Designing and Deploying Carport-Mounted PV Systems

Not all rooftops are well suited to host a PV array. This is part of what makes elevated solar support structures—like PV carports, canopies and shade structures—an attractive option for system integrators and potential customers alike.

Rooftops are space constrained and often present siting, shading and waterproofing challenges. On one hand, if the existing roofing system is more than a few years old, it may need replacing as part of the PV installation. On the other hand, if the roofing system is new, then retrofitting a PV system may void the roof warranty. The structure itself may be inadequate to support additional loads. The alternative, of course, is a ground-mounted PV array. However, many businesses and institutions do not have large areas of unused and unshaded land that they can dedicate to a PV power system for 20 to 30 years.

What these potential customers likely do have are parking lots, parking garages and storage or maintenance facilities for fleet vehicles. These vast fields of asphalt and concrete are ideal for elevated solar support structures. Regardless of location, covered parking is generally preferred to uncovered parking because it provides protection from the sun, rain and snow. Most customers value this convenience, even if they cannot justify paying a premium for it.

Part of what makes the value associated with elevated solar support structures so compelling is that it allows many US customers to receive a benefit like sheltered parking without having to pay full price. At least through 2016, as long as a solar support structure is constructed for the express purpose of generating electricity, it typically qualifies for a 30% federal tax credit. In addition, commercial customers can depreciate parking lot improvements. When they lease or finance carport-mounted PV systems using a PPA, customers often benefit from having covered parking without making any up-front payment.

To better understand the solar carport market, and the associated design and deployment challenges, I reached out to system integrators, carport vendors and industry professionals working where the structural steel meets the road.

Market Overview

If you think that solar carports represent an insignificant niche market, think again. In the summer of 2012, SunDurance Energy commissioned an 8 MW elevated solar structure that provides 32 acres of covered parking at Rutgers’ Livingston Campus in New Brunswick, New Jersey. This is one of the largest university-sited PV systems in the country.

It also bears mentioning that many solar carport projects, such as installations hosted at facilities operated by the US Department of Veterans Affairs or the California Department of Education, are not funded through state incentive programs. As such, these federal, state and municipal projects present another revenue stream for solar companies that are strategically positioned to take advantage of the business opportunity.

Who are typical solar carport customers and what is driving them toward this solution? Are some regions or market sectors hotter than others?

“SPG Solar has designed and installed carports for customers in California, Arizona and New Jersey. Typically, customers select a carport if they do not have a roof suitable for a solar array or an area of their property that they can dedicate to a ground-mounted PV system. Hotels, distribution centers, school campuses, government facilities and water agencies have all installed solar carports to lower operating costs and provide a hedge against rising energy rates. Solar carports are also a visible symbol of an organization’s sustainability efforts.”

—Danny Meyer, project designer, SPG Solar

“Most market activity is in those states where there are rich incentives, and in the West and Southwest where shaded parking is highly valued. Other drivers of demand include rain protection, demonstrating to customers that you have gone green and ARRA [American Recovery and Reinvestment Act] money still trickling through the government.”

—Casey Marshall, co-founder, Crider Americas Solar

“REC Solar’s typical carport customers include schools, hospitals and public agencies with large parking areas and high energy usage. Demand for solar carports in California is increasing as a percentage of the overall project mix.”

—Josh Meyers, senior director of commercial construction, REC Solar

“A key driver is that as the solar industry matures, customers and installers are aware of the challenges associated with rooftop solar: potential leakage due to roof penetrations, restricted roof access for first responders or HVAC service technicians, and the fact that the array may need to be removed and reinstalled to accommodate roof replacement or repair.”

—Steven Crider, co-founder, Crider Americas Solar

“California schools have been very actively incorporating solar support structures as compared to other regions. Educational facilities in California prefer this solar solution largely in response to stringent permitting requirements put in place by the Division of the State Architect [DSA]. In California, we have seen that 80% to 90% of school RFPs [request for proposals] have some preference for the use of elevated solar support structures in parking lots as opposed to roof mounts.”

—Ed Condreay, director of business development, Borrego Solar

“The demand for solar carports is growing in the Southeast, Southwest and Northeast, areas where roof and ground mounts have traditionally been market-leading solutions. The rise in demand is due in part to a gradual reduction in the cost of PV system components. These cost reductions—combined with technological advancements allowing for faster, more cost-effective installations—have eased barriers so that adding solar to an existing parking lot can make financial sense. In addition to providing an attractive return on investment in these markets, solar carports provide additional benefits such as increasing property values, generating clean energy, and protecting people and vehicles from the elements.”

