Acetic acid formed via the hydrolysis of ethylene vinyl acetate (EVA) as an encapsulant in photovoltaic (PV) modules causes a decrease in the conversion efficiency of such modules by grid corrosion. Here, a nondestructive and simple optical method for evaluating the condition of PV modules is proposed. This method uses a dual-wavelength pH-sensitive fluorescent dye to detect acetic acid in PV modules using a change in pH. The change in pH induced by the formation of acetic acid is detected by the change in the ratio of the fluorescent intensities of two peaks of the dye. A pH-sensitive fluorescent dye showed sensitivity for small amounts of acetic acid such as that produced from EVA. Furthermore, a membrane filter dyed with a pH-sensitive fluorescent dye was confirmed to detect acetic acid in aged EVA after a damp-heat test (85 °C, 85%) for 5000 h in PV modules.

A novel, nondestructive low-cost detection method for acetic acid distribution in a photovoltaic (PV) module during the damp heat (DH) test based on reflectance changes of tin film sensors is proposed and demonstrated. The sensor consists of a tin film evaporated on a glass substrate. Nineteen sensors and one gold film are laminated in the PV module, and the DH test was performed at 85°C and 85% relative humidity for 7203 h. The time range of measurement can be controlled between 2000 to 6000 h by adjusting the tin film initial thickness from 70 to 160 nm.