-circuit voltage measurements are less important than I-V curve traces, as the latter provide more insight into array health. To capture I-V curve traces on source circuits paralleled using a Y-connector, service technicians must have access to an I-V curve tracer rated to process the combined short-circuit current of both strings. At present, the Solmetric PVA-1000S is the only handheld I-V curve tracer offered with an optional 30 A measurement capability. With this 30 A–rated PV Analyzer, technicians can perform an I-V curve trace in a combiner box on two paralleled c-Si PV source circuits. If technicians have access to a 15 A–rated I-V curve tracer only, they will need to isolate the source circuits entering a Y-connector and trace each I-V curve individually.

Cost Reductions

The reason system integrators are willing to make a small sacrifice in convenience is that the proper use of Y-connectors reduces installed system costs. The savings are twofold: material savings associated with a reduction in the total length of PV Wire within the array field, and labor savings, since installers do not have to make as many terminations in source-circuit combiners.

To realize the maximum PV Wire savings, installers need to locate both poles of each PV source circuit at roughly the same spot within the array table. Using the leapfrog wiring method illustrated in Figure 2 is a good way to accomplish this. Where module wire whips are long enough to accommodate leapfrog wiring, this method eliminates about 30–60 feet of PV Wire per source circuit compared to daisy-chain wiring, with the reduction depending on string length (which is largely a function of nominal system voltage). Leapfrog wiring alone can reduce material costs by as much as $20,000 on a 5 MW PV system. (See “Cost-Saving PV Source Circuit Wiring Method,” SolarPro, April/May 2014.) Integrators can reduce material costs even further by combining leapfrog wiring with Y-connectors.

Case study. To illustrate, let us consider a hypothetical example where the basic building block for a large-scale PV array is a 50 kW string inverter that is processing power from a 240-module array table. Each array table is mechanically configured two modules high by 120 modules wide and wired electrically with 12 parallel-connected 20-module source circuits. The wire whips are long enough to accommodate leapfrog wiring. A main service road runs north and south along the east edge of the array.

As shown in Figure 3, the total length of PV Wire per array table is a function of both inverter placement and array wiring. Locating the inverter at the east end of an array table, as assumed in Option 1, provides service technicians with optimal inverter access for O&M purposes but requires the most PV Wire per inverter. Mounting the inverter in the middle of an array table, as shown in Option 2, dramatically reduces PV Wire requirements, but complicates array serviceability. Service technicians will have a harder time reaching each inverter. It may also be impractical or undesirable to run ac conductors within the array field. Option 3, which combines leapfrog wiring with Y-connectors, provides the best of both worlds as it allows for optimal inverter placement and reduces the use of PV Wire significantly.

As compared to Option 1, the combination of leapfrog wiring and Y-connectors in Option 3 effectively reduces the homerun conductor length within the array by half. This setup does not offer a free lunch, however, as the cost to purchase Y-connectors and inline fuses offsets some of the PV Wire savings. While it is possible to purchase inline fuseholders and unfused Y-connectors separately and plug them together in the field, it is generally more cost-effective to purchase an integrated assembly. Companies such as Amphenol, Eaton, Shoals Technologies Group and SolarBOS all offer Y-connector assemblies with integral inline fuses. When purchasing an all-in-one solution, integrators should order extra assemblies for O&M purposes; in the rare event that one fuse blows, they will need to replace the entire assembly.

Table 1 estimates the total material and labor savings associated with deploying array-table configuration Option 3 rather than Option 1. Assuming that 10-gauge PV Wire costs $0.20/foot, you can save more than $400 per array table by adding Y-connectors at the end of each adjacent pair of source circuits (2,070 ft. × $0.20/ft.). While it will cost $240 to add six pairs of fused Y-connector assemblies (12 Y-connectors x $20/each), the net material savings per array table are roughly $174 ($414 less $240). Labor savings are estimated at 1 hour per array table and reflect the fact that installers will spend less time managing homerun conductors within the array (saving roughly 45 minutes) and will have to make only half as many dc terminations at the inverter (saving roughly 15 minutes). Assuming a labor rate of $80 per hour, the total material and labor savings are $254 per array table, which extrapolates to $5,080 per MWac ($0.005/W).

Of course, every array is different, and material and labor costs vary from region to region, so results may vary. However, this case study is a good example of the type of analysis that can help reduce costs, improve profits and win more projects. According to GTM Research, the utility-scale solar market in the US will approach 12 GW in 2016. If each one of these large-scale projects could reduce eBOS costs by a half cent per watt, the industry as a whole would save $60 million.

Eric Every / Yaskawa–Solectria Solar / Lawrence, MA / solectria.com

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IHS Technology’s “PV Balance of System Equipment Report—2015” forecasts 9 GW of single-axis tracker installations worldwide in 2019, with the US the largest market, accounting for 36% of global single-axis tracker installations. The projected growth in the deployment of systems using horizontal single-axis trackers has focused the attention of existing manufacturers that are scaling their technologies for multimegawatt tracked PV plants and influenced manufacturers that have historically offered fixed racking systems to dedicate resources to tracker technology acquisition and development. This article presents manufacturer and equipment profiles that provide insight into the backgrounds, products and development efforts of ten companies that offer single-axis or dual-axis trackers for utility-scale and large commercial applications.

AllEarth Solar

Founded in 2008 by David Blittersdorf, AllEarth Solar is a privately held corporation headquartered in Williston, Vermont. Blittersdorf has a long history of entrepreneurship in the renewable energy industry and related fields. After receiving a mechanical engineering degree from the University of Vermont in 1981, he founded NRG Systems, a manufacturer of wind and solar resource assessment equipment. In 2004 Blittersdorf stepped down as CEO of NRG Systems to found AllEarth Renewables. Initially, the company’s focus was the development of residential and farm-scale wind turbines. However, the rapid decrease in PV module prices that was occurring at the time created a challenging market for grid-tied small-scale wind systems in the US. Due to these changing market dynamics, Blittersdorf decided to make a full-scale shift in AllEarth’s product focus and began developing dual-axis solar trackers in 2008. Five months later, AllEarth’s first tracker models were in production.

While integrators most often deploy AllEarth’s trackers in commercial and residential installations, they have also used the single-pole dual-axis tracker system in megawatt-scale projects, such as the 2.1 MW South Burlington Solar Farm commissioned in 2011 and the 2.2 MW Claire Solar Farm commissioned in October 2014. Both plants are located in South Burlington, Vermont. AllEarth served as the EPC firm for the Claire Solar Farm project and deployed 366 solar trackers on the site.

Unique aspects of the solar tracker include the way that AllEarth has designed all its components, with the exception of the pole, to fit on a single pallet, streamlining procurement and shipping. In addition, AllEarth typically packages the tracker as part of a pre-engineered system that includes modules, a string inverter and associated mounting hardware. AllEarth’s approach to distributed power processing, with a string inverter mounted to each tracker, is an early example of a shift toward decentralized power conditioning systems that utilize high-power string inverters rather than central inverters.

AllEarth trackers are compatible with precast or pour-in-place concrete, steel riser and helical pile foundations. The trackers are certified to ASCE 7–10 for 120 mph wind loads.  A 180 W hydraulic motor drives a ring/worm gear yaw drive (azimuth) with a 360° movement range. A hydraulic cylinder automatically adjusts the tracker’s tilt from 0° to 60°. A GPS-based microprocessor controller regulates both tracking mechanisms (azimuth and tilt). To protect the tracker during high-wind events, the system relies on an anemometer sensor and associated algorithm that stows the array flat when wind speed reaches 30 mph. The system includes wireless communication and visualization software for tracker plant management. AllEarth manufactures its trackers in the US, and they carry a 10-year warranty.

Array Technologies

Array Technologies (ATI) is a privately held company that has been manufacturing solar trackers in Albuquerque, New Mexico, since 1992. Its founder and CEO, Ron Corio, patented his first solar tracking system in 1990 while working for Wattsun. SolarPro’s publishing partner, Home Power, ran an early and very favorable review of Corio’s first dual-axis tracker in its October/November 1991 issue. The magazine’s publisher, Richard Perez, concluded, “I have never been excited enough by a PV tracker to install one in our system. The mechanical vagaries seemed to decrease the inherent reliability of the PV system. Wattsun has changed my mind. They have made a PV tracker we can rely on.” The reviewed tracker is still operational 26 years later (as are its eight Kyocera K51 modules).

ATI has continually evolved, redesigned and scaled its solar tracking equipment, systems and services in pace with the growth of the solar industry, especially with regard to the utility-scale PV plant market segment. Corio serves as the company’s chief engineer and is still actively involved in product engineering and development. Over the company’s history, ATI has delivered more than 4 GW of array tracking systems.

ATI currently offers single- and dual-axis DuraTrack pole-mounted trackers for residential and small commercial applications, as well as two models of DuraTrack single-axis horizontal trackers that are well suited to large residential and small commercial projects.

With a sharpened focus on multimegawatt utility-scale PV plants, ATI launched its third-generation DuraTrack HZ v3 horizontal single-axis tracker at Intersolar North America 2015 in San Francisco. The tracker features two-stage gearing and a flexible rotary drive shaft. Each 2 hp 3-phase 480 Vac motor can drive up to 28 rows of 80 c-Si modules each, with only two motors required per MWac. The DuraTrack HZ v3 minimizes driveline and module gaps to maximize array density and site utilization, while requiring half as many motors as the previous DuraTrack HZ v2.5 model.

The DuraTrack HZ v3 has an algorithm with a GPS input tracking method and a ±52° tracking range of motion with backtracking functionality. The system’s drivetrain has sealed gearboxes designed to be maintenance free for the life of the plant. The DuraTrack HZ v3 has a 135 mph 3-second gust exposure C (IBC 2012) allowable wind-load rating. A passive mechanical wind protection system that does not require power to operate protects the tracker during high-wind events and eliminates the maintenance requirements associated with active stow components.

Configurations for c-Si modules include one-up in portrait orientation, two-up in landscape orientation, and four-up in landscape for thin-film modules. To speed module deployment, ATI has developed a single-fastener module clamp with integrated grounding. The DuraTrack HZ v3 is certified to UL 2703 and to the UL 3703 standard for solar trackers. It has a 5-year parts-only warranty. A 10-year extended warranty is available.

Exosun

In 2007, Frédéric Conchy founded Exosun, a privately held French manufacturer of single-axis trackers for utility-scale PV plants and dual-axis trackers for concentrating PV modules. Conchy serves as the company’s president and CEO. Headquartered in Martillac, France, Exosun deployed the first tracked PV plant in France in 2008 for the French utility company EDF. Exosun established a US presence in 2012. Commissioned in 2014, the first US deployment of Exosun’s Exotrack HZ system is the San Bernardino County, California, 37 MW Lone Valley Solar Park, which Abengoa built and EDP Renewables owns. Exosun operates US offices in California and Arizona, and has partnered with North Carolina–based DCE Solar to provide a full range of fixed-tilt and tracking systems for utility-scale ground-mounted solar plants in the US.

Exosun’s Exotrack HZ V.2 trackers are available in 1,000 Vdc and 1,500 Vdc versions. The systems can drive up to 1 MWp of solar trackers with five 3-phase 400 Vac (CE) or 460 Vac (UL) sealed, maintenance-free brushless gear motors. Developers can effectively install the linked-row tracker systems on undulating sites with a grade variance of up to 10% (5.71°). The 1,000 Vdc model typically requires 450 piles per MW and the 1,500 Vdc model requires 555 piles per MW. The Exotrack HZ V.2 supports a one-up in portrait orientation module layout. Module mounting hardware consists of a proprietary clamp with integrated grounding. Electrically, designers typically configure the system with one source circuit per row, with up to 30 rows per tracker at 1,000 Vdc and 20 rows per tracker at 1,500 Vdc.

Exotrack HZ V.2 trackers have a ±50° tracking range of rotation. The system’s SMARTracking solar tracker program offers optimized array backtracking functionality, and its algorithms account for the worst-positioned module table on each individual tracker. In addition, the Exotrack HZ system’s software supports specific algorithms for each tracker. The tracker’s wind resistance specification is up to 62 mph in tracking mode and up to 125 mph in stow position. A high-wind version is also available. Exosun bases its control and monitoring platform on its Exobox product. Each Exobox can monitor and control up to 10 MWp of solar trackers.

