TECHNO-ECONOMICS OF RAINWATER HARVESTING...

TECHNO-ECONOMICS OF RAINWATER HARVESTING TECHNOLOGY

FOR DOMESTIC USAGE AND COOLING

ABDURAHIM ALMABRUK SHATEWI

A project report submitted in partial fulfillment of

the requirements for the award of the degree of

Master of engineering (Mechanical Engineering)

Faculty of Mechanical Engineering

Universiti Teknologi Malaysia

MAY 2008

iii

DEDICATION

Who Always Pushes Me Forward My Father.

Who Takes Care of Me Growing Up My Mother.

Whom Take My Success As Guide For Their Success My Brothers.

Who Smiles For My Smile My Wife.

Who Gave Me the Knowledge My Lecturers.

Whom Joined Me This Way My Classmates.

Who Ever Supported Me To Accumulate This Research. . ! ! !

Abdurahim Almabruk Shatewi

iv

ACKNOWLEDGEMENTS

First I wish to express my gratitude and greats to Allah to facilitate joining this

interesting course in University Technology Malaysia. Second, I wish to express my

appreciation and big thanks to Associate Professor Dr. Sanjayan Velautham for his

guidance and concern for this project for a better research performance. It was a nice

experience to have him as my project supervisor. Thirdly, I wish to express my thanks

to Kolej 10 Management for their concern. And, I wish to thank Malaysian Metrology

Department PJ for their corporation. Finally, I wish to express my thanks to William

Solomon Pakinathan for his assistance during this research.

Abdurahim Almabruk Shatewi

v

ABSTRAK

Kajian yang telah dijalankan ini adalah berkenaan penggunaan air hujan sebagai

bekalan air tambahan bagi kawasan penempatan. Kajian ini menerangkan penggunaan

sistem pengumpulan air hujan yang boleh diaplikasikan bagi kawasan penempatan

dengan tambahan sistem penyejuk pasif (passive cooling system). Analisa telah

dijalankan dengan membina pengkalan data air hujan bagi kawasan kajian tersebut.

Penggunaan air bulanan bagi isirumah telah dianggarkan bagi mengenal pasti

kapasiti/ukuran untuk sistem pengumpulan air hujan tersebut. Analisa yang telah

dijalankan ini seterusnya boleh digunakan bagi mendapatkan kapasiti optima sistem

pengumpulan air hujan itu. Satu sistem penyejuk pasif yang menggunakan air hujan

sebagai agen penyejuk bertindak untuk mengurangkan suhu dalaman. Sistem penyejuk

pasif ini akan menyumbang kepada pengurangan suhu dalaman dan kapasiti penyejukan

sistem penghawa dingin yang seterusnya mengurangkan penggunaan tenaga elektrik

secara keseluruhannya. Satu analisa juga akan dijalankan keatas sistem prototype bagi

mendapatkan kos sebenar dari segi ekonomi yang boleh diguna pakai bagi kawasan

penempatan. Kajian dari segi ekonomi ini juga merangkumi penjimatan untuk bil air dan

elektrik. Penjimatan ini seterusnya boleh digunakan bagi mendapatkan tempoh bayaran

balik yang mudah bagi pelaburan permulaan untuk membina sistem tersebut. Dari kajian

ini kita boleh membuat perbandingan dan selanjutnya dapat menentukan

kebolehupayaan untuk menjalankan kajian ini dari segi penjimatan kewangan dan

aplikasi jangka masa panjang bagi sumber air.

vi

ABSTRACT

The study on the use of rainwater as a supplementary water supply for residential

dwellings was conducted. This study elaborates rainwater harvesting systems that can be

applied at residential dwellings with an additional passive cooling system. The analysis

was conducted by building a database of rainfall in the test area. The monthly household

use was estimated to determine the sizing for the rainwater harvesting system. This

analysis was then used to determine the optimum size of the overall rainwater harvesting

system. A passive cooling system using rainwater as the cooling agent was designed to

reduce indoor temperatures. This passive cooling would contribute to the reduction of

the indoor temperatures and the cooling load of the air conditioning system, which will

in turn, reduces electrical energy consumption. A proposed cost analysis will be

conducted on the prototype system to determine its economic feasibility to be applied at

residential dwellings. This economic review will also included the savings from water

and electricity bills. These savings will be used to determine the simple payback period

on the initial investment to build the systems. From the study we can make some

comparisons and conclude the viability of implementing the system in terms of

monetary savings and the long term application of a sustainable and renewable source of

water.

