universiti putra malaysia effect of evaporative...

UNIVERSITI PUTRA MALAYSIA

EFFECT OF EVAPORATIVE COOLING BY MISTING FAN ON MICROCLIMATE OF A NATURALLY VENTILATED GREENHOUSE

AHMAD SYAFIK SURAIDI BIN SULAIMAN

FK 2008 93

EFFECT OF EVAPORATIVE COOLING BY MISTING FAN ON MICROCLIMATE OF A

NATURALLY VENTILATED GREENHOUSE


Master of Science

Universiti Putra Malaysia

2008

EFFECT OF EVAPORATIVE COOLING BY MISTING FAN ON

MICROCLIMATE OF A NATURALLY VENTILATED GREENHOUSE

By


Thesis Submitted to the School of Graduate Studies, Universiti Putra Malaysia, in

Fulfillment of the Requirement for the Degree of Masters

October 2008

ii

Abstract of thesis presented to the Senate of Universiti Putra Malaysia in Fulfillment of the requirement for the degree of Master of Science

EFFECT OF EVAPORATIVE COOLING BY MISTING FAN ON

MICROCLIMATE OF A NATURALLY VENTILATED GREENHOUSE

By


October 2008

Chairman: Desa Bin Ahmad, PhD, P.Eng

Faculty: Engineering

The environment that suits the growth of most kind of crops is very crucial in order to

guarantee high quality yields that can be controlled according to the desired parameters and

not easily damaged or stunted during its growth. Naturally Ventilated Greenhouse (NVGH)

is one of the methods to attain the controlled environment and it is proven to be highly

effective in controlling the suitable environment for most kind of plants or vegetables.

Furthermore, NVGH can save energy where mechanical, electrical and labour power

required is very small, require no controlling procedures or complicated handling, suitable to

tropical climate and the cost to build is very low compared to other plant protection

structures. The tropical country climate is inconsistent all year long and even though the

NVGH can control its environment, it has some weaknesses in which the air and the

temperature inside the NVGH can be easily influenced by the outside conditions of the

structure. Most kinds of crops require temperature between 20-35ºC and relative air humidity

iii

between 80-90% in order to ensure a standard quality harvest. An evaporative cooling system

using four misting fans was studied inside a NVGH of 10m width, 50m long and 4m high.

The aim was to modify the environment inside the NVGH so that it could control the inside

temperature between 20-35ºC and relative humidity between 80-90% all day long. Other

environmental parameters such as light intensity, outside air temperature and carbon dioxide

were also studied in order to see the correlation and modification effect on the environment

in the NVGH. All environment data studied was recorded and statistically analyzed using the

Statistical Package for the Social Science (SPSS) software. Temperature inside the NVGH

was found to be strongly correlated with time (min), outside temperature, light intensity and

relative air humidity while carbon dioxide only gave a moderate effect on the temperature

inside the NVGH. The correlation equation between temperature inside the NVGH is shown

in the following equation: T1= -0.001 (T) +0.001 (L)-0.103 (H) +0.447 (T2) +21.949 where

T1= inside temperature (°C), T= Time (min) L= Light Intensity (W·m-2), H=Relative

Humidity (%) and T2= outside temperature (°C). The misting fans also turned out to be

effective in controlling the temperature inside the NVGH to remain between 20-35ºC and

relative air humidity between 80-90% all day long compared to NVGH that is not equipped

with the misting fans. The inside temperature, light intensity and carbon dioxide under the

NVGH attached with misting fans were found to be lower than NVGH without misting fans.

The relative humidity inside the NVGH attached with misting fans was found to be higher

than the NVGH without misting fans. Crop such as chili and cauliflowers were able to grow

favourably inside the NVGH attached with the misting fans and the crop growth performance

indicates a linear trend during the growing period.

iv

Abtsrak tesis yang dikemukakan kepada Senat Universiti Putra Malaysia sebagai memenuhi keperluan untuk ijazah Master Sains

