Water ingress into photovoltaic devices is known to cause performance loss related to corrosion, mechanical stress and optical transmittance degradation of encapsulating polymer. The useful life of photovoltaic devices can be significantly degraded by moisture. It is estimated that 2% of photovoltaic modules fail within 8 years of operation and that 16% of these failures are related to encapsulant degradation. Due to the long lifetime of modules (approximately 30 years) this problem is difficult to avoid even by using low water diffusivity materials.
There are destructive and non‐destructive ways to measure water content in a photovoltaic device but each has its limitations. Destructive measures are one time measurements in a given device and non‐destructive techniques require moisture indicator compounds in a device that alters the devices actual configuration thereby creating an unknown element in the measurement.
LLNL’s Hydroscanner research team's technology focuses on measuring water ingress in photovoltaic modules. Their non-destructive optical technique picks up water signatures in modules to better inform manufacturers about the health and reliability of the system.
LLNL’s invention for non-destructive evaluation of water ingress in photovoltaic modules uses a non-invasive optical detection technique based on hyperspectral near infrared imaging technology with frequencies tuned to water absorption band. In this way a quantitative 2D image of the water content in a given device can be obtained remotely and repeatedly over time. A key challenge is presented by adapting the technique to modules with complex structure made of multiple layers with various material properties, composition and roughness.
A better understanding of the water diffusion process substantiated by experimental data analysis from deployed modules has the potential to improve both reliability and performance of photovoltaic modules.
Successful implementation of LLNLs technique can lead to a field-deployed rapid screening tool that can measure moisture ingress in hundreds of modules per day under a variety of weathering conditions, identifying items that are more prone to damage and thus allowing for mitigation measures before failure occurs.
LLNL has demonstrated this technique on photovoltaic module coupons. LLNL has filed a U.S. patent application to protect this invention. A LLNL Physicist has been awarded a grant from DOE’s SunShot Initiative to explore spectroscopic technology as a means of detecting moisture buildup in solar photovoltaic (PV) cells. . See related article “LLNL researcher takes aim at solarcell reliability”. The DOE SunShot Initiative is a national effort that drives innovation to make solar energy fully cost-competitive with traditional energy sources before the end of the decade. Through SunShot, the Energy Department supports efforts by private companies, universities and national laboratories to drive down the cost of solar electricity to 6 cents per kilowatt-hour.