- Title
- Investigation of potential induced degradation as a performance limiting defect in photovoltaic modules
- Creator
- Kwembur, Isaac Morko
- Subject
- Photovoltaic cells
- Date Issued
- 2020
- Date
- 2020
- Type
- Thesis
- Type
- Doctoral
- Type
- PhD
- Identifier
- http://hdl.handle.net/10948/48423
- Identifier
- vital:40875
- Description
- Potential Induced Degradation (PID) impacts negatively on photovoltaic (PV) module durability because it significantly affects the output of PV modules and systems. Unless detected at infancy, PID progression can be catastrophic. This study involved systematic PID stressing of PV modules using a custom-built environmental chamber that can achieve suitable environmental conditions, viz., of the 35 °C ± 1 °C and relative humidity of 75 % ± 5 %. The first part of this work was to induce PID using three approaches: climate chamber testing, inducing PID using a conductive aluminium plate on the surface of the module without touching the frame and a localised PID induction on one cell in a module. The second part is to detect induced PID using Electroluminescence (EL) images taken at current corresponding to 10% Isc, EL histograms analysis and Voc ratio taken at 1000 W/m2 to 200 W/m2 . The third part is to study module regeneration after PID shunting degradation in two ways, viz., forced reverse polarization and natural recovery. The PID detection tools used in this work are well known module characterization techniques such as EL imaging, Infrared imaging, and light and dark current-voltage measurements. These characterisation tools are used in combination to detect defects such as optical losses, cracks, breakage, electric circuit degradation and PID. Under normal testing PID was detected and in some cases, modules were able to recover, while for advanced stage PID regeneration or PID reversal was difficult. This thesis focuses on PID detection at infancy using three approaches; EL imaging at current corresponding to 10% of Isc. Light and dark current – voltage measurements (L-IV & D-IV) and open circuit voltage (Voc) ratios at low irradiance. The early detection procedures are essential in reversing the degradation caused by PID which is reversible. The time taken to reverse the PID degradation will depend on the extent of the degradation. If detected early, it will take a short period of time to completely reverse lost power. Infrared thermography is a non-contact characteristic tool that can be deployed in large scale plants using drones to detect the presence of PID in PV plants. Module performance and device parameters extracted from the L-IV curves on a module before and after PID stress, such as Pmpp, Voc, Isc Fill Factor (FF), shunt resistance (Rsh) and series resistance (Rs) and ideality (n) are sensitive to PID shunting. Voc and Rsh drop significantly with the onset of PID, while Rs increases. The decrease in Voc and Rsh is due to heavy shunting on the module resulting in increased carrier recombination, while the increase in Rs is due to increased shunting paths leading to decreased photocurrent. When substantial degradation on a module occurs Pmpp, FF and n will drop and at very advanced stage of PID degradation Isc may drop excessively.
- Format
- Xiv, 122 leaves
- Format
- Publisher
- Nelson Mandela University
- Publisher
- Faculty of Science
- Language
- English
- Rights
- Nelson Mandela University
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Collections
NMU School of Computer Science, Mathematics, Physics and Statistics
| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | SOURCE1 | Kwembur, IM 215379446 Thesis April 2020.pdf | 4 MB | Adobe Acrobat PDF | View Details Download |