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TABLE OF CONTENTS

CHAPTER TITLE PAGE

DECLARATION i

DEDICATION ii

ACKNOWLEDGEMENTS iii

ABSTRACT iv

ABSTRAK v

TABLE OF CONTENTS vi

LIST OF TABLES xi

LIST OF FIGURES xii

LIST OF SYMBOLS xvi

1 INTRODUCTION 1

1.1 Introduction 1

1.1.1 Brief History 2

1.1.2 Cooling Energy Consumption 2

1.2 Problem Statement 4

1.3 Aim And Objectives Of Study 4

1.4 Scope Of Study 5

2 LITERATURE REVIEW 6

2.1 Introduction 6

2.2 Rainfall Runoff Available 7

2.3 Harvested Rainwater Quality 7

viii

2.4 Rainwater Harvesting System 8

2.4.1 Tank 9

2.4.2 First Flush Diverters 10

2.4.3 Leaf Screen 11

2.5 Passive Cooling Techniques 12

2.6 Evaporative Cooling To Supply Cool Air 13

2.6.1 Evaporative Cooling Systems 14

2.6.1.1 Direct Evaporative System 14

2.6.1.2 Indirect Evaporative Cooler 14

2.6.1.3 Indirect-Direct Evaporative Cooler 15

2.6.2 Evaporating Cooling Advantages 16

2.7 Ventilation To Remove The Heat 17

2.7.1 Natural Ventilation 17

2.7.1.1 Fan Ventilation 17

2.7.1.2 Attic And Roof Ventilation 17

2.7.1.3 Solar Chimneys 18

2.8 Block Heat From Entering The Building 18

2.8.1 Shading 19

2.8.1.1 Exterior Shading 19

2.8.1.2 Interior Shading 20

2.8.2 Roof Insulation 20

2.8.2.1 Painting By White Cement 26

2.8.2.2 Vermiculite–Cement Thermal Insulation 26

2.8.2.3 Roof Pond Cooling And Heating 26

2.8.2.4 Evaporative Cooling 26

2.8.2.5 Broken White Glazed Tile Pieces Stuck

Over The Roof 27

2.8.2.6 Air Void Thermal Insulation on the roof 27

2.8.2.7 Sania Thermal Insulation 27

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3 RESEARCH METHODOLOGY 29

3.1 Introduction 29

3.2 A Selection Case Study 30

3.3 Rainwater Harvesting System Design 31

3.4 Passive Cooling System Design (Spray Water On The

Roof) 32

3.5 Fabrication And Installation Of Both Systems Prototype 33

3.6 Prototype Testing And Checking 33

3.7 Experimental Data Acquisitions 33

3.7.1 Rainwater Harvesting System Data 33

3.7.2 Spray Water On The Roof System Data 34

3.8 Result Analysis Of Technical Data 34

4 RAINWATER HARVESTING DESING CONCEPTION

AND CALCULATIONS 35

4.1 Introduction 35

4.2 The Conception Of Design 35

4.2.1 Catchment Surface 36

4.2.1.1 Metal 37

4.2.1.2 Clay/Concrete Tile 37

4.2.1.3 Composite Or Asphalt Shingle 38

4.2.1.4 Wood Shingle, Tar, And Gravel 38

4.2.2 The Amount Of Rainwater 38

4.2.3 Conveyance Systems (Gutters And Downspouts) 39

4.2.3.1 Gutters 40

4.2.3.2 Downspouts 41

4.2.4 Roof Wash (Leaf Screens And First-Flush Diverters) 41

4.2.4.1 Leaf Screens 41

4.2.4.2 First-Flush Diverters 42

4.2.5 Storage Tanks 43

x

4.2.5.1 Storage Tank Basics 44

4.3 Rain Water Harvesting Calculations And Fabrication 44

4.3.1 Catchment Surface 46

4.3.2 Conveyance Systems (Gutters And Downspouts) 47

4.3.2.1 Gutters 47

4.3.2.2 Downspouts 47

4.3.3 Roof Wash (Leaf Screens And First-Flush 49

4.3.3.1 Leaf Screen 49

4.3.3.2 First Flush Diverter 50

4.3.4 The Tank 53

4.3.4.1 The Tank Volume Calculation 54

4.3.5 The Distribution Pipes 55

4.3.6 The Pump 55

4.3.7 The Water Spry On The Roof Pipe 56

4.3.7.1 First Trail 57

4.3.7.2 Second Trail 59

5 RESULTS AND ANALYSIS 61

5.1 Introduction 61

5.2 Rainwater Harvesting 61

5.2.1 Rainwater Harvesting System 61

5.2.2 The Harvested Rainwater 63

5.2.3 Harvested rainwater quality 66

5.3 The Passive Cooling System (Spray Water On The Roof) 67

5.3.1 The Experimental Results Of Temperature

Distribution 70

5.3.1.1 Dry Test 70

5.3.1.2 Continued Spray Water On The Roof 73

5.3.1.3 Intermittent Spray Water On The Roof 77

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5.3.2 Passive cooling results analysis 82

