Design, construction and testing of a two axes

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When utilizing the solar energy using refraction, then the sun rays are ..... 3.5). Figure 3.4: Parabola with optimum rim angle of 45 ̊. Figure 3.5: Dish ..... Because we started the parabola at x = 0.1 m, then a half of a circle of radius = 0.1 m .... from the steel box (75 cm is longer than the dish radius and therefore the dish can.
Design, construction and testing of a two axes tracking parabolic solar collector with economical consideration

Saif Bin Khalfan Bin Saif AL-Jahwari

A Project Report submitted in partial fulfillment of the requirements for the Degree of Master of Science in Mechanical Engineering

Department of Mechanical and Industrial Engineering College of Engineering Sultan Qaboos University Sultanate of Oman

December, 2011 ©

Project of Saif Bin Khalfan Bin Saif AL-Jahwari

(I.D. #) 24259/07

Title of Project: Design, construction and testing of a two axes tracking parabolic solar collector with economical consideration.

Thesis Committee: 1. Supervisor:

Dr. Saif A. AL-Hiddabi

Title:

Associate Professor

Department:

Mechanical and Industrial Engineering

Institution:

Sultan Qaboos University.

Signature:

2. Co-Supervisor:

Date:

Dr. Tasneem Pervez

Title:

Associate Professor

Department:

Mechanical and Industrial Engineering

Institution:

Sultan Qaboos University.

Signature:

3. Co-Supervisor:

Date:

Dr. Mahmoud Tahat

Title:

Associate Professor

Department:

Mechanical and Industrial Engineering

Institution:

Sultan Qaboos University.

Signature:

Date:

Thesis Examining Committee: 1. Chair:

Dr. Baba El-Yakubu Jibril

Title:

Associate Professor

Department:

Petroleum and Chemical

Institution:

Sultan Qaboos University

Signature:

2. Supervisor:

Date:

Dr. Saif A. AL-Hiddabi

Title:

Associate Professor

Department:

Mechanical and Industrial Engineering

Institution:

Sultan Qaboos University.

Signature:

Date:

3. Member:

Dr. Yousef Zurigat

Title:

Associate Professor

Department:

Mechanical and Industrial

Institution:

Sultan Qaboos University

Signature:

4. External Examiner:

Date:

Dr. Mohammed Zahir Al-Abri

Title:

Assistant Professor

Department:

Petroleum and Chemical

Institution:

Sultan Qaboos University

Signature:

Date:

ACKNOWLEDGEMENT I thank Allah for blessing of completion of this project. I would like to extend my appreciation to the Sultan Qaboos University for the support received during my study. Special thanks and appreciation is extended to Dr. Saif Al-Hiddabi for his significant and continuous support as well as his help in outlining and directing this work. Special thanks are also extended to Dr. Tasneem Pervez and Dr. Mahmoud Tahat. I would like to express my deep thanks to my family for the significant support which had made this project successful.

IV

ABSTRACT Solar parabolic dish of 1 m diameter has been designed with the optimum rim angle of 45 ̊ for cavity receiver. The dish was designed for optical efficiency of 84%, concentrated solar energy of 424 W and concentration ratio of 21. The dish was simulated using ANSYS software to confirm safe structure for the dish. Both weight and wind loads were considered in the simulation. Auto-Cad software was used to simulate the geometry of the dish as well as the tracking mechanism. Finite Element Method was used for the stress analysis of both the dish and the tracking mechanism using four computer processors to achieve the numerical analysis. The tracking mechanism with the dish was simulated in ABAQUS software to confirm safe structure under dynamic loads. The safety factor is calculated and found to be 3.87. The dish was fabricated with new fabrication process and new tracking mechanism was constructed. New control circuit was designed and built using four Light Dependent Resistors (90 ̊ apart on the dish) as input components, NPN transistor as signal identifier and relays for inverting motors’ rotation. The geometry and performance of the dish were tested through measuring the actual focal length which was found with 4 mm error (0.7%). The operation of the tracking system with the dish was tested and the results are satisfactory. Economical analysis was performed on the dish and it was estimated that solar heating is cheaper than electrical heating by 43 OMR per year (considering heating 200 liters of water daily from 28 ̊ C to 42 ̊ C).

V

‫ﺍﻟﺧﻼﺻﺔ‬ ‫ﺗﻡ ﺗﺻﻣﻳﻡ ﻣ َُﺟﻣﱢﻊْ ﻁﺎﻗﺔ ﺷﻣﺳﻲ ﺑﻳﺿﺎﻭﻱﱡ ﺍﻟﺷﻛﻝ ﻭ ﺫﻟﻙ ﻋﻥ ﻁﺭﻳﻕ ﺗﺻﻣﻳﻡ ﻣﻧﺣﻧﻰ ﻫﻧﺩﺳﻲ‬ ‫ﺑﻳﺿﺎﻭﻱ ﺛﻧﺎﺋﻲ ﺍﻷﺑﻌﺎﺩ ﺛﻡ ﺍﻟﻘﻳﺎﻡ ﺑﺩﻭﺭﺍﻥ ﻗﺩﺭﻩ ‪ 360‬ﺩﺭﺟﺔ ﻟﻠﻣﻧﺣﻧﻰ ﻭ ﺑﺫﻟﻙ ﻳﺗﻛﻭﻥ ﺍﻟﺑﻌﺩ ﺍﻟﺛﺎﻟﺙ‬ ‫ﺻﻣِﻡ ﺍﻟﻣ َُﺟﻣﱢﻊْ ﺑﻘﻁﺭ ‪ 1‬ﻣﺗﺭ ﻣﻊ ﺯﺍﻭﻳﺔ ﻗﻁﻊ ﻣﺛﺎﻟﻳﺔ ﻟﻠﻣ َُﺟﻣﱢﻊْ ﻭ ﻫﻲ ‪ 45‬ﺩﺭﺟﺔ ﻭ ﺫﻟﻙ‬ ‫ﻟﻠﻣ َُﺟﻣﱢﻊْ ‪ُ .‬‬ ‫ﺑﺈﻋﺗﺑﺎﺭ ُﻣﺳْ َﺗ ْﻘ ِﺑﻝ ﺗﺟﻭﻳﻔﻲ ﻟﻁﺎﻗﺔ ﺍﻟﺷﻣﺱ ﺍﻟﻣﻧﻌﻛﺳﺔ ﻣﻥ ﺍﻟﻣ َُﺟﻣﱢﻊْ ‪ .‬ﻭ ﻗﺩ ﺻﻣﻣﺕ ﻟﻠﻣ َُﺟﻣﱢﻊْ ﺁﻟﻳﺔ ﺗﺗﺑﻊ‬ ‫ﻟﻠﺷﻣﺱ ﻓﻲ ﻣﺣﻭﺭﻱ ﺣﺭﻛﺗﻬﺎ ﺍﻷﻓﻘﻳﺔ ﻭ ﺍﻟﻌﻣﻭﺩﻳﺔ‪ .‬ﻭﻗﺩ ﺗﻡ ﺗﺻﻣﻳﻡ ﺍﻟﻣ َُﺟﻣﱢﻊْ ﻟﺗﺣﻘﻳﻕ ﻛﻔﺎءﺓ ﺑﺻﺭﻳﺔ‬ ‫ﻗﺩﺭﻫﺎ ‪ ،٪ 84‬ﻭﺇﻧﺗﺎﺝ ﻁﺎﻗﺔ ﺷﻣﺳﻳﺔ ﺣﺭﺍﺭﻳﺔ ﻣﺭﻛﺯﺓ ﻗﺩﺭﻫﺎ ‪ 424‬ﻭﺍﻁ ﻣﻊ ﻣﻌﺎﻣﻝ ﺗﺭﻛﻳﺯ ﻗﺩﺭﻩ‬ ‫‪ .21‬ﻭ ﺗﻡ ﺍﺳﺗﺧﺩﺍﻡ ﺍﻟﺑﺭﻧﺎﻣﺞ ﺍﻟﺣﺎﺳﻭﺑﻲ ‪ ANSYS‬ﻓﻲ ﺍﻟﺗﺻﻣﻳﻡ ﻭ ﻭ ﺫﻟﻙ ﺑﻣﺣﺎﻛﺎﺓ ﺍﻟﻣ َُﺟﻣﱢﻊْ ﻟﻠﺗﺄﻛﺩ‬ ‫ﻣﻥ ﺃﻥ ﺑﻧﻳﺗﻪ ﺁﻣﻧﺔ‪ .‬ﻭﺍﻋﺗﺑﺭ ﻛﻝ ﻣﻥ‪ :‬ﺍﻟﻭﺯﻥ ﻭﺍﻟﺭﻳﺎﺡ ﻓﻲ ﺍﻟﻣﺣﺎﻛﺎﺓ‪ .‬ﻛﻣﺎ ﺍﺳﺗﺧﺩﺍﻡ ﺍﻟﺑﺭﻧﺎﻣﺞ‬ ‫ﺍﻟﺣﺎﺳﻭﺑﻲ ‪ Auto-Cad‬ﻟﻣﺣﺎﻛﺎﺓ ﺷﻛﻝ ﻭ ﺃﺑﻌﺎﺩ ﺍﻟﻣ َُﺟﻣﱢﻊْ ﻭ ﺁﻟﻳﺔ ﺗﺗﺑﻊ ﺍﻟﺷﻣﺱ‪ .‬ﻭﻗﺩ ﺍﺳﺗﺧﺩﻡ ﺃﺳﻠﻭﺏ‬ ‫ﺍﻟﻌﻧﺻﺭ ﺍﻟﻣﺣﺩﺩ )‪ (Finite Element Method‬ﻟﺗﺣﻠﻳﻝ ﺍﻹﺟﻬﺎﺩ )‪ (stress‬ﻋﻠﻰ ﺍﻟﻣ َُﺟﻣﱢﻊْ ‪،‬‬ ‫ﻭﺁﻟﻳﺔ ﺗﺗﺑﻊ ﺍﻟﺷﻣﺱ ﺑﺎﺳﺗﺧﺩﺍﻡ ﺃﺭﺑﻊ ﻣﻌﺎﻟﺟﺎﺕ ﺣﺎﺳﻭﺑﻳﺔ ﻹﻧﺟﺎﺯ ﺍﻟﺗﺣﻠﻳﻝ ﺍﻟﻌﺩﺩﻱ‪ .‬ﻛﻣﺎ ﺍُﺳﺗﺧﺩﻡ‬ ‫ﺍﻟﺑﺭﻧﺎﻣﺞ ﺍﻟﺣﺎﺳﻭﺑﻲ ‪ ABAQUS‬ﻟﺗﺄﻛﻳﺩ ﺑﻧﻳﺔ ﺁﻣﻧﺔ ﻟﻠﻣ َُﺟﻣﱢﻊْ ﻭ ﺁﻟﻳﺔ ﺗﺗﺑﻊ ﺍﻟﺷﻣﺱ ﺗﺣﺕ ﺃﺣﻣﺎﻝ‬ ‫ﺍﻟﺣﺭﻛﺔ ﺍﻟﺩﻳﻧﺎﻣﻳﻛﻳﺔ‪ .‬ﻭﺗﻡ ﺣﺳﺎﺏ ﻋﺎﻣﻝ ﺍﻷﻣﺎﻥ ﻭ ﻭُ ﺟﺩ ﺃﻧﻪ ‪ .3.87‬ﺗﻡ ﺗﺻﻧﻳﻊ ﺍﻟﻣ َُﺟﻣﱢﻊْ ﺑﻁﺭﻳﻘﺔ‬ ‫ﺗﺻﻧﻳﻊ ﺟﺩﻳﺩﺓ ﻣﻊ ﻁﺭﻳﻘﺔ ﺟﺩﻳﺩﺓ ﻟﺗﺗﺑﻊ ﺍﻟﺷﻣﺱ‪ .‬ﻭﻗﺩ ﺗﻡ ﺗﺻﻣﻳﻡ ﻭ ﺗﺻﻧﻳﻊ ﺩﺍﺋﺭﺓ ﺗﺣﻛﻡ ﺟﺩﻳﺩﺓ‬ ‫ﺑﺎﺳﺗﺧﺩﺍﻡ‪ :‬ﺃﺭﺑﻊ ﻣﻘﺎﻭﻣﺎﺕ ﻛﻬﺭﺑﺎﺋﻳﺔ ﺣﺳﺎﺳﺔ ﻟﺿﻭء ﺍﻟﺷﻣﺱ )ﻣﺛﺑﺗﺔ ﻋﻠﻰ ﺳﻁﺢ ﺍﻟﻣ َُﺟﻣﱢﻊْ ﻋﻠﻰ ﺑﻌﺩ‬ ‫‪ 90‬ﺩﺭﺟﺔ ﻣﻥ ﺑﻌﺿﻬﺎ ﺍﻟﺑﻌﺽ( ﻟﺗﻛﻭﻥ ﻋﻧﺎﺻﺭ ﺍﻹﺩﺧﺎﻝ ﻟﻠﺩﺍﺋﺭﺓ ‪ ،‬ﻭ ﺑﻭﺍﺑﺔ ﻛﻬﺭﺑﺎﺋﻳﺔ‬ ‫)ﺍﻟﺗﺭﺍﻧﺯﺳﺗﻭﺭ ‪ (NPN‬ﻟﻳﺗﻌﺭﻑ ﻋﻠﻰ ﺇﺷﺎﺭﺓ ﺍﻹﺩﺧﺎﻝ‪ ،‬ﻭﻗﻭﺍﻁﻊ ﻛﻬﺭﺑﺎﺋﻳﺔ ﻣﻐﻧﺎﻁﻳﺳﻳﺔ )‪(Relays‬‬ ‫ﻟﻌﻛﺱ ﺩﻭﺭﺍﻥ ﺍﻟﻣﺣﺭﻛﻳﻥ ﺍﻟﺫﻳﻥ ﻳﺣﺭﻛﺎﻥ ﺍﻟﻣ َُﺟﻣﱢﻊْ ‪ .‬ﺗﻡ ﺍﺧﺗﺑﺎﺭ ﺃﺩﺍء ﺍﻟﻣ َُﺟﻣﱢﻊْ ﻣﻥ ﺧﻼﻝ ﻗﻳﺎﺱ ﺍﻟﺑﻌﺩ‬ ‫ﺍﻟﻔﻌﻠﻲ ﻟﻣﻛﺎﻥ ﺗﺟﻣﻊ ﺍﻟﻁﺎﻗﺔ ﺍﻟﺷﻣﺳﻳﺔ ﺍﻟﻣﺭﻛﺯﺓ ﻭ ﻭُ ﺟﺩ ﺃﻥ ﻣﻘﺩﺍﺭ ﺍﻟﺧﻁﺄ ﺍﻟﺗﺻﻧﻳﻌﻲ ﻫﻭ ‪ 4‬ﻣﻠﻡ‬ ‫)‪.(٪ 0.7‬ﻭ ﺗﻡ ﺍﺧﺗﺑﺎﺭ ﺗﺷﻐﻳﻝ ﻧﻅﺎﻡ ﺍﻟﺗﺗﺑﻊ ﻋﻠﻰ ﺍﻟﻣ َُﺟﻣﱢﻊْ ﻭﻛﺎﻧﺕ ﺍﻟﻧﺗﺎﺋﺞ ﻣﺭﺿﻳﺔ‪ .‬ﻛﻣﺎ ﺗﻡ ﺑﺣﺙ‬ ‫ﺍﻟﺟﺩﻭﻯ ﺍﻹﻗﺗﺻﺎﺩﻳﺔ ﻟﻠﻣ َُﺟﻣﱢﻊْ ‪ ،‬ﻭ ﻛﺎﻧﺕ ﻧﺗﻳﺟﺔ ﻫﺫﺍ ﺍﻟﺑﺣﺙ ﺃﻧﻪ ﻳُﻘ ﱠﺩﺭ ﺃﻥ ﺍﻟﺗﺳﺧﻳﻥ ﺑﺎﻟﻁﺎﻗﺔ ﺍﻟﺷﻣﺳﻳﺔ‬ ‫ﺃﺭﺧﺹ ﻣﻥ ﺍﻟﺗﺳﺧﻳﻥ ﺍﻟﻛﻬﺭﺑﺎﺋﻲ ﺑﻣﻘﺩﺍﺭ ‪ 43‬﷼ ﻋﻣﺎﻧﻲ ﺳﻧﻭﻳﺎ )ﺑﺈﻋﺗﺑﺎﺭ ﺗﺳﺧﻳﻥ ‪ 200‬ﻟﺗﺭ ﻣﻥ‬ ‫ﺍﻟﻣﻳﺎﻩ ﻳﻭﻣﻳﺎ ﻣﻥ ‪ 28‬ﺇﻟﻰ ‪ 42‬ﺩﺭﺟﺔ ﺳﻳﻠﻳﺯﻳﺔ(‪.‬‬

