Reliability of PV Modules Research Papers (original) (raw)

Encapsulant discoloration is a common type of degradation in photovoltaic (PV) modules, which significantly affects its performance and reliability under field conditions. This paper presents the non-destructive characterization... more

Encapsulant discoloration is a common type of degradation in photovoltaic (PV) modules, which significantly affects its performance and reliability under field conditions. This paper presents the non-destructive characterization techniques for investigation of encapsulant discoloration in crystalline-silicon PV modules. These characterization techniques have been channelized and applied to investigate various aspects of discoloration effects on 20 years old field-exposed PV modules. Dark lock-in ther-mography (DLIT) has been exploited for investigation of temperature variation and defects caused by uneven discoloration over the cells, while electroluminescence (EL) imaging has been proposed for relative quantification of extent of discoloration in a PV module. The spatially-resolved images obtained from both the techniques provided the qualitative and quantitative information about the optical and electrical effects of discoloration in a module, which is not possible by the conventional visual inspection method alone. The electrical methods including proposed differential current analysis, I–V measurement and insulation resistance test have also been used to aid this investigation. The results obtained from these techniques show that the power degradation due to discoloration was attributed to significant reduction in fill factor by non-uniform discoloration and increase in series resistance of cell contacts, and to some extent by its direct effect of light reduction. Electrical mismatch appeared to play an important role in accelerating the encapsulant discoloration in the module. These nondestructive characterization approaches can enable to inspect large number of PV modules in their actual encapsulated form by fast and efficient manner.

This work has been undertaken to examine the warranties offered by the PV module manufacturers for degradation after long term field operation under Thailand weather conditions. Samples from the four lots of PV modules comprising on mono... more

This work has been undertaken to examine the warranties offered by the PV module manufacturers for degradation after long term field operation under Thailand weather conditions. Samples from the four lots of PV modules comprising on mono crystalline, poly crystalline and amorphous silicon, with different duration of field operation ranging from 9 to 14 years were tested for I-V curve characteristics under field conditions and measured values were corrected to Standard Test Conditions (STC) values by using correction procedure inscribed in IEC 60891 standard. The corrected values of output power and other parameters were compared with nameplate data for calculation of degradation during the period of operation. The actual degradation in output power for two lots of mono and one lot of poly crystalline silicon was found remarkably high (3.9, 3.0 & 2%/year) when compared with the warrantees (0.8-1%/year generally). However, interestingly the lot comprising on thin film amorphous-Si modules showed higher values of output power than nameplate. There were no visible defects in the modules except yellowing and discoloring. The enhanced degradation rates can be attributed to the quality of modules along with the effects of harsh field weather conditions.

—This paper, Part II, deals with the software platform that implements the workflow described in Part I, i.e., a thermography-based diagnostics able to provide a detailed, clear, and unambiguous information on the health state of... more

—This paper, Part II, deals with the software platform that implements the workflow described in Part I, i.e., a thermography-based diagnostics able to provide a detailed, clear, and unambiguous information on the health state of photovoltaic (PV) modules. The methodology, in fact, allows a numerical and qualitative evaluation of each cell of the PV module. In particular , this paper deeply describes the main features of the software platform and introduces the graphical user interface that makes the framework efficiently and effectively adoptable since it leads to the automatic generation of a report. In order to show the mani-fold features, three cases of study, which have been derived from a real monitoring survey, are discussed, highlighting the critical situations revealed neither with a direct observation of the infrared image nor with its manual processing: The first case in regard to a defected PV module and the second one an almost completely uniform module, while the third one deals with a dishomogeneous module.

—Although recent laboratory tests are showing promising progresses in the materials and production technologies of pho-tovoltaic (PV) devices, the commercial PV modules do not show analogous impressive improvements. Therefore, a... more

—Although recent laboratory tests are showing promising progresses in the materials and production technologies of pho-tovoltaic (PV) devices, the commercial PV modules do not show analogous impressive improvements. Therefore, a diagnostic approach , able to check the current state of health of already installed PV systems, as well as their trend of ageing, assumes a strategic importance. In this scenario, we introduce a thermography-based diagnostics able to provide a detailed, clear, and unambiguous information , thanks to a computer-aided investigation that is much deeper than the today available infrared analysis. The proposed approach allows a numerical and qualitative evaluation of each cell of the PV device. This Part I—Framework introduces the methodology , based on two main analyses. The first one (cell analysis) studies each single cell, while the second one (cluster analysis) fo-cuses the attention on groups of PV cells. The framework is also characterized by a preprocessing in which the region of interest is extracted from the infrared image in order to focus the successive processing and analyses only on this area. The Part II—Platform and Results shows the cloud platform implementing the workflow (it automatically generates a comprehensive and detailed report), and discusses also several significant cases of study.

This study evaluates the frameless modules of same type (model B) in two 16-year old photovoltaic power (PV) systems to ascertain degradation rates, reliability failure modes and safety failure modes which occur in a hot-dry climate. Each... more

This study evaluates the frameless modules of same type (model B) in two 16-year old photovoltaic power (PV) systems to ascertain degradation rates, reliability failure modes and safety failure modes which occur in a hot-dry climate. Each system is composed of 1512 modules. The average degradation rate is determined to be 0.85%/year for the best modules and 1.1%/year for all the modules (excluding the safety failed modules). Primary safety failure mode is the backsheet delamination though it is small (less than 1.7%). Primary degradation mode and reliability failure mode may potentially be attributed to encapsulant browning leading to transmittance/current loss and thermo-mechanical solder bond fatigue (cell-ribbon and ribbon-ribbon) leading to series resistance increase. Under the typical 20/20 warranty terms, 0.5-1.7% of the modules qualify for the safety returns, 73-76% of the modules qualify for the warranty claims and 24-26% of the modules are meeting the warranty terms.