AIR-CONDITIONING SYSTEM

BY USING DISTRICT COOLING SYSTEM (DCS):

THERMAL ENERGY STORAGE (TES) TECHNOLOGY

NORDIANA BINTI MOHD HATTA

UNIVERSITI TEKNIKAL MALAYSIA MELAKA

“I admit that had read this dissertation and in my opinion this dissertation

is satisfactory in the aspect of scope and quality for the bestowal of

Bachelor of Mechanical Engineering (Design and Innovation)”

Signature:

Name of Supervisor 1: Mr. Safarudin Gazali Herawan

Date:

Signature :

Name of Supervisor 2: Mr. Afzanizam

Date:

AIR-CONDITIONING SYSTEM

BY USING DISTRICT COOLING SYSTEM (DCS):

THERMAL ENERGY STORAGE (TES) TECHNOLOGY

NORDIANA BINTI MOHD HATTA

This report was submitted in accordance

with the partial requirement for the honor of

Bachelor of Mechanical Engineering (Design and Innovation)

Faculty of Mechanical Engineering

Universiti Teknikal Malaysia Melaka

APRIL 2009

ii

“I verify that this report is my own word except summary and extract that

every one of it I have clarify the resource”

Signature:

Writer Name: Nordiana binti Mohd Hatta

Date:

iii

For my beloved parents, siblings and friends

iv

ACKNOWLEDGEMENT

I would like to acknowledge and extend my heartfelt gratitude to the

following persons who have made the completion of this Projek Sarjana Muda

(PSM) report possible. I would like to express my deep and sincere gratitude to my

supervisor, Mr. Safarudin Gazali Herawan, His wide knowledge and his logical way

of thinking have been of great value for me. I am deeply grateful for his detailed and

constructive comments, and for his important support throughout this work.

I wish to express my warm and sincere thanks to Mr. Amiruddin Ghazali,

Head of Section of TNEC and Mr. Sharulnizam Shariff, Plant Supervisor of TNEC

who gave me the opportunity to gain knowledge and experiences about the DCS and

TES systems that wholly-liable under TNB Engineering Corporation (TNEC) and

gave me untiring help during my difficult moments. I owe my most gratitude to Mr.

Nazree Abdullah, Senior Technician of TNEC for his valuable advice and friendly

help. Their extensive discussions around my work and interesting explorations in

operations have been very helpful for my PSM.

During this work I have collaborated with many colleagues for whom I have

great regard, and I wish to extend my warmest thanks to all those who have helped

me with my work. The generous support from all of you is greatly appreciated. I

cannot end without thanking my family, on whose constant encouragement and love

I have relied throughout my time at the university. Their unflinching courage and

conviction will always inspire me, and I hope to continue, in my own small way, the

noble mission to which they gave their lives. It is to them that I dedicate this

knowledge and experience. And to God, who made all things possible.

v

ABSTRACT

This study is about the air conditioning system by using District Cooling

System (DCS) with the Thermal Energy Storage (TES) technology. DCS is a system

where a central chiller plant provides chilled water for air-conditioning purposes for

multiple buildings. Whereas TES is the storage of cooling energy during low air-

conditioning loads period and used later to meet the air-conditioning loads. TES can

be further broken down into ice harvesting, ice-on-coil, ice slurry, and encapsulated

ice options. Ice-on-coil systems may be internal-melt or external-melt and may be

charged and discharged with refrigerant or a single-phase coolant (typically a

water/glycol mixture). Ice-on-coil systems come in several variations. In all

variations, ice is formed on a heat transfer surface (generically referred to as a

“coil”) without being released during the charging mode and melted away during the

discharge mode. Ice-harvesting systems form ice on coils or other refrigerant

evaporating surfaces and periodically release the ice into a storage tank that contains

a mixture of ice and water. Ice slurry systems produce small particles of ice within a

solution of glycol and water, resulting in a slushy mixture that can be pumped.

