Transcription
ASCE 7-16: Changes to WindCalculations for Rooftop SolarJoe Cain, P.E.Chair, SEIA Codes &Standards Working GroupDavid Banks, PhD, P.EngPrincipalCermak Peterka Petersen (CPP)
ASCE 7-16: Changes to Wind CalculationsAgenda Market Trends Current Practice General changes toASCE 7-16 Solar-specificchanges to ASCE Mitigations inSEAOC PV2 updateOctober 14, 2016 2016 Solar Energy Industries Association 2
Residential Market Trends 2010 to 2016July 11, 2017 2016 Solar Energy Industries Association 3
Calculation of Wind Pressure: ASCE 7-10 and ICC-ES AC 428 October 14, 2016Determine design wind speed and calculatedesign wind pressures using ASCE 7-10ICC Evaluation Services Acceptance CriteriaAC 428: Acceptance Criteria for ModularFraming Systems Used To SupportPhotovoltaic (PV) PanelsAC 428 is required to obtain an ICC-ESEvaluation Report; it is also useful asvoluntary guidanceAC 428 allows internal pressure set equal tozero (within constraints) in Components &Cladding methodIn future ASCE 7-16, there will be acalculation method specific to “flushmounted” PV systems on sloping “pitched”roofs 2016 Solar Energy Industries Association 4
ICC Acceptance Criteria AC 428 Components & Claddingmethod Internal pressure shall be setequal to zero Physical constraints areneeded for method to be valid Pressure equalization isdependent on gaps betweenmodulesOctober 14, 2016 2016 Solar Energy Industries Association 5
ASCE 7-10 with ICC-ES AC 428 CriteriaDon’t forget to consider: Roof edge zones, whichare changing in ASCE 7-16 Fire setbacks, which arechanging (for the better) in2018 IFC & IRCPhysical constraints of AC 428 wind method: Required 10 inch minimum distance from roof edge or ridge Height above roof between 2 inches and 10 inches Minimum gap of 0.25 inch between adjacent rows of panels In earlier version of AC 428, minimum gap was 0.75 inchOctober 14, 2016 2016 Solar Energy Industries Association 6
ASCE 7-16 Wind Speed Maps Revised (again) Risk Category II MeanRecurrenceInterval (MRI)700 years) ASCE 7-16wind speedmaps showcontour lines inWestern statesOctober 14, 2016 2016 Solar Energy Industries Association 7
C&C Roof Zones: ASCE 7-10 to 7-16ASCE 7-10 Figure 30.4-2COctober 14, 2016ASCE 7-16 Figure 30.43-2D 2016 Solar Energy Industries Association 8
Development of Corner & Edge Roof ZonesASCE 7-10 Roof ZonesOctober 14, 2016ASCE 7-16 Roof Zones 2016 Solar Energy Industries Association 9
Roof GCp Coefficients: ASCE 7-10 to 7-16ASCE 7-16Figure30.43-2DASCE 7-10 Figure 30.4-2COctober 14, 2016 2016 Solar Energy Industries Association 10
University of Western Ontario: Stenabaugh Experiments wereconducted in UWOboundary layerwind tunnel Two primary areasof investigation Height of PVsystem above roof Pressureequalization fromvarious gapsbetween PV panelsOctober 14, 2016 2016 Solar Energy Industries Association 11
University of Western Ontario - StenabaughOctober 14, 2016 2016 Solar Energy Industries Association 12
ASCE 7-16 with “Associated Criteria”Physical constraints ofASCE 7-16 method: Required minimumdistance from roofedge or ridge 2h2 Height above roofbetween 2 inchesand 10 inches Minimum gap of0.25 inch betweenall panelsOctober 14, 2016 2016 Solar Energy Industries Association 13
DRAFT ASCE 7-16 Section 29.4.4 Basic form of Equation29.4-7 is very familiar Velocity pressure qhtimes pressurecoefficient GCp New coefficients gE andga are solar-specific for“flush mounts” installedparallel to roofOctober 14, 2016 2016 Solar Energy Industries Association 14
Zone 1: ASCE 7-16 GCp Pressure CoefficientsOctober 14, 2016 2016 Solar Energy Industries Association 15
Zone 1: Wind Pressure Equalization FactorOctober 14, 2016 2016 Solar Energy Industries Association 16
Zone 1: Add ASCE 7-16 CA Wind SpeedsOctober 14, 2016 2016 Solar Energy Industries Association 17
Zone 1: Closer to Roof, with PV2-2016 EqualizationOctober 14, 2016 2016 Solar Energy Industries Association 18
DRAFT Update to SEAOC PV2 Wind Paper Original SEAOC PV 2 wind paper waspublished in October 2012 Dr. David Banks of CPP Wind isprimary author of PV2 update PV2 paper is updated to allrequirements of ASCE 7-16 Updated PV2 is expected to bepublished by the end of 2016 ASCE 7-16 intended to be referencedin the 2018 IBC, and in effect byJanuary 1, 2020 in most statesOctober 14, 2016 2016 Solar Energy Industries Association 19
ASCE 7-16: Exploring the Edge Factor, gE Edge Factor gE (“gammaE”) is a direct, linearmultiplier to the windpressure The value of gE is either1.5 or 1.0 In ASCE 7-16, panelswithin 1.5 Lp from end ofrow are exposed Result is three rows orfewer are 100% edgeOctober 14, 2016 2016 Solar Energy Industries Association 20
Mitigation for gE in (DRAFT) SEAOC PV2 UpdateFlush mount onlyLikely to be 2*h2from array edge infinal PV2-2016October 14, 2016 2016 Solar Energy Industries Association 21
ASCE 7-16: PV Pressure Equalization Factor, ga EqualizationFactor ga is adirect multiplier towind pressure Wind pressure isreduced for gapsbetween panels John Wolfe publiccomment wasdisapproved bythe ASCE WindSubcommitteeOctober 14, 2016 2016 Solar Energy Industries Association 22
Mitigation for ga in DRAFT SEAOC PV2 Update SEAOC PV2 update will includemore options for pressureequalization Options are height of PVsystem above roof and gapsbetween modules This alternative method rewardsdesigns that consideroptimization for wind Wind pressures can be reducedby 25 percent from worst-casebasis of ASCE 7-16October 14, 2016 2016 Solar Energy Industries Association 23
Questions?ContactsCodes & Standards:Joe Cain, P.E.Chair, SEIA Codes & StandardsWorking GroupE-mail: JoeCainPE@gmail.comPhone: 1-408-605-3934David Banks, PhD, P.EngPrincipal, CPP WindE-mail: dbanks@cppwind.comPhone: 1-970-498-2350October 14, 2016 2016 Solar Energy Industries Association 24
Development of Corner & Edge Roof ZonesOctober 14, 2016 2016 Solar Energy Industries Association 25
Development of Corner & Edge Roof ZonesOctober 14, 2016 2016 Solar Energy Industries Association 26
Calculation of Wind Pressure: ASCE 7-10 and ICC-ES AC 428 Determine design wind speed and calculate design wind pressures using ASCE 7-10 ICC Evaluation Services Acceptance Criteria AC 428: Acceptance Criteria for Modular Framing Systems Used To Support Photovol
