IMPROVEMENT DESIGN OF SOLAR CHIMNEY

TEY NGUAN WUI

Bachelor of Engineering with Honors

(Mechanical and Manufacturing Engineering)

2008

IMPROVEMENT DESIGN OF SOLAR CHIMNEY

TEY NGUAN WUI

This project is submitted in partial fulfillment of the requirements for the degree of Bachelor of

Engineering with Honors

(Mechanical and Manufacturing Engineering)

Faculty of Engineering

UNVERSITY MALAYSIA SARAWAK

2008

Dedicate to:

My Beloved Family

And Friends

UNIVERSITI MALAYSIA SARAWAK

BORANG PENYERAHAN TESIS

Judul: IMPROVEMENT OF SOLAR CHIMNEY DESIGN .

.

SESI PENGAJIAN : 2008/2009

Saya TEY NGUAN WUI .

(HURUF BESAR)

mengaku membenarkan tesis * ini disimpan di Pusat Khidmat Maklumat Akademik, Universiti

Malaysia Sarawak dengan syarat-syarat kegunaan seperti berikut:

1. Tesis adalah hakmilik Universiti Malaysia Sarawak.

2. Pusat Khidmat Maklumat Akademik, Universiti Malaysia Sarawak dibenarkan membuat salinan

untuk tujuan pengajian sahaja.

3. Membuat pendigitan untuk membangunkan Pangkalan Data Kandungan Tempatan.

4. Pusat Khidmat Maklumat Akademik, Universiti Malaysia Sarawak dibenarkan membuat salinan

tesis ini sebagai bahan pertukaran antara institusi pengajian tinggi.

5. ** Sila tandakan (√) di mana kotak yang berkenaan

SULIT (Mengandungi maklumat yang berdarjah keselamatan atau

kepentingan Malaysia seperti yang termaktub di dalam AKTA

RAHSIA RASMI 1972).

TERHAD (Mengandungi maklumat TERHAD yang telah ditentukan oleh

organisasi/badan di mana penyelidikan dijalankan).

TIDAK TERHAD

Disahkan oleh

_________________________ ___________________________

(TANDATANGAN PENULIS) (TANDATANGAN PENYELIA)

Alamat tetap: 166, LRG Poh Kwong 3 Ir Dr MOHD. SHAHRIL OSMAN

Poh Kwong Park,

93150 Kuching,

Sarawak.

Tarikh: __________ Tarikh: __________

CATATAN * Tesis ini dimaksudkan sebagai tesis bagi Ijazah Doktor Falsafah, Sarjana, dan Sarjana Muda.

** Jika tesis ini SULIT atau TERHAD, sila lampirkan surat daripada pihak berkuasa/organisasi

berkenaan dengan menyertakan sekali sebab dan tempoh tesis ini perlu dikelaskan sebagai SULIT atau

TERHAD.

√

R13a

Approval Sheet

This Final Year Project attached here:

Title : IMPROVEMENT OF SOLAR CHIMNEY DESIGN

Student Name : TEY NGUAN WUI

Matrix No : 15420

Has been read and approved by:

_____________________ _ _________________

Ir Dr MOHD. SHAHRIL OSMAN Date

(Supervisor)

Date

(Internal Reader)

ii

ACKNOWLEDGEMENT

I would like to express his appreciations to whom have lent a hand in bringing

this project to a success within the given time frame.

Firstly, the author would like to thanks his supervisor, Ir Dr Mohammad Shahril

Osman for all his guidance and support provided throughout this project to ensure project

is carried out successfully with least obstacles.

Secondly, special thanks to the laboratory technicians including Mr. Masri Zaini,

Mr. Mohd. Rhyier Juen Abdullah and Madam Hasmiza Kontet are acknowledged on the

lab equipment advices, machineries operation method and technique supports.

The author would like to express his gratitude to his friends and fellow course

mates for their help and support throughout the project.

Lastly, the author family support is acknowledged for bringing this project to

move on until a success is achieved.

iii

ABSTRACT

Renewable energy has become more preferable to the society compare with

conventional energy. This project presents the design, fabrication and performance

analysis of the improved solar chimney power generator. The solar chimney apply hot air

rise concept to generate power. The design consists of a chimney tower connected on top

of the circular solar collector with a chimney support. Within the chimney tower lie two

generators, one above another to generate power. Below of the solar collector lays the

heat absorber tiles and water tubes. The water tubes absorb heat during the day time, and

release the heat during the night for the power generation. An air flow director is placed

below the chimney tower to direct the air into the tower and then turn the electrical

generators. In this project, air flow simulation and fabrication method were employed.

