Fiber-Optic Daylighting from Parans
Here's how it works: Sunlight is collected by one or more Swedish-made Parans solar panels mounted on the roof or a wall. A 39" by 39" (1 m2) SP2 solar panel has 62 Fresnel lenses, each of which focuses sunlight into a tiny optical fiber that's just 3/100ths of an inch (0.75 mm) in diameter. These 62 fibers are joined together into four bundles, each about a quarter-inch (6 mm) in diameter. These fiber bundles can transmit the light more than 66 feet (20 meters), delivering daylight to rooms on lower floors or interior. Five different luminaires are available for delivering light to occupied spaces. In the SP2 solar panel, three small motors are used in getting the individual Fresnel lenses to actively track the sun as it moves across the sky. These motors use electricity (so the SP2 must be wired), but consumption is minimal--is under two watts. The actual tracking is controlled by a photosensor that continually feeds sunlight data into a microprocessor. This means that the solar panel can be installed or relocated without any programming. As described in company literature, "At installation, the SP2 immediately scans the sky to detect the direction to the sun. It then learns and remem¬bers the solar path so that it always is ready to collect sunlight."
The cables of bundled fibers that carry the sunlight can be run through wall cavities, ceiling plenums, or other spaces in a building. The bending radius can be as tight as 2" (50 mm), allowing a wide range of installation locations. The longer the cable run the greater the loss. At a 33-foot (10 m) length, 64% of the light is retained; at 66 feet (20 m), about 40% is retained (see graph). The delivered light retains the full color spectrum of sunlight, according to Parans literature.
The actual optical fibers are made of PMMA (PolyMethylMethAcrylate), a type of plastic that maintains light transmission of 95.6% for each meter, and clad with a fluorinated polymer. The bundle of fibers is sheathed with Megolon, which is a halogen-free thermoplastic resin.
Of the five luminaires offered by Parans, two of them, the L1 and L3 provide pure sunlight, while the L2, L4, and L5 are hybrid models that combine sunlight and fluorescent lighting. L1 luminaires can be served by individual cables or ganged to provide light from two or four cables. The L2 is a round luminaire matched with a compact fluorescent lamp (CFL) that is available in a small model, delivering light from one bundle, or a larger model, served by four bundles. The L3 is a small spotlight, served by a single cable; it can be aimed to focus on a wall, floor, or ceiling. The L4 a linear luminaire, served by a single bundle and coupled with a T-5 fluorescent lamp, while the L5, is a square luminaire with acrylic diffuser, also coupled with a T-5 fluorescent.
As for cost, a typical system starts at about $10,000, according to Eric Huffman, of HUVCO. That would provide one SP2 collector, four bundles of optical fibers, and one to four luminaires. He notes that the system qualifies for the 30% federal tax credit.
The system is manufactured in by Parans Solar Lighting AB in Göteborg, Sweden, while HUVCO Daylighting Solutions is the U.S. distributor and also manufactures roof-mountain hardware and some of the fixtures. It was first introduced in Sweden in 2004 and became available in the U.S. in 2008. To date, about 20 installations have been completed in the U.S., according to Huffman.
When I asked Huffman about a fiber-optic daylighting system that was under development at Oak Ridge National Laboratory in 1999 (when we ran article on distributed daylight in EBN), he said that that system had been brought to market by Sunlight Direct, but then was taken off the market in 2009. Apparently, that system had some technical problems, including "catching things on fire."
For more information:
HUVCO Daylighting Solutions
I invite you to share comments on this blog. Is natural daylight important enough that building owners will want to spends tens of thousands of dollars to capture and distribute it throughout a building?
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Posted by Alex Wilson on March 3, 2010
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