One of Exosun’s goals for its tracker system was to streamline dc wire routing and management by optimizing the Exotrack HZ V.2 tracker design and the layout of the tracked array. The resulting system typically deploys rows of single source circuits and uses cable trays or slings to eliminate the civil work required for cable trenches. The system design allows mounting of a combiner box or 3-phase string inverter to each tracker.

Exosun’s Exotrack HZ V.2 trackers have a 5-year product warranty, a 10-year structural warranty and extended warranties of up to 20 years. Exosun supports its tracking system with a full suite of services that include project-specific design, project management, operations and maintenance, and training courses.

GameChange Solar

GameChange Solar (formerly GameChange Racking) offers a broad product portfolio for commercial and utility-scale PV plants that includes penetrating and ballasted ground mounts, roof mounts and, most recently, array tracking systems. Andrew Barron Worden launched the privately held corporation in 2012 and serves as its CEO. Worden also serves as the chairman, CEO and majority investor of Barron Partners, a global investment firm with a clean tech focus.

GameChange introduced its inaugural array tracking system, the linked-row Power Tracker, at Solar Power International 2015 in Anaheim, California. In 2016, the manufacturer refocused its tracker development efforts on an independent-row, single-axis horizontal tracker design, and in March it launched its Genius Tracker. The same month, GameChange announced two early 20 MW–plus projects that will deploy its new solar tracking system.

The horizontal single-axis Genius Tracker is compatible with slopes of up to ±6.5° north–south and ±9° east–west. The tracker design uses a self-powered linear actuator coupled with a 24 Vdc or 12 Vdc motor to drive up to 90 72-cell c-Si modules per actuator. Each drive actuator has a dedicated PV module, battery and wireless field-replaceable hot-swappable controller. GameChange estimates that the battery will provide 5 days of backup power. The system uses the ZigBee wireless standard to network the individual controllers. Remote communication functionality allows secure system monitoring and control.

The Genius Tracker supports layouts of one-up in portrait orientation for large-format 72-cell c-Si modules, and three- or four-up in landscape orientation for thin-film modules. GameChange offers attachment hardware for framed and double-glass modules, as well as both top and bottom module-mounting options. The tracker’s standard rotational range is ±45°, and a ±60° range is available. The Genius Tracker uses a tracking algorithm based on time and location that provides backtracking functionality. GameChange specifies a 150 mph wind-load rating for its Genius Tracker, and has designed it to stow automatically when wind speeds reach 70 mph.

GameChange Solar offers in-house structural, mechanical, civil and geotechnical engineering services; on-site field training and site supervision services; and turnkey installation services. A 5-year control and drive system warranty and a 10-year structural component warranty back the Genius Tracker. An extended warranty, for 10 years on the control and drive system and 20 years on the structural components, is also available.

Grupo Clavijo

Headquartered in Viana, Spain, Grupo Clavijo is a sole proprietorship founded in 1961. Initially the company was active in the agricultural sector, providing machinery for the processing and transportation of animal feed and facilities for the production of animal feed products. Today, in addition to serving the agricultural market segment, Grupo Calvijo provides products and services to renewable energy and industrial sectors. The group founded its renewable energy division in 2004, with a technical emphasis on solar array trackers and fixed mounting structures.

Grupo Clavijo currently offers two single-axis horizontal tracker models, a polar-aligned single-axis tracker, ten dual-axis trackers (36.7 m2–294 m2 array areas), and several options for single-pile and dual-pile fixed racking systems for utility-scale projects. Its SP1000 model horizontal tracker has a rotation range of ±45° and is compatible with site grade variations of up to 6% (3.43°). Clavijo has patented the maintenance-free 3D polyamide bearing used in its horizontal single-axis trackers. The tracker’s position control allows backtracking and includes protection against high-wind events.

Grupo Clavijo has over 1 GW of fixed-tilt and tracked arrays deployed worldwide, and is approaching 100 MW of installed tracking systems in the US, primarily in California. The group reports that it has approximately 400 MW in its US pipeline for 2016. US projects include the 18 MWdc Morelos del Sol PV plant in Lost Hills, California (see Project Profile, SolarPro, March/April 2016). Solar Frontier Americas Development developed the project, which comprises 11,744 Solar Frontier CIS thin-film modules on Clavijo trackers. Clavijo engineered a reinforced version of its SP1000 tracker to accommodate the Solar Frontier modules, which are mounted two-up in portrait orientation to maximize the output of each power block.

In addition to designing and manufacturing solar trackers and fixed array structures, Grupo Clavijo provides PV plant installation services and customized solutions. Additional services include topographical surveys, recommendations for optimum tracker positioning, shading analysis, customized monitoring and remote tracker control, and O&M. Clavijo’s single-axis horizontal trackers carry a 10-year structural warranty.

NEXTracker

PV industry veteran Dan Shugar has spent nearly three decades in entrepreneurial roles in the solar industry. He is a former president of both PowerLight and SunPower. Shugar founded his current company, NEXTracker, in 2013 and launched its first-generation Self-Powered Tracker for utility-scale and distributed-generation PV installations in 2014. Flex (formerly Flextronics) purchased NEXTracker in 2015, and now operates it as an independent subsidiary of the $26 billion design, engineering, manufacturing and logistics services company, which has over 100 manufacturing sites in more than 30 countries worldwide.

Since its launch in 2014, NEXTracker’s self-powered, independent-row horizontal single-axis tracker platform has proven to be a disruptive technology in the utility-scale tracker market segment. Independent-row trackers can optimize land use on irregularly shaped and discontinuous project sites, and typically offer greater flexibility than linked-tracker designs for sites with significant slopes and topographical variability.

NEXTracker’s current tracker model is the NX Horizon. Each tracker’s slew gear drive system includes a 24 Vdc motor and self-powered controller (SPC) with a dedicated solar panel. A wireless ZigBee mesh network and NEXTracker’s Network Control Unit (NCU) eliminate the need for communication wiring in the array field. A single NCU can control up to 100 SPCs. The tracker’s range of motion is ±60°.

A typical NX Horizon configuration for 72-cell c-Si modules comprises independent rows of 80 modules mounted in portrait orientation. The resulting capacity per row is 23 kWdc–35 kWdc depending on module type. The tracker is compatible with all standard foundation types, including driven pier, ground screws and concrete footings. The NX Horizon’s standard wind-design load is 100 mph 3-second gust per ASCE 7-10, and the tracker is configurable for higher wind loads. The controller also provides automated wind and snow stowing. Torsional limiters provide additional wind- and snow-load protection. NEXTracker also offers optional snow and flood sensors for additional solar asset protection. The NX Horizon has a 10-year warranty on structural components and a 5-year warranty on drive and control systems.

The NX Horizon is ETL certified to the UL 2703 standard, and in January 2016 it achieved ETL certification to UL 3703. The UL 3703 standard allows the certification of tracker functions including those that protect against electric shock, as well as mechanical and fire hazards. The standard also certifies the NX Horizon’s ability to self-ground through existing structural components without requiring additional dedicated grounding components such as grounding washers or straps. NEXTracker notes that the UL 3703 certification covers the NX Horizon’s maximum system voltage of 1,500 Vdc.

In December 2015, NEXTracker announced its NX Fusion ac power system, which integrates its NX Horizon tracker with high-power string inverters, dc wiring harnesses, an uninterruptible power supply, piers, and a tracker monitoring and control system, as well as c-Si and thin-film PV module options. The system also includes on-site weather stations that initiate the safe stowing of trackers when they detect high wind speeds. The NX Fusion component package offers project developers a pre-engineered, repeatable tracker power block.

Schletter

Privately held Schletter GmbH has a 40-year history in the design and manufacture of steel and aluminum products. The manufacturer has been active in the solar industry for more than 20 years. Schletter founded its US subsidiary in 2008 with the launch of a sales and manufacturing facility in Tucson, Arizona. In 2012, it relocated its US headquarters to Shelby, North Carolina. Its product portfolio includes an extensive lineup of fixed solar mounting structures for carports, rooftops and ground-mounted PV systems.

Schletter introduced the US version of its FS Track-2 horizontal single-axis tracker at Intersolar North America 2015 in San Francisco. The tracker utilizes a standard industrial 1.5 kWac motor, available with several voltage ranges for compatibility with the electrical requirements of various project sites. The motor powers a linear actuator that can drive up to 16 rows of 40 modules per actuator. Depending on site and system design characteristics, the FS Track-2 tracker typically requires five or six motors per MW of array field. The tracker uses spherical bearings that do not require lubrication and has a range of motion of ±45° or ±55° standard. Schletter also offers additional tracker range-of-motion options to meet specific PV plant requirements. The FS Track-2 uses a solar vector tracking method with backtracking functionality.

The Schletter FS Track-2 has a north–south slope tolerance of 3° standard and up to 8° when deployed with Schletter’s sloped terrain set. The tracker’s east–west slope tolerance is 3° standard. Array table options include a one-up module layout in portrait orientation and a two-up module layout in landscape orientation. The FS Track-2 is compatible with most commercially available modules. Schletter tailors the engineering of its single-axis tracker system to meet the wind load requirements of specific sites, with solutions for allowable wind loads up to IBC 3-second gust speed of 180 mph, exposure C.

Schletter provides full in-house engineering services, which include geotechnical testing such as vertical pull-out tests, lateral load tests and independent laboratory analysis of soil classification, corrosion potential, gradation and soil plasticity. The manufacturer also offers foundation and tracker installation, motor and controls installation, and ongoing PV plant O&M. Schletter’s FS Track-2 solar tracker has a 12-month warranty on the system’s electrical controls, a 36-month warranty on electrical drive components and a 5-year warranty on the tracker’s structural steel components, with the exception of bearings and rotational shafts.

Solar FlexRack

Headquartered in Youngstown, Ohio, Solar FlexRack is a division of privately held Northern States Metals, a designer and manufacturer of extruded aluminum industrial products. In 1997, the company diversified and began to manufacture PV module frames, and in 2008 it started producing aluminum PV mounting clamps. In 2009, Northern States Metals launched its solar racking division, Solar FlexRack, with a focus on commercial and utility-scale racking systems. One of Solar FlexRack’s inaugural products was a factory-assembled array table that installers would expand on-site. The innovative product was an early example of manufacturers’ efforts to develop preassembled racking system components that reduced installation labor cost in the field. In 2011 Northern States Metals acquired OPEL Technologies’ single-axis solar tracker and redesigned it from the ground up. Solar FlexRack launched the newly designed single-axis horizontal TDP Turnkey Tracker in December 2015.

The company based the TDP Turnkey Tracker on a decentralized, independent row design that can maximize PV generation capacity. It does so by allowing array layouts that optimize utilization of irregular and nonadjacent project lots. Each tracker uses an ac-powered controller and a linear actuator coupled with a 24 Vdc motor to drive up to 60 c-Si modules in a one-up portrait-orientation table configuration. The individual controllers communicate via a ZigBee wireless mesh network. The TDP Turnkey Tracker is compatible with most module types. Foundation options include Solar FlexRack’s SFR Smart Post and I-beam piles. The TDP tracker uses an algorithm with a GPS input tracking method that includes backtracking functionality. The device’s tracking range is ±45°.

Solar FlexRack’s path to market for the TDP tracker bundles its tracker technology with a full suite of services and support for commercial and utility-scale solar clients. With a staff of mechanical, structural, civil, electrical and geotechnical engineers, Solar FlexRack offers services including array sizing and layout, pull testing, structural analysis and foundation design, project management, installation, commissioning and project O&M. Solar FlexRack’s TDP Turnkey Tracker has standard warranties of 10 years on structural steel and 5 years on electronics, linear actuators and motors.

Soltec Renewable Energies

Headquartered in Molina de Segura, Spain, with a US office in Fremont, California, privately held Soltec Renewable Energies was founded in 2004. Soltec’s flagship product is its SF Utility single-axis horizontal tracker. In December 2015, Soltec America increased its US presence with the opening of an Innovation Center in Fremont, California. The facility serves as a central location for the manufacturer’s North American research and development efforts, as well as a regional base for sales, engineering and logistics for Soltec America. In addition to developing and manufacturing trackers, Soltec offers services such as PV plant engineering; project planning and management; supply logistics; construction supervision and management; and utility-scale PV system installation, commissioning and O&M.

