BAPV modules with different air gaps: Effect of temperature on relative energy yield and lifetime

Temperatures experienced by photovoltaic modules operating in the field can be much higher than the Standard Test Conditions (STC) temperature of 25°C for which the nameplate rating is given. The module performance decreases as the operating temperature increases. The lifetime of PV modules is compromised by higher operating temperatures as well. A higher operating temperature increases the rate of reaction for several degradation mechanisms of photovoltaic modules. The air gaps between module and rooftop of Building Applied Photovoltaic (BAPV) modules can have a direct impact on cell operating temperature. This paper presents and analyzes the effect of air gap and corresponding temperature on the relative energy yield and lifetime of crystalline silicon BAPV modules based on 1 year of field data collected between March 2009 and March 2010 at the Arizona State University Photovoltaic Reliability Laboratory (ASU-PRL). The collected temperature data is analyzed to report estimated relative energy yield, environmental and economic impact, and lifetime values for each of the different air gap configurations. The results provide strong evidence that air gap space is an important aspect of BAPV performance and lifetime, especially in desert climatic conditions.