Encapsulated ice systems consist of water contained in plastic containers surrounded

by coolant, all contained within a tank or other storage vessel. Within this report, all

of these systems will differentiate by the storage system technologies, the

mechanism, design and operating systems. Considering the pros and cons, the most

suitable system will choose. The reasons of choosing that system as the best option

will briefly explain. Moreover, the cooling load of FKM blocks in Durian Tunggal

will calculate by using Carmel software. The overview of the software is preview,

also the data insertion, check and end result. There are two types of outcomes of the

program which consisting of result output and graph output. The most appropriate

vi

capacity/types of equipments that could go well with the system would be selected in

order to ensure the system can operate efficiently. These equipments comprise of

STL tank, chiller, cooling tower, heat exchanger and air-handling unit (AHU).

The end part of this report will gives general conclusion on this study. It also include

a suggestion to continue the research on this topic for better understanding on the

refrigeration system and more to the point of obtaining the most competent cooling

system in order to reduce its monthly expenses but with higher efficiency and give

much benefits to the consumers.

vii

ABSTRAK

Kajian ini adalah mengenai sistem penyejukan udara menggunakan Sistem

Pendingin Lingkungan (District Cooling System-DCS) dengan teknologi Tenaga

Pendam Lakuran (Thermal Energy Storage-TES). DCS ialah sistem di mana pusat

chiller plant membekalkan air sejuk untuk tujuan penyejukan bagi beberapa

bangunan sekitar. Manakala TES adalah penyimpanan tenaga penyejukan pada

waktu beban penyejukan rendah dan akan digunakan kemudian ketika tenaga

penyejukan itu diperlukan. TES terbahagi kepada beberapa jenis iaitu ice harvesting,

ice-on-coil, ice slurry dan encapsulated ice Sistem Ice-on-coil terbahagi kepada dua

iaitu pencairan dalam (internal-melt) dan pencairan luar (external-melt) di mana ia

akan dicaj dan nyahcaj menggunakan bahan penyejuk atau cecair penyejuk satu fasa

(biasanya campuran air/glikol). Terdapat pelbagai variasi di dalam sistem ice-on-coil

di mana di dalam semua variasi, ais terbentuk pada permukaan haba dipindahkan

(disebut sebagai “coil”) tanpa dibebaskan semasa pengecasan dan ais mencair

semasa penyahcasan. Sistem ice harvesting membentuk ice-on-coil atau permukaan

sejatan bahan penyejuk lain dan menyalurkan ais secara berperingkat ke dalam

tangki yang mengandungi campuran ais dan air. Sistem ice slurry menghasilkan ais

yang kecil di dalam larutan glikol dan air menjadikan ia sebagai larutan separa cair

yang boleh dipam. Sistem kapsul ais (encapsulated ice) adalah kapsul plastik yang

mengandungi air dan dikelilingi oleh cecair penyejuk di dalam sebuah tangki atau

bekas penyimpanan lain. Di dalam laporan ini, sistem-sistem ini akan dibezakan

melalui teknologi sistem penyimpanan, mekanisma, rekabentuk serta sistem operasi

setiap satunya. Selepas mengambil kira kelebihan dan kekurangan, system yang

paling sesuai akan dipilih dan sebab-sebab sistem ini dipilih akan dijelaskan. Beban

penyejukan bagi blok FKM di durian tunggal akan dikira menggunakan perisian

Carmel. Sedikit gambaran tantang program perisian akan diterangkan beserta

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cara memasukkan data, penyemakan dan hasil akhir. Terdapat dua jenis hasil iaitu

keputusan teks dan graf. Kelengkapan lain berkaitan sistem ini seperti tagki STL,

chiller, menara penyejuk, penukar haba dan air handling unit (AHU) akan dipilih

berdasarkan kapasiti/jenis yang terbaik yang dapat memaksimakan kecekapan

sistem. Kesimpulan mengenai kajian disertakan di akhir laporan yang juga

merangkumi cadangan untuk meneruskan kajian berkenaan topik ini dengan tujuan

untuk lebih memahami tentang sistem penyejukan dan lebih menjurus kepada

menghasilkan sistem yang kompeten untuk mengurangkan kos bulanan dan dalam

masa yang sama merupakan sistem yang efisien serta memberi banyak kelebihan

kepada pengguna.