In January 2016, Soltec announced the certification of its SF Utility tracker to the UL 3703 standard for solar trackers. The single-axis horizontal tracker has a driveline-free independent row design. The tracker typically requires only 275 piles per MW of array and is compatible with single-pile, micropile and ground-screw foundations. The SF Utility tracker has a north–south slope tolerance of 17% (9.65°). The tracker’s independent row design makes the east–west slope tolerance virtually unlimited, apart from the construction limits a site’s specific topography may impose. The tracker’s rotational range is ±60° and its tracking algorithm includes backtracking functionality.

The SF Utility tracker has a maximum PV module area of 1,937.5 square feet. Module table configuration options for the tracker include two-up, three-up and four-up in landscape orientation and two-up in portrait orientation. The tracker’s controller includes an internal universal power supply with two configurations. The ac-powered configuration uses an ac/dc power supply to drive the tracker’s 24 Vdc motor. The PV-powered configuration uses a dc-to-dc converter to power the tracker’s controller, 24 Vdc motor, and control and monitoring backup battery directly from one of the array’s source circuits.

A wireless mesh network provides networked communication and control of the individual tracker controllers while allowing asymmetrical and independent tracker operation to optimize PV plant power generation. The SF Utility tracker system includes proprietary source-circuit combiner boxes as well as integrated conductor management. The tracker has maintenance-free self-lubricated bearings. A face-to-face cleaning mode facilitates array cleaning and associated maintenance activities. Soltec’s SF Utility tracker system has a standard 10-year structural warranty and standard 5-year warranties on the system’s motors and electronics, with additional extended warranty options.

SunLink

Founded in 2004, SunLink played a pioneering role in the introduction of ballasted racking systems for large-scale commercial and industrial arrays on low-slope rooftops. Since then, the privately held San Rafael, California–based company has diversified its product line to include ground-mount racking systems for large-scale arrays and BOS components such as disconnecting source-circuit combiners. Most recently, SunLink added an array tracking system for utility-scale and distributed PV plants and its VERTEX project intelligence platform to its product portfolio. Also, with the introduction of its PowerCare program, SunLink expanded service offerings to include project engineering and management, geotechnical services, turnkey installation, and PV asset O&M. Promoted from his position as SunLink’s COO to president and CEO in 2015, Michael Maulick is the driving force behind SunLink’s ongoing transformation from a racking-only manufacturer to a full-service solar solutions provider.

SunLink finalized the acquisition of the single-axis horizontal G10 Quantum tracker from Tempe, Arizona–based ViaSol Energy Solutions in March 2015. ViaSol first introduced the linked-array tracking system in 2008 and had deployed 75 MW at the time of SunLink’s acquisition. The centralized tracking system drives up to 1.2 MW per drive, and its design leverages the use of proven hydraulic technology from standardized industrial automation equipment, streamlining both parts availability and access to qualified technicians in diverse global solar markets.

SunLink’s current TechTrack horizontal single-axis tracker is an evolution of the ViaSol tracker design. On the generation side, SunLink increased the tracker’s range of motion to ±52.5 degrees to improve its generation capacity in high-irradiance environments. It also redesigned the tracker’s torque tube splice. The new one-piece splice clamp design eliminates 1,000 bolts per MW. A new module rail offers reduced material costs while maintaining the module manufacturer’s warranties.

Compatible with all major module brands, the TechTrack horizontal single-axis tracker is designed for a one-up portrait layout. A single hydraulic drive coupled with a 3-phase 480 Vac motor can track up to 62 rows of 60 modules in many wind environments. The tracker’s PLC-based controller utilizes industrial automation components. Its tracking method utilizes NASA’s time and location algorithm. The monitoring and control system provides wind speed and direction, tilt angle and GPS sensors, and customers can expand it to include up to 512 digital and 56 analog sensors.

The TechTrack has a standard wind rating of 105 mph and is configurable to 150 mph with no snow load or 120 mph with snow loading of up to 50 psf. The stow algorithm includes wind-stow and snow-shedding functions. SunLink’s centralized TechTrack solar tracker has a 10-year mechanical and structural warranty and a 5-year controls and actuator warranty. Extended warranty options are available.

SunLink supports its TechTrack solar tracker system via its PowerCare services and VERTEX platform. This secure SCADA and performance monitoring system allows portfolio managers to monitor and control the performance of all projects in a portfolio, regardless of original SCADA or data monitoring implementation, and to facilitate the optimization of PV plant O&M activities. VERTEX enables remote project control capabilities, alerts, data analytics and performance trends, as well as O&M dispatch and scheduling.

CONTACT:

Joe Schwartz / SolarPro / Ashland, OR / solarprofessional.com

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Part 1: Site Grading and Design Optimization

By Samuel Laughlin and Bill Reaugh

When developers consider a piece of land for a large-scale ground-mounted PV power generation asset, the costs for grading and earthwork can be significant drivers of project viability. The project developer’s or owner’s goals determine in part when, where and how much to grade. These decisions must also fit the requirements of the site with respect to AHJ controls and the mechanical limitations of the equipment the developer may use. 

The best approach to this puzzle is one that integrates a holistic view for these requirements across multiple engineering disciplines, including civil, structural, electrical, mechanical and geotechnical, and water resources. A few of the first questions to ask are: How does the topography behave? Is the proposed equipment capable of dealing with the site in its current state or are modifications required? If the requisite site modifications are significant, are there other solutions that align better with the project’s financial goals?

To Grade or Not to Grade

Grading typically includes two major activities: cutting, the process of removing quantities of soil, and filling, the process of building up quantities of soil. Ideally, the amount of soil imported to or exported from the site is near zero to reduce both costs and environmental impacts.

The needs and conditions of the land underlying the solar array structure make each project unique. Depending on site conditions and construction requirements, a piece of land may need no preparation, minor surface clearing and grubbing of subsurface plant roots, smooth grading or full grading. Generally speaking, developers perform grading because the site requires it or because doing so will support plant optimization.

GRADING REQUIRED

In certain circumstances grading is unavoidable. The most common reasons for grading are to meet AHJ requirements or best practices for access roads or storm water management. Grading may also be required to conform to vendor-specified mechanical tolerances for the mounting system.

On-site access roads. AHJs and industry best practices dictate minimum and maximum slopes for access roads, as well as compaction and surface maintenance requirements. Grading is required where the existing topography does not meet these longitudinal or cross-slope requirements. While the local fire department typically has the final say on access roads, the local building department or the site owner may also have applicable requirements.

Storm water management. Site-specific hydrologic characteristics are a critical factor in determining grading requirements and plant design. If a site lies in a flood zone, for example, the flood depth determines the minimum height for electrical equipment. Storm-induced runoff and scour affect minimum pile embedment depths. The contributing watersheds and historical water flows may dictate detention basins or improvements to the existing storm water channels. Local environmental agencies may have requirements related to dust or water quality that impact these grading activities.

Mechanical tolerances. In general, fixed-tilt mounting systems are more capable of dealing with topographical changes across a site than are single-axis trackers. However, many large-scale ground-mounted systems use trackers to maximize energy production from the available land area. Trackers have a maximum slope (% grade) associated with the north-south axis of the torque tube and, if applicable, the east-west elevation of the driveline. Should existing slopes fail to accommodate the maximum slopes of the torque tubes or drivelines, grading is one possible solution.

While tracker equipment manufacturers specify maximum slope values, installation guidelines or product datasheets do not always provide these design criteria. Instead, some manufacturers provide a grading requirements document or similar reference upon request that details civil engineering needs for sites. This document provides information about mechanical tolerances to help engineers determine project-specific design criteria, including maximum slopes and maximum and minimum pile elevations above grade.

GRADING FOR OPTIMIZATION

Site preparation impacts solar power plant optimization in a variety of ways. For instance, minimizing the amount of steel in the foundation or the time required to wash the modules can offer potential benefits. Maximizing the ground-cover ratio (MW/acre) or specific energy yield (MWh/MW) can also yield benefits. Rather than focus on a single variable, a well-integrated engineering effort develops the best result holistically by evaluating all these variables in concert with the goal of achieving the lowest levelized cost of energy.

Steel piles. A combination of subsurface soil conditions, torque tube height requirements, tracker reaction forces on the pile and terrain variation determines the amount of steel required for driven pile foundations. The higher the torque tube height, the more steel the project requires. The larger the terrain variation from one end of a tracker row to the other, the more steel the project requires. Strategic grading has the potential to compensate for both of these conditions. For example, grading to channel water across the site can reduce flood depths and equipment height, whereas smooth grading can compact soils or minimize terrain variations. 

When optimizing a pile foundation plan, the design team generally seeks to minimize the total amount of steel the client must purchase or to optimize logistics by minimizing the total number of pile types and lengths. The former activity reduces the material cost for the steel, while the latter reduces the cost to transport and distribute piles across the site.

Soil volume. Another optimization variable for the design team to consider is the volume of soil that heavy equipment will need to move around the site. On one hand, reducing the required amount of earthwork has the advantage of speeding up the site preparation time, which allows the contractor to start installing equipment sooner. It is also beneficial to reduce site disturbance in areas that have the potential for below-grade archaeological or paleontological resources. On the other hand, minimizing earthworks could limit the area of land available for modules and other electrical equipment or increase the total amount of steel required. If the design must space rows further apart to account for terrain features, that restriction reduces ground-cover ratios.

Operations and maintenance. Site designers should also consider the amount and type of O&M activities required to keep a solar project operating optimally. For example, it may be beneficial to use a ground-cover ratio that allows maintenance personnel to wash two rows of modules at the same time. In addition, locating serviceable equipment—especially combiner boxes, inverters and transformers—close to maintenance roads makes O&M activities more efficient.

Available area. The design team also can employ multiple site or soil preparation variables to maximize the available land area for PV modules. These include placing detention basins under PV array fields, strategically routing storm water, developing flood-control channels, leveling hills and filling valleys, and so forth. Whereas locating detention basins below tracker arrays tends to increase the torque tube height and the required amount of foundation steel, smooth site grading generally allows the use of shorter piles. Further, more-extensive earthwork and site preparation activities lead to higher levels of pre- and post-construction monitoring for environmental quality impacts.

Specific yield. The goal of optimization exercises is to maximize the energy harvest per unit of installed power. For instance, the design team might adjust the ground-cover ratio or increase site slopes to increase the amount of incident sunlight. The potential downside is that more-extensive site preparation activities tend to increase grading costs.

Part 2: Ground Mounts on Landfills

By Bryan Morrison

Over the past 20 years, towns, municipalities and other entities have closed and capped nearly 6,000 landfills. Since the land at the majority of these sites is contaminated or contains remediated soils, they are not suitable for typical residential or commercial uses. However, these capped landfills can still provide value for municipalities as host sites for ground-mounted PV power plants.

A capped landfill typically becomes an expense for the community, requiring annual maintenance and continual monitoring. By leasing the land for PV project development, municipalities can recover maintenance and monitoring costs as well as generate revenue. Project developers also benefit because these tracts of land are often offered at exceptionally low lease rates compared to land suitable for commercial development.

To capitalize on the low cost of land, however, project developers need to address some unusual design challenges and unique risks associated with deploying a ground-mounted PV power plant over a landfill cap.

GROUND MOUNTS ON LANDFILLS

The first thing that project developers must consider is the construction of the landfill itself.

Landfill cap. Several different types of landfill cap designs appear in the US. Modern-day landfills commonly feature a Standard Subtitle D Cover cap design, as shown in Figure 1. This type of cap uses either a high-density polyethylene (HDPE) or a linear low-density polyethylene (LLDPE) geomembrane liner in concert with several layers of sand, soil and vegetation. A 12- to 18-inch drainage layer and a 6-inch soil layer are commonly found above the liner. The thickness of these layers determines the allowable bearing pressure on the liner.

A Standard Subtitle D Cover landfill cap provides allowable temporary bearing pressures (for vehicular traffic) of up to 7 pounds per square inch (psi) and permanent bearing pressures of up to 5 psi. Allowable bearing pressures dictate foundation designs for mounting systems and other equipment, as well as access road designs for plant construction and maintenance. Bearing pressure also determines what types of vehicles can safely operate on top of the landfill. Since a damaged or punctured membrane would be costly to repair and would cause significant project delays, bearing pressure is an extremely important design consideration.

Storm water management. Landfills are designed to maximize municipal solid waste storage capacity and therefore result in large dome-shaped plateaus with steep side slopes. Given these terrain features and the minimal amount of cover material, storm water runoff is another critical PV system design consideration. Landfills rely heavily on both vegetation and drainage swales to manage storm water and prevent erosion. It can be extremely costly and time consuming to modify these existing storm water management features to accommodate a PV system.