—Tom Racioppo, product manager, Schletter

“We have taken the approach that solar will find the highest-value opportunity where it brings together multiple needs. In Texas, my primary market, the sun evokes energy and shade. These two ideas come together elegantly in the form of a solar carport, which I generally think of as a solarscape. From this perspective, installations that fall within this project class include carports as well as stand-alone shade structures, building-integrated awnings, porch covers and multipurpose elevated ground mounts.

“Our customers range from commercial business owners to ranchers, from real estate developers to homeowners and visionaries. The primary motivation behind a customer’s interest in solarscapes is to maximize and expand the value proposition of solar. Shade is an added value. Integration into existing architecture or historic preservation is an added value. Avoiding roof issues is an added value. Site amenities are an added value.

“As prices fall, a more diverse group of customers can be included within the solar market, as solar provides viable solutions for a wider range of architectural programs. While we consistently try to think ‘off the roof,’ solarscapes still make up a limited percentage of our business—between 5% and 8% of our projects.”

—Stan Pipkin, vice president and managing director, Lighthouse Solar Austin

Design and Deployment

Solar carports present unique challenges with regard to system design, permitting, project management and construction. Consider, for example, the scope of work that your company performs on a typical roof-mounted PV system. Now imagine that you are installing the same array on a purpose-built carport. Whatever subcontractors you were using previously, you likely now need to add a surveyor, a geotechnical engineer, a structural engineer, a drilling excavator, a concrete supplier, a steel erector and perhaps a horizontal directional boring contractor.

What this means is that your company’s abilities as a specialty contractor are less important to the successful and timely completion of a solar carport project than are its abilities as a general contractor. You also need to plan for the unexpected, as you are unlikely to know what lies underground until you already have the job. The good news is that once you get out of the ground, a solar carport is essentially an oversized Erector set—well within the capabilities of an experienced steel erector and a specialty solar contractor.

What post-sale challenges might one encounter when siting or permitting a solar carport? How can companies minimize, mitigate or avoid these?

“Carport layout is an integral part of the design process. A great deal of communication is required with project developers, real estate owners and AHJs to ensure that the layout is code compliant, maintains the right of way and aligns with required offsets. Sometimes the responsibility for laying out carports is a hot potato. This scope of work should always be addressed up front and defined in the contract.”

—Steven Crider, Crider Americas Solar

“The sale of a solar support structure is negotiated and signed by two parties who often want to maximize the amount of PV that can be placed on a given site. Typically, this process is undertaken with limited resources to determine the existence of underground utilities, the location of property boundaries, any required building setbacks and any limitations that the building department, fire department, electrical utility and other authorities may place on the project. Sometimes after undertaking thorough site discovery and design work, the layout of the system as sold turns out to be at odds with existing site conditions.

“While the ideal situation would be to complete all site discovery and preliminary design work prior to signing a contract, this is likely not realistic due to the financial investment required to obtain the information and perform the engineering. Ultimately, the contract must allow for revisions to the system size and configuration as additional information is gathered and the system engineering is finalized to account for all the existing conditions and any imposed limitations.”

—David Dutil, PE, structural engineer, Borrego Solar

“The more information a system integrator can provide the supplier, the better. More often than not, post-sale challenges come from lack of information in the design phase. Permitting is always a wild card as every jurisdiction has its own processes. Those challenges, unfortunately, have to be faced on a case-by-case basis. That said, you can avoid most of them if your permit package is complete and concise.”

—Matthew Harrison, director of operations, Baja Construction

“Getting a solar project approved through the DSA can be time consuming. This is often the biggest challenge we face, as our customers usually want their systems built quickly. There are also a number of key design elements that are often overlooked initially, which then leads to costly redesigns later. The primary examples in this category are ADA [Americans with Disabilities Act] access and fire department access. If you do not address these two factors early in the permitting process, they can delay a permit by several months and cause repeated revisions to your design and layout.

“ADA access has several design implications. For example, we are required to cover the same percentage of ADA parking stalls as non-ADA stalls. Another factor is that the ADA stall or solar shade structure must have an accessible means of egress. Often the change in grade of existing sidewalks does not meet current ADA guidelines, in which case the DSA requires that you provide ADA-compliant access. This is often difficult to price during the bid process, unless a topographic survey of the entire site is provided in the RFP.”

