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Energy saving integrated facade: design and analysis using computer simulation

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Energy saving integrated facade: design and analysis using computer simulation

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ENERGY SA VING INTEGRA TED FACADE:
DESIGN AND ANALYSIS USING COMPUTER SIMULA TION

by

Tai Uey Huang

A Thesis Presented to the
FACULTY OF USC THE SCHOOL OF ARCHITECTURE
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
MASTER OF BUILDING SCIENCE

August 2010

Copyright 2010 Tai Uey Huang

ii

Acknowledgments
I would like to express my deep and sincere gratitude to my committee chair, Prof. Doug
Noble, whose encouragement, guidance and support from the initial to the final level
enabled me to develop an understanding of the subject. Thanks for his thesis direct; you
are my best committee chair.
Thanks to Prof. Pablo La Roche for valuable suggestions and direct. Thanks for his
constant support. Without his help, this thesis would not be possible. His wide knowledge
and his logical way of thinking have been of great value for me.
Thanks to my committee Jeffrey Vaglio for his valuable information and direct. His
understanding, encouraging and personal guidance have provided a good basis for the
present thesis
Thanks to every member in MBS and School of Architecture. I really enjoy the study with
you and learn a lot from each other.
Thanks to every friends here in California, without you I could not have experienced a
great study abroad life.
I cannot express my full gratitude to Tingbao who patiently visited me in LA and share her
time with me.
Lastly, I would like to thank my family for their support. Without their encouragement and
financial support it would have been impossible for me to complete my study abroad
dream.

iii

Table of Contents

Acknowledgments.................................................................................................................ii
List of Tables......................................................................................................................v
List of Figures ....................................................................................................................vi
Abstract ................................................................................................................................x
Chapter 1 Introduction ...................................................................................................1
1.1 Motivation and background………………………………………………….…2
1.2 Original work………………………………..…………………………….……3
1.3 Organization of this thesis………………..………………………………….…5

Chapter 2 Research Background....................................................................................7
2.1 BIPV...……………………………………………………………………....…7
2.2 Application of solar power.................................................................................19
2.3 BIPV case study.................................................................................................22
2.4 Building insulation efficiency............................................................................27
2.5 Ambition lighting efficiency...………………………….…………………..…30
2.6 Ventilation efficiency...………………………………………………………..33

Chapter 3 Research Scope, Objectives, Procedure and Method ................................. 39
3.1 Research Scope..................................................................................................39
3.2 Research Objectives.......................................................................................... 41
3.3 Research Procedure and Method.......................................................................44
3.4 Working Schedule……………......................................................................... 47

Chapter 4 Energy Saving Integrated Façade Computer simulation ............................ 48
4.1 Energy saving integrated façade design.............................................................48
4.2 Simulation model...............................................................................................53
4.3 Solar power calculation.................................................................................... 60
4.4 Ecotect solar thermal simulation.……………………………….....................72

iv

4.5 Design Builder solar thermal simulation...........................................................77
4.6 Airpak simulation model…………….…………………................................82
4.7 Ecotect lighting simulation…........................................................................... 96
4.8 3d max lighting simulation…………............................................................ 101

Chapter 5 Energy Saving integrated façade simulation Analysis................................102
5.1 Solar power economic benefits analysis......................................................... 102
5.2 Optimal shading distance and optimal PV performance…………….............103
5.3 solar thermal simulation analysis……………………………….....................113
5.4 CFD simulation analysis ……………….........................................................116
5.5Lighting simulation analysis……….……….………...................................120

Chapter 6 Conclusion & Future Work……………………........................................124
6.1 Conclusion…………………………………..…………………………….124
6.2 Suggestion and future work……………………………………………..…...132

Bibliography .....................................................................................................................136

v

List of Tables
Table 1.1 organization of this thesis.......................................................................................3
Table 1.2 organization of this thesis.....................................................................................6
Table 2.1 modules tilt angle.................................................................................................18
Table 2.2 type of Solar cell.................................................................................................21
Table 2.3 Case study1 Case1 Solar factory………………………………………………23
Table 2.4 Case study2 Office World ……………………………………………………24
Table 2.5 Case study3 California Academy of Science…………………………………25
Table 3.1 working schedule................................................................................................ 45
Table 4.1 Weather data for Hong Kong……………..…...…………………….……….....54
Table 4.2 Hong Kong solar irradiation………..……………………..……………….......54
Table 4.3 modules tilt angle………………………………………….…..……………….57
Table 4.4 Solar irradiation overlap reduce factor %............................................................64
Table 4.5 No overlaps PV system annual energy yield calculator…………...……...........67
Table 4.6 Overlaps PV system annual energy yield calculator...........................................68
Table 4.7 Ecotect No shading radiation analyses…………………...…………………….74
Table 4.8 Ecotect Window shading radiation analyses………………………………..….75
Table 4.4 Ecotect PV shading radiation analyses…………………………………………76
Table 5.1 Solar irradiation hour in different angles ………………………………..……104
Table 5.2 Solar irradiation hour in different angles ………………………………….….105
Table.5.3 Solar gain exterior window in different number of PV on the façade……….106
Table.5.4 Solar irradiation overlap reduce factor………………………………….…….109
Table 5.5 Ecotect Solar Radiation……………………………………………………….114
Table 6.1Energy saving integrated façade design ………………………………………125

vi

List of Figures
Figure 1.1 Earth 、Natural recourse 、Human life……………………………………....3
Figure 2.1 BIPV curtain wall……………………………………...………………….......8
Figure 2.2 Semi- transparent PV glazing replaces traditional glazing………………….......8
Figure 2.3 A lightweight building integrated photovoltaic system…………………….....10
Figure 2.4 pitched roof BIPV……………………………………………………………..11
Figure 2.5 Freiburg facade with transparent modules and shadowing modules………..…12
Figure 2.6 Spire Provides BIPV Systems to Chicago's Green Commercial Center……..12
Figure 2.7 BIPV to replace the part of wall……………………………………………..13
Figure 2.8 Attic space with BIPV roof glazing………………………………………….14
Figure 2.9 BIPV Glazing………………………………………………………………...14
Figure 2.10 An example of BIPV…………………………………………………………15
Figure 2.11 flat roof BIPV…………………………………………………………….......16
Figure 2.12 Thin film solar cell…………………….……………………………….…...21
Figure 2.13 Casel solar factory I…………………….…………………………………...23
Figure 2.14 Casel solar factory II…………………….…………………………………..23
Figure 2.15 office world……………………………….…………………………………24
Figure 2.16 PV shading1……………………………….…………………………………25
Figure 2.17 PV shading2………………………………………….………………………25
Figure 2.18 California Academic of Science 1………………………………………...….25
Figure 2.19 California Academic of Science 2………………………………………...….26
Figure 2.20 California Academic of Science 3………………………………………...….26
Figure 2.21 Sun shade can block direct sun light……………………………………...….28
Figure 2.27 hot air flow up in middle layer……………………………………………...29
Figure 2.28 Typical light shelf………………………………………………………….....31
Figure 2.29 light guide concept……………………………….………………………....32
Figure 2.30 opening and wind speed…………………………………….………………33
Figure 2.31 Opening position and wind…………………………………………………...34
Figure 2.32 opening type and wind……………………………….……………………..35
Figure 2.33 sun shading and wind……………………………….………………………36
Figure 2.34 wind wall and wind…………………………………….…………………...38
Figure 3.1 Air curtain systems…………………………………….……………………..40
Figure 3.2 scope of research 1…………………………………………………………….41
Figure 3.3 scope of research 2………………………………………………….………..42

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Figure 3.4 scope of research 3………………………………………………….………43
Figure 3.5 working schedule…………………………………………………….……..47
Figure 4.1 Energy saving façade Concept……………………………………….……..48
Figure 4.2 Energy saving façade design plan…………………………….….…………49
Figure 4.3 Energy saving façade design elevation and section…………….….…………50
Figure 4.4 Energy saving façade design rear elevation………………….……….……...50
Figure 4.5 Energy saving façade design perspective………………….………….………51
Figure 4.6 Energy saving façade design structure detail….…….………….………52
Figure 4.7 Single standard office spaces………………………………………………….56
Figure 4.8 Energy saving façade simulation plan…………………….………….……..58
Figure 4.9 Energy saving façade simulation south elevation………….……….….……58
Figure 4.10 Energy saving façade simulation south Section………………………..……59
Figure 4.11 Energy saving façade south 3D perspective………………………….….…..59
Figure 4.12 solar modules………………………………..……………………….….…...61
Figure 4.13 Sun and sun shading overlap angle………………………………………….62
Figure 4.14 Hong Kong Sun shading chart………………….…………………………….63
Figure 4.15 Hong Kong daily solar irradiation………..……………………………..64
Figure 4.16 Fan…………………………………………………………………….……70
Figure 4.17 Ecotect radiation analysis no shading model………………………….……73
Figure 4.18 Ecotect radiation analysis windows shading model………………….…….73
Figure 4.19 Ecotect radiation analyses PV shading model……………………….……..73
Figure 4.20 Ecotect No shading radiation analyses ……………………………….……74
Figure 4.21 Ecotect window shading radiation analyses…………………….…….……75
Figure 4.22 Ecotect PV shading radiation analyses …………………………….………76
Figure 4.23 Design builder No shading model…………………………………….……77
Figure 4.24 Design builder window shading model………………………………..……78
Figure 4.25 Design builder PV shading model……………………………...…….…….78
Figure 4.26 Design builder No shading simulation………………………………….….79
Figure 4.27 Design builder windows shading simulation…………………………….…80
Figure 4.28 Design builder PV shading simulation……………………………………..81
Figure 4.29 Airpak simulation model section setting point…height……………….…….83
Figure 4.30 Airpak simulation model plan setting point deep…………………….……..83
Figure 4.31 Airpak simulation model No shading……………………………….………84
Figure 4.32 Airpak simulation model Window shading………………………….…...…84
Figure 4.33 Airpak simulation model solar shading……………………………….…….84

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Figure 4.34Airpak simulation model PV shading with fan……………………..….……85
Figure 4.35 Airpak speed simulation –no Fan…………………………………..….……85
Figure 4.36 Airpak speed simulation –window shading………………………………...86
Figure 4.37 Airpak speed simulation –PV shading with fan……………………………86
Figure 4.38 Airpak speed simulation – PV shading with fan…………………..…….…87
Figure 4.39 Airpak pressure simulation horizontal setting point data…………….…….87
Figure 4.40 Airpak pressure simulation vertical setting point data……………….…….88
Figure 4.41 Airpak turbulence current – no fan…………………………………………89
Figure 4.42 Airpak turbulence current – with fan……………………………….………89
Figure 4.43 Airpak pressure simulation- No fan……………………………….………..90
Figure 4.44 Airpak pressure simulation- window shading………………...……….……90
Figure 4.45 Airpak pressure simulation- solar shading………………………….………91
Figure 4.46 Airpak pressure simulation- PV shading with fan………………….……….91
Figure 4.47Airpak pressure simulation horizontal setting point……………..….………92
Figure 4.48 Airpak pressure simulation vertical setting point……………….…….…….92
Figure 4.49 Airpak temperature simulation-no fan…………………………….…..…….93
Figure 4.50 Airpak temperature simulation- window shading………………….….……93
Figure 4.51 Airpak temperature simulation- solar shading……………………….….….94
Figure 4.52 Airpak temperature simulation- PV shading with fan…………….……...…94
Figure 4.53 Airpak temperature simulation horizontal setting point…………….………95
Figure 4.54 Airpak temperature simulation vertical setting point……………….………95
Figure 4.55 Ecotect simulation model no shading……………………………….………96
Figure 4.56 Ecotect simulation model window shading……………………….…….…..97
Figure 4.57 Ecotect simulation model solar shading………………………….…………97
Figure 4.58 Ecotect simulation no shading…………………………………….….……..98
Figure 4.59 Ecotect simulation window shading……………………………….….……..99
Figure 4.60 Ecotect simulation solar shading………………………………….….……..100
Figure 4.61 3D max lighting simulations-no shading………………………….….……..101
Figure 4.62 3D max lighting simulations-with shading……………………….…..…….101
Figure 5.1 Different angle Hong Kong Sun shading chart (June to December)……..…104
Figure 5.2 optimal distance & optimal PV performance……………………….…….106
Figure 5.3 4PV Sun and sun shading overlap angle……………………………….….…107
Figure 5.4 61degreeHong Kong Sun shading chart (June to December) ……….………108
Figure 5.5 Hong Kong daily solar irradiation…………………………………….…...…109
Figure 5.6 Ecotect Solar Radiation (KBtu) …………………………………….….……113

