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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
AHMAD SYAFIK SURAIDI BIN SULAIMAN
Master of Science
Universiti Putra Malaysia
2008
EFFECT OF EVAPORATIVE COOLING BY MISTING FAN ON
MICROCLIMATE OF A NATURALLY VENTILATED GREENHOUSE
By
AHMAD SYAFIK SURAIDI BIN SULAIMAN
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
AHMAD SYAFIK SURAIDI BIN SULAIMAN
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
AHMAD SYAFIK SURAIDI BIN SULAIMAN
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.
_______________________________________
AHMAD SYAFIK SURAIDI BIN SULAIMAN
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.