The standard “EN IEC 62788-1-5 Measurement procedures for materials used in photovoltaic modules - Part 1-5: Encapsulations - Measurement of the linear dimensions of the sheet encapsulation material resulting from the applied thermal conditions”, which has its basis in a European standard and was later published by the International Electrotechnical Commission (IEC), describes a method for measuring the maximum representative change in the linear dimensions of the sheet encapsulation material in an unrestricted thermal exposure, which may or may not be visible during the manufacture of a photovoltaic (PV) module.
This standard does not take into account any induced stresses that may develop due to restrained dimensional changes or friction during module manufacturing. Data obtained using this method can be used by encapsulation material manufacturers for quality control of encapsulation materials and for reporting purposes in product data sheets. Data obtained using this method can be used by PV module manufacturers for material acceptance, process development, design analysis or failure analysis purposes. This method can also be used to examine other materials such as backsheets and frontsheets as described in IEC 62788-2. Specific details of the test (including sample size and substrate) are specified for this application in 62788-2.
In principle, the encapsulation material (in sheet form) can change its dimensions when processed during the production of a PV module. The change in dimensions is usually due to stresses generated during the production of the encapsulation material (e.g. extrusion). Subsequent changes during module production (e.g. including lamination, heating, cooling and pressurization) can cause stresses inside the module that can lead to detrimental events: formation of bubbles (voids), movement or breakage of internal components or delamination at the interface of the encapsulation. In this procedure, a standardized characterization of the maximum change in dimensions is defined. The change in dimensions is characterized on sand to minimize friction or adhesion in order to standardize the result. The stress and strain generated during module lamination are complicated by additional factors that are not considered here. Effects specific to the processing (lamination) procedure are not necessarily addressed in this procedure.
The main equipment used in these tests includes:
When preparing samples for testing, square samples of 100 mm × 100 mm are cut from a received roll of encapsulation material that has been verified to have been stored according to supplier recommendations and has not exceeded its expiration date. Samples should be obtained at least 200 mm from the outer edges of the roll. A carefully cut edge that minimizes dimensional variation (in length and width) should be used. The exact sample size may vary slightly (plus/minus 5 mm) from the intended size, but all samples should be smaller than the piece of aluminum foil.
Some users may wish to perform the test procedure for other purposes, such as verifying the uniformity of material across the width of an encapsulation roll. In such cases, material can be sampled from other locations within the roll. Samples should be held firmly without sudden movements during and after preparation to prevent excessive stressing of the material. Each sample is marked with the machine direction (along the roll length) and the cross direction (across the roll width).
After cutting to size, any interleaf, liner or release film should be removed from the encapsulation samples. The thickness of the encapsulation test sample should be measured after preparation. The thickness should be taken as the average of three values obtained at different locations on the sample, preferably away from cut edges that may have been deformed during cutting. It is recommended to wear gloves to prevent contamination of the samples or the roll of material during sample preparation. A consistent thickness measurement technique should be used for the thickness measurement applied in this standard for reference only, as some encapsulation products have embossed or surface textured surfaces.
Our organization has a strong staff that closely follows the developments in the world in the field of science and technology and constantly improves itself. Among the numerous test, measurement, analysis and evaluation studies provided for businesses in various sectors, there are also test services in accordance with the standard “EN IEC 62788-1-5 Measurement procedures for materials used in photovoltaic modules - Part 1-5: Capsules - Measurement of changes in linear dimensions of sheet encapsulation material resulting from applied thermal conditions”.
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