5.3.2.1 Water tank temperature 82

5.3.2.2 Roof temperature 83

5.3.2.3 Room temperature 85

5.3.3 Water losses during the passive cooling tests 86

5.3.4 Actual pump working duration time 87

6 TECHNO-ECONOMICS ANALYSIS 90

6.1 Introduction 90

6.2 Techno-Economics of Rainwater Harvesting 90

6.2.1 Estimation of water demand 90

6.2.2 The harvested rainwater amount by a house roof 91

6.3 Techno-Economics of Cooling By Spray The Water On

The Roof95

6.3.1 The electrical consumption of the water pump and

the water losses 95

6.3.2 Heat gain reduction through the roof 96

6.3.3 Passive cooling system water amount needed 101

6.3.4 The cost of the system equipment and installation 101

6.4 The Techno-Economics for Actual House 102

6.4.1 Harvested rainwater saving 102

6.4.2 The saving due to the cooling by intermittent spray

water on the roof 103

6.4.3 The cost of the system equipment and installation

for actual house 103

7 CONCLUSION AND RECUMENDATION 105

7.1 Conclusion 105

7.2 Recommendation 106

REFERENCES 107

Appendices A - C 110-117

xii

LIST OF TABLES

TABLE NO. TABLE TITLE PAGE

2.1 Harvested rainwater quality results 8

2.2 Performance of different passive techniques 28

4.1 Runoff coefficients based on surface type 39

5.1 Theoretical and practical harvested rainwater for few days 64

5.2 Two harvested rainwater samples analysis 66

5.3 Water losses 87

5.4 Pump actual working duration time 88

5.5 comparison between continued sprayed and intermittent methods

88

6.1 Indoor Water Demand 91

6.2 Outdoor Water Demand 91 6.3 Pump electrical consumption and water losses for all the tests 96

6.4 Roof and Room temperatures for both Dry and Wet roofs 98

6.5 System cost details 102

6.6 Compulsory parts cost details 103

xiii

LIST OF FIGURES

TABLE NO. TITLE PAGE

2.1 Min and Max Rainfall Data for Johor 7

2.2 Rainwater Harvesting System 9

2.3 Polypropylene and Galvanized Steel Tanks 10

2.4 Stand Pipe First Flush Diverter with Ball Valve 11

2.5 Leaf Screen 12

2.6 Direct evaporative system 14

2.7 Indirect evaporative cooler 15

2.8 Indirect-direct evaporative cooler 16

2.9 Types of roof vents. 18

2.10 Summer and winter roof overhang

19

2.11 Bar roof with out any treatment 21

2.12 Roof with insulation beneath 21

2.13 Wetted roof surface (evaporative cooling) 22

2.14 Roof with movable insulation and roof pond open pond during night

23

2.15 WhiteCapTM Roof Spray Cooling System 24

3.1 Flowchart of the research methodology 30

3.2 Rainwater harvesting system 31

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3.3 Passive cooling systems (spray water on the roof) 32

4.1 Footprint area of catchment surface 37

4.2 Dowenspots – roof area relation 41

4.3 Leaf screen 42

4.4 First-flush diverters pipe 44

4.5 Case study in kolge 10 UTM Skudi 45

4.6 Sketch for the building including the systems components 45

