6 Artificial Lighting by wanghonghx


									7 Artificial Lighting

p   The subject of this chapter is artificial lighting, and the following
    chapter deals with natural lighting.
p   Although the principles of these two topics are treated
    separately it is important that they are considered together
    when designing a building.
The main functions of artificial

l   to provide enough light for people to
    carry out a particular activity
l   to provide enough light for people to move about
    with ease and safety
to display the features of the building in a manner
suitable for its character and purpose
l   To achieve these aims it is necessary to consider the
    properties of lamps, of the lamp fittings 灯具and of the
    room surfaces that surround them.
7.1 Lamps 灯

l   What is The oldest source of artificial light ?
    the flame from fires, from candles and from oil lamps

l   Convert chemical combustion化学燃烧 to light energy
 l    Modern sources of artificial light convert
      electrical energy to light energy

(1) Incandescent sources白炽灯
  lproduce     light by heating substances to a
  temperature at which they glow发热and are
(2) gas discharge sources气体放电灯

lproduce   light by passing an electric current through a gas or
vapour that has become ionised电离and hence able to conduct
lAt   low pressure, a luminous arc or discharge is formed between
the electrodes and useful quantities of light are given off
7.1.1 how to evaluate the Properties of lamps

1) Luminous efficacy 光效 which is given by the
  following formula.

Unit: lumens /watt (lm/W)
     2) Life 寿命

l   The luminous efficacy of a lamp decreases with time and for a
    discharge lamp it may fall by as much as 50% before the lamp
l   The nominal life of a lamp is usually determined by the
    manufacturer by considering the failure rate of a particular
    model of lamp combined with its fall in light output.
l   In a large installation it is desirable that all the lamps are
    replaced at the same time on a specified maintenance
3) The correlated colour temperature (CCT) 相关色温
is the absolute temperature of a perfect radiator when the colour
    apperance of the radiator best matches that of the light source
Unit : kelvin (K)

  •The CCT reflects the apparent color of light itself,
lThe   lower values of colour temperature indicate light
with a higher red content.
l   Some examples of colour temperatures are given below
l   Clear sky 晴天                     12,000-24,000K
l   Overcast sky 全阴天                  5,000-8,000K
l   Tubular fluorescent lamps         3,000-6,500K
l   Tungsten filament lamps            2,700-3,100K
Which one have the better color?
4)Colour rendering显色性is the ability of a light
  source to reveal the colour appearance of
l   This ability is measured by comparing the
    appearance of objects under the light source with
    their appearance under reference source such as
l   One system specifies the colour rendering of
    lamps by a colour rendering index(Ra) which has
    a value of 100 for an ideal lamp. Practical sources
    of white light range in Ra value between 50and 90

To make a comparison of the colour rendering
qualities of light sources easier,
colour rendering groups have been defined:

                  The CIE colour rendering groups
Group   Ra               Importance                       Typical application

        90...                                      Galleries画廊,美术馆 , medical
1A            accurate colour matching
        100                                        examinations, colour mixing
1B            accurate colour judgement            Home, hotels, offices, schools
2             moderate colour rendering            Industry, offices, schools
        40... accurate colour rendering is of
3                                                  Industry, sports halls
        60    little importance
        20... accurate colour rendering is of no
4                                                            Traffic lighting
        40    importance
l   Some tasks such as colour matching in the printing
    industry have high demands in accurate colour rendering
    and require special attention from the lighting designer.
l   For normal offices, however, the colour rendering group
    will be 1B or 2, which is easily achived with normal
    fluoresent lamps.
               Colour rendering index for different light sources
               Light source                    Colour rendering group
Incandescent                            1A
Metal halide                            1A ... 2
Fluorescent                             1A ... 3
High pressure sodium                    1B ... 4
Low pressure sodium                                       4
7.1.2 the fist type of artificial light
Incandescent lamps 白炽灯

Electric incandescent lamps work by passing an

electric current through a filament of metal and raising the
temperature to white heat.