—Ed Condreay, Borrego Solar

“Prior to contracting for a particular system capacity and energy output guarantee, carefully analyze the parking lot being covered—and consult the local jurisdiction—to identify any hidden costs, sources of shading or site constraints. Parking accessibility requirements are one potential source of hidden costs. Existing trees or parking lot lights may need to be removed. In some jurisdictions, tree removal can be difficult, costly or forbidden. This either reduces the space available for solar carports or significantly reduces the energy production due to shading losses.

“Often a carport array is wider than the parking spaces it covers, overhanging the drive aisle. This overhang is not allowed to extend into fire lanes. Where it is allowed, there is a risk that large vehicles, like RVs and garbage trucks, will drive into and damage the array. Building high-clearance carports significantly increases costs.”

—Danny Meyer, SPG Solar

“Project financing is critical, as solar carports are labor- and capital-intensive constructions. Contracts must be written in such a way as to keep things moving.”

—Casey Marshall, Crider Americas Solar 

“The general disconnect between the decision makers interested in the renewable energy proposition and the facility or site management team is consistently challenging. This is true of institutions, businesses and homes. Solar carports are facility-level capital improvement projects. These projects may tie up land, traffic or internal resources. During the negotiations, these issues are rarely covered in full. If customers make an initial investment in design, planning and coordination, they can avoid a lot of these issues and arrive at a better solution.”

—Stan Pipkin, Lighthouse Solar Austin

Do you have any recommended best practices for the structural design of a solar carport system?

“The solar support structure is just that, a structure that supports PV modules. It is a necessary component of the system, but it is not the portion of the system that is making, or saving, the customer money. Therefore, the structure’s design must be economical enough to make the project financeable, yet robust enough to safely support the PV modules and all required loads. To help accomplish this, we commission a geotechnical report for the specific project.

“When time allows, we design a foundation to the site-specific soil conditions and code-required loads, as this invariably results in the most economical solution. However, our schedule generally does not afford us this step when we are working on solar support structures at public schools in California. A full review by the DSA can add approximately 3 months to the permitting timeline. As a result, we typically sacrifice some efficiency in the structural design by using a structural system that the DSA has prechecked. A prechecked system is usually overdesigned to accommodate a range of dimensions, configurations and loads.

“While a prechecked design saves time in permitting the project, it comes with limitations associated with size, height, column spacing and so forth. Part of the design challenge is to ‘fit’ the prechecked design into the system layout on a specific site. [See the Borrego Solar case study sidebar] This is complicated further by the need to ensure that all the design constraints of the structural system are not exceeded. This is especially difficult when dealing with parking lots with sloping grades and/or relatively dramatic topography, since the contract often requires a minimum clearance height on the low side of the carport.

“To ensure that our low-side clearances are met without exceeding any of the structural design constraints, we import a topographic survey of the parking lot into AutoCAD 3D and model each solar support structure. We use this model to set foundation locations and elevations as well as the column heights for fabrication. During this process, the structural engineering team works closely with engineers in other disciplines to make sure that we are balancing the structural requirements with such things as module stringing, ADA path-of-travel constraints, underground utilities and other project-specific requirements.”

—David Dutil, PE, Borrego Solar

“We commission site-specific geotechnical reports to ensure cost-optimized footing designs as compared to code minimums. We employ subcontracted structural engineers with significant experience in carport design and erection to design the structural steel, and we look for partners with solar-specific carport experience.”

—John Hostetter, director of engineering, REC Solar

“Ensure that your engineer is licensed in the state in which your project is installed and that the engineer’s professional liability insurance has never lapsed. As an aside, it would be very helpful to the industry as a whole if there were an industry standard for maximum deflection allowed on canopies. Without this standard, design engineers must make their own determination about what is suitable, which typically results in a more conservative design than necessary.”

—Steven Crider, Crider Americas Solar

“SPG Solar always engages a geotechnical engineer to do soil sampling and analysis, while the design of the foundation is almost exclusively within the design and build scope of the solar carport subcontractors. The geotechnical report ensures that we have an accurate understanding of the existing site conditions. From this information, we design the foundations to fit the site parameters.

“Work with the structural engineer early in the design process, so that the finished structure is suitable for mounting the modules. Make sure the purlins are spaced correctly for the modules. Also pay special attention to the connection details; oftentimes there will be plates, brackets or even bolts that interfere with the plane of the array, disrupting the tilt and/or spacing of certain modules.

