Abstract
Considering the high level of energy consumption for lighting in commercial buildings, the use of solar energy for daylighting is appealing more interests at both research and industrial levels. This study presents a novel daylighting system working on the principles of electrowetting. It integrates electrowetting-driven liquid prisms with existing optical fiber daylighting systems, which not only facilitates flexible regulation of the lighting power but also allows for recovery of excess sunlight that is not used for daylighting. An improved design is firstly proposed for the liquid prism to simplify the fabrication processes, increase its reliability, and facilitate easier maintenance. Liquid prisms are then fabricated using the proposed design, and different functionalities are demonstrated. Based on the optimized component design, the illumination performance and energy-saving potential of the proposed daylighting system is quantified using long-term climatological data. Under the climatic conditions of Singapore, a stand-alone system with 1 m2 solar collector is able to provide an annual illumination time of more than 2260 h for a 10 m2 office. The energy consumption for driving the prism is found to be negligible compared with the illumination power provided. Additionally, recovery of the excess energy would further improve the illumination time by up to 95%, while the energy cost is reduced by 20%.
This work is gratefully supported by (1) Ministry of Education (MOE), Singapore (R-265-000-588-114 and R-265-000-597-112), (2) the Water Desalination and Reuse Center (WDRC), King Abdullah University of Science and Technology (KAUST), and (3) Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2019R1F1A1061693).