Significance and Use
It is the intent of these procedures to provide recognized methods for testing and reporting the electrical performance of photovoltaic modules and arrays.
The test results may be used for comparison of different modules or arrays among a group of similar items that might be encountered in testing a group of modules or arrays from a single source. They also may be used to compare diverse designs, such as products from different manufacturers. Repeated measurements of the same module or array may be used for the study of changes in device performance.
Measurements may be made over a range of test conditions. The measurement data are numerically translated from the test conditions to standard RC, to nominal operating conditions, or to optional user-specified reporting conditions. Recommended RC are defined in Table 1.
If the test conditions are such that the device temperature is within ±2°C of the RC temperature and the total irradiance is within ±5 % of the RC irradiance, the numerical translation consists of a correction to the measured device current based on the total irradiance during the I-V measurement.
If the provision in 5.3.1 is not met, performance at RC is obtained from four separate I-V measurements at temperature and irradiance conditions that bracket the desired RC using a bilinear interpolation method.
There are a variety of methods that may be used to bracket the temperature and irradiance. One method involves cooling the module under test below the reference temperature and making repeated measurements of the I-V characteristics as the module warms up. The irradiance of pulsed light sources may be adjusted by using neutral density mesh filters of varying transmittance. If the distance between the simulator and the test plane can be varied then this adjustment can be used to change the irradiance. In natural sunlight, the irradiance will change with the time of day or if the solar incidence angle is adjusted.
These test methods are based on two requirements.
First, the reference cell (or module, see 1.1.1 and 4.3.4) is selected so that its spectral response is considered to be close to the module or array to be tested.
Second, the spectral response of a representative cell and the spectral distribution of the irradiance source must be known. The calibration constant of the reference cell is then corrected to account for the difference between the actual and the reference spectral irradiance distributions using the spectral mismatch parameter, which is defined in Test Method E 973
A reference cell made and calibrated as described in 4.3 will indicate the total irradiance incident on a module or array whose spectral response is close to that of the reference cell.
With the performance data determined in accordance with these test methods, it becomes possible to predict module or array performance from measurements under any test light source in terms of any reference spectral irradiance distribution.
The reference conditions of 5.3.1 must be met if the measured I-V curve exhibits “kinks” or multiple inflection points.
|Total Irradiance, Wm−2||Spectral Irradiance||Device Temperature,|
|Standard reporting conditions||1000||G 173||25|
|Nominal operating conditions||800||...||NOCT|
1.1 These test methods cover the electrical performance of photovoltaic modules and arrays under natural or simulated sunlight using a calibrated reference cell.
1.1.1 These test methods allow a reference module to be used instead of a reference cell provided the reference module has been calibrated using these test methods against a calibrated reference cell.
1.2 Measurements under a variety of conditions are allowed; results are reported under a select set of reporting conditions (RC) to facilitate comparison of results.
1.3 These test methods apply only to nonconcentrator terrestrial modules and arrays.
1.4 The performance parameters determined by these test methods apply only at the time of the test, and imply no past or future performance level.
1.5 These test methods apply to photovoltaic modules and arrays that do not contain series-connected photovoltaic multijunction devices; such module and arrays should be tested according to Test Methods E 2236
1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.