Solar light pipes
Tags: Lighting, Renewables, solar
Light tubes are used to carry and distribute light which could be natural or artificial, when used with daylight they are referred to as solar light pipes.
Light tubes with reflective materials are the most common and longest used solar light pipes, the concept of which was developed by the ancient Egyptians, but not marketed commercially until 1991 when the Solatube was introduced in Australia. It has since been marketed commercially and residentially under many names.
Light rays travel in a tube of highly reflective material through a building, starting from an entrance point on a roof or outer wall. The entrance point usually consists of a dome (cupola), which collects and reflects as much sunlight as possible into the tube. Many units also have directional collectors, reflectors, or Fresnel lens devices which assist in collecting additional directional light down the tube. A light tube can not be used to create images, like a periscope so image distortion is not an issue and can in fact be beneficial due to the reduction of "directional" light. At the end point, where the light comes into use, a diffuser spreads the light into the room.
If the tube is short and straight then the light transmission is more efficient. When the tube is longer, angled, or flexible, part of the light intensity is lost. The high reflectivity of the tube lining is highly important to minimize losses. A heliostat can be installed to gain the maximum light. It tracks the movement of the sun, therefore it can capture sunlight into the light tube at all times of the day as far as the surroundings will allow, possibly with additional mirrors or other reflective elements that control the light path. The heliostat can even capture moonlight during the night.
Solar light pipes have several benefits over other more common lighting systems such as skylights and types of windows, they do not let the heat escape and have more flexibility for use in inner rooms; however they do not provide a view of the outside environment. Light tubes could be used in addition to windows to increase the amount of natural light exposure, contributing to residents or employees wellbeing whilst avoiding the need for harsh and over illuminated electric lights, and of course save energy. The daylight being transmitted will of course vary over the day, if at a point it becomes insufficient then artificial lights can be combined with the hybrid set-up.
Some artificial light sources are available with a spectrum similar to that of sunlight, as well as low flicker. They are designed to vary over the course of the day so as to copy the changes in natural light. Their manufacturers claim that their products have similar health benefits to natural light. However these products still consume energy through use, and so ultimately are less efficient in cost and do not benefit the environment. Light tubes do not require electric installations or insulation; they are particularly useful for wet indoor areas such as bathrooms and swimming pools. Aesthetically, transparent light tubes can be used as a new medium in modern architectural design.
In terms of security the small size of light tubes (especially compared to windows etc) and their high light output means they are ideal for use in secure environments, such as prisons and police cells. As they have a narrow diameter, and are mainly unaffected by internal security grills, daylight can be provided to areas without providing electrical connections and possibilities for escape or objects to be passed into a secure area.
Molded plastic light tubes are commonly used in the electronics industry to conduct illumination from LEDs on a circuit board to indicator symbols or buttons. Light tube indicators make electronics cheaper to manufacture.