Gas vents. PV system designers also need to consider landfill maintenance features such as gas vents, settlement plates and monitoring wells. It is especially important for installers to pay attention to gas vent locations. Since a large percentage of the gas emitted from a landfill is either methane or carbon dioxide, workers in the proximity of a passive vent risk exposure to flammable gas or a zero-oxygen environment. Landfill gas can also contain ammonia and hydrogen sulfide, both of which can cause a variety of respiratory issues. Since landfill vents often emit odorless gasses, workers need to rope off vent pipes in close proximity to the PV array to ensure that no one accidentally gets too close to these vents. To prevent gas from migrating into enclosures, workers should locate electrical equipment away from landfill vents. Smoking is prohibited when working on a landfill.

Vegetation control. Mowing is the most common form of routine landfill maintenance. If certain species of trees, shrubs or brush are allowed to grow on the landfill, their root systems will eventually penetrate the geomembrane liner. Regular mowing prevents this from happening. When preparing a PV array layout for a landfill, designers need to understand and consider how maintenance personnel mow the site and ensure that all sections of the landfill remain accessible to the mowing equipment.

Fencing. Many existing landfills are already fenced, and some of these fences require only minor modifications to comply with National Electrical Code requirements. Unfenced landfills can present significant design and budgetary challenges. The landfill membrane often extends for many acres beyond the usable array area. Fencing this long perimeter is a costly and time-consuming proposition. More often than not, project developers need to contend with wetlands located at the perimeter of the landfill that could require additional permits through local conservation committees, extending the project mobilization timeline. If it is not practical to build a conventional fence, system designers can consider adding a ballasted fence at the array boundary, provided they factor the fence location into the array layout.

PV SYSTEM CONSIDERATIONS

After taking landfill design into account, project developers need to adapt their PV system design and installation practices to the site.

Build from the vegetation up. It is a good idea to hire a site contractor who has experience with landfill closures or making landfill repairs. Given the minimal amount of material above the geomembrane liner, the most productive design and construction strategy is to build the PV system up from the vegetation layer. This means that the array foundations, equipment pads, electrical infrastructure and access roads are all installed above grade. The goal of this design approach is to maintain the existing protection of the cap and to preserve the functionality of existing storm water controls.

Prior to commencing construction activities, an authorized agent should inspect the existing landfill conditions to ensure that both the gas vents and storm water controls are intact and that no depressions due to settlement exist. The developer needs to remedy any depressions under the supervision of the AHJ prior to construction. During construction, crews need to immediately remediate any ruts or divots caused by construction traffic and weather events. The contractor can alternate construction activities among different areas or project phases to allow the protective layers of the landfill to dry out between weather events or while the crew is repairing them in an effort to minimize project delay.

Road layout. The first step in the design process is to determine the proper location of the construction road. Placing the access road along the spine (the highest points) of the landfill reduces or minimizes impacts to existing storm water controls. If space and landfill topography permits, it is ideal to have a road entering one side of a landfill and exiting the other, as this is beneficial for project logistics and project velocity. At a minimum, PV designers need to provide a sufficient number of turnarounds to accommodate construction traffic and material delivery.

Array layout. Designers determine the usable array area flanking the access road based on the slope of the terrain and the mechanical tolerance of the mounting system. Since ballasted mounting systems are susceptible to sliding forces and constrained by the allowable bearing pressure on the landfill cap, these systems are commonly limited to a 5°–7° slope. Once designers have identified existing landfill features and areas with acceptable slopes, they can begin to lay out the array, keeping in mind maintenance activities and cap protection.

Mounting system selection. Developers also must consider differential settlement when designing this type of system. As the landfill decomposes, the surface naturally settles differentially due to the varying types of material decomposing below. Landfills will settle 10–20 feet over their lifetime, and settlement of 1 foot per year in the first years of closure is common.

To tolerate this settlement, designers should use a statically determinate mounting structure that they can analyze using static equations of equilibrium to determine reaction forces. A structural design with two foundations per array table that allows for future in-field adjustment is generally best for withstanding settlement over the life of a system. By comparison, a structural design with three or more foundations may be subject to intolerable stresses that result in module deflection and possible destruction.

Cable tray. Landfill projects have unique electrical infrastructure requirements in two ways: The design needs to account for settlement, and the site has insufficient cover material to allow burial of conduit or cables. Since landfill applications require an above-grade solution, designers typically specify cable tray. Cable tray comes in 10- or 12-foot sections that installers do not have to physically connect to one another, so it can tolerate differential settlement, provided the conductors offer adequate slack.

Each cable tray section generally has four independent height-adjustable feet, allowing for installation on uneven ground. The base area for these feet is often adequate to disperse the weight of the cable tray and conductors, as well as keep the point loads below the maximum allowable bearing pressure. As an added benefit, cable tray remains visible to the landscaping crew even when the grass grows tall between mowings, and physically protects the electrical cables from both mowers and string trimmers.

Electrical equipment pad. As is the case with typical ground-mounted systems, centralizing the location of the inverters offers cost and performance benefits. The optimal location is typically somewhere along the access road near the center of the array. The shoulder of the access road serves as a means of bringing in the medium- or high-voltage circuit to the distribution transformer from the point of common coupling. Since the road is subject to both vehicular traffic and differential settlement, system designers generally call for a reinforced concrete duct bank to protect these circuits.

Concrete equipment pads for landfill applications may have to be quite large, given the extreme weight of the electrical equipment and the relatively low allowable bearing pressure. A typical 1 MW liquid-filled medium-voltage transformer usually weighs more than 1,000 pounds. In many cases, it makes sense to install a single reinforced concrete equipment pad that supports all of the equipment, rather than multiple smaller concrete pads, as the larger pad will save preparation and installation time. Using a single pad also protects the conductors against damage due to differential settlement, since the single pad will move uniformly as a single unit.

System grounding. Opting for a single equipment pad also provides a means for system grounding. Given the shallow depth of the landfill cover material, it is obviously not possible to install an 8- or 10-foot ground rod as a grounding electrode. Instead, a copper ground ring with supplemental copper grounding plates typically offers adequate system grounding. The thickness of the concrete pad, plus the depth of the fill material beneath it, provide the burial depth required for the ground ring.

Part 3: Bonding and Grounding

By Marvin Hamon, PE

To provide a safe PV system, designers and installers need to understand the fundamentals of bonding and grounding. Whereas proper bonding ensures that a ground-mounted PV array is free from stray shock hazards for the life of the system, proper grounding prevents dangerous voltage differentials between the PV array and the ground on which installers or service technicians stand. Since people often confuse these terms and practices, here I define each individually, consider its intent, and review hardware options and installation methods.

BONDING

Per the definition in Article 100 of the National Electrical Code, equipment is bonded when it is “connected to establish electrical continuity and conductivity.” Employing an equipment-grounding conductor (EGC) is one way to make this low-impedance connection. Another way is to make a mechanical connection by, for instance, bolting two pieces of conductive material together.

Intent. As described in NEC Section 250.4, bonding establishes a low-impedance connection between conductive equipment and materials to conduct fault current safely and minimize potential voltage differences between conductive components. By providing a low-impedance path for line-to-line or line-to-ground faults, the designer ensures that fault currents quickly rise to a level that activates an overcurrent or ground-fault protection device.

Hardware. In the 1990s and early 2000s, installers used thread-forming screws, UL-listed grounding lugs and bare copper EGCs to connect all the conductive parts of a ground-mounted PV system. While straightforward and easy to verify during inspection, this bonding method is also relatively expensive. It requires a lot of lugs and copper, and it is time-consuming to implement in the field. In other words, this approach is not well suited to deploying PV systems at low prices and high volumes.

About a decade ago, companies such as Wiley Electronics (now Burndy) introduced specialized bonding clips for PV applications to address this pain point. These products have sharp or serrated surfaces that bond the exposed metal module frames and other electrical equipment to the metal mounting structure during installation. Though these new bonding products allowed quick and easy installation, some AHJs and industry stakeholders were skeptical that they could effectively replace conventional hardware and copper EGCs. These (often single-use) components also make system inspection challenging since they are invisible once installed.

UL convened a Standards Technical Panel to develop the UL 2703 product safety standard—which covers PV module-mounting systems, clamping devices and ground lugs—in part to address these concerns about effective bonding. Mounting systems listed to this standard include bonding components designed to establish electrical conductivity between PV modules and other electrical equipment connected to metal racks. Further, a Nationally Recognized Testing Laboratory has certified the efficacy of these bonding connections.

EGC sizing. NEC Table 250.122 provides guidance for identifying the minimum allowable EGC size. But, many people fail to read the note that states the following: “Where necessary to comply with 250.4(A)(5) or (B)(4), the equipment-grounding conductor shall be sized larger than given in this table.” In other words, choosing a conductor based on Table 250.122 is no guarantee that the design will provide an effective path for fault currents. However, the NEC offers no further guidance about how to upsize an EGC.

Engineers need to account for a number of variables—incident energy ratings, available fault currents, overcurrent protection device (OCPD) time-current characteristics and so forth—to ensure that a fault will not damage an EGC. Fortunately, the unique electrical characteristics of PV systems work in their favor. For example, the available fault current in a PV array is much less than that from even the smallest utility service; the maximum fault current from a 500 kW PV array might be 1,000 A, whereas a 600 A utility service might easily have an available fault current of 50,000 A or greater. Conductors can carry a high amount of current for a short time without incurring damage. Therefore, Table 250.122 is very conservative for the purposes of PV array design. In most applications, a 10-gauge EGC is more than adequate.

Table 250.122 also provides installers and inspectors with a convenient basis of comparison for UL 2703–listed PV mounting systems, which should be bonded at least as well as those bonded with an EGC. As a quick bonding test, for instance, an installer could take a resistance reading between two points in an array, such as between one row of modules and an adjacent row. Assuming that these module rows are 100 feet long and spaced 10 feet apart, the installer should see a resistance reading equivalent to 210 feet of 10 AWG copper. According to NEC Chapter 9, Table 8, which details conductor properties, a single-strand 10 AWG copper conductor has a resistance of 1.21 mΩ per foot. So if the row-to-row resistance measurement is in the vicinity of 254 mΩ (210 feet x 1.21 mΩ/foot), that suggests the equipment is properly bonded. A significantly higher reading means a poor mechanical connection somewhere in the path probably needs correction.

Maintenance. It is not that difficult to create a good electrical bond in a new mounting system. The challenge is maintaining that connection over time in an outside environment. This is precisely why PV designers need to specify UL-listed equipment and assemblies, as UL product safety standards define test procedures intended to determine how bonded connections will age. While measuring bonding resistance during system commissioning is important, it does not indicate what the resistance will be after 6 months or 10 years in the field. Therefore, O&M providers should review bonding resistance as part of their scheduled maintenance activities.

GROUNDING

Per NEC Article 100, equipment is grounded when it is “connected to ground [the earth] or to a conductive body that extends the ground connection.” A grounding electrode establishes the actual connection to ground. A grounding electrode conductor extends the ground connection to the EGC or the conductive equipment.

Intent. Grounding is sometimes referred to as earthing, since it ensures that conductive equipment is at the same electrical potential (voltage) as the earth. Eliminating voltage difference between ground and conductive surfaces such as PV module frames and mounting systems mitigates shock and fire hazards. As long as the aluminum frames and steel racks, for example, are at earth potential, electrical current will not flow to ground through a person who is installing or servicing the array. In this scenario, the source of the voltage difference could be a cross-connection fault with another power system—perhaps an overhead power line falling onto a PV array—or a lightning strike. Proper setup of a ground-mounted array prevents any shock to service personnel because they will never provide the best electrical connection to earth.

In the field. Normally an electrical system is grounded at one point only: the point of supply. This connection to ground might be located at the utility service entrance or on the secondary side of a transformer. The Code also requires a connection to ground on the dc side of transformer-isolated inverters. However, this single-point approach to grounding can cause problems in large-scale ground-mounted PV systems, where the farthest reaches of the PV array may be located a great distance from the grounding electrode system.

