Daylighting Solar Tube Lighting System

Daylighting solar tube lighting systems capture solar energy and transmit the sun’s light through a tube-based system.  This allows for interior areas to be illuminated with natural light.  Not to be misunderstood as conventional skylights, daylight solar tubes are sophisticated natural lighting solutions.  

 

Tubular Daylighting Devices

Sometimes called tubular daylighting devices, solar tubes can be seen as specialized, modern skylights which collect sunlight and then transmit the light through a sophisticated mirrored tube.  The light which emits from the tube is natural sunlight, allowing interior areas to receive natural light.

 

Solar Tubes in Detail

There is a large assortment of tubular daylighting devices (often called solar tubes, or light tubes) available from several manufacturers.  Many of these daylighting devices use very similar concepts, the main differences are often in the materials used and the general design implementation of the daylighting technology.

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Solar Tub3A tubular daylighting device or solar tube can be divided into three primary components:

  • Reflective Tubing.
    1. This is the light capturing component which is exposed to direct sunlight on the roof.  The solar collector may be implemented in several different orientations.  Often, the solar collector is a semi-sphere protruding slighting from the roof.  In other designs, the solar collector may have a flatter, more low-profile design which protrudes from the roof very slightly.  Not all solar collectors are round dome types.  Some use square shapes, often with a diamond styled dome.
    2. The solar collector’s function is to provide a direct interface from incoming direct sunlight to the solar tube itself.  The solar collector has a large impact on the amount of light delivered transmitted into the reflective tube, the color and quality of the light emitted, and how the daylighting device reacts to variances in sunlight and weather conditions.
  • The Solar Collector.
    1. The solar collector feeds light into the daylighting device’s reflective tubing section.  Here, sunlight bounces off of highly reflective materials several times as it travels towards the diffusing end of the solar tube.
    2. The reflective tubing section’s design is critical to the overall effectiveness of the daylighting device.  One common measurement of a daylighting device’s performance is its reflectivity efficiency.  In general terms, the reflectivity efficiency is a measurement of how much light is lost each time light bounces off the reflective material.  
    3. For example, a 99.5% reflectivity rate would indicate that with each “bounce” the solar tube loses 0.5% of the light.  Many solar tubes bounce the light several times as it travels toward the emitting section of the daylighting device.  The exact number of bounces varies in many daylighting devices depending on the angle of the sun light, with lower sun angles resulting in more bounces.  To summarize, a daylighting device with a 99.5% reflectivity rate loses 0.5% of the captured light per bounce.  Therefore, if the light bounces 5 times as it reaches the light emitter, it will have lost 2.5% of the light captured.
    4. Although reflectivity is a common measurement, it is not the only factor which determines the brightness of a solar tube style daylighting device.  The entire design, including the size and shape of the light tube, the solar tube’s positioning in relation to the sun, and the general implementation of the optical materials all affect the brightness, color, and quality of light emitted from the daylighting device.
  • Prismatic Diffuser Lense.
    1. Once light has been captured and transmitted through the solar tube, it exits the solar tube through the diffuser lense.
    2. The prismatic diffuser lense redirects light in many directions and in the process illuminates interior spaces.  The prismatic lense redirects light, as opposed to an opal diffuser lense which scatters light.  Prismatic diffusers produce a sharper, less dull light which is typically preferred to the softer light produced by an opal diffuser.


As you can see, tubular daylighting devices incorporate many lighting concepts and specialized optical materials to deliver natural lighting into interior spaces.  For information related specifically to Daylite’s products, please visit our Products Page, or Contact Us for more information.