Categorization of weathering stresses for photovoltaic modules

Abstract

Solar energy conversion requires permanent outdoor operation of essential components such as photovoltaic modules, solar collectors, or reflectors. They are exposed to weathering stresses. The stress levels depend on the local climates. Monitoring of climatic properties and sample properties in different climatic zones (alpine, arid, maritime, moderate, and tropical) during several years provided the base for categorization of these climates. The local climate does not differ very much from year to year in terms of frequency distributions, but big differences are found for different regions or climatic zones. Especially, the solar irradiation is very location‐dependent. The alpine location shows the highest UV irradiation. The UV fraction of the solar irradiation is varying between 2.2% (tropics) and 4.7% (alps). The temperature histograms can be modeled by Gaussian distribution functions. The maritime histogram is very slim and high, showing the cooling by the sea and the wind. Several approaches for a categorization of these local climates can be applied: Mean temperatures, effective temperatures, or the corresponding constant testing time for fictive degradation processes with arbitrary activation energy. The categorization of the relative humidity revealed humid climates in the alpine and the tropical test site, when considering the time of wetness (rh > 80%). Obviously, the humidity stress or the corrosivity would be very different at those sites. Therefore, a more holistic approach considering more stress factors simultaneously would be more appropriate for the categorization. The interaction between the samples and the climate creates the so‐called micro‐climate which is the real stress on the samples, such as surface temperature, daily temperature cycles, surface humidity, or temperature‐enhanced photo‐degradation. The conditions for accelerated life testing (ALT) modeled on the base of monitored climatic data and sample temperatures are different for the different locations. They offer another possibility for categorization of the climatic stresses and the option for designing climate‐adapted components.

Photovoltaic Power Forecasting Methods

“…The three commonly used temperature models presented in (Eqs. (8), ( 9) & ( 10 [15,18] with small modifications to minimize the uncertainty.…”

“…It should be noted that, although the Kings model showed good predictions based on this example, it is not enough to guarantee that this will always be the case when the model is applied on different dataset. This is because the accuracy of the temperature models has been found to be influenced by; geographical locations, model design and mounting conditions [18].…”

“…T amb 0 C ½ is ambient temperature, GW =m 2 ½ is the incident solar irradiance on the module, and WS m=s ½ is the wind speed. U 0 W= 0 Cm 2 hi and U 1 Ws= 0 Cm 2 hi are the coefficients describing the effect of the radiation on the module temperature and the cooling by the wind, [18] respectively. a and b are parameters that depend on the module construction, materials and on the mounting configuration of the module [15].…”

Analysis on the Features of NOCT and NMOT Tests With Photovoltaic Module

“…At NMOT, the PV module junction temperature is a function correlated with the ambient temperature ( ) and the irradiance ( ) and the wind speed ( ) of an operating PV module. Being independent of the ambient temperature, the difference between the ambient temperature and module temperature ( − ) can be expressed as a function + • = /( − ) of the wind speed based on it being proportional to the irradiance level above 400 W/㎡ [7], [11]- [14].…”

Global Climate Data Processing and Mapping of Degradation Mechanisms and Degradation Rates of PV Modules

“…The definition of each letter is as follows: Hydrolysis-degradation presents the smallest contribution in almost all the KGPV zones, but is considerably higher for the tropical climates (AH and AK), which zones are related to high precipitation levels (humid areas) and temperature levels. This process can provoke moisture ingress leading to delamination of polymers or corrosion of solder bonds [31].…”