ix

Figure 5.7 Design Builder Solar Radiation (KBtu) ……………………………..………115
Figure 5.8 speed simulation horizontal setting points’ data analysis……………….……116
Figure 5.9 speed simulation vertical setting points’ data analysis…….……..…….…117
Figure 5.10 pressure simulation horizontal setting points’ data analysis……..….….…118
Figure 5.11 pressure simulation vertical setting points’ data analysis………..…….…118
Figure 5.12 temperature simulation horizontal setting points’ data analysis……..….…119
Figure 5.13 temperature simulation vertical setting points’ data analysis…….………..120
Figure 5.14 lighting simulation on March 21/ 12pm…………….…………………..…..121
Figure 5.15 lighting simulation on June 21/ 12pm……………..…………………..……122
Figure 5.16 lighting simulation on December 21/ 12pm.............................................…..123
Figure 6.1 Energy saving façade PV Modules……………..……………………..……126
Figure 6.2 Energy saving façade 3D model………………………..……………….…126
Figure 6.3 Energy saving façade 3D detail……………………….……………….……127
Figure 6.4 Energy saving façade rear elevation ………………….………………...……127
Figure 6.5 Energy saving façade 3D detail 2…………………….………………………128
Figure 6.6 lighting reflection board concept……………………..……………………...133
Figure 6.7 semi transparent photovoltaic window shading…..……………………….134

x

Abstract

Global warming is a serious problem we face today. Overusing fossil fuels not only emits
wasteful gas and pollutes our atmosphere but also produces greenhouse gases that lead to
global warming. In response to the energy crisis and global warming, solar energy is a
source of energy that can be used without depleting. Solar energy is quiet and produces
no toxic emission or greenhouse gas. It is an ideal energy we can use instead of fossil fuel
and stop global warming. One of the methods to use renewable solar energy is Building
Integrated Photovoltaic (BIPV). The basic frame of energy saving integrated façade can
integrate with manipulation of solar energy, heat insulation efficiency, ambient lighting,
transmit lighting and ventilation efficiency on the photovoltaic (PV) sun shading and fan.
The power that is needed for the fan control results from the collection of the PV sun
shading. PV shading is also a sustainable insolation prevention system for tropical zones.
This thesis demonstrates that an air curtain is an effective thermal strategy that supports
the new age of low-energy, zero-energy sustainable energy saving architecture.

This research included collecting and arranging data to support the basic theory and to
frame the design standard of the solar integrated façade BIPV, analysis of successful

xi

American and overseas case studies of BIPV for the standard and reference for the design
of the energy saving integrated façade. Ecotect and computational fluid dynamics (CFD)
are used to examine the designing productions for make up the reliable reason and the
reference emendation to support the designing productions. Estimates and discussion of
energy saving integrated façade: This study arranges and analysis the experiments results
to estimate the entirety designing productions to provide a reference for architecture
designer. The goal is to develop a good example of BIPV, low-energy façade in
architecture design and to suggest the trends for continuing research.

PV sun shadings help airflow substantially more efficiently than normal window shading.
After placing the fan in the air gap the airflow is even better. The energy saving integrated
façade greatly improved the insulation of the best test experimental configuration. An
energy saving integrated façade can block heat from the sun so the indoor layer can have a
bigger opening, improving the ambient indoor lighting and ultimately creating more
comfortable work spaces.

1

Chapter 1 Introduction

1.1 Motivation and background
Most people believe that global warming is a major crisis we face today, and that these
serious problems are caused by humans’ excessive use of energy. Overusing fossil fuels
not only emits waste gas and pollutes our atmosphere but also produces green house gas
that causes global warming. Nowadays, we use too many fossil fuels in our life. All
fossil fuels and biomasses consist of carbon and hydrogen atoms. Burning coal
produces carbon dioxide. Carbon dioxide is the main green house gas that causes global
warming. Global warming causes very serious problems in our earth: extreme weather
(warmer waters and more hurricanes, increased probability and intensity of droughts and
heat waves, economic consequences, spread of disease and polar ice caps melting). If
we can’t resolve this momentous problem people will have challenging times ahead to
survive on Earth.
To stop burning coal or fossil fuel is impossible but exploiting new resources is an
inevitable method. In response to the energy crisis and global warming, solar energy is a
source of energy that can be used without energy depleting. Solar energy is quiet and

2

produces no toxic emission or green house gas. It offers great potential to bridle and
perform cosmic source of free energy. It is the ideal energies we can use to substitute
fossil fuel and to stop global warming.
Photovoltaic (PV) is one of the best methods to apply solar energy. It is the field of new
technology using solar cells for energy by converting sunlight directly into electricity.
Basic on human healthy, comfortable and safety, to reduce the damage of overusing our
resource and zealous to develop new energy for our sustainability environment is the
main mission goal for building science and also the main issue we want to discus in this
study.

3

Figure1.1 Research study context

1.2 Original work

Before initiating this study, a literature review of relevant books and data was performed.

Table1.1Organisation of this thesis
Author book content
Henemann BIPV: Built- in Solar
Energy
This book gives a general idea of how to build house with
solar energy. It introduces from BIPV components,
architectural integration, and system design to Installation
and maintenance.
Eiffert, Patr
ina
Building-Integrated Phot
ovoltaic Designs for Co
mmercial and Institution
al
Introduction of Building-Integrated Photovoltaic
Designs using in Commercial and Institutional building.
It gives case study and examples.

4

Table1.1: Continued
Friedrich
Sick and
Thomas
Erge
Photovoltaic in
Buildings
Photovoltaic in Buildings is a book that introduces
the method to use photovoltaic.
Klasus,
Danirls
The Technology of
Ecological Building
This book introduces the new technology of ecological
building. It also gives same case study about BIPV in
building.
Wigginton,
Michael;
Harris, Jude
Intelligent Skins It gives a new definition for architectural facade.
The concept of Intelligent skin is from human skin.
It actively controls through itself conformation to a
ttain the reaction capacity between inside and outsid
e, and the capability of ideal comfort condition.
Gerhard
Hausladen,
Michael de
Sadanha,
petra liedl
Climate Design Different Climate should have different method of
design. It shows us using the different experiment on
airflow to design the opening.
Dean
Hawkes,
Waye Foster
Energy Efficient
Buildings
It Introduces case studies of Energy Efficient Buildings.
It gives a great idea to design a Energy Efficient
Buildings.
Solar
Energy
International
Photovoltaics: design
and installation manual
This manual introduces the BIPV design and installation
using the renewable energy.
Deo K.
Prasad,Dr.
Mark Snow
Designing with solar
power
This is a source book for design BIPV. It inspires
designer or professionals to think about photovoltaic as
an energy-producing building material, and to
incorporate this energy source whenever possible.

5

1.3 Organization of This Thesis

The section is about the brief description of each chapter. The two main directions of
this study include case design and a comprehensive simulation evaluation. The
organization of this thesis is composed of an introduction, research background, energy
saving integrated façade study and design, energy saving integrated façade simulation
and experiment, energy saving integrated façade analyze and evaluation and conclusion
and future research.

6

Table1.2 Organization of this Thesis
Chapter Name content

1

introduction
This chapter is focus on research motivation and backgroun
d description. The original work is about bibliographic sour
ce for my research.

2
Research
background
This chapter is focus on basic data gathering and understan
ds; I take reference on this chapter for basic design.

3

Energy saving
integrated façade
study and design
After case study, this chapter focuses on using those succes
sful case studies for design reference. The design will inte
grate solar PV, window, solar shade and wall.

4

Energy saving inte
grated façade
simulation and
experiment
After the main architectural design chapter 4 is focus on m
odel simulation, this study will use Ecotect for lighting and
solar thermal simulation and CFD for airflow simulation.

5

Energy saving
integrated façade
analyze and
evaluation
After the simulation and experiment, chapter 5 is focus on
data analyze, evaluation and compare. Then it can give fee
d back to the original design.

6

Conclusion and
future research.
After all of those design, analyze and feedback. The last
chapter gives a conclusion and suggestion of solar integrate
d façade design and future research.

7

Chapter 2 Research background

2.1 BIPV
BIPV, Building integrated photovoltaic (BIPV), is a design method to use photovoltaic
materials replacing traditional building material in part of building. Because of the
energy crisis these days, the potential threat of global warming, BIPV is proving to be an
image of energy savings in housing, commercial and industrial buildings. BIPV is a
new dimension to energy conscious design, the photovoltaic modules replace traditional
materials in building and create an ambient inside temperate, it also can protect against
the weather from wind and rain. Semi- transparent PV cells have the advantage that
their transparency can let sun light transmit into the building or can provide partial shade.
(Henemann 2008 p14, 16-19)
Photovoltaic (PV) arrays of solar cells produce electricity directly from sunlight. (Mark Z.
Jacobson, 2009) The application of using PV in the building called Building Integrated
Photovoltaic (BIPV)
In this section we are going to discuss more about BIPV: the advantage of BIPV, forms of
BIPV, the difference between BIPV and Building Mounted Photovoltaic (BMPV) and the
major design issues with BIPV.

8

Figure2.1: BIPV curtain wall, Tainan county government http://www.tainan.gov.tw/cht/reduceco/index.aspx

Figure2.2: Semi- transparent PV glazing replaces traditional glazing Tainan county government
http://www.tainan.gov.tw/cht/reduceco/index.aspx

9

2.1.1 Advantages of BIPV
From energy conservation, environmental and global point of view, solar energy has
many green advantages.
1. It’s quiet, produces no toxic emission or green house gas, and dismisses no harmful
scrap.
2. PV modules can service at least 30 years. It has potential of becoming a major clean
energy source of the future.
From a financial, architectural and technical point of view:
1. It can provide electricity power during utility peak time requirement.
2. It can be in replace conventional building material and give more pay back with solar
energy.
3. PV can be set on building wall, roof or part of the building, It does not need extras
land use or additional infrastructure installations.
4. It provides new technology and innovative image concept design for architecture
façade.

10

2.1.2 Forms of BIPV
The common method to integrate photovoltaic on the building is to set PV panels on the
elevation or roof of the building. There are several forms we can use of BIPV such as
roof, facade and glazing.
Roofs
There are two kind of BIPV roofs, flat roof and pitched roof.

Figure2.3: A lightweight building integrated photovoltaic system, (Architecweb,
http://www.architechweb.com/ArticleDetails/tabid/254/ArticleID/5605/Default.aspx)
The PV modules attach on pitch roof look like multiple roof tiles. The PV modules not
only can protect the roof out of insulation and membranes from ultraviolet rays and water
degradation but also extend the roof life. Eiffert 2000, p60-61)

11

Figure2.4: pitched roof BIPV (CHC
http://www.iea-shc.org/countries/reports/images/Alouette%20home.jpg)

Façade
PV design has the image of new technology, sustainability and innovative concept. It can
give old buildings a new look. These modules are mounted on the facade of the building,
over the existing structure, which can increase the appeal of the building and its resale
value. (Henemann 2008 p14, 16-19)

12

Figure2.5: Freiburg facade with transparent modules and shadowing modules (Solar fabric,
http://www.solar-fabrik.com/modules-systems/technology/module-production/?L=1)

Figure2.6: Spire Provides BIPV Systems to Chicago's Green Commercial Center (spire solar,
http://www.renewableenergyworld.com/rea/partner/spire-corporation-2558/news?page=18)

13

Figure2.7: BIPV to replace the part of wall. （Newenergynews,
,http://newenergynews.blogspot.com/2008/09/solarbuilding-bricks.html ）

Glazing
Semi transparent photovoltaic modules can be installed on window or similar materials,
such as windows and skylights.

14

Figure2.8: Attic space with BIPV roof glazing (Canada Mortgage and Housing Corporation,
http://www.cmhc-schl.gc.ca/en/co/maho/enefcosa/images/8.jpg)

Figure2.9: BIPV Glazing (Atlantis Energy System Inc)

15

2.1.3 BIPV vs. BMPV
Building Integrated Photovoltaic, BIPV, uses PV as an integral part of building envelope.
This is a new architecture space thought, construction material revolution. BIPV building
is not just an energy generating machine but it can be a self-contained and self-sufficient
source. When PV install in the building as a part of material, it can generate electricity by
leveraging sun light. Tree leaves grown on the tree help the tree output photosynthesis
and manufacture nutrient. PV integrated within the building envelope absorbs sun light
and converts it into electricity. The concept is very similar to the tree’s leaves.