“Deflection is an important structural consideration that is often overlooked. The most common carport structure is a full cantilever tee type, which is a double-bay, single-post structure with cantilevered beams up to 20 feet long. While the structure may be plenty strong, excessive deflection gives it a droopy look and can affect production if the array is not strung properly. Work with the structural engineer to limit deflection of all structural members to L/180 or less. With a minimal cost increase, this gives the array an aesthetically clean look and decreases mismatch.”

—Danny Meyer, SPG Solar

“Always establish your foundation design assumptions when responding to an RFP. Most RFPs do not provide geotechnical reports. Those that do often do not cover the area where the solar is being installed. The tilt of the array is another consideration, since it factors into energy production. We have found that the best balance between support-structure cost and solar production is achieved using tilt angles in the 5° to 10° range. While clients sometimes request a painted finish for the solar support structure, we prefer to use an unpainted galvanized finish that eliminates the maintenance costs associated with repainting. On one hand, a good coat of paint might last 5 years before the structure needs to be repainted; on the other, a good galvanized finish costs less, requires no maintenance and lasts more than 50 years under most conditions.

“In years past, solar support structures were primarily erected using light-gauge structural steel with a column spacing of 18 feet—spanning two parking stalls—and no exposed concrete above grade. Design improvements and DSA guidelines have since led to solar support structures erected using heavier-gauge structural steel columns spaced every 27 feet—spanning three parking stalls—and structural steel beams with light-gauge purlins that support the solar modules. These structures typically have a galvanized finish and the foundation includes 24 to 36 inches of exposed concrete above grade to protect the columns from vehicle damage.

“One design factor that is often overlooked is that the modules are secured to the purlins mainly via a pressure connection, using mid or end clamps. While this connection is sufficient if the purlins do not twist or sag, the reality is that most purlins in fact twist or deflect during installation or through temperature changes. To prevent modules from losing their connection to the mounting surface, designers may need to bolt modules to the purlin or otherwise change the module-mounting method. Always make sure that you address the manufacturer-specified module-mounting requirements.”

—Ed Condreay, Borrego Solar

“Thoroughly involve the engineers in the design of the structure and the site evaluation, including the geotechnical report. I also recommend engaging the engineer in the rationale for the PV design so that the appropriate design considerations are acknowledged and respected. For example, at a smaller scale, we may consider access to the site more important than the absolutely optimal frame design in terms of the number of columns.”

—Stan Pipkin, Lighthouse Solar Austin

Does your company have any design standards or best practices for the electrical design of a solar carport system?

“Many of the electrical design best practices for roof- and ground-mounted PV are equally applicable to carport projects. For example, the engineering analysis for combiner sizes and locations relative to the inverter, trench or conduit routes, conductor material, and other basic electrical layout and Code-compliance considerations are all very similar, regardless of racking type. However, there are some unique considerations because solar carports are above or adjacent to areas where the general public congregates. These structures are often noncontiguous and typically located a good distance away from the point of interconnection.

“Proximity to the general public has two ramifications. First, safety is paramount; second, people observe the product’s aesthetics and workmanship every day. From an electrical standpoint, safety considerations include proper equipment grounding and bonding, appropriate placards and signs, reliable and well-thought-out wire management, and an appropriate area-lighting system design. While aesthetic concerns are not as important as protecting the public from hazards, people tend to see the underside of the canopy much more frequently than the front side of the modules. Haphazard wiring or conduit runs can negatively impact how the public and the client perceive a project. We pay a lot of attention to wire management, conduit routing and equipment-grounding details, emphasizing quality work and minimizing its visual impact.

“The physical location and size of carport arrays probably has the biggest impact on the electrical design. Since the layout is highly dependent on the geometry of each parking area and the stall striping, the system design is highly site specific. In certain scenarios, there may be a strong argument for a distributed inverter design, such as multiple small carports, each with module quantities that match available inverter capacities. In other cases, such as when a fewer number of larger structures are evenly distributed around the point of connection, a centralized inverter design may make sense. The on-site utilization voltage may also impact the electrical design. If you are interconnecting to a 208 Vac service, then it may make sense to distribute string inverters across the site, since many central inverters operate at 480 Vac.”

—Benjamin Walter, PE, electrical engineer, Borrego Solar

“Site-specific conditions or customer requirements dictate the scale of inverter selected, as there is no one solution in all situations. The optimal conductor routing and circuit aggregation depends upon many factors, including the specific geometry of the site, voltage drop, wire cost as compared to collection and distribution equipment cost, trenching costs, labor costs, site requirements for equipment and who will have access to the equipment.”

