The Long Read: Back to the Drawing Board

By Marian Willuhn | January 18, 2020 | Read the full article published on PV Magazine here. 

The combined use of trackers and bifacial modules can result in significant power gains, but they are not distributed equally. For single-axis tracking R&D teams, the process of optimizing the output from arrays that use bifacial modules requires experimentation and a steep learning curve in terms of what is going on underneath the module.

With monofacial PV modules and trackers now on the market for decades, the industry has had ample time to optimize the two. There is little theoretical uncertainty in terms of performance, and over the past year, global annual tracker installations have increased by a margin of 40% to reach more than 20 GW, according to IHS Markit. That number is set to grow at record speeds, analysts say, not least because of the assumed symbiosis of single-axis tracking and bifacial modules.

This symbiosis, however, is still in its infancy. While suppliers of trackers and modules tout monumental yield gains of up to 30%, the reality remains unclear, and a precise figure for the power gains that can be achieved is not easily arrived at.

In pursuit of an answer to the question of how much power output can be expected, tracker suppliers around the globe have teamed up with renowned solar research institutes. These efforts extend beyond front-side yield optimization to an understanding of what actually happens on the rear of the module.

Among those tracker suppliers is U.S.-based Nextracker. The company’s CEO, Dan Shugar, says that he was first introduced to the idea of bifacial modules in 1991; as early as 2007, his company supplied dual-axis trackers to the 14 MW Nellis project, near Las Vegas. Commissioned 12 years ago, the site was the country’s largest utility-scale array at the time, and around 20% of the modules supplied to the site were bifacial. Shugar says that Powerlight, the company he worked at before NExtracker, already in 2007, had supplied a purpose-built bifacial tracker. A lot of testing and validation went into bifacial designs at that time, and definitely more has in the interim, he adds.