Study on thermal protection and temperature of PMMA plastic optical fiber for concentrated sunlight transmission in daylighting

Abstract

Daylighting system by concentrating and transmitting sunlight through optical fiber is an emerging technology of direct utilization of solar energy. In this work, a sunlight concentrating and transmitting system via plastic optical fibers was developed and investigated. This study addressed the overheating problem of plastic optical fibers under highly concentrated light irradiation. Polymethylmethacrylate (PMMA) plastic fibers have a strong absorption in the infrared band. The PMMA plastic fiber generates serious heat under highly concentrated light transmission, which leads to its overheating and burning. In this study, an incident light filtering method based on the combination of infrared filter and insulating glass is proposed. By filtering out the infrared band light with significant thermal effect, the PMMA plastic optical fibers are guaranteed to be within a safe working temperature range. Experiments demonstrated that the developed filter system can ensure the safe operation of PMMA plastic optical fibers at the concentration level of about 4300 suns. This shows that it is feasible to use low-cost plastic optical fiber for highly concentrated daylighting system.