Q & A: Aerial Site Surveys Save Time and Resources

I operate a residential solar company. I am consuming a large amount of employee resources performing preliminary on-site analyses for customers who either do not have proper solar access or do not move forward with the project. How can I use fewer resources and still provide the quality service my customers expect?

Allow me to preface my answer by describing my experience as a preliminary site inspector for Austin Energy. This municipally owned utility has a very aggressive, yet cautious, solar rebate program. To prequalify a site for participation in our solar rebate program, we must perform a preliminary shade study. A subsequent site survey occurs at post inspection to ensure high standards in the installation.

When I started this position in 2006, the typical procedure was to conduct an on-site analysis for each Austin Energy customer expressing interest in the solar rebate program. A backlog of 60 customers kept some waiting 2 to 3 months for a preliminary inspection. The process required setting up a file, entering data into the job log, scheduling the site visit, producing an information packet and driving to the site for an evaluation. Each site inspection involved 30 to 60 minutes of face time with the customer. Austin has a lot of tree shading, and despite our best efforts to inform the public of solar access requirements, many of the site analysis requests came from customers with no solar window. Their homes were completely shaded. There were also many customers who were seeking information but had little intention of moving forward with an installation. My entire workload was spent accommodating feasible and unfeasible customers, and I was still unable to keep up with the demand. I quickly realized that we were wasting resources on sites that had no potential.

In order to become efficient and maintain good customer relations, we needed to develop new procedures. The first step towards efficiency came by using aerial photographs in a Geographic Information System (GIS) to help generate the site survey. The GIS format allowed us to create a template for site surveys that included the aerial image of the home and pertinent information extracted from the job log. The City of Austin provides digital aerial photographs produced during the winter of 2006. These 6-inch-scale, high resolution aerial photos offer accurate and measurable depictions of the roof planes, thus eliminating the need to physically measure and draw them. These photos are also aligned to true North, so it is possible to calculate an accurate azimuth for each roof plane without worrying about declination or magnetic interference. I took a hard copy of the aerial image into the field to align the photo with the roof in order to position the shade analysis tool to correspond with the North arrow on the aerial. This allowed me to determine true North at the site. The aerial map was also useful for quickly denoting any shade obstructions by marking their positions. Upon returning to the office, I digitally entered the aerial markups into the GIS tool to store them electronically for future access. The GIS tool along with the aerial photographs also allowed for calculation of square footages to approximate the amount of solar that a site could accommodate.

This preliminary GIS-enhanced process considerably reduced the time it took to perform an on-site survey, and the customers loved the use of the technology as well. However, I still wasted a significant amount of time on visits to homes that were not feasible for solar due to tree shading. Bird’s-eye view images available online helped reduce that unnecessary time expenditure. These images show the home at four different angles and are taken from an airplane. The image set for Austin was taken in the winter and gives some indication of the approximate distance that a shadow is thrown. By carefully studying these images and getting the metadata to determine when the individual photos were taken, I developed a process that allowed me to determine a site’s eligibility approximately 75% of the time, without the need to travel to the site.

With previous experience using an on-site shade calculation tool and a good understanding of the annual shade patterns produced by objects on different orientations and tilt angles of a roof plane, solar professionals can use aerial images to perform preliminary site assessments. It is possible to use the angled aerial images to estimate the height of the roof plane and the distances of objects to determine the shading that will be produced. Once you have identified the approximate shaded areas, you can use the GIS tool to calculate the solar window. It is important to realize that this method is not as accurate as an on-site visit, but it allows you to perform the evaluation in a fraction of the time using far fewer resources.

Using these methods, the response time to a customer request is approximately 2 weeks. Austin Energy saves time, gas, paper, risk of on-site injury and wear on vehicles. Since these new procedures were adopted, customer satisfaction and customer participation in the program have risen. Although these procedures may not translate directly to a contractor’s business model, I think that it is helpful to know how successful Austin Energy has been in streamlining its procedures. I believe that these processes can be modified to greatly reduce time spent on preliminary site assessment, to allow some email and phone consultation to take place before a house call and to reduce overhead required for a project.

Tim Harvey / Austin Energy / Austin, TX / austinenergy.com

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