IEC TS 60904-1-2-2019 pdf free.Photovoltaic devices – Part 1-2: Measurement of current-voltage characteristics of bifacial photovoltaic(PV) devices.
A solar simulator, as defined in IEC 60904-9,with the additional capability to simultaneo uslyilluminate 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.
5.4Natural sunlight
In addition to the general measurement requirements described in lEC 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.
Care shall be taken to minimize the shadowing if placing sensors to measure the temperatureof bifacial devices under natural sunlight or using double-side illumination. This needs to beconsidered in the measurement uncertainty analysis. Alternatively,contactless (IRT) orequivalent cell temperature calculation can be used as described in lEC TS 62446-3 andIEc 60904-5 respectively.
5.5 Non-irradiated background and background compensation
To measure the I-V characteristics of both front and rear surfaces of bifacial devices,thecontribution from the light incident on the opposite side of the device under test shall beeliminated completely during the measurement by creating a non-irradiating background.Thebackground is considered to be non-irradiating if the irradiance on the surface under test doesnot exceed 3 Wm-2, at any point,on the non-exposed side of the device.
ln order to fulfil this requirement, in the case of PV modules, it is highly recommended to limitthe size of the test area to that of the device under test using baffles as illustrated in Figure 1.Materials with minimized reflection in the wavelength range corresponding to the spectralresponsivity of the test specimen, placed at a suitable distance from its non-exposed side,shall be used to reduce the irradiance level (non-reflective material).
To measure the irradiance on the non-exposed side,choose at least 5 points as shown inFigure 1,with symmetrical distribution,for instance,P1-P3-P5-P7-P9,P2-P4-P5-P6-P8 orP1-P2-P3-P7-P8-P9.
Iln the case of PV bare cells, the use of non-reflective materials to manufacture cell holdersmay be insufficient to reach irradiance values below 3 Wm2. In that case,backgroundcompensation may be performed by extrapolating the short-circuit current as a function of thebackground irradiance.
6Additional I-V characterisations for bifacial devices
6.1 General
The procedure for measurement of the 1-V characteristics of standard (monofacial)Pvdevices is described in lEC 60904-1 and its provisions are also valid for the measurement ofbifacial PV devices except where explicitly amended by this document.The procedure for themeasurement of the 1-V characteristics of a bifacial PV device is based on the same basicprinciples as in lEC 60904-1, but requires some additional considerations and also providessupplementary characteristics specific to bifacial devices.
The measurement conditions for l-V characteristics of bifacial devices require more attentionthan for monofacial devices as the measurement results for bifacial devices are more prone toeffects due to the measurement conditions deviating from the reference conditions. Forinstance,the parasitic reflections from the rear side of the device under test can increasesignificantly the measurement uncertainty.The measurement results should be corrected forthe deviations of the measurement conditions from the reference conditions whereverpossible. The uncertainty of this correction and furthermore the uncertainty arising from corrections which are not possible or have not been made need to be considered in theuncertainty analysis.
The parameters calculated as described below shall adhere to the specified limitations, whichdefine the permissible measurement conditions. The calculated parameters shall also bereported with the measurement results as indicated in Clause 0.
Proper selection of measurement conditions avoids or minimizes the magnitude of thecorrection that shall be applied to the measured characteristics. In any case, a detailedanalysis of measurement uncertainties is required.
6.2Determination of bifacialities
In order to determine the bifacialities of the test specimen, the main l-V characteristics of thefront and the rear sides shall be measured at STC, as schematised in Figure 2 (with G =1 000 wm-2). A non-irradiated background, as described in 5.5,shall be used in order toavoid the illumination of the non-exposed side.IEC TS 60904-1 pdf download.