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Daylighting & Artificial Lighting - Coggle Diagram
Daylighting & Artificial Lighting
FUNDAMENTAL OF LIGHT
light is a creative medium, its basic function is to
enable humans to see
humans visual perception relies on the quantity of light and its spectral distribution
seeing is not only about distinguishing light and shade, but also color
the movement of light is a linear process where time and space meet
any moment reveals frozen movement in time
humans have evolved to respond to daily and seasonal change brought about by the movement of the sun, the moon and the stars
human tracks the change of day into night as well as form and surfaces moving in light
two different effects
it lightens the objects humans want to see
it shines directly in the eyes
DAYLIGHTING
Introduction
combination of direct sunlight and atmospheric light (dispersion of sun radiation by dust and water) with indirect and reflected components
has a broad spectrum with a peak in the blue green and a cut off in the ultra violet (wavelength of 290 nm)
caused by the atmosphere of the Earth
works as a filter
shorter wavelengths are intercepted by the atmosphere, the ozone layer playing an important role in this
3 components
direct sunlight from the sky
sky component (SC) normally refers to the diffuse sky
e.g. it is not used to describe direct sunlight
light that comes from external surfaces
externally reflected component (ERC) (relevant in dense urban situations)
tends to come from a low angle close to horizontal
penetrate deeper into the space than the SC, although it is much weaker
light that is reflected from internal surfaces
internally reflected component (IRC) is normally fairly uniform all over the room
Role of Envelope in Daylighting
lighting design begins with recognizing the entry of daylight
because the presence of daylight in an interior strongly influences spatial perception
also changes the color of surfacing materials in terms of how they appear elsewhere in the room under a number of different kinds of electric illumination
The amount of sunlight reflected about an interior is determined by the size and shape of apertures in the spatial envelope
direct daylight penetrates deeper into a room, the higher the top of the window is above the floor
Windows can reduce dependence on
electric lighting
lower energy cost
the illumination provided by the sky should not be greater than direct sunlight
Daylighting Quality
glare
disabling
when it interferes with the ability to see.
discomfort
when there is excessive contrast between light and dark surfaces in a room.
does not necessarily increase with increasing window size
light distribution
Factor Affecting Daylighting
room finishes
for maximum daylight levels, uniformity and the least glare, room surfaces should have matte /dim finishes
shiny finishes create reflections that result in glare
glass type
allows the highest transmission of the visible portion of the solar spectrum provides the highest daylight levels
window position
the higher the window, then
the greater the daylight factor (DF)
DF is a daylight availability metric that expresses as a percentage the amount of daylight inside a room (on a work plane) compared to the amount of unobstructed daylight outside under overcast sky conditions
the deeper the penetration of daylight into the space
extending the window to the floor does little to increase daylight levels
clerestory windows have to allow deep penetration of daylight
while avoiding normal viewing angles
Daylighting Application Issues
the arrival of inexpensive energy and the proliferation of fluorescent lights in the 1950-1960s made daylight almost irrelevant
the 'glazed skin' look of many buildings became an expensive in 1970s
increasing heating and cooling cost
cooling cost is a major cost
new construction characteristic
deemphasized direct sunlight
brought forth lower ceilings and lower building skin to volume ratios
sustainable architecture
the illumination of spaces with daylighting has become important
main principles
energy
the usage of renewable energy minimizes the consumption of artificial light
land use
It is not a commodity but the base of life
local material
renewable local materials have to be used
Benefits
perceived as more attractive and comfortable
the blend of these colors makes up white daylight because sunlight emitted covers a wide spectrum of colors
artificial lighting sources cannot exactly
reproduce the sun’s color spectrum
dynamic
varies through the seasons and times of the day, the
position of the sun, and cloud cover
artificial light is static
the required amount of artificial light in interior space is set at a level required for minimum comfort
reaches considerably greater light levels, which is perceived to be more pleasant.
emitted by all sides of the celestial hemisphere and the sun
its distribution results in the illumination of the environment
comfortable for eye
potential for energy saving
increasing either visual comfort and energy saving
presence of encouraging in saving energy through daylighting implementation while reducing thermal radiation as well
create positive effect on the physical and psychological well being of its users
Glazing System
the basic method of maximizing daylight intake to the interiors is glazing
advanced implementation: selective coatings or low emissivity window glazing
optimized to be transparent to daylight
opaque to potentially detrimental UV radiations
factors affecting glass envelope design
height of the building
distance between slabs
location of the building
span of each panel
advantages of advanced glazing system
cut energy consumption
prevent associated pollution sources
reduce peak demand
enhance daylighting performance
improve occupant comfort
less air leakage
improve comfort
warmer glazing surface temperature
minimize condensation
features of advance glazing system
multiple types of glass
specialized
transparent coatings
insulating gases sandwiched between panes of glass
improved frames
issues to consider included in advance glazing system
acoustic control
ultraviolet control
condensation control
thermal comfort
heat gains and losses
visual requirements (glare, view, privacy)
shading and sun control
security issues
color effects
energy requirements
daylight performance
Advanced Daylight Systems
Light Shelves
main goal
take the optimum level of sunlight to illuminate the interiors of the buildings
designed to provide sunlight intake and lead the sunlight into the floors to provide diffuse lighting (as an illumination source)
the positions of the light shelves
depend on the volume of the spaces in order to
provide indoor outdoor relations
prevent glare
If the position is far from the ceiling, more light can be taken
solar light reflections are used with artificial light sources
provide the same homogenous lighting levels obtained during both day and night.