Figure2.10: An example of BIPV, which is installed at an REI store in Boulder, CO.
(Photo: Scott Dressel-Martin) http://todaysfacilitymanager.com/facilityblog/2009/04/page/2

16

PV integrated within the building envelope absorbs sun light and converts it into
electricity. In this case, PV is not part of the building or façade material. It is like we use
accessory on our dressing.

Figure2.11: flat roof BIPV (PGLE,http://www.gple.com.tw/im/solar_10kw.jpg)
The difference between BIPV & BMPV is PV modules or PV panels are implemented to
replace conventional building materials as a part of the building. The broad definition for
BIPV includes BMPV; the scope of this study is limited to BIPV technologies and case
studies.

17

2.1.4 BIPV Design Issue
Environmental and structural considerations must be factored into BIPV designs. To
achieve the highest possible performance for the BIPV system, we also have to consider
the solar energy systems such as solar access, system orientation and tilt, electrical
characteristics, and system sizing.

Solar access
It’s about the potential electrical output of a BIPV system. For best performance, PV
modules need to face directly to the sun, if something such as tree or building shade on
the PV, the PV efficiency will reduce. We have to consider surrounding features:
building, tree, etc.
System Orientation
To have efficient solar access and power we have to consider the tilt angle of the array
relative to the location and building site.
Photovoltaic modules when they facing the sun directly they can generate maximum
power. “This ideal over the course of the year, thus maximizing annual energy production,
is facing due south”. (Oksolar company 2010). This only happened in good weather
condition, if the weather is bad facing south maybe not the best orientation.

18

Module title angle
Module tilt angle should point directly at the sun to generate the maximum solar power.
As we know the solar modules installations are fixed to a permanent structure. Solar
power in the winter is most weak, so we should be tilted for optimum winter performance.
“If the system power production is adequate in the winter, it will be satisfactory during
the rest of the year. The module tilt angle is measured between the solar modules and the
ground.” (Oksolar company 2010)
Table2.1 modules tilt angle (Oksolar.com 2010)
Latitude Site Tilt Angle
0-15° 15º
15-25° SAME AS Latitude
25-30° add 5° to local latitude
30-35° add 10° to local latitude
35-40° add 15° to local latitude
40° + add 20° to local latitude

System Sizing
This study has to consider the whole building consumption, architectural considerations,
and economic factors for choose a BIPV type and sizing a system. Other factors in
system sizing are PV array size, PV modules type, and available sunlight.
PV array size determinate the capacity power can be generate a year. PV modules types

19

affect the efficiency of the PV modules. Available sunlight is the power source the PV
system need for generate power.

2.2 Application of solar power
On this section we discuss the different types of solar cell, solar power system and the
installation of solar power system. The main mission to set the power solar system is to
achieve the maximum potential electrical output of a BIPV system.

2.2.1 Solar cell
“A photovoltaic cell is the smallest semi-conductor element within a PV module to
perform the immediate conversion of light into electrical energy”. (Friedrich Sick and
Thomas Erge, 1996)
Photovoltaic, PV, work by absorb sunlight and convert directly into electricity.
“The term“photo” means light and “voltaic,” electricity. A photovoltaic (PV) cell, also
known as “solar cell,”is a semiconductor device that generates electricity when light falls
on it”. ( Olivia Mah,1998)

20

2.2.2 Types of photovoltaic cell
Crystalline solar cell
Crystalline solar cell, made of crystal silicon, is the most common cell we use for PV .
On the market we have different type of crystalline solar cell such as Monocrystalline,
Multicrystalline and GaAs. The manufacture procedure and material composition are
different. “The current market leader in solar panel efficiency (measured by energy
conversion ratio) is SunPower, a San Jose based company. Sunpower's cells have a
conversion ratio of 23.4%, well above the market average of 12-18 %”( Caltech
Researchers Create Highly Absorbing, 2010). So they have different practical efficiency
and prime cost. Different types of crystalline solar cell have different practical
efficiency and manufacture price. (See table2.2). I n this study I selected the
Multicrystalline solar cell for the BIPV design, because it is widespread, more
affordable and good practical efficiency.
Thin- film solar cells
The common thin film solar cell is made of amorphous silicon. It is lower cost, uses
less material and is a faster manufacturing process. The advantage of thin film solar cell
is it doesn’t need large energy to produce and the disadvantage is the efficiency is low.

21

This section is just introduced that there are other kind of solar cell, but in this study we
are not going to use thin film solar cell in the energy saving integrated façade.

Figure 2.12: Thin film solar cell. Thomas net, http://www.thomasnet.com/articles/image/thin-film.jpg

Table2.2 type of Solar cell (jih ji hsiao zang1999)
Type Monocrystalline Multicrystalline
Amorphous
silicon
GaAS CIGS
practical
Efficiency
16 －17％ 13－15％ 8 ％ 18％ 17.6 ％
Laboratory
Efficiency
24％ 17.2 ％ 14.5 ％ 33.3 ％－
Manufacture

easy moderate difficult easy moderate
Material
resource
moderate moderate difficult easy easy

22

Table2.2: Continued
environmental
pollution
Low Low Low high high
durability

high high moderate high high
Prime cost high moderate high Very high high

2.3 BIPV case study
There are many built examples of energy saving façade around the world. This study
selected three more emblematic and interrelated examples or systems for case study. 1.
Casel solar factory use PV on the façade and adjustable window shading. It is a classic
energy saving façade using PV. 2. Office world in Switzerland is a case that uses PV on
the window shading. It also can be adjusted on different season. 3. California Academic
of Science is important because it uses semitransparent PV modules on the overhand. It is
a recent North America application of BIPV.

23

Table2.3 Case study1 Case1 Solar factory
No.1 Case1 Solar factory(Klasus, Danirls
1997)
Type of case PV Facade
Image

Figure 2.13 Casel solar factory 1(Klasus, Danirls 1997)
Introduction Location: German Freiburg
Architect: Rolf + Horz
Detail
Image

Figure 2.14 Casel solar factory II
(Klasus, Danirls 1997)
note This case use PV on the building façade and glazing photovoltaic. PVs not only
absorb and convert sun light to electricity but also can use as insulation material.

24

Table2.3: Continued
Remark

The thick of Crystalline solar cell is 0.4 mm, the size is from10x10cm to 15x15 cm.
PV modules can directly seal with silicon on the glass. Depend on the different
semi-transparent PV the transparent rate can be 4% to 30%.

Table2.4 Case study2 Office World
NO.2 Case2 Office World
(Klasus ,1997)
Type of case PV shading
Image

Figure 2.15 office world (Klasus ,1997)
Introduction contractor: Swissbau 93, Mwsse Basel
Location: Switzerland
Architect: Burckhardt + Partner
Electrical Engineer: Solution AG, Colt International AG
Completed date:1993

25

Table2.4: Continued
Detail
Image

Figure 2.16 PV shading1 (Klasus ,1997)
There is less solar radiation in winter; they
turn reverse the PV shading to get natural light
and heat from the sun.

Figure 2.17 PV shading 2(Klasus ,1997)
There are too much solar radiation on summer,
the PV shading not only insulate the sun heat
but also convert it to electricity.
note This case integrated PV and window shading. They set PV on the top of window shading and
reflect material on the button, when the sun location angle change, the indoor can block the sun
heat and get electricity get light and electricity. When the indoor illumination is not enough, they
turn reverse the PV shading to get light. This is the prototype of PV integrated window shading.

Table2.5 Case study3 California Academy of Science
NO.3 Case3 California Academy of Science Type of case PV overhand
Image

Figure 2.18 California Academic of Science1(Photograph taken by Taiuey Huang)

26

Table2.5: Continued
Introduction contractor: California government
Location: San Francisco
Architect: Renzo Piano
Completed date:2008
Detail
Image

Figure 2.19 California Academic of
Science2 (Photograph taken by Taiuey
Huang)

There is less solar radiation in winter;
they turn reverse the PV shading to get
natural light and heat from the sun.

Figure 2.20 California Academic of Science3
(Photograph taken by Taiuey Huang)

There are too much solar radiation on summer,
the PV shading not only insulate the sun heat
but also convert it to electricity.
note This case integrated PV and window shading. They set PV on the top of window shading
and reflect material on the button, when the sun location angle change, the indoor can
block the sun heat and get electricity get light and electricity. When the indoor
illumination is not enough, they turn reverse the PV shading to get light. This is the
prototype of PV integrated window shading.

27

2.4 Building insulation efficiency
The main purpose of building insulation is to insulate too cold or too hot temperature
out of the building and control the indoor temperature for human physical comfort. If
the building insulation efficiency is bad we need to use more energy load to cool our
building. Furthermore, the increase of using energy not only emits more Co2 but also it
causes global warming. So building insulation is a crucial problem we need to take care.
The main source of heat transfer is radiant energy, in this study, energy saving integrated
facade using PV shading can block radiant heat from the sun and decrease cooling load.
PV shading is kind of Insulation system and Double skin maybe a good effective thermal
strategy.

2.4.1 Insulation of sun shade
The main effective function to set sun shade on the window is to keep out sun radiation.
Sun shade can absorb and reflect great quantities of solar short wave then release with
solar long wave as heat energy. So it is a good method to insulate heat from the sun.

28

Figure 2.21 Sun shade can block direct sun light. Keep the sun heat out of the window
http://shlelang.com/product_show.asp?ID=86

2.4.2 Insulation of double skin hot flow air
The insulation of double skin is composed of outer layer, middle later and internal layer.
When the sun radiation pass thought the outer layer, outer layer such as sun shade will
keep out the sun radiation and convert it to heat. The heat makes the middle layer hot air
flow up, when the temperature is different between indoors and out door, it will create
pressure and push the hot air up. Therefore, the middle layer hot air flow up draws low
temperature air in from the openings near the bottom.
After the sun shade absorbs the sun radiation the heat energy will remain on the sun

29

shade. The heat on the sun shade needs to convert to pass into the opening and get
inside. Most of the heat energy will flow up when they convert in the middle layer and
keep out from internal layer. The middle layer is a good idea to help the double skin
have natural convection.
According to Wigginton （2002, the experiment data shows that double skin having natural
convection in the middle layer reduce 76% of skin radiation and decrease the cooling
load.

Figure: 2.27hot air flow up in middle layer (Wigginton, 2002)

Hot air flow
Window
Air chimney

30

2.5 Ambition lighting efficiency
Housing for 21 century, we have to consider not only sustainable and energy efficiency
but also human health. Appropriate natural lighting brings human warm and hygiene
desire. A good lighting space can make the user feel comfortable and enhance working
efficiency. Furthermore, natural lighting can decrease the using of artificial lighting and
energy cost. Natural lighting is main lighting source we use at day time.

2.5.1 Method of Natural lighting
There are many ways to access the natural lighting, such as window day lighting, skylight,
light reflectors, light shelves.
Window
Window is most easy method to access the daylight. Depend on the different window size,
orientation, time of the day; season, and climate, window can demonstrate different
strength of daylight.
Skylight
Skylight is a very common way to admit daylight directly into indoor. Skylight admit
directly exposed to sunlight the whole day so they are more effective in providing natural
lighting than windows.

31

Light reflector
A light reflector is made of high reflecting material. It can reflect sun light into the
interior. “Once used extensively in office buildings, the adjustable light reflector is
seldom in use today having been supplanted by a combination of other methods in
concert with artificial illumination”. (Wikipedia, daylighting, 2010)
Light shelves
A light shelf is a horizontal light-reflecting overhang that helps daylight to access deep
into a building. It has a high-reflectance upper surface, normally it made of aluminum.
This high-reflectance is used to reflect daylight onto the ceiling and deeper into a space.
(Wikipedia, architectural lighting shelves, 2010)

Figure 2.28 Typical light shelfwww.pages.drexel.edu/~st96dmn3/opt/mdl.htm

32

2.5.2 Method of light guide
The main purpose to guide light is to use reflect shading reflect directly or indirectly light
into the building. Especially in the summer, the angle of the sun is high, only few directly
sun light can enter the building and make the indoor lack of lighting. So using light
guide panel and reflect material on the ceiling lead the light enter the building. It can
decrease using artificial lighting and energy load.
Therefore, using light guide method can guide the light enter the room but exclude light
heat. In the summer, too much directly sun light access to the building and heat our
space. If we can use the light guide method we can have a good lighting and save
energy.

