Description of degradation of output performance for photovoltaic modules by multiple regression analysis based on environmental factors

Abstract

Output performances of multi-crystalline Si (mc-Si), single-crystalline Si (sc-Si), hydrogenated amorphous Si (a-Si), and a-Si/microcrystalline-Si tandem photovoltaic (PV) modules are described using multiple regression analysis based on environmental factors (irradiation intensity on tilted surface (IrrT), angle of incidence (AOI), average photon energy (APE), and module temperature (Tmod)). Since performances of PV modules are normally degraded with time-passing, a term of time (day_number) is added for the description of estimated output energy for high accuracy as compared with actual output energy, where collection periods of the environmental factors for the estimated output energy and actual energy are the same data period (interpolation). It is disclosed that for high accurate output description a term of time is vital for sc-Si, a-Si, and tandem PV modules with time-related degradation, while it is not for mc-Si PV module with small time-related degradation. In addition, the multiple regression analysis using the environmental factors and day_number is successfully utilized based on extending known sequence of these values in years 2004–2006 to describe output energy under their beyond data period of time in years 2007–2009 (extrapolation). This is practical for prediction of energy production in lifetime of PV modules (20–25 years) under consideration of their degradation.