Taking a Digital Approach: How to Standardize Workflows and Design Systems with Unprecedented Accuracy

Technological advancements in the solar industry, such as standardized, digital approaches to shade analysis, are making the installation of photovoltaic systems more efficient than ever. However, to incorporate digital approaches to shade analysis, installers need to be confident in their production estimates. Increased project timelines can create uncertainty around actual production, unsatisfied customers, and decreased profitability. The objective of this study was to shorten design/installation timelines by finding a solution that reduces time spent conducting site visits without compromising shade analysis accuracy. To accomplish this goal, solar access values (SAVs) derived from aerial imagery and computer vision were tested by a third-party quality assurance company against SAVs gathered by a handheld measurement tool on site. To derive values with aerial imagery and computer vision, multi-angle aerial imagery is taken to create a 3D model of the property along with thousands of consistent roof measurement points. The path of the sun is traced over the 3D model. For each 15-minute interval of the year, the solar access is recorded at each measurement point for unprecedented accuracy. The quality assurance company chose an industry standard hand-held device as a benchmark, which derives measurements of a property on-site. Four properties in the Bay Area were chosen as test sites based on diversity of shade. An independent technician collected measurements of the properties using the hand-held tool under instruction from the quality assurance company. SAVs were then derived from already collected aerial imagery to compare against the hand-held measurements. The study found that in a point-to-point comparison between the hand-held measurement tool and the measurements derived from aerial imagery, the average difference was between –1% and 0%. Approximately 70% of the individual locations studied resulted in an annual difference between the two measurements of <5%. Additionally, the study noted that the aerial imagery measurements “can provide modeled SAVs at more locations on a roof than could be practically measured and processed manually.” The quality assurance company named the aerial imagery measurements as “comparable” to the leading shade-estimating tools accepted by solar professionals. The objective data extraction process can also reduce the risk of on-site measurements varying amongst technicians. The study found that the SAVs derived from aerial imagery are “a viable tool for estimating shade impact on the roof of common residential/low-rise structures.” The study concluded that SAVs derived from aerial imagery are “a compelling alternative to on-site hand-held measurements” as they “can provide a more repeatable measure” without having an inspector climb on the roof, saving time and reducing site visits. The method derived from aerial imagery provided a more detailed data set, with over 1,000 times more data points than the traditional handheld sampling method, for more accurate designs and increased efficiency.