Figure: 2.29 light guide concept （Huang 2004 ）
Window shading
Reflect able ceiling

33

2.6 Ventilation efficiency
The main purpose of natural ventilation is to bring fresh air into the building and take out
the polluted air. For instance, in the spring morning, when the outdoor air temperature is
lower than indoor temperature, natural ventilation can cool the indoor temperature and
decrease the HVAC load.

2.6.1 Opening and wind speed

Source OLGYAY(1992) content
Design with climate
Author: OLGYAY, VICTOR
publish: VAN NOSTRAND
REINHOLD
publish time: 1992
1. When the wind- in area larger than wind-out area, the
room wind speed is faster than outside.
2. When the wind-in area is larger than wind out opening
area, the speed is slow but it accelerates when going
out.
3. When the wind in and wind out opening area is the
same, indoor wind speed is a little bit fast than outside.

Different opening and airflow in & out.
Figure:2.30 opening and wind speed (Olgyay, 1992)

34

2.6.2 Opening position and wind
Source OLGYAY(1992) Content
Design with climate
Author: OLGYAY,
VICTOR
publish: VAN
NOSTRAND REINHOLD
publish time: 1992
Wind in opening
1. Height Win in opening, wind goes up.
2. Low win in opening, wind goes down.
3. Set the win in opening on the floor height. Wind goes on the
floor surface.
conclusion ：Wind in position affect directly to the wind route.
Wind out opening
1. Wind out opening near ceiling, wind goes down 。
2. Wind out opening in the middle of the wall ，wind goes down 。
3. Wind out opening near the floor, wind goes down 。
conclusion ： Wind out position not very important for the wind route.

Height airflow in opening airflow out opening near ceiling

Low airflow in opening airflow out opening near floor

airflow in opening near floor airflow out opening in the middle
Figure: 2.31 Opening position and wind (Olgyay 1992)

35

2.6.3 Opening type and wind

Source Olgyay(1992) Content
Design with climate
Author: OLGYAY, VICTOR
publish: VAN NOSTRAND
REINHOLD
publish time: 1992
The horizontal cross axle face up, make the wind goes up to
the ceiling. It’s not help for ventilation.
The horizontal cross axle face down, make the wind goes
down, the wind goes depend on the direction adjust on the
cross axle.
Fixed window blinds also affect the wind route.

horizontal cross axle face up

horizontal cross axle face up facedown window blinds

Figure:2.32 opening type and wind(Olgyay(1992)

36

2.6.4 Sun shading and wind

Source OLGYAY(1992) Content
Design with climate
Author: OLGYAY, VICTOR
publish: VAN NOSTRAND
REINHOLD
publish time: 1992
The same high of hangover can speed the ventilation.
The sun shading on the window helps to lead the wind enter
the room.
When they set a gap between sun shading and wall, it can
helps wind enter the room more directly and horizontal.

overhand

Sun shading sun shading with gap
Figure: 2.33 sun shading and wind (Olgyay1992)

37

2.6.5 Wind wall and opening
Source: Hamzah&YeangSdn(1998) Content
UMNO Menara
Author: T.R. Hamzah & Yeang
Sdn. Bhd.
publisher: 《DIALOGUE 》9 （18 ）
publish time: 1998
Window type affect the amount of enter wind.
Wind device can help wind ventilation.
Wind device can smooth the wind don’t decrease the
amount of ventilation.

Wind flow A become small a airflow as the x window
width.

When wind B does not vertical the window and enter
inside ，speed a is high than b.

The set of wind wall let more wind enter the room. If the
enter angle of A and B are less than 45
0
，the wind wall
helps C enter the room is larger than a and b.

When the wind angle is up and down 900, the wind wall can
set up and down the window to increase the wind quantity.

38

The wind wall set in the middle of the window can smooth
the wind but not decrease the wind quantity.

Figure:2.34 wind wall and wind ,
Hamzah&YeangSdn(1998)

39

Chapter 3 Research Scope, Objectives, Procedure and Method

3.1 Scope of objective
The main concept of Energy saving facade is to use photovoltaic materials replacing
conventional building materials in parts of the window shading.
This study is proposing to replace a sunshade with a PV sunshade. PV sunshade not only
has the advantage of sunshade but also it can use the sun heart converted to electricity
power.
This paper shows the method and procedure to design Energy saving facade also provides
the comprehensive analysis of energy conservation in the integrated building facade.
Hypothesis: Double skin is an effective thermal strategy.

1. Solar energy
This envelope system is composed of Sun shading with Photovoltaic panels and
fans. The PV panels generate electric power and supply for the fans. Fans start to
operate and pump the air up.

2. Heat insulation efficiency
Sun shading with Photovoltaic panels also act like wind deflector. They insulated
sun heat and fans conduct hot air to go up.

40

3. Operable windows and ventilation
We can open the top window and let hot air flowing up. The air curtain system also
helps to pump out hot air. On the other side we can open the upper window to
enhance the ventilation efficiency.
This air curtain system will increase façade thermal insulation and reduce HVAC
energy load. It also improves natural ventilation efficiency.

Figure: 3.1 Air curtain systems
Through this study I am hoping to find out the energy saves in this Energy saving
Integrated Façade system. It can achieve the concept of low-energy, Zero-energy
sustainable energy saving architecture in the neo age.

41

3.2 scope of research
The research scope of Energy Saving integrated Façade focus on integrated PV into the
building façade. It is crucial to understand the best efficiency and method to applicant PV
on the building façade. BIPV application and contraction will discuss in this study.

Figure: 3.2 scope of research 1

Energy saving
integrated
Façade
BIPV
Set
Location
Angle
Construction
Material
Compose
Operate
Others
Maintain
Benefit
Code
Scope of research

42

Building Insulation is the other issue in this study. Energy saving integrated façade use
PV sunshade replace traditional sunshade to create more energy benefit. This part of the
study focusses on the window, double skin and ambition lighting.

Figure: 3.3 scope of research 2

Natural ventilation and the tectonic of the construction are also important issue that we
are going to discuss in this study.
Energy saving
integrated Façade
Insulation
Window
Shading
Glass
Double
Skin
Middle layer
Air flow
Insulation
material
Natural
lighting
Natural lighting
Window
Shading
Guide light
Opening
Reflect panel
Scope of research

43

Figure: 3.4 scope of research 3

Energy saving
integrated Façade
Ventilation
Soundproof
Material
Insulation
Wind
Wind wall
Opening
CFD
Air path
Speed
Aeration
Pressure
Flow
Mechanical
Tectonic
Façade & solar
shade
Façade maintain
Solar shade &
window
Soundproof
material
insulation
Scope of research

44

3.3 Research Procedure and Method
The major steps I will do to accomplish the research portion of my thesis project are as
follow:

1. Reference, arrangement: The main purpose in this procedure is to collect and
rearrange the data in order to support the basic theory and to show the design
standard of BIPV.
2. Design the Energy saving integrated façade.
3. The Calculation plan of BIPV: This procedure is going to use Ecotect for on
energy efficiency and lighting analyzing and CFD to air flow between indoor
and outdoor.
4. Examine and simulate the thermal comfort, lighting and wind on the solar
intergraded façade.
5. The evaluation and discussion: This procedure is mainly to simulate the wind,
thermal comfort and lighting on the solar intergraded facade , yet to provide a
reference as planning guide for architecture designers.
6. Conclusion and suggestion: To state an excellent example of BIPV on
low-energy, Zero-energy sustainable energy saves architecture design.

45

3.3.1 Energy saving integrated façade BIPV design
I take reference base on chapter 2 and those case studies to design the solar integrated
façade. This study uses Autodesk AutoCAD to design the project. Autodesk AutoCAD
is broadly used on architectural design. It is very efficiency and fast. Plan, elevation,
section and detail will show as architectural drawing.

3.3.2 Solar thermal simulation
One of the critical aspects of this study was to understand the thermal performance of
solar integrated façade that was designed in this study. This study will use Autodesk
Ecotect to analysis the solar thermal. Ecotect is relatively new software for energy
efficiency design; it can simulate thermal comfort and lighting. Ecotect is powerful
analysis and simulation tools for architects and designer to design more energy efficient
and sustainable design.

46

3.3.3Lighting simulation
After set those solar device on the façade will influence the ambient natural lighting.
This is important to study how the lighting performance does after set up that solar device.
This study uses Autodesk 3D studio lighting engine to simulate the lighting.

3.3.4 Computational fluid dynamics simulation
The other critical aspects of this study were to understand the airflow performance of
solar integrated façade that was designed in this study. Using CFD simulation is very
important in this study; the goal of the design is to prove the hypothesis is work like the
original concept. CFD is the examination method to prove the air curtain system works.
This study will use Design Builder CFD to model and simulate.

47

Figure: 3.5 working schedule

48

Chapter 4 Energy Saving Integrated Façade design and simulation

4.1 Energy saving integrated Façade design
4.1.1 Design concept
Using chapter two as design background data, I try to design the Energy saving Integrated
Façade that can conform to my study hypothesis, Double wall is an effective thermal
strategy. This new Energy saving Façade concept based on PV window shading with
integrated functions resulting in lower total energy consumption. The design is a single
office building in Hong Kong. Kyocera Ks20 is selected for PV modules, PV arrays face
to the south with tilt angle 30 degree. (design detail see chapter 4.2)

Figure: 4.1 Energy saving façade Concept

49

4.1.2 Design

Figure: 4.2 Energy saving façade design plan

Double Low E

50

Figure: 4.3 Energy saving façade design elevation and section

Figure: 4.4 Energy saving façade design rear elevation

51

Figure: 4.5 Energy saving façade design Perspective

52

Figure: 4.6 Energy saving façade Structure detail

Double Low E

53

4.2 Simulation model

4.2.1 Simulation environment
This study set the simulation site in a subtropical climate. In this area building need more
cooling energy than heating energy. And this Energy saving façade are design for
decrease building cooling energy load.
Selected Location: Hong Kong, 22°15′N 114°10′E.

4.2.2 Weather condition in Hong Kong
Hong Kong's climate is sub-tropical, tending towards temperate for nearly half the year.
During November and December there are pleasant breezes, plenty of sunshine and
comfortable temperatures. Many people regard these as the best months of the year.
January and February are cloudier, with occasional cold fronts followed by dry northerly
winds. It is not uncommon for temperatures to drop below 10 °C in urban areas. The
lowest temperature recorded at the Observatory is 0 °C , although sub-zero temperatures
and frost occur at times on high ground and in the New Territories.

54

Table 4.1 Weather data for Hong Kong( Source: Hong Kong Observatory

2008)
Month Jan Feb
Ma
r
Ap
r
May Jun Jul Aug Sep Oct Nov Dec Year
Average
high °C (°F)
18.6
(65)
18.6
(65)
21.5
(71)
25.1
(77)
28.4
(83)
30.4
(87)
31.3
(88)
31.1
(88)
30.2
(86)
27.7
(82)
24.0
(75)
20.3
(69)
25
(77)
Average low
°C (°F)
14.1
(57)
14.4
(58)
16.9
(62)
20.6
(69)
23.9
(75)
26.1
(79)
26.7
(80)
26.4
(80)
25.6
(78)
23.4
(74)
19.4
(67)
15.7
(60)
21
(70)
Precipitatio
n mm
(inches)
24
(0.94
)
52
(2.05
)
71
(2.8)
188
(7.4)
329
(12.95
)
388
(15.28
)
374
(14.72
)
444
(17.48
)
287
(11.3
)
151
(5.94
)
35
(1.38
)
34
(1.34
)
2,382
(93.78
)
Table 4.2 Hong Kong solar irradiation
Daily mean
solar irradiation (kWh/m
2
)
R
Jan 2.82
Feb 2.75
Mar 2.82
Apr 3.29
May 3.91
Jun 3.97
Jul 4.6
Aug 4.23
Sep 4.01
Oct 3.95
Nov 3.44
Dec 2.98
Total 44.77
1. Daily mean solar irradiation figures are based on data of King's Park weather
station.

55

Source: Electrical and Mechanical Services Department.
http://re.emsd.gov.hk/english/solar/solar_ph/solar_ph_cal.html

4.2.3 Simulation unit
Building type
Office building is a building that uses large opening and glass façade. This type of
building in subtropical area needs more cooling energy than heating energy.
Office Size: office standard Manual. (15x20x12 f) Window high 3 feet from the floor

This study picks up a general size for a small single reasonable office working space.
According to the office standard manual, the most common size for an office space is 15ft
x 20ft x 12ft.