4.7 The complete system installed to the building 46

4.8 The downspouts pipes 48

4.9 The gutters after the installation 49

4.10 Leaf Screen 50

4.11 The dimensions of the first flush divert 52

4.12 The first flush diverts 53

4.13 Polyethylene tank 54

4.14 Tank dimensions (sketch drawing) 55

4.15 Distribution pipes and Water pump 56

4.16 Water spray first trail 57

4.17 Water spray pipe first trail 58

4.18 First trail wet roof surface 58

4.19 Water spray second trail 59

4.20 Second trail wet roof surface 60

5.1 Sketch for the tank dimensions 63

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5.2 Fully shading roof 68

5.3 Six point’s data logged 69

5.4 Dry test 1-1 71

5.5 Dry test 1-2 72

5.6 Wet roof tests 2-1 73




5.10 Intermittent spray water tests 3-1 78




5.14 Water tank temperatures for all the tests 82

5.15 Water tank temperatures for no sunny tests 83

5.16 Roof temperatures for all the tests 84

5.17 Roof temperatures for no sunny tests 84

5.18 Room temperatures for all the tests 85

5.19 Room temperatures for no sunny tests 86

6.1 Annual rainfall for the last ten years 92

6.2 Monthly rainfall 2007-08 93

6.3 Monthly harvested rainwater 2007-08 93

6.4 Harvested rainwater Daily avarage per month 2007-08 94

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6.5 Monthly extra harvested rainwater 94

6.6 Daily average extra harvested rainwater 95

6.7 Heat gain for both dry and wet roof of cas study bulding 99

6.8 The reduction heat gain cause of wet roof of case study

building

99

6.9 Heat gain for both dry and wet roof for actual house 100

6.10 The reduction heat gain cause of wet roof for actual house 101

6.11 System installed to actual house 104

xvii

LIST OF SYMBOLS

A1 - Cross-section area of downspouts pipe (1)

A2 - Cross-section area of downspouts pipe (2)

A3 - Cross-section area of main downspouts pipe

Aroof - Catchment surface footprint area

COP - Air-condition unit coefficient of performance

CR - Run of coefficients

D(0.85) - The deference (WT - W(0.85))

D(0.95) - The deference (WT - W(0.95))

H - Water level height in the tank

H - Pump head

HP - Pump Hours power

Lmax - Maximum pipe length

Lmin - Minimum pipe length

m1 - Water mass flow rate through downspouts (1)

m2 - Water mass flow rate through downspouts (2)

m3 - Water mass flow rate through main downspouts

Q - Pump Water flow

Q - Heat transfer rate

xviii

Qcooling - The removed heat by air-condition unit

R0 - Overall thermal resistance

TD - Temperature difference

TH - High temperature (roof)

TL - Low temperature (room)

U - Overall heat transfer coefficient

V - Water volume (liter)

V1 - Tank Rectangular part volume

V2 - Tank parabolic part volume

W(0.85) - Calculated Harvested rainwater when (CR = 0.85)

W(0.95) - Calculated Harvested rainwater when (CR = 0.95)

