Improved modeling of failure rate of photovoltaic modules due to operational environment

Reliability characteristics of PV modules, which are always installed outdoor, can be influenced by environmental conditions such as temperature, wind speed, snow, long term degradation, spectral issues, irradiance, air gap between modules, dust, rainfall, corrosion, water vapour intrusion, delamination of encapsulant materials, Thermal expansion, ultraviolet radiation, humidity, mechanical load, salt mist, partial shading, heat island impact, global climate change, summer-winter climate change, Staebler- Wronski effect, Clearness of sky, urban heat island (UHI) effect, ageing and component derating etc. But the conventional reliability model deals with a time interval and is a measure of the probability for failure-free operation during the given interval, i.e., it is a measure of success for a failure free operation. It is often expressed as R(t) = exp(−t/MTBF) = exp(−λt), where MTBF is the Mean Time Between Failure and λ is the failure rate, which is the reciprocal of MTBF. In this paper an attempt is made to modify the time equation of reliability with incorporating environmental impacts like temperature, wind and snow and remodel the equation with various statistical distributions. This will lead to more accurate prediction of the reliability and life time of photovoltaic system and components.