Throughout the 1900s, use of the sun as a source of energy has evolved considerably. Early in the century, the sun, streaming in through windows and other aperatures, was the primary source of interior light for buildings during the day. Eventually, however, the cost, convenience, and performance of electric lamps improved and the sun was displaced as our primary method of lighting building interiors.

Attempts to use sunlight directly for interior lighting via lens collectors, reflective light-pipes, and fiber-optic bundles were the next step.

The most recent technology, Hybrid Solar Lighting, collects sunlight and routs it through optical fibers into buildings where it is combined with electric light in "hybrid" light fixtures. Sensors keep the room at a steady lighting level by adjusting the electric lights based on the sunlight available. If a cloud passes over the sun, diminishing the sunlight coming in over the fiber optics, then the power to electic lights is increased. When the sun shines fully again, the electric power is decreased.

This new generation of solar lighting combines both electric and solar power. Hybrid solar lighting pipes sunlight directly to the light fixture and no energy conversions are necessary, therefore the process is much more efficient. It is currently being developed and tested by Oak Ridge National Laboratory in collaboration with the Department of Energy and several industry partners.

Solar Lighting

The Solar Energy Research Facility (SERF) at the Natural Resource Ecology Laboratory (NREL) uses a light shelf on the south side for daylighting. It also has a small square windows on the east and west to minimize glare.

About Fiber Optics

Fiber optics is the branch of applied science and engineering concerned with optical fibers.

An optical fiber is a glass or plastic fiber, like a long thin cable or thread, designed to guide light along its length by total internal reflection. Because of the flexible nature of the materials optical fibers are made of, they can bend around corners and bring sunlight into areas where there are no windows!