ix

TABLE OF CONTENT

CHAPTER TITLE PAGE

DECLARATION ii

DEDICATION iii

ACKNOWLEDGEMENT iv

ABSTRACT v

ABSTRAK vii

TABLE OF CONTENT ix

LIST OF TABLES xiv

LIST OF FIGURES xv

LST OF SYMBOLS xvii

LIST OF ABBREVIATIONS xix

LIST OF APPENDIX xx

CHAPTER I INTRODUCTION 1

1.1 Background 1

1.2 Problem Statement 2

1.3 Objectives 3

1.4 Scope of Study 3

CHAPTER II LITERATURE REVIEW 5

2.1 District Cooling System (DCS) 5

2.1.1 Overview of DCS 5

x

CHAPTER TITLE PAGE

2.1.2 The District Cooling System (DCS)

Concept

7

2.1.3 The Benefits of DCS 8

2.2 Thermal Energy Storage (TES) 9

2.2.1 Overview of TES 9

2.2.2 Economics of Thermal Storage 10

2.2.3 Other Benefits 12

2.2.4 Storage System Technologies 14

2.2.4.1 Chilled Water Storage 14

2.2.4.2 Ice storage 17

2.2.4.3 Eutectic Salts Storage 21

2.2.5 The Variations of Mechanisms 22

2.2.5.1 Chilled Water System 22

2.2.5.2 Ice Storage System 25

2.2.5.3 Eutectic Salt Systems 32

2.2.6 The Variations of Design and Operating

Strategies

33

2.2.6.1 Full Storage System 33

2.2.6.2 Partial Storage 34

CHAPTER III METHODOLOGY 36

3.1 Introduction 36

3.2 Implementation Flow Chart 37

3.3 Carmel Software 38

3.4 Loadsoft 6.0 Software 40

3.5 Data Insertion, Checks and Outputs 41

3.5.1 Terminology 41

3.5.2 Data Insertion 43

3.5.3 Checks 60

xi

CHAPTER TITLE PAGE

3.5.4 Outputs 61

3.5.4.1 Calculation Month and Time

Range

62

3.5.4.2 Standard Outputs 63

3.5.4.3 What-If Scenario Outputs 64

3.5.5 Report Description 64

3.5.5.1 System/Area Heating and Cooling

Load Summary Report

64

3.5.5.2 Breakdown of All Load

Components Report

65

3.5.5.3 Detailed Psychrometric Analysis

Report

67

3.5.5.4 Wall and Window Load Summary

Report

67

3.5.5.5 Graph Outputs 68

3.6 Equipment Selection 70

3.6.1 STL Tank 70

3.6.1.1 Atmospheric Tank Option 71

3.6.1.2 Pressurized Tank design Option 72

3.6.2 Chillers 73

3.6.2.1 Types of Chillers 74

3.6.3 Cooling Tower 77

3.6.3.1 Type of Cooling Tower 77

3.6.3.2 Water Treatment 79

3.6.4 Heat Exchanger 80

3.6.4.1 Types of Heat Exchanger 80

3.6.5 Air Handling Unit (AHU) 82

3.6.5.1 Temperature Control 84

3.6.5.2 Humidity Control 84

xii

CHAPTER TITLE PAGE

CHAPTER IV RESULT 85

4.1 Introduction 85

4.2 DCS Incorporating With TES Technology 86

4.3 Results/Outputs of Carmel Software 86

4.3.1 System/Area Heating and Cooling

Load Summary Report

87

4.3.2 Breakdown of All Load Components

Report

89

4.3.3 Detailed Psychrometric Analysis

Report

91

4.3.4 Wall and Window Load Summary

Report

92

4.3.5 Graph Output 93

4.4 Result Analysis 95

CHAPTER V DISCUSSION 96

5.1 Introduction 96

5.2 Equipment Selection 97

5.2.1 Encapsulated Ice 97

5.2.1.1 Benefits of Using Ice Balls 99

5.2.1.2 Basic System Operation 100

5.2.1.3 Modular Tanks vs. Encapsulated

Ice Storage

101

5.2.2 STL Tank 104

5.2.2.1 Inventory Tank 104

5.2.2.2 STL Tank Size Determination 105

5.2.3 Chiller 107

5.2.3.1 Centrifugal Chiller 108

5.2.4 Cooling Tower 109

xiii

CHAPTER TITLE PAGE

5.2.5 Heat Exchanger 110

CHAPTER IV CONCLUSION AND SUGGESTION 112

6.1 Conclusion 112

6.2 Suggestion 112

REFERENCES 114

BIBLIOGRAPHY 116

APPENDIX A 118

APPENDIX B 120

APPENDIX C 128

xiv

LIST OF TABLE

TABLE TITLE PAGE

2.1 Comparison of alternative thermal storage technologies 14

4.1 Benefits of using ice balls 99

4.2 Typical tank size dimension 106

xv

LIST OF FIGURES

FIGURE TITLE PAGE

2.1 Typical DCS configuration 7

2.2 Typical design day chilled water load profile 11

2.3 How TES technology saves energy cost 13

2.4 Chilled water storage tank with siphon baffles 16

2.5 Ice shedder thermal storage system schematic 18

2.6 External melt coil freezing thermal storage system

