Outdoor exposure tests of photovoltaic modules in Japan and overseas

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 exposure, 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 module temperature and the corrected (by irradiance and temperature) output power. For the outdoor exposure tests with much more severe conditions, the climate conditions of Oman were examined and found to be a suitable place due to its high solar irradiance, temperature, and humidity. (C) 1998 Elsevier Science Ltd. All rights reserved.