News

Gone With The Wind – No More!

Wind-related failures over the past several years of both roof- and ground-mounted arrays of photovoltaic panels have put a damper on an otherwise booming market segment.

Solar panel builders, manufacturers, and structural engineers have struggled to understand the dynamics of these systems which have a unique geometry, weight, and method of connection to a building. With no established guidelines or codes addressing the impact of design wind loads on these types of systems, they have literally been operating in the dark as they tried to keep up with the demand for these popular energy-saving systems.

That’s about to change in 2016 when new codes are incorporated into the International Building Code (IBC / ASCE 7-10). These code changes are the result of work done over the past several years by the Photovoltaic Systems Committee of the Structural Engineers Association of California to address this problem. The committee, which is comprised of consulting structural engineers, building officials, industry members, wind tunnel research experts, members of national code committees, and the SEAOC seismology committee, developed these proposed changes to ASCE 7-10:
• Adding a Section 29.9 to address solar arrays on flat or low-slope roofs;
• Modifying Table 29.1-1 to include solar arrays;
• Adding a Figure 29.9-1 to define prescriptive wind pressure coefficients for solar arrays;
• Adding a definition of Effective Wind Area for solar arrays;
• Adding a Section 31.6 to address wind tunnel testing of solar arrays.

Establishing new industry standards with these code changes should go a long way toward removing any uncertainty in the marketplace and restoring consumer confidence about the design integrity of ground- and roof-mounted arrays of solar PV systems.

Photos showing typical wind damage to rooftop-mounted solar photovoltaic arrays: (Above left) Construction worker inspecting roof-mounted solar photovoltaic arrays on commercial building. Courtesy SolarPro |June/July 2012 / Shawn Schreiner. (Top right) Wind damage to roof-mounted solar photovoltaic arrays on commercial building due to improper installation. Courtesy SolarPro |June/July 2012 / BEW Engineering. (Above) Wind damage caused rooftop solar panels to collapse atop a residential building in Toronto. Courtesy CTV Toronto Wind damage caused rooftop solar panels to collapse atop a residential building in Toronto. Courtesy CTV Toronto Courtesy SolarPro |June/July 2012 / Shawn Schreiner


RELATED LINKS

http://www.documents.dgs.ca.gov/dsa/dsaab/csc04-12-12_agenda-Item-5B_SEAOC-WindLoad.pdf
http://www.seaoc.org/bookstore/wind-design-low-profile-solar-photovoltaic-arrays-flat-roofs-seaoc-report-pv2-2012
http://www.seaoc.org/bookstore/seismic-structural-requirements-and-commentary-rooftop-solar-photovoltaic-arrays-seaoc
http://www.solarindustrymag.com/issues/SI1304/FEAT_01_How_Structural.html
http://solarprofessional.com/articles/design-installation/wind-load-analysis-for-commercial-roof-mounted-arrays