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 .