Daytime EL & PL Empirical Test Report for PV Modules

Test Scenario 1

Test Date: September 2025

Test Location: A centralized photovoltaic power station in Qinghai, with an altitude of approximately 3000 meters

Time: 9:30 – 19:00

Weather: Cloudy   Temperature: 10℃ – 23℃    Humidity: 66%

组件1（N型）-测试时阳光直射
PL
The module is damaged and cannot be powered on, rendering the EL test invalid.
组件2（N型）-测试时阳光直射
PL
The module is damaged and cannot be powered on, rendering the EL test invalid.
组件3（N型）-测试时阳光直射
EL
PL
组件4（N型）-表面玻璃碎裂-测试时阳光直射
EL
PL
组件5（TOPCON）-测试时有薄云层
EL
PL
组件6(N型)-测试时有薄云层
EL
PL
组件7（多晶）
EL

Test Scenario 2

Test Date: September 2025

Test Location: A distributed photovoltaic power station in Qinghai, with an altitude of approximately 2000 meters

Time: 11：00~12：00

Weather:Sunny with direct sunlight     Temperature: 20℃ – 22℃    Humidity:51%

组件1（BC）

EL

PL

组件2（单晶PERC）

EL

Test Scenario 3

Test Date: August 2025

Test Location: A rooftop distributed photovoltaic power station in Jiangsu, with an altitude of approximately 100 meters

Time: 17：00~18：00

Weather:Overcast    Temperature:35℃    Humidity:80%

Irradiance：40w/m²

检测最下方一排组件PL，组件如下图：

检测结果统计表：

Total Number of Inspections	23
Number of Modules with Microcracks	5
Detection Rate of Modules with Microcracks	21.74%
Total Number of Microcracks	9
Module1-2：Number of Microcracks（0）
Module3-4：Module3 Microcracks（5），Module4 Microcracks（1）
Module5-6：Module5 Microcracks（1）
Module7-8：Microcracks（0）
Module9-10：Microcracks（0）
Module11-12：Microcracks（1）
Module13-14：Microcracks（0）
Module15-16：Microcracks（0）
Module17-18：Microcracks（0）
Module19-20：Microcracks（0）
Module21-22：Microcracks（1）
Module23：Microcracks（0）

Conclusion：

 Tests on various types of PV modules for PL and EL were conducted at centralized and distributed photovoltaic power stations located in Qinghai (plateau region) and Jiangsu (plain region). The tests covered different environmental conditions including direct sunlight and cloud cover, as well as different time periods such as morning, noon, afternoon and dusk. A wide range of defects were detectable, including virtual soldering, microcracks, bypass diode failure, contamination and scratches.

Adventage：

Daytime EL/PL testing is safer and more efficient than nighttime testing. This advantage is even more pronounced for centralized power stations located in wilderness areas, mountainous regions, on water surfaces and in low-lying lands, as well as for distributed power stations installed on high-rise rooftops.

During the construction phase of power stations, daytime EL/PL testing enables convenient random inspection of incoming modules outdoors in daylight hours, eliminating the need for testing at night or in indoor darkrooms.