In-Situ Measurement of Crystalline Silicon Modules Undergoing Potential-Induced Degradation in Damp Heat Stress Testing for Estimation of Low-Light Power Performance

Abstract

The extent of potential-induced degradation of crystalline silicon modules in an environmental chamber is estimated using in-situ dark I-V measurements and applying superposition analysis. The dark I-V curves are shown to correctly give the module power performance at 200 W/m 2 , 600 W/m 2 , and 1,000 W/m 2 irradiance conditions, as verified with a solar simulator. The onset of degradation measured in low light in relation to that under one sun irradiance can be clearly seen in the module design examined; the time to 5% relative degradation measured in low light (200 W/m 2) was 28% less than that in full sun (1,000 W/m 2 irradiance). The power of modules undergoing potential-induced degradation can therefore be characterized in the chamber, facilitating statistical analyses and lifetime forecasting.

Fault identification in crystalline silicon PV modules by complementary analysis of the light and dark current–voltage characteristics

“…Modules P1, P3, and P4 were stressed at 60 °C/85% relative humidity (RH) and −1000 V bias, during which they exhibited medium to high PID sensitivity. The fast degradation rate of these modules is readily evident from the STC P max degradation curves shown in Figure , measured in situ according to the procedure described in . In contrast, module P2, which was designed by the manufacturer to be PID‐resistant, degraded much slower, as can be observed from Figure .…”

Temperature‐dependency analysis and correction methods of in situ power‐loss estimation for crystalline silicon modules undergoing potential‐induced degradation stress testing

“…The current work is based on such an in situ module degradation characterization method, first proposed in [3], that can estimate the STC P max degradation of modules, from the 25°C dark I-V characteristic of the PV modules, taken during the PID stress test. The method involves periodic measurement of the 25°C dark I-V characteristic of the PV modules, while in the chamber, followed by the superposition of the dark I-V curves to light conditions, using the short-circuit current (I sc ) of each module, measured at STC (or other irradiance conditions of interest such as low in light [3]), before and after the PID stress test.…”

“…The current work is based on such an in situ module degradation characterization method, first proposed in [3], that can estimate the STC P max degradation of modules, from the 25°C dark I-V characteristic of the PV modules, taken during the PID stress test. The method involves periodic measurement of the 25°C dark I-V characteristic of the PV modules, while in the chamber, followed by the superposition of the dark I-V curves to light conditions, using the short-circuit current (I sc ) of each module, measured at STC (or other irradiance conditions of interest such as low in light [3]), before and after the PID stress test. Because the photocurrent (at I sc ) is only weakly influenced by PID, as previously observed for crystalline modules [3][4][5], the P max degradation estimated by the superposition of the dark I-V curves corresponds very well with the degradation measured using a flash tester, for a wide range of irradiance conditions [3].…”

“…The method involves periodic measurement of the 25°C dark I-V characteristic of the PV modules, while in the chamber, followed by the superposition of the dark I-V curves to light conditions, using the short-circuit current (I sc ) of each module, measured at STC (or other irradiance conditions of interest such as low in light [3]), before and after the PID stress test. Because the photocurrent (at I sc ) is only weakly influenced by PID, as previously observed for crystalline modules [3][4][5], the P max degradation estimated by the superposition of the dark I-V curves corresponds very well with the degradation measured using a flash tester, for a wide range of irradiance conditions [3]. This method so far has been limited to dark I-V curves captured at 25°C, requiring interruption of the stress test, ramping down the temperature of the PV module to 25°C for dark I-V characterization, and then ramping back up again to the elevated temperature for resuming the stress test.…”

“…The in situ module degradation characterization method [3], assumes the superposition principle (or "shifting approximation"), which has been shown to work well for most crystalline pn single junctions [6,7]; however, there are some limitations that must be considered when applying this method. One of the most common cases mentioned in the literature, for which the superposition principle breaks down, is for solar cells exhibiting a significant series resistance (R s > 10 Ωcm 2 ) [7][8][9][10], for which the I sc does not match the light-generated current anymore.…”