Dynamic Light Shelves Sytem
movable to prevent direct light glare while providing deep penetration of sunlight into the room
two groups
manual systems
users arrange the positions of the shelves according to seasons, months, etc., and the sun's position.
automatic systems
a microcomputer arranges the positions and angles of the shelves according to seasons to provide efficient illumination
disadventages
expensive
expensive and require more technical staff space
possibility of breakdowns in systems because of electrical system usage
two factors directly affect the positions & efficiency of light shelves
climate
latitude and longitude coordinates of buildings
Daylight Transmitting Systems
especially used in buildings with insufficient or no opening
daylight is taken from one point, collected, and distributed to the spaces.
types of daylight transmitting system
Light Tubes
emit daylight from one optical staff and transmit it to the spaces
suitable implemented in the deep spaces (e.g. large office buildings)
consist of 3 parts
collector/dome
positioned on rooftops
using hemi sphere-shaped optics or tube to collect daylight
transmitter/tubing
distributor/diffuser
have more complex mechanisms and need more structural spaces (small skylight)
effects on long term
more economical
effective for wide and multiple spaces
Fiber Optics
specified optical fibers that transmit and lead the light rays even through long ranges
mechanism
solar panels or helio-static units positioned on the rooftops collect daylight transmitted with fiber optic cables
daylight is transmitted to light tubes
tubes are directly related to the spatial lighting source to illuminate the spaces during the day
the greater the length of the tube, the greater the light loss
10 m = 64% of the light is delivered
advantages
more efficient than many daylight intake systems
less light loss
disadvantages
sensitive structures of fiber optic cables may create problems
high cost of treatment
Anidolic Systems
do not collect sunlight
absorb sunlight with a glass semi-optics unit and transmit it to the ceiling system directly (without collector/reflector/mirror)
limited implementation
must be used with their special ceiling systems
less economical
Other Systems
example
Holographic optic panels
carvings of specially designed textures to laminated glass with laser technology
have specific features to emit sunlight as much as possible
assembled on the facades of the buildings and directly transmitted to the ceiling and illumination system
advantage
efficient
disadvantages
cladding of hole surfaces with these panels
maintenance problems
Prismatic panels
special glass panels with similar features to holographic panels
mostly suitable for use in hot climate conditions
ARTIFICIAL LIGHTING
Incandescent
the release of thermal radiation from a body due to its temperature (yellow lamp)
produced when electricity passes through a fine tungsten filament
It occurs in light bulbs because the
filament resists the flow of electrons
this resistance heats the filament to a temperature (black body radiation falls in the visible spectrum)
The majority of radiation is emitted in the invisible infrared and lower frequency spectrums
very inefficient
advantages
greatest amount of flexibility
directional or non directional illumination
varied size and shape
easy dimming
quick on
frequent starts
high optical control
low initial cost
excellent CRI
disadvantages
low efficacy rating
generation of heat
relatively short life
damages artwork, fabrics, and other precious materials
Fluorescent
a low pressure mercury vapor gas discharge lamp
uses fluorescence to produce visible light
electricity is released through mercury vapor in a tube
ultraviolet light gives a blue cast to rooms
advantages
energy efficient
high lumen output
long life
radiate less heat than incandescent
moderate initial cost
low operating cost
variety of color options
use up to 80 less energy than incandescent
can last up to 18 times longer than incandescent
disadvantages
needs ballast
flickering can occur
indoor use only
time needed to reach maximum lumen output
sensitive to ambient temperatures
dimming is expensive
shape and size limitations
variations between lamp manufacturers
mismatches with lamps and ballasts
continuous on and off is detrimental to life and performance of lamp
Halogen
an incandescent lamp consisting of a tungsten filament sealed in a compact transparent envelope filled with a mixture of inert gas and a small amount of a halogen (e.g. iodine/bromine)
it usually casts a bright, white light
halogen regenerative cycle
evaporated tungsten redeposit on the filament
requires a heat resistant glass (quartz)
advantages
20-30% more efficient
than incandescent
longer life
whiter light
higher color temperature
and efficacy rating
High-Intensity Discharge (HID)
similar to the fluorescent lamp
illumination begins with an arc between 2 electrodes
operates in a gas filled cylindrical tube
requires ballasts
creates radiant energy from gases and metal vapors
advantages
gives decent CRI, color temperature
very good optical control
very high efficacy
very long life
operation in a wide range of ambient temperatures
positive long term economics
disadvantages
long start up time
long restart time
color shifts during the life of the lamp
variations in color between the same lamps
strict ballast requirements
not easily dimmable
Light-Emitting Diode
an electric light that produces light using light emitting diodes
advantages
significantly more energy efficient than equivalent incandescent lamps
can be made in almost any incandescent bulb shape
can be made in almost any fluorescent bulb shape
very long life
very high efficacy
dimmable
disadvantages
very high initial cost
heat dissipation concerns
CRIs typically only in the 80 ’s