The performance of the solar chimney is dependent to the solar radiation, solar collector’s

size, chimney tower’s height, collector’s transparency and type of heat absorber. The

night operation performance is dependent on the water tube and heat absorber type. The

solar chimney is 4.2 meter diameter and 3.6 meter height. The simulation will simulate

the air behaviors within the solar chimney.

Keyword: Solar chimney, renewable energy

iv

ABSTRAK

Tenaga yang boleh diperbaharui semakin mendapat tempat di hati masyarakat

berbanding dengan tenaga yang tidak boleh diperbaharui. Projek ini bertujuan untuk

mengetengahkan reka bentuk, pembuatan serta analisa terhadap prestasi penjana kuasa

cerobong suria yang telah dipertingkatkan. Cerobong suria ini menggunakan konsep

udara panas untuk menghasilkan tenaga. Reka bentuknya terdiri daripada menara

cerobong yang dihubungkan dengan penyokong cerobong di atas pengumpul suria

berbentuk bulat. Terdapat dua penjana di dalam cerobong suria, bertindih di antara satu

sama lain untuk menjana tenaga. Di bawah pengumpul suria terdapat jubin penyerap haba

dan tiub air. Tiub air ini berfungsi untuk menyerap haba pada siang hari dan

membebaskan haba pada waktu malam untuk penjanaan tenaga. Sebuah pengarah aliran

udara diletakkan di bawah menara cerobong untuk mengarahkan aliran udara ke menara

dan kemudian memutarkan penjana electrik. Dalam projek ini, simulasi aliran udara dan

cara pembuatan diambil kira. Prestasi cerobong solar bergantung kepada radiasi solar,

saiz pengumpul solar, tinggi cerobong solar, kelutsinaran pengumpul dan jenis penyerap

haba yang digunakan. Prestasi pada waktu malam bergantung kepada tiub air dan jenis

penyerap haba. Cerobong asap inimempunyai diameter sebanyak 4.2 meter dan

berketinggian 3.6 meter. Simulasi akan digunakan untuk mengetahui kelakuan aliran

udara dalam cerobong suria.

v

TABLE OF CONTENTS

CONTENT Page

ACKNOWLEDGEMENT………………………………………………………. ii

ABSTRACT……………………………………………………………………… iii

ABSTRAK……………………………………………………………………….. iv

TABLE OF CONTENT…………………………………………………………. v

LIST OF TABLES……………………………………………………………….. ix

LIST OF FIGURES………………………………………………………………. x

NOMECULATURE….………………………………………………………….. xiii

CHAPTER 1 INTRODUCTION TO THE SOLAR CHIMNEY

1.1. Introduction………………………………………………………………… 1.

1.2. Objectives of the Project…………………………………………………... 3.

CHAPTER 2 LITERATURE REVIEW

2.1. Introduction ……………………………………………………………….. 4.

2.2. Solar Chimney Working Principle…………………………………………. 5.

2.3. Solar Chimney’s Structure…………………………………………………. 9.

2.3.1. Chimney Tower……………………………………………………………. 10.

vi

2.3.2. Turbine ……………………………………………………………………. 17.

2.3.3. Solar Collector…………………………………………………………….. 20.

2.3.4. Heat Absorber …………………………………………………………….. 28.

2.3.5. Water Tubes………………………………………………………………... 32.

2.4. Environment Factor Consideration………………………………………... 33.

2.4.1. Solar Radiation……………………………………………………………. 33.

2.4.2. Air Humidity …………………………………………………………….. 34.

2.4.3. Star-CD software ………………………………………………………….. 35.

CHAPTER 3 METHODOLOGY

3.1. Introduction……………………………………………………………….. 36.

3.2. Method and Approaches…………………………………………………... 37.

3.3. Work Plan………………………………………………………………….. 39.

3.4. Future Work……………..…………………………………………………. 41.

CHAPTER 4 ANALYSIS AND DESIGN OF THE SOLAR CHIMNEY

4.1. Introduction………………………………………………………………... 42.

4.2. Air Flow Simulation Analysis………………………………………………43.

4.2.1. Air flow director analysis……………………………………………………44.

4.2.1.1.Without air flow director analysis…………………………………………..44.