schematic

19

2.7 Internal melt coil freezing thermal storage system

schematic

20

2.8 Chilled water stratification 24

2.9 Typical chilled water configuration 24

2.10 Typical ice-harvesting configuration 26

2.11 External-melt ice-on-coil 27

2.12 Internal melt ice-on-coil 27

2.13 Direct refrigerant external-melt ice-on-coil

configuration

28

2.14 Secondary coolant external-melt ice-on-coil

configuration

28

2.15 Typical internal-melt ice-on-coil configuration 29

2.16 Typical Ice Slurry Configuration 30

2.17 Encapsulated ice balls 31

2.18 Typical encapsulated ice configuration 31

2.19 Eutectic salt container 32

2.20 Typical eutectic salt configuration 32

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FIGURE TITLE PAGE

2.21 Full storage 33

2.22 Partial storage – load leveling 34

2.23 Partial storage – demand limiting 35

3.1 Implementation flow chart 37

3.2 Software program from Carmel 39

3.3 Basic data input 44

3.4 System inputs 45

3.5 Air volume calculation type / pretreating 47

3.6 Zone inputs 48

3.7 General area 49

3.8 Wall and roof envelope 50

3.9 Wall CTS number 51

3.10 Roof CTS number 52

3.11 Window envelope 53

3.12 Window SHGC properties 53

3.13 Window construction U-value 54

3.14 Door envelope 55

3.15 Internal / other 56

3.16 People activity level 56

3.17 Schedule 58

3.18 Appliance list 59

3.19 Checks/outputs 61

3.20 Display Report 1 63

3.21 Display Report 2 63

3.22 Graphing output option 69

3.23 Atmospheric Tank System 72

3.24 Pressurized tank system 73

3.25 Centrifugal chiller 75

3.26 Reciprocating chiller 76

xvii

FIGURE TITLE PAGE

3.27 Screw chiller 76

3.28 Cross flow cooling tower 78

3.29 Cross flow cooling tower system 78

3.30 Counter flow cooling tower 79

3.31 Counter flow cooling tower system 79

3.32 Shell and tube heat exchanger 81

3.33 Plate heat exchanger 82

3.34 Plate fin heat exchanger 82

3.35 Air handling unit 83

4.1 Horizontal bar chart 93

4.2 Pie chart 94

4.3 Line chart 94

5.1 Ice ball characteristic 98

5.2 Charging and discharging process of ice ball 98

5.3 Charging cycle 100

5.4 Discharging cycle 100

5.5 Standby mode 101

5.6 Modular ice storage tanks 102

5.7 Encapsulated ice 103

5.8 Centrifugal chiller parts 108

5.9 Reduction in chiller capacity usage 110

5.10 Cooling tower crossflow type design 111

5.11 Plate heat exchanger (PHE) 113

5.12 Partial storage – load leveling 114

xviii

LIST OF SYMBOLS

BTU = British Thermal Unit

C = Celsius

CFM = Cubic Feet Meter

F = Fahrenheit

hr = Hour

J = Joule

J/kg = Joule per kilogram

K = Kelvin

kg = Kilogram

KJ = Kilojoules

kPA = Kilopascal

kW = Kilowatt

kW/h = Kilowatt per Hour

kWh = Kilowatt hour

m3

= Cubic meters

m3/hr = Cubic meters per Hour

mm = Millimeter

RT = Refrigerant ton

RTHr = Refrigerant ton hour

SqFt = Square feet

SqM = Square meter

Ton-Hr = Ton hour

xix

LIST OF ABBREVIATION

ASHRAE = American Society of Heating, Refrigerating and

Air-Conditioning Engineers

CMA = Calcium Magnesium Acetate

COP = Coefficient of Performance

CTS = Conduction Time Series

DCS = District Cooling System

DX = Direct Expansion

FKM = Fakulti Kejuruteraan Mekanikal

(Faculty of Mechanical Engineering)

HCFC = Hydrochlorofluorocarbons

HFC = Hydrofluorocarbon

HVAC = Heating, Ventilating and Air-Conditioning

HW = Heavy Weight

IP = Inch-Pound

L/s = Litres per second

O&M = Operation and Maintenance

PSM = Projek Sarjana Muda

RTS = Radiant Time Series

SHGC = Solar Heat Gain Coefficient

SI = System International

STL = Storage Thermal Latent

TES = Thermal Energy Storage

TNB = Tenaga Nasioanal Berhad

TNEC = TNB Engineering Corporation

UTeM = Universiti Teknikal Malaysia Melaka

