Raising the Bar: Wind-Caused Solar Tracker Failure Is Not an Option

By on August 28, 2018

Reliable solar trackers don’t come easy. It takes a lot of blood, sweat and tears to enter the market with a dependable system. Tracking system development involves extensive research, testing and complex engineering that extends far beyond the reach of published standards. People often forget that building codes and other related standards represent minimum requirements, not optimal reliability and performance. When you apply that understanding to a relatively new structure type like trackers, you have a potential recipe for failure that can occur well before owner expectations. 

When it comes to wind engineering and analysis, we believe that no other tracker company has the depth of knowledge that NEXTracker does. We invested in the pioneering wind tunnel R&D work done by David Banks and his team at CPP, which investigated torsional instability, vortex lock-in and other factors in single-axis trackers and demonstrated the critical importance of analyzing not just the static but the dynamic effect or impact of wind on PV structures.

One such dynamic effect can be modeled through computational fluid dynamics (CFD) analysis only after wind tunnel testing is completed to emulate the loads on a panel. Research shows that the best way to combat tracker instability is through stow angles and proper damping. In this video below, the CFD analysis demonstrates vortex shedding on one side of the panel.

The findings of this testing and body of research guided us in the robust design of our current NX HorizonTM system,  which to date, has had no reported wind-related failures in the field. We have also conducted in-depth, site-specific wind engineering studies in Australia, India, Latin America and other regions where our systems have been or will be deployed in ever-greater numbers.

But the importance of diligent wind engineering analysis extends beyond our own work at NEXTracker. That’s why we’ve put together a white paper as a resource for informed developers and asset owners looking at more than upfront cost. To understand the true expected reliability of systems with design lives of 25-35 years, advanced dynamic wind analysis of each tracker system is critical in predicting required operations and maintenance costs and facilitating the continued success of utility and large-scale distributed generation solar around the world.

The paper addresses the importance and challenges of comprehensive wind engineering, presents examples of the pioneering wind tunnel analysis conducted by CPP and NEXTracker, discusses the potential impact of different stowing approaches as well as tracker design architectures, and looks at the LCOE implications of proper wind engineering practices. The paper also provides suggestions and recommendations for solar developers, EPCs and owners to consider when they are choosing their tracker supplier.  

We’re not the only ones that recognize the importance of thorough wind-engineering and analysis. DNV GL’s new white paper, “Tracker Bankability Reviews: Guidelines for Stakeholders,” devotes a substantial portion of its recommendations toward wind tunnel testing, structural validation and analysis, and tracking algorithm and stow requirements.

This is music to our ears at NEXTracker since we have been investing considerable resources in these and other areas discussed in the paper and are meeting or exceeding the criteria laid out by DNV. Of course, this is not just a NEXTracker-specific set of challenges and necessities. In order to manage this key variable and mitigate risk for our customers, we encourage all PV structure companies to complete wind tunnel studies and understand the static and especially the dynamic wind loads on their equipment so they can ensure reliable long-term operation. 

We’ll be publishing our white paper the week of September 17, followed by a GTM webinar on September 18 titled “Designing for Wind in the Age of Mass Solar Tracker Deployment.” You can register for this free webinar here; we’d love to get a lively discussion going on this topic during the Q&A session!

We will also be participating in PV magazine’s Quality Roundtable during Solar Power International 2018 in Anaheim, where we will share more of our wind engineering analyses and observations. Stay tuned for more details in the coming weeks.

Lastly, if you’ve made it this far, drop me a line on LinkedIn. I’m interested in watching how the field of wind design engineering develops and would like to hear your stories.