4.2.1.2.With air flow director analysis……………………………………………... 46.

4.2.2. Nozzle Design analysis…………………………………………………….. 49.

4.2.2.1.Nozzle Design Pattern 01 analysis…………………………………………..49.

4.2.2.2.Nozzle Design Pattern 02 analysis…………………………………………..51.

vii

4.2.3. The Turbine’s blades Design analysis………………………………………52.

4.2.3.1.The turbine’s blade design pattern I and II………………………………….53.

4.2.4. Overall Simulation analysis………………………………………………….54.

4.3. Solar Chimney Parts Design and Modification……………………………. 57.

4.3.1. Power Generator design ……………………………………………………..57.

4.3.1.1.Turbine Shaft………………………………………………………………...58.

4.3.1.2.Turbine’s Blades ……………………………………………………………59.

4.4.1. Power Generator……………………………………………………………..61.

4.4.2. Gear System………………………………………………………………….61.

4.4.3. Water Tube………………………………………………………………….63.

4.4.4. Collector Skirt……………………………………………………………… 63.

4.5. Conceptual Solar Chimney Design………………………………………… 64.

4.5.1. Conceptual Design 1……………………………………………………….. 64.

4.5.2. Conceptual Design 2……………………………………………………….. 66.

4.6. Assembly Process………………………………………………………….. 67.

4.7. Summary…………………………………………………………………… 70.

CHAPTER 5 RESULT AND DISCUSSION

5.1. Introduction………………………………………………………………… 71.

5.2. Air Temperature Variation Analysis in Solar Chimney…………………….72.

5.3. Water Tube Analysis in Solar Chimney…………………………………….75.

5.4. Solar Collector Skirt analysis………………………………………………..78.

5.5. Discussion …………………………………………………………………..79.

5.6. Conclusion ………………………………………………………………….82.

viii

CHAPTER 6 CONCLUSION AND RECOMMENDATION

6.1. Conclusion…………………………………………………………………. 83.

6.2. Recommendations …………………………………………………………. 85.

REFERENCE…………………………………………………………………….. 88.

APPENDIX.............................................................................................................. 90.

ix

LIST OF TABLES

Table 2.1: Pressure difference and wind velocity versus power output (P2)………. 17.

Table 2.2: Annual power output comparison, which illustration the influence

of the including a better quality glass for the collector roof……. ……... 22.

Table 2.3: Annual power output comparison for solar chimney power plant

employing various ground types……………………………………….. 29.

Table 4.1: Material comparison for the turbine shaft ……………………………... 59.

Table 4.2: Material comparison for the turbine’s wing……………………………. 60.

Table 4.3: Material comparison of power generator ………………………………. 61.

x

LIST OF FIGURES

Figure 2.1: Sea Breeze……………………………………………………………... 5.

Figure 2.2: Solar chimney operation concepts…………………………………….. 7.

Figure 2.3: Principle of heat storage underneath the roof using water filled

black tubes…………………………………………………………….. 8.

Figure 2.4: Solar chimney’s structure……………………………………………… 9.

Figure 2.5: Influence of the tower height on the average temperature in

the tower……………………………………………………………….. 11.

Figure 2.6: Standard atmospheric and isentropic specific volumes………………... 12.

Figure 2.7: Influence of the tower radius on the mass flow……………………….. 14.

Figure 2.8: Influence of the tower radius on the velocity of the tower

symmetry axis………………………………………………………….. 14.

Figure 2.9: Solar chimney turbine layouts…………………………………………. 19.

Figure 2.10: Schematic drawing of horizontal-to-vertical transition section

(a) without and (b) with a centerpiece to redirect the flow…………… 20.

Figure 2.11: Effect of the inclusion of a better quality glass for the

collector roof…………………………………………………………. 21.

Figure 2.12: Influence of collector material on the ground temperature…………... 23.

Figure 2.13: Influence of collector material to the flow velocity in the tower…….. 23.

Figure 2.14: Influence of collector radius on the average temperature in the

solar collector…………………………………………………………. 24.

xi

Figure 2.15: Influence of the collector height on the development of the

mass flow……………………………………………………………... 25.

