Performance testing under Standard Test Conditions (STC) is one of the most fundamental evaluations in photovoltaic (PV) module qualification. Within IEC 61215-2:2021, the MQT 06 test focuses on verifying the electrical performance of PV modules under controlled laboratory conditions.
This test plays a critical role in validating module nameplate ratings, assessing power degradation after stress testing, and ensuring consistency in PV module performance measurements across the industry.
What is MQT 06 in IEC 61215-2:2021?
MQT 06, titled Performance at STC, is defined in IEC 61215-2:2021 as a specialized form of maximum power determination (MQT 02) performed under Standard Test Conditions.
The test determines how the electrical performance of a PV module varies with load under the following STC conditions:
• Irradiance: 1000 W/m²
• Cell temperature: 25°C
• IEC 60904-3 reference solar spectral irradiance distribution
The primary objectives of MQT 06 are:
• Verification of module nameplate power ratings
• Determination of power loss after reliability stress tests
• Evaluation of module electrical characteristics under standardized conditions
Purpose of MQT 06 Testing
The MQT 06 test is designed to measure the current-voltage (I-V) characteristics of the PV module while operating under tightly controlled environmental conditions.
The test helps manufacturers, laboratories, and project stakeholders:
• Validate declared power output
• Compare module performance consistently
• Detect degradation after environmental or mechanical stress testing
• Assess electrical stability and reproducibility
Because module performance can vary due to spectral mismatch and temperature deviations, the standard also emphasizes uncertainty control and correction methodologies.
Apparatus Requirements for MQT 06
IEC 61215-2:2021 specifies that the apparatus used for MQT 06 testing shall include the same equipment required for MQT 02 testing, along with additional monitoring capabilities.
Temperature Monitoring
The testing system must include temperature monitoring equipment capable of:
• Accuracy: ±1°C
• Repeatability: ±0.5°C
This ensures reliable correction and stabilization of module temperature during measurements.
Requirements for Bifacial Modules
For bifacial PV modules, the radiant source used during testing must support:
• Adjustable irradiance levels
• Rear-side irradiance capability
• BNPI (Bifacial Nameplate Irradiance) testing methods according to IEC TS 60904-1-2
These additional requirements ensure accurate characterization of bifacial module behavior under realistic irradiation conditions.
Requirements for Multi-Junction Modules
For multi-junction modules, the simulator and reference device must comply with the additional specifications outlined in IEC TS 60904-1-1.
MQT 06 Testing Procedure
The IEC standard outlines a detailed procedure for measuring PV module performance at STC.
1. Maintain Controlled Conditions
The PV module must be maintained at:
• Temperature: 25 ± 2°C
• Irradiance: 1000 ± 100 W/m²
Irradiance must be measured using a suitable reference device in accordance with IEC 60904-1.
2. Trace the I-V Curve
The current-voltage (I-V) characteristic of the module is measured to determine key electrical parameters such as:
• Open-circuit voltage (Voc)
• Short-circuit current (Isc)
• Maximum power (Pmax)
This measurement establishes the module’s electrical performance under STC.
3. Temperature Correction
If the module temperature deviates from 25°C, corrections shall be applied using:
• Temperature coefficients
• IEC 60904 series
• IEC 60891 correction methods
These correction methods improve accuracy and consistency across testing environments.
Special Requirements for Bifacial Modules
Bifacial modules require additional measurement considerations under IEC 61215-2:2021.
Testing shall follow IEC TS 60904-1-2 requirements, including measurements at:
• STC
• BNPI (Bifacial Nameplate Irradiance)
The following bifaciality coefficients may also need to be measured:
• Short-circuit current bifaciality coefficient
• Open-circuit voltage bifaciality coefficient
• Power bifaciality coefficient
The standard notes that post-stress evaluations may only require BNPI measurements, depending on the specific MQT stress test procedure.
Additionally, IEC 60891 correction methods may be used to adjust irradiance to the desired equivalent front-side irradiance.
Flexible and Very Large Modules
IEC 61215-2:2021 also includes special provisions for flexible and very large PV modules.
Flexible Modules
Flexible modules must be measured while fully unfolded and flat during maximum power determination.
Very Large Modules
For very large modules, testing may be conducted at the manufacturer’s facility, provided all apparatus and measurement requirements remain compliant with IEC 61215-2:2021.
Importance of MQT 06 in PV Quality Assurance
MQT 06 testing is essential for ensuring the reliability and bankability of PV modules.
Accurate STC performance measurements help:
• Verify manufacturer claims
• Support investor confidence
• Establish baseline performance before and after stress testing
• Ensure compliance with international certification standards
As PV technologies continue to evolve, especially with bifacial and multi-junction designs, standardized STC testing remains a critical part of photovoltaic quality assurance and certification.
Conclusion
IEC 61215-2:2021 MQT 06 provides a structured framework for evaluating PV module electrical performance under Standard Test Conditions. By controlling irradiance, temperature, and measurement uncertainty, the test ensures consistent and repeatable performance verification across different module technologies.
From conventional monofacial modules to advanced bifacial and multi-junction designs, MQT 06 remains a cornerstone test in modern PV module qualification and quality assurance programs.
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