Three years performance and reliability of a 15 kWp amorphous silicon photovoltaic system

A 15 kWp grid-connected photovoltaic system was installed in August 1988 at one of Florida Power Corporation´s substations near Orlando, Florida. The photovoltaic array is made of 640 G4000 modules. The system´s performance has been monitored for three years of operation, and periodic diagnostic tests have been conducted to evaluate the subsystem reliability. During the three-year period, the power output of the photovoltaic array has degraded by 25% of its original value and the array peak power efficiency is 4.0% as of August 1991. Due to the annealing effects and more favorable spectral distribution of solar irradiance in summer, the array efficiency is about 10% relatively higher in summer time than in winter period (4.4% versus 3.9%). A significant corrosion build-up on 31 out of total 640 photovoltaic modules has been observed. Relatively high leakage currents of the array, particularly under wet conditions, have also been detected