Failure and degradation modes and rates of PV modules in a hot-dry climate: Results after 16 years of field exposure

Abstract

This study evaluates the frameless modules of same type (model B) in two 16-year old photovoltaic power (PV) systems to ascertain degradation rates, reliability failure modes and safety failure modes which occur in a hot-dry climate. Each system is composed of 1512 modules. The average degradation rate is determined to be 0.85%/year for the best modules and 1.1%/year for all the modules (excluding the safety failed modules). Primary safety failure mode is the backsheet delamination though it is small (less than 1.7%). Primary degradation mode and reliability failure mode may potentially be attributed to encapsulant browning leading to transmittance/current loss and thermo-mechanical solder bond fatigue (cell-ribbon and ribbon-ribbon) leading to series resistance increase. Under the typical 20/20 warranty terms, 0.5-1.7% of the modules qualify for the safety returns, 73-76% of the modules qualify for the warranty claims and 24-26% of the modules are meeting the warranty terms.