56

Figure 4.7 Single standard office spaces
(http://www.tpsgc-pwgsc.gc.ca/biens-property/amng-ftp/images/oo_23_1.png)

PV module orientation
Photovoltaic modules when they facing the sun directly they can generate maximum
power. “This ideal over the course of the year, thus maximizing annual energy production,
is facing due south”. (Oksolar company 2010)
Module title angle
Module tilt angle should point directly at the sun to generate the maximum solar power.
As we know the solar modules installations are fixed to a permanent structure. Solar
Double Low E
window

57

power in the winter is most weak, so we should be tilted for optimum winter performance.
“If the system power production is adequate in the winter, it will be satisfactory during
the rest of the year. The module tilt angle is measured between the solar modules and the
ground.” (Oksolar company 2010)
Table4.3 modules tilt angle (Oksolar.com 2010)
Latitude Site Tilt Angle
0-15° 15º
15-25° SAME AS Latitude
25-30° add 5° to local latitude
30-35° add 10° to local latitude
35-40° add 15° to local latitude
40° + add 20° to local latitude
A module mounted in Hong Kong (latitude 23º should be tilted at approximately 23º from
horizontal, and should be faced due south.

58

Figure: 4.8 Energy saving façade simulation plan

Figure: 4.9 Energy saving façade simulation south elevation

59

Figure: 4.10 Energy saving façade simulation south Section

Figure: 4.11 Energy saving façade south 3D perspective

60

4.3 Solar power application
In this study I select Kyocera KS20 multicrystal Photovoltaic module to set on the solar
shading. The reason that Kyocera KS20 is selected for this study is because it is the most
common and spread type of multicrystal photovoltaic module we can find in the mark
today and the product size fit in design. Every single PV shading uses two Ks20. There
are 24 solar shadings on one office unit, so one office unite will use 48 units of KS20
modules. Total annual energy of PV module design Size （kW ）for one unit office is =
48x20 = 960kWh

61

Figure: 4.12 PV modules
http://www.kyocerasolar.com/products/

62

Figure: 4.13 Sun and sun shading overlap angle
Because of the different sun azimuth and altitude, only the first top 8 modules will not be
overlap at some point during the year, the other 40 modules will be overlapped on sun
angle more than 45 degree. According to the sun chart from Climate consultant, in Hong
Kong during winter time, the sun can point directly to the PV array without shading on 45
degree, over 45 degree part of sun light will occupied by the upper PV array.

63

Sun irradiation overlap & hour of sun irradiation
Compare with the sun shading chart (June to December) we can find out that sun
irradiation from 8:00 to 16:00 and above 45 degree cannot count it, because it was
overlap.

Figure: 4.14 Hong Kong Sun shading chart (June to December) Climate consultant

Strength of Sun irradiation & daily hour

Every hour in a day have different sun irradiation strength. The strength of sun irradiation
is less in the morning and sunset, more in the mid noon. PV modules Ks 20 can generate
20 kWh; this result was under test conditional of irradiance of 1kW/m2. So if the strength
is below than 1kW/m2, we need to reduce the percentage of anticipated energy collection.

64

Figure: 4.15 Hong Kong daily solar irradiation
http://www.weather.gov.hk/wxinfo/ts/display_element_solar_c.htm

According to Figure 4.12 and 4.13 we can have a result showing PV overlap reduce
factor.

Table 4.4 Solar irradiation overlap reduce factor %
Month Irradiation
hr
Irradiation hr% Irradiation strength
reduce%
Total reduce
factor%
December 8 hr 100% 90% 90%
January
November
7 hr 87.5% 60% 52.5%
February
October
6 hr 75% 50% 37.5%
March
September
4 hr 50% 45% 22.5%

65

Table 4.4:Continued
April
August
4hr 50% 45% 22.5%
May
July
1 hr 12.5% 40% 5%
June 1 hr 12.5% 40% 5%

This study provides two solar calculation formulas to verify and compare the result of the
annual energy yield.

Formula 1

Ep = Pas×Ha×K×365

Ep ：Annual Energy Yield （kWh ）
Pas ：PV module design Size （kW ）
Ha ：Site accumulation Solar irradiation （kWh/m2.day ）
K ：Correction factor or design factor
365：Days of year
NO overlaps PV
8 modules (20W)
Pas: 8 x 20W = 0.16 kW
Ha: 44.77/12= 3.56 kWh/m2. Day (from Table 4.2)
K= 0.75
EP = 0.16 x 3.56 x 0.75x 365 = 155.93 kWh

66

Overlaps PV (use solar reduce irradiation factor from table 4.3)
40 modules (20W)
Pas: 40 x 20W = 0.8 kW
Ha: Jan 2.82 x 52.5% =1.48
Feb 2.75x 37.5% =1.03
Mar 2.82x 22.5% =0.63
Apr3.29x22.5% =0.74
May3.91x5% =0.2
June 3.97x5% =0.2
Jul 4.6x 5% =0.23
Aug 4.23x 22.5% =0.95
Sep 4.01x22.5% =0.9
Oct 3.95x37.5% =1.48
Nov 3.44x52.5% =1.8
Dec 2.98x90%= 2.68
Jan to Dec = 12.32/12 =1.02 kWh/m2. Day
K= 0.75
EP = 0.8x 1.02x 0.75x 365= 224.8 kWh
Total Annual Energy Yield
155.93+224.8 = 380 kWh

67

Formula 2
PV system energy yield calculator
No overlaps PV system energy yield calculator
Peak power rating of PV module (P) = 20Wp
Number of modules (N) = 8
Overall loss/correction factor (Lf) = 0.75
Angle of tilt = 30 degrees
Table 4.5 No overlaps PV system annual energy yield calculator
Daily mean
solar irradiation
(kWh/m
2
)
Tilt factor to be used

Mean energy yield
per day
R Tf Eg
Jan 2.82 1.48 0.5kWh
Feb 2.75 1.31 0.43kWh
Mar 2.82 1.11 0.38kWh
Apr 3.29 0.93 0.37kWh
May 3.91 0.80 0.38kWh
Jun 3.97 0.73 0.35kWh
Jul 4.6 0.76 0.42kWh
Aug 4.23 0.88 0.45kWh
Sep 4.01 1.04 0.50kWh
Oct 3.95 1.24 0.59kWh
Nov 3.44 1.43 0.59kWh
Dec 2.98 1.54 0.55kWh
annual energy yield 167kWh
1. This is a simple calculator for appreciating the year-round performance of a PV
array. It is not intended to be a design tool because simplifying assumptions have
been made.

68

2. The overall loss/correction factor is for taking into account cable loss, converion
(inverter) loss, mismatch loss, and reduction in output due to rise in cell
temperatures and pollution of panel surface. Loss due to shading effect should be
dealt with using shading analysis technique.
3. Daily mean solar irradiation figures are based on data of King's Park weather
station.
4. The formula for Eg is:
Eg = P x N x R x Tf x Lf / 1000
Source: Electrical and Mechanical Services Department.
http://re.emsd.gov.hk/english/solar/solar_ph/solar_ph_cal.html
PV system energy yield calculator – Partial overlaps
The others 40 modules are overlaps on from March to October.
Peak power rating of PV module (P) = 20Wp
Number of modules (N) = 40
Overall loss/correction factor (Lf) = 0.75
Angle of tilt = 30 degrees

Table 4.6 Overlaps PV system annual energy yield calculator
Daily mean
solar irradiation
(kWh/m
2
)
Tilt factor to be
used

Overlaps reduce
factor % (table
4.3)
Mean energy yield
per day
R (Tf) Overlap HR% Eg
Jan 2.82 1.48 52.5% 1.31 kWh
Feb 2.75 1.31 37.5% 0.81kWh
Mar 2.82 1.11 22.5% 0.42kWh
Apr 3.29 0.93 22.5% 0.41kWh
May 3.91 0.80 5% 0.1kWh

69

Table 4.6: Continued
Jun 3.97 0.73 5% 0.09kWh
Jul 4.6 0.76 5% 0.1kWh
Aug 4.23 0.88 22.5% 0.5kWh
Sep 4.01 1.04 22.5% 0.56kWh
Oct 3.95 1.24 37.5% 1.1kWh
Nov 3.44 1.43 52.5% 1.54kWh
Dec 2.98 1.54 90% 2.47kWh
annual energy yield 287kWh
1. This is a simple calculator for appreciating the year-round performance of a PV
array. It is not intended to be a design tool because simplifying assumptions have
been made.
2. The overall loss/correction factor is for taking into account cable loss, converion
(inverter) loss, mismatch loss, and reduction in output due to rise in cell
temperatures and pollution of panel surface. Loss due to shading effect should be
dealt with using shading analysis technique.
3. Daily mean solar irradiation figures are based on data of King's Park weather
station.
4. The formula for Eg is:
Eg = P x N x R x Tf x Lf / 1000x No Overlaps %
Source: Electrical and Mechanical Services Department.
http://re.emsd.gov.hk/english/solar/solar_ph/solar_ph_cal.html

One office union using （6x8=48 ）48 modules of KS20 annual energy yield =

167+287 kWh = 454 kWh

70

Fan power calculation

Figure: 4.16 fan

Fan consumption power
One office unit uses 4 fans (4x50w= 200 watt)
The fan is turn on from 9:00am to 5:00pm
200x8 hr= 1.6kWh/day
1.6 x 365days= 584kWh
Solar power – Fan consumption power (454-584= 130 watt)
After using on Fan power there still need 130 kWh from Electricity Company.

71

Energy saving integrated façade solar power estimation:
One unit of office needs 48 modules KS 20(Kyocera)
PV capacity = 1Kw
One year can produce 700 kWh =700 Electricity tariffs
Electricity tariffs= 1Kw x 1 hr.
The definition of Electricity tariff on Wikipedia is a “term that implies a certain market
structure, generally that of a regulated monopoly” (Wikipedia, Electricity tariff)
One tariff in Hong Kong = USD 0.129 (Hong Kong Electric)
One unit of office in one year can save 700x 0.129 = 90.3 USD/yr
Environment Benefits
1kWh = 1.64lbs CO2 pollution
1kW DC PV system can save 701
701 x 1.64 = 1149.64 lbs CO2 / year
Eliminate 1149.64 lbs of CO2 pollution over the first year Environmental benefits.
(This calculation doesn’t count the embodied energy)

72

4.4 Ecotect Solar thermal simulation
“ECOTECT uses the CIBSE Admittance Method to calculate heating and cooling loads
for models with any number of zones or type of geometry”. (Autodesk . Ecotect .com.
http://www.ecotect.com/). Ecotect is a environmental and energy analysis tool. This
software is powerful in Shadows and Reflections analysis, solar analysis, thermal
analysis, acoustic, shading design and lighting design.
This study use the same size (20x15x12 foot) and types (no shading, window shading and
PV shading and PV shading with Fan) simulation model in Ecotect, Design builder,
Airpak CFD and 3D MAX simulation.

4.4.1 Simulation model
This study set the Ecotect simulation model in three groups, no shading, window shading
and solar Shading. (Size: 20x15x12 foot).

73

Figure: 4.17 Ecotect radiation analysis no shading model

Figure: 4.18 Ecotect radiation analysis windows shading model

Figure: 4.19 Ecotect radiation analyses PV shading model

74

4.4.2 Ecotect solar radiation simulation
The result show as follow,

Figure: 4.20 Ecotect No shading radiation analyses

Table 4.7 Ecotect No shading radiation analyses (unit: Kbtu)
Total Radiation
Contour Band Within
(from-to) Pts (%)
340-496 0 0
496-652 196 61.25
652-808 21 6.56
808-964 21 6.56
964-1120 8 2.5
1120-11270 16 5
1270-1432 9 2.81
1432-1588 25 7.81
1588-1744 8 2.5
1744-1900 3 0.94
1900-2050 10 3.12
2050-2212 3 0.94
Table 4.2 this table shows the strength of solar radiation spread around the room
For example, the window without any shading on it, the strength of solar radiation on

75

496-652 Kbtu in the room is 61.25%, the strength of solar radiation on 2050-2212 Kbtu is
0.94 % compared with others strength data in the room.
Figure 4.15 shows that the close to the opening the strong solar radiation we gain.

