Reported November 2006

BACKGROUND: Engineers at Oak Ridge National Laboratory in Tennessee have developed a new hybrid solar lighting system that literally pipes sunlight into a room. It brings natural light inside through optical fibers and distributes it through light fixtures that contain electric lamps. The solar and electrical systems work in tandem, dimming the electric lights when the sunlight is bright and turning them up as clouds move in or as the sun sets.

HOW IT WORKS: The system uses a roof-mounted collector and small fiber optics to transfer sunlight to top-floor hybrid fixtures that contain electric lamps. The result: less energy is used. The system not only uses less lighting, but also less cooling, since it blocks ultraviolet rays and infrared heat. Preliminary test results indicate that companies installing such a system would also see increased wellness and productivity among their employees.

SAD FACTS: Human beings require a certain amount of natural sunlight. SAD (Seasonal Affective Disorder) is a type of winter depression that affects an estimated half a million people every winter. It is caused by a biochemical imbalance in the hypothalamus due to the shortening of daylight hours and the lack of sunlight in winter. Light therapy has been shown to be effective in up to 85 percent of diagnosed cases. The treatment calls for exposure, for up to four hours per day (average one to two hours) to very bright light, at least 10 times the intensity of ordinary domestic lighting.

ABOUT SOLAR CELLS: The solar cells on calculators and satellites are photovoltaic cells or modules: groups of cells electrically connected and packaged together. Photovoltaics convert sunlight directly into electricity. Photovoltaic (PV) cells are made of semiconductor materials like silicon. When light strikes the cell, a certain portion of it is absorbed by the semiconductor material. The energy of the absorbed light knocks electrons loose, allowing them to flow freely. PV cells also all have one or more electric fields that act to force electrons freed by light absorption to flow in a certain direction. This flow of electrons is a current, and by placing metal contacts on the top and bottom of the PV cell, we can draw that current off to use externally. For example, the current can power a calculator.

If you would like more information, please contact:

Duncan Earl
Optical/Electrical Engineer
Oak Ridge National Laboratories
Oak Ridge, Tennessee
(865) 675-7827
earldd@ornl.gov

Melissa Lapsa
Sunlight Direct
(865) 483-6624

FACTOID...

About 24 percent of the energy used by commercial buildings is due to artificial lighting. As many as 1 million hybrid solar lighting systems could be in use by 2020, with savings of billions of dollars annually.

ON THE WEB...

Hybrid Solar Lighting From Sunlight Direct

Hybrid Solar Lighting at the Oak Ridge National Laboratory