energy.gov/sunshot	
  

energy.gov/sunshot	
  

Tes$ng	
  for	
  PV	
  Reliability	
  	
  

Test	
  types	
  and	
  Test	
  gaps	
  

Sarah	
  Kurtz,	
  NREL;	
  	
  

Shubhra Bansal,	
  DOE	
  

NREL/PR-­‐5J00-­‐62779	
  

2014	
  SunShot	
  Workshop	
  

Golden,	
  Colorado	
  

September	
  9,	
  2014	
  
energy.gov/sunshot	
  

• Types	
  of	
  tests	
  

• Purpose	
  

• Stresses	
  

• Sample	
  size	
  

• Some	
  important	
  gaps	
  (out	
  of	
  a	
  much	
  longer	
  list)	
  	
  

• In-­‐field	
  detecTon	
  

• PID	
  in	
  qualificaTon	
  test	
  

• Soiling	
  

• Corrosion	
  and	
  adhesion	
  

• Reduced	
  cost	
  through	
  use	
  of	
  mini	
  modules?	
  

• What	
  does	
  success	
  look	
  like?	
  

Outline:	
  
energy.gov/sunshot	
  

• Purpose:	
  

• LifeTme	
  	
  

• QualificaTon	
  (during	
  design	
  or	
  during	
  manufacturing)	
  

• Process	
  control	
  	
  

• Failure	
  detecTon/analysis	
  

• Choice	
  of	
  stresses	
  

• Single	
  stress	
  	
  

• Combined	
  stress	
  (sequenTal	
  or	
  simultaneous)	
  

• MulTple	
  stress	
  levels	
  (can	
  define	
  acceleraTon	
  factors)	
  

• Sample	
  size	
  or	
  point	
  in	
  manufacturing	
  process:	
  

• Material	
  or	
  component	
  

• Mini-­‐module	
  

• Module	
  

Overview:	
  Types	
  of	
  tests	
  –	
  Lots	
  of	
  needs	
  

Following slides identify gaps for different types of tests 
energy.gov/sunshot	
  

• Cracked	
  cells	
  can	
  become	
  disconnected	
  from	
  circuit	
  and	
  

cause	
  serious	
  failures	
  a[er	
  thermal	
  cycling	
  in	
  the	
  field	
  

• Gap:	
  	
  How	
  do	
  we	
  idenTfy	
  modules	
  that	
  have	
  been	
  

damaged	
  (impending	
  failures)?	
  	
  (Drones	
  with	
  EL	
  or	
  

thermography?)	
  What	
  are	
  pass/fail	
  criteria?	
  	
  

In-­‐field	
  failure	
  detec$on	
  –	
  Gap:	
  standard	
  test	
  
energy.gov/sunshot	
  

• Voltage-­‐driven	
  current	
  flow	
  through	
  the	
  glass	
  can	
  cause	
  

large	
  degradaTon	
  

• Can	
  easily	
  be	
  tested	
  in	
  a	
  chamber	
  with	
  high	
  humidity,	
  

temperature	
  and	
  bias.	
  

• Gap:	
  	
  Important	
  to	
  have	
  material	
  (encapsulant)	
  and	
  

component	
  (cell)	
  level	
  tests	
  for	
  quality	
  control	
  

• Gap:	
  	
  Understanding	
  of	
  in-­‐field	
  degradaTon	
  and	
  recovery	
  

to	
  be	
  able	
  to	
  model	
  effects	
  related	
  to	
  chamber	
  tesTng	
  	
  

• Gap:	
  	
  Complete	
  qualificaTon	
  test	
  by	
  developing	
  consensus	
  

around	
  the	
  (use-­‐dependent?)	
  pass/fail	
  criteria!	
  

Poten$al-­‐induced	
  degrada$on	
  –	
  Mul$ple	
  gaps	
  
energy.gov/sunshot	
  

• Soiling	
  can	
  lead	
  to	
  large	
  uncertainty	
  in	
  system	
  output	
  

• Tests	
  are	
  needed	
  for:	
  

• SuscepTbility	
  of	
  surface	
  to	
  soiling	
  under	
  different	
  

condiTons	
  

• Durability	
  of	
  anT-­‐reflecTon	
  coaTngs	
  to	
  the	
  abrasion	
  

associated	
  with	
  cleaning	
  and/or	
  sand	
  blasTng	
  from	
  windy	
  

desert	
  condiTons.	
  

• Understanding	
  local	
  condiTons	
  

Soiling	
  –	
  Gaps:	
  predic$ons	
  and	
  mul$ple	
  tests	
  
energy.gov/sunshot	
  

• Corrosion	
  may	
  be	
  a	
  mulT-­‐step	
  process:	
  

• UV	
  exposure	
  weakens	
  the	
  EVA-­‐glass	
  bonds	
  

• EVA	
  absorbs	
  moisture	
  

• Freezing	
  expands	
  moisture	
  and	
  causes	
  delaminaTon	
  

• Drops	
  of	
  water	
  enter	
  module	
  and	
  causes	
  corrosion	
  

Corrosion	
  –	
  Gaps:	
  adhesion	
  and	
  combined	
  stress	
  

Gap: Understand subtleties of 

combined stresses 

Gap: Quantify adhesion between 

encapsulant and cell 
energy.gov/sunshot	
  

• Sample	
  size:	
  

• Material	
  –	
  lowest	
  cost,	
  but	
  is	
  it	
  relevant?	
  

