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Device and Methods for Mechanical Load Testing of Photovoltaic Modules

Stage: Development

State-of-the-art quality-assurance approaches limit photovoltaic (PV) modules’ comprehensive design testing to only general approximations of real-world PV-module operating conditions faced in the field. Due to partial physical obstruction by state-of-the-art testing equipment, load-bearing tests do not capture module performance under simultaneous high-frequency vibrations experienced in high winds, thermal stresses from extreme temperatures, and weathering from water ingress. As the serial testing of individual stressors does not accurately replicate real-world situations, researchers at NREL have developed a novel device for mechanical load testing of PV modules. NREL’s device rapidly displaces the whole module from connections at the module’s edges. In conjunction with mechanical stress, the PV module’s surface remains open to test other stressors, like heat, moisture, light, and voltage, for accurate performance evaluation and quality control.



NREL’s device applies forces to only the edges or frame of a photovoltaic (PV) module such that its active cell area remains free from obstruction. Using electromagnetic, electro-mechanical, or piezoelectric-based actuators and position-adjustable mechanical stops, the device can control the magnitude, direction, and frequency of repeated displacements for oscillatory motion at frequencies between 25 and about 400 Hz. The body of the PV module conveys displacement forces from the module’s edges to all regions of the module. Noting that a PV module is not perfectly rigid, forces applied to its edges cause stress and elastic strain throughout its entirety. In other words, the forces applied to a module’s edges will cause temporary flexing in the center of a module to replicate the mechanical fatigue experienced during deployment in the field. The displacement may be monitored by optical (e.g. a laser), electrical (e.g. a strain gauge), or physical (e.g. a linear variable differential transformer) sensing means.


NREL’s device enables testing methods that provide an unobstructed optical path to both sides of the module’s laminate surface. Beyond replicating real-world oscillatory mechanical fatigue, NREL’s device allows concurrent mechanical loading with illumination, electro-optical testing, or optical inspection, unlike existing PV module mechanical-testing tools. Moreover, NREL’s methods allow the simultaneous application of multiple stressors that may include mechanical, optical, thermal, hydrolytic, and electrolytic stimuli. Even under the application of multiple stressors simultaneously, the response of the full active portion of the PV module can be measured.


To learn more about the Device and Methods for Mechanical Load Testing of Photovoltaic Modules, please contact Bill Hadley at:
bill.hadley@nrel.gov
ROI 19-64.

Applications and Industries

  • PV manufacturers
  • PV-module testing facilities

Benefits

  • Unlike existing PV-module testing equipment, NREL’s device enables accurate simulation of real-world stressors that cause PV-module fatigue and determination of PV-module performance during real-world fatigue simulations.
  • NREL’s device and testing method can provide unprecedented module-performance-assessment accuracy and quality control.
  • NREL’s device mechanically actuates the edges or frame of a PV module to provide an unobstructed optical path to both sides of the module’s laminate surface.
  • NREL’s device enables concurrent mechanical, optical, thermal, hydrolytic, and electrolytic stress-testing methods for accurate simulation of a module’s performance and fatigue caused by wind and snow loads, extreme temperatures, precipitation, and optical degradation.