Initial Results From an Experimental Hybrid Solar Lighting System in a Commercial Building and Overview of Related Value Propositions

This paper describes preliminary results from research on a new hybrid solar lighting (HSL) system being developed to reduce electric lighting in commercial office buildings. A physical description of HSL system components along with preliminary results from an experimental system deployed in a commercial building in Knoxville, TN are provided. Results from a systems-level, chromaticity model are compared with experimental data. A total lumen distribution efficiency of over 50% was recorded for the initial prototype having optical fibers an average of 6 m (19.5 ft) in length. The total electrical power displacement of the 1 m² HSL proof-of-concept prototype is estimated to be between 522–2350 watts per 1000 W/m² of incident solar radiation on the collector depending on the type of electric lights being used in conjunction with the solar lighting system. By adding the reductions in heat gain associated with reduced electric lamp use and predicted performance improvements achieved by a system redesign, the electrical power displaced in a commercial prototype could rise to between 702–3160 W (peak)/m² of collected sunlight not including any additional electrical power that can be generated using the otherwise wasted IR energy. The color temperature of the distributed sunlight emerging from the optical fibers is approximately 5100°K and the chromaticity values in uniform color space (u′v′) are approximately (.2010, .4977). These values match well with modeled results and will vary slightly depending on the day, time, atmospheric conditions, and system configuration. The paper concludes with a discussion of new value propositions that HSL provides architects, energy providers, building owners, and occupants and briefly outlines anticipated disadvantages.