VAV = Variable Air Volume

xx

LIST OF APPENDIX

APPENDIX TITLE PAGE

A Gantt Chart 118

B Data Insertion in Carmel Software and Graph Output 120

C FKM Block Floor Plan 128

1

CHAPTER I

INTRODUCTION

1.1 Background

Referred to Robert (2003), there are two types of HVAC systems designed to

satisfied building cooling requirements; direct expansion (DX) systems, in which

there is direct heat exchange between the building air and the refrigerant, and

secondary refrigerant systems that utilize chilled water as an intermediate heat

exchange medium to transfer heat from the building air to the refrigerant which we

called it centralized cooling system or commercially named Direct Cooling System

(DCS).

Basically, a DCS distributes thermal energy in the form of chilled water or

other media from a central source to multiple buildings through a network of

underground pipes for use in space and process cooling. The cooling or heat

rejection is usually provided from a central cooling plant, thus eliminating the need

for separate systems in individual buildings. In DCS there is one new technology

which called Thermal Energy Storage (TES). This type of system has been use

widely in overseas but only introduced in Malaysia for about few years.

Thermal Energy Storage capitalizes on the cheaper off-peak tariff offered by

the electric utility company. The system produces cooling energy at night when the

electricity tariff is low. During the day, when the air-conditioning demand is high,

2

the stored cooling energy is released by circulating chilled water through the storage

system and onto the buildings. Only a limited amount of chiller capacity needs to

operate during this period. By adopting this concept, the plant consumes less

electricity during the day, when electricity tariff is high. This leads to significant

savings in operating costs. As the electrical power demand for this plant is also low

during the day, further cost saving is achieved through reduced maximum demand

charges.

There are many different types of thermal storage systems representing

different combinations of storage media, charging mechanisms, and discharging

mechanisms. The basic media options are water, ice, and eutectic salts. This system

can be further broken down into ice harvesting, ice-on-coil, ice slurry, and

encapsulated ice options.

1.2 Problem Statement

The purpose of the study is to find an approach in order to get lower cost and

high efficiency for air-conditioning system. Almost every commercial buildings and

offices have an air conditioning unit. It has become necessity of modern life. There

are two major options to distribute cooling energy to building which are direct

expansion system and centralized system. For the average sized of office and home,

the trend is to use building-specific cooling that is a split air conditioning unit. For

large and/or multiple buildings, it make use of central air conditioning unit which

also called District Cooling System (DCS). District cooling means the centralized

production and distribution of cooling energy. Commonly, many building which

applied this DCS system would use water as a refrigerant. This system will cost high

monthly expenses of the electricity consumption of the system also for the

maintenance and services. This is because the water chillers will be operated all the

time as required to supply cooling energy into buildings and normally the demand is

during peak hours. In order to solve this problem, there is new development of

refrigeration technology called Thermal Energy Storage (TES). TES can reduce cost

by shifting the electricity consumption from day to night. With this system, the