While designers can extend the grounding electrode system throughout the PV array with buried electrodes—as is done with substations—this is very expensive. Alternatively, NEC Section 250.54 allows the use of auxiliary grounding electrodes, which do not have to comply with electrode-bonding requirements. The steel foundation members often serve as auxiliary grounding electrodes. Section 250.52 covers electrodes permitted for grounding. Ground-mounted PV array foundations may comply with Subsections 250.52(2) or (3), depending on whether the system uses driven piles or posts embedded in concrete. Designers can increase the overall connection to earth in a ground-mounted PV system by specifying a foundation with one or more posts per array table or row of modules that qualifies as a grounding electrode.

Some in the PV industry feel that auxiliary grounding electrodes can actually make a PV system less safe in areas prone to lightning strikes. When lightning strikes the ground, localized voltage increases in the earth but normally dissipates over time. If there are auxiliary grounding electrodes in the area of increased voltage, however, the voltage rise can cause current flow up one auxiliary grounding electrode through the PV array and out the nearest auxiliary grounding electrode that is at a lower voltage, which could put people or equipment in harm’s way. In a grounding electrode system, the buried bonding jumpers that connect each of the individual grounding electrodes into a single system would carry this current below the surface of the earth.

[Editor’s note: For information on system grounding, which is a design consideration not covered here, see “Grounding Compendium for PV Systems,” SolarPro, April/May 2013.]

Part 4: Scalable Mounting Solutions

By Keith Beisner and Sara Jacobs

The increased rate of solar adoption is opening up new markets to solar providers and ramping up project volumes. Developers, EPC firms and solar providers are seeing an increased number of project opportunities as well as a wider range of project sizes across their portfolios. In addition, the solar industry’s footprint is expanding into all regions of the US, from the remotest rural areas to the tightest urban spaces.

Rapid market expansion means that solar solution providers must streamline their designs across a wide range of environmental conditions. Solar installers have to be prepared to deal with variable surface and subsurface conditions. At the same time, the industry is under great pressure to lower costs. These realities require new solutions. Solar providers and EPC firms require a new generation of efficient, cost-effective solutions that enable them to better react and adapt. 

MASS CUSTOMIZATION

The key to making solar happen in more places while driving costs down lies in having a mounting-system design that is centered upon built-in environmental adaptability, construction flexibility and predictable costs. Developing customized solutions on a site-specific basis is not a scalable strategy. Instead, the industry needs racking systems composed of standard components that installers can assemble in a variety of ways to meet each project’s unique challenges. This mass customization approach will allow the industry to accelerate most rapidly because it is both highly configurable and cost effective.

Foundation design. Installers need different foundation options to avoid costly delays caused by variable soil conditions and unpredictable subsurface obstructions within a project portfolio. To achieve economies of scale, however, it is essential that these foundation options be part of a standardized product solution. Taking the need for foundation flexibility a step further, soil conditions can vary dramatically within a site, meaning even a single project may require a range of optimal foundations. The key is to provide a range of standardized foundation options that developers can easily interchange without having a negative impact on the overall system design or aesthetics.

If project developers discover the need for diverse foundations during the engineering design phase or preconstruction pull tests, mass customization allows designers to optimally specify different foundation types before construction starts. Often, though, EPC firms do not discover these soil variations until installation work is already in progress. When installers must quickly react to problems without a ready-made solution on hand, delays and escalating costs are the norm.

Product designs that allow for swap-in foundation changes can equip installers to make on-the-fly changes during construction without incurring high costs for replacement parts and project delays. For example, if installers hit a refusal while driving a post on-site, they might quickly swap in a cast-in-place ballasted foundation on top of the soil while utilizing the same superstructure. Readily available and interchangeable foundation options can help eliminate expensive in-field modifications.

Mounting structure. When it comes to the racking structure itself, mass-customized solutions provide design flexibility to accommodate project variations, including different modules, terrains, and wind or snow loads. Although 72-cell modules are the de facto standard on ground-mount projects, each module frame has its own distinct set of mounting dimensions. Mounting systems that are adaptable to different modules without component modification eliminate the need for last-minute change orders.

Similarly, standardized products with terrain-following capabilities reduce not only site preparation and installation time, but also PV system cost and complexity. In recent years, the scope of projects has grown to include not only flat, level and prepared sites but also more-challenging sites with undulating slopes or hilly terrain. Mounting systems that installers can deploy without making major site improvements or modifications can reduce preconstruction civil work and improve project economics.

As solar projects expand into regions with higher wind and snow loads, mounting systems must also adapt to these environmental conditions. Standardizing products to accommodate higher loads without the need for custom components simplifies both the design and the supply chain processes. This simplification allows optimal project delivery timelines and improved cost efficiencies.

Soft costs. Beyond material costs, mass customization also shaves project soft costs. Many developers and customers are seeking better-integrated electrical and mechanical designs across their project portfolios. Mounting solutions with standardized table sizes—such as two-high in portrait configuration—make this integration possible. Different foundation configuration options, meanwhile, can accommodate changing environmental factors while keeping other variables, including table size and mechanical and electrical components, consistent across multiple project sites. Standardizing these mechanical and electrical design processes can lower costs and increase engineering efficiency while allowing for easy preparation, installation and O&M.

THE DOMINO EFFECT

A domino effect begins to take place when product design and engineering become more efficient. Solar providers, large and small, can take on more projects in more locations. While these growth factors place a high demand on materials, mass customization also streamlines supply chains. It allows companies to inventory components and reduce lead times. It accommodates short-notice schedule or design changes. This adaptability is critical to companies with aggressive and sometimes simultaneous or competing construction schedules.

Furthermore, the ability to use the same system and components on all sites, regardless of environmental and site conditions, allows installers to implement best practices more consistently and can dramatically improve installation efficiencies. On-site crews learn to quickly troubleshoot unpredictable situations and implement rapid, cost-effective mitigation solutions while also reducing punch lists and mitigation work.

With the combined advantages of mass customization, solar providers gain maximum efficiency and achieve economies of scale across projects of all sizes. Mass customization reduces costs and allows rapid growth in nonresidential markets where ground mounts are typically deployed. The result is more successful solar projects and a faster technology adoption trajectory.

Contact:

Keith Beisner / SunLink / San Rafael, CA / sunlink.com

Marvin Hamon / Hamon Engineering / Alameda, CA / hamonengineering.com

Sara Jacobs / SunLink / San Rafael, CA / sunlink.com

Samuel Laughlin / Blue Oak Energy / Davis, CA / blueoakenergy.com

Bryan Morrison / Borrego Solar / Lowell, MA / borregosolar.com

Bill Reaugh / Blue Oak Energy / Davis, CA / blueoakenergy.com

Primary Category: 
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More and more vendors are offering dual-tilt mounting systems, which orient modules in undulating east-west or even north-south rows. Is this the wave of the future? 

Module-mounting strategies have evolved over time. In the early to mid 2000s, for example, it was common for designers to tilt modules at latitude. This approach optimized specific yield (kWh/kW), ensuring that the modules were as productive as possible. This design approach made sense when the modules constituted the most expensive part of a PV system. As module costs have declined, however, so have module tilt angles.

The industry movement toward lower tilt angles was first evident on commercial rooftops. To optimize energy production in this space-constrained setting, designers have long opted to reduce array tilt and tighten array spacing to fit more modules per square foot. For example, PowerLight (now SunPower) began volume production on its flat-tilt PowerGuard solution for commercial rooftops in September 1999. Although this high-power–density design approach predates the era of low-cost PV modules, it is especially well suited to optimizing financial performance at the system level rather than specific yield at the module level. 

Dual-tilt mounting systems are a continuation of this trend in low-slope rooftop applications. Lower-cost PV modules incentivize designs that maximize roof coverage ratios and installed PV capacity while minimizing shade and soiling effects. This design philosophy gave birth to dual-tilt mounting systems that allow for high-power densities on rooftops with minimal self-shading as well as arrays that are self-cleaning during rain events. However, since south-facing PV arrays have been the de facto industry standard on commercial rooftops in North America for many years, system designers may initially be confused by dual-tilt mounting approaches or even suspicious of vendor performance claims.

In this article, we analyze the pros and cons of dual-tilt mounting systems for low-slope roofs, providing quantitative examples of how this design strategy differs from traditional approaches. We illustrate how to use an economic model to evaluate the financial performance of dual-tilt versus south-facing designs. Based on these results, we describe how and where designers can deploy dual-tilt systems most effectively. In the event that this design approach is ideal for projects you are developing, we provide a brief overview of vendors offering dual-tilt mounting systems in North America.

Evaluating the Dual-Tilt Value Proposition

The first step in evaluating dual-tilt mounting is to understand the trade-offs associated with this design approach, some of which Table 1 details. Some of the potential benefits that vendors tout (such as increased power density) are self-evident, whereas designers need to model and analyze others (such as time of delivery [TOD] gains). Most important, a decrease in specific yield relative to south-facing arrays tempers the potential benefits of dual-tilt arrays.

Power density. Traditional south-facing fixed-tilt mounting systems for low-slope roofs require a gap between rows of modules to prevent interrow shading. The width of this gap represents a trade-off between power density and module productivity. Interrow spacing typically ranges between 1 and 3 feet on rooftop systems. It is much larger on ground-mounted systems, which tend to have tall array tables.

By contrast, dual-tilt mounting systems orient modules in a “wave” pattern that inherently mitigates self-shading effects. Since there is no need for additional interrow shading allowances, most dual-tilt systems simply have rows at regular intervals to accommodate system maintenance. In most cases, dual-tilt mounts have a narrow gap only at the peak of each ridge to facilitate airflow around the modules and equalize pressure differentials associated with wind loads.

As a result of this fundamental design difference, dual-tilt arrays typically have a core ground coverage ratio (not counting obstructions or walkways) of approximately 0.9. By comparison, south-facing fixed-tilt arrays typically have core ground coverage ratios in the 0.5–0.8 range. This means that designers can increase system capacity 15%–35% by using a dual-tilt rather than a traditional south-facing design approach.

Specific yield. While power is an important variable in terms of a PV system’s economic performance, reduced energy yield per unit of power offsets capacity gains with a dual-tilt array. Though dual-tilt arrays are less sensitive to azimuth than traditional fixed-tilt arrays, vendors typically advertise these products as east-west mounting solutions. Not surprisingly, an array that has half of its modules facing east and half facing west will generate fewer kilowatt-hours per kilowatt than an array that has all of its modules facing south. This reduction in specific yield is a simple function of the lower average annual irradiance in the plane of the dual-tilt array.

The plane-of-array irradiance reductions associated with dual-tilt mounting vary based on site latitude and reference array tilt. As illustrated in Table 2, the farther a dual-tilt installation is from the equator, the larger the performance penalty relative to a south-facing array. The amount that an east-west array underperforms relative to a south-facing array also varies based on the array tilt of the reference design. For the cities we analyzed in Table 2, an east-west array underperforms a south-facing array with a 10° tilt by 6%–10%; that performance penalty increases to 9%–16% in relation to a reference array with a 20° tilt.

In addition to plane-of-array irradiance losses, dual-tilt mounting systems also experience secondary irradiance losses, including reflective and low-light losses. Reflective losses increase when sunlight strikes a module at a shallower incidence angle. Since an east-west array experiences shallower sun angles than a south-facing array, its reflective losses increase by 0.5%–1%. In addition, PV modules are less efficient at lower light levels, and an east-west array experiences an additional 0.1%–0.3% of loss due to low-light losses. Taken together, the secondary irradiance losses in an east-west array account for system losses of roughly 1% compared to a south-facing array.

Dual-tilt mounting systems sacrifice irradiance by design. While improved power density is the most obvious trade-off, this design approach also has a number of other system-level benefits. There are significant benefits associated with the aerodynamic performance of an east-west array, and there may be additional benefits associated with the time of year or day that a dual-tilt array produces energy or power.

Material and labor costs. Many low-slope mounting systems use a combination of wind deflectors and ballast blocks to resist wind loads. By contrast, each module in a dual-tilt system acts as a wind deflector for the module at its back. This means that dual-tilt mounting systems eliminate both the labor and the material costs associated with installing traditional wind deflectors.

Dual-tilt designs can reduce total component counts further by sharing components between rows. In addition, the back-to-back rows of modules tend to both reduce wind loads and distribute uplift forces. Because dual-tilt systems are both aerodynamic and structurally interconnected, they typically require fewer ballast blocks compared to traditional fixed-tilt arrays. Since there are fewer parts to install and the rows share some parts, dual-tilt systems also improve installation efficiencies in the field.

