Introduction
The efficiency of a PV plant depends on the performance of its modules. If a PV module degenerates, it impacts the overall generation of the plant as each module is electrically interdependent with other modules through string configuration. Hence, a timely performance evaluation of the modules is necessary to achieve the expected lifetime of PV modules.
In India, PV module testing labs are available in various parts of the country. These labs are mostly located away from the plant locations. Thus, if any performance related discrepancy occurs in a solar power plant, the conventional way is to send affected modules to the testing lab with the added cost of transportation and additional damage to the module if not treated delicately. This problem is solved by a mobile PV laboratory developed by us at Mahindra Teqo.
Mahindra Teqo’s mobile PV testing lab is the first of its kind in India. It provides a range of electrical and visual tests of PV modules as per IEC61215/61646 norms. Its robust design can reach various geographical regions of India and can produce reports on the degradation status of PV modules in less than 3-4 days. This laboratory is maintained as per IEC/ISO 17025 standards.
Common modes of degradation in PV modules
There are many modes of degradation in a module which makes the module to underperform or even affects the lifespan of the other modules in the string. Some of the modes of degradation are mentioned below:
- Cell Degradation
- Optical Degradation
- Light Induced Degradation (LID)
- Temperature Induced Degradation
- Potential Induced Degradation (PID)
- Mismatch Loss
- Incident Angle Modifier
- Soiling
The tests that can be conducted in mobile PV testing lab
The mobile lab comprises three major testing equipment which are as follows:
- Thermal Imaging – The IR(Infrared)Scanner/camera is used to detect any hotspot in the module using a thermal imaging technique. The IR inspection of modules is done as per IEC 62446-3 temperature difference in cells which leads to the hotspot. Bypass diode failure or dead cells with high temperature can also be detected using IR imaging. A defect in the module can be identified as IR image is done at string level.
- Electroluminescence (EL) Tester – The EL imaging of the PV modules helps to identify micro cracks and effects of PID (Potential Induced degradation) in Modules. The test measurements are done in a completely dark room to classify the micro cracks present in the module.
- Flash Tester – The flash test is being done with the help of an AAA-class Solar Sun Simulator which gives the I-V characteristics of the PV module at STC (Standard Test Condition.
Methodology for quality analysis using on-site mobile PV lab
Here is our approach while performing tests in the mobile lab:
Key features of mobile PV testing lab
- The lab has a failsafe system which comprises very robust design with no movable parts.
- The Sun Solar simulator is of AAA-class which can be used to test modules of all type of current technologies (mono-Si, poly-Si, Amorphous silicon (aSi, CIS, CIGS), CdTe, HIT & high efficiency).
- The lab is built to meet ISO/IEC 17025 standards enabling it to maintain standards of PV plant with proper quality assurance procedure.
- The lab is accredited as per ISO\IEC 17025 norms by NABL (National Accreditation Board for Testing & Calibration Laboratories).
- When compared to a traditional horizontally mounted system for I-V testing, the vertical mount structure for Flash test and the EL measurements provides an all in one solution cutting down the time required for test analysis and report making.
- The lab requires ZERO set up time for the Dark Room and it has integrated living space for an engineer for instant reporting.
- It is equipped with integrated distributed generation to work without site auxiliary power supply (self-powered).
- Robust and compact model of Lab maintains the STC conditions required for testing.
- The mobile PV Lab I-V test can be conducted during the non-generation hours which don’t affect the generation of PV plants.
- STC condition can be maintained in the lab and there is no need for any translation procedure which is prone to any high uncertainty for the power degradation calculation.
The on-site mobile PV Lab enables the testing of PV plants with the same efficiency as a PV test Lab located remotely, but with the added advantages of cutting down the handling loss of modules during transportation.
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