Designing the optimal solar PV system is no easy task. There are a vast number of variables to take into account—from deciding which components to use to determining the best stringing configuration. But there are a few commonly overlooked considerations that can be particularly devastating.
We spoke with experienced solar designers to understand some of the most problematic solar design pitfalls. Failing to account for these factors in the design phase can have a dramatic impact on the quality of the installation and damage your credibility with clients (not to mention your bottom line).
1. Miscalculating the impact of shade
One of the most common—and most serious—mistakes in solar design is the failure to accurately account for how shading on the project site will impact solar energy production.
Commonly overlooked elements that shade solar arrays include nearby trees, roof vents, chimneys and in some cases surrounding buildings, according to Joe Montoya, co-owner and residential sales director of Namaste Solar, an employee-owned cooperative that designs, installs and maintains commercial and residential solar systems throughout the United States. He added that such oversights are “clearly problematic as they will have an impact not only on the customer’s expectations, but also the ROI of the project.”
The need for accurate shading analysis is a key reason why a precise 3D model of the project site is an important and powerful tool for designing quality solar installations. A detailed site model makes it possible to assess how elements like trees will cast shade at different times of the day and year. Paired with a remote solar design software platform that models the movement of the sun (as well as the impact of local weather patterns), you won’t need to guess at the impacts of shade.
Doug Munsch, project developer at Straight Up Solar—a solar installation firm that has installed more than 950 residential- and commercial-scale solar projects in Illinois and Missouri since its founding in 2006—observed that “too often interested parties consider the decision to move forward with solar without a realistic expectation about what impact obstructions, like chimneys and trees, will have on the performance of an array. Nothing hurts the experience of going solar more than giving someone shadows when you promised sun.”
This is particularly true because a small amount of shade can have a disproportionate impact on solar energy production. Software like Aurora can be a key tool in ensuring accurate estimates of solar energy production in light of shading at the project site. According to Munsch, “Aurora’s 3D modeling and LIDAR help shape expectations about an array’s performance between client and contractor before anyone even sets foot on top of a roof.”
Of course, you’ll also want to ensure that the system you use to model the energy production of your design precisely accounts for electrical behavior within the shaded PV system, including the stringing configuration and the capabilities of component parts. A simulation engine that can model electrical behavior at the cell-string level will offer even greater accuracy.
2. Misjudging physical characteristics of the project site
In addition to being important for shading analysis, as discussed above, accurate assessment of building proportions and other characteristics is essential to ensuring that your design fits the site and that the installation process is smooth and error-free. Misjudging physical aspects of the project site is another common mistake that solar designers highlighted.
Zach Hall, VP of business development at TriSMART Solar, a full-service solar provider operating in Texas, Arizona and Utah, notes that getting the site model correct is the “first step [to designing a solar installation]—if it is incorrect, so will be everything else.” This includes making sure the height of the building, lengths of different roof edges and structure of different roof planes are all true to life.
For rooftop solar arrays, one common error is misjudging the pitch of the roof. Aurora Solar customer success representative Victor Ionin , who teaches Aurora’s continuing education course in Advanced 3D Modeling, explained that this is problematic because the tilt “greatly affects the surface area available for solar. For instance, a roof with a 45° tilt has a larger surface area than the same roof with a 15° tilt.” Thus, overestimating the roof tilt could result in a system that is too large for the customer’s available roof space.
Montoya added that aside from space considerations, misjudging the pitch will “have operational efficiency impacts as well.” This is because the tilt and orientation of the roof have a significant impact on the amount of solar energy that will be available on the surface of the array.
Remote solar design tools with LIDAR can ensure that tilt and other building characteristics are correctly modeled, even without a site visit. Where LIDAR is unavailable, another technology that can facilitate assessment of roof tilt is computer vision. Aurora uses computer vision to take precise measurements from Google’s Street View combined with top-down aerial or satellite imagery. Aurora’s process has been validated by the National Renewable Energy Laboratory to accurately measure roof pitch to within two degrees and lengths to within six inches. Additionally, having a design program that makes it easy to create a precise model of the project site can help eliminate the accidental introduction of errors.
3. Overlooking local building codes or permitting requirements
Munsch said one of the biggest solar design mistakes is overlooking code requirements of the local Area Having Jurisdiction (AHJ), such as International Building Code (IBC) and National Electrical Code (NEC) requirements.
“In the bidding process, deals can be won or lost based upon solar contractors’ familiarity with what designs are permitted. Nothing says a competitor didn’t do their homework like a design which encroaches on fire code setbacks or fails to include a mandatory rapid system shut down,” Munsch said.
Solar design software that validates your designs to confirm that they do not violate NEC requirements or local fire code setbacks can be a valuable tool in safeguarding against oversights that could derail approval of your design.
While there are many factors that need to be considered to find the optimal solar design for your customer, being mindful of these three potential pitfalls will help you avoid some of the common causes of underperforming installations and costly change orders. State-of-the-art remote solar design tools offer a variety of features that, when used correctly, eliminate these kinds of oversights and help you deliver quality solar PV systems that satisfy customers.