‫‪VI‬‬

Table of Contents

Acknowledgment

IV

Abstract in English

V

Abstract in Arabic

VI

List of Figures

X

List of Tables

XIII

Chapter 1: Introduction

1

1.1

Categorization for the methods of utilizing solar energy

1

1.2

Photovoltaic

2

1.3

Refraction

3

1.4

Flat plate collectors

4

1.5

Vacuum tube and heat pipe collector

5

1.6

Central system (Solar tower)

6

1.7

Solar troughs

7

1.8

Solar dish

7

1.9

Combination of solar technologies

8

1.10

Objectives of the project

8

Chapter 2: Progress in Solar Dish Technologies, Conceptual Design and Design Philosophy

9

2.1

Overview on recent solar technologies

9

2.2

Early solar dishes

9

2.3

Recent solar dishes

11

2.4

Conceptual design of the dish

12

2.4.1

Dish frame

12

2.4.2

Tracking method

13

2.4.3

Cost and dish optics

15

2.4.4

Design philosophy

16

VII

CHAPTER 3: Parabolic Dish Geometry Design and Dish Capability Calculations

17

3.1

Parabolic dish geometry

17

3.1.1

Receivers and rim angle optimization

18

3.1.2

Defining the dimensions of the dish

19

3.2

Dish performance estimation

21

3.2.1

Optical efficiency

21

3.2.2

Calculation of concentrated solar energy at the focus (Qc)

22

3.2.3

Calculation of concentration ratio (CR)

23

CHAPTER 4: Dish Design, Simulation and Fabrication

25

4.1

Dish design

25

4.2

Dish fabrication

32

4.2.1

Preparation of fabrication board

32

4.2.2

Members fabrication for the matrix frame

34

4.2.3

Joining the members to form the matrix frame

36

4.2.4

Fixing the wood and aluminum sheets on the matrix dish

37

Chapter 5: Design and Fabrication of Tracking Mechanism and Dish Base

43

5.1

Design of the tracking mechanism and dish base

43

5.2

Fabrication of tracking mechanism and dish base

47

5.2.1

Fabrication of the altitude box

47

5.2.2

Installation of the driver for tracking the altitude direction

49

5.2.3

Rotation axis for azimuth direction

49

5.2.4

Dish base

50

5.2.5

Installation of the driver for tracking in azimuth direction

50

5.2.6

Selection of the driving motors

51

5.2.7

Features of the tracking mechanism

52

CHAPTER 6: Control System Design and Setup

56

6.1

The conceptual design of the control circuit

56

6.2

Selection for the components of the control circuit and system setup

56

6.2.1

Selection of the component for input signal

56

6.2.2

Selection of other functional components

57

VIII

6.2.3

Connection between input circuit and functional circuit

57

6.2.4

Connecting all of the components together

58

6.3

Control circuit specifications and verification

62

CHAPTER 7: Testing of the Tracking System and the Dish

65

7.1

Verifying dish performance

65

7.2

Testing the dish with tracking system

65

Chapter 8: Economical Analysis of the Dish System

68

8.1

Manufacturing and capital costs of the dish

68

8.1.1

Manufacturing cost

68

8.1.2

Capital cost

70

8.2

Operational cost of the dish

70

8.3

Maintenance cost of the dish

70

8.4

The dish as a heater

71

8.5

Costs of electrical heater

76

8.5.1

Capital cost

76

8.5.2

Operational cost

76

8.6

Economical comparison between solar heater and electrical heater

77

Chapter 9: Conclusions and Recommendations

80

References

81

Appendix 5.1: Angular Speed of the Sun in Azimuth Direction

90

Appendix 8.1: Global radiation and sunshine duration

102

Appendix 8.2: Average temperatures in Muscat (Seeb)

103

IX

List of Figures

Figure Title

Page

1.1

Categorization for the methods of utilizing solar energy

2

1.2

Solar cell

3

1.3

Schematic for refraction of sun rays

3

1.4

Glazed flat plate collector

4

1.5

Unglazed flat plate collector

5

1.6

Vacuum tube and heat pipe collector

6

1.7

Solar tower

6

1.8

Solar troughs

7

1.9

Plant of solar dishes

7

2.1

Schematic for dish/Stirling system

9

2.2

Vanguard I (Parabolic dish with heat engine in 1984)

10

2.3

Solar plant Number 1

11

2.4

ANU 500 square meter dish

11

2.5

Low cost dish

12

2.6

Solid frame dish

13

2.7

Shadow tracking method

14

2.8

Tracking by sensing solar intensity

15

3.1

Parabola geometry

18

3.2

Cavity Receiver

18

3.3

Rim angle optimization

19

3.4

Parabola with optimum rim angle of 45 ̊

20

3.5

Dish dimensions

20

4.1

Dish dimensions (vertical)

25

X

Figure Title

Page

4.2

Three dimensional drawing of the matrix frame.

26

4.3

The overall system mesh

27

4.4

Selected area for the matrix mesh

27

4.5

Von Mises stress for the static load

28

4.6

CFX model for the wind analysis

29

4.7

Fluid domain mesh (421985 tetrahedral elements)

29

4.8

Matrix frame mesh surrounded with fluid elements

30

4.9

Velocity profile around the focus holder

30

4.10

Pressure distribution on the matrix frame resulted from wind load

31

4.11

Effective stress for combined wind and weight loads

31

4.12

Positive half of the parabola

33

4.13

Fabrication board

33

4.14

Shaping the parabola piece

34

4.15

The construction member

35

4.16

The fabrication error

36

4.17

Joining drawing

36

4.18

The matrix dish

37

4.19

Pressing the wood pieces

39

4.20

The unit of inverted members

39

4.21

The dish after gluing the wooden pieces

40

4. 22

The dish after completing gluing of aluminum pieces

40

4.23

Member for the holder of the receiver

41

4.24

The dish with the holder of the receiver

42

5.1

Representative geometry and boundary conditions of the mechanism frame

XI

44

Figure Title

Page

5.2

Finite element mesh of the mechanism frame

45

5.3

Effective stress of the holder (Pa)

46

5.4

Effective stress of the base (Pa)

46

5.5

The dish with the tracking mechanism (jack motor not installed)

48

5.6

Normal motor is replaced by Jack motor for tracking in altitude direction

53

5.7

Dish foundation and azimuth axis

54

5.8

Complete tracking mechanism

55

6.1

6.2

Control circuit diagram (see table 6.1 for the symbols of the components) Schematic diagram for the parameters of the specification for NPN Transistor

59

63

6.3

Control Circuit picture

64

7.1

Dual Power Source

67

7.2

LDR's casing

67

XII

List of Tables

Table Title 1.1

Page

Solar collectors with their characteristics and temperatures limitations

8

4.1

Parabola points

32

6.1

Symbols for the components of the control circuit

60

6.2

Comparison between component's limits and actual conditions in the circuit

63

7.1

Actual voltages, currents and power of the dish system while testing

66

8.1

Costs for manufacturing one dish with the two axes tracking system

69

8.2

8.3

8.4

8.5

8.6

Costs for the maintenance of one dish with the two axes tracking system differences in the costs due to changing the reflective material to glass mirror economical comparison between the solar heater and the electrical heaters The expenses for the first two years for both the solar heater and the electrical heaters The expenses for the first ten years for both the solar heater and the electrical heaters

XIII

71

75

77

77

78

CHAPTER 1 Introduction Due to the increasing demand for energy (especially electricity) and the associated environmental problems of fossil fuel, solar energy is receiving more attention. Because it is free, clean and renewable (Wu et al., 2010). Oman is among the countries which receive the highest rate of solar energy and has the potential to utilize it effectively.

Sun energy is free, naturally brings heat and light to earth in a clean form and without any pollution. The sun delivers its energy continuously and therefore the solar energy is renewable. Because of the importance of solar energy, many researches have been conducted related to its application. As an example, researches were done on the following solar energy applications: • • • • • • • • • • 1.1

Steam generation. Desalination. Electricity generation. Drying crops. General drying. Heating of buildings. Solar cooling. Mobile homes. Chemical reactions. Destruction of hazardous wastes. Categorization for the methods of utilizing solar energy

There are many ways to utilize the sun energy. Figure 1.1 shows the classification of utilizing solar energy. This categorization is based on the form of solar energy. There are two forms for utilizing solar energy: light and heat. This is shown in Fig. 1.1 in the two main categories: photovoltaic (light) and thermal (heat). The thermal utilization can be divided in four categories based on the application. As shown in Fig. 1.1, the reflection is divided into two systems according to the way of collecting the heat. These two systems are the central and distributed systems.

-1-

Methods of Solar Energy Utilization Photovoltaic Cells

Refraction

Thermal

Flat Plate Collectors

Reflection

Central System (solar Tower)

Vacuum Tube Collectors

Distributed System Solar Trough Plant Solar Dish Plant

Figure 1.1: Categorization of the methods of utilizing solar energy

1.2

Photovoltaic cells

When sunlight hits a photovoltaic cell, electrons will flow causing electrical current as shown in Fig. 1.2. Unlike traditional photovoltaic cells, concentrated photovoltaic technology (CPV) uses optics such as lenses to concentrate a large amount of sunlight onto a small area of photovoltaic materials (P.J. Sonneveld et al., 2010). By using same area of photovoltaic material, CPV generates more electricity than traditional photovoltaic cells.

-2-

Figure 1.2: Solar cell

1.3

Refraction

When utilizing the solar energy using refraction, then the sun rays are refracted and focused at the focal point (Fig. 1.3). Therefore, the scattered energy will be collected at the focus in order to produce useful energy. Convex lens are used to refract the sun rays.

Figure 1.3: Schematic for refraction of sun rays.

-3-

1.4

Flat Plate collectors

The flat plate solar collectors are classified into two categories: glazed and unglazed collectors. The glazed flat plate collector (Fig. 1.4) is a metallic box with a glass or plastic cover (called glazing) on top and a dark-colored absorber plate on the bottom. The sides and bottom of the collector are usually insulated to minimize heat loss. Sunlight passes through the glazing and strikes the absorber plate, which heats up, changing solar energy into heat energy. The heat is transferred to liquid flowing through pipes attached to the absorber plate. On the other hand, the unglazed flat plate collector (Fig. 1.5) is normally built without glazing on the top. It consists of an absorbing plate which will be heated due to absorption of solar energy. The gained heat will be transferred to the fluid passing through the tubes which are attached to the plate.

Figure 1.4: Glazed flat plate collector

-4-

Figure 1.5: Unglazed flat plate collector

1.5

Vacuum tube and heat pipe collector

The vacuum tube solar collector (Fig. 1.6) consists of double layer glass tube and heat pipes in the core. There is a vacuum between the two layers of the tube and this is the reason for calling the collector a vacuum tube collector. This vacuum will prevent heat conduction and convection. As a result, heat loss from the collector will be minimized. The heat pipe will absorb solar heat and therefore the working fluid inside the pipe will heat up. Another fluid is passing around the tip of the pipe and therefore the heat will be transferred to this fluid. On the other hand, the fluid inside the tip will lose heat and condense and it will flow down to repeat the cycle.

-5-

Figure 1.6: Vacuum tube and heat pipe collector

1.6

Central system (Solar tower):

In a solar tower, many mirrors are reflecting and concentrating solar energy to the same receiver (Wu et al., 2010). Therefore, the incident solar energy will be collected and concentrated at the same receiver in order to get useful energy (Fig. 1.7).

Figure 1.7: Solar tower

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1.7

Solar troughs

The parabolic trough is reflecting the solar energy into a linear receiver (Fig. 1.8). The output energy from many distributed troughs is collected to increase the received power and get a useful energy. Collecting the energy from the troughs can be done by piping network which carries working fluid that transfers the heat.

Figure 1.8: Solar troughs

1.8

Solar dish:

The parabolic dish reflects sun rays to a focal point (Wu et al., 2010). Therefore concentrated solar energy is produced at this point. This energy is thermal and can be converted to electricity through Stirling engine as shown in Fig. 1.9.

Figure 1.9: Plant of solar dishes

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1.9

Combination of solar technologies

Technologies which are previously described can be combined to boost the collection of sun energy. For example, flat plat collectors can be combined with solar trough. Also, PV panels can be used to generate the required electricity for the motors of solar dishes plant. Table 1.1 shows comparison between solar collectors with their characteristics and temperatures limitations. Table 1.1: Solar collectors with their characteristics and temperatures limitations (Kalogirou, 2004) Collector Flat plate collector Vacuum tube collector Parabolic trough collector Parabolic dish collector Solar tower collector

Geometrical concentration ratio

Indicative temperature range (◦C)

Sun tracking

Absorber type

Stationary

Flat

1

30

-

80

Stationary

Flat

1

50

-

200

Tubular

15

-

60

-

300

Point

100

- 1000

100

-

500

Point

100

- 1500

150

- 2000

Single-axis tracking Two-axes tracking Two-axes tracking

45

Note: Geometrical concentration ratio is defined as the aperture area divided by the receiver/absorber area of the collector

1.10

Objectives of the project

The need for energy is increasing for both domestic (as electricity) and industrial usage. One of the main resources of energy is the fossil fuel but it is harming the environment. Because of these problems, the world is heading to utilization of solar energy using various systems as described previously. One of the attractive approaches is the solar dish system because of its high efficiency. This project aims to design, construct and test a solar dish with two axes tracking system with minimum cost. It is not necessary to get a perfect dish but cost effective and practical design is the goal for this work. The project will deliver the following: new fabrication process for the dish structure, new control circuit for the tracking system and new tracking mechanism.

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Chapter 2 Progress in Solar Dish Technologies and Conceptual Design In this chapter, the importance of solar dish compared to other solar technologies will be presented. Also, the literature on solar dish technology will be surveyed and the new technology of solar dishes will be presented. The low cost dish concept will be demonstrated. Moreover, the conceptual design of the dish will be discussed.

2.1

Overview on recent solar technologies

Dish/Stirling systems have been found to have a high potential to become one of the least expensive sources of renewable energy due to their high solar-to-electric conversion efficiency of 31.25% (Wu et al., 2010).

Figure 2.1: Schematic for dish/Stirling system

2.2

Early solar dishes

Goswami (1987) reported that Advanco Cooperation built 11 meter diameter solar dish with two axes tracking and Stirling heat engine in February 1984. The heat engine was operating at 800 ̊ C which converts heat to electricity with concentration ratio of 2100 and net efficiency of 30% (produced electricity/received sun heat at dish opening = 26.400 kW/88.001 kW). This system was called "Vanguard I" (Fig. 2.2) and was located at California. This system was commercially developed by

-9-

McDonnell Douglas Corporation and United Stirling of Sweden. The commercial unit consisted of 90 m2 dish and engine, each unit that could generate 25kW.

Figure 2.2: Vanguard I [Parabolic dish with heat engine (Goswami, 1987)]

Also, Goswami (1987) wrote about Solar Plant Number 1. Solar Plant Number 1 was dedicated in January 1985 with 700 dishes providing superheated steam at 400 ̊ C. The plant was located in California and could produce 5MW. Figure 2.3 shows Solar Plant Number 1.

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Figure 2.3: Solar Plant Number 1 (Goswami, 1987)

2.3

Recent solar dishes

The solar dish technology is continuously improved. Australian National University (ANU) demonstrated a 400 m2 dish (22.57 m in diameter) in 1994. Another, 500 m2 dish (25.23 m in diameter) with two axes tracking was built and tested in June, 2009 by ANU as shown in Fig. 2.4. This dish could reach a temperature of 1200 ̊ C at the focus (Lovegrove et al., 2010).

Figure 2.4: ANU 500 square meter dish (Lovegrove et al., 2010).

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In Jan. 2006, Palavras and Bakos reported about a low cost dish system. The dish was made from damaged satellite dish (2.85 m aperture diameter) but it was reformed carefully with Polymer mirror film (reflectivity: 0.85). The focus diameter was 0.18 m. This dish costs $106 and it reached a temperature of 432 ̊ C at noon (ambient temperature was 30 ̊ C). The dish is shown in Fig. 2.5.

Figure 2.5: Low cost dish (Palavras and Bakos, 2006)

2.4

Conceptual design of the dish

2.4.1 Dish frame There are two main types of dish frames: 1) Solid Frame. 2) Matrix Frame

Solid frame: Solid aluminum frame dish with 200mm diameter could produce 11.5 thousands multiples of usual sun energy (Daniel Feuermann et al, 2002). Solid frame is more practical for small size dishes (less than 0.5 m diameter aperture) because they can be easily casted and then grinded and polished to make perfect parabolic profile. Solid frames needs more construction material than matrix frame which leads to extra cost and weight. However, this difference is negligible in small dishes.

