The Renewable Energy Test Center (RETC) has released its report Index of PV modules 2024 report evaluating the reliability, quality and performance of solar panels.
Solar panels are subjected to various accelerated stress tests to evaluate these parameters. Comparative test results allow project stakeholders to select products that are best suited for a particular environment, location or portfolio.
To identify the best of the best, RETC assessed and ranked the overall data distribution across three disciplines: quality, performance and reliability. At the end of this report you will find the overall top performers.
Reliability
Back cover ultraviolet durability
Top performers: JA Solar, Longi Solar, SolarSpace
Backsheet ultraviolet durability (BUDT) includes a durability test suite to examine glass-on-backsheet PV module designs for vulnerabilities to UV exposure and to prevent backsheet-related failures. This BUDT sequence begins with 1000 hours of exposure to moist heat to weaken polymeric bonds.
Featured top performers experience no cracks in the backplate during the test.
Damp heat test
Top performers: Astronergy, ES Foundry, Longi Solar, Runergy and Trina Solar
The RETC thresher test involves a moist heat test where modules are exposed for 2000 hours, double the amount required for product certification. The test evaluates a module’s ability to withstand prolonged exposure to humid, high-temperature environments. The test takes place in a climate chamber and exposes the modules to a controlled temperature of 85 C (185 F) and a relative humidity of 85% for a certain period of time.
RETC highlighted artists who experienced less than 2% degradation after this exposure.
Hail durability
Top performers: JA Solar, Longi Solar
RETC’s hail durability test takes UL and IEC standards one step further, exposing solar panels to higher kinetic impacts to reflect the risk of hail over a 25 or 30 year lifespan. In addition to ballistic impact testing, RETC conducts thermal cycling and hotspot testing to reveal potential long-term module degradation.
The top performers in this category withstood an effective kinetic energy of 20 Joules or more. These modules effectively demonstrated resistance to a 45 mm (1.8 in) ice ball traveling at a terminal velocity of 30.7 m/s (68.7 mph).
Potential Induced Degradation (PID)
Top performers: Astronergy, ES Foundry, GEP VN, Gstar, JA Solar, Longi Solar, Qcells, REC Solar, Runergy, SEG Solar, Silfab Solar, SolarSpace, Talesun, Trina Solar, VSUN Solar and Yingli Solar
Potential Induced Degradation (PID) resistance tests rack-mounted modules in an environmental chamber, which controls temperature and humidity and exposes them to a voltage bias of several hundred volts relative to the mounting structure for 192 hours (PID192 exposure). PID testing characterizes a module’s ability to resist degradation due to voltage and current leakages due to ion mobility between the semiconductor and other elements in the module package.
RETC required PV module models to withstand PID192 exposure with a maximum power decrease of less than 2%. At the other end of the spectrum, it considered a maximum power degradation greater than or equal to 5% as a red flag.
Static and dynamic mechanical load test
Top performers: Aptos Solar, Astronergy, ES Foundry, Gstar, JA Solar, Longi Solar, Runergy, Silfab Solar, SolarSpace, Trina Solar and Yingli Solar
In this test, modules are exposed to 1,000 cycles of +1,000 Pascal and –1,000 Pascal loads at a frequency of three to seven cycles per minute. After this stress test, the electrical performance was measured.
This year, RETC required PV module models to withstand SDML exposure with less than 2.5% degradation of maximum power. It considered a maximum power degradation greater than or equal to 5% as an alarm signal. In this testing category, it notes that 68% of samples qualified as high performers, while 7% returned a red flag result.
Thermal cycling
Top performers: Aptos Solar, Astronergy, ES Foundry, Gstar, JA Solar, Longi Solar, Qcells, Runergy, SolarSpace, Trina Solar and Yingli Solar
The thermal cycling test requires cycling modules in an environmental chamber between two extreme temperatures: 85 C (185 F) on the high side and –40 C (–40 F) on the low side. The RETC test involves 600 cycles, three times the 200 required for certification.
Approximately 67% of the modules in this test achieved high performance status with less than 2% power loss, while 9% of brands tested experienced a power loss of 5% or more.
Ultraviolet Induced Degradation (UVID)
Top performers: Trina Solar and VSUN Solar
UVID testing characterizes a PV panel’s ability to resist ultraviolet-induced degradation. This optional test suite exposes test samples to 220 kWh/m2 UV exposure (UV220), almost 15 times the UV exposure required for product certification.
Top performers can withstand UV220 exposure with a reduction in maximum power of less than 2%. Red flag modules that deteriorated more than 5% represented 40% of brands tested.
“Alarmingly, we have observed double-digit power losses in some mass-produced, commercially available PV modules, indicating that these products could degrade by 10% to 16% in the first three years of field use,” according to RETC.
