Solar backsheet (membrane) monitoring of external water vapor barrier performance - Database & Sql Blog Articles

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Abstract: The water vapor transmission rate (WVTR) is a crucial performance indicator used to evaluate the moisture barrier capability of solar backsheet materials. It plays a vital role in monitoring the protection of internal solar cell components and preventing oxidation caused by external humidity. This study employs the W3/330 water vapor transmission rate test system, independently developed by Jinan Languang Electromechanical Technology Co., Ltd., to measure the WVTR of a solar backsheet. The paper outlines the equipment’s parameters, application scope, and testing procedures, providing a practical reference for the solar industry in assessing the moisture barrier properties of backsheet materials.

Keywords: Water vapor transmission rate, moisture barrier, solar backsheet, solar cell, oxidation, test system, EVA film, TPT backsheet, PVF, PVDF, PET

1. Introduction

Solar panels are the core components of solar energy systems, converting sunlight into electricity and contributing significantly to renewable and clean energy development. Given that most solar products are expected to last over 25 years, the solar backsheet must provide exceptional protection to the internal photovoltaic cells. Typically, a solar module consists of a structure like "photovoltaic glass-EVA film-solar panel-EVA film-backboard," all enclosed in an aluminum frame. Common backsheet materials include TPT, BBF, TPE, and EVA films, with TPT being one of the most effective due to its three-layer composite structure—PVF or PVDF/PET/PVF (or PVDF).

As solar modules are often installed outdoors for extended periods, the backsheet must exhibit excellent insulation, water resistance, and aging resistance. It should also have high peel strength, tensile strength, and good heat shrinkage. Among these, the water vapor transmission rate is the most critical factor, as it determines how well the material resists moisture penetration. A high WVTR indicates poor moisture barrier properties, which can lead to EVA adhesive degradation, delamination, and eventual oxidation of the solar cells. In this study, the W3/330 test system was used to evaluate the moisture barrier performance of the solar backsheet material.

Width=447 height=232 src=http://i.bosscdn.com/blog/20/17/10/2117947463708.jpg /></p> <p align=Figure 1: Solar cell module structure diagram

width=330 height=305 src=http://i.bosscdn.com/blog/20/17/10/2117949892779.jpg
Figure 2: Solar backing material

2. Current Status

Currently, several methods are used in China to measure the water vapor transmission rate of flexible plastic materials, including the gravimetric (cup) method, electrolytic method, humidity method, and infrared method. Relevant standards include GB 1037-1988, GB/T 16928-1997, GB/T 21529-2008, and GB/T 30412-2013. In this study, the electrolytic sensor method (GB/T 21529-2008) was applied to test the WVTR of the solar backsheet.

3. Test Samples

A specific brand of solar backsheet (film) was selected for the experiment.

4. Test Equipment

The W3/330 water vapor transmission rate test system, developed by Jinan Languang Electromechanical Technology Co., Ltd., was used for this study.

Width=300 height=225 src=http://i.bosscdn.com/blog/20/17/10/2117950291317.jpg /> Figure 3: W3/330 water vapor transmission rate test system</p> <p>4.1 Test Principles</p> <p>The W3/330 system uses the electrolytic sensor method. Dry nitrogen flows on one side of the sample, while humidified nitrogen flows on the other. Water vapor diffuses through the film and is carried to the sensor by the dry gas stream. The sensor generates an electrical signal proportional to the amount of water vapor, allowing the calculation of the WVTR. For containers, the inside is kept dry while the outside is exposed to high humidity.</p> <p>4.2 Device Parameters</p> <ul> <li>Test range for film samples: 0.001–40 g/(m²·24h), extendable to 0.01–1000 g/(m²·24h); resolution: 0.001 g/(m²·24h)</li> <li>Test range for container samples: 0.0001–0.2 g/(pkg·24h); resolution: 0.00001 g/(pkg·24h)</li> <li>Temperature range: 15°C–55°C; accuracy ±0.1°C</li> <li>Humidity range: 0% RH, 35%–90% RH, 100% RH; accuracy ±1% RH</li> <li>Three independent test chambers for simultaneous testing without interference</li> <li>Supports up to 10 stations, enabling testing of 30 samples at once</li> <li>Includes standard membranes for calibration and compatibility with oxygen transmission rate systems</li> </ul> <p>4.3 Application Scope</p> <p>This device is suitable for testing the WVTR of various materials, including films, sheets, papers, cardboard, and packaging containers. It can be used for solar backplanes, LCD films, medical blister packs, pharmaceutical bottles, automotive fuel tanks, and more. It complies with international standards such as GB/T 21529, ISO 15106-3, DIN 53122-2, and YBB 00092003.</p> <p>5. Test Procedure</p> <ol> <li>Cut three 108 mm × 108 mm samples from the surface of the specimen.</li> <li>Mount the samples in the three test chambers and secure them.</li> <li>Set parameters such as sample thickness, temperature, and humidity.</li> <li>Adjust nitrogen flow to achieve the desired humidity levels in both chambers.</li> <li>Start the test and allow the system to automatically record and calculate the results.</li> </ol> <p align=width=549 height=129 src=http://i.bosscdn.com/blog/20/17/10/2117952361942.jpg /><br> Figure 4: Sample clamping process</p> <p>6. Test Results</p> <p>The WVTR values for the three samples were: 1.2405 g/(m²·24h), 1.3114 g/(m²·24h), and 1.3075 g/(m²·24h), respectively.</p> <p>7. Conclusion</p> <p>The W3/330 water vapor transmission rate test system is a reliable and precise tool for evaluating the moisture barrier performance of films, sheets, and containers. Its high accuracy and repeatability make it ideal for assessing the long-term durability of solar backsheet materials. In addition to WVTR testing, Labthink also offers equipment for tensile and peel strength testing of solar backsheets. For more information about our testing solutions, please visit our website or contact us directly. Jinan Languang Electromechanical Technology Co., Ltd. is committed to supporting the solar industry with advanced technology and quality service.</p><p><span class=55 Inch Interactive Conference Board

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