[PV Panel Quality] Sharp's Accelerated Degradation Test (2)
Test based on data of 30-year application
Continued from [PV Panel Quality] Sharp's Accelerated Degradation Test (1)
Accelerated degradation test itself is knowhow
Sharp disclosed all of its quality evaluation standards to VDE for evaluation and incorporated the "repeated air pressure test" specified by VDE and the "terminal strength test" for the strength evaluation of terminals (cables) that connect the modules. Among the quality evaluation standards exclusive to Sharp, the accelerated degradation test was the most highly evaluated by VDE.
"For establishing an accelerated degradation test of high reproducibility, it is essential to evaluate the details of the deterioration conditions of solar panels that have operated in the actual field for a long period and determine the conditions for reproducing the states of deterioration," said Hideki Yoshioka, general manager, Quality Control and Environment, Solar Systems Division, Sharp. "It is a huge advantage for us that we commercialized solar panels at an early stage and possess the data on long-term use."
In addition to the solar panels that have been in operation for about 30 years at Tsubosaka Temple, Sharp installed the panels of 4kW output at the Japan Weathering Test Center in Choshi City, Chiba Prefecture, roughly 20 years ago. The company also installed 80 sheets of 70W solar panels at Rokko Island in Kobe in 1986 as part of the validation project implemented by NEDO (New Energy and Industrial Technology Development Organization). According to Sharp, it has accumulated data for analysis of deterioration states in the field.
"The accelerated degradation test, which is based on the deterioration data, itself, is the knowhow, and we have not disclosed the detailed contents," Yoshioka said.
The outline of the test is as follows. The IEC standard requires 200 cycles of temperature loading, setting temperature change from -40°C to 85° in six hours as one cycle. But the Sharp standard sets the temperature at -40° to 90° with more cycles, and the test frequency is set at about 10 times the frequency specified by the IEC standard.
As for humidity load assuming condensation and freezing, the IEC standard requires 10 cycles of humidity loading, setting the temperature change from -40° to 85° in 24 hours under 85% humidity as one cycle. On the other hand, Sharp sets the cycles to roughly 10 times the cycles specified by the IEC standard (Fig. 1). VDE has its own standard for the test, but Sharp continues to incorporate the original standard even after collaboration with VDE.
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