The art of tracking the sun
Tracking the sun’s daily course from east to west to harness its energy and generate solar power may seem like a simple concept, but in reality it’s a complicated process that requires the application of advanced technology. Among the solar tracking technologies there are a few different architectures – and they are as dissimilar as they are complex.
“The only thing we have in common with other trackers is that we track the sun east to west,” said Bob Bellemare, chief financial officer for Array Technologies. “The fundamentals of how we do it are radically different.”
Array Technologies’ approach to solar tracking is informed by decades of experience and innovation. It’s guided by the philosophy that less is more and that high quality is what will withstand the years and the impacts of the environment. Its technology is differentiated by intense integration of function in the design.
“In our architecture, one industrial-grade, high-quality motor is linked to many rows, and that motor can drive 28 rows with up to 90 solar panels in each row,” Bellemare said. “By linking the rows together with a driveline that spins a gear on each row, you greatly reduce the number of failure-sensitive components involved in your solar field.”
That distinction is critical, because the more components in a tracker, the greater the possibility of mechanical breakdown and system failure. By contrast, trackers with individually driven rows feature separate motors, controllers and other components to drive each row—requiring tens of thousands of additional electromechanical components which greatly increase the possibility of failure.
That failure becomes critical when a tracker that must stow flat to survive a wind event doesn’t, because one link in a chain of components stops working.
“You’re dealing with a lot of components in each row of panels over a big field—for example, a 100 megawatt project typically has 200 miles of solar trackers,” Bellemare said. “The trackers must be in the stow position to avoid destruction from heavy winds, and with more system components, there’s a higher probability of one or more failures.”
Array Technologies’ tracker architecture, meanwhile, is built not to stow, but to survive. “We take a mechanical approach and employ a torsion limiter in our trackers,” Bellemare said. “When the load reaches a certain point, the gears of the tracker will disengage and the structure will float to the best position for the modules to effectively shed the wind force. The force of the wind is therefore transferred through the structure and shared evenly across the supports to mitigate potential damage.”
That focus on survivability translates to less stress on the installation over time—which is critically important, considering that trackers spend 20 to 30 years in the field. The design focus on low stress is also one of the factors that differentiates Array Technologies’ linked row approach from the push-pull tracker, an architecture in which the solar array is moved by a lever that pushes and pulls through the center of the array.
“A push-pull tracker design requires a lot of steel and an incredible amount of force in the center of the solar array,” Bellemare said. “The design needs very high precision installation and requires more structural material, which is cumbersome to install and again means more maintenance for the end user.”
Array Technologies designs its architecture around low risk and low operating and maintenance requirements, which leads to lowest cost of energy over time. Thanks to a rotating mechanical driveline, there is a high level of flexibility inherent to the system. “The driveline we use is very unique,” Bellemare said. “It has a u-joint that has flexibility up, down, left and right, basically 40 degrees in any direction, which the push-pull architecture cannot achieve. So our tracker can follow terrain – up and down hills and slopes.”
As compared to both push-pull and individually driven row architecture for solar trackers, Array Technologies gravitates toward engineered simplicity. “We don’t need the extraneous instrumentation that other products require,” Bellemare said. “Overcomplicated instrumentation leads to more failure points. We’ve worked hard to eliminate all that opportunity for failure from our elegantly simple, streamlined architecture.”