Anidolic lighting
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Anidolic lighting systems use anidolic optical components to light rooms. Light redirected by these systems does not converge to a focal point or form an image, hence the name (from ''an'', without, and ''eidolon'', image). Anidolic lighting uses non-imaging mirrors, lenses, and light guides to capture exterior
sunlight Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light. On Earth, sunlight is scattered and filtered through Earth's atmosphere, and is obvious as daylight when t ...
and direct it deeply into rooms, while also scattering rays to avoid glare. The human eye's response to light is non-linear, so a more even distribution of the same amount of light makes a room appear brighter. It is most challenging to effectively capture and redistribute light on cloudy, overcast days,Scartezzini, p. 14 when the sunlight is diffuse.


Optical elements

Mirrors are typically parabolic or
elliptical Elliptical may mean: * having the shape of an ellipse, or more broadly, any oval shape ** in botany, having an elliptic leaf shape ** of aircraft wings, having an elliptical planform * characterised by ellipsis (the omission of words), or by conc ...
mirrors. Lenses are frequently made in multiple sections, like a
Fresnel lens A Fresnel lens ( ; ; or ) is a type of composite compact lens developed by the French physicist Augustin-Jean Fresnel (1788–1827) for use in lighthouses. It has been called "the invention that saved a million ships." The design allows the c ...
. Light guides include
light pipe Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 tera ...
s and anidolic ceilings.


Lens systems

Lens systems use reflection and refraction within
optical prism Prism usually refers to: * Prism (optics), a transparent optical component with flat surfaces that refract light * Prism (geometry), a kind of polyhedron Prism may also refer to: Science and mathematics * Prism (geology), a type of sedimenta ...
s to redirect daylight. Some forms of prism lighting have been used for centuries, and others are 21st-century.
Deck prism A deck prism is a prism inserted into the deck of a ship to provide light down below. For centuries, sailing ships used deck prisms to provide a safe source of natural sunlight to illuminate areas below decks. Before electricity, light below a ...
s were set into the upper decks of ships to light the decks below. Pavement lights were set into floors or sidewalks to let light into a basement below. The underside was frequently extended into prisms to direct and spread the light. Prism tiles were designed to bend sunbeams coming through a window upwards, so that they would reach deeper into a room. They were placed in the upper parts of window frames, where they were called "transom lights".
Daylight redirecting window film Daylight redirecting film (DRF) is a thin, flexible plastic film which can be applied to a window to refract or reflect incoming light upwards, so that the deeper parts of the room are lit more evenly. It can be used as a substitute for opaque bl ...
(DRF) is a thin, flexible plastic version of the old glass prism tiles. It can be used as a substitute for opaque blinds. File:Luxfer sidewalk.gif, The basement under a sidewalk daylit with vault lights. File:Scatter.gif, Single vault light pendant prism, showing
total internal reflection Total internal reflection (TIR) is the optical phenomenon in which waves arriving at the interface (boundary) from one medium to another (e.g., from water to air) are not refracted into the second ("external") medium, but completely reflected b ...
. Multi-prism vault lights were also made. File:Window with prism tile transom.gif, Transom light. The upper part of the window is made of prism tiles, so the light passing through them is bent. File:2angles.gif, Two different prescriptions of prism tiles, showing their differing effects on the light File:Awning with show window.gif, Daylighting a shop with a shop window using prism tile transoms File:Daylight Redirecting Film.jpg, Daylight Redirecting Film (DRF), essentially a prism tile with very tiny prisms, sending light up onto the ceiling


Mirror systems

Anidolic mirror lighting systems can be divided into three parts: * daylight capture, usually with
zenith The zenith (, ) is an imaginary point directly "above" a particular location, on the celestial sphere. "Above" means in the vertical direction (plumb line) opposite to the gravity direction at that location (nadir). The zenith is the "highest" ...
al light collector * optimal transmission of the light (via anidolic ceilings,
light tube Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 tera ...
s, etc.) * distribution of captured light to target areas inside the rooms Architectural design also require optimal integration into the building facade.


