Natural exposure testing and annual power degradation rate evaluation for photovoltaic（PV） modules Part 4: Extreme cold environment
1Key Takeaways
This document specifies the terminology and definitions, exposure site and test apparatus, test specimens, test procedures, inspection and maintenance, test results, performance evaluation of annual power attenuation rate, and test report requirements for natural outdoor exposure tests of photovoltaic modules in extrem…
2Expert Interpretation
This article provides a detailed interpretation of the SJ/T 11828.4-2026 standard, covering natural exposure testing methods for photovoltaic modules in extreme cold atmospheric environments, annual power degradation rate evaluation, equipment requirements, and performance grading, providing a scientific basis for assessment in the photovoltaic industry.
Standard Background and Scope of Application
SJ/T 11828.4-2026 "Photovoltaic Module Natural Exposure Testing and Annual Degradation Rate Evaluation - Part 4: Extreme Cold Atmospheric Environment" is a Chinese electronic industry standard, primarily targeting outdoor natural exposure testing of ground-mounted crystalline silicon photovoltaic modules in extreme cold climates. The characteristics of extreme cold environments include low temperatures (down to -40°C), heavy snow, hail, strong winds, and other extreme weather conditions, posing severe challenges to the material, electrical, and mechanical performance of photovoltaic modules. This standard measures module power degradation, power generation, and energy efficiency ratio through year-long outdoor exposure, and grades products based on the first-year degradation rate (A+, A, B, C levels), providing a basis for product selection and quality assessment.
Test Site and Equipment Requirements
The standard imposes strict requirements on exposure test sites: they must be located in extreme cold climate zones, with flat ground free of tall vegetation, open surroundings without obstructions, and far from industrial pollution sources. Test setups include support systems (fixed or tracking), grid-connected inverters (string or micro-inverters), and various monitoring devices.
Key monitoring equipment is listed in the table below:
| Equipment Name | Key Parameter Requirements |
|---|---|
| Pyranometer | Front side Class A (uncertainty ≤±2% @1000W/m²), back side Class C (≤±3%) |
| Ambient Temperature Sensor | Resolution ≤0.1°C, uncertainty ≤1°C |
| Anemometer | Measurable range 0.25m/s, uncertainty ≤0.5m/s when ≤5m/s |
| DC Energy Meter | Accuracy class 1 or higher |
| I-V Characteristic Measurement Device | Compliant with IEC 60904-1:2020 |
All monitoring devices require regular calibration (pyranometers every 12 months, others every 24 months) and must be equipped with heating modules to ensure normal operation at low temperatures.
Specimens and Test Procedures
Specimens shall be same-batch products explicitly certified as qualified by the manufacturer, including inspection samples, control samples, and spare samples. The number of inspection samples must match the inverters, with at least two single-module specimens. During installation, string inspection samples are fixed at the optimal tilt angle, while single-module specimens are preferably installed on tracking supports.
The test consists of stability testing, initial testing, natural exposure monitoring, and final testing. Initial testing includes visual inspection, Electroluminescence (EL), performance under Standard Test Conditions (STC), insulation, and wet leakage current tests. During exposure, single modules are monitored via automatic I-V testing devices or micro-inverter power generation monitoring, while strings are monitored via DC energy meters to record power generation. Final testing repeats the initial test items.
Evaluation Indicators and Grading
Core evaluation indicators include:
- Annual Power Degradation Rate: Percentage of power degradation in the first year, graded separately for P-type and N-type crystalline silicon modules.
- Annual Power Generation: Total DC power generation for single modules and strings.
- Annual Energy Efficiency Ratio: Ratio of actual power generation to theoretical power generation.
Grading based on degradation rate (P-type/N-type): A+ level ≤1.0%/≤0.5%, A level 1.0%-2.0%/0.5%-1.0%, B level 2.0%-3.0%/1.0%-4.0%, C level >3.0%/>4.0%.
Maintenance and Safety
During exposure, visual inspections must be conducted at least once a month, and modules must be cleaned every 30 days. Snow and debris on the site must be cleared promptly after snowfall, and photos must be taken followed by EL testing after extreme weather events. The test site must be equipped with lightning protection, fire prevention, and other safety facilities.
Summary
SJ/T 11828.4-2026 provides a scientific and systematic testing method for evaluating the performance of photovoltaic modules in extreme cold environments, helping to improve the reliability and standardization of photovoltaic power stations in high-altitude and high-latitude regions. The standard content is comprehensive, with detailed regulations covering sites, equipment, specimens, and data analysis, making it an important technical specification for the photovoltaic industry.