Photovoltaic failure and degradation modes

Abstract

The extensive photovoltaic field reliability literature was analyzed and reviewed. Future work is prioritized based upon information assembled from recent installations, and inconsistencies in degradation mode identification are discussed to help guide future publication on this subject. Reported failure rates of photovoltaic modules fall mostly in the range of other consumer products; however, the long expected useful life of modules may not allow for direct comparison. In general, degradation percentages are reported to decrease appreciably in newer installations that are deployed after the year 2000. However, these trends may be convoluted with varying manufacturing and installation quality world-wide. Modules in hot and humid climates show considerably higher degradation modes than those in desert and moderate climates, which warrants further investigation. Delamination and diode/j-box issues are also more frequent in hot and humid climates than in other climates. The highest concerns of systems installed in the last 10 years appear to be hot spots followed by internal circuitry discoloration. Encapsulant discoloration was the most common degradation mode, particularly in older systems. In newer systems, encapsulant discoloration appears in hotter climates, but to a lesser degree. Thin-film degradation modes are dominated by glass breakage and absorber corrosion, although the breadth of information for thin-film modules is much smaller than for x-Si.

Quantifying and modeling the impact of interconnection failures on the electrical performance of crystalline silicon photovoltaic modules

“…They lead to a reduction in the module's performance by an increase in the series resistance, which is often observed in field modules (see, eg, previous studies). An extensive survey of PV field reliability of 2017 identifies some failures related to the electric interconnections, such as ribbons and metallization discoloration caused by corrosion and hot spots, as the highest concerns for PV systems installed in the past 10 years.…”

“…In addition to thermomechanical fatigue, the presence of moisture or acids in the encapsulant, such as the acetic acid generated by the photothermal degradation of the ethylene‐vinyl acetate (EVA) typically used as the encapsulation material, can corrode the metallic interconnections, ie, the copper core and the tin coating of the ribbons, as well as the solder bonds and the cell fingers (see, eg, other works). Internal circuitry discoloration due to corrosion is an issue in particular in hot‐humid climates, where it was found to cause significant reduction in the fill factor.…”

Influence of Viscoelastic Properties of Encapsulation Materials on the Thermomechanical Behavior of Photovoltaic Modules

“…The number of elements required is dependent on the complexity of the material. The model may be expressed mathematically as (1).…”

“…Solder bond degradation is amongst the most dominant failure mechanisms for performance degradation and failure, particularly in hotter climates [1] and can be attributed to the thermomechanical stresses and strains generated during operation. The rate of degradation is known to be dependent on the specific use-environment, module design and material selection [2].…”

Effect of viscoelasticity of ethylene vinyl acetate encapsulants on photovoltaic module solder joint degradation due to thermomechanical fatigue

“…[12][13][14][15][16][17] PV module solder joint failure is a common failure mechanism that is widely observed in the field. [18][19][20][21][22][23][24] The rate of solder fatiguing in different environments is not fully understood as it depends on a variety of factors, such as thermomechanical properties of the various materials in a PV module as well as the detailed stress levels and the material response to these particular stress levels. [25][26][27][28] Typical PV modules are a multi-layer system of materials consisting of a front glass sheet, a polymeric backsheet, and two layers of polymeric materials in which interconnected solar cells and electrical circuitry are encapsulated.…”