Currently, the main failure modes of photovoltaic modules include corrosion, delamination, discoloration, cracks and fractures, among which discoloration and delamination of packaging materials are the main problems, accounting for 60% of the total failure modes. The main causes of degradation of packaging materials are moisture, heat and ultraviolet rays. In order to test and evaluate photovoltaic modules, it is necessary to analyze the degradation of packaging materials. Millennial Comprehensive Environmental Test Chamber, which can realize automated and easy-to-operate temperature and humidity control systems and various energy-saving new technologies to simulate the environment required for testing; UV Preconditioning Chamber, a UV test system designed to verify the performance changes of photovoltaic modules after ultraviolet light exposure.

EVA degradation

The encapsulant provides structural support, electrical isolation, physical isolation, and physical protection against external harmful environmental factors for photovoltaic modules.

According to recent data reports, the most common degradation mode in the modules used so far is encapsulant discoloration (45%), followed by delamination (14%), hot spots (11%), cell fracture (9%), diode/junction box fracture (8%), and glass breakage (4%). It can be seen that encapsulant discoloration and delamination are the main problems, accounting for 60% of the total failure modes.

Significant Degradation Pattern Pie Chart

Materials used as encapsulants include EVA, POE, TPU, PVB, PDMS and silicone, among which EVA has become the dominant encapsulant for PV applications due to its low cost and high thermal stability.

Market share of different packaging materials

EVA Delamination

EVA loses adhesion strength under high humidity and temperature conditions, causing delamination of the encapsulation material, which increases moisture penetration paths, accelerating cell corrosion and power loss.

Delamination in PV panels

EVA discoloration

The main reason for the power loss of photovoltaic modules is the discoloration of the packaging material, which leads to a reduction in short-circuit current. The discoloration of EVA is mainly caused by ultraviolet radiation, moisture exposure and temperatures above 50°C, which will lead to changes in the chemical structure of the polymer.

EVA photothermal degradation mechanism

As shown in the figure, the discoloration of EVA usually changes from light yellow to dark brown. If the discoloration continues, it will prevent the entry of sunlight and cause power loss. It will also cause the operating temperature of the photovoltaic module to rise, accelerating the degradation of EVA.

EVA Accelerated Test Methods and Analysis

IEC 61215 specifies the approval requirements for crystalline silicon modules to operate in general outdoor climates, where damp heat tests, humidity freezing tests, thermal cycling tests, and UV aging tests affect the encapsulation materials.

IEC 61215 test conditions

UV Testing:

UV aging testing uses a spectral range of 280-400nm with a total radiation exposure of 15kWh/m² at 60±5°C. Used to analyze polymer issues such as encapsulant delamination, adhesion and elasticity loss, discoloration, and ground faults due to backsheet degradation. Degradation accelerates with increasing UV irradiance.

Thermal Cycle Test:

Thermal cycle test is usually used to check for problems such as interconnection fracture, cell fracture, solder bonding failure, junction box adhesion and module connection failure. The thermal cycle test is repeated for 550 cycles from -40°C to 90°C. The discoloration of EVA after thermal cycling will cause the transmittance to decrease, resulting in a decrease in current. P_max drops from 34.6 W to 26.6 W, and I_sc drops from 7.39 a to 6.2 a.

Damp heat and wet freeze test:

EVA has strong hygroscopicity and poor stability. In a 1000-hour damp heat test at 85°C, the mechanism of damp heat degradation will produce acetic acid, which promotes corrosion. This causes EVA to delaminate, leading to gate corrosion, increased series resistance, and decreased Voc slope.

In HF test, 75 cycles were performed, and there was no obvious power drop in the photovoltaic module.

The results of the temperature and humidity test module after simulated UV irradiation showed more obvious EVA degradation than the module without UV irradiation, so the combination of temperature and UV for testing can simulate a test environment similar to the actual one.

The main causes of EVA degradation are moisture, heat and ultraviolet rays. It is necessary to refer to the MQT10, 11, 12, and 13 standards in IEC61215 and use environmental simulation equipment to simulate long-term ultraviolet light and different temperature and humidity environments to analyze the degradation of packaging materials and evaluate whether the performance of photovoltaic modules will change.

Comprehensive Environmental Test Chamber

E-mail: market@millennialsolar.com

Millennial Comprehensive Environmental Test Chamber uses an automated, easy-to-operate temperature and humidity control system and various new energy-saving technologies to simulate the environment required for testing. While improving reliability, it significantly reduces power consumption.

·Built-in circulating air ducts and long-axis fans for effective heat exchange, and the temperature inside the environmental chamber is uniform and stable

·Imported temperature controllers are used to achieve multi-stage temperature programming, high accuracy, and good reliability

·High and low temperature interactive tests can be performed according to the plans of engineers

UV Preconditioning Chamber

E-mail: market@millennialsolar.com

In the cell packaging structure of photovoltaic modules, polymer materials such as EVA, silicone, backplane, junction box and cables will change their performance after long-term ultraviolet light exposure. UV Preconditioning Chamber is mainly designed to verify the performance changes of solar modules after ultraviolet light exposure.

· Mainly used to test the performance of polymer materials of photovoltaic modules

· Multifunctional and customizable

· Meet IEC 61215-MQT10, IEC61730-MST54 standards

EVA is the main packaging material in photovoltaic modules, and its degradation will affect the performance and life of the modules. Exploring the types, causes and test methods of EVA degradation is of great significance to improving the performance and life of photovoltaic modules. Millennial Comprehensive Environmental Test Chamber meets the IEC 61215 standard and uses a temperature and humidity control system to simulate the environment required for the test. In the packaging structure of photovoltaic modules, polymer materials such as EVA, silicone, backplane, junction box and cables will change in performance after long-term ultraviolet light exposure. UV Aging Test Chamber is mainly designed to verify the performance changes of solar modules after ultraviolet light exposure.