When the metal is incandescent, at around 2800K , useful
quantities of light are given off.
1)   Most General Incandescent lamps is
     tungsten filament lamp.
 GLS lamps, or common light bulb, has a coiled filament
 contained within a envelope of glass which may be clear or
    The cost of a tungsten filament lamp is low and its
    installation is simple ,

    but the relatively short life of the lamp can cause the
    labour costs of replacement to be high.
l   The low luminous efficacy of the lamp produces high
    electrical running costs.
l   Only about 5% of the electrical energy is converted to
    visible light and most of the energy consumed is given
    off as heat, especially radiant heat.
2) The improved incandescent lamps:
Reflecting lamps 反射灯

l   The relatively large size of the standard tungsten filament lamp
    makes it difficult to control the direction of the light.
l   Spot lamps 聚光灯 are filament lamps with the glass bulb
    silvered inside and shaped to form a parabola 抛物线with the
    filament at the focus.
l   This arrangement gives a directional beam of light which is
    available in different widths of beam.
l   Sealed beam lamps密封光束灯 use similar techniques
l   Crown-silvered lamps 银冠灯 are standard filament
    lamps where the glass bulb is silvered in front.
l   When this lamp is used with a special external reflector
    it also gives narrow beams of light
some other improved incandescent lamp

         3) Tungsten-halogen lamps卤钨灯
l   Tungsten –halogen lamps have filaments which run at
    higher temperatures with the presence of a small
    quantity of a halogen gas, such as iodine 碘 or bromine
4) Low-voltage system

l   uses 12volt lamps fed from the mains by a
l   low-voltage bulbs need a lower resistance ,so the
    filament can be shorter, thicker and stronger.
l   The small size of these lamps give them good
    directional qualities which make them popular in shops
    for the display of goods.
l   The relatively low heat output of low-voltage systems
    is also an important property in stores where high
7.1.3 the second type of artificial light
gas discharge sources

Most General gas discharge source is
     Tubular fluorescent lamps 荧光灯管
Figure 7.2 Tubular fluorescent lamp


A improved form is
       Compact fluorescent lamps紧凑型荧光灯

l   Compact fluorescent lamps give a light quality suitable
    for domestic purpose and the use of such lamps are
    important technique for low-energy lighting in homes.
l   How is the coulur quality of gas discharge lamps?
l   Apart from the well-known tubular fluorescent lamp,
    gas discharge lamps usually have a poor colour rendering

l   So they have in the past been restricted to outdoor lighting,
    such as for roadways, where their generally poor colour
    qualities have not been important.
l   Modern types of discharge lamp have a colour rendering
    that is good enough for large-scale lighting inside
    building such as factories and warehouses仓库.
l   Continuing technical advances are producing more
    discharge lamps suitable for interior lighting
l   high efficiency of such lamps can give significant
    savings in the energy use of buildings.
    Some Modern types of discharge lamps

Mercury discharge lamps 汞放电灯
l    An uncorrected mercury lamp emits sharp light at certain blue
     and green wavelengths.
lIn   the mercury halide lamp
卤汞灯, metallic halides are
added to the basic gas
discharge in order to
produce better colour
rendering and to raise the

                             A metal halide gas discharge lighting
                             system provides illumination for a
                             college baseball game at Olsen Field
                             in College Station, Texas. Note the
                             various colors of the lights as they
                             warm up
Example of a Metal Halide lighting pole, at a
baseball field
Sodium discharge lamps钠放电灯

l   Low-pressure sodium
    lamps produce a distinctive
    鲜明的yellow light that is
    virtually 实质上
    monochromatic and gives
    poor colour rendering .
l   however the efficacy of the
    lamp is very high and they
    have been traditionally
    used for street lighting
A low pressure sodium/sodium oxide
(LPS/SOX) streetlamp at full power
Office building illuminated by high pressure sodium lamps.
l   High-pressure sodium lamps (SON) produce a
    continuous spectrum without much blue light but with a
    colour rendering that is more acceptable than the low-
    pressure sodium lamp.
l   SON lamps are used in modern street lighting and for
    the economic lighting of large areas such as forecourts篮
    球场 and warehouses仓库.
7.1.5 Lamp and energy conservation

l   Lighting is an important area of energy conservation in
    buildings as new systems can be installed in existing
    buildings as well as in new buildings.
l   The energy saved by a modernised lighting system usually
    pays for the cost of the installation within a few years, which is
    a shorter payback period than most methods of saving energy
    in buildings.
l   The major lamp companies of the World are therefore
    developing new types of low-energy lamps including
    improvements to the compact fluorescent lamp and high
    pressure discharge lamps described above.
7.2 Luminaires
Let’s do some judgements

