“It doesn’t have to go on your roof,” I explained to homeowner Eric Lindgren of Bonney Lake, Washington, while Alex from Brothers Electric Solar was on the roof measuring for a new PV array. To take advantage of Washington’s production incentive program, Lindgren was considering installing a 9-kilowatt solar-electric system, which would generate enough energy to recoup costs before the program expires in 2020. But the roof had its challenges: it was partially shaded and the shingles needed to be replaced. At a 5:12 pitch, it wasn’t at an optimal angle for a flush-mounted PV array. Plus, there wasn’t enough space on the roof to fit a PV system that would max out the yearly incentive payment. Lindgren’s south-facing yard was huge, though—perfect for a ground-mounted array.
We measured the area for a 9.12 kW array. To capture the highest incentive rate, we needed to use Washington-made equipment, which meant using 38 Itek Energy 240 W modules and Altenergy Power System (APS) microinverters. The same modules installed on a dual-axis tracking mount, however, only needed to be 7.2 kW, since production increases by up to 28% with a tracked array at this location. We estimated that two rows of 15 modules each on Sedona Solar dual-axis frames could produce the kilowatt-hours needed to pay off the system within seven years.
Compared to the fixed system, installing a dual-axis tracking framework and controllers was less expensive, since there were eight fewer modules and inverters to purchase. An added bonus in Lindgren’s case is that the two arrays fit perfectly around his garden.
The framework that holds the modules and tracking frames is mounted on eight 4-inch-diameter galvanized steel posts set in concrete. Two actuating arms control the array’s elevation and another controls its azimuth. They are energized by the controller and position the array by calculating the sun’s position based on the site’s longitude, latitude, and local time.
Each module is wired to a microinverter. The inverters and wiring had to be carefully placed on the framework to avoid any contact with the rotating modules and rack. Module-level online monitoring is through the APS software, and a smartphone app (designed by Lauritzen Inc.) is available for remote operation of the system. Having remote control of the array allows the system owner or installer to reposition the modules for cleaning, maintenance, storm readiness, or even snow clearing—without having to open up the control box on each subarray. The smartphone app allows access to the controller’s many parameters with a joystick-like interface.