KESAN SISTEM PENYEJUKAN PENYEJATAN MENGGUNAKAN KIPAS KABUS TERHADAP PERSEKITARAN DALAMAN RUMAH HIJAU

PENGALIHAN UDARA SECARA SEMULAJADI

Oleh


Oktober 2007

Pengerusi: Desa Bin Ahmad, PhD, P.Eng

Fakulti: Kejuruteraan

Keadaan persekitaran yang sesuai adalah amat penting untuk tumbesaran pelbagai jenis

tanaman. Keadaan persekitaran yang sesuai ini dapat menjamin hasil tuaian yang berkualiti,

terkawal dalam parameter yang diingini, mencapai target dan tidak rosak atau pun bantut

sepanjang tumbesaran. Rumah hijau pengalihan udara secara semulajadi (NVGH) adalah

salah satu daripada kaedah untuk mendapatkan persekitaran yang terkawal dan ianya

memang terbukti berkesan dalam mengawal persekitaran yang sesuai untuk keperluan

tumbesaran tanaman. NVGH ini boleh menjimatkan tenaga dimana kuasa mekanikal,

elektrikal dan bilangan buruh yang digunakan adalah kecil, tidak memerlukan prosedur

pengawalan dan penjagaan yang rumit, sangat sesuai dengan iklim di negara tropika dan

memerlukan kos yang kecil untuk dibina berbanding struktur perlindungan tanaman yang

lain. Iklim semulajadi negara tropika secara puratanya adalah tidak konsisten sepanjang

tahun dan walaupun NVGH dapat mengawal persekitarannya, ia juga mempunyai kelemahan

dimana udara dan suhu didalam struktur mudah dipengaruhi oleh persekitaran diluar struktur

v

NVGH tersebut. Kebanyakan tanaman memerlukan suhu diantara 20-35ºC dan kelembapan

relative udara diantara 80-90% untuk memastikan hasil yang dituai memperolehi standard

kualiti yang ditetatpkan. Empat buah kipas kabus (Misting Fan) telah digunakan didalam

NVGH yang berkeluasan 10m lebar, 50m panjang dan 4m tinggi untuk mengubahsuaikan

persekitaran dalaman struktur tersebut. Ini supaya NVGH dapat mengawal suhu sehingga

berada diantara 20-35ºC dan mempuyai kelembapan udara relatif diantara 80-90%

sepanjang hari. Beberapa parameter persekitaran yang lain seperti kekerapan cahaya,

kandungan karbon dioksida dan suhu udara diluar struktur NVGH juga turut dikaji untuk

melihat hubung-kait dan kesan terhadap pengubahsuaian persekitaran didalam NVGH.

Semua data-data parameter persekitaran yang dikaji telah direkod dan dianalisis secara

statistik dengan menggunakan perisian Statistical Package for the Social Science (SPSS).

Suhu didalam NVGH didapati berhubung-kait secara kuat dengan masa (min), suhu luaran,

kekerapan cahaya dan kelembapan udara relatif manakala karbon dioksida pula hanya

memberi kesan yang sederhana terhadap suhu didalam NVGH. Persamaan hubung-kait

diantara suhu didalam NVGH dilengkapi kipas kabus ditunjukkan dengan persamaan ini; T1=

-0.001 (T) +0.001 (L)-0.103 (H) +0.447 (T2) +21.949 dimana T1=suhu dalaman (°C), T=

masa (min), L= light intensity (W·m-2), H= kelembapan udara relatif (%) dan T2= suhu luaran

(°C). Kipas kabus juga didapati telah berjaya mengawal suhu didalam NVGH berada diantara

20-35ºC dan kelembapan udara relatif diantara 80-90% sepanjang hari berbanding struktur

NVGH yang tidak dilengkapi kipas kabus. Suhu, kekerapan cahaya dan kandungan karbon

dioksida didalam NVGH yang dilengkapi kipas kabus didapati lebih rendah daripada NVGH

yang tiada kipas kabus. Kelembapan relatif udara didalam NVGH yang dilengkapi kipas

kabus pula didapati lebih tinggi daripada NVGH yang tiada kipas kabus. Tanaman seperti cili

vi

dan kubis bunga pula didapati boleh menbesar secara subur didalam NVGH yang dilengkapi

kipas kabus. Ini dapat dilihat melalui graf keupayaan pembesaran bagi cili dan kubis bunga

yang menunjukkan trend yang linear sepanjang masa pembesaran tanaman tersebut.

vii

ACKNOWLEDGEMENTS

The author wishes to express his sincere gratitude and thanks to his supervisor

Prof.Ir.Dr.Desa Bin Ahmad for his assistance, guidance and supervision during the

conduct of the study. Heis also indepted to Dr. Rezuwan Bin Kamarudin and Assoc. Prof.

Dr. Zakaria Bin Wahab, his co-supervisors for their guidance and suggestions.

Special thanks to Dr. Mahmud Bin Shahid and En. Yusof Bin Hapzah from Horticultural

Research Centre MARDI Serdang for their help and advice during the planting of

selected crops and not to forget to En. Mohd Hafiz Bin Hashim from the Mechanization

and Automation Research Centre MARDI Serdang for providing the facilities to be used

to complete his research.

