To detect potential defects in the solar cells seen in solar panels, it is necessary to have a highly sensitive camera that can capture images in very low light conditions. Solar technology is gaining momentum from green initiatives and is increasingly becoming a part of everyday devices. It will continue to serve as a turnkey power source for everyday products. Lumenera provides scientific grade CCD cameras for inspection of solar panels.
Technical Background of Solar Cells
Solar cells convert solar energy into electricity and are commonly found in solar panels or compact solar powered devices such as camping lanterns, phone chargers, and flashlights. Solar panel inspection is performed to detect the possible defects in the silicon solar cells present in the panel because the presence of defects would influence the efficiency and service life of the cell.
The application of a voltage or current stimulates silicon solar cells to emit photons (light) at a wavelength range of 950-1250nm, with the peak occurring at roughly 1150nm. Silicon cells with a longer diffusion length exhibit brighter luminescence and higher conversion efficiency. It is possible to determine the efficiency of the solar cells by the diffusion lengths and light emitted through imaging this process. This approach helps detecting those cells containing defects.
Challenges in Solar Cell Inspection
Electroluminescence tests for uniformity involve supplying of electric currents through the solar cells that stimulates them to emit photons. The influence on the emission of light by the possible holes or defects in the cell indicates their presence.
An electroluminescence system needs a lens, camera, and an enclosure free from ambient light. After placing the solar cell inside this enclosure, it is linked to a constant current source. The camera captures an image whilst the current passes into the cell. This image will then be studied for dark defects, uniformity, and overall efficiency of the cell. Based on the severity of the defects, the cell will either be accepted or rejected.
The solar cell inspection is a challenging process that needs a camera capable of snapping clear images at a specific wavelength range of 950-1250nm. The camera must have the ability to precisely render the whole panel in a single snap and an adequate resolution that enables the operator to easily detect broken contacts, different light intensities, micro-cracks, and uniformities of the emitted photons to electrons that would otherwise not be possible by a visual inspection.
Imaging Solution from Lumenera
Figure 1. INFINITY3-1M for Electroluminescence.
With the INFINITY3-1M scientific grade camera (Figure 1), Lumenera and Titan Electro Optics have been witnessing significant success in the solar cell inspection market. When employed in electroluminescence solar cell inspection, this high speed USB 2.0 camera is able to inspect the whole cell in a single snap.
With a 1.4MP CCD image sensor, the INFINITY 3-1M provides a cooling feature that minimizes dark current (.015e-/s) and thermal noise during electroluminescence. The CCD sensor has a cut-off wavelength at 1100nm to determine the short wavelength tail of the band-to-band luminescence emitted from silicon solar cells at room temperature.
Figure 2. An electroluminescence system featuring the INFINITY 3-1M.
The INFINITY 3-1M provides a fully customizable SDK. With a feature-rich API library, the camera removes design risk, enables full access to camera controls, and facilitates integration and camera exchange. Ascertaining the solar cells used in the solar panels are defect free and facilitates manufacturers to minimize rework and optimize module efficiency. An electroluminescence system featuring the INFINITY 3-1M is illustrated in Figure 2.
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This information has been sourced, reviewed and adapted from materials provided by Lumenera Corporation.
For more information on this source, please visit Lumenera Corporation.