• Mini-­‐module	
  

• Module	
  –	
  highest	
  cost,	
  but	
  most	
  relevant	
  

• Example:	
  	
  Backsheet

• UV	
  irradiaTon	
  of	
  full	
  module	
  is	
  expensive	
  

• But,	
  some	
  backsheet	
  failures	
  depend	
  on	
  the	
  size	
  of	
  the	
  

sample:	
  	
  thermal	
  expansion	
  differences	
  may	
  cause	
  

backsheet	
  to	
  pull	
  away	
  in	
  a	
  full	
  size	
  module.	
  

• Is	
  a	
  mini-­‐module	
  a	
  useful	
  compromise??	
  

• Gap:	
  	
  How	
  to	
  fully	
  test	
  a	
  backsheet’s	
  funcTon	
  in	
  a	
  

module	
  without	
  prolonged	
  UV	
  exposure	
  of	
  a	
  full	
  module	
  

Which	
  size	
  to	
  use?	
  
energy.gov/sunshot	
  

• Give	
  quanTtaTve	
  indicaTon	
  of	
  lifeTme	
  

• Uncover	
  all	
  relevant	
  failure	
  modes	
  

• Avoid	
  sTmulaTng	
  unwanted	
  failure	
  modes	
  

• Be	
  completed	
  quickly	
  	
  

• For	
  new	
  product	
  launch:	
  	
  <	
  6	
  months	
  

• For	
  process	
  control:	
  <	
  1	
  day	
  

• Low	
  cost	
  

• As	
  low	
  as	
  possible:	
  <	
  1%	
  of	
  total	
  cost?	
  

If	
  our	
  goal	
  is	
  a	
  set	
  of	
  ideal	
  tests,	
  then	
  we	
  have	
  gaps	
  everywhere!	
  

Biggest	
  opportuni?es	
  today	
  will:	
  	
  

•	
  Reduce	
  failures	
  in	
  the	
  field	
  (improved	
  design	
  qualifica?on	
  and	
  

improved	
  quality	
  control)	
  

•	
  Reduce	
  ?me	
  (and	
  cost)	
  to	
  bring	
  a	
  new	
  product	
  to	
  market	
  

Ideal	
  tests	
  –	
  what	
  does	
  success	
  look	
  like?	
  
energy.gov/sunshot	
  

Breakout	
  Session	
  2	
  

Degradation or Failure 

Mode 

Inadequacy in Testing 

Protocols 

Needs for DOE funding 

• Breakout	
  session	
  2	
  on	
  Gaps	
  in	
  TesTng	
  Protocols	
  

• Worksheets	
  with	
  pre-­‐populated	
  degradaTon	
  modes	
  will	
  be	
  provided	
  	
  

• Please	
  idenTfy	
  the	
  gaps	
  or	
  inadequacies	
  in	
  tesTng	
  protocols	
  

• Tests	
  can	
  be	
  accelerated	
  test	
  protocols,	
  need	
  for	
  field	
  tesTng,	
  characterizaTon	
  needs,	
  

metrology	
  needs,	
  etc.	
  (maybe	
  mulTple	
  gaps	
  per	
  failure	
  mode	
  –	
  see	
  next	
  slide)	
  

• If	
  there	
  is	
  a	
  need	
  for	
  test	
  standard,	
  please	
  idenTfy	
  

• In	
  the	
  3rd	
  column,	
  please	
  idenTfy	
  if	
  there	
  is	
  a	
  need	
  for	
  DOE	
  funding.	
  	
  

• If	
  “yes”	
  how	
  can	
  DOE	
  funding	
  be	
  most	
  impacmul?	
  	
  

• How	
  can	
  industry	
  best	
  leverage	
  DOE	
  funding?	
  

• Are	
  there	
  ways	
  DOE	
  can	
  help	
  facilitate	
  data	
  sharing,	
  collaboraTons,	
  etc.?	
  
energy.gov/sunshot	
  

• Voltage-­‐driven	
  current	
  flow	
  through	
  the	
  glass	
  can	
  cause	
  

large	
  degradaTon	
  

• Can	
  easily	
  be	
  tested	
  in	
  a	
  chamber	
  with	
  high	
  humidity,	
  

temperature	
  and	
  bias.	
  

• Gap:	
  	
  Important	
  to	
  have	
  material	
  (encapsulant)	
  and	
  

component	
  (cell)	
  level	
  tests	
  for	
  quality	
  control	
  

• Gap:	
  	
  Understanding	
  of	
  in-­‐field	
  degradaTon	
  and	
  recovery	
  

to	
  be	
  able	
  to	
  model	
  effects	
  related	
  to	
  chamber	
  tesTng	
  	
  

• Gap:	
  	
  Complete	
  qualificaTon	
  test	
  by	
  developing	
  consensus	
  

around	
  the	
  (use-­‐dependent?)	
  pass/fail	
  criteria!	
  

PID	
  –	
  Shows	
  example	
  of	
  mul$ple	
  tes$ng	
  gaps