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Page 1

AN ANALYSIS OF DAYLIGHTING

PERFORMANCES IN OFFICE

BUILDINGS AND APPLICATIONS

OF LIGHT-GUIDE SYSTEM

COUPLED WITH REDIRECTING

DEVICE

TSANG KIN WAI

DOCTOR OF PHILOSOPHY

CITY UNIVERSITY OF HONG KONG

August 2010

Page 2

CITY UNIVERSITY OF HONG KONG

香港城市大學

An Analysis of Daylighting Performances in

Office Buildings and Applications of

Light-guide System Coupled with

Redirecting Device

商用樓宇採光環境及揉合轉向裝置的光導

管應用之分析

Submitted to

Department of Building and Construction

建築學系

in Partial Fulfillment of the Requirements

for the Degree of Doctor of Philosophy

哲學博士學位

by

Tsang Kin Wai

曾建偉

August 2010

二零一零年八月

Page 12

xi

Figure 6.12 Comparison of LLP exiting luminous flux from the sky using the NN and

standard method .................................................................................... 160

Figure 6.13 Comparison of LLP exiting luminous flux from the sky using the

"interpolated" and standard method ...................................................... 160

Figure 6.14 Comparison of HLP exiting luminous flux from the sun using the NN and

standard methods ................................................................................... 162

Figure 6.15 Comparison of HLP exiting luminous flux from the sun using the

"interpolated" and standard methods .................................................... 163

Figure 6.16 Comparison of the LLP exiting luminous flux from the sun using the NN

and standard method ............................................................................. 163

Figure 6.17 Comparison of LLP exiting luminous flux from the sun using the

"interpolated" and standard methods .................................................... 164

Figure 6.18 Calculation procedure for indoor illuminance level by the daylight

coefficient and light transfer coefficient ............................................... 166

Figure 6.19 Plan and section of the generic office building ..................................... 169

Figure 6.20 Rendering for the model employed in the simulation ........................... 171

Figure 6.21 Annual mean RI at the first floor facing north ...................................... 173

Figure 6.22 Annual mean RI at the first floor facing east ........................................ 173

Figure 6.23 Annual mean RI at the first floor facing south ...................................... 174

Figure 6.24 Annual mean RI at the first floor facing west ....................................... 174

Figure 7.1 Calculation procedures adopted in the software ................................... 189

Figure 7.2 Calculation procedures for the daylight coefficient module ................. 191

Figure 7.3 Calculation algorithm of rdirect,i for SC and ERC .................................. 195

Figure 7.4 Calculation algorithm of daylight coefficient for IRC .......................... 202

Figure 7.5 Calculation algorithm of determining the coefficient for daylighting

devices ................................................................................................... 205

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xii

Figure 7.6 Flowchart for daylight illuminance calculation for each time step ....... 208

Figure 7.7 The illuminances simulated by RADIANCE and Photopia and the simple

software for skies nos. 2, 4 and 6 .......................................................... 212

Figure 7.8 The illuminances simulated by RADIANCE and Photopia and the simple

software for skies nos. 7 to 10 ............................................................... 213

Figure 7.9 The illuminances simulated by RADIANCE and Photopia and the simple

software for skies nos. 11 to 15 ............................................................. 213

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xxii

nair Refractive index of air (dimensionless)

npanel Reflective index of panel (dimensionless)

Pset Set of ray belongs to direct sky pipe transfer coefficient (dimensionless)

Pz Portion of the zenith overcast sky form which illuminance can enter the

guide (degree)

pc Pipe transfer coefficient (dimensionless)

pcdirect sky Pipe transfer coefficient for direct sky (dimensionless)

pcdirect sun Pipe transfer coefficient for direct sun (dimensionless)

pcindirect sky Pipe transfer coefficient for indirect sky (dimensionless)

pcindirect sun Pipe transfer coefficient for indirect sun (dimensionless)

Qin Entering luminous flux for light coming from particular direction (lm)

Qout Exiting luminous flux for light coming from particular direction (lm)

r Radius (m)

ri Angle of refraction (degree)

rext Ratio of indoor illuminance to external luminance (dimensionless)

rIRCA Ratio of Ea to external luminance (dimensionless)

rIRCB Ratio of Eb to external luminance (dimensionless)

rmin Minimum angle of refraction (degree)

rmax Maximum angle of refraction (degree)

rpipe Ratio of light pipe exiting light flux to external luminance

(dimensionless)

Rb Average reflectance of surface in the rear half of the room

(dimensionless)

Rf Minimum fraction of output level (fraction)

Rw Minimum fraction of power consumption (fraction)

s Arbitrary variable (dimensionless)

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xxiii

T Set of ray belongs to direct sky daylight coefficient (dimensionless)

Tc Transmittance of dome (dimensionless)

To Transmittance of diffuser (dimensionless)

W Cut Depth (m)

Wrm Width of room measured parallel to the window (m)

x Coordinate to x-axis (dimensionless)

xo Coordinate x of new origin (dimensionless)

x‟ Transformed coordinate x (dimensionless)

x‟‟ Coordinate x of shadow (dimensionless)

y Coordinate to y-axis (dimensionless)

yo Coordinate y of new origin (dimensionless)

y‟ Transformed coordinate y (dimensionless)

y‟‟ Coordinate y of shadow (dimensionless)

Z Zenith angle (degree)

Zs Solar zenith (degree)

z Coordinate to z-axis (dimensionless)

zo Coordinate z of new origin (dimensionless)

z‟ Transformed coordinate z (dimensionless)

z‟‟ Coordinate z of shadow (dimensionless)

