How to Handle High Winds
October 8, 2015
No one in the industry has invested more time and money than SunLink in understanding the effects of wind on solar arrays, and how to mitigate the challenges those wind loads pose. But what do the more than 1000 wind tunnel runs; hundreds of different array, building and site models; and several of the world’s leading boundary layer wind tunnels and industry-leading experts mean for our customers?
LinkUp sat down with VP of Engineering Rob Ward to talk about how our rigorous R&D program informs our roof-mount product and project engineering, ensuring installations that are safer and built to stand both the test of time and the toughest forces Mother Nature can conjure.
“One of the most important outcomes of our testing is confirmation that wind loads over small areas on a roof are much higher than many in the industry think. Wind pressures on tilted modules result in forces that are both horizontal – drag – and vertical – uplift. Plus, wind blowing across an array is gusty – meaning that locally high transient pressures will occur.”
Rob emphasizes that understanding winds behavior and the “what if” scenarios has to drive system design.
“At SunLink, as our name implies, we design our Precision RMS systems to withstand wind loads by linking our components together with load sharing in mind. A typical array of interlinked modules may have enough interconnection stiffness to share the drag component of the wind loads, but without sufficient uplift load sharing, it would have to be excessively heavy or heavily connected in order to be designed safely. The key to getting good performance while minimizing the overall weight of the racking system is to provide sufficient uplift load sharing stiffness.”
Rob gave LinkUp a hands-on demonstration of the load sharing concept using a model of Precision RMS.
“Precision RMS builds in the industry’s best uplift load sharing by panelizing modules with Spars, and then interlinking the panels in 2 links per panel, both in the east-west and north-south directions. The racking does all the work, not the modules.”
Without a doubt, proper design depends on thorough wind tunnel testing and solid data, but what does our project engineering team actually do with all that data when designing a Precision RMS project? Rob says that engineering a roof mount project requires an appropriate level of analysis, looking at racking forces and response to wind loads.
“At SunLink we have developed sophisticated software that uses our extensive wind tunnel data together with full-scale system calibration to model each project’s configuration and rooftop environment. Precision RMS offer a huge amount of design flexibility in terms of tilt, row spacing, panel sizes and layout, but with our software we can quickly get an accurate, non-linear structural analysis model for every array we build.
We’re able to apply numerous wind load cases to each array to check capacity for those highly concentrated gust loads. It’s all part of ensuring that our installations are designed to withstand even the most punishing environmental loads. We take pride in preparing for the expected and the unexpected!”