- South Africa’s Council for Scientific and Industrial Research’s (CSIR) boasts a state of the art photovoltaic (PV) module quality and reliability testing laboratory – a first of its kind for Africa – which includes world-class equipment for localising accelerated reliability stress testing on PV modules.
- This ensures that only high-quality modules that are suitable to the unique South African climate are developed and installed.
The CSIR’s accelerated stress tests provide quantitative metrics for evaluating the performance and reliability of solar PV modules over time. “The tests accelerate the failures in poorly constructed modules that can otherwise take years to occur naturally in the field, thereby helping to ensure reliable solar PV plant performance. Like a referee on the field, the lab tests ensure that the suppliers play fair and provide only high-quality and reliable modules”, says CSIR solar PV expert, Lawrence Pratt.
The environmental and mechanical stress testing forms the foundation for the pre-qualification of new concepts, certification of new PV modules and reliability testing of existing PV technology. “We have the equipment, experience and expertise to conduct testing on most of the common PV technologies, including crystalline, thin film, high capacitance and bifacial modules,” explains Pratt.
The PV module quality and reliability testing services are designed around specialised equipment for PV module extended reliability. The specialised equipment includes environmental chambers to simulate the real-world environmental conditions listed below:
- Thermal cycling of modules from -40 C to 85 C for 200, 400, and 600 cycles to simulate stress from thermal expansion and contraction.
- Humidity freeze testing: 85 C / 85% RH for 20 hours and a -40 C freeze for 10, 20, and 30 cycles to stress the lamination and adhesion strength of the PV module.
- Damp heat testing: 85 C / 85% RH for 1 000 hours, 2 000 hours, with and without electrical bias to stress the adhesion and insulation of the PV module.
- Mechanical load testing: static and dynamic load for simulating transportation, installation, and wind loads that may lead to broken cells and weakened interconnections.
The lab also operates specialised characterisation equipment to measure the electrical performance and safety aspects of the PV module. Pratt points out that the sun simulator outputs an equivalent dose of energy nearly identical to the sun’s energy and spectrum, but only for a fraction of a second. “This is just enough time to accurately and precisely record the current, voltage and power output of the PV module across various temperatures (15 °C and 75 °C) and light intensities (200 W/m2 to 1100 W/m2)”, he says.
The sun simulator is used to compare the output of the PV module as measured at the factory against an independent standard. The sun simulator is also critical to quantify the impact of the accelerated stress tests described above. Finally, the high potential electrical tester helps to identify failures in the insulation resulting from accelerated stresses. Failures in electrical insulation indicate a potential risk to the safe and reliable performance of PV modules over time.
The PV team at the CSIR also offers outdoor test services for module-level performance testing, soiling studies, degradation studies and small-scale string inverter system testing in a real-world environment.
Author: Bryan Groenendaal