AN ANALYSIS OF DAYLIGHTING

PERFORMANCES IN OFFICE

BUILDINGS AND APPLICATIONS

OF LIGHT-GUIDE SYSTEM

COUPLED WITH REDIRECTING

DEVICE

TSANG KIN WAI

DOCTOR OF PHILOSOPHY

CITY UNIVERSITY OF HONG KONG

August 2010

Page 2

CITY UNIVERSITY OF HONG KONG

香港城市大學

An Analysis of Daylighting Performances in

Office Buildings and Applications of

Light-guide System Coupled with

Redirecting Device

商用樓宇採光環境及揉合轉向裝置的光導

管應用之分析

Submitted to

Department of Building and Construction

建築學系

in Partial Fulfillment of the Requirements

for the Degree of Doctor of Philosophy

哲學博士學位

by

Tsang Kin Wai

曾建偉

August 2010

二零一零年八月

Page 12

xi

Figure 6.12 Comparison of LLP exiting luminous flux from the sky using the NN and

standard method .................................................................................... 160

Figure 6.13 Comparison of LLP exiting luminous flux from the sky using the

"interpolated" and standard method ...................................................... 160

Figure 6.14 Comparison of HLP exiting luminous flux from the sun using the NN and

standard methods ................................................................................... 162

Figure 6.15 Comparison of HLP exiting luminous flux from the sun using the

"interpolated" and standard methods .................................................... 163

Figure 6.16 Comparison of the LLP exiting luminous flux from the sun using the NN

and standard method ............................................................................. 163

Figure 6.17 Comparison of LLP exiting luminous flux from the sun using the

"interpolated" and standard methods .................................................... 164

Figure 6.18 Calculation procedure for indoor illuminance level by the daylight

coefficient and light transfer coefficient ............................................... 166

Figure 6.19 Plan and section of the generic office building ..................................... 169

Figure 6.20 Rendering for the model employed in the simulation ........................... 171

Figure 6.21 Annual mean RI at the first floor facing north ...................................... 173

Figure 6.22 Annual mean RI at the first floor facing east ........................................ 173

Figure 6.23 Annual mean RI at the first floor facing south ...................................... 174

Figure 6.24 Annual mean RI at the first floor facing west ....................................... 174

Figure 7.1 Calculation procedures adopted in the software ................................... 189

Figure 7.2 Calculation procedures for the daylight coefficient module ................. 191

Figure 7.3 Calculation algorithm of rdirect,i for SC and ERC .................................. 195

Figure 7.4 Calculation algorithm of daylight coefficient for IRC .......................... 202

Figure 7.5 Calculation algorithm of determining the coefficient for daylighting

devices ................................................................................................... 205

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xii

Figure 7.6 Flowchart for daylight illuminance calculation for each time step ....... 208

Figure 7.7 The illuminances simulated by RADIANCE and Photopia and the simple

software for skies nos. 2, 4 and 6 .......................................................... 212

Figure 7.8 The illuminances simulated by RADIANCE and Photopia and the simple

software for skies nos. 7 to 10 ............................................................... 213

Figure 7.9 The illuminances simulated by RADIANCE and Photopia and the simple

software for skies nos. 11 to 15 ............................................................. 213

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xxii

nair Refractive index of air (dimensionless)

npanel Reflective index of panel (dimensionless)

Pset Set of ray belongs to direct sky pipe transfer coefficient (dimensionless)

Pz Portion of the zenith overcast sky form which illuminance can enter the

guide (degree)

pc Pipe transfer coefficient (dimensionless)

pcdirect sky Pipe transfer coefficient for direct sky (dimensionless)

pcdirect sun Pipe transfer coefficient for direct sun (dimensionless)

pcindirect sky Pipe transfer coefficient for indirect sky (dimensionless)

pcindirect sun Pipe transfer coefficient for indirect sun (dimensionless)

Qin Entering luminous flux for light coming from particular direction (lm)

Qout Exiting luminous flux for light coming from particular direction (lm)

r Radius (m)

ri Angle of refraction (degree)

rext Ratio of indoor illuminance to external luminance (dimensionless)

rIRCA Ratio of Ea to external luminance (dimensionless)

rIRCB Ratio of Eb to external luminance (dimensionless)

rmin Minimum angle of refraction (degree)

rmax Maximum angle of refraction (degree)

rpipe Ratio of light pipe exiting light flux to external luminance

(dimensionless)

Rb Average reflectance of surface in the rear half of the room

(dimensionless)

Rf Minimum fraction of output level (fraction)

Rw Minimum fraction of power consumption (fraction)

s Arbitrary variable (dimensionless)

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xxiii

T Set of ray belongs to direct sky daylight coefficient (dimensionless)

Tc Transmittance of dome (dimensionless)

To Transmittance of diffuser (dimensionless)

W Cut Depth (m)

Wrm Width of room measured parallel to the window (m)

x Coordinate to x-axis (dimensionless)

xo Coordinate x of new origin (dimensionless)

x‟ Transformed coordinate x (dimensionless)

x‟‟ Coordinate x of shadow (dimensionless)

y Coordinate to y-axis (dimensionless)

yo Coordinate y of new origin (dimensionless)

y‟ Transformed coordinate y (dimensionless)

y‟‟ Coordinate y of shadow (dimensionless)

Z Zenith angle (degree)

Zs Solar zenith (degree)

z Coordinate to z-axis (dimensionless)

zo Coordinate z of new origin (dimensionless)

z‟ Transformed coordinate z (dimensionless)

z‟‟ Coordinate z of shadow (dimensionless)