Tracking Success

With a wide-open summertime solar window, this small dual-tracked array produces enough electricity for the seasonal residence.

A pair of 2,720 W pole-mounted, tracked arrays at the Tucson site have generated even more energy than originally predicted.

Home builder Ed Marue offers his perspective on making the most of his PV energy production with tracked systems operating in two very different climates.

The conditions for the remote, off-grid installation were ideal—a seasonal residence on a wide-open property that takes advantage of the long summer days in central Idaho, when the sun makes a sweep from 15° north of east to 20° north of west, with more than 11 peak sun-hours daily. Under these conditions, the 960-watt PV array easily keeps the 1,000 amp-hour battery bank charged, powering a 1,000-square-foot cabin equipped with lighting, a washer, a TV, a computer, a vacuum, and a dishwasher. Because of the ample energy the batteries receive from the array, rarely does the battery state of charge drop below 70%.

The system—eight Kyocera KC120 modules and an AZ-125 Wattsun dual-axis tracker—was easy to install and has worked perfectly. A pyramidal sensor mounted on the array signals the electronic controller, which powers the DC azimuth drive motor and elevation actuator, always keeping the array perpendicular to the sun. The tracker has weathered six summers and winters, and temperatures of 112°F to -10°F, with no repairs or maintenance, other than greasing the gear head each spring. In the winter, the array is left unattended, and power to the controller is shut off with the tracker pointed due south at a steep angle to shed snow more easily. Because there is no requirement for power during the winter months, the decision to install a tracker, rather than a more costly, larger, fixed PV array, has proven to be a wise choice.

The  grid-tied installation in Tucson, Arizona, also had a wide-open site, but there were no good roof-mount options—the design of the home minimized southern exposure to decrease cooling loads. So two Wattsun AZ‑225 trackers, each with 16 BP SX170 modules, producing a total of 5,440 watts of PV, were chosen. The trackers installed easily, and other than an initial problem with an elevation drive motor that had intermittent brush contact, there have been no reliability issues in the 18 months since commissioning. The manufacturer’s documentation was clear and concise, and the company was extremely responsive in resolving the initial problem, which required a replacement motor. The  array has produced 13,174 kWh in its first year of operation, slightly more than predicted.

The system was installed during the home’s construction, and on-site labor for the array installation was not separately accounted for. Excluding labor, the gross cost of the system was $42,247, with a net cost of $25,927 after a $16,320 utility rebate. An equivalent 7.65 kW fixed array was estimated to have cost $27,847 after rebate.

—Ed Marue