LONGi’s Hi-MO 5 bifacial module has recently passed the China General Certification Center (CGC)’s inhomogeneous snow load test, which simulates a beamless installation, where the back of the module does not touch the beam during deformation. The results indicated that, for five Hi-MO 5 modules, critical snow load (at point of failure) reached or exceeded 6400Pa, with the highest load reaching 7400Pa. Considering the safety factor, the inhomogeneous snow load of the Hi-MO 5 was 4341Pa, although, for 3.1m2 modules tested at the same time, the average critical snow load was 4600Pa, 3066Pa when taking into account the safety factor. Following wind tunnel, hail and ultimate dynamic load testing, the reliability of LONGi modules in terms of size and structural design has again been verified.
Significance of inhomogeneous snow load testing
LONGi
Compared with real snow load characteristics, mechanical load testing is unable to apply extreme stress to the framing section at the lower part of a module at an inclined exposure. Snow loads tend to creep downhill and invade the potential space between frame edge and top surface, the ice formed by compression of the lower snow areas pushing against the exposed tip of the frame, making the load on the modules inhomogeneous. As length and width of a module increases, the local pressure and bending moment caused by an inhomogeneous snow load increase significantly, making it important to evaluate the performance of larger-sized modules under such conditions.
Methodology of inhomogeneous snow load testing
LONGi
According to the IEC 62938:2020 inhomogeneous snow load testing standard, a step-distributed non-uniform load is applied to 2/3 of the length of a module at a specified inclination angle (usually 37°), with the load gradually increased to measure the critical point at which the module is damaged, the sample result of five modules subsequently used to calculate the average. Finally, the inhomogeneous snow load is obtained by applying a safety.
Hi-MO 5 inhomogeneous snow load test results
LONGi
Larger-sized bifacial modules are currently applied mainly in portrait installation. In order to avoid the influence of the beam on backside power generation, the modules are usually raised by clamps to increase the distance between the back glass and the beam, with the installation method for this test similar to the above scenario. The backside of the module does not touch the beam during the test, which is more critical than for a conventional test.
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In addition to obtaining the critical load of a module, this test also records deformation of the lower edge relative to the module’s center point under different loads. Hi-MO 5 not only has a significantly higher snow load tolerance than a 3.1 square metre module (2384×1303mm), but also presents significantly lower deformation under a specific pressure. The critical load of a 3.1 square metre module is low, with deformation exceeding 50mm under a load of 3600Pa. In practical application, long-term excessive deformation may potentially lead to problems such as cracks in the cells, deformation of the frame and glass breakage.
LONGi
What do these results tell us?
In summary, module size is strongly linked to mechanical properties. Whether extreme dynamic load, hail, wind tunnel or inhomogeneous snow load testing, all tests indicated that size should have reasonable limits. With its optimal sizing insight and reliable design, Hi-MO 5 performs very well in extreme climatic conditions and LONGi will adhere to its product design concept based on LCOE, paying attention to the application performance of a product throughout its life cycle, and continuing to develop technologies and products. (mfo)