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Figure 2.6: Solid frame dish

Matrix frame: Matrix frame has the advantages of: 1) Less weight 2) Low cost 3) Less power to operate the tracking system because of light weight. Matrix frame is more practical for large size dishes like the one built by ANU (Fig. 2.4). In this respect a matrix frame is selected for the construction of the dish. One meter diameter is chosen in order to ease the transportation of the dish as well as the fabrication, installation and testing. 2.4.2

Tracking method

The dish needs to be equipped with a tracking system. This system will move the dish so that it will follow the sun. The parabolic profile of the dish will enable the dish to reflect sun lights to the focus for heat generation. There are mainly two methods for tracking the sun position: 1) Tracking by using astronomical calculations 2) Shadow tracking method. 3) Tracking by sensing solar intensity

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Tracking by using astronomical calculations There are calculations to determine the position of the sun at any given time or date (like the ones given in Appendix 5.1). Therefore by using these calculated data and by using sensors that can tell the angel of solar collector relative to the earth; a closed loop tracking system to track the sun path can be built. These sensors will act as a feedback signal that will tell whether the collector is normal to the sun or not. However, these calculated data of the sun position are not that much accurate and therefore there will be a misalignment error to sun position. Also there will be a much consumed power since the collector will not work to find the sun but it will work continuously following the path of the sun even there are clouds or any other distortion of the sun lights. Shadow tracking method In April 2007 at University of Kashan in I.R. Iran, the shadow method for two axes tracking system was tested and reported (Arbab et al., 2009). This method (Fig. 2.7) uses camera to capture the image of a fixed bar shadow. The shadow will change as sun moves and this change can be analyzed by the computer and then the computer sends signal to move the dish to be facing the sun.

Figure 2.7: Shadow tracking method (2007)

Tracking by sensing solar intensity The level of solar intensity differs as per the position of an object with respect to the sun. When the object is directly facing the sun, then it will receive the maximum

- 14 -

possible solar intensity. On the other hand if the sun is just rising in the morning and an observer is facing west, then the observer will receive minimum solar light intensity but if he looks to the east, he will receive the maximum intensity. Therefore, solar intensity has direct relation to the sun position and accordingly the sun can be tracked and followed by sensing the sun intensity. This method was used to build a two axes tracking system (Fig. 2.8) in Sultan Qaboos University in Oman (AL-Busaidi and AL-Siyabi, 2006). Tracking by sensing solar intensity is the selected method because: 1) It has a direct relation with the actual sun position and therefore the sun can be followed and tracked easily. 2) This method does not require camera. Therefore, the camera's cost will be saved.

Figure 2.8: Tracking by sensing solar intensity (AL-Busaidi and AL-Siyabi, 2006)

2.4.3

Cost and dish optics

It is not necessary to get a perfect optical efficiency ηo (reflectance, parabolic profile, …etc, see section 3.2.1) for the dish design but practical perfection “cost effective” is the key for a successful design (Palavras and Bakos, 2006). Therefore, the optical

- 15 -

efficiency is not a main focus in this project. The focus is on practicality and minimizing the cost.

2.4.4

Design Philosophy

With reference to the sections 2.5.1, 2.5.2 and 2.5.3, the design philosophy for the dish system will be to have a system that has: 1) A light structure. 2) Economical and cost effective design. 3) Reliable tracking system. 4) Safe structure.

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CHAPTER 3 Parabolic Dish Geometry and Energy Calculations In this chapter, the parabolic dish geometry will be explained. Also, the thermal energy produced by the dish will be estimated. Moreover, this chapter will touch on the optical efficiency and concentration ratios for the dish.

3.1

Parabolic Dish Geometry Design

The parabolic shape is widely used as the reflecting surface for concentrating solar collectors because it has the property that, for any line parallel to the axis of the parabola, the angle p between it and the normal to the surface is equal to the angle between the normal and a line to the focal point (Fig. 3.1). Since solar radiation arrives at the earth in essentially parallel rays and the angle of reflection equals the angle of incidence, all radiation parallel to the axis of the parabola will be reflected to a single point F, which is the focus and therefore, the scattered solar energy will be concentrated at one focal point and this concentrated energy can be utilized in useful applications like steam generation. A parabolic dish (paraboloid) is formed by rotating the parabola about its axis. A parabola (Fig. 3.1) is the locus of a point that moves so that its distances from a fixed line (directrix) and a fixed point (the focus) are equal. The line perpendicular to the directrix and passing through the focus F is called the axis of the parabola. The parabola intersects its axis at a point V called the vertex, which is exactly midway between the focus F and the directrix. If the origin is taken at the vertex V and the xaxis along the axis of the parabola, the equation of the parabola is

y 2 = 4 fx

(3.1)

Where f is the focal length (distance between V and F as shown in Fig.3) Solar concentrators use a truncated portion of Parabola curve. The truncation is determined by rim angle ψrim (Fig. 3.1). By this angle, aperture diameter and height of the dish will be defined.

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Figure 3.1: Parabola geometry

3.1.1

Receivers and Rim Angle ψrim Optimization

One of the very famous types of receivers in the solar energy collection studies is cavity receiver (Fig. 3.2). The cavity receiver receives radiations only from one direction. As shown in Fig. 3.3, the best performance for a cavity receiver is at rim angle of 45 ̊ (Stine and Geyer, 2001). Therefore, 45 ̊ is the optimum rim angle ψrim for the cavity receiver.

Figure 3.2: Cavity Receiver

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Figure 3.3: Rim angle optimization (Stine and Geyer, 2001)

3.1.2

Defining the dish dimensions

At the edge of the parabola, there is the point (h, d/2) as indicated in Fig. 3.4. Applying this to the parabola Eq. 3.1 will give: (d / 2) 2 = 4 f h

( 3.2)

Also, considering the optimum rim angle for cavity receiver which is 45 ̊ (Figs. 3.3 and 3.4), then: d /2 f −h d /2 = f −h tan 45ο =

( 3.3)

Taking the dish diameter "d" as 1 meter (for easy transport, operation, maintenance and handling of the model dish), then Eqs. (3.2) and (3.3) will become:

4 f h = 0.25 f − h = 0.5 then

(3.4) (3.5)

f = h + 0.5

Subtituting Eq. 3.5 in Eq. 3.4, then 4 (h + 0.5) h = 0.25 4h 2 + 2h − 0.25 = 0 h=

− 2 ± 2 2 − 4 x 4 x (−0.25) 2 x4

= − 0.25 ± 8 / 8 = 0.104

Then, h = 0.104 m = 104 mm.

- 19 -

Using Eq. (3.5), f = h + 0.5 = 0.604 m = 604 mm. Using this focal length "f" in parabola Eq. (3.1), then the parabola is fully defined and truncated by the height "h" or the diameter "d" which are defined by the rim angle (Fig.3.4). Also, the dish is defined as full revolution of the generated parabola and accordingly can be fabricated (Fig. 3.5).

Figure 3.4: Parabola with optimum rim angle of 45 ̊

Figure 3.5: Dish dimensions

- 20 -

3.2

Dish performance estimation

In this section, the calculations will be made to find out performance estimation of the dish to produce concentrated thermal energy at the focus. The key factor in these calculations is the optical efficiency ηo, which will be explained, but the project will not focus on perfecting it during the construction.

3.2.1

Optical efficiency

The optical efficiency ηo (Wu, et al., 2010) depends on the optical properties of the materials involved (e.g., the reflectance of dish) and the various imperfections arising from the construction of the collector. It can be analyzed by identification of the different thermal loss mechanisms. These mechanisms are: 1) Shading loss: part of the reflective area of the dish is shaded by the receiver, which is located at the focal point of the dish. Dish manufacturing process involves that the matrix members will meet at the dish vertex and therefore they will intersect at a circle (Fig. 4.18). The resulted circle has a diameter of 20 cm which is more than enough to accommodate the receiver. Then shading loss is calculated as the ratio between the two areas 0.22 /12 which is 4%. Therefore, the remaining reflecting area is 1 – 4% = 96%. Accordingly, the factor (λ) for shading loss is 0.96. 2) Reflectivity loss: this loss is defined by the reflectivity (ρ) of the reflective material. In the project, aluminum sheet will be used and it has a reflectivity of ρ = 0.75 (Kaiyan, 2009). 3) Transmission loss: some of the reflected energy is lost through transmission of the sunlight in the air from the dish to the receiver, causing about 3% loss. Accordingly, the remaining transmitted energy is 97% and therefore the transmission loss factor τ = 97% or 0.97. 4) Absorption loss: the reflected radiation hitting the receiver cavity surface is partially absorbed which is determined by the absorptivity of the receiver surface. Using a receiver painted black, then the absorbtivity α = 0.98. 5) Cosine loss: quotient of total reflective area as seen from the sun. The dish will maintain its axis pointing towards the sun, then incidence angle of solar beam into the dish is zero. Therefore the factor of cosine loss = cos (θ) = cos (0 ̊ ) = 1.

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6) Spillage loss is fraction of radiation arriving outside the entrance aperture of the receiver. This loss may cause about 2% additional loss. Therefore the spillage loss factor Ω = 98% = 0.98. Sources of Spillage Loss •

Error in Concentrator Structure (Slope error).



Error in Receiver Alignment.

As per the above energy losses, the optical efficiency ηo = λ ρ τ α Ω cos(θ) = 0.96 x 0.75 x 0.97 x 0. 98 x 0.98 x 1 = 0.67 = 67%

However, this can be significantly improved by changing the reflective material to glass mirror because this material has high reflectance (ρ = 0.94) compared to ρ = 0.75 for aluminum sheet which was used because of fabrication limitations. Then, ηo = 0.67 ÷ 0.75 × 0.94 = 0.84 3.2.2

Calculation of Concentrated Solar Energy at the focus (Qc):

Qc = ηo Qs Where: ηo = optical efficiency = 0.67 , as obtained earlier. Qs : the total solar energy incident on the aperture area of the solar dish. Also, Qs = Ib Aa Where: Ib : the Sun energy at earth surface per unit area Ib = 643.5 W/m2 (this is the average value for 2002, 2003 and 2004; Actual data from Directorate General of Meteorology and Air Navigation, Sultanate of Oman, Appendix 8.1) Aa : aperture area of the dish = π d 2 /4 = π x 1 2 /4 = 0.785398 m2 Then Qs = 643.5 x 0.785398 = 505 W and Qc = ηo Qs = 0.67 x 505 = 338 W

- 22 -

3.2.3

Calculation of Concentration Ratio (CR):

The concentration ratio (CR) is the quotient of the energy per unit area at the focus (concentrated energy) and the sun energy per unit area at the dish opening which is the sun energy at earth surface per unit area (Ib). Therefore, 𝐶𝑅 =

𝑄𝑐 𝐴𝑟

Where:

𝐼𝑏

=

ηo 𝑄𝑠 𝐴𝑟

𝐼𝑏

=

ηo 𝐼𝑏 𝐴𝑎 𝐴𝑟

𝐼𝑏

𝐴

= ηo 𝐴𝑎 = ηo GCR (Stine and Geyer, 2001) 𝑟

Ar : the aperture area of the receiver. GCR: Geometrical Concentration Ratio, As per Section 3.2.1 on shading losses, a receiver of 20 cm diameter can be placed and this will result in GCR = Aa / Ar = (π x 12 /4) / (π x 0.202 /4) = 25 Also ηo = 0.67 for aluminum sheet as reflecting material, then CR = 0.67 x 25 = 16.75 But for the case of glass mirror as reflecting material, ηo = 0.84 and CR = ηo GCR = 0.84 x 25 = 21 The concentration ratio can be increased by two methods: 1) Increasing GCR: considering that the dish is already fixed to have 1m diameter (fixed Aa), then the GCR can be increased by minimizing the receiver area Ar. However, the receiver size cannot be reduced without limitation because the receiver needs to be large enough to capture maximum reflected light which is not exactly reflected to the focus but to an area around the focus. Therefore, the receiver size shall be optimized between being too small (so it cannot capture maximum reflected lights) and between being too large (so its large surface will lose more heat to the surroundings and it results in small GCR). Normally Ar shall be less than 1% of Aa (Wu et al., 2010). Then, taking Ar = 0.005 x Aa Accordingly GCR = Aa / Ar = 1/0.005 = 200 Also ηo = 0.67 as calculated earlier, then CR = ηo GCR = 0.67 x 200 = 134 Also, knowing that the dish has a diameter of 1m, then

- 23 -

(Receiver ′ s diameter)2 =

4Ar 4 x 0.005 x Aa 0.020 x π x 12 /4 = = π π π

= 0.005 m2

Then Receiver’s diameter = 71 mm.

2) Increasing ηo: The concentration ratio can be significantly increased by changing the reflective material to glass mirror because this material has high reflectance (ρ = 0.94) compared to aluminum sheet (ρ = 0.75). Then, ηo = 0.67 ÷ 0.75 × 0.94 = 0.84 and CR = ηo GCR = 0.84 x 200 = 168 However, the CR can be increased more by using large dishes with very small receivers. For example, if a receiver of 5 cm diameter is placed in the focus of a dish of 5 m diameter , then GCR will be 10,000 and CR will be 8,600 (considering ηo = 0.86 because the un-shading factor λ will change from 0.96 to 0.99 for 0.5 m circle of members). This means that the dish will be concentrating the sun energy in smaller area up to 8,600 multiples of the usual sun energy reaching the surface of the earth (this is also named that the dish produces the concentration of 8,600 SUNS, (Daniel Feuermann et al, 2002)).

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CHAPTER 4 Dish Design, Simulation and Fabrication This chapter describes the design and fabrication of the dish. Also, the installation of the reflective material will be described. As discussed in Chapter 2, there are two types of frames: matrix and solid frames. The matrix frame is used because of the following reasons: 1) Matrix frame has less weight compared to a solid frame. The less weight will need less power for tracking the sun. 2) Matrix frame is more practical and easier to fabricate for big size dish (more than 0.5 m diameter dish).

As specified in Chapter 3, the dish shall be fabricated as per the dimensions shown in Fig. 4.1.

Figure 4.1: Dish dimensions

4.1

Dish Design

A three dimensional geometry for the dish frame had been created in AutoCAD as shown in Fig. 4.2. This three dimensional geometry is used to minimize material used for fabrication.

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Figure 4.2: Three dimensional drawing of the matrix frame.

After optimizing and selecting the location and dimensions of many of the members in the matrix frame with the aid of three dimensional drawings, the system was then tested against failure using finite element combined with finite volume numerical methods. A 15o sector was enough to be analyzed because of angular symmetry. A 64-bit machine with parallel processing using four local processors had been used for the numerical analysis which makes it possible to analyze the whole system at once. Figure 4.3 shows the discretized system of the matrix frame to 137613 mixed solid elements: tetrahedral elements at complex geometry and brick elements at normal geometry. The discretization resulted in 308426 nodes and 10-4 error. Figure 4.4 shows a closer view for the mesh.

- 26 -

Figure 4.3: The overall system mesh.

Figure 4.4: Enlarged area for the matrix mesh.

The system was analyzed against failure for the static load and the load effect by wind (to account for additional dynamic loadings) using the commercial Finite Element/Volume Package ANSYS. A commercial low carbon steel (σY = 284.4 MPa) was used for the analysis which is the one used in market and hence for fabrication. Low carbon steel properties are averaged to be for Steel AISI 1015 with

- 27 -

density of 7800 kg/m3. For the static load, the matrix frame weight plus the additional components weights were considered. The effective stress (Von Mises stress) results are shown in Fig. 4.5 with a maximum value of 22.087 MPa (the runs of ANSYS were repeated with more mesh elements until the error becomes 10-4 which is very small and results in accurate results at very good level of convergence). The safety factor against static failure is 284.4/22.087 = 12.88 which will be reviewed after adding wind load.

Figure 4.5: Von Mises stress for the static load.

The wind effect on the matrix frame is a coupled-field problem where the pressure load caused by wind will be numerically calculated using CFX package and then to be transferred to a mechanical stress analysis package (ANSYS-Mechanical). A fluid domain was generated around the matrix frame as shown in Fig. 4.6 with an inlet velocity of 13.85 m/s (50 km/hr) which is high velocity by considering Oman weather.

The mesh for the fluid domain and the matrix frame are shown in Figs. 4.7 and 4.8 respectively. Figure 4.9 presents a vector plot for the velocity profile around the focus holding frame which is the most affected area by wind.

- 28 -

Figure 4.6: CFX model for the wind analysis.

Figure 4.7: Fluid domain mesh (421985 tetrahedral elements).

- 29 -

Figure 4.8: Matrix frame mesh surrounded with fluid elements.

Figure 4.9: Velocity profile around the focus holder.

The resulted pressure on the frame is shown in Fig. 4.10 at which this pressure load was exported to ANSYS-Mechanical for the stress analysis.

- 30 -

Figure 4.10: Pressure distribution on the matrix frame resulted from wind load.

The effective stress raise up to 22.125 MPa (Fig. 4.11) when the wind and weight effects combined together which means a safety factor of 12.85. Even though this is a high safety factor against static yielding but it gives strong comfort about the structural rigidity of the frame and also it provides comfortable feeling that the dish will stand good against any vibration which may lead to loss of the parabolic shape and eventually loss of optical performance of the dish. The safety factor will be reviewed in Section 5.1 by adding dynamic loads.

Figure 4.11: Effective stress for combined wind and weight loads

- 31 -

4.2

Dish Fabrication

First, a fabrication board was prepared. Then dish members were made and joined to form the matrix frame. Finally, aluminum sheets were fixed to form the reflecting surface.

