Solar Lighting

Solar powered lights; powered by the sun!

Research at the Oak Ridge National Laboratory (ORNL) is leading to new, highly energy-efficient ways of lighting buildings using the power of sunlight. This new technology, called Hybrid Solar Lighting, (HSL) uses sunlight to simultaneously light interior spaces and generate electricity. Hybrid solar lighting makes better use of the sun in its natural form and focuses on the energy consumed by electric lights; the largest consumer of electricity in commercial buildings. Electric lighting represents more than a third of the electricity consumed for commercial use in the United States. HSL uses a special collector to focus natural, full-spectrum sunlight into optical cables while simultaneously converting otherwise wasted infrared energy into electricity. The optical cables then deliver the full-spectrum sunlight to the light fixtures throughout a building. HSL converts sunlight to electricity much more efficiently than conventional solar technologies. In solar lighting and power systems, roof-mounted concentrators collect sunlight and distribute it through the optical fibers and to hybrid lighting fixtures inside the building. A HSL system can produce electricity for supplemental lighting too.
Solar Lighting in Use
# There are currently two proposed applications for hybrid solar lighting systems.Hybrid lighting systems are being developed for use in commercial buildings to displace electric lighting, which consumes a large portion of electricity in commercial buildings.
# Researchers are investigating the use of HSL as a key component in new hybrid solar photobioreactors that sequester carbon through enhanced photosynthetic-based bio-processing at power plants.

Solar Lighting Research and Development
# HSL doesn’t waste any of the sunlight it collects. It collects the visible portion of sunlight and delivers into the building providing interior lighting, then the remaining (invisible) part of the sunlight is used to generate electricity. Besides converting sunlight into electricity, HSL collectors concentrate sunlight into flexible optical fibers. Sunlight is then routed into buildings using these flexible cables. The sunlight is then combined with electric light in specially designed “hybrid” light fixtures. The natural and electric light sources work together to illuminate the inside of a building. Lighting controls automatically reduce the amount of electric light used in accordance with the amount of sunlight available. In addition to being more efficient than commercially available solar options, hybrid solar lighting brings highly preferred, full-spectrum sunlight inside buildings. Full-spectrum sunlight is preferred over incandescent or fluorescent light because it can help realize performance and health benefits for people of all ages The remaining “invisible” energy in the sunlight, mostly infrared radiation, is directed to a concentrating thermo-photovoltaic cell that very efficiently converts infrared radiation into electricity. The resulting electric power can be directed to other uses in the building. The overall affordability of solar energy could be doubled or tripled using this new hybrid approach. There is a multidisciplinary R&D effort under way consisting of several industrial and university partners. Compared to earlier light collection systems for solar lighting applications in buildings and photobioreactors, the proposed hybrid collector design provides several advantages: Fewer, easily assembled, system components integrated into a smaller, less costly, and more compact design configurations
# Improved IR heat removal and management
# Improved optical fiber placement and articulation (bundled and pivoted on a radial axis)
# A longer optical path for light and lower entrance angles for visible light entering large-core optical fibers. This results in much lower overall transmission losses in the accompanying light delivery system
# Centrally-concentrated IR radiation, allowing for convenient implementation of IR-TPVs.

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