Figure: 4.21 Ecotect window shading radiation analyses

Table 4.8 Ecotect Window shading radiation analyses (unit: kbtu)
Total Radiation
Contour Band Within
(from-to) Pts (%)
340-496 0 0
496-652 196 70
652-808 24 8.57
808-964 26 9.29
964-1120 16 5.71
1120-11270 17 6.07
1270-1432 1 0.36
1432-1588 0 0
1588-1744 0 0
1744-1900 0 0

76

Table 4.8: Continued
1900-2050 0 0
2050-2212 0 0

Figure: 4.22 Ecotect PV shading radiation analyses

Table 4.9 Ecotect PV shading radiation analyses (unit: kbtu)
Total Radiation
Contour Band Within
(from-to) Pts (%)
340-496 0 0
496-652 196 70
652-808 24 8.57
808-964 26 9.29
964-1120 16 5.71
1120-11270 17 6.07
1270-1432 1 0.36
1432-1588 0 0
1588-1744 0 0
1744-1900 0 0
1900-2050 0 0
2050-2212 0 0

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4.5 Design Builder Solar Thermal simulation
“Design Builder is a state-of-the-art software tool for checking building energy, CO2,
lighting and comfort performance”. (Design Builder Inc,
http://www.designbuilder.co.uk/). This software is a powerful and precise energy analysis
tool. Modeling your building is easy and you can choose the different material for your
building. When you select the material for your building, there is a data report on the
screen that really help you understand what have you selected.

4.5.1 Simulation Model
The simulation models for Design builder were set on three groups, no shading, window
shading and solar shading. (Size: 20x15x12 foot)

Figure: 4.23 Design builder No shading model

78

Figure: 4.24 Design builder window shading model

Figure: 4.25 Design builder PV shading model

79

4.5.2Design Builder solar radiation simulation
This study simulate the solar thermal in Design Builder, the chart below show the solar
gain on the eterior window.

Figure: 4.26 Design builder No shading simulation

This diagram and chart shows the solar gain on the exterior window is 9951.19 kBtu per
year on No shading simulation model.

80

Figure: 4.27 Design builder windows shading simulation

This diagram and chart shows the solar gain on the exterior window is 5229.16 kBtu per
year on window shading simulation model.

81

Figure: 4.28 Design builder PV shading simulation
This diagram and chart shows the solar gain on the exterior window is 5229.16 kBtu per
year on PV shading simulation model.

82

4.6 Airpak simulation
“Airpak is an easy-to-use computational fluid dynamics (CFD) tool that lets the user
accurately model airflow, heat transfer, contaminant transport, and thermal comfort in
ventilation systems as well as external building flows”. (Fluent,
http://www.fluent.com/about/news/pr/pr22.htm). This study uses this software to
simulate the speed, pressure and temperature of cavity airflow on double skin.

4.6.1 Simulation model
The models for CFD simulation in Airpak were set on three stories. It is a three story
building model. The size for every unit is 20x15x12 foot. This study on Airpak simulates
four groups, no shading, window shading, PV shading and PV shading with Fan.
On vertical section was set 11 points for data check (H1~H11) and on horizontal section
was set 11 points for data check (D1~D11).
On Airpak simulation we get speed, turbulence current, pressure and temperature data.

83

Figure: 4.29 Airpak simulation model section setting point-height

Figure: 4.30 Airpak simulation model plan setting point-Deep

84

Figure: 4.31 Airpak simulation model No shading

Figure: 4.32 Airpak simulation model Window shading

Figure: 4.33Airpak simulation model solar shading

85

Figure: 4.34 Airpak simulation model PV shading with fan

4.6.2 Airpak speed simulation

Speed simulation examining the Air flow speed from outside to inside.

Figure: 4.35 Airpak speed simulation –no Fan

86

Figure: 4.36 Airpak speed simulation –window shading

Figure: 4.37 Airpak speed simulation –PV shading

87

Figure: 4.38 Airpak speed simulation – PV shading with fan

Figure: 4.39 Airpak speed simulation horizontal setting points’ data Unit: m/s

0
1
2
3
No shading
Window shading
Solar shading
Solar shading with fans
No shading 2 1.39 1.37 1.14 0.89 0.64 0.6 0.54 0.45 0.35 0
Window shading 2 1.54 1.55 1.35 1.44 1.09 0.9 0.53 0.46 0.44 0
Solar shading 2 1.53 1.44 1.11 0.97 0.51 0.47 0.45 0.41 0.37 0
Solar shading with fans 2 1.25 1.15 0.88 0.61 1.51 1.64 1.49 1.21 0.78 0
D1 D2 D3 D4 D5 D6 D7 D8 D9 D10 D11

88

Figure: 4.40 Airpak speed simulation vertical setting points’ data Unit: m/s

0
0.5
1
1.5
2
No shading
Window shading
Solar shading
Solar shading with fans
No shading 0 0.45 0.53 0.6 0.7 0.76 0.69 0.74 0.65 0.85 1.02
Window shading 0 0.27 0.52 0.64 0.66 0.7 0.72 0.67 0.62 0.75 1.32
Solar shading 0 0.37 0.56 0.71 0.72 0.73 0.78 0.76 0.76 0.76 1.44
Solar shading with fans 0 1.9 1.56 1.27 1.23 0.83 0.79 0.74 0.72 0.89 1.53
H1 H2 H3 H4 H5 H6 H7 H8 H9 H10 H11

89

4.6.3 Airpak-turbulence current
The turbulence current simulation examines the Air flow turbulence in the window
shading and after adding the fan on the chimney.

Figure: 4.41 Airpak turbulence current – no fan

Figure: 4.42Airpak turbulence current – with fan

90

4.6.4 Airpak simulation- Pressure

The pressure simulation exanimate the Air flow pressure from outside to inside.

Figure: 4.43 Airpak pressure simulation- No fan

Figure: 4.44 Airpak pressure simulation- window shading

91

Figure: 4.45 Airpak pressure simulation- solar shading

Figure: 4.46 Airpak pressure simulation- PV shading with fan

92

Figure: 4.47 Airpak pressure simulation horizontal setting point Unit: N/m2

Figure: 4.48 Airpak pressure simulation vertical setting point Unit: N/m2

-1
0
1
2
3
4
5
No shading
Window shading
Solar shading
Solar shading with fans
No shading -0.37 -0.45 -0.47 -0.21 0.18 0.8 0.76 0.74 0.73 0.72 0.75
Window shading 0.06 0.05 0.11 0.27 0.45 0.52 0.68 0.75 0.74 0.73 0.72
Solar shading 0.14 0.8 0.76 0.56 0.59 0.75 0.77 0.76 0.74 0.73 0.78
Solar shading with fans 3.14 2.99 3.17 3.87 4.05 2.57 1 1.02 0.99 1 1.14
D1 D2 D3 D4 D5 D6 D7 D8 D9 D10 D11
-4
-2
0
2
4
6
8
No shading
Window shading
Solar shading
Solar shading with fans
No shading -2.8 -2.8 -0.8 -1.2 -0.7 0.48 0.54 0.16 0.58 1.75 1.97
Window shading -2.3 -1.9 -1.6 -0.3 -0.4 0.54 0.75 0.82 0.86 1.91 2.37
Solar shading -2.7 -2.5 -1.2 -0.8 -0.6 0.6 0.77 0.76 1.18 2.35 2.8
Solar shading with fans -0.9 0.42 2.54 2.55 3.94 4.1 4.12 4.04 4.34 5.34 5.87
H1 H2 H3 H4 H5 H6 H7 H8 H9 H10 H11

93

4.6.5 Airpak simulation- Temperature

The Temperature simulation exanimate the Air flow temperature from outside to inside.

Figure: 4.49 Airpak temperature simulation-no fan

Figure: 4.50 Airpak temperature simulation- window shading

94

Figure: 4.51 Airpak temperature simulation- solar shading

Figure: 4.52 Airpak temperature simulations- PV shading with fan

95

Figure: 4.53 Airpak temperature simulation horizontal setting point Unit: C0

Figure: 4.54 Airpak temperature simulation vertical setting point Unit: C0

24.5
25
25.5
26
26.5
27
No shading
Window shading
Solar shading
Solar shading with fans
No shading 26 26 26 26 26 26 26 26 26 26 26
Window shading 26 26 26 26 25.6 25.4 25.4 25.6 25.7 25.9 26
Solar shading 26.1 26.3 26.2 26.2 26.5 26.8 26.7 26.5 26.3 26.1 26
Solar shading with fans 26 26 26 26 26.7 26.8 26.8 26.7 26.6 26.3 26.1
D1 D2 D3 D4 D5 D6 D7 D8 D9 D10 D11
21
22
23
24
25
26
27
28
29
No shading
Window shading
Solar shading
Solar shading with fans
No shading 26 26 26 26 26 26 26 26 26 26 26
Window shading 23.9 23.8 25.5 24.1 23.9 25.4 25.3 24 23.9 25.7 24.7
Solar shading 26.9 27.5 26.1 27.8 27.7 26.8 26.6 27.7 27.6 26.6 27.6
Solar shading with
fans
26.5 26.6 26.5 27 27 27 27.2 27.4 27.3 27.1 27.2
H1 H2 H3 H4 H5 H6 H7 H8 H9 H10 H11

96

4.7 Ecotect lighting simulation
Ecotect lighting analysis can show both natural and artificial light levels at specific points
in the model. This study set the Ecotect simulation model in three groups, no shading,
window shading and solar shading. (Size: 20x15x12 foot)

4.7.1 Ecotect lighting simulation model

Figure: 4.55 Ecotect simulation model no shading

97

Figure: 4.56 Ecotect simulation model window shading

Figure: 4.57 Ecotect simulation model solar shading

98

4.7.2 Ecotect lighting simulation data

Figure: 4.58 Ecotect simulation no shading unit: f/c

This chart shows the strength of daylight level spread in the office space.

99

Figure: 4.59 Ecotect simulation window shading

100

Figure: 4.60 Ecotect simulation solar shading

101

4.8 3D max lighting simulations
“Autodesk 3ds Max 2009 includes tools to predict the way natural and electrical lighting
performs in space”. (Autodesk, http://au.autodesk.com/?nd=class&session_id=3063).
This study evaluates how the daylight works on the window without shading, window
shading and solar shading.
4.8.1 3D max lighting simulation-no shading

Figure: 4.61 3D max lighting simulations-no shading

4.8.2 3D lighting simulation – shading

Figure: 4.62 3D max lighting simulations-with shading
0
2000
4000
6000
8000
10000
D1 D2 D3 D4 D5 D6
spring
summer
winter
0
2000
4000
6000
8000
10000
D1 D2 D3 D4 D5 D6
Shading-spring
summer
winter

102

Chapter 5 Energy Saving integrated façade simulation Analysis

In this chapter we discuss the solar power estimation and the optimal PV distance versus
Optimal PV performance. Furthermore, we analyze those simulation data which we
exanimate in the previous chapter.

5.1 Energy saving integrated façade solar power estimation:
According to Chapter 4.3 PV calculation formulas 1, the top 8 no overlap PV modules
can generate 155.93kWh and the others overlap 40 modules can generate 224.8kWh.
Total annual energy yield is 380.73kWh It is obviously to find out that annual energy
yield on overlap PV modules is 29% of no overlap PV modules. And according to PV
calculation formula 2, the top 8 no overlap PV modules can generate 167kWh and the
others overlap 40 modules can generate 287kWh. It is easy to find out that annual energy
yield on overlap PV modules is 35% of no overlap PV modules. It is almost certain that
overlap PV modules is no efficiency and no economic benefits.
It is strong possibility that it is not a good strategy to set up vertical PV modules on the
façade in low Latitude country such as Hong Kong, Taiwan or Singapore. Because of the
Sun angle, the PV modules overlap one on one other and reduce the PV efficiency and

103

economic benefits.

