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|Title: ||An analysis of daylighting performances in office buildings and applications of light-guide system coupled with redirecting device|
|Other Titles: ||Shang yong lou yu cai guang huan jing ji rou he zhuan xiang zhuang zhi de guang dao guan ying yong zhi fen xi|
|Authors: ||Tsang, Kin Wai (曾建偉)|
|Department: ||Department of Building and Construction|
|Degree: ||Doctor of Philosophy|
|Issue Date: ||2010|
|Publisher: ||City University of Hong Kong|
Office buildings -- Lighting.
|Notes: ||CityU Call Number: TH7791 .T75 2010|
xxiii, 305 leaves : ill. 30 cm.
Thesis (Ph.D.)--City University of Hong Kong, 2010.
Includes bibliographical references (leaves 225-237)
|Abstract: ||Daylight is a valuable natural resource and plays a crucial role in passive solar
building design. Appropriate daylighting design not only provides a connection with
outside, ensuring an adequate illuminance level with high uniformity and a glare-free
environment but also provides an opportunity for energy saving and carbon reduction.
However, in metropolitan Hong Kong, vast high-rise buildings are built closely together
resulting in a severely indoor daylight environment.
To acquire in-depth understanding of the daylight environment of current buildings
in Hong Kong, a survey on the daylighting performance of local buildings was
conducted. In total, 35 air-conditioned non-residential buildings built from 1962 to
2004 spreading over different districts were selected for the study. The findings
suggest that the rear part of rooms rarely receives adequate amount of daylight and the
average obstruction angle for buildings in Hong Kong is between 30° and 60°. It is
envisaged that traditional daylighting designs are not able to fulfil the needs of
occupants and there is a potential to use novel daylighting devices to transmit light from the zenith of a sky dome to interior part of the buildings.
And therefore, the performance of several daylighting systems was investigated.
The first one was a vertical light-pipe system. It was studied through field
measurements and its performance was promising. For nearly half of the operating
hours, the internal illuminance design level can be achieved by daylight alone.
However, vertical light pipes are usually installed in floors near the roof and reduces its usability in high-rise non-residential buildings.
The second type of system being studied was the laser cut panel (LCP). Its
installation is simple and redirects daylight into deeper parts of a room. LCP can
improve the indoor daylight environment under most sky conditions. Both uniformity
and the illuminance of the rear part of rooms have significant improvement. The
performance of LCP is highly dependent on the internal layout of the room. Any
obstruction which intercepts redirected daylight seriously affects the performance of
Subsequently, horizontal light pipe (HLP) seems to be able to remedy the situation.
However, the HLP cannot transmit light from high elevations effectively, and hence,
another system integrating the LCP with a HLP (LLP) is of interest. To investigate the
performance of this system, experimental works were conducted to identify the
transmission characteristics of this system. The LCP can reduce the number of
reflection with light pipes and hence it can increase the overall transmittance for light from high elevations. Through a simulation study, it is found that for most sky
conditions, the LLP have a larger transmittance than conventional the HLP.
Annual performance of a daylighting system is an important parameter to assess a
design. However, even though computational power is improving, conducting an
annual assessment of daylighting systems is still not feasible. Fortunately, employing
daylight coefficient concepts can greatly reduce the simulation time for long-term
system evaluation. In this study, a two-step daylight coefficient simulation approach is
proposed. Its performance was validated against measured data. And finally, a
simple daylighting assessment tool was developed. Its major algorithms are discussed.
It is believed that this study can provide a better understanding and more accurate
design method of daylighting systems for architects and engineers.|
|Online Catalog Link: ||http://lib.cityu.edu.hk/record=b3947684|
|Appears in Collections:||BC - Doctor of Philosophy |
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