The author is grateful to all members and technicians of the Faculty of Engineering for

allowing and providing the facilities to complete his research. He also would like to

record his gratitude to his lecturers and friends who always motivated and supported him

to accomplish his study.

His utmost appreciation and heartfelt gratitude goes to his beloved wife, parents and all

family members for their patience, understanding, support and sacrifices throughout his

study.

viii

I certify that an Examination Committee has met on 31 October 2008 to conduct the final examination of Ahmad Syafik Suraidi Bin Sulaiman on his Masters of Science Thesis entitled “Effect of Evaporative Cooling by Misting Fan on Microclimate of a Naturally Ventilated Greenhouse” in accordance with Universiti Pertanian Malaysia (Higher Degree) Act 1980 and Universiti Pertanian Malaysia (Higher Degree) Regulations 1981. The Committee recommends that the candidate be awarded the relevant degree. Members of the Examination Committee are as follows: Nor Mariah Adam, Ph.D, P.Eng Associate Professor Faculty of Engineering Universiti Putra Malaysia (Chairman) Mohd Amin Mohd Som, Ph.D, P.Eng Professor Faculty of Engineering Universiti Putra Malaysia (Internal Examiner) Jamarei Othman, Ph.D. Faculty of Engineering Universiti Putra Malaysia (Internal Examiner) Mohammud Che Husain, Ph.D. Deputy Director Program Mekanisasi Pengeluaran Pusat Peyelidikan Mekanisasi dan Automasi Ibu Pejabat MARDI Serdang (External Examiner) ___________________ Hasanah Mohd Ghazali, PhD Professor/Deputy Dean School of Graduate Studies Universiti Putra Malaysia Date: 14 November 2008

ix

This thesis were submitted to the Senate of Universiti Putra Malaysia and has been accepted as fulfillment of the requirement for the degree of Master of Science. The members of the Supervisory Committee were as follows: Desa Bin Ahmad, PhD, P.Eng Professor Faculty of Engineering Universiti Putra Malaysia (Chairman) Rezuwan Bin Kamarudin, PhD Research Officer Mechanization and Automation Research Centre Malaysian Agricultural Research and Development Institute (Member) Zakaria Bin Wahab, PhD Associate Professor Faculty of Agriculture Universiti Putra Malaysia (Member) ______________ HASANAH MOHD GHAZALI, PhD. Professor and Dean School of Graduate Studies Universiti Putra Malaysia

Date: 14 November 2008

x

DECLARATION

I hereby declare that the thesis is based on my original work except for quotations and citations which have been duly acknowledged. I also declare that it has not been previously or concurrently submitted for any degree at UPM or other institutions.

_______________________________________


Date:

xi

TABLE OF CONTENTS

Page ABSTRACT ii ABSTRAK iV ACKNOWLEDGEMENTS Vii APPROVAL Viii DECLARATION X LIST OF TABLES XVii LIST OF FIGURES XiX

1.0 INTRODUCTION 1

1.1 Problem statement 5

1.2 Objectives 6

1.3 Contribution of knowledge 7

2.0 LITERATURE REVIEW 8

2.1 Crop protection structure (greenhouse) technologies 8

2.2.1 Tropical greenhouse structure and controlled 8

environment for temperate vegetable production

2.1.2 Development of tropical and sub-tropical 9

greenhouses and in houses production systems

2.1.3 Controller for greenhouses 11

2.1.4 Natural ventilation rate of greenhouse 12

2.1.5 Naturally ventilated greenhouse 13

xii

2.2 Cooling System for greenhouse 16

2.2.1 Natural ventilation 17

2.2.2 Forced ventilation 18

2.2.3 Mist/ fog system 19

2.2.4 Evaporative cooling efficiency of a fogging system 20

for greenhouse

2.2.5 Energy and water management in 21

evaporative cooling system

2.2.6 Development of hybrid photovoltaic cooling system 22

2.2.7 Cooling system components 24

2.2.8 Controlled environment 25

2.3 Crop Performance under the greenhouse 30

2.3.1 Crop-temperature relationship 30

2.3.2 Crop-light intensity relationship 31

2.3.3 Crops- CO2 relationship 32

2.3.4 Cauliflower physiology 33

2.3.5 Chili physiology 36

3.0 METHODOLOGY 37

3.1 Designing the cooling system 37

xiii

3.1.1 Construction of a naturally ventilated greenhouse 38

3.1.2 Designing the evaporative cooling system by using 39

misting fan inside a naturally ventilated greenhouse

3.1.3 Fan requirement 41

3.2 Measurement of misting fan efficiency inside a naturally ventilated 45

greenhouse

3.3 Cauliflower growth under the evaporative cooling system 48

3.3.1 Raising cauliflower seeds 49

3.3.2 Time of planting the cauliflowers 50

3.3.3 Land preparation 50

3.3.4 Land spacing for cauliflowers 51

3.3.5 Cauliflowers care after cultivation 52

3.3.6 Cauliflowers plant protection/ care 52

3.3.7 Harvesting the cauliflowers 53

3.4 Chili growth under misting fan cooling system 53

3.4.1 Chili Seedling 54

3.4.2 Chili plantation inside a naturally ventilated greenhouse 55

3.4.3 Chili maintenance 57

3.4.4 Chili growth 58

xiv

3.5 Data analysis 59

4.0 RESULTS AND DISCUSSION 60

4.1 Effects of misting fan on the microclimates of a naturally ventilated 60

greenhouse

4.1.1 Temperatures inside a naturally ventilated greenhouse 61

4.1.2 Relative humidity 66

4.1.3 Light intensity 68

4.1.4 Carbon dioxide 72

4.1.5 Misting fan efficiency inside a naturally ventilated 73

greenhouse

4.2 Statistical Analysis 76

4.2.1 Bivariate Correlations 77

4.2.2 Correlation Matrix 78

4.2.3 Coefficient 80

4.2.4 ANOVA Test 84

4.3 Yield of Cauliflowers grown 85

4.3.1 Cauliflowers stem diameter 87

4.3.2 Cauliflowers height 90

xv

4.3.3 Cauliflowers leaf width 93

4.3.4 Cauliflowers canopy dimensions 93

4.3.5 Cauliflowers curds 95

4.4 Yield of Chili Grown 96

4.4.1 Chili stems diameter 98

4.4.2 Chili height 99

4.4.3 Chili leaf width 101

5.0 CONCLUSIONS AND RECOMMENDATIONS 103

5.1 Conclusions 103

5.2 Recommendations 107

REFERENCES 108

APPENDICES 118

BIODATA OF THE STUDENT 132

LIST OF FIGURES

Figure Page

xvi

1.1: Naturally ventilated greenhouse 3

2.1: Misting fan 25

2.2: Cauliflower seed bed preparation 35

3.1: Opening of a NVGH 39

3.2: Misting fan at each zone inside a NVGH 40

3.3: Misting fan controller 40

3.4: Misting fan location inside a NVGH 44

3.5: Watchdog weather station 46

3.6: Location of the Watchdog weather station inside a NVGH 47

3.7: Watchdog data logger 47

3.8: Mechanization inside a NVGH 51

3.9: Cauliflower land spacing 52

3.10: Chili seed inside the nursery 55

3.11: Coco peat arrangement inside a NVGH 56

3.12: Chili transferred into coco peat 56

3.13: Chili stem tied to a metal pipe pole 57

3.14: Chili stems diameter 58

4.1: Temperatures inside a NVGH 62

4.2: Relationship between measured and calculated inside temperatures 64

4.3: Inside temperatures reduction percentage 65

4.4: Relative humidity inside a NVGH 66

4.5: Light intensity inside a NVGH 68

xvii

4.6: Relationship between measured and calculated light intensity 71

4.7: Carbon dioxide inside a NVGH 73

4.8: Temperature distributions under evaporative cooling system 74

4.9: Correlation matrix of misting fan effects on microclimates 79

inside a NVGH

4.10: Yield of Cauliflower 86

4.11: Cauliflower stem diameter 88

4.12: Cauliflower height 90

4.13: Cauliflower leaf width 92

4.14: Cauliflower canopy dimension 93

4.15: Cauliflower curd 95

4.16: Chili stem diameter 98

4.17: Chili Height 100

4.18: Chili leaf width 101

LIST OF TABLES

Table Page

xviii

3.1: Dimensions of Greenhouses structures 38

3.2: Classifications of fans 44

3.3: Unit for microclimates parameters 46

3.4: Parameter used to take crop growth performance and yield data 48

4.1: Microclimates inside a NVGH without misting fan. 60

4.2: Microclimates inside a NVGH with a misting fan 61

4.3: Misting fan performance inside a NVGH 75

4.4: Correlation between environmental parameters inside a 77

NVGH with misting fan.

