When it is not possible to give natural lighting to a closed environment through windows or transparent openings on the walls or roof, there are only two systems left.
The first system is that of light ducts, the second instead exploits the technologies of optical fibers. Let's see how they work.
Light ducts. In the technique of natural lighting which uses the 'ducts', the light is captured by small transparent domes installed on the roof and equipped with optical systems capable of optimizing the collection of natural light.
The direct and diffused light captured by the domes are conveyed to a diffuser which constitutes the terminal element in the environment to be illuminated. The conveyance takes place through circular section aluminum tubes whose diameter can vary from 25 to 60 centimeters.
With i light ducts you can give natural lighting even in points distant from that of the collection, but with a limit of around 20-25 meters. Curves can also be imposed on the tubes, so as to have a certain flexibility, but it should be borne in mind that the longer and more tortuous the path, the higher the losses of light due to reflection.
Optical fibers. This technique of natural lighting is more recent than that of light ducts. The advantage lies in greater flexibility and in very small dimensions because the tubes are replaced by cables. However, the costs are higher.
In the system a optical fibers, a plane of moving lenses collects the adjusted sunlight to follow the apparent movement of the sun during the day. The aiming system of the capturing plane is managed by a microprocessor and made so that the lenses can concentrate the light on the optical fiber heads. Through the fibers the luminous flux is transported to the light diffuser terminals.
Light ducts is optical fibers they are economical and efficient systems for giving natural lighting to confined spaces without windows and skylights. The drawbacks are the potential overheating and the formation of annoying glare, especially in summer when the light is very intense. The glazed part of these systems must be open to let the hot air out and allow for nighttime ventilation.
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