Figure 2.16: Influence of the collector height on the average temperature

in the tower.…………………………………………………………... 26.

Figure 2.17: Comparison between the original and new convective heat

transfer coefficients…………………………………………………... 30.

Figure 2.18: Thermal networks for a solar chimney collector…………………….. 32.

Figure 3.1: Conceptual drawing of the new method proposed……………………. 37.

Figure 3.2: Three main parts of chimney for ease of modification……………….. 40.

Figure 4.1: Air flow velocity analysis without the flow director …………………. 45.

Figure 4.2: Air flow pressure analysis without the flow director…………………. 46.

Figure 4.3: Air flow velocity analysis with air flow director……………………… 47.

Figure 4.4: Air flow pressure analysis with air flow director……………………… 48.

Figure 4.5: Air flow velocity analysis with nozzle design pattern 01……………... 50

Figure 4.6: Air flow pressure analysis with nozzle design pattern 01…………….. 50.

Figure 4.7: Air flow velocity analysis with nozzle design pattern 02……………... 51.

Figure 4.8: Air flow pressure analysis with nozzle design pattern 02…………….. 52.

Figure 4.9: Pressure analysis of turbine’s blade design pattern 1…………………. 53.

Figure 4.10: Pressure analysis of turbine’s blade design pattern II……………….. 54.

Figure 4.11: Velocity analysis at Part I and Part II …………………………........... 55.

Figure 4.12: Velocity analysis whole systems…………………………………….. 56.

Figure 4.13: Second generator parts design in conceptual design 1……………….. 65.

Figure 4.14: Overall conceptual design 1…………………………………………...66.

xii

Figure 4.15: Second generator part design in conceptual design 2………………… 67.

Figure 4.16: Flow of solar chimney structure assembly process………………….. 69.

Figure 5.1: Temperature variant across solar collector ……………………………. 73.

Figure 5.2 Temperature on the solar collector near the perimeter…………………. 74.

Figure 5.3: Temperature on the solar collector near the center……………………. 75.

Figure 5.4 Temperature under solar collector (i) with skirt, (ii) without skirt…….. 78.

xiii

NOMECULATURE

Latin

𝑝 Pressure

𝑉 Wind velocity

𝑣 Volume

𝜌 Density [kgm-3

]

𝑒 Maximal net work output [J/kg]

ŋ Efficiency

𝐻 Stagnation enthalpy

𝑕 Convection heat transfer coefficient [W/m2K]

𝑓 Friction factor

𝑅𝑒 Reynolds number

𝑃𝑟 Prandtl number

𝑘 Thermal conductivity [W/m K]

𝑑 Diameter

𝜇 Dynamic viscosity [kg/m s]

𝑔 Gravitational acceleration

𝑐 Specific heat coefficient

𝑇 Temperature

𝑁 Number of gear tooth

𝑤 Gear speed

xiv

𝑅 Gear ratio

𝑄 Heat energy

𝑐 Specific heat capacity

𝜃 Temperature gradient

Prefix

∆ Change in value

Subscript

𝐻𝑐 Chimney height

𝑎 Atmosphere

𝑐𝑜𝑙𝑙 Collector

𝑡𝑜𝑡 Total

𝑡𝑡 Circumferential component

𝑡 Total (stagnation) or turbine

𝐿𝑜𝑠𝑠 Loss

𝑟𝑕 Collector roof to air under collector roof

𝑕 Air under collector roof or hydraulic

𝑟𝑎 Collector roof to ambient air

𝑚 Mean

𝑝 Pressure

𝑀 Motor

𝐷 Driven

1

CHAPTER 1

INTRODUCTION TO SOLAR CHIMNEY

1.1. Introduction

Solar chimney generator is a hybrid system of solar and wind energy,

which are using convection of air heated by passive solar energy generate electric

energy. It is also referred as the thermal chimney.

By considering all forms of energies options available, renewable energy

has become more preferable to the society compare with conventional energy

resources such as petroleum, coal and natural gas. The solar chimney is an

alternative source because it is cheap and green energy, which is affordable for

developing country and preferable for advanced country that demand for

unpolluted and stable price energy. This renewable energy fulfills the demand of

the society to achieve a better, healthier and safer life style.

Solar chimney is getting the attention due to the new renewable power

generator that meets the current demand. Researchers are interested in this sector

2

and many researches were conducted, but the efficiency of the renewable energies

is still not running at its efficient state.