Wcooling - The energy consumption by the air-condition unit

WHarvested - Harvested rainwater in liters

WRainfall - Rainfall amount in mm

WT - Harvested rainwater amount in the tank

Y - Parabolic width on the water level

1

CHAPTER 1

INTRODUCTION

1.1 Introduction

The never-ending exchange of water from the atmosphere to land and the oceans

and back again is known as the hydrologic cycle. All forms of precipitation (hail, rain,

sleet, and snow), and consequently all movement of water in nature, forms part of this

cycle. Precipitation stored in streams, lakes and in soil evaporates while water stored in

plants transpires to store of water in the atmosphere. When the atmospheric conditions

reach a level of super saturation, a stat achieved as a result of increased humidity

combined with changes in temperature and pressure, this water is released in the form of

rain, sleet, snow or hail, which falls as a result of the force of gravity to the earth. The

cycle continues, and results in shifting water from sea level all the way into the

mountains and back into rivers, lakes and the sea etc.

Rainwater harvesting is the collection and storage of rainwater from roofs or

catchment surface for future use. The collected water is stored in tanks for future use.

The usage way (water distribution) is depending on the rainwater applications. Did you

know that although 70% of the earth is covered with water, only 3% of this water is

fresh water? Out of this, 2% is locked in the form of ice, and it is only the balance 1% of

water that recycles through the evaporation, condensation cycle, that flows into the

rivers and lakes, to be used mankind [1]. So, the aim of this technique is to collect fresh

water (rainwater) to improve the mankind uses especially in dry regions. Rainwater is

2

valued for its purity and softness. It has a nearly neutral pH, and is free from

disinfection by-products, salts, minerals, and other natural and man-made contaminants

accept the development area (acid rain). If the rain fall persists for long time only the

fist part of rain will be bulleted.

1.1.1 Brief history

Collecting and storing rainwater is not a new idea. While the origin of rainwater

catchments systems are not known precisely, historical evidence suggests structures for

holding runoff water date back to the third millennium BC[2]. Historical structures

range from saucer like ground catchments and below ground cisterns to above ground

rooftop runoff storage tanks, have been found in numerous locations in Middle Eastern,

Asian and Mediterranean countries as Negev desert, , India, Greece, Italy, Egypt,

Turkey and China. It is found in Mexico, Taxes and Arizona as well. Historically,

harvested rainwater provided water for daily life use as drinking, cooking, washing and

landscape watering. Once urban areas started to develop, centralized water supply

systems replaced the need to harvest water [3].

1.1.2 Cooling energy consumption

The main contributor to increasing atmospheric carbon dioxide (CO2)

concentration is the combustion of fossil fuels from electricity generation, commercial

and domestic uses. The demand for energy is expected to grow rapidly in developed

countries as well as in the developing countries as they attempt to obtain a higher

standard living. This increase energy demand and consequently increase carbon dioxide

concentration in the atmosphere.

3

As energy costs rise, and the public becomes more aware of the environmental

damage arising from current energy use patterns. In most of hot just as much energy, if

not more, may be used for cooling to achieve the thermal comfort. Refrigeration and

air conditioning systems have a major impact on energy demand with roughly 30% of

total energy consumption in the world [4]. With fossil fuels fast depleting, it is

imperative to look for refrigeration systems that require less high-grade energy for their

operation. A minimum amount of energy should be use for cooling.

