1. LONGTERM EXPERIENCE
WITH PV POWER PLANTS IN GERMANY
Dr. Christian Reise
Fraunhofer Institute for
Solar Energy Systems ISE
Freiburg, Germany
Solar Operations & Maintenance
Milan, October 9th, 2013
© Fraunhofer ISE

2. The Fraunhofer ISE Quality Circle
Yield Assessments
Quality
Monitoring
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Module
Measurements
System tests

3. What are the questions?
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4. What are the questions?
 What is the state-of-the-art performance of a PV power plant?
 What about degradation?
 What affects system reliability?
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5. What are the questions?
 What is the state-of-the-art performance of a PV power plant?
A review of 20+ years of commercial PV systems in Germany
 What about degradation?
A study on 100+ power plants in Germany
 What affects system reliability?
Modules / inverters / operation management…
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6. PV support schemes in Germany
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7. Development of system Performance Ratio in Germany
A typical
5 kWp
system
installed
in 1993
within the
German
1000 Roofs
Programme
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8. Performance Ratio (PR): A simple Definition
PR =
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9. Development of system Performance Ratio in Germany
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10. Development of system Performance Ratio in Germany
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11. Development of system Performance Ratio in Germany
Where is the limit?
 In Germany, state-of-the-art PV systems reach PR(si) values around 90%
 Note the difference of some 3…4% between PR(si) and PR(pyr)
 In southern Europe, PR will be reduced by 3…5%
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12. Development of system Performance Ratio in Germany
Where is the limit?
 In Germany, state-of-the-art PV systems reach PR(si) values around 90%
 Note the difference of some 3…4% between PR(si) and PR(pyr)
 In southern Europe, PR will be reduced by 3…5%
PR =
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13. Important factors for successful projects
Lessons learnt
 Modules show rated power
 Maintenance of area
 Theft protection
 Minimized row to row shading
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14. Important factors for successful projects
Lessons learnt
 Modules show rated power
 Maintenance of area
 Theft protection
 Minimized row to row shading
 Minimized local shading
 Durable installation
 QC with commissioning
 Regular cleaning intervals
 Monitoring of operation
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15. What are the questions?
 What is the state-of-the-art performance of a PV power plant?
A review of 20+ years of commercial PV systems in Germany
 What about degradation?
A study on 100+ power plants in Germany
 What affects system reliability?
Modules / inverters / operation management…
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16. A study on 100+ power plants in Germany
Data Handling
Filtering of 5-min average values:
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17. A study on 100+ power plants in Germany
Data Handling
Filtering of 5-min average values:
 Irradiance between
800…1000 W/m²
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18. A study on 100+ power plants in Germany
Data Handling
Filtering of 5-min average values:
 Irradiance between
800…1000 W/m²
 Module temperature between
40…45 °C
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19. A study on 100+ power plants in Germany
Data Handling
Filtering of 5-min average values:
 Irradiance between
800…1000 W/m²
 Module temperature between
40…45 °C
 Values inside median ± 5%
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© Fraunhofer ISE

20. A study on 100+ power plants in Germany
Data Handling
Filtering of 5-min average values:
 Irradiance between
800…1000 W/m²
 Module temperature between
40…45 °C
 Values inside median ± 5%
 Calculation of rate of change
rate in %/year
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21. A study on 100+ power plants in Germany
Example: a German „1000-Roofs-Programme“ system
5 kWp PV system built in 1993
New monitoring equipment in 2001
outliers excluded
fitted linear slope
Rate of Change: ca. –0.3%/a
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22. A study on 100+ power plants in Germany
Results statistics for c-Si
 Calculation of a rate of
change per year for each
PV system shows large
scatter
rate of change in % per year
 Average c-Si degradation
rates are around –0.25%
per year
2.0%
4.0%
mono/poly
3.0%
1.0%
0.0%
-1.0%
-2.0%
-3.0%
-4.0%
1
2
3
4
5
6
7
8
9 10 11_
years of operation
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23. A study on 100+ power plants in Germany
Results for alternative silicon wafer technologies
 Average c-Si degradation
rates are around –0.25%
per year
 Systems with EFG or
string-ribbon modules
reveal a tendency towards
larger negative rates of
change
rate of change in % per year
4.0%
mono/poly
3.0%
EFG/String Ribbon
2.0%
1.0%
0.0%
-1.0%
-2.0%
-3.0%
-4.0%
1
2
3
4
5
6
7
8
9 10 11_
years of operation
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© Fraunhofer ISE