Collection

Typically, light is captured with a compound parabolic collector (CPC) or elliptical collector (CEC) mounted on the exterior wall. These mirrors provide a wide and even collection pattern. The vertical capture angle approaches 90 degrees, from the
horizon The horizon is the apparent line that separates the surface of a celestial body from its sky when viewed from the perspective of an observer on or near the surface of the relevant body. This line divides all viewing directions based on whether i ...
to the vertical plane of the supporting wall. An even capture pattern alleviates the need for a
solar tracker A solar tracker is a device that orients a payload toward the Sun. Payloads are usually solar panels, parabolic troughs, fresnel reflectors, lenses or the mirrors of a heliostat. For flat-panel photovoltaic systems, trackers are used to mi ...
: a permanently fixed anidolic collector remains effective at any time of day. External parabolic collectors require proper
heat insulation In thermodynamics, heat is defined as the form of energy crossing the boundary of a thermodynamic system by virtue of a temperature difference across the boundary. A thermodynamic system does not ''contain'' heat. Nevertheless, the term is al ...
(usually double-glazed windows over the zenithal opening) and
roller blinds Roller may refer to: Birds *Roller, a bird of the family Coraciidae * Roller (pigeon), a domesticated breed or variety of pigeon Devices * Roller (agricultural tool), a non-powered tool for flattening ground * Road roller, a vehicle for compa ...
to reduce excessive lighting, glare and heat on sunny days. Snow and weatherproofing are also a consideration.


Transmission

Unlike the industrial
parabolic trough A parabolic trough is a type of solar thermal collector that is straight in one dimension and curved as a parabola in the other two, lined with a polished metal mirror. The sunlight which enters the mirror parallel to its plane of symmetry is foc ...
s used in
solar concentrator Concentrated solar power (CSP, also known as concentrating solar power, concentrated solar thermal) systems generate solar power by using mirrors or lenses to concentrate a large area of sunlight into a receiver. Electricity is generated when ...
s, architectural CPC mirrors do not concentrate captured light into a single focal point or focal line (which creates a
fire hazard Fire safety is the set of practices intended to reduce the destruction caused by fire. Fire safety measures include those that are intended to prevent the ignition of an uncontrolled fire and those that are used to limit the development and ef ...
). Instead, light is directed into the building through a relatively wide opening.


Distribution

A second CPC or CEC mirror acting as an angle transformer disperses this beam into a wide-angle, diffused pattern. If it transmits light from a wide external CPC, a light tube actually becomes a flat ''anidolic ceiling''.


Architectural integration

''Integrated anidolic systems'' reduce external protrusion and attempt to visually blend into traditional facades. However, like other anidolic systems, they are susceptible to glare and offer no protection from overheating on sunny days.Scartezzini, p. 15


Example

For example, the external CPC in the reference lights a 6-metre deep room. It protrudes 0.67 metres from the exterior wall and employs a 3.6 metre long, 0.5 meter tall
light tube Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 tera ...
, followed by a 0.9 metre long interior CPC, to deliver captured light into the back of the room. This arrangement provided 32% energy savings over a six-month period compared to a reference facade.


See also

*
Architectural light shelf A light shelf is a horizontal surface that reflects daylight deep into a building. Light shelves are placed above eye-level and have high-reflectance upper surfaces, which reflect daylight onto the ceiling and deeper into the space. Light shelve ...
*
Daylighting Daylighting is the practice of placing windows, skylights, other openings, and Reflective surfaces (climate engineering), reflective surfaces so that sunlight (direct or indirect) can provide effective internal lighting. Particular attention is ...
*
Deck prism A deck prism is a prism inserted into the deck of a ship to provide light down below. For centuries, sailing ships used deck prisms to provide a safe source of natural sunlight to illuminate areas below decks. Before electricity, light below a ...
*
Light tube Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 tera ...
*
Passive solar building design In passive solar building design, windows, walls, and floors are made to collect, store, reflect, and distribute solar energy, in the form of heat in the winter and reject solar heat in the summer. This is called passive solar design because, unli ...
* Pavement lights *
Sunroom A sunroom, also frequently called a solarium (and sometimes a "Florida room", "garden conservatory", "garden room", "patio room", "sun parlor", "sun porch", "three season room" or "winter garden"), is a room that permits abundant daylight and v ...


References


Sources

* * {{DEFAULTSORT:Anidolic Lighting Architectural lighting design