Solar Durability Workshop
How PV Standards Developed
Case Study: Hot Spot Endurance Test
Liang Ji
Corporate Research, UL LLC
April 9, 2012
Case Western Reserve University, Cleveland, Ohio
Copyright© 1995-2007 Underwriters Laboratories Inc. All rights reserved. No portion of this material may be reprinted
in any form without the express written permission of Underwriters Laboratories Inc. or as otherwise provided in writing.
Standard Development Cycle
Development Revision
Research Analysis
Market Surveillance
Testing Certification
Factory Auditing
UL have all 5 pillars in this cycle.
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PV Test Standard
PV test standards have several challenges.
For example:
• Fast moving technology vs. lengthy
standard development process;
• R&R: Repeatability and Reproducibility,
especially for outdoor testing;
• Long system operation lifetime vs. demand
for quick certification to market;
• Highly accelerated stress test vs. keeping in
the similar failure mode.
3
Hot Spot and Bypass Diode
Without bypass diode,
the heat dissipation Q
from shaded cell is:
P3N-1
P3N-1
N
N
+
N
_
short circuit module
P~η
PN-1
Q ~ ∆T, A
N
With 3 bypass diodes,
the heat dissipation Q
from shaded cell is
reduced to: PN-1
N
_
+
short circuit module
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Field Failures
Before JPL Block V, 1981
• No requirement for hot spot
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UL1703: Test Equipment
UL 1703 Ed.1-1986, Ed.2-1993, Ed.3-2002
• Three cells, 1hr on - 0.5hr off
• Total 100hrs on time
• Indoor test with temperature control
• Use external power supply to provide
maximum heat dissipation energy.
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3
UL1703: Test Failures
7
IEC 61215 History and Current
Very few test
failures.
Not reflect field
failure problem.
IEC 61215 Ed.1-1993
• One cell, 1hr on - 0.5hr off, total 5hrs
IEC 61215 Ed.2-2005
• One cell, 5hrs on - no off (may in two days)
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4
IEC61215 Ed.3 (Draft 2011-11)
Module char acteristi cs
wi th one cell total ly shaded
3. 5
Cur rent-voltage characteri stic
of the non -shaded modul e
Byp ass diode
turns on
Test 4 cells:
3 with lowest Rshunt,
1 with highest Rshunt.
2
Cel l w ith hi ghest
leakag e cur ren t
1. 5
1
0. 5
0
0
5
10
15
20
25
Module vol tage in Vol ts
Current-v ol tage c haracteri sti c
of the non-shaded module
3.5
3
Module current in Amps
Module current in Amps
3
2. 5
Module charac ter istics
with the te st cel l shaded:
a) 100%, b) 75 %
c) ma x. power diss ipati on
ISC
Adjust shaded area to
get maximum power
dissipation.
2.5
IMP
c)
On time: 1-5 hours.
2
1.5
b)
1
I1 00
a)
0.5
0
0
5
10
15
Module volta ge in Volts
20
25
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Contact
Liang Ji (季良俊)
Research Engineer
Corporate Research, UL LLC
333 Pfingsten Road
Northbrook, IL 60062-2096 USA
Phone: +1 847 664 1200
Email: <liang.ji@ul.com>
Web: www.ul.com
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