The California Lighting Technology Center (CLTC) is pleased to announce the release of a new research report, Performance Assessment of Integrated Core Daylighting Technology, which evaluates the performance of a solar-tracking fiber optic daylighting system. This solar-tracking fiber optic daylighting system captures sunlight using roof-mounted collectors that follow the sun’s path and transmit the light through fiber optic cables to interior luminaire, where it is integrated with commercially available LED lighting to supplement illumination when daylight levels are insufficient, e.g., overcast days and evening hours. By dynamically balancing natural daylight and electric light, this hybrid solar-tracking fiber optic lighting system (STF) maintains consistent light levels, color quality, and distribution, regardless of seasonal or weather conditions, while also maximizing energy efficiency. 

This solar-tracking fiber optic lighting system is particularly well-suited for spaces where bringing in daylight through traditional methods, such as windows or skylights, is impractical. Additionally, the fixture produces a light cone angle between 41° and 46°, which is commonly used in office area lighting. Here are more details about the STF system: 

Light Output: The STF system consists of 40 fiber optic cables, where each cable can deliver up to 729 lumens, resulting in a maximum total light output of approximately 28,000 lumens, depending on the cable length and external conditions. 

Spectral Quality: The fiber optic cables are manufactured from high-quality glass, minimizing spectral shift and maintaining the natural quality of sunlight, delivering light with an average color rendering index (CRI) of 85. 

System Efficacy: The STF system uses a motorized base, electronic control system, and central photosensor to track the sun’s position using geographic and time-based data while optimizing alignment, ensuring that the maximum amount of sunlight is captured. This hybrid lighting system achieved energy savings of up to 40% compared to installed LED baselines. 

While this hybrid STF lighting system demonstrated strong technical performance (maintaining acceptable illumination levels, color quality, and occupant comfort while reducing electricity consumption far below Title 24 allowances), its cost effectiveness remains the primary barrier to deployment. Current hardware costs, which are driven primarily by fiber and collector fabrication, result in payback periods that exceed hundreds or even thousands of years! 

To move the technology toward viability, further development is needed in both hardware and controls. On the hardware level, enhancing collector uniformity, fixture optics, and dust protection can improve light output and long-term reliability. On the controls side, manufacturers should prioritize fast-response daylighting algorithms with narrow deadbands to suppress perceivable fluctuations, ideally integrating fiber-specific daylight signals directly into the control loop. Additionally, field demonstrations in occupied buildings should be expanded to quantify real-world maintenance intervals, validate occupant comfort across seasons, and evaluate performance across varying fiber run-lengths! 

Learn more about the development, installation, and performance of this hybrid lighting technology in the Final Report.