Measurement of spectral response on cell level
SR is measured in the range of 300 nm to 1200 nm using 42 monochromator filters for reference module. The spectral response data are used for the correction of the module measurement, thus it is necessary that the reference module is built up identically and with the same materials like the modules to be measured. For each type of module we need one additional module for spectral response measurements. We have to open the backside of that module in order to contact one single cell within the module. Please note that the module will be destroyed, since this is a destructive test.
Stabilization of PV modules with a continuous solar simulator
Stabilization is performed for 20 hours at 1000 W/m² and operating conditions at Pmpp prior to calibration.
Images with electroluminescence camera
Subsequent to the STC measurement, an electroluminescence image of the PV module will be taken for the inspection of cells. Defects which are not visible to the eye, such as micro-cracks or grid finger defects can be detected. Electroluminescence is the emission of light in response to the passage of an electric current in consequence of a voltage externally applied to the PV module. A sensitive CCD camera takes an image of the electroluminescent intensity distribution across the PV module. All effects are visible which lead to a local reduction of the charge carrier concentration.
Calibration of the module to determine the I/V characteristic and electrical parameters
Calibration is performed under standard test conditions (STC). The minimum uncertainty of measured power is ±1.1 %. For every module measurement, three consecutive measurements are carried out as hysteresis measurements, where the I-V curve is swept twice for each measurement: from short circuit (Isc) to open circuit (Voc) during the first flash, and from open circuit (Voc) to short circuit (Isc) during the second flash. Due to capacitive effects, which vary between module technologies, a difference (hysteresis) between these two I-V curve sweeps can be observed. Whenever this difference is not negligible, the I-V curve sweeps are divided into multiple sections which are swept during multiple flashes, thus reducing the voltage slew rate and, in consequence, the capacitive effects and the entailed hysteresis between the two I-V curve sweeps.
Calibration certificate and calibration mark on PV module
Signed Dakks calibration certificate with ILAC mark showing calibration object, calibration procedure, measurement conditions, measurement results, measurement uncertainty, reference standards (traceability) and additional information will be issued.
For each calibrated module a calibration mark will be issued close to the name plate. The calibration mark on the module is unique.