1 Scope
This document defines a test sequence that will quickly uncover CPV module failures thathave been associated with field exposure to thermal cycling for many years. This documentwas specifically developed to relate to thermal fatigue failure of the HCPV die-attach, however,it also applies,to some extent,to all thermal fatigue related failure mechanisms for theassemblies submitted to test.
IEC 62108,the CPV module qualification test already includes an accelerated thermal cyclesequence in one leg of the testing,however,the parameters of that test only represent aqualification level of exposure. This test procedure applies more stress and will provide aroute for comparative testing to differentiate CPV modules with improved durability to thermalcycling and the associated mechanical stresses.
Normative references
The following documents are referred to in the text in such a way that some or all of theircontent constitutes requirements of this document. For dated references,only the editioncited applies. For undated references, the latest edition of the referenced document (includingany amendments) applies.
IEC 62108:2016,Concentrator photovoltaic(CPV) modules and assemblies – Designqualification and type approval
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
IsO and lEC maintain terminological databases for use in standardization at the followingaddresses:
. IEC Electropedia: available at http://www.electropedia.orgl
. iso Online browsing platform: available at http://www.iso.orglobp
system’s capacity to resist degradation specific for a particular stress or set of stresses
Note 1 to entry: The durability with respect to all relevant stresses shall be assessed in order to gain informationabout the anticipated performance of the system.
probability for a system to perform and maintain its designed function in specific conditions fora specified period of time
Note 1 to entry.: In this context the term reliability shall be accompanied by three numbers: a) a specified period oftime, b) a criterion that quantifies its performance at that time and c) the probability that the criterion will be met.
concentrator receiver
group of one or more concentrator cells and secondary optics (if present) that acceptsconcentrated sunlight and incorporates the means for thermal and electric energy transfer.Areceiver could be made of several sub-receivers.The sub-receiver is a physically standalone,smaller portion of the full-size receiver
[SOURCE: IEC 62108:2016,3.4]
concentrator module
group of receivers,optics, and other related components,such as interconnection andmounting,that accepts unconcentrated sunlight. All above components are usuallyprefabricated as one unit, and the focus point is not field adjustable
Note 1 to entry: A module could be made of several sub-modules. The sub-module is a physically stand-alone,smaller portion of the full-size module.
concentrator assembly
group of receivers,optics, and other related components, such as interconnection andmounting that accepts unconcentrated sunlight. All above components would usually beshipped separately and need some field installation, and the focus point is field adjustable
Note 1 to entry: An assembly could be made of several sub-assemblies. The sub-assembly is a physicallystandalone, smaller portion of the full-size assembly.
[SOURCE: IEC 62108:2016,3,6]
4 Sampling
For non-field-adjustable focus-point CPv systems or modules, a number of modules thatcontain at least 20 separate PV cells are required.Test failure is based on the failure of 5 %of the submitted cells; therefore submission of more than 20 cells is encouraged.
lf coordinated between the submitting manufactured and testing laboratory,disassembly ofthe submitted module(s) into a separate receiver or receivers for the thermal cyclingsequence is acceptable and encouraged.This approach may be desirable in order to reducethermal mass thereby enabling the possibility to achieve a faster temperature ramp rate.Following the thermal cycling sequence,the receiver shall be reassembled into its moduleconfiguration for the outdoor exposure. The original submission of receivers for test is alsoacceptable,provided they may subsequently assembled into a module for the requiredoutdoor exposure.