Download PV Module Troubleshooting and Measurement

Table of Contents
Abstract........................................................................................................................iv
Acknowledgements .....................................................................................................vi
Glossary ......................................................................................................................vii
1. Introduction .............................................................................................................. 1
1.1 Background .......................................................................................................... 1
1.2 Objective of the Thesis ........................................................................................ 2
1.3 Research Focus .................................................................................................... 2
1.4 Thesis Outline ...................................................................................................... 3
2. Module degradation................................................................................................. 4
2.1 Overview of module degradation......................................................................... 4
2.2 Cell failure ........................................................................................................... 5
2.2.1 Hot spot ........................................................................................................... 5
2.2.1.1 Bypass diodes ................................................................................................ 6
2.2.2 Cracks in cells .................................................................................................. 7
2.3 Packaging material degradation ........................................................................... 8
2.4 Power losses in solar cells.................................................................................... 9
2.4.1 Fundamental losses .......................................................................................... 9
2.4.2 Recombination ............................................................................................... 10
2.4.3 Series Resistance and Shunt Resistance ........................................................... 12
2.4.4 Power loss exceeding the guaranteed level ....................................................... 15
2.4.5 Power loss in different strings ......................................................................... 16
2.5 Module failure .................................................................................................... 18
2.5.1 Dust and Soiling............................................................................................. 18
2.5.2 Shading ......................................................................................................... 19
3. Troubleshooting techniques .................................................................................. 22
3.1 Visual inspection ................................................................................................ 22
3.2 Infrared imaging (IR) ......................................................................................... 22
3.3 Lock in thermography (LIT) .............................................................................. 23
3.4 Electroluminescence (EL) and Photoluminescence (PL) imaging techniques .. 24
3.5 Resonance ultrasonic vibrations (RUV) technique ............................................ 25
4. PV module performance measurements and degradation rate estimation ...... 26
4.1 Background ........................................................................................................ 26
4.2 Description of different PV modules used in the project ................................... 26
4.2.1 Monocrystalline silicon (mc-Si): BP275 & BP585 ............................................ 27
4.2.2 Polycrystalline silicon (p-Si): SX-75 & PW750/70 ........................................... 29
4.3 Major procedures ............................................................................................... 31
4.3.1 Temperature measurement .............................................................................. 31