Background

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.

Description

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.

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Advantages

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.

Potential Applications

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.