24. What are the questions?
 What is the state-of-the-art performance of a PV power plant?
A review of 20+ years of commercial PV systems in Germany
 What about degradation?
A study on 100+ power plants in Germany
 What affects system reliability?
Modules / inverters / operation management…
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25. What affects system reliability?
On average, there
are 5 incidents per
PV power plant and
year
Source:
meteocontrol,
Augsburg,
Germany
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26. What affects system reliability?
 Module reliability
 BOS component & installation reliability
 Operation management
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27. What affects system reliability?
 Module reliability
“no problem”
 BOS component & installation reliability
Commissioning tests
 Operation management
Monitoring & intervention concepts
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28. Commissioning tests
Detailed on-site analysis of the
entire power plant:
 Comprehensive visual
inspection
 Thermographic imaging
 Measurement of actual PV
power and conversion to
Standard Test Conditions
 Assessment of Performance
Ratio (PR)
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29. System Inspection and Testing
 Verification of design data (module types, tilt angles, distances)
 Screening for large and small anomalies (insufficient foundation,
cell grid faults)
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30. System Inspection and Testing
Mechanical problems
 Faulty mounting of modules
 Missing protection leading to cable damage
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31. System Inspection and Testing
Mechanical problems
 Loose connectors
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32. System Inspection and Testing
Mechanical problems
 Combination of connectors from
different manufacturers
 Loose cables
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33. System Inspection and Testing
Mechanical problems
 Cable glands on top, moisture in the sub-distribution box
 Spare cable glands not sealed, moisture and animals in the box
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34. System Inspection and Testing
Infrared imaging
Mobile lifting platform used
for infrared camera imaging
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Temperature analysis of a
large module field
Temperature analysis of a
solar module with defective
cells

35. System Inspection and Testing
Infrared imaging
 Detection of defective bypass diodes
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36. System Inspection and Testing
Infrared imaging
 Detection of defective terminals with high transition resistance
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37. System Inspection and Testing
Infrared imaging
 Detection of weak connections on power rails
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38. Commissioning tests
Detailed on-site analysis of the
entire power plant:
 Comprehensive visual
inspection
 Thermographic imaging
 Measurement of actual PV
power and conversion to
Standard Test Conditions
 Assessment of Performance
Ratio (PR)
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© Fraunhofer ISE

39. What affects system reliability?
 Module reliability
“no problem”
 BOS component & installation reliability
Commissioning tests
 Operation management
Monitoring & intervention concepts
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40. Operation management
Monitoring & intervention
 Operation of a state-of-the-art supervisory control and data acquisition
(SCADA) system in each PV power plant
 Operation of a dedicated control centre, offering all features needed to
evaluate system operation and to optimize maintenance work flow
 Rapid reaction to error messages
 Management, performing and documentation of maintenance and repair
 On-site visits in regular intervals
 Landscape maintenance
Learn more about operation management at this event…
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41. Conclusions…
 PV power plant operation is well understood and reproducible
 Today’s systems may reach PR(si) values around 90% in Central Europe
 Mono- and polycrystalline silicon systems show small degradation rates, by
default, Fraunhofer ISE assumes –0.25% per year
 Long term success starts with a comprehensive system testing
 Only professional O&M concepts ensure high performance and yields
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42. Thank you for your attention!
Fraunhofer Institute for Solar Energy Systems ISE
Dr. Christian Reise
christian.reise@ise.fraunhofer.de
www.ise.fraunhofer.de
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43. Development of system Performance Ratio in Germany
Comparison prediction vs. real world system operation
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44. Development of system Performance Ratio in Germany
Comparison prediction vs. real world system operation
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