   Direct 直接向下型
General diffusing 普通漫反射型


7.3 how to do Lighting design 照明设计

 First , find the standard service illuminance levels that are
 recommended for a variety of interiors and tasks given in Table
 7.3.      P156
 The aim of Lighting design is to reach the illuminance levels

Then , use Lumen method 流明法 to calculate the number of
 lamps needed.
 UF= utilisation factor 使用系数 is the ratio of the total flux
 reaching the working plane compared to the total flux output
 of the lamps table 7.4           P158


Hm——mounted height of the luminaire above the working plane

LLF=light loss factor 光损失系数is the ratio of the illuminance
provided at some given time compared to the initial illuminance
At the end of design, we should place these lamps in a
regular grid pattern and
their spacing must not exceed certain distances.
This maximum spacing depends on the type of luminaire and the
  height at which they set. Typical values are as follows
For fluorescent tubes in diffusing luminiaires
For filament lamps in direct luminaires
Figure 7.6 spacing of luminaires P160
Worked example 7.1

   A factory space measuring 40m by 12m by 4m in height
   requires a service illuminance of 500lux on the work benches
   which are set 1m above the floor. The 65W tubular fluorescent
   lamps chosen have a luminous efficacy of 80lm/W. they are to
   be mounted on the ceiling in luminaires which have a DLOR of
   50%. The room reflectances are 0.5 for the ceiling and 0.3 for
   the wall; the initial light loss factor is 0.7
a) Use the lumen method of design to calculate the number of
   lamps required
b) Suggest a suitable layout for the lamp fittings.
  l   E=?
  l   A=?
  l   F=?
  l   UF=?
  l   LLF=?
So number of lamps required=144 lamps
Suggested layout: 9 rows行of 16 luminaires
Check spacing using Smax=1.5XHm
So the suggested layout is satisfactory provided that the
distance between lamps is not greater than 4.5m
In a particular lighting system design ,the
following factors need to be considered

l   Light quantity should reach the illuminance levels
Natural light 自然光
lColour   quality 光的颜色

Glare 眩光
l   Directional quality 方向性
l   Energy use 能耗
l   Costs 运行费
l   Physical properties 物理性能
That’s all for chapter 7, let’s do a summary together.

   chapter 7 Artificial Lighting
  7.1 Lamps 灯
  7.1.1 how to evaluate the Properties of lamps
  Luminous efficacy 光效
  Life 寿命
  The correlated colour temperature (CCT) 相对色温
  Colour rendering显色性
7.1.2 Incandescent lamps 白炽灯

GLS lamps, or common light bulb

Reflecting lamps 反射灯

 Spot lamps         Sealed beam lamps   Crown-silvered lamps
Tungsten-halogen lamps卤钨灯

low-voltage bulbs
  7.1.3 Discharge lamps放电灯

Fluorescent lamps 荧光灯
Compact fluorescent lamps紧凑型荧光灯

Mercury discharge lamps 汞放电灯
Sodium discharge lamps钠放电灯
7.2 Luminaires 灯具
7.3 how to do Lighting design 照明设计

First , find the   standard service illuminance levels

Then , use Lumen method 流明法 to calculate the
  number of lamps needed.

At the end of design, we place these lamps in a
  regular grid pattern
Practices in class
1 Modern sources of artificial light convert (   ) to (   )

A chemical energy
B electrical energy
C light energy
D heat energy
2 Oldest sources of artificial light convert (   ) to (   )

A chemical energy
B electrical energy
C light energy
D heat energy
3 Modern sources of artificial light are of
two general types:(     )

A incandescent lamps
B discharge lamps
C mercury discharge lamps
B tungsten filament lamps
4 The following lamp is (   )
A common light bulb
B spotlamp
C crown-silvered lamp
D tungsten-halogen lamp
5 The following lamp is (    )
A tubular fluorescent lamp
B compact fluorescent lamp
C mercury discharge lamp
D sodium discharge lamp

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