—John Hostetter, REC Solar

“Our preferred system design still uses the large central inverter model, usually with one standard combiner box—without an integrated disconnect—per carport. Parking areas are generally open to the public, and we prefer to locate inverters and PV disconnects away from publicly accessible areas. This mitigates the risk of somebody turning off the system or a portion of the system.

“It is also important for each individual carport to have complete strings; no source circuits should include modules on multiple carports. This does create design limitations, so using string inverters can provide more flexibility when carport arrays must have odd numbers of modules. Since bonding carport arrays to ground can be very time consuming and costly, choosing attachment hardware that bonds the module frames to the support structure can greatly simplify the array-grounding plan.”

—Danny Meyer, SPG Solar

“We prefer distributed solutions that ideally follow a structural bay logic. This allows us to locate transition or aggregation points at structural columns. We use the structural shapes where possible for conduit or wire routing.”

—Stan Pipkin, Lighthouse Solar Austin

In terms of the actual installation, do solar carport projects present any unique logistical or project management challenges? If so, how can these be minimized or mitigated?

“Most carport projects should include an experienced project manager, someone who basically lives on-site during construction. This person should be well versed in foundations and steel erection. Solar integrators typically have a core competency on rooftops and are less knowledgeable about underground drilling, concrete work, rebar and underground utilities.”

—Steven Crider, Crider Americas Solar

“Carports are often built within parking areas that are already fully utilized. To minimize the impact on parking space availability, the construction must often be phased in small sections. It is essential at the outset of any contract negotiation that the owner understands that available parking will be impacted through the construction period.”

—Danny Meyer, SPG Solar

“We almost always encounter client issues associated with the temporary loss of parking stalls. This should always be addressed in RFP responses and construction meetings. Keep the client informed about the work schedule and its impact on traffic flow and parking.”

—Ed Condreay, Borrego Solar

“Every carport project is unique in the sense that each one is designed specifically for the site where it is deployed. Good communication and proper prior planning mitigate logistical challenges such as site safety, traffic egress and loss of parking. System integrators should hold preconstruction meetings with their contractors and the facility managers. This helps to develop a solid construction schedule and to identify and mitigate challenges.”

—Matthew Harrison, Baja Construction

“Project management challenges include establishing working and staging areas, determining the maximum number of lost parking spaces, creating a construction phasing plan, implementing a site safety plan, developing a traffic management plan, identifying ac circuit-routing paths and agreeing on a post-construction restoration plan. While planning is important, make sure that you have the flexibility to adapt and change the details as construction progresses.”

—Josh Meyers, REC Solar

“Solar carports are essentially small-scale architectural design and civil engineering projects. Project managers likely need to coordinate more subcontractors and construction trades than are typically involved in rooftop installations. In addition, the impact on the general public is greater, which has a higher cost to the organization hosting the carport. This has the potential to lead to unreasonably short time windows for on-site construction, which can jeopardize the continuity and quality of the work. Regrettably, the robust, multilevel project management team required to avoid these types of problems is not always part of the DNA of a solar installation company.”

—Stan Pipkin, Lighthouse Solar Austin

“Carports are generally tall structures, especially in commercial applications that call for truck and large vehicle clearance. Working at these heights can be more challenging and time consuming than roof-mounted projects. Much of the work is performed on mobile lifts or scaffolds, which can increase the labor time required.”

—Tom Racioppo, Schletter 

Does your company have any best practices or success strategies for streamlining the installation of solar carport systems?

“The single greatest factor in streamlining the installation process is to secure as much available parking area as possible.”

—Josh Meyers, REC Solar

“Before any drilling takes place, call the local utility locator service to identify underground utilities like water, gas, electricity or telecommunications lines. Concrete X-rays are a good idea if the project economics can support it. Geotechnical studies tell you what is underground at the boring sites only.”

—Steven Crider, Crider Americas Solar

“Many of our solar support structure projects are at public schools where we schedule construction during the summer when school is not in session. To avoid delays during construction, we emphasize three things: site discovery, engineering and construction control. Good site discovery yields comprehensive site information, which limits the chances of uncovering an unknown condition during construction. During the engineering process, we use information gathered during site discovery to simplify the design while meeting all the project constraints, with the goal of reducing the amount of coordination required during construction and minimizing opportunities for mistakes. Good construction control ensures that we can catch mistakes early and address them immediately. Borrego Solar followed this model to complete five solar support structure projects for three school districts in California during the summer of 2013. Using a single steel fabricator and erector, we constructed a total of 38 individual structures with 223 foundations and a cumulative generating capacity of 2.24 MW—and completed all of the projects on schedule.”