The solar chimney was first originated by German author, Hanns Günther

in 1931. In Manzanares, (Spain), a small scale working model of solar chimney

was successfully built by Prof. Dr. Ing. Jörg Schlaich, Bergerman and Partner. In

1982, the chimney had a diameter of 10 meters and height of 195 meters, with a

collection area (greenhouse) of 46,000m2 (about 11 acres) obtaining a maximum

power output of about 50kW. The solar chimney function around 8 years before it

was destroyed in a thunderstorm. Before the incident happened, the optimization

data was collected and was lincensed to EnviroMission and SolarMission

Technologies Inc. USA.

Solar chimney power plant consists of transparent glass canopy roof raised

a certain height from the ground and surrounding the black chimney circular

tower. Inside the chimney tower lays one or more turbo-generators at its center

base. Black color heat absorber is laid and the water tubes are place between the

heat absorber to allow night tie power generation.

Current prototype has a chimney tower of 3.6 meter height. Inside the

chimney tower lie two generators, a nozzle is installed for the second generator to

function using water mill concept. The chimney tower is built on circular solar

3

collector, which is connected by a chimney support. The solar collector is 4.2

meter in diameter. The solar collector is raise 15 millimeter from the ground and

incline till 50 millimeter. Below the collector lie the black heat absorber tiles and

water tubes. Water tubes absorb heat during the day time and release it at night

time for plant operation.

1.2. Objective of the project

Objectives of this project are to made modification on the existing solar

chimney. To do so, the chimney will be reassembled. Some parts of the current

chimney will be improved such as the main generator and chimney tower. For

modifications part, the processes include reducing the air leakage from the

chimney, to improve power output by studying the generator and implementation

of water tube. Then simulation will be applied to the modified chimney. Lastly

testing will be run to observe the overall performances. All those are to increase

the solar chimney efficiencies.

4

CHAPTER 2

LITERATURE REVIEW

2.1. Introduction

Since the year electricity was discovered, the demand of electricity has

been increasing. Societies now no longer just demand for simple electricity, they

also demand for environment friendly energy or so called the green energy. Green

energies that that are common found are the hydroelectricity, geothermal, wind

power generator and photovoltaic cell. Another green energy that researcher are

interested recently is the solar chimney power generator. This chapter contains the

literature review of some researches done previously by various researchers

regarding solar chimney power generator. In this chapter also, the working

concept, the solar chimney structure, and environment factors to be consider will

be discuss.

5

2.2. The Working Concept of Solar Chimney

The working principle of the solar chimney is actually originated from the

natural occurrence of hot air rises. An easy illustration of this concept is by

considering the sea breeze, which is shown in Figure 2.1.

Figure 2.1: Sea Breeze

The sun heated up both land and sea. Land heats up faster than sea to

higher temperature, causing the air on the surface of the land hotter than air on the

surface of the sea. The hot air on the surface of land raises and creates a low

pressure condition on the land surface. Air on sea surface, which experience

higher pressure, will move toward the lower pressure land surface replacing the

raised hot air. While moving from sea to land surface, the air is being heated by

the hot land temperature and hence the air will rise again, creating an infinite

6

cycle. This cycle result a steady wind moving from sea to land and that is

basically the sea breeze theory.

In the solar chimney, the heat absorber will heated up faster than it‟s

surrounding; causing the air on the surface of the heat absorber to raise and flow

toward the chimney tower. At the same time, the pressure on the heat absorber

surface will drop to a point which lowers than the surrounding pressure. Hence

cool air from the surrounding which has higher pressure will flow into the solar

collector, due to air flow from high pressure to low pressure area. While the cool

air flow in solar collector, it will slowly heated up by the heat from the heat

absorber. Cool air temperature rises across the heat absorber and finally flows out

through the chimney tower. The air flow through the chimney tower will be

harvest by the generator turbines and generates electricity. This concept is

illustrated in Figure 2.2.

During the day, heat absorber and water tube were heated up together.

When come to night time, the heat collected in the water will be released to

continue heating up the surface air as to replace the heat absorber. Heat release

from the water tube heated up the surface air to a higher temperature causing them

to rise. This creates a pressure difference between the air inside the solar collector

and the surrounding, hence wind flow created between these areas. Cool air

moving into the solar collector is slowly heated up by the heat released from the