Dual-tilt mounting systems can reduce material and labor costs compared to traditional low-slope mounting systems in a few ways. While cost savings vary based on product platform, crew experience and basis of comparison, our interviews with vendors—all of which sell both dual-tilt and conventional south-facing mounting systems—indicate that dual-tilt solutions offer cost savings of $0.02–$0.07 per watt.

Weight. Another benefit of improved aerodynamic performance and reduced ballast requirements is that rail-based dual-tilt arrays weigh less per unit of power than conventional ballasted fixed-tilt arrays. This may allow integrators to deploy a ballasted solution on low-weight– bearing rooftops, such as warehouse roofs. It may also allow for the installation of more PV capacity than would be possible with a traditional ballasted solution. In these weight-constrained situations, designers must pay careful attention to roof-loading limits. While dual-tilt arrays weigh less than traditional fixed-tilt arrays on a pounds-per-kilowatt basis, they also allow designers to install more kilowatts per square foot. As a result of this increased power density, some dual-tilt solutions or configurations could actually increase net roof loading on a pounds-per-square-foot basis.

Energy production. While dual-tilt arrays have a lower specific yield than comparable south-facing arrays, improved power densities offset these irradiance losses. As a result, dual-tilt arrays can generate more energy per rooftop than south-facing arrays. Figure 1, for example, provides a comparison of installed capacity, specific yield and total energy production in a space-constrained application for an east-west versus a south-facing array configuration, assuming that interrow spacing for the south-facing arrays varies based on latitude.

Time of delivery. Simply comparing total energy generation between a dual-tilt and a south-facing array does not always tell the whole story. As illustrated in Figure 2a, an east-west array can produce more energy on summer afternoons than an equivalent south-facing array on a low-slope rooftop. Further, the total energy an east-west array produces during summer months compares favorably to the output of a south-facing array.

Since east-west arrays perform well in the summer and generate more energy later in the day, they potentially provide more value than a south-facing array under TOD rate structures. These potential benefits vary based on how the utility has defined its TOD periods and factors (multipliers). In a TOD regime weighted specifically toward summer afternoons, an east-west array can generate 2%–3% more value over the course of a year than a south-facing array with a 20° tilt. In a TOD regime that also emphasizes on-peak (afternoon) production in the winter, an east-west array might provide little to no additional benefit.

Figure 2b provides examples of these scenarios. The SCE 2006 TOD and PG&E A6 rate structures, which specifically emphasize on-peak production in the summer, are favorable for east-west arrays. The PG&E 2006 TOD rate structure, however, provides a negligible net benefit, since it also includes an on-peak multiplier in winter, when east-west productivity suffers.

Inverter limiting. In the previous examples, we intentionally used conservative design assumptions, limiting the dc-to-ac sizing ratio of the systems we modeled to a maximum of 1.2 to minimize inverter power limiting. In practice, however, integrators are increasingly deploying systems with high dc-to-ac ratios. (See “Optimizing Array-to-Inverter Power Ratio,” SolarPro, October/November 2014.) In high-loading scenarios, the peak of the inverter output power curve is more likely to be clipped at peak-production times of the day or year when the array is capable of delivering more power than the inverter can export.

Because a dual-tilt array is not pointed toward the equator, it is less likely to operate at high-power levels than a south-facing array, which means that the peak of its power curve is lower. This squatter production curve means that the inverter power-limiting losses are lower for a dual-tilt array, assuming the same dc-to-ac sizing ratio. As detailed in Figure 3, a 1.35 array-to-inverter ratio results in inverter power limiting losses of 1.5% for a south-facing array versus 0.5% for an east-west array. Put another way, the dc-to-ac ratio for an east-west array can be 5%–10% larger than that of a south-facing array and still have the same inverter power-limiting losses. Therefore, designers can use a dual-tilt approach to reduce either inverter power-limiting losses or inverter capacity.

Our modeling results support vendor claims that dual-tilt arrays can make more efficient use of inverter capacity. However, we found no evidence that an inverter itself operates any more efficiently—based on voltage or loading levels—when connected to an east-west array.

Economic Analysis

Economic performance at the system level is the ultimate measure of value for a dual-tilt mounting system. On the one hand, designers can use a dual-tilt mounting system to increase array capacity by 15%–35%. On the other, a dual-tilt design approach nominally decreases specific yield by 4%–12%, depending on location, though TOD and inverter power-limiting factors may offset some of these irradiance yield losses. In addition, hardware utilization improvements, including potential inverter cost reductions, may reduce installed costs by $0.02–$0.08 per watt. Given the complexity of the factors involved, we need to use a site- and system-specific economic model to holistically understand the impact of using a dual-tilt array versus a conventional south-facing array.

Table 3 compares key economic indicators for two potential array designs for a 43,000-square-foot rooftop in Charlotte, North Carolina. To define the reference systems, we used Folsom Lab’s HelioScope software to calculate the array capacity for a south-facing PV array and for an east-west–oriented PV array, assuming a 10° tilt for both systems. Based on its ability to perform component-level analyses, we also used HelioScope to model energy production for these two systems. After defining system energy production, we used the System Advisor Model (SAM) from the National Renewable Energy Laboratory to model economic performance over time. For the inputs to the SAM model, we assumed fixed costs of $0.81 per watt, marginal costs of $1.64 per watt, an energy value of $0.15/kWh, a 7% discount rate and a useful system life of 25 years.

Looking at the data in Table 3, it is striking that an east-west design increases system capacity by 32%, yet increases total cost by only 20%. The explanation for this is improved fixed-cost amortization. There are always fixed costs associated with deploying a PV array. These include sales, design, administration, management and permitting costs, in addition to the costs of acquiring an interconnection agreement or executing a power purchase agreement. Even within a single line item for labor, such as electrical installation, some overhead components are relatively independent of system size, such as travel to the site and site preparation. To the extent that we increase system capacity, we decrease these fixed costs on a dollars-per-watt basis. Further, if the smaller-capacity system was already profitable, then increasing capacity results in more profit for all parties in the value chain, including the customer, the system integrator and the equipment vendors.

In this example, the real value of the east-west design option is that it increases the project’s net present value (NPV), which compares the up-front investment costs to the present value of future revenues. While this 51% increase in NPV is significant, the east-west array actually has a slightly lower levelized cost of energy (LCOE). The LCOE is lower because reduced specific yield largely offsets the better fixed-cost amortization.

Effective Deployment

While some projects may benefit from a dual-tilt design approach, others may not. So where and how can designers deploy these systems most effectively? The key considerations fall into three main categories: site selection, system design and operations.

SITE SELECTION

Deploying dual-tilt mounting systems effectively requires knowing where these systems provide the most benefit and where they present additional design or installation challenges. Space-constrained roofs, for example, are well suited to a dual-tilt design approach. However, roofs with a large number of obstructions may make this design approach more challenging. Site latitude and array azimuth can also sway design decisions.

Space-constrained roofs. At many commercial and industrial sites, the customer’s electrical loads far exceed the power-generating capability of the rooftop. Where this is the case, a dual-tilt design approach is generally beneficial, since it increases the rooftop power density and productivity in terms of energy production per unit of area. If an array is not space constrained, a dual-tilt design is more difficult to justify. Such scenarios includes sites where electrical load or customer budget rather than available roof area limit array capacity.

Roof obstructions. Most dual-tilt mounting systems require that designers add modules two at a time to limit wind loads. This can create problems on some rooftops. If a dual-tilt mounting system does not allow you to remove one module at a time to accommodate a small obstruction, then you will need to remove two modules at a time. This can make dual-tilt mounting systems comparatively less attractive on rooftops with a significant number of obstructions than on rooftops with few obstructions.

Site latitude. While the specific yield for dual-tilt arrays decreases at higher latitudes, as illustrated in Table 2, the same dynamic impacts south-facing arrays, albeit to a lesser degree. Depending on the interrow spacing of your south-facing reference system, a dual-tilt array can also significantly increase power density, which favors this design approach. Because of these opposing dynamics, it is impossible to generalize about whether a dual-tilt design approach is always better or worse based on latitude. However, designers should bear in mind that the results of an economic analysis vary from one location to another, especially if the site latitudes are different. The magnitude of variation is significant enough that site latitude can make or break a dual-tilt design.

Array azimuth. One of the interesting characteristics of dual-tilt arrays is that their performance is relatively insensitive to changes in array azimuth. As illustrated in Figure 4, a dual-tilt array essentially produces as much energy in an east-west orientation as it does in a north-south orientation. Some designers have concerns about deploying dual-tilt arrays on roofs that do not have a south-facing azimuth, since a portion of the array will necessarily face in a northern direction. However, the relative performance of a dual-tilt array generally improves in off-azimuth applications, because standard fixed-tilt array production suffers. Designers do need to be aware that wind loads increase when they design a dual-tilt array off azimuth.

SYSTEM DESIGN

After selecting an appropriate site, consider product and system design features, both mechanical and electrical.

Tilt angle. Most dual-tilt mounting systems orient PV modules at a 10° tilt angle. Exceptions in Table 4 are Mounting Systems’ Lambda Light EW+ (10° or 15°), SolarCity’s ZS Peak solution (8°) and tenKsolar’s DUO (25° south and 16° north). All else being equal, the performance of an east-west array with an 8° tilt versus a 10° tilt is not significantly different. At the system level, the lower tilt angle may improve aerodynamics and allow lower roof loading, while the higher tilt angle may decrease soiling losses. The only real outlier in terms of array tilt angle is the DUO product line from tenKsolar, which has significantly higher tilt angles and is designed specifically for a north-south orientation. By using a matrix of series and parallel connections in its modules, tenKsolar is able to increase system shade tolerance, which allows for the platform’s unique mechanical characteristics.

Rail-based vs. non–rail-based systems. Broadly speaking, there are two categories of low-slope mounting systems: rail-based and non–rail-based systems. In a rail-based system, modules mount on top of rails that run perpendicular to the array; these rails are the roof interface and provide some structure to the mechanical system. In a non–rail-based system, modules mount on feet or posts; this configuration means that the module frame provides some structure to the mechanical system. Non–rail-based systems have cost advantages, as they minimize hardware and materials. Rail-based systems may have structural advantages in high-wind areas. To the extent that non–rail-based systems place more load on the module frame, designers need to ensure that the module is capable of withstanding this additional load.

Module-mounting points. Compared to conventional rail-based mounting systems, dual-tilt products often locate mounting points closer to the corner of the module. This is significant because a module’s maximum permissible load allowance may vary based on mounting point location. System designers may need to verify that modules are compatible with dual-tilt mounting systems. This verification could be as simple as checking a website or contacting an applications engineer, as these mounting system vendors typically maintain an approved module list.

Inverter selection and array wiring. Dual-MPPT or multi-MPPT 3-phase string inverters are ideal for dual-tilt applications. Because these arrays face in two different directions, designers and installers need to ensure that the array is wired in a way that dedicates separate MPPT channels to these opposite array orientations. Splitting the array between MPPT channels in this manner minimizes mismatch losses. However, it also increases design and installation complexity. For example, installers may need to use jumpers between rows to complete source circuits without mixing array orientations.

Inverter capacity. Because a dual-tilt array has a squatter power curve than a south-facing array, designers can increase the dc-to-ac ratio in these systems. This approach can reduce installed inverter capacity by as much as 5%–10%, which reduces total inverter costs on a dollars-per-watt basis.

OPERATIONS

After designing the system, consider whether the dual-tilt array will present any unique challenges from a commissioning or maintenance perspective.

More and more vendors are offering dual-tilt mounting systems, which orient modules in undulating east-west or even north-south rows. Is this the wave of the future?

Commissioning. If installers mix module orientations within the same source-circuit or MPPT zone, mismatch losses can increase by as much as 6% or 7%. While this is a relatively easy mistake to make on a dual-tilt array, it is also easy to spot with an I-V curve tracer. Therefore, the site commissioning process may call for additional I-V curve tracing.

Access paths. Because a dual-tilt design approach increases packing density on the roof, access pathways are relatively narrower or less frequent. This could increase the cost of both scheduled and unscheduled maintenance activities—such as module cleaning or replacement—throughout the project lifetime. Note that cleaning schedules are largely a function of array tilt and rainfall. There is no reason to assume that cleaning requirements will change based on orientation only.