4.5: The coefficients of regression line 81

4.6: Predicted and measured inside temperatures 83

4.7: ANOVA for microclimates inside a NVGH 84

4.8: Model Summary 85

4.9: Descriptive Statistics 85

4.10: Crop Performance Average Data 87

4.11: Yield of Cauliflowers 87

4.12: Chili growth 97

4.13: Yields of Chili 97

1

CHAPTER 1

INTRODUCTION

The environment-cooling systems design for agriculture requires understanding of the

complex interaction between the biological system within the space and the environment

provided to that system. The biotic system will have specific environmental needs where

its growth, production, and well-being are influenced by the environment. Concomitantly,

the biotic system will strongly influence condition within the air space. The aim of the

environment cooling is to create a balance favourable to both the biological and physical

systems. To be able to create such a balance successfully requires understanding of

physics, thermodynamics, mathematics through calculus, fluid mechanics, heat transfer,

mass transfer, refrigeration, weather phenomena, control theory and environmental

biology.

Greenhouse (crop protection structure) is conventionally used to create environment

suiting plant propagation year round, irrespective of external conditions. This may result

in conditions outside the human comfort range inside the greenhouse where tropical

vegetation is propagated. Greenhouse can have extended action as a non-habitable space

to an eventuate gross ventilation by encouraging warm air to vent out of the greenhouse,

with replacement air to flow from the abutting building to encourage ventilation there.

2

The greenhouse is also defined as a special construction which is used to protect plants

from undesirable climatic variation and to provide inside environmental conditions to suit

the cultivations of plants (Bin Qadhi and Haidrah, 1999). This technique is used to

increase the production rate of vegetables, fruits, flowers and to renew plants by using

new methods applied to control the surrounding conditions and to produce products at all

times of the year.

The naturally ventilated greenhouses (NVGH) rely primarily on the air blowing into a

windward side opening and out the open roof vents. Wind can also create a vacuum

pressure along the aerodynamically-designed roof vents to accelerate the outward flow of

hot air. A secondary, much smaller effect, is the air buoyancy. The air buoyancy helps to

move hot, humid air up and out of the greenhouse if there is no internal traps.

Nevertheless, any barrier to this process, such as gutter vents or wide internal framing,

can completely negate the effect. In all cases, including the open roof designs, it is

essential to have at least a very effective windward side inlet with multiple roof outlets.

This is to allow the air to move from the inlet to the outlet through the plants to have a

good ventilation.

The NVGH has a side netting functions as a cover which its porosity is enough to prevent

pest from entering the structures and remove the trapped internal air to the outside of the

greenhouse (Figure 1.1).

3

Figure 1.1: Naturally ventilated greenhouse

The NVGH have low energy requirements where no mechanical or electrical power is

used to ventilate the structure. It is also easily cooled in hot climate, has no ventilation

restrictions on the length of the greenhouse, the air temperature also can be maintained

very close to the outside air, has a very high ventilation rates and has low temperature

gradients across the greenhouse area.

The disadvantages of a NVGH include the difficulty in its design. It must be incorporated

with some forms of shade system, with no pad cooling and no micro insect screening

needed. Besides that, the plants near the side vent can be wind-damaged. This depends on

the wind speed and the wind direction. The vents are subjected to wind-damage while the

low light plants below the open vents can be sun-scorched.

4

The NVGH usually has more than one climates. In other words, there are microclimates

in a NVGH. These small climates are enclosed in one larger environment. A NVGH

frequently becomes too warm when a high level of light intensity occurs. If the high

temperatures are to be kept near or below outside ambient temperatures, some form of

cooling must be provided. This is important to study the correlation between the light

intensity to the temperatures under a NVGH.

Furthermore, numerous applications of environment control in agriculture require more

cooling temperatures than what can be provided by the ventilation alone. Temperatures

requirement for the best agricultural production typically is within the range of 20 °C to

35 °C. Day temperatures requirement for greenhouse crops is seldom higher than 35 °C.

Whenever the outdoor temperature is warm, maintaining the conditions within these

ranges can become impossible unless the alternative cooling is used.

The process of cooling off the environment inside the NVGH was done to improve the

conditions inside the structure to suit the growth of the crops. Hence, choosing the plant

is mainly a matter of knowing what the physiology, chemical and biological aspects

needed by the plant. It is important for us to know the kind of light intensity,

temperatures, relative humidity and carbon dioxide that each plant requires and how

much heat and moisture it needs to thrive. It is also important to choose the crops in order

to study the effects of cooling on their growth inside the NVGH.

universiti putra malaysia effect of evaporative...

Documents