4.2.1

Preparation of Fabrication Board

As discussed in Chapter 3, the parabola is defined by using focal length “f” of 0.604 m. This focal length will be used in Eq. (4.1) to obtain the parabola points as listed in Table 4.1 where the x-maximum is the radius of the dish (that is 0.5 m).

y = x2 / 4 f

(4.1) same as 3.1 but axes are inverted.

Table 4.1. Parabola Points x (m)

y (m)

x (m)

y (m)

-0.500

0.104

0.100

0.004

-0.450

0.084

0.150

0.009

-0.400

0.066

0.200

0.017

-0.350

0.051

0.250

0.026

-0.300

0.037

0.300

0.037

-0.250

0.026

0.350

0.051

-0.200

0.017

0.400

0.066

-0.150

0.009

0.450

0.084

-0.100

0.004

0.500

0.104

x (m)

y (m)

-0.050

0.001

0.000

0.000

0.050

0.001

The points (from x = -0.050 to 0.050) will not be considered during dish matrix fabrication in order to avoid overlapping of matrix members. The effect of this is already discussed while obtaining the optical efficiency in Chapter 3.

- 32 -

Because of the symmetry of the parabola around y-axis, one half is to be fabricated of the parabola only. Taking the positive half, the parabola graph is drawn as shown in Fig. 4.12:

Figure 4.12. Positive half of the parabola

This graph was plotted on a drawing paper. This paper was glued on a piece of thick wood. Nails were fixed on the graph points as per Table 4.1. Nails of small head were used in order to minimize the sticking of bars during fabrication. Now, the piece of wood with the graph on the drawing paper and the nails form the fabrication board. The fabrication board is shown in Fig. 4.13.

Figure 4.13: Fabrication board.

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4.2.2

Members fabrication for the matrix frame

The fabrication bar (steel rectangular bar of 1 cm width and 3 mm thickness) was cut into the length of the parabola (fabrication board was used to find the physical length of the parabola). Also, another piece of the bar was cut into the length of the x-axis (which equals 0.5 - 0.1 = 0.4 m = 40 cm). This piece will be used as a support to the parabola. Now the parabola piece can be shaped into the parabola line by using Ibeam in the welder shop as can be seen in Fig. 4.14 (the I-beam shall be flipped up down).

Figure 4.14: Shaping the parabola piece.

As shown in Fig. 4.14, the parabola piece is hammered and shaped into parabola using the inverted I-beam. Then, the hammered piece will be compared to the parabola (formed by nails) on the fabrication board. If the piece does not fit on the nails of the fabrication board, then it shall be hammered again until it fits on the nails. After that, the parabola piece was put on the fabrication board and it was aligned with the nails. Also, x-axis piece was put on the fabrication board and it was attached to the x-axis. After putting both pieces on the fabrication board, the welder can take measurements of the differences in the height between the two pieces in different locations and then he will cut some pieces (connectors) from the fabrication bar using those measurements. Then, those connectors will be used to join the parabola piece to the x-axis piece by welding (also, the two pieces are welded

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together at the start point). The number of connectors chosen was three and last one is preferred to be at the end of the parabola. After joining the parabola piece to the supportive piece (x-axis piece), the end points of the parabola piece were compared to parabola nails and then being trimmed for any extra lengths in the parabola piece. Similarly, it is preferred that to compare the end point of the x-axis piece to the xaxis on the fabrication board and trim the extra length in the x-axis piece as well. Now, the joined parabola piece and x-axis piece will form a structural member for the matrix solar dish construction. Revolution of the parabola in Fig. 4.15 around yaxis will form the dish. Therefore, in order to form the matrix dish, we need to rotate the said member 360 degrees around the y-axis. Also, in order to have strong matrix, the rotation was done into 15 degrees sectors. Therefore, the number of required members is equal to 360/15 = 24 members. Those members were fabricated with an approximate cost of 1 RO per member. Figure 4.15 is showing one of those members.

Figure 4.15: The construction member.

In order to assess the fabricated parabolic profile, the parabola was drawn using parabola equation (y = 4 f x) and this is the reference profile. Also, the fabricated parabola profile was marked on the same drawing paper as shown in Fig. 4.16. The maximum deviation is 5 mm and the minimum deviation is zero. Therefore, the error is 5-0 = 5 mm (G. Henzold, 1995).

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Figure 4.16: The fabrication error

4.2.3

Joining the Members to Form the Matrix Frame

Because we started the parabola at x = 0.1 m, then a half of a circle of radius = 0.1 m was drawn on white large paper (size: 100 x 70 cm). This half-circle was divided in segments (each of which is 15 degrees which is the same angle used in dividing the rotation that forms the dish). The lines between the segments are preferred to be extended to the edges of the paper in order to have them in sufficient lengths for alignment of the members' bases (x-axis pieces). This drawing forms the joining drawing which is shown in Fig. 4.17.

Figure 4.17: Joining drawing

Now, the members were put on the extended lines such that the start point of the parabola piece was put outside the half-circle at the circle’s circumference and the center line of the member's base was aligned on the extended line outside the halfcircle. After that, the bases of the members were joined together by welding

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connectors between them. Two connectors were welded between each two bases. After joining most of the members on the half-circle, the joined members can be rotated outside the half-circle except three of them. These three members shall be aligned at one end of the half-circle, and then other members can be added on the half-circle and joined/welded to previous members. This shall continue until the completion of the circle (this will form the complete matrix dish). After that, the matrix dish was flipped up-down. Then, more welding was done on the connectors between members (it is important that center of the dish does not go down in this stage). Also, steel bar (square cross-section 1.1 x 1.1 cm) was added at the bottom of the matrix dish as a support. Another important support is the support at the center of the matrix dish which was a steel sheet (thickness 1 mm); all members should be welded to this sheet especially at the start of the parabola. This will complete the matrix solar dish as shown in Fig. 4.18.

Figure 4.18: The matrix dish

4.2.4

Fixing the Wood and Aluminum Sheets on the Matrix Dish

A piece of stiff white paper was put and cut to cover four members in the matrix dish (also it was bent in the parabolic shape). Then, it was put on a sheet of decoration wood (wood sheet having thickness of 1mm) and mark-up was made on the wooden sheet. Then according to the mark-up the wooded sheet was cut and similarly a number of 8 wood pieces were cut to cover the whole dish because each piece will

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cover 3*15 = 45 degrees and 360/45 = 8 pieces. Similarly, 8 pieces were cut from aluminum sheets (cooking sheets of 0.5mm thickness). Sharp knife was used in cutting the wood sheets and sharp steel plate was used to cut the aluminum sheets. The wood pieces were glued one by one on the dish using wood glue (a wood glue is shown in Fig. 4.19). During the drying time of the glue, the wood pieces shall be pressed using inverted members (Figure 4.20) and heavy stones. A piece of wood (9 mm thickness) shall be put between the inverted members unit and the stones in order to distribute the load of the stones. The pressing shall take around four hours. The pressing is shown in Fig. 4.19.

The unit of inverted members was fabricated by similar way of fabricating parabola pieces. Two steel pieces from the fabrication bar were used; namely, a parabola piece and an axis piece. The parabola piece was hammered to take the shape of the curve above the nails of the fabrication board (this is unlike parabola piece of the dish members because this piece was formed using the curve below the nails). The axis piece is a straight piece having the length of around 0.4 m (length = xmaximum – xminimum = 0.5 – 0.1 = 0.4 m). The axis piece was put on the fabrication board along the axis y = ymaximum = 0.104 m. Also, the parabola piece was put on the fabrication board above the nails. Then the two pieces were welded togther using connectors (straight pieces from the fabrication bar). Three connectors should be welded between the two pieces and the two pieces should be welded at the point (0.5, 0.104). Similarly, another four inverted members were made. Then, the four members shall be put on the joining drawing and their central lines of their bases (axis pieces) shall be aligned on the extended lines outside the circle such that the start point of the parabola is projected on the circumference of the circle. By this, the inverted members will be 15 degrees apart like the dish members. Then, the inverted members shall be connected by welding three straight bars from the fabrication bar as shown in Fig. 4.20. Consequently, the unit of the inverted members will be completed as shown in Fig. 4.20. The complete system is shown in Fig. 20.

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Figure 4.19. Pressing the wood pieces

Figure 4.20. The unit of inverted members

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Figure 4.21: The dish after gluing the wooden pieces

Then, the aluminum pieces were glued using the same glue but no need for pressing. Figure 4.22 shows the dish after completing gluing of aluminum pieces.

Figure 4.22: The dish after completing gluing of aluminum pieces

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After that, a receiver holder was fixed as per the calculation of focus point in chapter 3. A straight piece of the fabrication bar having the length of 101 cm will be enough for making one member for the holder. After 5 cm length from this piece, a 90 degrees bend shall be made. This 5 cm length will be the bottom of the holder and it shall be drilled with two holes (Figure 4.23) for bolt/nut fixing at the center of the dish. Above this 5 cm length, the focal length (f = 0.604 m) shall be left straight and then another 90 degrees bend to be made. After that, another 5 cm shall be left straight and then a 90 degrees bend to be made. After this bend, 10 cm length is left straight and then a 90 degrees bend shall be made and this will be followed by 5 cm straight length and then one last 90 degrees bend. This will form one member for the holder (one member is shown in Fig. 4.23). Similarly, another three members shall be made. Then all the four members will be tightened together using thin wire such that each two members are 45 degrees apart (this will form the holder). After that, the holder was put on the center of the dish and eight marks were drawn around the center of the dish as per the holes on members. These marks to be drilled and then the holder can be bolted to be at the center of the dish. The dish with the holder of the receiver is shown on below Fig. 4.24.

Figure 4.23: Member for the holder of the receiver

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Figure 4.24: The dish with the holder of the receiver.

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Chapter 5 Design and Fabrication of Dish Base and Tracking Mechanism This chapter will describe the fabrication of the tracking mechanism. The tracking mechanism will transfer the motion from the drivers to the dish so that the dish will follow the sun. The dish shall follow the sun in two directions: altitude and azimuth directions. Therefore, the tracking mechanism will enable the drivers to change the altitude and azimuth angles for the dish. The design of the tracking mechanism is such that the tracking is possible in both altitude and azimuth directions at the same time.

5.1

Design of the Tracking Mechanism

In chapter 4, the dish design and fabrication were explained. The tracking mechanism structure will be discussed and designed in this section. The representative three dimensional geometry had been developed in AutoCAD and then exported to ABAQUS for finite element analysis as shown in Fig. 5.1. The motor effect is done through a rotational speed of 6 rad/hr as shown in the Fig.. However, the whole frame is restricted against vertical motion at the interface with ground.

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Notion restrain at the frame-ground interface

Rotational boundary condition of 6 rad/hr

Point mass representing the dish

Figure 5.1: Representative geometry and boundary conditions of the mechanism frame.

A total of 44569 mixed elements had been used and this implies negligible error of 10-4 in the results. Three dimensional elements (8276 element) was used for the members between the base and holder only while all other members was meshed using shell elements which reduced the computational time significantly to around five hours only. The mesh is shown in Fig. 5.2.

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Figure 5.2: Finite element mesh of the mechanism frame.

Dynamic analysis was preformed for the mechanism structure under the applied loads and realistic constraints. The run took around five hours on a super computer with eight GB full RAM memory and four parallel processors working together for the whole domain.

Figures 5.3 and 5.4 shows the effective stresses in the system. The holder is experiencing the maximum stresses in the system where it reached up to a value of 73.42 MPa that implies a safety factor of 3.87 (this is high factor but it will count for severe cases such as heavy rains). The stress analysis is shown in film inside the CD which is attached to this report. This concludes the dynamic structural safety of the mechanism frame.

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Figure 5.3: Effective stress of the holder (Pa).

Figure 5.4: Effective stress of the base (Pa).

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5.2

Fabrication of Tracking Mechanism and Dish Base

The construction consists of three parts: an altitude box, a rotational axis for azimuth direction and dish foundation. These parts were joined by bolts and nuts which ease transporting the whole system.

5.2.1

Fabrication of the Altitude Box

With reference to Fig. 5.5, altitude box is a structure which contain the dish while it is moving in the altitude angle and it will provide space for the dish motion in the altitude direction. This box will have four sides. One of these sides is the rotation axis for tracking in the altitude direction. This axis shall be built from 1" steel pipe having the thickness of 3mm (this pipe shall be reinforced by another embedded 3/4" steel pipe having 2mm thickness where the ends of the two pipes shall be welded together). Each end of the axis shall be inserted and welded to used bearing (it is important to align the center of the pipes to the center of the bearings). After completion of building the structure for the tracking mechanism, the dish shall be fixed on the altitude axis such that the diameter (for the base circle for the dish) will be aligned and welded to the altitude axis and therefore this axis shall have a length longer than that of the dish diameter which is 1m (the axis length shall be taken as 1.4 m). A steel box (cross section of 2.5 cm x 2.5 cm) shall be used to make the other three sides. Each of the two bearing's casings shall be welded to a 75 cm length piece from the steel box (75 cm is longer than the dish radius and therefore the dish can move freely in the altitude box). Finally, these two pieces (75 cm long) shall be moved/adjusted until they are in the same plane and then a third piece from the steel box shall be used to connect them together (the third piece will be the opposite side to the rotating axis and the length of the third piece will be same as the length between the two welds at the bearings' casings).

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Figure 5.5: The dish with the tracking mechanism (jack motor not installed)

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5.2.2

Installation of the driver for tracking the altitude direction:

With reference to Fig. 5.6, both jack and normal motors were tested. The jack motor was preferred and therefore, the normal motor was replaced by jack motor because it was found more practical than normal motor. This is because jack motor will itself support the weight of the dish whereas in the case of normal motor the load will be on the gears which will lead to misalignment between the gears' teeth. Accordingly, the jack motor will provide better stability to the system.

The jack motor was fixed between the bottom side of the altitude box and almost the edge of the dish. This was in order to contain the altitude motion and to keep this motion within the altitude box. As can be seen in section 5.2.3, the whole altitude box (including altitude mechanism) will be fixed on the rotation axis for azimuth direction. This will give the flexibility to the tracking mechanism so that the dish can be simultaneously moved in both altitude and azimuth directions.

5.2.3

Rotation axis for azimuth direction

With reference to Fig. 5.5, solid circular steel bar having the diameter of 3 cm and the length of 60 cm shall be used as rotation axis in the azimuth direction. The bottom end of this bar shall be welded to a bearing (from car scrap). It is important to align the center of the bearing to be at the center of the bar. After leaving a length of 30 cm from the bearing, a gear shall be welded to the bar. The gear shall be in the same x-y plane (with reference to z-axis which is the height) and the center of the gear shall be aligned to be at the center of the bar. On the other top end, a bearing shall be entered and welded after leaving a length of 8 cm from the bar above the bearing (center of the bearing shall be aligned to be at the center of the bar). With reference to Fig. 5.7, the top end of the bar shall be welded to 5 mm thick plate (16 cm x 4 cm). Before welding this plate to the bar, the plate shall be drilled with two holes each of which is 15 mm diameter and then this plate shall be aligned with the center of the altitude box (bottom side). Then, the bottom side of the altitude box shall be drilled as per the holes of the plate because later the altitude box will be bolted to this plate (then the two rotational axes will be connected). After drilling the bottom side of the altitude box, the plate can be welded on the bar such that the bar's center is at the center of the plate.

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5.2.4

Dish Base

With reference to Fig. 5.5, the dish foundation shall be built from the same construction box that shall also be used for altitude box (see 5.5). The construction box is a steel box with cross section of 2.5 cm x 2.5 cm. Firstly; an angle (3 cm x 3 cm x 3 mm thickness) shall be used to build two rectangles (90 cm x 70 cm). Four pieces (36 cm long) from the construction box shall be welded between the two rectangles (at the corners). Also, another four pieces from the construction box and of the same length shall be welded between the two rectangles at centers of the rectangles' sides. The center of the top rectangle (middle of length and width) shall be identified. Then, the bottom bearing shall be placed at this center and the locations of the bearing's holes shall be identified because two pieces from the construction box shall be placed to cover these holes and those two pieces will be the direct carriers for the bottom bearing (Figure 5.7). After initial welding of the two pieces between the long sides of the top rectangle, the bottom bearing shall be again placed on the two carriers at the center of the foundation and the four bearing's holes shall be marked on the carriers. According to the marking, four holes shall be drilled on the two carriers (after the final welding of the carriers).

