Fiber Optics to Bring Sunlight into Buildings


This article was published by Newsletter, issue #9, 2005-07-10.

The conventional use of sunlight to illuminate the insides of our buildings, involves covering a building's exterior with solar panels, which capture the sun's radiation and convert it into electricity, which is then transmitted inside the building to conventional fluorescent and incandescent bulbs. At first glance, this approach seems like a considerable improvement over the more wasteful situation nowadays of letting the sun's rays bounce off the building unused, and pulling power from an electrical grid, which probably generated that electricity by burning coal, damning rivers, or running a nuclear power plant. Admittedly, the conventional solar panel approach is a huge improvement.

But that can't possibly be the best that we can do, considering that it is a multi-stage process, with the first input being light (from the sun), and all that work is done to transform it into something else, which is then transformed into… light. It can't be 100 percent efficient, and it certainly isn't, using today's technology. Surely there must be a way to let the natural sunlight become indoor lighting, and thus avoid the costs of building, installing, and maintaining solar panels. "There is such a way," points out the nearest wag. "They're called windows!"

Yet those windows are only of much use to the lucky souls who happen to have window offices, and even then only when the sun is facing those windows at a non-oblique angle. Wouldn't it be terrific if there were a way to capture all of that sunlight falling on the building's rooftop and outside walls, and distribute that throughout the building? According to scientists at the Oak Ridge National Laboratory in Oak Ridge, Tennessee, there is a way, and it uses fiber optics.

Fiber optics is considered by most people to be a recent discovery. Thus it would likely astonish them to learn that the principles of fiber optics were first developed during the 1790s and the 1870s, by various engineers and researchers — most of whom were ignored. It wasn't until the 1960s and 1970s that the potential of fiber-optic technology was given worthy attention, primarily for communication purposes. The strands of glass used to transmit the light, were made increasingly smaller (until reaching the limits of manufacturing), because there was no advantage to having a thicker tube to transmit the same amount of information.

But that team at the Oak Ridge National Laboratory is demonstrating that there truly is a valid reason for using thicker fiber-optic strands, namely, for bringing sunlight from outside of a building to the inside. The researchers point out that indoor electric lighting is the biggest consumer of electricity within commercial buildings. They have termed their new system "hybrid solar lighting" (HSL), and claim that it would reduce this energy usage by supplementing with sunlight the indoor lighting that currently relies entirely upon electricity. Fortunately, this supplementation would not take the form of doubling the number of light sources — with each traditional electric bulb being paired up with a hybrid solar light fixture — because the solar light is directed into electric bulbs, in particular, high-efficiency fluorescent lighting. At nighttime and on cloudy days, when the solar light is not flowing into the bulbs, traditional electricity would be used to generate light. At times when the sunlight was fully illuminating each room, the lights would draw no electricity, and would stay off automatically as directed by a sensor.

These results were reported in the laboratory's magazine, ORNL Review, and then again in an article posted on the website of World Science, dated 11 March 2005. The article notes that a similar technology for transmitting solar light through fiber-optic tubes had already been created in Japan. But according to the Oak Ridge scientists, their system has an advantage over the Japanese Himawari (sunflower) method in that it would move the technology from its current luxury niche market and into more widespread usage. They claim that this will occur because their design combines solar power with traditional electric light, as well as having demonstrable energy savings. They already have plans to help install a hybrid solar lighting system at the Sacramento Municipal Utility District's headquarters in Sacramento, California (under a California Energy Commission contract).

It will be interesting to see if one day in the future, all of the rooms in all of our buildings are receiving as much sunlight is possible. Perhaps then there won't be so much competition for the coveted corner offices.

Copyright © 2005 Michael J. Ross. All rights reserved.

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