Solar modules are evaluated in the Renewable Energy Test Center annual PV Module Index.

The Renewable Energy Test Center (RETC) released its 2023 PV Module Index report, evaluating the reliability, quality, and performance of solar panels.

Solar modules are put through a variety of accelerated stress tests to evaluate these parameters. Through comparative test results, project stakeholders can select products best suited for a particular environment, location, or portfolio.

Quality

Hail durability

Top performers: JA Solar, JinkoSolar, Trina Solar

RETC’s hail durability test takes UL and IEC standards testing a step further, exposing solar modules to higher kinetic impact to reflect the risk posed by hail over a 25 or 30 year operating life. In addition to ballistic impact testing, RETC runs thermal cycle and hot-spot tests to reveal potential long-term module degradation.

The top eight 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.) iceball traveling at a terminal velocity of 30.7 m/s (68.7 mph).

Thresher Test

Top performers: Astronergy, JA Solar Longi Solar, Runergy

The thresher test is a summation of a series of tests that places modules under a variety of vigorous environmental stresses to provide quantitative data behind degradation modes. Power drop, leakage current and visual observations are also made in the test.

The RETC test places backsheets, modules, and connectors through accelerated stresses. Thresher tests include humidity-freeze cycling, thermal cycling, damp heat exposure, static and dynamic load testing, and UV soaking. High performers in this category consistently achieved less than 2% of power degradation.

Performance

LeTID resistance

Top performers: Aptos Solar, Astronergy, JA Solar, Runergy, SEG Solar, Silfab Solar, Solar Space, Trina Solar, Yingli Solar

Relatively new cell technologies may experience long-term degradation associated with light exposure and elevated temperatures. This phenomenon, called light- and elevated temperature-induced degradation (LeTID), is tested with a protocol of light soaking, followed by 75 C (167 F) temperature exposure for two 162-hour cycles to identify significant degradation (>5%). Subsequently, test samples are subject to 500 hours of 75 C temperature exposure followed by two additional 162-hour cycles.

Highlighted top performers demonstrated products that less than 0.75% power loss after 486 hours of exposure.

LID resistance

Top performers: Dehui Solar, Longi Solar, Merlin Solar

Light-induced degradation (LID), or power losses from sunlight exposure, affects some PV cell types but not others. PV modules exposed to LID losses rapidly lose performance over the first few hours or days of operation before stabilizing.

RETC notes LID resistance is highly correlated with cell type. Top performers were all monocrystalline silicon panels and experienced an increase in performance or a modest decrease amounting to less than one tenth of one percent.

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 converted to electrical energy, is a well-known and key metric for solar performance. It is highly correlated with cell technology and module design.

The top 14 highest scoring modules scored efficiencies of 20% or more. An N type TOPCon cell scored the highest at 25.8% efficiency, followed by a monocrystalline silicon module with heterojunction technology, recording a 22.4% efficiency.

PAN file

Top performers: Dehui Solar, JA Solar, Longi Solar, Qcells, Runergy, Yingli Solar

The PAN file test is a module characterization test with 22 parameters set by the PVsyst modeling software. Project developers use PVsyst to evaluate potential sites based on energy production and financial performance.

The assuming filed test conditions of a 10 MW utility-scale solar plant in Midland, Texas with fixed tilt ground mounts and 500 kVA central inverters. Top performers in the PAN test achieved a performance ratio in PVsyst of 85% or greater.

Reliability

Damp heat test

Top performers: Astronergy, JA Solar, Longi Solar, Qcells, Runergy, Trina Solar, Yingli Solar

The RETC thresher test includes a damp heat test that exposes modules for 2,000 hours, double the amount required for product certification. The test evaluates a module’s ability to withstand prolonged exposure to humid, high-temperature environments. Taking place inside an environmental chamber, the test exposes modules to a controlled temperature of 85 C (185 F) and a relative humidity of 85% for a set amount of time.

RETC highlighted performers that experienced less than 2% degradation after this exposure.

PID resistance

Top performers: Astronergy, JA Solar, JinkoSolar, Qcells, Runergy

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 with respect to the mounting structure. Typically, exposure times range from 96 hours to as much as 500 hours. PID testing characterizes a module’s ability to withstand degradation due to voltage and current leakage resulting from ion mobility between the semiconductor and other elements in module packaging.

Nearly 28% of the test samples experienced less than 1% degradation over the test period. By comparison, less than 9% of modules achieved greater than 5% power loss.

Static and dynamic mechanical load test

Top performers: Astronergy, JA solar, JinkoSolar, Longi Solar, Runergy, Trina Solar, Yingli Solar

This test exposes modules to 1,000 cycles of +1,000 pascal and –1,000 pascal loads at a frequency of three to seven cycles per minute. Measurements taken after this stress test rate electrical performance.

This year, nearly 47% of the modules that RETC subjected to simulated wind and environmental stresses achieved less than 2% degradation in power. Roughly 17% of the total test samples experienced less than 1% degradation in power after the SDML sequence. RETC notes that the results in this category represent a modest improvement on a year-over-year basis.

Thermal cycling

Top performers: Astronergy, JA Solar, JinkoSolar, Longi Solar, Qcells, Runergy, Saint Gobain, Trina Solar, Yingli Solar

Thermal cycle test calls for cycling modules in an environmental chamber between two temperature extremes—85 C (185 F) on the high end and –40 C (–40F)  on the low end. The RETC test runs 600 cycles, three times as much as the 200 required for certification.

Roughly 80% of modules in this test achieved less than 2% power loss, while only 2.4% had power losses of 4% or more.

Overall top performers

“To identify the best of the best, we reviewed and ranked the overall data distributions across all three disciplines: quality, performance, and reliability. The Overall Results Matrix on the right summarizes the results of this analysis, which highlights eight high achievers based on overall highest achievement in manufacturing,” said RETC.

Top performers (alphabetical order): Astronergy, JA Solar, JinkoSolar, Longi Solar, Qcells, Runergy, Trina Solar, Yingli Solar