Estimation of Energy and Analysis of Time-Related Degradation Using Contour Map of Photovoltaic Module Performance

Abstract

The output energies of multicrystalline and amorphous silicon/microcrystalline silicon photovoltaic (PV) modules were estimated using the performance contour map as a function of module temperature and solar spectral irradiance distribution taking into consideration time-related degradation. Generally, the performance of outdoor PV modules degrades yearly. When degradation is not considered, the error of the estimated output energy tends to increase yearly. To estimate the precise output energy, the degradation rates of the performance of the PV modules was considered. The yearly degradation rates were estimated using the measurement data from the years 2005–2009 by linear approximation, and the performance contour map in 2010 was estimated. The estimated contour maps were similar to the actual ones, and the errors between the estimated and actual maps were decreased. The error between the estimated and actual energies was within 2.5% in the PV modules. The results indicated that the method of using the contour map taking into account the yearly degradation is useful for estimating the output energy of the PV modules after outdoor exposure.