Evaluating Flush and Tilted PV System’s on

Metal Roof Decks

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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

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