New research from the University of New South Wales shows that the degradation of PV modules varies widely depending on system design and location, influenced by UV exposure, temperature, humidity and atmospheric conditions. Tropical and desert regions face the highest stresses, highlighting the need for climate-specific testing and system design.
Utraviolet (UV) radiation has long been recognized as a major cause of PV module degradation. However, this factor is significantly underestimated in current testing standards, especially for modern system designs and areas of high irradiation.
With this in mind, a group of researchers from the University of New South Wales (UNSW) in Australia have developed a highly accurate global UV radiation model on tilted surfaces, capturing the impact of system design, climate and atmospheric conditions.
“Our new model shows that identical module technologies degrade differently depending on the location of deployment, highlighting the need for climate-specific reliability assessment,” said corresponding author Bram Hoex. pv magazine. “It also provides a way to move beyond generic accelerated testing to regionally relevant degradation modeling and qualification protocols.”
The researchers highlighted that global UV radiation can range from less than 30 W/m² in high latitude areas to more than 80 W/m² in deserts and arid climates. In some locations, the UV dose specified in the IEC 61215 standard, which is only 15 kWh/m², can be achieved in less than two months. In contrast, real-world exposure over the lifetime of a module is an order of magnitude higher.
“Current testing thresholds are simply too low to replicate long-term field conditions,” the authors noted, adding that even improved protocols fall short in simulating 25 to 30 years of operation.
One of the most striking findings of the study concerns system design. The researchers compared fixed-tilt installations with single-axis tracking (SAT) systems and found that trackers receive significantly more UV radiation due to their orientation to the sun during the day.
In high-radiation areas such as deserts, single-axis tracking (SAT) systems can be exposed to up to 1.5 times more UV radiation than fixed-tilt systems, leading to degradation rates that are almost twice as high. This results in annual UV-driven degradation rates of up to 0.35% per year for SAT systems, compared to approximately 0.25% per year for fixed-tilt installations.
Over the average life of a project, this difference can add up to several percentage points of additional power loss, which has a direct impact on the economics and long-term performance of the PV system.
The study also found that identical PV modules can degrade at markedly different rates depending on their installation location. The main factors driving this variability include UV radiation, temperature, humidity and atmospheric conditions such as ozone levels, aerosols and cloud cover. Some of the most challenging environments include tropical and desert regions, where high UV exposure combines with intense thermal and environmental stress, accelerating module degradation.
“Current standards significantly underestimate real-world UV exposure, in some cases by orders of magnitude relative to living conditions,” Hoex pointed out. “UV exposure varies significantly depending on location and system configuration, with tracking systems experiencing up to approximately two times higher degradation rates in high-radiation areas. In arid and tropical climates, UV-induced degradation can reach approximately 0.25-0.35% per year, contributing substantially to long-term performance loss.”
The new, highly accurate model to estimate UV radiation in PV systems was presented in the article ‘Closing the UV-Induced Photodegradation Gap Through Global Scale Modeling of Fixed Tilt and Tracking Photovoltaic Systems’, published in the journal IEEE Journal of Photovoltaics.
“This work is part of our group’s broader efforts to connect fundamental degradation mechanisms to system-level effects in the field, by combining targeted accelerated testing – such as UV, moist heat and contamination – with physics-based and data-driven modeling at the system scale to quantify how both established and emerging failure modes translate into real-world energy yield losses in different climates and system designs,” Hoex concluded.
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