Remote diagnosis of residential PV systems become important in reducing the Operation & Maintenance cost. In this study, we have developed Operating Performance Index Method (OPI method) which can remotely detect the output power reduction of the PV systems. This method can distinguish between the output reduction due to a failure and a shading by using the configuration data and power output of PV systems, ambient temperature, solar radiation, and wind speed. A failure detection experiment was also conducted by using the 4kW system. This system consists of 24 modules (8 series connected modules in the strings and 3 parallel strings) and has output reduction due to the shading during winter morning and evening. One of the modules in the experimental system was bypassed in September 2016 and output reduction about 7% was successfully detected in October 2016.

An optical fiber lighting system using a Fresnel lens and plastic optical fiber was investigated for sunlight condensation. The coupling efficiency of the Fresnel lens to the optical fiber was evaluated in experiments and calculations. As a result, it has been found that the chromatic aberration of the lens does not cause a significant reduction in the efficiency and the unique groove structure of the Fresnel lens requires though evaluation in the selection process.A coupling efficiency of about 50% was obtained by using a large diameter Fresnel lens of φ 300 mm.