Solar Lighting Research and Development

Photo of a sky simulator being used for daylighting research and design at Lawrence Berkeley National Laboratory.

The sky simulator provides a test facility for researchers and building design professionals to conduct model studies on daylighting. The facility is operated collaboratively by LBNL and the University of California Berkeley, Center for Environmental Design Research.

HSL does not waste any portion of the sunlight. It delivers the visible portion of sunlight deep into the building to provide interior lighting, and it uses the remaining "invisible" portion of the sunlight to generate electricity.

Rather than solely converting sunlight into electricity, HSL collectors concentrate sunlight into flexible optical fibers. Sunlight is routed into buildings using the flexible cables. The sunlight is then combined with electric light in specially designed "hybrid" light fixtures.

The natural and electric light sources work in unison to illuminate the inside of buildings. Lighting controls automatically reduce the amount of electric light used in accordance with the amount of sunlight that is 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.

Independent cost and performance models suggest the overall affordability of solar energy could be doubled or tripled using this new hybrid approach. The multidisciplinary R&D effort includes 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 configuration
Improved IR heat removal and management
Improved optical fiber placement and articulation (bundled and pivoted about 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.