PD IEC TS 60904-1-2:2019 pdf free.Photovoltaic devices Part 1-2: Measurement of current-voltage characteristics of bifacial photovoltaic (PV) devices.
The final performance of bifacial PV devices in a power plant depends not only on the spatialdistribution of the irradiance incident onto the front surface, but additionally on that incidentonto rear surface of the device,which is strongly affected by site-specific conditions, such asalbedo, reflective surface size, the racking system, the device’s elevation and its tilt angle.Due to these dependences and in order to obtain comparable measurement results，I-Vcharacterisation is extended to quantify the bifaciality of the device and the rear irradiancedriven power gain yield it can yield.Bifaciality is an intrinsic property of the device,unlike thesite-specific conditions such as albedo. The measurement conditions for bifacial devicesshould strive to generate extra photocurrent proportional to their bifaciality. Iln general, thiscan be achieved with a test spectrum close to the reference spectrum such as provided bynatural sunlight under suitable conditions or with a solar simulator whose irradiance level is
adjustable.However,measurement conditions will never be perfect and will deviate from thereference conditions. This document sets limits on the permissible deviations for obtainingvalid measurements. Smaller deviations are preferable, but may not be achievable in allcases. In any case，the deviations of the measurement conditions from the referenceconditions shall be accounted for in the analysis of measurement uncertainty.
In addition to the apparatus requirements described in IEC 60904-1, one of the equipmentsets described in 5.2，5.3 and 5.4 and that described in 5.5 is necessary for thecharacterisation of bifacial devices.
A solar simulator, as defined in lEC 60904-9, with adjustable irradiance level shall be used forthe I-V characterisation of bifacial devices. Simulators shall be able to provide irradiancelevels above 1 000 Wm-2(typically up to 1 200 Wm2). The simulator’s non-uniformity ofirradiance shall be below 5 % and shall remain below this value at irradiance levels used forthe characterisation of bifacial devices. The non-uniformity of irradiance，the spectraldistribution and the temporal instabilities of irradiance shall be measured at the irradiancelevels used for the characterisation of bifacial devices and those values used for corrections(such as spectral mismatch correction) and uncertainty evaluation.
For irradiances used above STC (>1000 wm-2), the spatial uniformity, spectral distributionand temporal instability at 1 100 Wm-2 and 1 200 Wm-2 shall be measured.
A solar simulator, as defined in IEC 60904-9,with the additional capability to simultaneouslyilluminate the bifacial device on both sides shall be used.Such simulators shall be able toprovide irradiance at different levels on both sides. The non-uniformity of irradiance，thespectral distribution and the temporal instabilities of irradiance shall be measured on bothsides when the test area is simultaneously illuminated on both sides. The non-uniformity ofirradiance shall be below 5 % on both sides, at the irradiance levels used for thecharacterisation of bifacial devices and those values used for corrections (such as spectralmismatch correction) and uncertainty evaluation.
ln addition to the general measurement requirements described in IEC 60904-1， at least2 additional PV reference devices, as described in lEC 60904-2,are required to measure theirradiance level on the rear side and the rear-side irradiance non-uniformity. Their spectralresponsivity should be as close as possible to the one of the device under test.PD IEC TS 60904-1-2 pdf download.