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Q: How often do you have to clean the collector?
A: In January 2003, an experimental hybrid solar lighting (HSL) system was cleaned for the first time. It had been installed in September 2002. The system's performance improved approximately 5% after the primary mirror, secondary mirror, and fiber end-faces were cleaned (about a 5-minute task). This indicates that cleaning the mirrors and end-faces at six-month intervals should be sufficient to keep a typical installation operating well.
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Q: Does the color of the distributed sunlight match natural sunlight?
A: In December 2002, staff at Oak Ridge National Laboratory (ORNL) measured distributed sunlight through the hybrid solar lighting (HSL) system and compared the result with direct, non-diffuse sunlight. Although the results have not published to date, initial data show that the two sources have very similar chromaticity values (a method of quantifying color) and correlated color temperatures at the same time, date, and location. Here is a data sample for referencing purposes:
HSL System:
(u', v') = (0.200, 0.497)
Color Temp. = 5150 K
Sunlight:
(u', v') = (0.208, 0.486)
Color Temp. = 5108 K
Lighting designers who have seen ORNL's demonstration have made several positive comments about the quality of HSL-distributed light. The data above substantiate that HSL-distributed sunlight closely matches direct sunlight.
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Q: How much space (and how many light fixtures) can one roof-mounted hybrid solar lighting (HSL) collector system illuminate?
A: The experimental 1-square-meter collector developed at Oak Ridge National Laboratory will illuminate about 500 square feet (approximately 8 light fixtures). The actual square footage being illuminated will depend on a number of factors associated with the particular space. In a commercial system, we anticipate that approximately 2 square meters of collectors will be needed to cover about 1000 square feet of space containing 16 light fixtures.
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Q: What do you do for lights on cloudy or overcast days?
A: The hybrid solar lighting (HSL) fixtures also contain standard T8 fluorescent lamps that are automatically dimmed (adjusted), using traditional electronic ballasts, according to the amount of sunlight available. Oak Ridge National Laboratory (ORNL) is testing a new daylight harvesting control sensor that distinguishes between natural and electric light; this will drastically reduce the commissioning requirements of HSL daylight harvesting systems.
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What do we know about global climate change?
