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Matthew Traum

Tubular Daylighting Devices (TDDs) Provide Residential-scale Illumination

Earlier this year, electric light bulb manufacturer Philips Electronics led a coalition establishing a government mandate to phase-out inefficient incandescent lamps by substituting energy-efficient alternatives. The details of this initiative are outlined in “Philips Advocates Industry Phase-Out of Inefficient Lighting”, appearing in FlashlightNews.com.

While noble on the surface, the self-serving intent underlying this initiative becomes obvious when the proposed alternative illumination sources are considered: compact fluorescent lamps (CFLs), halogen lamps, and light emitting diode (LED) lamps. Each of these products is manufactured by Philips, and the company would realize substantial benefit from a federally-endorsed nation-wide lighting retrofit using Philips products.

For energy managers seeking illumination alternatives, my recent post, “Sunlight Direct’s Optical Fibers Enable Piping of Natural Light Through Buildings” covers a new day-lighting technology for commercial buildings. However, the parabolic light collectors underpinning this technology cost $10,000 per unit. So, is there a viable residential-scale day-lighting alternative that a private homeowner can afford?

Enter the Tubular Daylighting Device (TDD). Like Sunlight Direct’s hybrid light fixtures, TDDs capture rooftop sunlight, redirecting it internally to where illumination is needed. However, instead of fiber-optics, the TDD uses a hollow metallic channel to pipe light to its destination.

Among the top TDD manufactures is Vista, CA based Solatube International, Inc., which pioneered the TDD lighting technique in the 1980’s. Solatube recently introduced the 160 DS and the 290 DS rooftop collectors, which the company claims can light 200 and 300 square feet respectively.

Like more advanced daylight systems, TDDs filter out some of sunlight’s infrared spectrum, reducing unwanted internal heating. Add-on kits with integrated fluorescent lamps can be added to the light-directing channel, allowing the TDD to function like a normal light fixture when sunlight is not available.

Installations of Solatube International, Inc. TDDs start around $400. For incandescent bulb replacement, the simple payback period on this technology pushes 30 years. Nonetheless, it represents a zero-energy alternative to CFLs, halogen lamps, and LEDs in a price range accessible to residential homeowners.