—David Dutil, PE, Borrego Solar

“While larger carports with longer cantilevers are rising in popularity because they allow for spans over multiple parking spaces, these features have to be weighed against the associated costs of heavier materials to maintain the structural integrity and larger footings. Sometimes bracing may be required during construction to ensure a safe installation environment. An experienced carport vendor can help a system integrator consider these variables and develop the most cost-effective solution.”

—Tom Racioppo, Schletter 

“During the design phase, work closely with the carport vendor to ensure that its design works with your attachment strategy and the electrical aspects of the PV arrays. To secure a clean installation, also coordinate with your subcontractor during construction. For example, install stub-ups prior to pouring concrete foundations, so that conduit runs from combiner boxes do not look like an afterthought. If necessary, install inverters before the steel canopy blocks the overhead access required to crane them into place. Once the steel is up, a small, well-organized crew can use a scissor lift to quickly install the modules.”

—Danny Meyer, SPG Solar

Qualifying Vendors and Solutions

If you do not already have a preferred carport vendor, consult Table 1 for a representative listing. Many of these companies offer a variety of standard and custom carport configurations. The scope of services also varies, with many vendors providing turnkey solutions.

What should system integrators look for when qualifying a carport vendor and specifying a carport solution?

“We look for established vendors who have design-build capabilities—either in-house or outsourced—and who have been involved in previous projects with the permitting authority. Vendors must have enough experience to be able to cost-optimize their solutions. Also, they must understand the cost and scheduling risks that are inherent when constructing large systems in existing, and often active, parking areas.”

—Josh Meyers, REC Solar

“System integrators should look for proven technology. Always qualify a company’s product based on system compatibility and durability. Also look at the company’s experience in the industry. How many projects has it completed successfully? What size are these projects? Finally, analyze the economic feasibility of the product based on overall cost, ease of installation and added value.”

—Matthew Harrison, Baja Construction

“We have worked with Crider Americas in Texas, both through design and implementation. We also design, engineer and fabricate site-specific solutions in-house. We evaluate a carport or structure provider based on the merits of its solution rather than on a set of components. We prefer to work directly with a vendor’s development team. If that is not possible, or if the project warrants more direct involvement, we manage the design and implementation in-house.”

—Stan Pipkin, Lighthouse Solar Austin

“The vendor should be able to provide project references and a range of aesthetic options, as well as stamped engineering drawings in any state. Ask whether they offer a turnkey solution that includes foundation, erection, racking and panelization. Does the price include a site-specific or a generic foundation? What equipment is required to complete the installation? Is field welding required? Who is fabricating the material and where is it coming from? What is the finish material? What are the material lead times?”

—Stephen Crider, Crider Americas Solar

“When we consider various carport vendors, we want to know how much permitting experience they have with the AHJ. We want to know if they can provide a structural engineering stamp. We look into their performance on past projects. Have they demonstrated an ability to maintain a project schedule? If the foundation is included in their scope of work, have they demonstrated that they can overcome unforeseen underground obstructions?”

—Ed Condreay, Borrego Solar

“System integrators should consider the materials used for the structure, the finish and maintenance of the system, installation requirements, type of foundation and how much destruction or repair is required for the existing asphalt blacktop. They should also take into account whether things like engineering support are included in the price, as these variables can introduce unexpected project costs.”

—Tom Racioppo, Schletter

“We have worked with several design-build contractors, including Baja Construction, M Bar C Construction, Schletter and Skyline Steel. These companies all have experience erecting steel structures. They also have a variety of designs in their portfolios, ranging from economical solutions to higher-cost structures with more architectural features. Competitive pricing and timeliness of engineering and construction services are our chief considerations when selecting a subcontractor.

“The scope of the subcontractor’s work typically ends at the purlins, which support the array. It is up to the solar contractor to attach the modules. Our most recent projects have used Schletter clamps to secure the modules to the structure, because these helped reduce the cost of bonding the array. Also, the stainless steel hardware can be installed in a way that allows the modules to be removed from underneath the array. This is a valuable feature in terms of customer service, since there is no safe way to access a typical top-down module clamp once the array is completed. If you do not consider this eventuality during the design, it is more challenging to replace a module in the future.”

—Danny Meyer, SPG Solar

CONTACT

David Brearley / SolarPro magazine / Ashland, OR / solarprofessional.com

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