Performance
Module efficiency
Top performers: Astronergy, Mission Solar, Qcells, REC Solar and Silfab Solar
Module conversion efficiency is determined by dividing the maximum power on a product’s nameplate under standard test conditions by the total opening area.
RETC has recognized manufacturers of PV module models with a conversion efficiency of more than 21% as high performers in the test category. About 56% of the modules tested were listed as ‘high performers’.
Angle of attack modifier
Top performers: Dehui Solar, ES Foundry, JA Solar, JinkoSolar, Longi Solar, Meyer Burger, Qcells, Runergy, Silfab Solar and SolarSpace
Incidence Angle Modifier (IAM) is a performance characteristic that accounts for changes in PV module output based on changing sun angles relative to the plane of the array. To characterize IAM, RETC conducts electrical characterization tests at different angles ranging from 0° to 90°.
Manufacturers of PV module models with an IAM of more than 88% at an angle of incidence of 70° were cited as high performers in the test category.
LeTID resistance
Top performers: Astronergy, Gstar, JinkoSolar, Longi Solar, Runergy, SEG Solar, Silfab Solar, SolarSpace, Talesun, Trina Solar, VSUN Solar, Waaree, Yingli Solar
Relatively new cell technologies can degrade in the long term due to exposure to light and elevated temperatures. This phenomenon, called light- and elevated temperature-induced degradation (LeTID), is tested with a protocol of light soaking, followed by exposure to a temperature of 75 C (167 F) for two 162-hour cycles to detect significant degradation (>5% ) to identify. . The test samples are then subjected to 500 hours of exposure at a temperature of 75°C, followed by two more cycles of 162 hours.
Featured top performers demonstrated products with less than 0.5% power loss after 486 hours of exposure.
LID resistance
Top performers: Astronergy, GEP VN, Gstar, JA Solar, JinkoSolar, Longi Solar, Meyer Burger, Qcells, Runergy, SEG Solar, Silfab Solar, SolarSpace, Talesun, Trina Solar, VSUN Solar, Waaree and Yingli Solar
Light-induced degradation (LID), or power loss due to exposure to sunlight, affects some types of PV cells but not others. PV modules exposed to LID losses rapidly lose performance during the first few hours or days of use before stabilizing. RETC notes that LID resistance is strongly correlated with cell type.
RETC required PV module models to withstand the LID range with less than or equal to 0.5% maximum power degradation.
Module efficiency
Top Performers: Auxin Solar, JA Solar, Longi Solar, Meyer Burger, Mission Solar, Qcells, REC Solar, Silfab Solar, Trina Solar, Yingli Solar
Module efficiency, or the percentage of incident solar energy that is converted into electrical energy, is a well-known and important measure of solar energy performance. It is highly correlated with cell technology and module design.
The top 14 highest scoring modules achieved an efficiency of 20% or more. An n-type TOPCon cell scored the highest with an efficiency of 25.8%, followed by a monocrystalline silicon module with heterojunction technology, which registered an efficiency of 22.4%.
PAN file
Top performers: Astronergy, Gstar, JinkoSolar, Longi Solar, Qcells, Runergy, SolarSpace, Trina Solar, VSUN Solar and Yingli Solar
PAN files are text-only software files that characterize the performance parameters of PV modules in accordance with IEC 61853-1. RETC uses state-of-the-art equipment under controlled conditions to generate third-party PAN files, which provide an independent and affordable characterization of PV module performance.
“These small files do a lot of work in the context of the PV performance modeling used to inform project bankability assessments,” RETC said. “Once imported into industry-standard software, such as PVsyst, these independently verified module-specific performance parameters provide accurate and affordable energy production estimates.”
The assumption provided test conditions of a 10 MW utility-scale solar power plant in Midland, Texas, with fixed tilting ground supports and 500 kVA central inverters. Top performers in the PAN test achieved a performance ratio in PVsyst of 85% or more.
Temperature coefficient
Top performers: Astronergy, JinkoSolar, Meyer Burger, Qcells, REC Solar, Runergy and Silfab Solar
This performance characteristic takes into account changes in the maximum power, current and voltage of the PV module based on changing cell temperature conditions. Specifically, the temperature coefficient describes the percentage change in power for each degree Celsius (%/°C) compared to standard test conditions (25°C).
Modules with temperature coefficient values less than 0.3%/°C (absolute) were listed as good performers in the test category.
Generally the highest achievers
“When analyzing our annual PV module test results, 8% of tested models met RETC’s stringent standard for our top award – being recognized as ‘Overall Highest Performer’ – while 14% of tested models showed some sort of red flag ,” said RETC .
Top performers (alphabetical order): Astronergy, ES Foundry, Gstar, JA Solar, Longi Solar, Runergy, SolarSpace, Trina Solar and Yingli Solar
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