5.2.5

Installation of the driver for tracking in azimuth direction

With reference to Fig. 5.7, the motor gear shall be aligned to the same x-y plane and the center of this gear shall be aligned to the center of the motor axis. Then, the motor gear shall be welded to the motor axis. This axis shall be entered into a coupling (this coupling is mounted on the motor as a connection between the motor's axis and the motor itself). A bolt shall be screwed through the coupling in order to fix the motor's axis. The motor is a used motor of a car window. This motor shall be put on steel sheet (1 mm thick). The sheet shall be marked with the shape of the motor's base and according to the marking the sheet shall be cut. Also, the base of this motor has three holes which shall be marked and then drilled on the sheet. This sheet will form the motor's board. At the assembling stage, the holes shall be used to bolt the motor on its board. The motor with its board, axis and gear shall all be taken together and the motor's gear shall be aligned to the axis's gear which is the gear welded to the tracking axis for azimuth direction (Figure 5.7). Simultaneously, the height of the motor's stand shall be measured (refer to Fig. 5.7). This stand will connect the motor board to the direct carrier which shall be welded on the dish foundation. According

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to the measured height of the motor's stand, a piece from the construction box shall be cut and welded to the motor's board. Also, the direct carrier for the motor's stand shall be cut and welded with initial welding (tack welding). After confirming the alignment between motor's gear and axis's gear, the carrier of motor's stand shall be fully welded to the dish foundation. Then, the dish shall be fixed on the altitude axis such that the diameter (for the base circle of the dish) will be aligned and welded to the altitude axis noting that the center of altitude axis shall be at the center of the base circle of the dish. Also, the bottom bearing shall be bolted on the dish foundation. Then the whole altitude box including the welded dish shall be bolted on the plate at the top of azimuth axis (rotation axis for azimuth direction). Also, the motor for azimuth direction shall be bolted on its board. By this, the tracking mechanism will be completed (Figure 5.8). 5.2.6

Selection of the driving motors

Altitude motor The volume of the dish (with receiver's holder) is 1431879.9247 mm3 and the density of the steel AISI 1015 is 7800 kg/m3. Therefore the mass is 1431879.9247 x 10-9 m3 x 7800 kg/m3 = 11.169 kg and the weight on the altitude motor will be 11.169 kg x 9.8 m/s2 = 109.5 N. The minimum load available for commercial motors is 1500 N and therefore the selected motor model is LA36 made by NAKIN.

Azimuth motor The maximum sun angular speed is 178.01 degrees/hour (appendix 5.1). Therefore the dish shall rotate at the same speed. Then 178.01/360 multiplied by the dish circumference will give the distance which the dish will pass each hour. This distance is 178.01 x π x D/360. Since D is the diameter of dish aperture, then the distance will be 178.01 x π x 1/360 = 1.5534 m/hr = 0.4315 x 10-3 m/s. The dish shall achieve this speed within one second and therefore the acceleration will be 0.4315 x 10-3 m/s2. Accordingly F = ma = 11.169 kg x 0.4315 x 10-3 m/s2 = 4.819 x 10-3 N and T = F x distance from the center = F x D/2 = 4.819 x 10-3 x 1/2 = 2.410 x 10-3 N.m. The minimum load available for commercial motors is 3 N.m for car window motor. Therefore, the selected motor is the window motor model HT300-1 made by HOX (Ningbo Hengte Automobile Parts Company).

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5.2.7

Features of the tracking mechanism

1) Simultaneous tracking in both altitude and azimuth directions. 2) Moveable structure because the structure can be dismantled into three parts: foundation, azimuth axis and altitude box (including the dish and altitude tracking mechanism). These three parts are just bolted together.

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Figure 5.6: Normal motor is replaced by Jack motor for tracking in altitude direction.

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Figure 5.7: Dish foundation and azimuth axis

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Figure 5.8: complete tracking mechanism

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CHAPTER 6 Control System Design and Setup The control circuit is required to direct and control the motions of the motors so that the motors will move the dish until the dish faces the sun in order to maximize energy collection. The control circuit will get input signals from light sensors. These signals will be processed within the control circuit which will send the right output to the motors so that the dish continuously faces the sun.

6.1

The conceptual design of the control circuit

The function of the control circuit is to manage the motors so that they will keep the dish facing the sun. The control circuit shall automatically recognize the dish position with respect to the sun. If the dish is not facing the sun, then the circuit shall force the motors to move the dish in the right direction until the dish faces the sun and then the circuit will stop the motors. However, if the dish is facing the sun, then the circuit will not send power to the motors. Recognition of the dish's position will call for installing input device which will send signals that can be processed by the circuit. Also, stopping the motors will require including switch in the control circuit. Moreover, moving the dish in the right direction will require rotating the motors clockwise direction and anticlockwise direction. This means that the circuit shall have arrangement for reversing the electrical polarity of the motors.

6.2

Selection for the components of the control circuit and System Setup

6.2.1

Selection of the component for input signal

The input component shall be able to sense the degree of lighting so that this sensitivity can be measured by the control circuit which will force the dish to follow the sun. The light intensity shall be converted to a signal which can be analyzed in the control circuit. Accordingly, the input component shall have two features: sensitivity to sun and possibility of converting this sensitivity to signal. The Light Dependent Resistor (LDR) is sensitive to light intensity because its electrical resistance changes according to light intensity. Different electrical

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resistance can be analyzed as a signal and therefore LDR can be used as an input component. Resistance of the LDR decreases as it experiences more dense light. This feature is very suitable because if the dish is not directly facing the sun, then the different edges of the dish will have different light intensity. Therefore, placing two LDRs at two opposite edges will provide different resistances at each edge. This difference in the resistances can be analyzed by the control circuit. Therefore, the LDRs are selected as input components for the control circuit.

6.2.2

Selection of other functional components

The functional components are those components which will enable the control circuit to perform the two functions mentioned in the conceptual design of the circuit in section (6.1). Stopping the power requires switch in the circuit. One of the simple electrical switches is the relay. The other function of the circuit is reversing the motor motion and this function requires reversing the electrical polarity of the motor. Revising the polarity means that each shall have two sources for electrical charges. One of the sources should be of positive electrical charge and the other source shall be of negative electrical charge. In other words, each pole shall have a switch which can select either positive or negative electrical charge. Therefore for the two poles of the motor, two switches will be required and those switches can be again electrical relays. Those connections between the motor, two relays and positive/negative charges are shown in Fig. 6.1. Therefore, the relays are selected as functional components.

6.2.3

Connection between input circuit and functional circuit

The functional circuit is of high voltage compared to the input circuit. This is because the input circuit is sensitive circuit which is can be affected by small difference in the resistance of the LDRs. On the other hand, the functional circuit is required to drive the bit large motors. Accordingly, the two circuits shall be separated. The connection between the two circuits shall be by a component which will identify the signal from the input circuit and accordingly open or close the functional circuit (motor circuit). The component which can do this is the transistor. Most bipolar transistors used today are NPN, because electrical mobility in NPN type is higher than electrical mobility in PNP type of semiconductors, allowing greater currents and faster operation. Therefore, NPN transistor is selected.

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6.2.4

Connecting all components together

The connections between the input circuit, functional circuit and the transistor are shown on Fig. 6.1. Also, a variable resistor is installed in order to adjust the sensitivity of the input circuit with respect to the light intensity on the LDRs.

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Figure 6.1: Control circuit diagram (see table 6.1 for the symbols of the components)

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Table 6.1: Symbols for the components of the control circuit Wires and connections Component

Circuit Symbol

Function of Component

Wire

To pass current very easily from one part of a circuit to another.

Wires joined

A 'blob' should be drawn where wires are connected (joined). Wires connected at 'crossroads' should be separated slightly to form two Tjunctions, as shown on the right.

Wires not joined

It is often necessary to draw wires crossing even though they are not connected. The 'bridge' symbol shown on the right is preferred because the simple crossing on the left may be misread as a join where a 'blob' is forgotten.

Power Supplies Component

Circuit Symbol

Function of Component Supplies electrical energy. DC = Direct Current, always flowing in one direction.

DC supply Output Devices: Component

Circuit Symbol

Function of Component

Motor

Converts electrical energy to kinetic energy (motion).

Inductor (Coil, Solenoid)

A coil of wire which creates a magnetic field when current passes through it. It can be used for converting electrical energy to mechanical energy by pulling on something through the magnetic field (as used in the relay).

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Table 6.1: Symbols for the components of the control circuit (continued) Switches Component

Circuit Symbol

Function of Component A 2-way changeover switch directs the flow of current to one of two routes according to its position (as in the relay)

2-way Switch

An electrically operated switch, NO = Normally Open, COM = Common, NC = Normally Closed.

Relay

Resistors Component

Circuit Symbol

Function of Component This type of variable resistor with 3 contacts (a potentiometer) is used to adjust the resistance in the circuit and therefore the sensitivity of the LDRs to the sunlight density.

Variable Resistor (Potentiometer)

Transistors Component

Circuit Symbol

Function of Component A transistor amplifies current. It can be used with other components to make an amplifier or switching circuit.

Transistor NPN

Sensors (input devices) Component

LDR

Circuit Symbol

Function of Component Converts brightness (light) to resistance (an electrical property). LDR = Light Dependent Resistor

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6.3

Control Circuit Specifications and Verification

The control circuit was connected as per Fig. 6.1. The following commercially available components were tested in the circuit and found suitable: 1) LDR having resistance ranging from 200 Ω to more than 2000 kΩ. 2) Variable resistor of 100 kΩ resistance. 3) Relay. The specifications are: •

Activating voltage of the magnetic coil: 6Vdc and



Maximum allowable current: 10 A.

4) NPN transistor S9014 B135. The Specifications are: •

Base-Emitter Saturation Voltage (VBE(sat)): 1 Vdc (required to open base-emitter junction and activate the transistor).



Maximum Collector-Base Voltage (VCE(0)): 50 Vdc.



Maximum Collector Current (IC(max)): 100 mAdc.



Maximum Base current (IB(max)): 100 μAdc (note: this maximum current is at Emitter-Base Breakdown Voltage which 5Vdc).



Maximum Emitter current (IE

(max))=

IC(max) + IB(max) = 100 mAdc +

100 μAdc = 100.1 mAdc which is practically IC(max). Figure 6.2 shows schematic diagram for the parameters of the specifications for the NPN transistor. The circuit was tested with both motors and it was found suitable. Figure 6.3 shows picture of the control circuit. Also, a comparison is shown in table 6.2 to confirm that the limits of the components are not exceeded in the actual circuit.

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Table 6.2: Comparison between component's limits and actual conditions in the circuit. Limits of the component

Actual condition in the Conclusion circuit

Activating voltage of the 8.965

Vdc

for any 8.965 is more than 6Vdc and

magnetic coil of the relay: relay's coil

therefore magnetic coil will be

6Vdc

activated.

Maximum

allowable Maximum current is 2.3 A is less than the maximum

current for the relay: 10 A.

2.3 A for the case of allowable current of 10 A and azimuth motor circuit.

therefore the relay will not have over current.

Maximum

Collector- Maximum voltage is 13 13 V is less than the maximum

Base Voltage (VCE(0)): V for the case of allowable voltage of 50 V and 50 Vdc for the transistor

Altitude motor.

therefore the transistor will stand in the motors' circuits.

Maximum Current

Collector IC = 59 mA

(IC(max)):

50 mA is less than the maximum allowable current of 100 mA and

100

therefore the transistor will not have

mAdc for the transistor

over current.

Figure 6.2: schematic diagram for the parameters of the specification for the NPN Transistor

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Figure 6.3: Control Circuit picture

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CHAPTER 7 Testing of the Tracking System and the Dish This chapter describes testing of the dish with the two axes tracking system. The chapter includes two parts. The first part verifies the dish performance. The second part describes testing the tracking system with the dish.

7.1

Verifying Dish Performance

The dish with the receiver holder were placed outdoors. The dish was aligned to be in the position of facing the sun. It was confirmed that the dish is facing the sun by ensuring that there is no shadow for the receiver holder. Then, it was noted that one portion of the holder get heated up. This portion is the focus because the parabolic dish will reflect sunlight to one focal point (focus). Accordingly, the focal length was measured and found 60 cm which is very good compared to the calculated value which is 0.604 m. This implies an error of 4 mm which means error of 0.004/0.604 = 0.7%.

7.2

Testing the dish with tracking system

The LDRs were put in their casings. The casing is 3.5 cm length of black electrical pipe (1/2 inch diameter). The casing is totally rapped with black tape and two holes were made for the light entry to the LDR (Figure 7.1). In order to track the sun in the azimuth direction, two LDRs with the casings were installed on the right and left edges of the dish as indicated in Fig. 5.5 (these two edges are at 180 ̊ deference). These LDRs were connected to the control circuit as shown in Figs. 6.1 and 6.3. Also, the output wires from both relays were connected to the azimuth motor as indicated in Figs. 6.1 and 6.3. Finally, a dual DC power source (Figure 7.2) was connected to the power supply wires of the control circuit as shown in Figs. 6.1 and 6.3 (note: the dual power supply has two output terminals and those are grounded together by connecting their negative terminals together and the common negative terminal was connected to the circuit). By completing these connections, the system will be ready to track the sun and move the dish to follow the sun and be facing the sun.

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In order to test the dish with the tracking system, one connection was kept unconnected like the connection for the power supply to the motor of azimuth motion. Also, the dish was kept in position of not facing the sun (this can be ensured by seeing shadow of the receiver holder). Once the motor power supply was connected, the motor started moving the dish in the direction of facing the sun and when the dish faced the sun the motor stopped (at this stage the shadow of the receiver holder was minimum). This test was recorded in a CD as video which is attached to this report. For tracking in the other direction (altitude motion), the control circuit was connected to the other two LDRs (top and bottom LDRs as indicated in Fig. 5.5) and the output wires were connected to the altitude motor. The dish was kept in position not facing the sun. After completing all connections, the altitude motor immediately started moving the dish in the direction of facing the sun and when the dish faced the sun the motor stopped (note: if the motor moves the dish in the wrong "opposite" direction, then the motor polarity shall be reversed). This test for the motion in the altitude direction was recorded also in the same CD as video. Both tests showed good results and this was confirmed by having minimum shadow of the receiver holder at the moment when the motors stopped. Table 7.1 shows the actual voltages, currents and power of the system while testing.

Table 7.1: Actual voltages, currents and power of the dish system while testing Item description

Voltage (Volt) Current (Amp.) Power (W)

Azimuth motor

5.000

2.300

11.50

Altitude motor

13.000

0.295

3.84

Solar Resistors for azimuth direction 8.965

0.059

0.53

Solar Resistors for altitude direction

0.059

0.53

8.965

Total

16.40

- 66 -

Figure 7.1: LDR's casing

Figure 7.2: Dual Power Source

- 67 -

Chapter 8 Economical Analysis of the Dish System This chapter will provide the estimated cost of the dish: manufacturing, operation and maintenance costs. Also, the feasibility of the dish will be analyzed by comparing the costs with the output during the expected life for the dish. All the costs are taken in Rial Omani (R.O.) and up to three decimals.

8.1

Manufacturing and capital costs of the dish

8.1.1

Manufacturing cost

Table 8.1 shows the costs for manufacturing one dish with the two axes tracking system as described in previous chapters 4, 5, 6 and 7. The total cost is 181.650 R.O.

- 68 -

Table 8.1: Costs for manufacturing one dish with the two axes tracking system Description of cost item

Cost

Quantity

Total cost

(R.O.)

(pieces)

(R.O.)

Dish member

1

24

24

Fixing the members together to form the dish

16

1

16

Wood sheets and gluing them on the dish

1.250

8

10

Aluminum sheets and gluing them on the dish

0.625

8

5

Receiver holder and mounting it on the dish

6.5

1

6.5

Used bearing

4

3

12

Altitude tracking axis

3

1

3

Azimuth tracking axis (used material)

2.5

1

2.5

Altitude box and welding it to altitude bearings

11

1

11

1

15.5

1

5

1

3.5

1

4.350

1

6.6

Jack motor for tracking in the altitude angle and 15.5 fixing it to the altitude box Used motor for tracking in the azimuth angle

5

Gear for azimuth motor and welding it to motor's 3.5 axis. Coupling for azimuth motor and connecting rod to 4.350 the gear (this includes bolting between coupling and motor) The gear welded to azimuth tracking axis (including 6.6 the welding) Base box

10

1

10

Fixing the base bearing to the base box

6

1

6

Painting

5.5

1

5.5

Control Circuit

12

2

24

Solar Resistor (input)

0.300

4

1.200

Power adapter

2.5

4

10

Grand Totals

181.650

- 69 -

8.1.2

Capital cost:

The capital cost of the dish consists of the manufacturing and installation costs. The manufacturing cost of the dish system is calculated as 181.650 R.O. as in previous section. Also, a storage tank will be required to store the hot water. As per the calculations in section 8.4, the tank capacity shall be 227 liters. The tank shall be fully isolated. The tank cost is estimated to be 25 R.O. The other part of the capital cost is the installation cost which includes installation of the dish and motors (5 R.O.), tracking system (5 R.O.) and the piping (6 R.O.) between the cavity receiver and the tank. Therefore, the total installation cost is 16 R.O. Accordingly, the capital cost is 181.650 + 25 + 16 = 222.650 R.O.

8.2

Operational cost of the dish

The operational cost will include the electricity required to operate the dish and manpower required to set the dish in the position facing the east every night. However, considering that this dish will be installed for domestic use as water heater then the manpower cost will be eliminated because setting the dish shall part of daily house works. The electricity cost is shown in table 7.1.

