One-axis tracking for large-scale ground-mounted solar is "a no-brainer," according to Dan Shugar, CEO of tracker firm NEXTracker, who called it the "dominant" mounting structure in that space. Kate Trono, VP of products at SunLink, believes a centralized tracker architecture is "the right solution for the preponderance of projects in the U.S." Bob Bellemare, CFO at tracker leader Array Technologies, says his firm "focuses on simplicity and ease of installation."

These three tracker execs met last week on a panel at Greentech Media's U.S. Solar Market Insight conference in San Diego, Calif.

Bellemare pointed out the varying design and engineering philosophies, saying, "The most we have in common is we track east to west."

Trackers can improve solar output by 20 percent in Las Vegas and 30 percent in Chile, said Shugar, at what is approaching a single-digit premium to fixed tilt. At the same time, trackers help provide a better match to utility load.

MJ Shiao, panel moderator and director at GTM Research, notes, "Tracking, specifically horizontal single-axis tracking, continues to be the fastest-growing structural [balance-of-system] component and is expected to make up nearly 20 percent of ground-mount projects installed globally this year. The U.S. leads this market, where over 60 percent of ground-mount projects are installed with trackers -- and that share is growing. We expect the market for trackers will reach nearly $5 billion by 2020."

Array Technologies

Array Technologies shipped more than 500 megawatts in 2014 and is now shipping 300 to 500 megawatts per month, according to Bellemare. GTM Research notes that "for many years, ATI was the only 'bankable' tracking product, and it remains the largest third-party tracking manufacturer globally." Array Technologies expects to deliver nearly 4 gigawatts of trackers between mid-year 2015 through the end of 2016.   

Bellemare notes that the firm has been around for 25 years and has been solely focused on trackers and tracker design. The company has shipped a cumulative 4 gigawatts of its centralized design and will ship "enough to cover 40 to 50 square miles of land surface in the next year."

He notes that the company uses "no sensors -- we feel like that's a break point." He said the firm uses fewer parts -- "half the bolts of other trackers" with "two motors per megawatt, connected by a flexible drive line to track all types of terrain." Bellemare said, "We focused on taking the maintenance out of the system," suggesting that the firm's tracker "does not require any routine maintenance."

He noted that several of the firm's trackers were in the path of Hurricane Sandy and "all survived," adding, "We design for the unusual and assume the improbable and unlikely will happen."    

SunLink

SunLink's Kate Trono discussed the firm's design decision to go toward the most centralized solution possible with its hydraulically-actuated system. Trono suggested that the many large, flat sites in the U.S. favor a centralized approach that "expedites commissioning" and "reduces O&M." She said SunLink's offering is "the right solution for the preponderance of projects in the U.S."

Trono sees her firm's goal as "making solar more valuable" and providing the owner with insight into O&M and maintenance and ultimately lowering the cost of solar by employing "as big a block as possible."

She said that the choice of tracking "depends on the project. On a site with extreme terrain variation, with challenges like that, a distributed architecture is the way to go."

Still, for Trono, "Centralized is for massive utility scale. The right projects require the right solutions."

NEXTracker 

Solar tracker startup NEXTracker was recently acquired by Flextronics for up to $330 million. The company shipped 275 megawatts in 2014 and now has 1.8 gigawatts of trackers operating and under construction. NEXTracker expects to deliver over 2 gigawatts in 2015 and has large supply agreements with SunEdison and Blattner Energy.

The firm is now shipping 100 megawatts' worth of products per week; CEO Dan Shugar said it took the first 12 years of his career to get to a cumulative 100 megawatts.

NEXTracker uses an unlinked tracker architecture, unlike the linked scheme and centralized architecture used by SunLink and Array Technologies.

Shugar rattled off the advantages of his firm's design: maintenance costs are lower, it's easier to clean, it can be driven through, grading requirements are decreased -- but the most prominent edge that NEXTracker has is: "We [need] less steel, and at the end of the day, we win on less steel."

In a previous interview, Shugar said, "Virtually every tracker system uses a mechanical interlock -- and that hasn't evolved a lot." He said that when his team was hammering out the requirements for their new tracker design, they determined that "it needed to be individually driven, not interlocked (think Venetian blinds)."

Shugar told the U.S. SMI crowd, "We measure the angle of every row in real time and measure to one-tenth of a degree."

"NEXTracker uses the exact data collection systems used by utility smart meters (ZigBee wireless protocol with mesh network), and archives data in the same database system used by 100% of the utility [independent system operators]. We use 'closed loop control,' meaning the angle of each row is measured and used to exactly control its angle. Those angles, plus other important things like the health of the motor, are measured, reported, and stored with the same integrity as utility data. We believe the world has moved to more accountability, and when power-plant assets are now in the hundreds of millions of dollars on some plants, real data on key metrics is essential to financing and optimum performance," wrote Shugar in a follow-up email.

Shugar told the conference audience, "We must track to take [solar] to the next level...[and] get rid of the duck curve."