Induced thermo-mechanical stress in CPV receivers with cycled high intensity light

Abstract

CPV receivers are made of materials with very different lineal expansion coefficients. Strong variations in DNI due to the passage of clouds can cause sudden temperature changes that creates mechanical stress. For common solder and metal filled polymers the plastic limit could be reached causing substantial fatigue. The best forecast of receiver reliability is therefore achieved by applying an intermittent light source with nominal irradiance level and a number of cycles equal to the expected cloud passages for a given site. The UPM has developed specialized equipment, dubbed the LYSS (Light cYcling Stressing Source), for carrying out such experiments. The small thermal capacity of receivers allows simulating more than 25000 cycles per week. The number of deep transients expected for Madrid in 30 years operation, based on available data, is about 45000. We are currently using the system to cycle a "Ge/Ag Epoxy/aluminum" receiver, which shows no degradation after 20000 cycles. The equipment can cast up to 200 and 70 W/cm2 on 0.1 and 1 cm2 cells, respectively.