BS EN 60904-4:2009 pdf download – Photovoltaic devices — Part 3: Measurement principles for terrestrial photovoltaic (PV) solar devices with reference spectral irradiance data
3 Measurement principles In current practice the photovoltaic performance of a solar cell or module is determined by exposing it at a known temperature to stable sunlight, natural or simulated, and measuring its current-voltage (I-V) characteristic curve while measuring the magnitude of both the incident irradiance and the PV device temperature. Detailed I-V curve measurement procedures are included in IEC 60904-1 . The measured performances can then be corrected to Standard Test Conditions (STC) or other desired conditions of irradiance and temperature according to IEC 60891 . The corrected power output at the rated voltage and STC is commonly referred to as the rated power. Incident irradiance can be measured by means of a PV reference device (whose spectral response must be known) or, if measuring under natural sunlight, by means of a thermopile- type irradiance detector (pyranometer). If a PV reference device is used, it shall satisfy the requirements specified in IEC 60904-2.
Temperature determination of the PV device under test shall be made according to IEC 60904-1 . Since a solar cell has a wavelength-dependent response, its performance is significantly affected by the spectral distribution of the incident radiation, which in natural sunlight varies with several factors such as location, weather, time of year, time of day, orientation of the receiving surface, etc., and with a simulator varies with its type and conditions of use. If the irradiance is measured either with a thermopile-type radiometer (that is not spectrally selective) or with a reference solar cell, the spectral irradiance distribution of the incoming light must be known in order to make the necessary corrections to obtain the performance of the PV device under the reference solar spectral distribution defined in this standard as specified in IEC 60904-7.
It is also possible for a user or array designer, using the spectral response of the cells, to compute within a reasonable tolerance the performance of a PV device when exposed to light of any other known spectral irradiance distribution. The methodology for this calculation can be found in IEC 60904-7. 4 Reference solar spectral irradiance distribution The reference solar spectral distribution AM1 .5 is given in Table 1 and Figure 1 . This is a total distribution (direct + diffuse) of sunlight, corresponding to an integrated irradiance of 1 000 W·m –2 incident on a sun-facing plane surface tilted at 37º to the horizontal considering the wavelength-dependent albedo of a light bare soil, under the following atmospheric conditions:
– U.S. Standard Atmosphere with CO 2 concentration increased to current level (370 ppm), a rural aerosol model, and no pollution; – precipitable water: 1 ,41 64 cm;
– ozone content: 0,3438 atm-cm (or 343,8 DU);
– turbidity (aerosol optical depth): 0,084 at 500 nm;
– pressure: 1 01 3,25 hPa (i.e., sea level). Data contained in Table 1 have been generated using the solar spectral model SMARTS, Version 2.9.2. A general description of this model and its suitability to reproduce actual solar spectral irradiance distributions can be found in “Proposed Reference Irradiance Spectra for Solar Energy Systems Testing” by C. A. Gueymard, C. Myers and K. Emery 1 ) , and in the references therein. Table 1 can be obtained using the data contained in Annex A as an input to the model SMARTS Version 2.9.2. The resulting output spectral irradiance values have to be multiplied by a normalization factor (0,9971 ) in order to get an integrated irradiance of 1 000 W·m –2 in the wavelength range 0 to infinity.
At the time of publication of this standard the SMARTS Version 2.9.2 spectral model code is available, free of charge, subject to the author’s license agreement, at A copy of the model, not for distribution purposes, is kept under IEC TC 82 WG 2 control.