Inventory management. Some vendors use many of the same parts in their dual-tilt mounting systems as in their single-tilt mounting systems, whereas others sell products with unique parts and components.

RIDING THE WAVE

In space-constrained applications, system economics favor low module-tilt angles and high rooftop-packing densities. This is especially true when module prices are low, as they have been for several years. Therefore, it behooves designers to understand the potential benefits of dual-tilt mounting systems. In the right applications, this design approach can help deliver larger and more profitable arrays, which ultimately contributes to the sustained growth of the industry.

Table 4 provides an overview of mounting system vendors with dual-tilt products for low-slope roof applications in North America. Companies such as Aerocompact, Everest, Mounting Systems, Renusol and S:FLEX originally developed their products in Europe, where dual-tilt mounting systems are already fairly common. A few North American companies—including Orion Solar Racking, PanelClaw, SolarCity (Zep Solar), SunPower and tenKsolar—also now offer dual-tilt solutions. Look for more dual-tilt mounting systems in the future as other vendors start to ride this wave.

CONTACT:

Paul Gibbs / Folsom Labs / San Francisco / folsomlabs.com

Paul Grana / Folsom Labs / San Francisco / folsomlabs.com

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The large-scale ground-mount installation market segment presents tremendous opportunities. In U.S. Solar Market Insight Report: 2014 Year in Review, GTM Research and the Solar Energy Industries Association (SEIA) project 8.1 GW of new PV capacity in 2015 and forecast that large-scale ground-mount installations will comprise approximately 5 GW of that. However, the development of large-scale ground-mounted PV power plants has become increasingly competitive and cost sensitive. These pressures have been driving changes in racking system design, materials and deployment.

Racking systems for commercial and utility PV plants are just that—systems. Effective designs balance materials and manufacturing cost, component count and shipping cost with speed of installation, adjustability for varied site terrain and foundations, and, of course, durability. For this article, I researched the wide range of ground-mount racking vendors and product lines that are available to project developers and integrators in the US. I include background information on the vendors themselves and overviews of their solutions for commercial and utility array fields. With a few exceptions, all the products presented here are scalable for large projects.

AP Alternatives

AP Alternatives / 419.267.5280 / apalternatives.com

Headquartered in Ridgeville Corners, Ohio, AP Alternatives was founded in 2008 and launched its racking systems and related services in 2010. Its offerings include UL-listed racking system design and manufacture, as well as preassembly services intended to improve quality control and decrease installation time in the field. AP Alternatives’ mobile assembly lines can be moved anywhere in the US and set up to prepanelize modules on racking cartridges or sections. Depending on the model, each cartridge uses helical anchors, four posts (individual cartridges share adjacent east-west posts) and stainless steel cable bracing to support four 60-cell (MOD 60), three 72-cell (MOD 72) or 10 thin-film (MOD FS) modules. AP Alternatives’ GPS-guided anchor drivers can simultaneously drive two posts (north and south). Modules are electrically bonded during prepanelization, and a prewiring option is available. AP Alternatives also operates a separate division, Ready Rack, that offers racking systems for commercial and utility projects where field assembly is preferred over preassembly.

Applied Energy Technologies (AET)

Applied Energy Technologies (AET) / 586.466.5073 / aetenergy.com

A division of The Applied Group, AET was founded in 2009 and is headquartered in Clinton Township, Michigan. Its racking product family includes UL 2703–listed pitched roof and ballasted flat-roof systems. AET’s solution for ground-mounted commercial and utility PV plants is the Rayport-G Eco ground mount. AET designed the system to use a single row of driven posts for anchoring, but helical- and screw-pile foundations, as well as a ballasted option, are also available. Installers mount modules in two-high portrait orientation, and an adjustable plate installed between the post and strut allows for ¾-inch height adjustment per post. A brace installed between the post and strut provides structural rigidity to the racking system. Top-down clamps offer integrated module-to-racking system electrical bonding to the requirements of UL 2703. AET provides a full layout and loading analysis for each Rayport-G Eco ground-mount project.

Brilliant Rack

Brilliant Rack / 678.280.7453 / brilliantrack.com

Lilburn, Georgia–based Cantsink launched Brilliant Rack in 2014. Cantsink dates back to 1988, when it originally served as a foundation repair specialist for residential and commercial projects. It developed a manufacturing division in 2000 to produce helical piles for foundation stabilization. In 2010, the company shifted its core focus and manufacturing facility to anchoring systems for large-scale ground-mounted PV projects. Brilliant Rack is introducing a turnkey UL 2703–certified racking solution that is compatible with Cantsink’s helical piles, as well as driven piles and ground screws. The galvanized steel racking system uses a single-row post system in conjunction with a tilt beam (strut) and brace for a triangulated structural configuration. To simplify installation, the assembly process requires only two bolt sizes and a single nut and washer size. Brilliant Rack’s design includes three-axis installation tolerance and is compatible with east-west grades of up to 10%. Brilliant Rack also offers geotechnical testing, engineering and installation services.

DCE Solar

DCE Solar / 704.659.7474 / dcesolar.com

The Daetwyler Group designated DCE Solar as a specialized division within the Daetwyler Clean Energy family of companies in 2015 and established its headquarters in Huntersville, North Carolina. Worldwide, the Daetwyler Group is involved in high-precision machine engineering, including a focus on the design, manufacture and support of products for the printing industry. DCE Solar offers rooftop and parking canopy array-mounting solutions, as well as several variations of its Modu-Rack ground-mount system. The Modu-Rack product has galvanized steel structural members and DCE Solar designed it to facilitate module prepanelization. Modu-Rack model variations include single-row and dual-row post configurations and anchoring systems such as helical and driven piles, micropiles, and soil and rock anchors. DCE Solar’s ground-mount product portfolio also includes two racking systems, the Cap-Rack driven-beam system and the Cap-Rack ballasted system, developed for landfills and other contaminated sites that do not allow for ground disturbance.

DPW Solar

DPW Solar / 505.889.3585 / dpwsolar.com

Headquartered in Albuquerque, New Mexico, DPW Solar was founded in 1993 as Direct Power and Water. The PV racking system provider is currently a wholly owned subsidiary of Preformed Line Products, a component designer and supplier for industries that include communications and energy. DPW Solar has an extensive line of roof-, pole- and ground-mount PV racking products. The most recent addition to its ground mount line is the Power Peak large-scale ground mount system. Intended for commercial and utility PV plants, the Power Peak combines a galvanized steel driven-pile anchoring system with preassembled aluminum assemblies that include the rack’s strongback, strut and rail brackets. Installers unfold the assemblies on-site and attach them to the vertical piles via adjustable galvanized steel attachment brackets. DPW manufactures the rails from aluminum extrusions that include built-in wire channels. DPW Solar’s factory-preassembled RAD module clamps provide a built-in electrical grounding option.

GameChange Racking

GameChange Racking / 212.359.0205 / gamechangeracking.com

Launched in 2011, GameChange Racking is owned by Barron Group Holding and headquartered in New York. It offers a full line of PV racking products that include roof mounts, carport structures, and anchored and ballasted ground mounts. Two recent additions to GameChange’s ground-mount line include the Max-Span post system and GC Pour-In-Place ballasted system. The Max-Span ground mount’s structural members are galvanized steel. To reduce parts count and streamline installation, the system features nested components with slotted attachment points, eliminating the need for separate brackets to connect the main structural members. The Max-Span system’s direct purlin mount option enables an 8% east-west grade, while its purlin bracket mount option enables an east-west grade of up to 17%. For landfill or brownfield sites, the GC Pour-In-Place ballasted system uses leave-behind recycled high molecular weight polyethylene (HMWPE) plastic forms that installers fill with concrete on-site.

IronRidge

IronRidge / 800.227.9523 / ironridge.com

Headquartered in Hayward, California, IronRidge was founded in 1996. The company’s racking family includes fixed and ballasted products for rooftop array mounting, as well as pole mounts and ground mounts. Its Ground Mount product for commercial and industrial systems combines IronRidge’s XR1000 aluminum rail with installer-supplied 2- or 3-inch Schedule 40 galvanized steel pipe. The system uses connectors with U-bolt attachments between the racking system’s rails, cross-pipes (purlins) and vertical piers. IronRidge’s Ground Mount is compatible with a variety of foundation options, including concrete piers and driven piles. It can support up to five modules per column in landscape orientation. The XR1000 rails allow for spans of up to 17 feet between east-west foundation piers.

Mounting Systems

Mounting Systems / 855.731.9996 / mounting-systems.us

Founded in 2010, West Sacramento, California–based Mounting Systems is the US affiliate of Mounting Systems, GmbH, headquartered in Rangsdorf, Germany. In January 2015, Mounting Systems GmbH expanded via the acquisition of racking manufacturer HatiCon Germany GmbH and its US affiliate, HatiCon Solar, from Sapa, a global aluminum solutions provider. Mounting Systems’ product portfolio provides mounting solutions for pitched and low-slope roofs as well as three ground-mount products for open-field commercial and utility PV arrays. Its Sigma I product is a single-row system that features a custom galvanized steel driven-micropile anchoring system. The Sigma I XL product combines a single-row anchoring system with aluminum rails to enable large-format array configurations of up to four-module columns in landscape orientation. The Sigma II product is a two-post system that can be anchored with driven micropiles, helical piles or footplates on ballast. Sigma II’s use of micropiles instead of large beam-type piles allows the use of smaller, less expensive hydraulic driving equipment and simplifies material transport and handling.

MT Solar

MT Solar / 844.687.6527 / mtsolar.us

MT Solar is a small, privately held racking system manufacturer located in Charlo, Montana. While its products fall outside the general scope of this article (racking solutions that installers can efficiently scale for large commercial and utility projects), its Solar Pole Mount system features a unique design that integrators should be aware of for ground-mounted small commercial and residential installations. MT Solar has designed its Solar Pole Mount system for waist-level array assembly and wiring, and it features a manual and removable hoist system that raises the array to top-of-post level. The innovative design eliminates the need for cranes for preassembled array lifting and placement, scaffolding for pole-top mount assembly or overhead work from ladders during array installation. Additionally, installers can fully adjust the mounts from 0° to 90° by twisting a crank from the ground. Single-pole models designed to support two to 12 modules are available, as are larger multipole models for higher-capacity, continuous pole-top arrays.

Patriot Solar Group

Patriot Solar Group / 517.629.9292 / patriotsolargroup.com

Founded in 2006, Patriot Solar Group (PSG) is a privately held company headquartered in Albion, Michigan. The origins of the company date back to 2006 when it was involved in the telecommunications industry and operated as Patriot Antenna Systems. PSG manufactures rooftop, carport and ground-mount racking systems, as well as dual-axis trackers and portable stand-alone power systems. PSG’s solutions for commercial and utility systems include its Post Driven Ground Mount and Ballasted Ground Mount products. Foundation options for the galvanized steel Post Driven Ground Mount include driven piles, helical piles, screw piles and concrete piers. The single-post system is built in five-module sections with modules in a single row in portrait orientation. This system is unique in that its adjustable trusses connect to the driven posts and allow for tilt angles ranging from 10° to 40°. PSG’s Ballasted Ground Mount also supports five modules in portrait orientation, and it relies on two 1,850-pound precast concrete ballast blocks per racking section for anchoring.

Polar Racking

Polar Racking / 844.860.6722 / polarracking.com

Headquartered in Toronto, with US offices in New York, Polar Racking’s product family includes solutions for residential, commercial and utility rooftop and ground-mount applications. Polar Racking offers eight configurations of its PRU utility-scale ground mount. Compatible foundation types include helical and driven piles, micropiles, ground screws and ballasted options. The galvanized steel racking system is available in single- and dual-post models that use either round or flat (rectangular) post types. The system has east-west and north-south adjustability of ±2 inches. Polar Racking offers models for both landscape and portrait module orientation, and custom array tilt angles from 5° to 35°. The PRU systems’ mid-clamps provide integrated grounding. Prepanelized module options are also available for the PRU racking systems.

PV Racking

PV Racking / 610.990.7199 / pvracking.us

Founded in 2010, PV Racking is headquartered in Southampton, Pennsylvania. A manufacturer of racking systems for roof-, ground- and carport-mounted arrays, the company is unique in that it offers a slide-in module mounting design. Instead of the typical use of top-down module mounting clamps, PV Racking’s aluminum rail profile allows installers to slide modules into place, where they are held securely as installers place successive rails and module rows. The manufacturer recommends the use of DynoBond jumpers manufactured by DynoRaxx for module-to-rail electrical bonding. PV Racking’s Ground Mount system is typically anchored with galvanized steel helical piers that also serve as the main posts for the racking structure. Five rail profiles accommodate module frame thicknesses of 1.16–2 inches. PV Racking’s design allows for portrait or landscape module orientation at tilt angles of 5° and higher.

