View
188
Download
1
Category
Tags:
Preview:
Citation preview
Evaluating Flush and Tilted PV System’s on
Metal Roof Decks
q This webinar will be available afterwards at www.solarpowerworldonline.com & email
q Q&A at the end of the presentation q Hashtag for this webinar: #SolarWebinar
Before We Start
Steven Bushong Solar Power World
Moderator Presenters
Eric Stephenson Advanced Racking Systems
Jonathan Young Advanced Racking Systems
Ø Founded by Eric Stephenson & Ingo Wolfert in 2010 Ø Subsidiary of hb Solar Canada
Ø Maximizing metal roof PV output with smart designs supported by strong validaFon
Ø Installed base of more than 60 MW, almost half metal roof
Product Offering
VICERAIL = Low Slope Corrugated VICERACK = Low Slope Standing Seam SKYRACK = Flush mount on metal or shingle
-‐
VICERAIL (low slope corrugated)
SKYRACK (Flush on SS, Corrugated, Shingle)
Evolution of VICERACK
(low slope Standing seam)
554kW system in CA.
VICERACK PC at 15
degree tilt, skewed
across standing seam.
Unsolicited Installer Feedback:
“So you know your system is without a doubt the
nicest, cleanest, easiest system I've been involved with.”
ü Cost effec)ve ü Accessories for Power
Op)mizers
ü Approved by PE’s
ü Clamps stage easily
ü Base rail on metal roofs
ü Flashing included
SKYRACK flush mount racking for metal / shingle
Top considerations of PV systems on metal roofs
1. Metal roof types? 2. How different racking
configurations affect the structure? 3. How wind & snow affect the PV
system and roof structure? 4. Flush and Tilt systems. 5. Mounting on a North Slope? 6. Summary, how to assess a metal
roof.
Metal Roofs Two main types:
1. Standing Seam, Ø No Penetrations
2. Corrugated = Exposed Fastener = Trapezoid Ø Existing holes / limited new ones
Advantages of Metal roofs Ø Life cycle of 30 – 40 years
Ø Avoid the cost of removing PV system
Ø Durable, Maintenance free
Roofs are not created equal, check capacity with MFG
VICERACK 10 degree tilt
Metals Roof types
Standing Seam Corrugated
Standing Seam Clamps
Dual SS Attachment clips
Single Top portion of the clip moves thermally with the panel since it’s clamped by seam, while the lower portion (fastened to structure) is stationary; the two pieces are joined with a slip joint.
Single component clips rely on differential movement between roof clips and roof panels to accommodate thermal cycling.
Source: S-‐‑5
Corrugated Brackets
Deck Bracket
w/ L Foot
Deck Bracket EJOT w/ L Foot
Versa Bracket
How racking configurations affect the structure?
VICERACK – parallel to seam
VICERACK – Portrait parallel to seam
VICERAIL - Square on seam
VICERACK - skewed on seam
VICERACK– different row spacing
Roofs are designed for
distributed load.
Concentrated loads can
exceed MFG specs and
increase liability.
What to watch out for
•
What we learned
Design Related
• Wind deflector results in pressure equaliza)on drama)cally reducing upliK
• Skewed system reacts differently than arrays square with the building
• How much upliK is your PV system applying, does it conform with the structural limits?
• Is there data to support it?
How wind & snow affect the structure
Wind loads • UpliK on building increased by 50 – 100% without a wind deflector
• Not all roofs are created equal, loads vary greatly
Ø Seam Capacity: 150 lbs – 540lbs
Ø Hold down capacity of seam varies based on loca)on of structure below
1.1 MW VICERACK in NJ
•
Snow loads
Snow Loads • Snow Fence Effect
• Tilted systems are safe in high snow load areas. • Advanced Racking has a successful track record • Worked with RWDI to create snow load tool
Source: Effects of Snowfall on PV Systems, May 2013. Prediction of Energy Effects on Photovoltaic Systems due to Snowfall Events, June 2012. Queens University, Michigan Technological University
• Data supports )lted arrays perform beaer • At lower module angles, snowfall from the previous day will increase the chances of snow adhering.
• Higher )lt angles, approx. 15 degree and above result less annual PV yield loss, and require less )me to clean the system.
Flush & Tilt systems
Flush system on Metal
Portrait modules single rail
Landscape orient with 2 layers of rail
Why Tilt?
$ Increase PV output of South facing arrays $ More direct sun angle $ Improved airflow under the module
$ Utilize the North Slope of the building
$ Improved access for maintenance
Comparison of Tilt Angles
$ Add’l Energy $176792
$ Net increase > $115K
• 6-‐9% ROI
$ Skewed array increase annual produc)on 2 – 4%*
• Increased equip cost = 1 -‐ 2c/w
Assump6on: Flush System equipment cost 10c/w and a Tilted system cost 22c/w, value of energy at .148 / kWh Source: PV Waas and SMA simula)ons Loca6on: Boston, MA * Based on 15 degree )lt, results dependent on la)tude
Maintaining PV Systems $ According to NREL
$ Fixed O&M costs $19 / kW/ yr for 100kW – 1MW
$ Micro-fractures affect performance
$ Cleaning 1 – 2 / year (gravity)
Source: NREL, GTM, SolarPro. Impact of micro-cracks on the degradation of solar cell performance on two diode model parameter, Energy Procedia 2012. Influence of cracks on the local current-voltage parameters of silicon solar cells, Progress in Photovoltaics 2013.
Mounting on a North Slope
VICERAIL
North Slope Array
• Tilt angle 10 – 25
• Larger Inter-row spacing
• Increased Uplift
North Slope PV Output
A 15 degree )lt system on the North Slope generates roughly 70% of the power output of the South Slope system
Assump6on: Using the same Sq K area on a building with a 5 degree roof slope. Source: ARS projects
70
"ʺVICERACK was the perfect
mounting solution. The unique design, supported by 3rd party
testing, satisfied strict local structural & wind loading
requirements. The tilted rack provided just enough boost in
resource for the system to
qualify for state incentives. John Grieser President
h`p://www.elementalenergy.net/
Summary: How to assess a metal roof
Metal roof - common questions • Roof slope? • Standing steam or Corrugated: rib profile? • Substrate construction? • Gauge of metal deck? • Purlin spacing; 5’ common on commercial structures
o Purlins wood or steel?
• Utilize the North Slope? • Load limitations of roof structure? • Are you connecting to the roof deck or structural framing?
Selecting the right racking configuration 1. Attachment Point: Seam or Purlins? 2. Space limitation: Power density vs Increased Efficiency 3. State or local Performance Incentives? 4. System’s expected production: upfront cost vs return 5. Roof structure limitations (Uplift)? 6. Is the Racking system design helping distribute the load? 7. Is preserving the Roof warranty a concern of customer? 8. Data to support your PV system design?
Our
focus at is
your
success.
Thank you.
Questions?
Jonathan Young 540 557-‐‑7811
jonathan@advancedracking.com www.advancedracking.com
Questions? Steven Bushong Solar Power World sbushong@wtwhmedia.com
Eric Stephenson Advanced Racking Systems
Jonathan Young Advanced Racking Systems jonathan@advancedracking.com www.advancedracking.com Phone: 540 557-7811
q This webinar will be available at www.solarpowerworldonline.com & email
q Tweet with hashtag #SolarWebinar
q Connect with Solar Power World
q Discuss this topic on EngineeringExchange.com
Thank You
Recommended