5.2 Optimal shading distance and optimal PV performance
When we set more PV shadings on the façade, the distance between PV shading and PV
shading will be shorter. This is good for shading but bad for PV energy Efficiency.
Oppositely, when we set less PV shading on the façade, the distance between them will
be larger. This is good for PV performance but bad for Sun shading. This section will the
show optimal shading distance and optimal PV performance by using solar formula
calculation to find out the best distance for PV performance and simulating on Ecotect to
find out the shading performance on the façade.
Optimal Distance
Using sun shade chart we can find out the average monthly solar irradiation hour in
different angles. As revealed by Figure 5.1, direct sun light which irradiate to the PV can
be calculate on the chart. For instance, the façade with 4 PV below 61
o
(no overlap angle)
can get the direct sun light, on September the direct sun is at 8am to 10 am and 14-16pm,
so total accumulation sun irritation is 6 hours(monthly average)

104

Figure: 5.1 Different angle Hong Kong Sun shading chart (June to December) climate consultant
The tables 5.1 shows the solar irradiation hour in different angle that have no PV overlap.
Table 5.1 Solar irradiation hour in different angles
Month 6PV -45
o

5PV -53
o

4PV -61
o

3PV -69
o

2PV -74
o

December 8 hr 8 hr 8 hr 8 hr 8 hr
January
November
7 hr 8 hr 8 hr 8 hr 8 hr
February
October
6 hr 7 hr 8 hr 8 hr 8 hr
March
September
4 hr 5 hr 6 hr 7 hr 8 hr
April
August
4hr 3hr 6hr 6hr 7hr
May
July
1 hr 4 hr 4 hr 6hr 6hr
June 1 hr 4 hr 4 hr 6 hr 6 hr
Total 53 66 76 84 88

105

As can be seen in table 5.2, the number of PV makes a different distance between PV to
PV . Less PV on the façade can access more directly sunlight. Large distance between PV
to PV can get more no overlap angels so that we can get more solar irradiation hours in
the year.
Table 5.2 Solar irradiation hour in different angles
Number
Of PV
Distance
(foot)
No overlap angle Solar irradiation hour
Monthly average (hr)
6 2 45 degree 53
5 2.5 53 degree 66
4 3 61 degree 76
3 4 69degree 84
2 6 74degree 88

Optimal PV (solar gain exterior window)
The optimal PV simulation for different number of solar shading on façade was simulated
in Design Builder. We set 5 group of simulation (6PV, 5PV, 4PV , 3PV, 2PV and no
shading). As we can see in Table 5.3, more PV on the façade can block more solar gain
on the exterior window. For instance, a comparison of those simulation groups, 6PV can
reduce 47.6% of solar gain on the exterior window than no shading.
The simulation results in Design builder about the solar gain on the exterior window
show as table 5.3.

106

Table.5.3 Solar gain exterior window in different number of PV on the facade
Number
Of PV
Distance
(foot)
solar gain exterior
window (Kbtu/yr)
Reduce %
(Compare to no shading)
6 2 5229.16 47.4%
5 2.5 5447.49 45.25%
4 3 6099.3 38.7%
3 4 6987.21 29.78%
2 6 8401.33 15.57%
0 9951.16 0%

The figure 5.2 shows solar irradiation reduction percentage compare with no shading on
the façade and monthly average direct sun light hours of PV. As can be seen by a
comparison of design builder simulation study and solar calculator, the optimal distance
for shading and optimal PV efficiency performance is 4PV (3ft) on the façade.

Figure 5.2 optimal distance & optimal PV performance

107

Annual energy yield of optimal PV performance calculation

After we figure out the optimal PV distance and optimal PV performance, this section
calculate the annual energy yield （kWh ）.As we can seen in figure 5.3 the sun overlap
angle is 61 degree.

Figure: 5.3 4PV Sun and sun shading overlap angle

108

Because of the different sun angle, only the first top 8 modules will not be overlap in all
the year, the others 12 modules will be overlaps on sun angle more than 61 degree.
Sun irradiation overlap & hour of sun irradiation
By comparing with the sun shading chart (June to December) we can find out that sun
irradiation from 8:00 to 16:00 and above 45 degree cannot be counted on, because there
is overlap in the PV panels.

Figure: 5.4 61degreeHong Kong Sun shading chart (June to December) climate consultant

Strength of Sun irradiation & daily hour

Every hour in a day have different sun irradiation strength. The strength of sun irradiation
is less in the morning and sunset, more in the mid noon. PV modules Ks 20 can generate

109

20 kWh; this result was under test conditional of irradiance of 1kW/m2. So the strength
below than 1kW/m2, we need to reduce the percentage of power.

Figure: 5.5 Hong Kong daily solar irradiation
http://www.weather.gov.hk/wxinfo/ts/display_element_solar_c.htm

According to Figure 5.4 and 5.5 we can have a result showing PV overlap reduce factor.
Table 5.4 Solar irradiation overlap reduce factor %
Month Irradiation
hr
Irradiation hr% Irradiation strength
reduce%
Total reduce
factor%
December 8 hr 100% 90% 90%
January
November
8 hr 100% 90% 90%
February
October
8hr 100% 90% 90%

110

Table 5.4:Continued
March
September
6hr 75% 70% 52.5%
April
August
6hr 75% 70% 52.5%
May
July
4hr 50% 50% 25%
June 4 hr 50% 50% 25%
This study provides two solar calculation formulas to verify and compare the result of the
annual energy yield.

Formula 1

Ep = Pas×Ha×K×365

Ep ：Annual Energy Yield （kWh ）
Pas ：PV module design Size （kW ）
Ha ：Site accumulation Solar irradiation （kWh/m2.day ）
K ：Correction factor or design factor
365：Days of year
NO overlaps PV
8 modules (20W)
Pas: 8 x 20W = 0.16 kW
Ha: 44.77/12= 3.56 kWh/m2. Day (from Table 4.2)
K= 0.75
EP = 0.16 x 3.56 x 0.75x 365 = 155.93 kWh

111

Overlaps PV (use solar reduce irradiation factor from table 4.3)
24 modules (20W)
Pas: 24 x 20W = 0.48kW
Ha: Jan 2.82 x 90% =2.53
Feb 2.75x 90% =2.06
Mar 2.82x 75% =2.1
Apr3.29x75% =2.46
May3.91x50% =1.95
June 3.97x50% =1.98
Jul 4.6x 50% =2.3
Aug 4.23x 75% =3.17
Sep 4.01x75% =3
Oct 3.95x90% =3.6
Nov 3.44x90% =3.09
Dec 2.98x90% = 2.68
Jan to Dec = 30.92/12 =2.57kWh/m2. Day
K= 0.75
Total Annual Energy Yield
EP = 0.48x 2.57x 0.75x 365= 337.6 kWh

112

One office union using （4x8=32 ）32 modules of KS20 annual energy yield =
155.93+337.6 = 493.53 kWh
According to Chapter 4.3 PV calculation formulas 1, the top 8 no overlap PV modules
can generate 155.93kWh and the others overlap 40 modules can generate 224.8kWh. It is
obviously to find out that annual energy yield on overlap PV modules is 29% of PV
modules when there was no overlap. After we modified our design to 4PV which is the
optimal distance and optimal PV performance, the top 8” no overlap” PV modules can
generate 155.93kWh and the others “overlap 24 “modules can generate 337.6kWh. The
annual energy yield on overlap PV modules is 72% of no overlap PV modules.
In other words, the original design 40 PV (overlap) can generate 224.8kWh but the
optimal PV (4PV) can generate 337.6kWh. This is a very significant modification for this
study. This scheme not only reduces the installation fee but also enhances the system
energy efficiency.

113

5.3 Solar thermal simulation analysis
The solar thermal simulation for energy saving integrated façade was simulated in two
programs, Autodesk Ecotect and Design Builder.
The simulation result in Ecotect demonstrated the solar radiation on no shading façade is
much more than façade with shading. The graphic in figure 5.6 shows that strength of
solar radiation in 1120 to 2212(KBtu) obviously decreases on Window with shading and
PV shading Façade.

Figure: 5.6 Ecotect Solar Radiation (KBtu)
In Table 5.4 also indicate that strength of solar radiation up to 1432 Kbtu fell off to 0 on
window shading and solar shading. The simulation on window shading and PV shading
show totally the same result.

0
50
100
150
200
250
340-496
496-652
652-808
808-964
964-1120
1120-11270
1270-1432
1432-1588
1588-1744
1744-1900
1900-2050
2050-2212
Total Radiation No shading
Total Radiation Window shading
Total Radiation solar shading

114

Table 5.4 Ecotect Solar Radiation (KBtu)
Total Radiation
Contour Band No shading Window
shading
solar shading
340-496 0 0 0
496-652 196 196 196
652-808 21 24 24
808-964 21 26 26
964-1120 8 16 16
1120-11270 16 17 17
1270-1432 9 1 1
1432-1588 25 0 0
1588-1744 8 0 0
1744-1900 3 0 0
1900-2050 10 0 0
2050-2212 3 0 0

As can be seen in figure 5.6 and table 5.4, Ecotect simulation reveals that Shading on the
façade can block the solar radiation from the sun. Most of the strength radiations fall
away on façade with shading. And it also indicates that different material on the shading
doesn’t affect the result of solar radiation.

The result on Design Builder shows that solar radiation exterior window gain on no
window shading is 9951.16 Kbut a year; solar radiation on window shading and Solar
shading on the façade decline to 5229.16 Kbtu a year. The simulation on window shading
and solar shading show totally the same result.

115

As can be seen on figure 5.7, window with Shading can block 47.4% of solar radiation
out of the wall.

Figure: 5.7 Design Builder Solar Radiation gains exterior windows (KBtu)

116

5.4 CFD simulation analysis

The Computational fluid dynamics simulation for energy saving integrated façade was
simulated in Airpak. This section analyzes the result from Airpak in four factor, wind
speed, wind pressure, temperature and turbulence current.

Airpak speed simulation

According to the Airpak simulation study, the speed of cavity airflow velocity on no
shading façade is faster than window shading and PV shading on the façade. It is a strong
possibility that the shading decrease the wind speed before enters to indoor. We can see
very clearly on the graphic on Figure 5.8. It also shows that the fan accelerate the wind
speed before enters to indoor.

Figure: 5.8 speed simulation horizontal setting points’ data analysis (deep)
0
0.5
1
1.5
2
2.5
D1 D2 D3 D4 D5 D6 D7 D8 D9 D10 D11
No shading
Window shading
Solar shading
Solar shading with fans
window
Shading

117

As we can see in the height speed simulation study, the different simulations groups of
speeds in the chimney are very similar. The speed close to the fan is faster than at the
other data points.

Figure: 5.9 speed simulation vertical setting points’ data analysis (height)

Airpak pressure simulation
The Airpak pressure simulation on the horizontal data shows that pressure between
shading and window are very similar in no fan groups. As revealed by figure 5.10, the
pressure on PV shading with fan is much more than others group. It is likely that the fan
press the air into the indoor spaces.
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
H1 H2 H3 H4 H5 H6 H7 H8 H9 H10 H11
No shading
Window shading
Solar shading
Solar shading with fans

118

Figure: 5.10 pressure simulation horizontal setting points’ data analysis

As can be seen, pressure in no fan groups is very similar. Figure 5.11 obviously shows
pressure in the chimney is much high than others simulation groups. It is a good
possibility that fan press the air and accelerate the air speed.

Figure: 5.11pressure simulation vertical setting points’ data analysis (Height)
-1
-0.5
0
0.5
1
1.5
2
2.5
3
D1 D2 D3 D4 D5 D6 D7 D8 D9 D10 D11
No shading
Window shading
Solar shading
Solar shading with fans
-4
-3
-2
-1
0
1
2
3
4
5
6
7
H1 H2 H3 H4 H5 H6 H7 H8 H9 H10 H11
No shading
Window shading
Solar shading
Solar shading with fans
window
Shading
window
Shading

119

Airpak temperature simulation
The temperature in this simulation is set on 26
0
C. PV shading absorb heat from the sun to
generate electricity, the temperature can arrive more than 50
0
C. This study set the PV
shading temperature on 50
0
C. According to the simulation result, Shading on the window
raise the temperature 0.6~0.8
0
C. PV shading is higher than window shading. It is almost
certain that window shading block the sun out from the window but the heat remains on
the shading. Figure 5.8 also shows the fan can cool down the heat on the PV modules
around 0.1
0
C.

Figure: 5.12 temperature simulation horizontal setting points’ data analysis (deep)

The results on Figure 5.13 indicate that temperature in the chimney close to the window
is lower than other part. It is probable that window opening let the air flow into the
25.4
25.6
25.8
26
26.2
26.4
26.6
26.8
27
D1 D2 D3 D4 D5 D6 D7 D8 D9 D10 D11
No shading
Window shading
Solar shading
Solar shading with fans
window
Shading

120

interior and counteract the hot air. The temperatures on PV shading with fans are more
even in the chimney. It is probable those fans not only accelerates the air speed but also
cool down the temperature.