Each year has 365.25 days in the average (by considering that February changes from 28 days to 29 days in the fourth year). However, taking into consideration that Oman has three months when heating water is not required which are May, June and July (refer to appendix 8.2), and then the solar heater will be required for nine months (273 days) a year. Also, average number of sunshine hours per day is 8 hours and 40 minutes (see appendix 8.1). Then the total operational hours per year are 273 x (8 + 40/60) = 2, 366 hours. As a result, the total consumed electrical energy will be 0.01640 kW x 2, 366 HR = 38.80 kWHR per year. The electricity production cost in Oman is 0.100 R.O. for each kWHR. Therefore, the total operational cost of the dish will be 38.80 x 0.100 = 3.880 R.O. per year.

8.3

Maintenance cost of the dish

Table 8.2 shows the costs of maintenance for one dish with the two axes tracking system. Considering that the solar dish will be used as water heater in houses, cleaning of the reflective material shall be done weekly as one of the regular home - 70 -

works and therefore this is considered as zero cost. The total annual cost is 42.333 R.O. Table 8.2: Costs for the maintenance of one dish with the two axes tracking system Description of cost item

Cost

Frequency Annual Cost

R.O. Changing the reflective material* Structure

maintenance

including

7 cleaning

R.O. Yearly

7

and 13

9 monthly

17.333

1.5

3 Monthly

6

4

4 Monthly

12

Annual

42.333

repainting Preventive maintenance for the mechanical parts:



Tracking mechanism: greasing and general check.



General check for the complete system.

Preventive

maintenance

and

repair

for

instrument/electrical parts (control system):



Check the solar resistors.



Cleaning of control circuit and check the power source.



Motors cleaning and checking.

Total

* The bed of the reflective surface was made from thin sheets of wood. However, it is suggested to weld permanent metallic sheet as bed for the reflective surface in order to eliminate the cost the frequent change of the bed. On other hand, this permanent bed installation is estimated to have the same cost as for the thin wood sheets and therefore there will be no additional costs in manufacturing of the dish. Accordingly, metallic sheet is considered for the cost calculations.

8.4

The Dish as a heater

In this section, calculations will be made to estimate the dish performance as a water heater. In order to do this, the heat gained by a cavity receiver placed in the focus of the dish will be calculated. Therefore, the heat losses will be analyzed in order to find the net heat gained by the receiver. Considering the cavity receiver is fully insulated except the cavity opening, and then heat loss by conduction is negligible compared to convection and radiation losses (Wu et al., 2010). Accordingly, it follows:

- 71 -

Tc = 42 ̊C (Achieving this temperature during the day will be sufficient to compensate for temperature reduction during the night and it will be sufficient to get the minimum temperature of 32 ̊C at the morning of next day). Ta = 28 ̊C (ambient air temperature averaged over the year; refer to appendix 8.2) Film (average) temperature between the cavity and ambient air is Tf = (42 + 28)/2 = 35 ̊C (308 K). With reference to table A-11in Heat Transfer book (Yunus A.Cengel, 1998), properties of air at Tf are listed below: Thermal conductivity k = 0.0261 + (0.0268 – 0.0261) x (308 – 300) / (310 – 300) = 0.0267 W/m. C ̊ . Similarly, Kinematic viscosity ν = (1.57 + 0.800 x (1.67 – 1.57)) x 10-5 = 1.65 x 10-5 m2 / s. Prandtl number Pr = 0.712 – 0.800 x (0.712 – 0.711) = 0.711 β = 1/Tf = 1 / 308 = 0.00325 K-1. With reference to section 7.2 in Heat Transfer book (Yunus A.Cengel, 1998): The characteristic length δ will have three cases: Case 1: When the sun is in the middle of the sky, the receiver cavity will be horizontal with hot surface facing down (for simplification, the cavity is considered as flat surface). Therefore: δ = area/perimeter = π r2 / (2πr) = π x 0.1002 / (2π x 0.100) = 0.050 m. Gravitational acceleration g = 9.8 m2/s Rayleigh number 𝑅𝑎 =

𝑔𝛽(𝑇𝐶 − 𝑇𝑎 )𝛿 3 9.8 𝑥 0.00325 𝑥 (42 − 28)𝑥 0.0503 Pr = 0.711 𝜈2 (1.65 𝑥 10−5 )2

Ra = 1.040 x 105

Nusselt number Nu = 0.27 Ra1/4 = 0.27 x (1.040 x 105)1/4 = 4.85 Heat transfer coefficient h = Nu k/δ = 4.85 x 0.0267 / 0.050 = 2.6 W/ m2. ̊ C Area for the cavity of the receiver is Ac = π r2 = π x 0.1002 = 31, 416 x 10-6 m2 (The cavity receiver is cylindrical with diameter of 20 cm and height of 25 cm). The rate of heat loss by natural convection will be 𝑄̇𝑐 = ℎ𝐴𝑐 (𝑇𝑐 − 𝑇𝑎 ) = 2.6 𝑥 31, 416 𝑥 10−6 (42 − 28) = 1.1 𝑊

Case 2: When the sun starts rising in the morning or at sunset at the end of the day, the receiver cavity will be vertical and therefore: δ = cavity diameter = 0.200 m - 72 -

𝑅𝑎 =

𝑔𝛽(𝑇𝐶 − 𝑇𝑎 )𝛿 3 9.8 𝑥 0.00325 𝑥 (42 − 28)𝑥 0.2003 Pr = 0.711 𝜈2 (1.65 𝑥 10−5 )2

Ra = 9.316 x 106

Nusselt number Nu = 0.59 Ra1/4 = 0.59 x (9.316 x 106)1/4 = 32.60 Heat transfer coefficient h = Nu k/δ = 32.60 x 0.0267 / 0.20 = 4.4 W/ m2. ̊ C The rate of heat loss by natural convection will be 𝑄̇𝑐 = ℎ𝐴𝑐 (𝑇𝑐 − 𝑇𝑎 ) = 4.4 𝑥 31, 416 𝑥 10−6 𝑥 (42 − 28) = 1.9 𝑊 Case 3: When the sun position is between its position at rising in the morning or at sunset at the end of the day and between the middle of the sky, the receiver cavity will be inclined at an angle. An average representative angle for the purpose of economical calculation is 45 ̊ (in the middle) and therefore: δ = cavity diameter = 0.200 m 𝑅𝑎 =

9.8 𝑥 0.00325 𝑥 (42 − 28)𝑥 0.2003 𝑔𝛽(𝑇𝐶 − 𝑇𝑎 )𝛿 3 Pr = 0.711 𝜈2 (1.65 𝑥 10−5 )2

Ra = 9.316 x 106 < 109 and there g shall be replaced by (g cos45 ̊ ) and then 𝑔 cos(45 ̊) 𝛽(𝑇𝐶 − 𝑇𝑎 )𝛿 3 𝑅𝑎 = Pr 𝜈2

9.8 cos(45 ̊) 𝑥 0.00325 𝑥 (42 − 28)𝑥 0.203 = 0.711 = 6.587 x 106 (1.65 𝑥 10−5 )2

Nusselt number Nu = 0.59 Ra1/4 = 0.59 x (6.587 x 106)1/4 = 29.89

Heat transfer coefficient h = Nu k/δ = 29.89 x 0.0267 / 0.20 = 4.0 W/ m2. ̊ C The rate of heat loss by natural convection will be 𝑄̇𝑐 = ℎ𝐴𝑐 (𝑇𝑐 − 𝑇𝑎 ) = 4.0 𝑥 31, 416 𝑥 10−6 𝑥 (42 − 28) = 1.8 𝑊

Accordingly, the maximum heat loss by natural convection is 1.9 W. This loss is negligible because it is less than 0.6% of the solar heat gained by the receiver (338W). For the radiation heat loss, the receiver cavity shall be made of copper because

copper has low emissivity. With reference to table A-14 in Heat Transfer book (Yunus A.Cengel, 1998), the emissivity (ε) of polished copper at 42 ̊ C (315K) can be interpolated as: ε = 0.04 + (0.05-0.04) x (315-300)/(500-300) = 0.04 Stefan-Boltzmann constant σ = 5.67 x 10-8 W/m2.K4

- 73 -

Sky temperature Ts = 28 – 6 = 22 ̊ C because sky temperature is typically assumed to be 6 Kelvins lower than ambient temperature (Stine and Geyer, 2001). The rate of heat loss by radiation will be 𝑄̇𝑟 = 𝜀𝐴𝑐 𝜎�𝑇𝑐 4 − 𝑇𝑠 4 � = 0.04 𝑥 31, 416 𝑥 10−6 𝑥 5.67 𝑥 10−8 𝑥 (3154 − 2954 ) 𝑄̇𝑟 = 0.2 𝑊

Therefore, the total heat loss by natural convection and radiation is 1.9 + 0.2 = 2.1 W. This loss is negligible because it is 0.6% of the solar heat gained by the receiver (338 W). Accordingly, the water in the receiver will gain net heat at a rate of 338 W. The water in the receiver shall be heated from 28 ̊ C to 42 ̊ C. Therefore, the difference in temperature ΔT = 42 - 28 = 14 ̊ C. With reference to table A-14 in Heat Transfer book (Yunus A.Cengel, 1998), the water density and specific heat Cp can be determined as: Water density (at 28 ̊ C) = 997 – (997-988) x (28-25)/(50-25) = 996 kg/m3 Water specific heat Cp = 4.18 kJ/kg. ̊ C (for water temperature range 25 to 50 ̊ C) The mass of water in the receiver m = volume x water density = receiver height x Ac x water density = 0.250 x 31,416 x 10-6 x 996 = 7.82 kg The required energy to heat this mass of water from 28 to 42 ̊ C is Eh = m Cp ΔT = 7.82 x 4.18 x 14 = 458 kJ. The water in the receiver is gaining net heat a rate of 338 W = 338 J/s = 0.338 kJ/s Therefore, required time to heat the water in the receiver from 28 to 42 ̊ C is Δt = 458/0.338 = 1, 355 sec = 22.6 minutes. The dish (solar heater) will be working during the day hours. The average sunshine duration is 8 hours and 40 minutes which is 520 minutes (refer to appendix 8.1). Therefore, the total receiver's volume, the solar heater can produce is 520/22.6 = 23.0 volumes. Accordingly, the total production of heated water = 23.0 x volume of receiver = 23.0 x receiver height x Ac = 23.0 x 0.250 x 31,416 x 10-6 = 0.181 m3 = 181 liters. The production of heated water can be significantly increased by changing the reflective material to glass mirror because this material has high reflectance (ρ = 0.94) compared to aluminum sheet (ρ = 0.75). Accordingly, the gained heat will be 338 W x 0.94 / 0.75 = 424 W (then total loss of heat due to convection and radiation - 74 -

which is 2.1 W is even more negligible because it's less than 0.5%). Accordingly, the net gained heat by the water in the receiver will be 424 W. Similarly, the required time to heat the water in the receiver from 28 to 42 ̊ C is Δt = 458/0.424 = 1, 080 sec = 18.0 minutes. Therefore, the total receiver's volumes which the solar heater can produce is 520/18.0 = 28.9 volumes. Accordingly, the total production of heated water = 28.9 x volume of receiver = 28.9 x 0.250 x 31,416 x 10-6 = 0.227 m3 = 227 liters The cost of installing glass mirrors is estimated as below: A glass mirror need to be cut in the same shape of wood sheet (triangular shape) and this will need to be cut into three pieces in order to allow the glass mirrors to take the curved shape of the dish. The cost of doing this is estimated to be 3.5 R.O. The total cost will be 3.5 x 8 = 28 R.O. because the dish will need 8 triangular pieces (refer to chapter 4). On the other hand, using wood and aluminum sheet costs 15 R.O. (refer to 8.1.1). The difference is 28 – 15 = 13 R.O. However, aluminum sheets will need to be changed every year with a cost of 7 R.O. (refer to 8.3). On the other hand, the glass mirror life is estimated to be 10 years and mirrors replacement cost is estimated to be same as installation cost plus 5 R.O. for mirrors removal (i.e. 28+5 = 33 R.O. per 10 years or 3.3 R.O. yearly). This means that the yearly maintenance cost will reduce by 7-3.3 = 3.7 R.O. Accordingly, the additional installation cost of the glass mirror will be recovered within 13 / 3.7 ≈ 3.5 years (the benefit of increased production of heated water will be explored in 8.5). Therefore, changing the reflective material to glass mirror is justified. Also, table 8.3 records the differences in the costs. Table 8.3: differences in the costs due to changing the reflective material to glass mirror Cost Category

Change (R.O.)

Capital cost: Manufacturing + 13 Maintenance

- 3.7 yearly

- 75 -

8.5

Costs of electrical heater

8.5.1

Capital cost

The total cost of an electrical heater consists of purchasing cost and installation cost. The purchasing cost of one heater (50 liters, 5 kW) is 19.5 R.O. The installation cost is estimated as 18 R.O. which includes both fixing the heater (6 R.O.) and electrical works from the electrical distribution board to the heater (12 R.O.). Therefore, the total capital cost for one electrical heater (50 liters, 5 kW) is 37.500 R.O. Similar to the solar heater, the calculations are considered for a house which needs 200 liters of hot water daily in cold months (the solar heater is producing 227 liters and that means 27 additional liters which will be considered as extra benefit of using solar heater). Therefore, four heaters of 50 liters will be required to get 200 liters and accordingly the capital cost will be 37.500 x 4 = 150 R.O.

8.5.2

Operational cost

The operation cost is the cost required run the electrical heater and heat the water. The electrical heater is heating the water by converting electrical energy to heat energy with an efficiency of 95%. Considering the same conditions of the solar heater, then the electrical heater will heat 50 liters from 28 to 42 ̊ C. Accordingly: ΔT = 42 – 28 = 14 ̊ C. Similar to the solar heater, water density (at 28 ̊ C) is 996 kg/m3. Mass (m) = Volume x density = 50 liters/ (1000 liters/m3) x 996 kg/m3 = 49.8 kg. Cp (specific heat for water) = 4.18 kJ/(kg. ̊ C) Then, the gained by water to increase the temperature from 28 to 42 ̊ C is: E = m Cp ΔT = 49.8 x 4.18 x 14 = 2, 914 kJ. Then considering the heater efficiency, the consumed electrical energy Ee can be calculated as: 0.95 Ee = 2, 914 kJ Ee = 3, 067 kJ = 3, 067 kJ x (1 kWHR/3600 kJ) = 0.85 kWHR. Similar to the solar heater, the calculations are considered for a house which needs 200 liters of hot water daily in cold months. Therefore, four heaters of 50 liters will be required and accordingly the total consumed electrical energy is 0.85 x 4 = 3.4 kWHR per day.

- 76 -

Taking into consideration that Oman has three months when heating water is not required which are May, June and July, and then the electrical heater will be required for nine months (273 days) a year. Therefore, the annual consumption of electrical energy is 3.4 x 273 = 928.2 kWHR. Considering the production cost of electricity which is 0.100 R.O. per kWHR, then annual cost for running the electrical heaters (200 liters) is 928.2 x 0.100 = 92.820 R.O.

8.6

Economical comparison between solar heater and electrical heater

Table 8.4 summarizes the calculations in this chapter and shows an economical comparison between the solar heater and the electrical heaters.

Table 8.4: economical comparison between the solar heater and the electrical heaters Cost element

The solar heater

The electrical heaters

Capital cost (R.O.)

222.650 + 13 = 235.650

150

+13 for changing to glass mirror as reflector. Yearly

42.333 – 3.7 = 38.633

maintenance

-3.7 for changing to glass heating element every 5 years).

(R.O.)

mirror as reflector.

Yearly

0.8 (considering 4 R.O. for changing the

operation 3.880

92.820

(R.O.) Extra benefit

Daily production of 27 Not applicable extra liters of hot water

Accordingly, the expenses for the first two years can be calculated as in table 8.5.

Table 8.5: The expenses for the first two years for both the solar heater and the electrical heaters Year

Expenses of the solar heater

Expenses of the electrical heaters

Year 1 235.650 + 38.633+ 3.880 = 278.163 150+0.800+92.820 = 243.620 Year 2 38.633+ 3.880 = 42.513

0.800+92.820 = 93.620

Total

337.240

320.676

- 77 -

As can be seen the solar heater is becoming economical in the second year compared to electric heater. In addition, the solar heater is producing 27 liters of hot water more than the electrical heater every day. Also, table 8.6 shows that solar heater will achieve savings of 425.420 R.O. over the electrical heater at the end of the tenth year which means an average saving of 42.542 R.O. per year. Moreover the electrical heaters daily produce 200 liters of hot water (average requirement for a house of 10 persons) and Oman population is around 2.5 millions. Then, the savings for Oman at the end of the tenth year will be 425.420 x 2.5 / 10 million R.O. = 106.355 million R.O.

