Mitsui Chemicals India Backsheet Durability Test Sequence (BDTS)

Why is BDTS testing required?

Solar PV modules require the Backsheet Durability Test Sequence (BDTS) to ensure the long-term performance, safety, and reliability of the photovoltaic (PV) panels. The back sheet is a critical & vulnerable component of a solar module, located on the rear side of the PV cells. It serves as a protective layer that shields the sensitive solar cells from External environmental factors and provides electrical insulation.

When it comes to solar panels, the durability of the backsheet is crucial for long-lasting performance. MCIND (Mitsui Chemicals India) , a leading company in the solar industry, has developed a Backsheet Durability Test Sequence (BDTS) to ensure the reliability of backsheet materials used in photovoltaic (PV) modules. Let’s explore the simplified steps of this test:

Step 1: Factory Witness and Intake: The BDTS begins by recording the materials used in module production through a factory witness. This helps maintain a record of the bill of materials (BOM) used in case of any issues. A sample coupon of the backsheet is saved for further verification if needed. The module also undergoes baseline characterization during this stage.

Step 2: Damp Heat: In this step, the module is placed in an environmental chamber at high temperature (85°C) and humidity (85%) for 1000 hours. This stress test helps identify degradation-prone materials by breaking down their bonds.

Step 3: Characterization: The backsheet undergoes several tests, including wet leakage to check for possible grounding issues, visual inspection for cracking and chalking, and color measurement to detect any yellowing using a specialized colorimeter.

Step 4: UV Light: The module’s rear side is exposed to UV light, simulating sunlight, to cause UV degradation. This step mimics the effects of long-term exposure to sunlight in the field, typically equivalent to 15 to 20 years, depending on environmental conditions.

Step 5: Dynamic Mechanical Load Test, Thermal Cycling, and Humidity Freeze: These tests create mechanical stress on the backsheet to understand its bond strength and resilience. The Dynamic Mechanical Load Test (DMLT) assesses the sealant bond between backsheet layers. Thermal cycling involves subjecting the module to extreme temperature changes, while humidity freeze drives moisture into the module.

Test Results Replicating Field Failures in the Lab: MCIND’s BDTS successfully replicates the common issues observed in the field, such as yellowing, chalking, and cracking of backsheet materials. The goal is to recreate these failure modes in a controlled laboratory setting. The test also helps identify both high and low-quality backsheets available in the market.

Figure 1: Crack formed after 2nd round of BS durability testing

Figure 2: Cracks formed in the backsheet after 1st round of BS durability sequential testing

Figure 3: No Crack formed in backsheet after 3rd round of Backsheet sequential testing

Advantages of MCIND’s Backsheet Durability Sequence

MCIND’s BDTS is performed on complete PV modules with a witnessed BOM, ensuring representative results and material traceability. The inclusion of rear-side UV in the test more accurately reflects the back sheet’s behaviour in real-world conditions. By using the data from MCIND’s Component Qualification Program, downstream buyers can avoid the financial consequences of choosing modules with faulty backsheets. Manufacturers can also leverage the independent data from MCIND’s BDTS to demonstrate the long-term reliability of their PV modules.

In conclusion, MCIND’s Backsheet Durability Test Sequence is a crucial step in ensuring the long-term performance and reliability of solar PV modules. By subjecting the backsheets to various stress tests, MCIND helps identify potential issues and assists buyers and investors in making informed decisions to avoid underperformance in their solar assets.

Source: Representation of actual site backsheet failure due to Arc-ing

Source: Representation of actual site backsheet failure due to Arc-ing + surface glass broken

Mitsui Chemicals is an ESG-enabled organisation, offering a spectrum of services and expertise in the domain of solar power generation in India. This expertise has enabled us to become the first Japanese company to set up a BIS (Bureau of Indian Standards) testing and certification lab.We are proud to have completed technical due diligence for 4GW-6GW in Japan, a pioneering work in the field of solar diagnostics

We are committed to building a progressive future that is safe and convenient for everyone. Thus, all our products and services contribute to achieving the long-term goal of sustainable development.

For further information, please contact us at: https://in.mitsuichemicals.com/contact/

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