BS EN 60904-1:2006 – Photovoltaic devices — Part 1: Measurement of photovoltaic current-voltage characteristics
5.1 Mount the reference device as near as possible to and co-planar with the specimen on the two-axis tracker. Both shall be normal to the direct solar beam within ±5°. Connect to the necessary instrumentation.
5.2 If the specimen and reference device are equipped with temperature controls, set the controls at the desired level. If temperature controls are not used:
5.2.1 shade the specimen and the reference device from the sun and wind until their temperature is uniform within ±2 °C of the ambient air temperature, or
5.2.2 allow the test specimen to equilibrate to its stabilized temperature, or
5.2.3 pre-condition the test specimen to a point below the target temperature and then let the module warm up naturally. NOTE There may be differences between average cell temperature and average back temperature during warming up.
5.3 Record the current-voltage characteristic and temperature of the specimen concurrently with recording the output and temperature (if required) of the reference device at the desired temperatures. If necessary, make the measurements immediately after removing the shade. NOTE In most cases the thermal inertia of the specimen and the reference device will limit the temperature rise during the first few seconds to less than 2 °C. Their temperatures will remain reasonably uniform.
5.4 Ensure that the specimen and reference device temperature are stable and remain constant within ±1 °C and that the irradiance as measured by the reference device remains constant within ±1 % (fluctuations caused by clouds, haze, or smoke) during the recording period for each data set.
5.5 If a pyranometer or an unmatched reference device is used as reference device, perform a simultaneous measurement of spectral irradiance using the spectroradio- meter. Calculate the effective irradiance for the specimen under the AM1 ,5 spectrum (see IEC 60904-3) using its spectral response data (apply IEC 60904-7). NOTE When no spectral irradiance data are available the match of the reference device to the specimen and the air mass conditions should be checked carefully. Measurement should be performed on a clear sunny day (no observable clouds around the sun, diffuse contents of solar irradiance not higher than 30 %).
5.6 Correct the measured current-voltage characteristic to the desired irradiance and temperature conditions in accordance with IEC 60891 (for linear devices). For non- linear devices refer to IEC 60904-1 0 for guidance in determining over what range the device can be considered to be linear.
6 Measurement in steady-state simulated sunlight Steady-state sunlight simulation for photovoltaic performance measurements shall meet the requirements of IEC 60904-9. The uniformity of light distribution in the test area shall be known and periodically checked. The accuracy of the measurement shall be verified periodically by successive measurements at the same test condition. Three methods for calibration can be applied. If the device under test is the same size as the reference device, use method A. If the device under test is larger than the reference device, use method B. If the device under test is smaller than the reference device, use method C. NOTE Method A is the preferred method as it minimises the effects of non-uniformity of irradiance and scale factors in the electronics.
BS EN 60904-1:2006 – Photovoltaic devices — Part 1: Measurement of photovoltaic current-voltage characteristics