Table 8.6: The expenses for the first ten years for both the solar heater and the electrical heaters Year

Expenses of the solar heater

Expenses of the electrical heaters

Year 1

235.650 + 38.633+ 3.880 = 278.163 150+0.800+92.820 = 243.620

Year 2

38.633+ 3.880 = 42.513

0.800+92.820 = 93.620

Year 3 to Year10 42.513 x 8 = 340.104

93.620 x 8 = 748.960

Total

1,086.200

660.780

Moreover, the two heaters can be compared using future value method. Knowing that the interest rate in Oman banks is between 8 to 12%, then The average interest rate r = (8%+12%)/2 = 10% = 0.10 For the electrical heaters: Capital cost C = 150 R.O. Annual expenses A = 93.620 R.O. Number of years N=10 years. The future value (F) for the expenses at the end of ten years will be: (1 + 𝑟)𝑁 − 1 1.1010 − 1 10 𝐹 = 𝐶(1 + 𝑟) + 𝐴 � � = 150 𝑥 1.10 + 93.620 � � 𝑟 0.10 𝑁

F = 1,881.123 R.O.

Similarly, for the solar heater: 𝐹 = 235.650 𝑥 1.1010 + 42.513 �

1.1010 − 1 � = 1,289.050 𝑅. 𝑂. 0.10

Therefore the solar heater will achieve savings of 1,881.123 – 1,289.050 = 529.073R.O. over the electrical heaters at the end of the tenth year. Moreover the - 78 -

electrical heaters daily produce 200 liters of hot water (average requirement for a house of 10 persons) and Oman population is around 2.5 millions. Then, the savings for Oman at the end of the tenth year will be 529.073 x 2.5 / 10 million R.O. = 132.268 million R.O.

As a conclusion, the solar heater is better than the electrical heaters for the reasons: 1) It more economical. 2) It has extra production (27 liters of hot water). 3) It will help to reduce pollution that is caused during electricity production from fossil fuels. Electricity production by fossil fuels causes 1.915 pounds of CO2 per kWHR for petroleum fuel, 1.314 pounds of CO2 per kWHR for gas fuel and 2.117 pounds of CO2 per kWHR for coal fuel (The U.S. Department of Energy and the U.S. Environmental Protection Agency, 2000).

Even though solar dish is better than electrical heater in water heating application but there are other competing solar technologies (like flat plate collectors). However, the solar dish shows strong economics which can be extended for other applications like steam generation because of the high concentration of solar energy in small area (the focus). Also, solar dishes have the highest efficiency among other solar technologies.

- 79 -

Chapter 9 CONCLUSIONS and RECOMMENDATIONS

The following conclusions are made: •

It is not necessary to get a perfect dish but a practical one which is “cost effective” is the key for a successful design.



Matrix frame is more practical for large size dishes because it has less weight, low cost and requires less power to operate the tracking system.



Sun tracking by sensing solar intensity is a very effective method compared to other tracking methods. This is because it has better efficiency.



Fabrication process by using a unit member (as explained in chapter 4) is cost effective.



Combination between angular motion (for azimuth direction) and linear motion (for altitude direction) for the dish’s tracking mechanism is very promising concept for tracking mechanisms.



Testing results for the dish and the tracking system showed the effectiveness of the design and fabrication process.



Simple use of the dish as a solar heater show economical benefits.



Simulation of the dish system in ANSYS and ABAQUS softwares showed safe structure under both static and dynamic loads.

The followings are recommendations for further studies: •

Improving reflectivity by having better reflecting surface.



Improving control system by better input devices and control circuits.

- 80 -

REFERENCES

A. Abene, V. Dubois, M. Le Ray and A. Ouagued, 2004, “Study of a solar air flat plate collector: use of obstacles and application for the drying of grape”, Journal of Food Engineering, Vol. 65, Issue 1, pp. 15-22. A. De Munari, D.P.S Capao, B.S. Richards and A.I. Schafer, 2009, “Application of solar-powered desalination in a remote town in South Australia”, Desalination, Vol. 248, Issues 1-3, pp. 72-82. A. Di Vecchia, G. Formisano, V. Rosselli and D. Ruggi, 1981, “Possibilities for the application of solar energy in the European Community agriculture”, Solar Energy, Vol. 26, Issue 6, pp. 479-489. A. Fernandez-Garcia, E. Zarza, L. Valenzuela and M. Perez, 2010, “Parabolic-trough solar collectors and their applications”, Renewable and Sustainable Energy Reviews, Vol. 14, Issue 7, pp. 1695-1721. A. Mellit, S.A. Kalogirou, S. Shaari, H. Salhi and A. Hadj Arab, 2008, “Methodology for predicting sequences of mean monthly clearness index and daily solar radiation data in remote areas: Application for sizing a stand-alone PV system”, Renewable Energy, Vol. 33, Issue 7, pp. 1570-1590. Adjar Pratoto, M. Daguenet and B. Zeghmati, 1998, “A simplified technique for sizing solar-assisted fixed-bed batch dryers: application to granulated natural rubber”, Energy Conversion and Management, Vol. 39, Issue 9, pp. 963-971. AL-Busaidi Yazeed Talib and AL-Siyabi Mousa Ali, 2006, “Design and implementation of a two axes tracking control system for a concentrating solar dish collector”, Sultan Qaboos University, Mechanical and Industrial Engineering Department, not published. Andreas Poullikkas, George Kourtis and Ioannis Hadjipaschalis, 2010, “Parametric analysis for the installation of solar dish technologies in Mediterranean regions”, Renewable and Sustainable Energy Reviews, Vol. 14, Issue 9, pp. 2772-2783. Antonis Tsikalakis, T. Tomtsi, N.D. Hatziargyriou, A. Poullikkas, Ch. Malamatenios, E. Giakoumelos, O. Cherkaoui Jaouad, A. Chenak, A. Fayek, T. Matar and A. Yasin, 2011, “Review of best practices of solar electricity resources applications in selected Middle East and North Africa (MENA) countries”, Renewable and Sustainable Energy Reviews, Vol. 15, Issue 6, pp. 2838-2849. - 81 -

Arbab H., B. Jazi and M. Rezagholizadeh, 2009, “A computer tracking system of solar dish with two-axis degree freedoms based on picture processing of bar shadow”, Renewable Energy, Vol. 34, Issue 4, pp. 1114-1118. Aydogan Ozdamar, Necdet Ozbalta, Alp Akin and E. Didem Yildirim, 2005, “An application of a combined wind and solar energy system in Izmir”, Renewable and Sustainable Energy Reviews, Vol. 9, Issue 6, pp. 624-637. Bernhard Dimmler and Rolf Wachter, 2007, “Manufacturing and application of CIS solar modules”, Thin Solid Films, Vol. 515, Issue 15, Proceedings of Sympodium O on Thin Film Chalcogenide Photovoltaic Materials, EMRS 2006 Conference - EMRS 2006 Symposium O, pp. 5973-5978. Christian A. Gueymard, 2009, “Direct and indirect uncertainties in the prediction of tilted irradiance for solar engineering applications”, Solar Energy, Vol. 83, Issue 3, pp. 432-444. Craig E. Tyner, 1990, “Application of solar thermal technology to the destruction of hazardous wastes”, Solar Energy Materials, Vol. 21, Issues 2-3, pp. 113-129. D. Hernandez, G. Olalde, G. Bonnier, F. Le Frious and M. Sadli, 2003, “Evaluation of the application of a solar furnace to study the suitability of metal oxides to be used as secondary reference points in the range 2000-3000 ◦C, Measurement, Vol. 34, Issue 2, pp. 101-109. Daniel Feuermann and Jeffrey M. Gordon, 1999, “Solar fiber-optic mini-dishes: a new approach to the efficient collection of sunlight”, Solar Energy, Vol. 65, Issue 3, pp. 159-170. Daniel Feuermann, Jeffrey M. Gordon and Mahmoud Huleihil, 2002, “Solar fiberoptic mini-dish concentrators: first experimental results and field experience”, Solar Energy, Vol. 72, Issue 6, pp. 459-472. Dilip Jain and Rajeev Kumar Jain, 2004, “Performance evaluation of an inclined multi-pass solar air heater with in-built thermal storage on deep-bed drying application”, Journal of Food Engineering, Vol. 65, Issue 4, pp. 497-509. E. Bilgen and B.J.D. Bakeka, 2008, “Solar collector systems to provide hot air in rural applications”, Renewable Energy, Vol. 33, Issue 7, pp. 1461-1468. E.-E. Delyannis and V. Belessiotis, 1995, “Solar application in desalination: the Greek Islands experiment”, Desalination, Vol. 100, Issues 1-3, pp. 27-34. Ehab AlShamaileh, 2010, “Testing of a new solar coating for solar water heating applications”, Solar Energy, Vol. 84, Issue 9, pp. 1637-1643. - 82 -

F.K. Forson, M.A.A. Nazha, F.O. Akuffo and H. Rajakaruna, 2007, “Design of mixed-mode natural convection solar crop dryers: Application of principles and rules of thumb”, Renewable Energy, Vol. 32, Issue 14, pp. 2306-2319. G. De Giorgi, S. Fumagalli, G. Rizzi and V. K. Sharma, 1991, “Design, development and experimental performance of solar collector-storage system for space heating applications”, Energy Conversion and Management, Vol. 31, Issue 1, pp. 75-93. G. Henzold, 1995, “Handbook of Geometrical Tolerancing Design, Manufacturing and Inspection”, John Wiley and Sons, Chichester. New York. Brisbane. Toronto. Singapore, pp. 203, 234. G. Manzolini, M. Bellarmino, E. Macchi and P. Silva, 2011, “Solar thermodynamic plants for cogenerative industrial applications in southern Europe”, Renewable Energy, Vol. 36, Issue 1, pp. 235-243. G. Schmidt, H. Zewen and S. Moustafa, 1980, “A solar farm with parabolic dishes (Kuwaiti-German project)”, Electric Power Systems Research, Vol. 3, Issues 1-2, pp. 65-76. George T. Koide and Patrick K. Takahashi, 1978, “Solar and wind energy applications in Hawaii”, Solar Energy, Vol. 21, Issue 4, pp. 297-305. Goswami D. Yogi, 1987, “Progress in Solar Engineering”, Hemisphere Publishing Corporation, USA. Govind N. Kulkarni, Shireesh B. Kedare and Santanu Bandyopadhyay, 2008, “Design of solar thermal systems utilizing pressurized hot water storage for industrial applications”, Solar Energy, Vol. 82, Issue 8, pp. 686-699. Hans Schnitzer, Christoph Brunner and Gernot Gwehenberger, 2007, “Minimizing greenhouse gas emissions through the application of solar thermal energy in industrial processes”, Journal of Cleaner Production, Vol. 15, Issues 13-14, Approaching zero emissions, pp. 1271-1286. Hong Li and Hongxing Yang, 2009, “Potential application of solar thermal systems for hot water production in Hong Kong, Applied Energy, Vol. 86, Issue 2, IGEC III Special Issue of the Third International Green Energy Conference (IGEC-III), pp. 175-180. Huseyin Gunerhan and Arif Hepbasli, 2007, “Determination of the optimum tilt angle of solar collectors for building applications”, Building and Environment, Vol. 42, Issue 2, pp. 779-783.

- 83 -

Ibrahim Reda and Afshin Andreas, 2004, “Solar position algorithm for solar radiation applications”, Solar Energy, Vol. 76, Issue 5, pp. 577-589. Iftikhar A. Raja, M. G. Dougar and R. S. Abro, 1996, “Solar energy applications in Pakistan”, Renewable Energy, Vol. 9, Issues 1-4, World Renewable Energy Congress Renewable Energy, Energy Efficiency and the Environment, pp. 11281131. Iskander Tlili, Youssef Timoumi and Sassi Ben Nasrallah, 2008, “Analysis and design consideration of mean temperature differential Stirling engine for solar application”, Renewable Energy, Vol. 33, Issue 8, pp. 1911-1921. J. Blanco, S. Malato, P. Fernandez-Ibanez, D. Alarcon, W. Gernjak and M.I. Maldonado, 2009, “Review of feasible solar energy applications to water processes”, Renewable and Sustainable Energy Reviews, Vol. 13, Issues 6-7, pp. 1437-1445. J. Joseph, R. Saravanan and S. Renganarayanan, 2005, “Studies on a single-stage solar desalination system for domestic applications”, Desalination, Vol. 173, Issue 1, pp. 77-82. J.P. Chiou, 1977, “On the study of applications of solar thermal energy for mobile homes”, Solar Energy, Vol. 19, Issue 5, pp. 449-466. Jaehyeong Lee, N. Lakshminarayan, Suresh Kumar Dhungel, Kyunghae Kim and Junsin Yi, 2009, “Optimization of fabrication process of high-efficiency and lowcost crystalline silicon solar cell for industrial applications”, Solar Energy Materials and Solar Cells, Vol. 93, Issue 2, pp. 256-261. Jayanta Deb Mondol, Mervyn Smyth and Aggelos Zacharopoulos, 2011, “Experimental characterisation of a novel heat exchanger for a solar hot water application under indoor and outdoor conditions”, Renewable Energy, Vol. 36, Issue 6, pp. 1766-1779. Jorge Gonzalez-Garcia, Sergio Vazquez-Montiel, Agustin Santiago-Alvarado, Alberto Cordero-Davila and Graciela Castro-Gonzalez, 2009, “A proposed design and fabrication of lenses and mirrors from a set of spherical rings that produce desired energy distributions for solar energy applications”, Solar Energy, Vol. 83, Issue 12, pp. 2205-2216. K.F. Fong, C.K. Lee, Z. Lin, T.T. Chow and L.S. Chan, “Application potential of solar air-conditioning systems for displacement ventilation”, Energy and Buildings, In Press.

- 84 -

K.S. Reddy and N. Sendhil Kumar, 2008, “Combined laminar natural convection and surface radiation heat transfer in a modified cavity receiver of solar parabolic dish”, International Journal of Thermal Sciences, Vol. 47, Issue 12, pp. 1647-1657. K.S. Reddy and N. Sendhil Kumar, 2009, “An improved model for natural convection heat loss from modified cavity receiver of solar dish concentrator”, Solar Energy, Vol. 83, Issue 10, pp. 1884-1892. Kaiyan He, Zheng Hongfei, Tao Tao and Xue Xiaodi, 2009, “Experimental investigation of high temperature congregating energy solar stove with sun light funnel”, Energy Conversion and Management, Vol. 50, Issue 12, pp. 3051-3055. Kalogirou Soteris A., 2004, “Solar thermal collectors and applications”, Progress in Energy and Combustion Science, Vol. 30, Issue 3, pp. 231-295. Leonard D. Jaffe, 1989, “Test results on parabolic dish concentrators for solar thermal power systems”, Solar Energy, Vol. 42, Issue 2, pp. 173-187. Lourdes Garcia-Rodriguez, Ana I. Palmero-Marrero and Carlos Gomez-Camacho, 1999, “Application of direct steam generation into a solar parabolic trough collector to multieffect distillation”, Desalination, Vol. 125, Issues 1-3, European Conference on Desalination and the Environment, pp. 139-145. Lourdes Garcia-Rodriguez, Ana I. Palmero-Marrero and Carlos Gomez-Camacho, 2002, “Comparison of solar thermal technologies for applications in seawater desalination”, Desalination, Vol. 142, Issue 2, pp. 135-142. Lovegrove K., G. Burgess and J. Pye, “A new 500 m2 paraboloidal dish solar concentrator”, Solar Energy, In Press. Lovegrove K., G. Burgess and J. Pye, 2011, “A new 500 m2 paraboloidal dish solar concentrator”, Solar Energy, Vol. 85, Issue 4, SolarPACES 2009, pp. 620-626. M. A. Karim and M. N. A. Hawlader, 2004, “Development of solar air collectors for drying applications”, Energy Conversion and Management, Vol. 45, Issue 3, pp. 329344. M. Karagiorgas, A. Botzios and T. Tsoutsos, 2001, “Industrial solar thermal applications in Greece: Economic evaluation, quality requirements and case studies”, Renewable and Sustainable Energy Reviews, Vol. 5, Issue 2, pp. 157-173. M. Keyanpour-Rad, H. R. Haghgou, F. Bahar and E. Afshari, 2000, “Feasibility study of the application of solar heating systems in Iran”, Renewable Energy, Vol. 20, Issue 3, pp. 333-345.