RBI Solar

RBI Solar / 513.242.2051 / rbisolar.com

RBI Solar is a privately held provider of solar racking solutions headquartered in Cincinnati. It operates additional US offices in Washington, North Carolina, as well as a facility in Temecula, California, which opened in 2015. The company made two notable acquisitions in 2014, including PV carport manufacturer and installer ProtekPark Solar, and Renusol GmbH and its subsidiary, Renusol America, providers of rooftop mounting solutions that include HMWPE ballasted mounts. The Renusol acquisition adds the Renusol GS, a nonpenetrating ballasted one-piece mounting system for ground-mount applications, to RBI Solar’s product portfolio. Intended for sites such as landfills and brownfields, the Renusol GS accommodates 72-cell modules at a 10° tilt angle. RBI Solar also offers a range of all-steel ground mounts that it developed for large commercial and utility-scale projects. Its GM-I and GM-T ground-mount products are listed to the UL 2703 standard and can be configured for portrait or landscape module orientations with tilt angles of 0°–45°. Foundation options include concrete piers, precast or cast-in-place concrete ballast, driven posts, and screw or helical piles.

Schletter

Schletter / 888.608.0234 / schletter.us

Privately held Schletter GmbH has a 40-year history in the design and manufacture of steel and aluminum products; it has been active in the solar industry for approximately 20 years. The company founded its US subsidiary in 2008 with the launch of a sales and manufacturing facility in Tucson, Arizona. In 2012, Schletter relocated its US headquarters to Shelby, North Carolina. Its product portfolio includes mounting structures for carports, roofs and ground-mounted PV systems. Schletter designed its fully ballasted PvMax system for commercial and utility PV projects on landfill or brownfield sites. It uses a cast-in-place ballast system and arrives partially preassembled to speed installation time. The aluminum PvMax system is available in several configurations for portrait and module orientations and layouts. Schletter’s ETL-classified FS System uses a galvanized steel single-row driven-pile anchoring system and aluminum upper-racking components. The system features a high level of preassembly and integrated module-to-rail grounding. Schletter’s all-steel ground-mount model is the FS Uno. Like the FS System, the FS Uno uses single-row driven pile anchoring and arrives partially preassembled. Connector hooks connect module rails to the rack substructure, and a unique mid- and end-clamp design allows installers to mount modules anywhere along the rails. Schletter offers engineering support and geotechnical testing services, and is also the exclusive North American distributor of the GAYK Hydraulic Ram pile driver.

S:FLEX

S:Flex / 303.522.3974 / sflex.com

With its global headquarters in Hamburg, Germany, privately held S:FLEX GmbH was founded in 2009 and has its US headquarters in Denver. S:FLEX’s racking-system portfolio includes solutions for pitched and low-slope roof-, carport- and ground-mount applications. Its Ground Mount System product line supports both portrait and landscape module layouts, as well as framed or frameless modules, at an array tilt angle of up to 45°. Preassembled parts include height-adjustable, click-in module clamps. The dual-post racking structures are compatible with driven pile, helical pier, ground screw and embedded-in-concrete anchoring. Sites with a maximum east-west terrain slope of 8° can utilize the system, and it provides 12 inches of vertical adjustability on-site with no cutting or welding.

Solar FlexRack

Solar FlexRack / 888.380.8138 / solarflexrack.com

Headquartered in Youngstown, Ohio, Solar FlexRack is a division of privately held Northern States Metals, a designer and manufacturer of extruded aluminum industrial products. In 1997, the company diversified and began to manufacture PV module frames, eventually producing aluminum PV mounting clamps in 2008. In 2009, Northern States Metals launched its solar racking division. Solar FlexRack designs products with partially preassembled structural components that installers can expand or unfold on-site to reduce labor costs for large-scale PV plants. Solar FlexRack’s Series G3-L is also an all-steel, single-post racking system. The company ships the vertical and horizontal rack components to the jobsite as a fully assembled unit. To meet the requirements of projects that prioritize material cost savings over labor savings, Solar FlexRack’s new all-steel Series G3-X model ships with less preassembly than its G3-L model. The G3-X is Solar FlexRack’s most cost-effective solution. It is value engineered to optimize materials, components and fasteners. Solar FlexRack has streamlined the all-steel system for field assembly, permitting easy staging on the jobsite. The G3-X is compatible with all standard foundation types, and built-in tolerances allow the system to adjust to varying topographies and challenging terrain. Integrated bonding and wire management round out the G3-X system. Solar FlexRack offers pullout testing, as well as geotechnical, engineering and turnkey installation services.

SunLink

SunLink / 415.925.9650 / sunlink.com

Founded in 2004, SunLink had a pioneering role in the introduction of ballasted racking systems for large-scale commercial and industrial arrays on low-slope rooftops. Since then, the privately held San Rafael, California–based company has diversified its product line to include ground-mount racking systems and BOS components such as disconnecting source-circuit combiners. SunLink’s galvanized steel Large-Scale GMS uses a single-row driven-pile anchoring system. Installers can prepanelize landscape-oriented modules on vertical rails with three or four modules per column. For landfill and brownfield sites, SunLink offers its precast Ballasted GMS system. Earlier this year, SunLink added a cast-in-place ballast option for its GMS racking line. The new ballasted anchoring option uses locally sourced off-the-shelf concrete forms and allows casting of foundations at varying heights to account for uneven site terrain. Both the penetrating and ballasted versions of the GMS line offer integrated grounding and are listed to UL 2703. SunLink recently announced the completed acquisition of ViaSol Energy Solution’s single-axis tracker. Developed for deployment in large-commercial and utility PV plants, the tracked solution rounds out SunLink’s racking system product line.

SunModo

SunModo / 360.844.0048 / sunmodo.com

SunModo is a privately held racking system manufacturer headquartered in Vancouver, Washington. Its products include flashed mounts for composition roofs and EPDM gasketed mounts for metal roofs, as well as racking systems for pitched and low-slope rooftops and ground-mounted arrays. SunModo has based its ground-mount systems on a double-row 2- or 2.5-inch Schedule 40 steel pipe substructure that is braced front to rear. The manufacturer offers a range of galvanized steel caps, sliders, splices and U-bolt kits for various racking system configurations in both landscape and portrait module orientations. Foundation options include earth anchors, concrete encased pipe and ballast. SunModo offers both extruded aluminum and galvanized steel module rail options.

TerraSmart

TerraSmart / 239.362.0211 / terrasmart.com

TerraSmart, a PV racking-system manufacturer and ground-screw distributor, was launched in 2009. Headquartered in Estero, Florida, the privately held company also operates a facility in Chambersburg, Pennsylvania. TerraSmart is the US distribution partner for German ground-screw manufacturer Krinner GmbH. TerraSmart has designed its TerraFarm ground-mount system for installation on its ground-screw anchoring system. North and south leg assemblies bolt directly to the top flange of each ground screw. The system’s galvanized steel structure combines pipe, U-bolt and other attachment fittings with wire rope bracing to form a structure that supports up to 63 60-cell or 56 72-cell modules in landscape orientation, in seven-module columns. TerraSmart’s ground screws and associated drilling equipment are well suited for challenging sites with poor or rocky soils. TerraSmart offers services that range from earth screw foundation installation to full turnkey ground-mount array systems.

Unirac

Unirac / 505.242.6411 / unirac.com

Headquartered in Albuquerque, New Mexico, Unirac was founded in 1998. It designs, manufactures and supports an extensive mounting and racking product portfolio that includes roof- and ground-mount solutions for residential, commercial, industrial and utility applications. (Hilti Group, a privately held global construction equipment provider, acquired Unirac in 2010.) Unirac developed its Large Array (U-LA) system for commercial-scale roof- and ground-mount PV installations. The U-LA system uses installer-supplied Schedule 40 or 80 galvanized steel pipe in conjunction with Unirac’s aluminum attachment components and SolarMount rails. For utility-scale PV plants, Unirac offers its single-row, driven-pile Ground Fixed Tilt (GFT) racking system. The GFT has a galvanized steel substructure (pile, top chord and diagonal braces) featuring a single-bolt top-of-pile connection and a preassembled diagonal brace that unfolds on-site. The top chord assembly and pile have a prepunched hole pattern that provides north-south and vertical adjustability. Four east-west aluminum beams support a two-module column layout in portrait orientation; top-down clamps provide integrated module-to-rail grounding.

U.S. Solar Mounts

U.S. Solar Mounts / 608.272.3999 / ussolarmounts.us

Sparta, Wisconsin–based U.S. Solar Mounts is a privately held racking manufacturer that PV installation company Pipkin Electric launched in 2010. U.S. Solar Mounts can scale its Adjustable Ground Mount (AGM) system for commercial PV arrays. The AGM uses a single-row galvanized steel pipe anchoring system that is typically concrete encased. Preassembled torque cradles installed on each pipe support two 4-inch galvanized steel torque tubes. Aluminum rails support modules in landscape orientation in three-module columns. The racking system allows for easy manual adjustment of the tilt angle from 0° to 50°. Customers can add an optional linear actuator, along with optical or GPS controls, to enable automatic elevation adjustment or solar azimuth tracking.

Zilla

Zilla / 855.670.1212 / zillarac.com

Zilla is a privately held PV racking- and mounting-system designer and manufacturer headquartered in Lafayette, Colorado. Its product line includes solutions for pitched and low-slope rooftops, as well as ground-mounted PV arrays. Zilla’s Ground Mount Systems use a prefabricated aluminum triangular truss that is compatible with the company’s helical piers as well as with contractor-supplied ballasted or concrete-encased anchor systems. The standard truss design layout is two-module columns in portrait orientation with a 30° tilt angle. Various sizes of the ground mount are available, and Zilla designs and manufactures custom trusses to meet specific project requirements. Zilla has designed the trusses for securing to a two-row anchor layout. Aluminum cross rails and bracing tie the trusses together. Zilla’s integrated grounding Top Clip provides module mounting and bonding.

 

CONTACT:

Joe Schwartz / SolarPro magazine / Ashland, OR / solarprofessional.com

 

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[Lafayette, CO] Zilla’s new Cobra flat-roof system includes two lightweight components, the Cobra rail and the ballast pan. The 6061-T6 aluminum rails feature prefabricated attachments and module-mounting hardware, while the galvanized steel ballast pan includes rail attachment hardware. The modular components self-align, so installers do not need to take measurements to determine placement between module rows and columns. The rack supports modules in landscape orientation at a 10° tilt. The Cobra system is compatible with modules up to 45 inches wide and up to 96 inches long, and offers integrated module-to-rail grounding with Burndy WEEB-11.5 bonding washers. The mount is manufactured in the US from recycled aluminum and steel.

Zilla / 855.670.1212 / zillarac.com

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[Union City, CA] The Trellis Roof Mount by ISA is a unique solution for commercial rooftop PV projects where the array must be elevated to avoid roof-mounted equipment or to provide accessibility for roofing maintenance. The system is based on the company’s W Support System, which maximizes the span between attachment points and minimizes the number of roof attachments. The Trellis mount is designed to support 24 modules in portrait orientation and requires one post per six modules. The rack’s tilt angle can be manually adjusted between 0° and 20°. Attachment options include ISA’s innovative SureGrip Beam Clamp, which crews can install and tighten directly to a roof system’s steel beams, minimizing the number of roof penetrations.

ISA / 510.324.3755 / isa-corporation.com

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[Albion, MI] The Spider ST ballasted roof mount by Patriot Solar Group (PSG) includes three main injection-molded HDPE components. The ballast tray, spacer bar and wind deflector feature a snap-together design, and the system requires a single tool for securing modules to the mount. It accommodates 60-cell modules at a 7.5° tilt angle and 70-cell modules at 10° tilt in portrait orientation. It includes integrated wire management, UL 2703 certification, and provision for mounting microinverters and electrical boxes. PSG offers supplementary penetrating anchor options as well. The Spider ST carries a 25-year warranty and is ARRA compliant.

Patriot Solar Group / 517.629.9292 / patriotsolargroup.com

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