ABSTRACT
Outdoor exposure tests of photovoltaic (PV) modules have been conducted in Japan, Australia, and Oman to understand the long term stability of PV modules and the effects of climate conditions on efficiency. From the test in Japan, it was found that the efficiencies of crystal silicon (c-Si)and amorphous silicon (a-Si) module showed little degradation tendencies even after about 9 years of exposure. The tests in Australia showed that a-Si module efficiencies were strongly influenced by climate conditions especially by temperature. The efficiencies showed very slight degradation tendencies (2-3% per year) for about two years of exposure. The spectral distribution of solar irradiance were measured and the results are discussed in terms of short circuit current of a-Si. The test in Oman for a-Si related modules (single type of a-Si, two layers type of aSi/a-SiGe, and three layers type of a-Si/a-Si/a-SiGe) showed initial degradation of efficiency which were a little different among the types of a-Si modules.
