Decline of the Carrisa Plains PV power plant: the impact of concentrating sunlight on flat plates

The Carrisa Plains photovoltaic (PV) power plant located in central California has steadily degraded in performance since 1986 at a rate of approximately 10% per year. Originally rated at 5.2 MW, the plant routinely produced less than 3 MW as of 1990. The plant is composed of two-axis trackers with single-crystalline flat plate modules, and over 90% of the trackers have V-trough mirrors to concentrate sunlight. This low-concentration design has caused an accelerated browning of the modules and is the cause of the plant´s decline. Electrical testing was performed to investigate the ramifications of module browning. The results indicate that ethylene-vinyl acetate (EVA) browning is an important concern for the PV industry and that low-concentration designs should not be used for one-sun flat plate modules until the issue has been resolved