In order to evaluate the reliability and performances of photovoltaic
(PV) modules, it is of importance to reveal the characteristics of PV
modules in actual use conditions. Outdoor exposure tests of PV modules
have been conducted at some sites in Japan and Australia. The purpose
of these tests are to evaluate the effects ok the starting month of e
xposure, long term degradation, and heat insulator on the performances
of the module efficiencies. Some important results were obtained, for
example, the efficiencies of a-Si modules after one year of exposure
showed similar tendencies regardless of the starting month of the year
. The efficiencies of a-Si modules showed no long term (for six years)
degradation. Heat insulator had the effects on the increase of the mo
dule temperature and the corrected (by irradiance and temperature) out
put power. For the outdoor exposure tests with much more severe condit
ions, the climate conditions of Oman were examined and found to be a s
uitable place due to its high solar irradiance, temperature, and humid
ity. (C) 1998 Elsevier Science Ltd. All rights reserved.