Evaluation of a Passive Optical Fiber Daylighting System for Plant Growth

Abstract

Current farming practices deplete resources and energy including water, soil, and electricity. Alternative farming methods such as indoor agriculture are possible solutions, however, current methods utilize a considerable amount of electricity to provide plants with artificial light. Optical fiber daylighting systems (OFDs) offer a way to direct sunlight indoors over long distances and can therefore reduce electricity usage. Currently, the market mostly includes active OFDs that use a motor and sun-tracking mechanism. This can be complicated and expensive to develop and operate. Therefore, our research focuses on developing and optimizing a passive OFD system. Passive OFDs are static structures that use their geometry and the laws of optics to redirect light. Optical simulation software, CAD software, additive manufacturing, and waterjet tools were used to develop an optimal passive OFD prototype for data collection. Vegetative plant growth requires a photosynthetic photon flux density (PPFD) of 250 and higher. Our prototype design provided a photoperiod of 210 minutes at a high (above 250 PPFD) level, 179 minutes at a medium (above 170 and less than 250 PPFD) level, and 175 minutes at a low (below 170 PPFD) level. This research supports the development and implementation of an effective passive OFD system for indoor farming operations at a significantly reduced cost, with increased feasibility in a more environmentally friendly approach.