Experimental

Rooftop system

The inverter-based switching method for DPL image acquisition was demonstrated first on a 12 kWDC / 10 kWAC residential rooftop system at Wylie’s Baths in the eastern suburbs of Sydney. The PV system was commissioned in March 2021 and consists of 35 bifacial 350 Wp glass-glass modules, each containing 120 half-cell PERC cells with a nominal open circuit voltage of 682 mV per cell. The modules are arranged in two series-connected strings that are connected to the DC inputs of a 10 kW SMA Sunnyboy Tripower inverter. DPL measurements were performed on a sunny day in April 2023 using an Indium Gallium Arsenide (InGaAs) camera with a resolution of 1280 x 1024 pixels in conjunction with near-infrared camera objectives with focal lengths ranging from 12.5 mm to 50 mm. A 25 nm bandpass filter with a centre wavelength of 1,137 nm was mounted in front of the camera lens for all measurements to exploit a broad atmospheric absorption band that coincides with the emission spectrum from crystalline silicon at room temperature. The filter increases the relative proportion of the PL signal in each individual image, as previously demonstrated and as discussed in more detail elsewhere .