Figure: 5.13 temperature simulation vertical setting points’ data analysis (height)

5.5 Lighting simulation analysis
This simulation is set on three groups, spring summer and winter. According to the
simulation results, window shading group strength of light in spring summer and winter
is less than no shading groups. It is strong possibility that window shading block sun light
out of window.
The minimum comfortable to writing indoor we need 1000 Lux. As has been
demonstrated by figure 5.14, 5.15 and 5.16, the light strength after window shading
blocked, it still has enough for witting (1000 Lux) in every season before D4(3m deep).
25
25.5
26
26.5
27
27.5
28
H1 H2 H3 H4 H5 H6 H7 H8 H9 H10 H11
No shading
Window shading
Solar shading
Solar shading with fans

121

After D4 we still need artificial lighting to satisfy for writing.
Figure 5.14 shows the lighting simulation of no shading and window shading on spring
March 21. As can be seen in figure 5.14, sun light has been decreased about 1500 Lux
on D1 (behind the shading panel) and 2900Lux on D2 (b3hind the window) than no
shading.

Figure: 5.14 lighting simulation on March 21/ 12pm

As shown in Figure 5.15, sun light has been decreased about 1000 Lux on D1 (behind the
shading panel) and D2 (behind the window) than no shading. There is a strong possibility
that the high sun angle on summer doesn’t affect the vertical façade that much.

0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
D1 D2 D3 D4 D5 D6
NO shading-spring
Shading-spring
Window
Shading

122

Figure: 5.15 lighting simulation on June 21/ 12pm
Figure 5.16 shows the lighting simulation of no shading and window shading on winter
December 21. As can be seen in figure 5.16, sun light has been decreased about 2600
Lux on D1 (behind the shading panel) and 4200Lux on D2 (behind the window) than no
shading. Because of the lower sun angle on the winter, it is highly likely that the sun light
access into the building more than summer and spring. Even the shading blocks more sun
light but the amount Lux of light is still higher than summer and spring.
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
D1 D2 D3 D4 D5 D6
NO shading-summer
Shading-summer
window
Shading

123

Figure: 5.16 lighting simulation on December 21/ 12pm

0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
D1 D2 D3 D4 D5 D6
NO shading-winter
Shading-winter
window
Shading

124

Chapter 6 Conclusion & Future Work

6.1 Conclusion

The energy saving integrated façade was designed based on reference data and case study.
It also uses simulation modeling to prove the design rationale.
The energy saving integrated façade performs in four areas; application of solar power,
heat insulation efficiency, lighting and ventilation efficiency. It is composed of sun
shading with photovoltaic panels, fans and an air chimney with steel structure on the
building envelope. The conclusion of this study can be separated into two parts; energy
saving integrated design and simulation experimentation.
Feedback from using computer simulation:
1. Adjust PV tilt angle from 23 degrees to 30 degrees. Because of the vision and overlap
problem, it is better to adjust to 30 degree.
2. According to Chapter 5.1, the optimal distance for PV performance support a final
design modified to 4PV modules on the façade.
3. In chapter 4.3 the PV annual yield calculation indicated that it is not favorable to set
PV panel on vertical façade, because the sun angle, those PV modules will overleap

125

one by one and reduce the efficiency and economic benefits. Finally, the energy saving
façade takes out those PV modules which are overlapping and replace with alumni
window shading.

6.1.1 Energy saving Integrated Design conclusion

Table 6.1Energy saving integrated façade design
Item suggestion This study remark
Solar power Solar cell Monocrystalline
Multicrystalline
Multicrystalline Ks 20
PV system shunt winding shunt winding
Best system orientation south ＞eat south/west
south ＞east / west
South
Best Tilt angle 38° 30° (visual )
Module size Depend on opening 110×40cm
Building
insulation
Wall insulation U ＝2.5W/ （m
2
k ） U ＝2.5W/ （m
2
k ）
Window glass LOW-E
Air chimney 30~60cm 60cm cat way
Ambition
lighting
Room size 13x20 ft 15x20 ft
Opening rate 25~30 ﹪ 30 ﹪
Opening form floor <9 ft 9 ft
Control system PSALI Supply from
PV power
ventilation Ventilation method Flow and wind
Window style Rotate window
others structure steel
joint Steel join
Window shading one five

126

Figure: 6.1 Energy saving façade PV Modules (Credit source for Kyocera images)

Figure: 6.2 Energy saving façade 3D model

127

Figure: 6.3 Energy saving façade 3D detail

Figure: 6.4 Energy saving façade rear elevation

128

Figure: 6.5 Energy saving façade 3D detail 2

6.1.2 Energy saving integrated façade Simulation conclusion
Energy saving integrated façade solar power estimation
1. The original energy integrated saving facade was designed on 6PV array on the
façade. The top PV array (no overlap) can generate 155.93(kWh/yr) and the others
overlap 5 PV arrays modules can generate 224.8(kWh/yr). Total annual energy yield
is 380.73(kWh/yr). The annual energy yield on overlap PV modules is 29% of PV
modules with no overlap.

129

2. According to the solar formula calculation and design builder solar gain on the
exterior window, the best distance and shading for PV performance on the façade
with 4PV was determined. The distance between each PV panel is 3 ft. The annual
energy yield of this optimal PV is 493.53 (kWh/yr). The top PV array (no overlap)
can generate 155.93(kWh/yr) and the other overlapping 3 PV modules can generate
337.6(kWh/yr). The annual energy yield on overlapping PV modules is 72%
compared to no overlapping PV modules. This Optimal scheme not only cost down
the application fee but also enhances the system energy efficiency.
3. Economy benefit: vertical PV modules design on the façade in low-latitude countries
such as Hong Kong, Taiwan or Singapore overlap one on one other and reduce the PV
efficiency and economic benefits.

Solar thermal simulation
1. The simulation result in Ecotect demonstrated the solar radiation on no shading
façade is more efficient than façade with shading. The strength of solar radiation in
1120 to 2212(KBtu) obviously decreases on a window with shading and PV shading
Façade.

130

2. According to the simulation in Design Builder, using shading on the window can
block47.4% of the solar gain on the exterior window. The type of material on the
shading doesn’t make any different to solar radiation.

Solar thermal simulation
3. The simulation result in Ecotect demonstrated the solar radiation on no shading
façade is much more than façade with shading. The strength of solar radiation in
1120 to 2212(KBtu) obviously decreases on Window with shading and PV shading
Façade.
4. According to the simulation in Design builder, Using shading on the window can
block47.4% of the solar gain on the exterior window. The type of material on the
shading doesn’t make any different to solar radiation.

CFD simulation analysis
1. The speed of cavity airflow velocity on no shading façade is faster than window
shading and PV shading on the façade. I the results of design A indicate that
integration of shading on the exterior of the façade with natural ventilation will
decrease the wind speed before entering the indoor environment.

131

2. The pressure on PV shading with fan is much more than no shading group. It is
almost certain that the fan press the air into indoor.
3. The fan also forces the air into the interior space.
Lighting simulation analysis
1. During spring months, the sun light has been decreased 1592 Lux behind the shading
panel and 2883Lux behind the window with no shading.
2. During summer months, the sun light decreases 1061 Lux behind the shading panel
and behind the window than no shading. There is a strong possibility that the high sun
angle on summer doesn’t affect the vertical façade that much.
3. During winter months, the sun light has been decreased about 2649 Lux behind the
shading panel and 4236Lux behind the window than no shading. It is very probable
that the lower sun angle on the winter, it is highly likely that the sun light access into
the building more than summer and spring. Even the shading blocks more sun light
but the amount Lux of light is still higher than summer and spring.
4. Depend on different season window shading can shading can block 40% to 62% of
light out of the window. The sunlight can approach 1000 Lux three meters away from
the window.

132

6.2 Suggestion and future work

6.2.1 Suggestions
The modeling simulation of energy saving integrated facade revealed several important
directions to improve the energy consumption of the design. Suggestions as the
following:
Solar power versus day lighting
The primary benefits of using solar power are that it can generate clean power and can
insulate solar heat out of the building. The indoor space will get less heat and reduce the
HVAC energy load. But using PV shading on the window also blocks 40% to 60% of day
light. At day time it may increase the building lighting energy. Here I suggest two
solutions,
1. Set up lighting reflection board. This lighting refection board can use as a window
shading. It can block part of sun light and reflect part of sun light into the building.

133

Figure: 6.6 lighting reflection board concept (Huang 2004)
2. With the use semi-transparent photovoltaic modules, the amount of light transmitted
can be adjusted to as much as 20% or more. (National Renewable Energy Laboratory)
The transparent photovoltaic modules will allow more day light to pass through the
shading, generate clean power and reject insulating solar heat away from the building.

134

Figure: 6.7 semi transparent photovoltaic window shading (SBIC East Head Office Building,
www.iea-pvps.org/cases/jpn_02.htm)

3. In lower latitude climates, such as Hong Kong, it is not a good strategy to install PV on
vertical façades. The sun angle in the summer is almost 90 degrees; therefore, the
vertical façade won’t face to the sun and reduce their power generate efficiency. A good
strategy is to set the PV array on the roof facing south with 23 degree tilt angle.
6.2.2 Future work
This energy saving facade study integrated elements of solar power, heat insulation
efficiency, lighting and ventilation efficiency. Reference data is used to complete the
design and simulation of solar radiation, lighting, thermal comfort and fluid dynamics.

135

But it still requires more simulations and experiments to prove the rationality of this
energy saving integrated façade approach. So here are some points of suggestion to
reference for people who decide to pursue the same area of study.
1. Make a full-scale mock-up of model performance application of solar power, heat
insulation efficiency, lighting and ventilation efficiency. Then it can test and get the
real data from the model to do the analysis. This test can validate the rationality of
this energy saving integrated façade and make the design more reasonable.
2. Human health is an essential issue. Health issues are more important than energy
saving issue. So testing indoor air quality or considering the indoor comfort and
health is an opportunity to explore further in future work.
3. Future work can focus on different size of opening, type of window, different climate
condition, daytime or night time ，to accumulate and complete the study data for this
energy saving integrated façade.
4. Energy saving integrated façade can also integrate more functions, such as acoustic,
fireproof, indoor comfort, sustainable material. Integrated façade not only can make
more economic benefits but also can zealous to develop low energy or zero energy for
our sustainability environment

136

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Eiffert, Patrina (2000). Building-Integrated Photovoltaic Designs for Commercial and
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Huang, Taiuey(2004), Study and Analysis of Energy Save in Integrated Building Skin
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Abstract (if available)

Abstract Global warming is a serious problem we face today. Overusing fossil fuels not only emits wasteful gas and pollutes our atmosphere but also produces greenhouse gases that lead to global warming. In response to the energy crisis and global warming, solar energy is a source of energy that can be used without depleting. Solar energy is quiet and produces no toxic emission or greenhouse gas. It is an ideal energy we can use instead of fossil fuel and stop global warming. One of the methods to use renewable solar energy is Building Integrated Photovoltaic (BIPV). The basic frame of energy saving integrated façade can integrate with manipulation of solar energy, heat insulation efficiency, ambient lighting, transmit lighting and ventilation efficiency on the photovoltaic (PV) sun shading and fan. The power that is needed for the fan control results from the collection of the PV sun shading. PV shading is also a sustainable insolation prevention system for tropical zones. This thesis demonstrates that an air curtain is an effective thermal strategy that supports the new age of low-energy, zero-energy sustainable energy saving architecture.

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Asset Metadata

Creator Huang, Tai Uey (author)

Core Title Energy saving integrated facade: design and analysis using computer simulation

School School of Architecture

Degree Master of Building Science

Degree Program Building Science

Publication Date 08/04/2010

Defense Date 08/03/2010

Publisher University of Southern California (original), University of Southern California. Libraries (digital)

Tag BIPV,double skin,energy saving facade,OAI-PMH Harvest

Place Name Basel (city or populated place), California (states), Freiburg (city or populated place), Germany (countries), San Francisco (city or populated place), Switzerland (countries)

Language English

Contributor Electronically uploaded by the author (provenance)

Advisor Noble, Douglas (committee chair), La Roche, Pablo (committee member), Vaglio, Jeffrey (committee member)

Creator Email dhuang@akintl.com,taiueyhu@usc.edu

Permanent Link (DOI) https://doi.org/10.25549/usctheses-m3268

Unique identifier UC1133136

Identifier etd-HUANG-3966 (filename),usctheses-m40 (legacy collection record id),usctheses-c127-369396 (legacy record id),usctheses-m3268 (legacy record id)

Legacy Identifier etd-HUANG-3966.pdf

Dmrecord 369396

Document Type Thesis

Rights Huang, Tai Uey

Type texts

Source University of Southern California (contributing entity), University of Southern California Dissertations and Theses (collection)

Repository Name Libraries, University of Southern California

Repository Location Los Angeles, California

Repository Email cisadmin@lib.usc.edu