Environmental Engineering Reference
In-Depth Information
5.1 Introduction
The controlled lighting of interior space has changed the world to a far greater
degree than any other human achievement. Mastery over the ability to see is,
fundamentally, the most ''enabling'' technology ever introduced. Yet, the light-
ing of interior spaces has been so successful and so ubiquitous, for so long, that
few citizens of industrialized societies would immediately identify the invention
of the electric light bulb as one of the most significant achievements of human
civilization. It was, however, the invention that made it possible to provide
abundant light to interior spaces safely, conveniently, and reliably at all times of
the day or night. The timeline in Fig.5.1 shows the progression of lighting
technology from oil lamps through the emergence of solid-state lighting [1].
Throughout the 1900s, the use of the sun as a light source for illuminating
building interiors evolved considerably. As we entered the century, the sun was
our primary source of interior light during the day, and the electric light bulb
was only slowly gaining practicality. Until the 1940s, sunlight remained the
primary means for lighting buildings, with electric lights as a supplement.
Eventually, however, the cost and performance of electric lamps improved,
and the sun was displaced as our primary method of lighting building interiors.
During the heightened energy awareness of the 1970s, a renewed interest in day
lighting emerged, yet that interest was outweighed by the convenience and cost
of electric light sources that could be placed virtually anywhere within build-
ings. Moreover, it became clear that the effective architectural integration of
daylight into modern buildings required skill and finesse to avoid potential
10
3
Solid-State
Lighting
100%
50%
Fluorescence/HID
10
2
25%
25%
AlGaInN
AlGaInN
AlGaInP
5%
5%
Incandescence
10
1
ZnSe
ZnSe
Tungsten
Filament
DH AlGaAs
AlGaAs
GaAsP:N
Filtered
Incande-
scence
Filtered
Incande-
scence
AlGaInN
Carbon
Filament
10
0
Gas Mantle
GaAsP:N
Fire
GaP:Zn,O
Gas
Kerosene
10
-1
GaAsP
Oil
SiC
10
-2
1
8
5
0
1
9
0
0
1
9
5
0
2
0
0
0
2
0
5
0
Ye a r
Fig. 5.1 Evolution of various interior lighting technologies. (Reprinted with permission
from Tsao, J. Y. (2004) Solid-State Lighting: Lamps, Chips and Materials for Tomorrow,
IEEE Circuits & Devices, 20(3), 28-37 (May/June) (# 2004 IEEE))