Typically, air-conditioning accounts for 60% of electricity consumption in

commercial buildings in the hot and humid Southeast Asian Region [5]. Residential

households in urban and suburban areas use air-conditioning for thermal comfort

increasingly. Typically, one air-conditioner will be initially installed in the main

bedroom of a house. With increase in disposable income, a household would add

second, third and possibly more units to other bedrooms and common rooms. There is

increasing penetration of air-conditioning, both in terms of number of households and in

terms of number of air-conditioners per households, that the air-conditioning industry

reports increasing annual number of units sold that approaches 5% of the number of

households in Malaysia and Thailand. When air-conditioning is used, it contributes 70%

of electricity consumption in a household [5]. Alternative methods, using passive

cooling techniques, can assist in reducing the conventional energy consumption in

buildings. Researchers have shown that about 50% of the heat gains for a single-story

building come through the roof [6]. The conventional approaches to reduce heat flux

through the roof into a building include increasing thickness of the roof, providing

insulation and false ceilings, shading the roof and using reflective finish or coating. In

hot dry areas, however, this can be achieved by an open pond, thin water film and

spraying water on the roof [7]. The passive cooling is a feasible technology that can

reduce mechanical cooling and energy requirement in air conditioning application that

will effect to decrease emissions from electricity generation.

4

1.2 Problem Statement

Malaysia is tropical region (hot, humidity and raining weather). Rainwater

harvesting can be supplementary water source for residential dwelling. The study will

predicts how much rain water can be harvested. Also it will show, whether the harvested

rainwater will be partial coverage of the water requirements of daily usage (drinking,

cooking, shower, washing, toilet flush, washing front yard, watering plants and washing

cars …ect), during whole of the year, or it will be full coverage. The harvesting

rainwater can be used for passive cooling technique (spry water on the roof) to reach the

thermal comfort.

1.3 Aim and Objectives of Study

An overall goal of this study is to meet water demand for residential dwelling.

The study will show how much the harvested rain water well reduces the usage of the

public water supply. In other wards, how much the water bill can be reduced? On the

other hand, by using the harvesting rainwater for passive cooling technique (spry water

on the roof), well decrease the cooling electrical energy (air-condition) to reach the

thermal comfort.

The objectives of this study by using case study of rainwater harvesting system and

passive cooling technique (spray water on the roof) as the following:

1. Fundamental study of rainwater systems used for rain harvesting.

2. To Acquit observables facts in implementing rainwater harvesting techniques

with residential dwellings.

3- To find out the performance passive cooling technique (spraying water on the

roof).

107

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Johor Bahru, 2005.

2. Heather Kinkade-Levario, ASLA, Rainwater Harvesting And Storm Water

Recycling, national conference 2002, http://www.forgottenrain.com.

3. Dr. Hari J. Krishna, P.E., The Texas Manual on Rainwater Harvesting, Texas Water

Development Board, 3rd Edition, , Contract Manager, Austin, Texas.

4. S. Arivazhagan, R. Saravanan, S. Renganarayanan, Experimental studies on HFC

based two-stage half effect vapor absorption cooling system, Applied Thermal

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as A passive Cooling Option in Hot Humid Climate. Building and Environment. 42

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Jabatan Meteorologi Malaysia, Kementerian Sains Teknologi dan Inovasi, 20th

April 2007.

9. Patricia H. Waterfall, Rainwater Harvesting for Landscape Use, 2nd Edition,

Extension Agent, University of Arizona, 2006.

108

10. Mohamad Afifi Abdul Mukti et. all, Rainwater Harvesting an Opportunity

Neglected, University of Technology Malaysia, 2004.

11. D. Brett Martinson, Terry Thomas, Quantifying the First Flush Phenomenon,

Development Technology Unit, School of Engineering, University of Warwick,

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12. Lib Reid-McGowan. Passive Cooling for Your North Carolina Home. North

California solar center. 2000.

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Environment, 38 (2003) 109 – 116.

14. R. A. Bucklin, J. D. Leary, D. B. McConnell, E. G. Wilkerson. Fan and Pad

Greenhouse Evaporative Cooling Systems1. University of Florida IFAS. 2002.

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19. Dilip Jain. Modeling of Solar Passive Techniques for Roof Cooling in Arid

Regions, India, Building and Environment, 41 (2006) 277–287.

20. Nogales Demonstration, Dennis DeConcini Poe. WhiteCapTM Roof Spray Cooling

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109

21. Sudaporn Chungloo, Bundit Limmeechokchai. Application of Passive Cooling

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