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M.M. Valmiki, Peiwen Li, Javier Heyer, Matthew Morgan, Abdulla Albinali, Kamal Alhamidi and Jeremy Wagoner, 2011, “A novel application of a Fresnel lens for a solar stove and solar heating”, Renewable Energy, Vol. 36, Issue 5, pp. 1614-1620. Md Azharul Karim and M.N.A. Hawlader, 2006, “Performance evaluation of a vgroove solar air collector for drying applications”, Applied Thermal Engineering, Vol. 26, Issue 1, pp. 121-130. Mo Wang and Kamran Siddiqui, 2010, “The impact of geometrical parameters on the thermal performance of a solar receiver of dish-type concentrated solar energy system”, Renewable Energy, Vol. 35, Issue 11, pp. 2501-2513. N. D. Kaushika and K. S. Reddy, 2000, “Performance of a low cost solar paraboloidal dish steam generating system”, Energy Conversion and Management, Vol. 41, Issue 7, pp. 713-726. N. K. Bansal, 1999, “Solar air heater applications in India”, Renewable Energy, Vol. 16, Issues 1-4, Renewable Energy Energy Efficiency, Policy and the Environment, pp. 618-623. N. M. Khattab and E.T. El Shenawy, 2006, “Optimal operation of thermoelectric cooler driven by solar thermoelectric generator”, Energy Conversion and Management, Volume 47, Issue 4, pp. 407-426. N. Sendhil Kumar and K.S. Reddy, 2007, “Numerical investigation of natural convection heat loss in modified cavity receiver for fuzzy focal solar dish concentrator”, Solar Energy, Vol. 81, Issue 7, pp. 846-855. N. Sendhil Kumar and K.S. Reddy, 2008, “Comparison of receivers for solar dish collector system”, Energy Conversion and Management, Vol. 49, Issue 4, pp. 812819. N.D Kaushika, 1993, “Viability aspects of paraboloidal dish solar collector systems”, Renewable Energy, Vol. 3, Issues 6-7, pp. 787-793. O. O. Badran, 2001, “Study in industrial applications of solar energy and the range of its utilization in Jordan”, Renewable Energy, Vol. 24, Issues 3-4, pp. 485-490. O. V. Ekechukwu and B. Norton, 1999, “Review of solar-energy drying systems III: low temperature air-heating solar collectors for crop drying applications, Energy Conversion and Management, Vol. 40, Issue 6, pp. 657-667. Oliver St. C. Headley, 1998, “Solar thermal applications in the West Indies”, Renewable Energy, Vol. 15, Issues 1-4, Renewable Energy Energy Efficiency, Policy and the Environment, pp. 257-263. - 86 -

Omar H. Al-Sakaf, 1998, “Application possibilities of solar thermal power plants in Arab countries, Renewable Energy, Vol. 14, Issues 1-4, 6th Arab International Solar Energy Conference: Bringing Solar Energy into the Daylight, pp. 1-9. P. Dorato and H. K. Knudsen, 1979, “Periodic optimization with applications to solar energy control”, Automatica, Vol. 15, Issue 6, pp. 673-676. P.J. Sonneveld, G.L.A.M. Swinkels, B.A.J. van Tuijl, H.J.J. Janssen, J. Campen and G.P.A. Bot, 2011, “Performance of a concentrated photovoltaic energy system with static linear Fresnel lenses”, Solar Energy, Vol. 85, Issue 3, pp 432-442 P.T. Tsilingiris, 1993, “Theoretical modelling of a solar air conditioning system for domestic applications”, Energy Conversion and Management, Vol. 34, Issue 7, pp. 523-531. Palavras I. and Bakos G. C., 2006, “Development of a low-cost dish solar concentrator and its application in zeolite desorption”, Renewable Energy, Vol. 31, Issue 15, pp. 2422-2431. Ph. Dind and H. Schmid, 1978, “Application of solar evaporation to waste water treatment in galvanoplasty”, Solar Energy, Vol. 20, Issue 3, pp. 205-211. R. Ramakumar and K. Bahrami, 1981, “Dispersed solar thermal generation employing parabolic dish-electric transport with field modulated generator systems”, Solar Energy, Vol. 27, Issue 1, pp. 7-11. R.E. Hogan Jr., R.D. Skocypec, R.B. Diver, J.D. Fish, M. Garrait and J.T. Richardson, 1990, “A direct absorber reactor/receiver for solar thermal applications”, Chemical Engineering Science, Vol. 45, Issue 8, pp. 2751-2758. Rafael Almanza, Perla Hernandez, Ivan Martinez and Marcos Mazari, 2009, “Development and mean life of aluminum first-surface mirrors for solar energy applications”, Solar Energy Materials and Solar Cells, Vol. 93, Issue 9, pp. 16471651. Ronnen Levinson, Paul Berdahl, Hashem Akbari, William Miller, Ingo Joedicke, Joseph Reilly, Yoshi Suzuki and Michelle Vondran, 2007, “Methods of creating solar-reflective nonwhite surfaces and their application to residential roofing materials”, Solar Energy Materials and Solar Cells, Vol. 91, Issue 4, pp. 304-314. Soteris A. Kalogirou, 2004, “Solar thermal collectors and applications”, Progress in Energy and Combustion Science, Vol. 30, Issue 3, pp. 231-295.

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Stine William and Geyer Michael, “Power From The Sun book, Chapters 8, 9 and others”,

Power

From

The

Sun.net,

2001,

Web.,

31

Oct.

2009,

Suleyman Karsli, 2007, “Performance analysis of new-design solar air collectors for drying applications”, Renewable Energy, Vol. 32, Issue 10, pp. 1645-1660. T. Noguchi, 1985, “Overview on thermal application of solar energy in Japan”, Solar and Wind Technology, Vol. 2, Issues 3-4, pp. 155-171. T.T. Chow, K.F. Fong, A.L.S. Chan and Z. Lin, 2006, “Potential application of a centralized solar water-heating system for a high-rise residential building in Hong Kong”, Applied Energy, Vol. 83, Issue 1, pp. 42-54. Tetsuo Noguchi, 1973, “Recent developments in solar energy research and application in Japan”, Solar Energy, Vol. 15, Issue 2, pp. 179-187. Theo Chidiezie Chineke and Ugochukwu Kingsley Okoro, 2010, “Application of Sayigh 'Universal Formula' for global solar radiation estimation in the Niger Delta region of Nigeria”, Renewable Energy, Vol. 35, Issue 3, pp. 734-739. U.R. Prasanna and L. Umanand, 2011, “Modeling and design of a solar thermal system for hybrid cooking application”, Applied Energy, Vol. 88, Issue 5, pp. 17401755. U.R. Prasanna and L. Umanand, 2011, “Optimization and design of energy transport system for solar cooking application”, Applied Energy, Vol. 88, Issue 1, pp. 242-251. U.S.Department of Energy and the U.S. Environmental Protection Agency, 2000, “Carbon Dioxide Emissions from the Generation of Electric Power in the United States”, The US Energy Information Adminstration, p.2. V.K. Sharma, S. Sharma, R.A. Ray and H.P. Garg, 1968, “Design and performance studies of a solar dryer suitable for rural applications”, Energy Conversion and Management, Vol. 26, Issue 1, pp. 111-119. William S. Duff, 1975, “A methodology for selecting optimal components for solar thermal energy systems: Application to power generation, Solar Energy, Vol. 17, Issue 4, September 1975, pp. 245-254. Wu Shaopeng, Chen Mingyu and Zhang Jizhe, 2011, “Laboratory investigation into thermal response of asphalt pavements as solar collector by application of smallscale slabs”, Applied Thermal Engineering, Vol. 31, Issue 10, pp. 1582-1587.

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Wu Shuang-Ying, Lan Xiao, Yiding Cao and You-Rong Li, “Convection heat loss from cavity receiver in parabolic dish solar thermal power system: A review”, Solar Energy, In Press. Wu Shuang-Ying, Lan Xiao, Yiding Cao and You-Rong Li, 2010, “A parabolic dish/AMTEC solar thermal power system and its performance evaluation”, Applied Energy, Vol. 87, Issue 2, pp. 452-462. Wu Shuang-Ying, Lan Xiao, Yiding Cao and You-Rong Li, 2010, “Convection heat loss from cavity receiver in parabolic dish solar thermal power system: A review”, Solar Energy, Vol. 84, Issue 8, pp. 1342-1355. Yong Shuai, Xin-Lin Xia and He-Ping Tan, 2008, “Radiation performance of dish solar concentrator/cavity receiver systems”, Solar Energy, Vol. 82, Issue 1, pp. 1321. Yunus A. Cengel, 1998, “Heat Transfer: A Practical Approach”, McGraw-Hill Companies, Inc., USA. Zhigang Li, Dawei Tang, Jinglong Du and Tie Li, 2011, “Study on the radiation flux and temperature distributions of the concentrator-receiver system in a solar dish/Stirling power facility”, Applied Thermal Engineering, Vol. 31, Issue 10, pp. 1780-1789. Zhi-Sheng Li, Guo-Qiang Zhang, Dong-Mei Li, Jin Zhou, Li-Juan Li and Li-Xin Li, 2007, “Application and development of solar energy in building industry and its prospects in China”, Energy Policy, Vol. 35, Issue 8, pp. 4121-4127.

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Appendix 5.1 Angular Speed of the Sun in Azimuth Direction This appendix will show the calculations of the maximum angular speed of the sun in azimuth direction. The calculations mainly depend on the solar position which is determined by the azimuth angle and altitude angle. Those angles are calculated using solrad.xls program which was developed and is maintained by the Washington state Department of Ecology. A soft copy for the program is added in the CD of the project with the analysis (yellow highlighted sheets).

Procedure: 1) The input data to the program was entered in the input sheet as follows: Site data and time information (for the location of the solar dish in Solar Area at Sultan Qaboos University (SQU), Muscat, Oman)

Latitude in decimal degrees (positive in northern hemisphere): 23.593 Longitude in decimal degrees (negative for western hemisphere): 58.169 Ground surface elevation (m): 90.0 Time zone in hours relative to GMT/UTC (PST= -8, MST= -7, CST= -6, EST= -5): 4 Daylight savings time (no= 0, yes= 1): 0 Start date to calculate solar position and radiation: 18-May-10 Start time: 12:00 AM Time step (hours): 1 Number of days to calculate solar position and radiation: 370 2) The program was run by pressing the Excel Macro button named "run" in the input sheet. 3) After a while, the output data were generated in the output sheet. This sheet was copied to new sheet. The new sheet was organized so it contains three columns: Date and time column, Azimuth angle column and altitude angle column as in table 1. 4) When altitude angle is negative it means that this is night time. Therefore, the rows of negative altitude angle were removed in order to obtain the sun angular speed during the day.

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5) The angular speed in azimuth direction was calculated in the fourth column by subtracting the previous row azimuth angle from the present azimuth angle. This difference is the angular speed during an hour because the time difference between any two rows is one hour. 6) It is noted that azimuth angle increases as time passes from the morning to the evening. Therefore, it starts small at the beginning of the day compared to the last azimuth angle of the previous day. Therefore, the angular speed becomes negative and this negative speed is replaced by the text "new day". 7) Finally, the maximum angular speed was obtained using "Max" function (excel built-in function). The maximum speed was found in June. Accordingly, table A(5.1).1 shows the data of June only in order to save the large number of papers required to print for all months which are necessary.

Table A(5.1).1: Calculation of the maximum angular speed in azimuth direction Angular speed (deg/ hr) in Date and time Solar azimuth Solar elevation azimuth angle (deg) angle (deg) direction 1-6-2010 6:00 AM 69.21 7.66 new day 7:00 AM 74.15 20.63 4.94 8:00 AM 78.49 33.97 4.34 9:00 AM 82.56 47.52 4.07 10:00 AM 86.80 61.20 4.24 11:00 AM 92.66 74.93 5.86 12:00 PM 142.26 88.06 49.60 1:00 PM 265.80 77.27 123.54 2:00 PM 272.44 63.54 6.64 3:00 PM 276.79 49.85 4.35 4:00 PM 280.85 36.28 4.06 5:00 PM 285.13 22.91 4.28 6:00 PM 289.95 9.86 4.82 2-6-2010 6:00 AM 69.07 7.67 new day 7:00 AM 74.00 20.64 4.93 8:00 AM 78.33 33.97 4.32 9:00 AM 82.36 47.51 4.03 10:00 AM 86.52 61.18 4.16 11:00 AM 92.13 74.91 5.61 12:00 PM 138.90 88.14 46.77 1:00 PM 266.36 77.33 127.46 Solar position

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Angular speed (deg/ hr) in Date and time Solar azimuth Solar elevation azimuth angle (deg) angle (deg) direction 2:00 PM 272.72 63.60 6.36 3:00 PM 276.98 49.91 4.26 4:00 PM 281.00 36.35 4.02 5:00 PM 285.26 22.98 4.25 6:00 PM 290.06 9.94 4.80 3-6-2010 6:00 AM 68.94 7.69 new day 7:00 AM 73.86 20.65 4.92 8:00 AM 78.17 33.97 4.31 9:00 AM 82.16 47.50 4.00 10:00 AM 86.25 61.16 4.08 11:00 AM 91.63 74.90 5.38 12:00 PM 135.37 88.21 43.73 1:00 PM 266.91 77.38 131.54 2:00 PM 272.99 63.65 6.08 3:00 PM 277.16 49.97 4.17 4:00 PM 281.14 36.41 3.98 5:00 PM 285.37 23.05 4.23 6:00 PM 290.16 10.02 4.79 4-6-2010 6:00 AM 68.81 7.70 new day 7:00 AM 73.73 20.65 4.91 8:00 AM 78.02 33.96 4.29 9:00 AM 81.98 47.48 3.96 10:00 AM 85.99 61.14 4.01 11:00 AM 91.16 74.87 5.17 12:00 PM 131.69 88.27 40.54 1:00 PM 267.42 77.44 135.73 2:00 PM 273.24 63.71 5.82 3:00 PM 277.33 50.03 4.09 4:00 PM 281.27 36.48 3.94 5:00 PM 285.48 23.13 4.21 6:00 PM 290.26 10.10 4.78 5-6-2010 6:00 AM 68.69 7.71 new day 7:00 AM 73.60 20.64 4.91 8:00 AM 77.87 33.95 4.27 9:00 AM 81.80 47.47 3.93 10:00 AM 85.74 61.12 3.94 11:00 AM 90.71 74.85 4.96 12:00 PM 127.95 88.31 37.24 1:00 PM 267.91 77.49 139.97 Solar position

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Angular speed (deg/ hr) in Date and time Solar azimuth Solar elevation azimuth angle (deg) angle (deg) direction 2:00 PM 273.48 63.76 5.57 3:00 PM 277.49 50.09 4.01 4:00 PM 281.40 36.54 3.90 5:00 PM 285.59 23.20 4.19 6:00 PM 290.35 10.17 4.76 6-6-2010 6:00 AM 68.57 7.71 new day 7:00 AM 73.47 20.64 4.90 8:00 AM 77.73 33.93 4.26 9:00 AM 81.64 47.45 3.90 10:00 AM 85.51 61.10 3.88 11:00 AM 90.28 74.82 4.77 12:00 PM 124.18 88.34 33.90 1:00 PM 268.38 77.55 144.19 2:00 PM 273.71 63.82 5.33 3:00 PM 277.64 50.15 3.94 4:00 PM 281.51 36.61 3.87 5:00 PM 285.68 23.27 4.17 6:00 PM 290.43 10.25 4.75 7-6-2010 6:00 AM 68.46 7.71 new day 7:00 AM 73.36 20.63 4.89 8:00 AM 77.60 33.92 4.25 9:00 AM 81.48 47.42 3.87 10:00 AM 85.30 61.07 3.82 11:00 AM 89.89 74.79 4.59 12:00 PM 120.48 88.36 30.59 1:00 PM 268.81 77.60 148.33 2:00 PM 273.92 63.87 5.10 3:00 PM 277.79 50.21 3.87 4:00 PM 281.62 36.67 3.84 5:00 PM 285.77 23.34 4.15 6:00 PM 290.51 10.32 4.74 8-6-2010 6:00 AM 68.36 7.70 new day 7:00 AM 73.25 20.62 4.89 8:00 AM 77.48 33.90 4.23 9:00 AM 81.33 47.40 3.85 10:00 AM 85.09 61.04 3.76 11:00 AM 89.51 74.76 4.42 12:00 PM 116.89 88.37 27.38 1:00 PM 269.22 77.66 152.33 Solar position

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Angular speed (deg/ hr) in Date and time Solar azimuth Solar elevation azimuth angle (deg) angle (deg) direction 2:00 PM 274.11 63.93 4.89 3:00 PM 277.92 50.27 3.80 4:00 PM 281.72 36.74 3.80 5:00 PM 285.85 23.40 4.13 6:00 PM 290.58 10.40 4.73 9-6-2010 6:00 AM 68.26 7.70 new day 7:00 AM 73.14 20.60 4.88 8:00 AM 77.37 33.88 4.22 9:00 AM 81.19 47.37 3.83 10:00 AM 84.90 61.00 3.71 11:00 AM 89.17 74.72 4.27 12:00 PM 113.49 88.36 24.32 1:00 PM 269.60 77.71 156.11 2:00 PM 274.29 63.98 4.69 3:00 PM 278.04 50.33 3.74 4:00 PM 281.81 36.80 3.78 5:00 PM 285.93 23.47 4.12 6:00 PM 290.65 10.47 4.72 10-6-2010 6:00 AM 68.17 7.69 new day 7:00 AM 73.05 20.58 4.88 8:00 AM 77.26 33.85 4.21 9:00 AM 81.06 47.34 3.80 10:00 AM 84.73 60.97 3.66 11:00 AM 88.85 74.68 4.13 12:00 PM 110.31 88.35 21.46 1:00 PM 269.95 77.76 159.64 2:00 PM 274.46 64.04 4.51 3:00 PM 278.15 50.39 3.69 4:00 PM 281.89 36.86 3.75 5:00 PM 285.99 23.54 4.10 6:00 PM 290.70 10.54 4.71 11-6-2010 6:00 AM 68.08 7.67 new day 7:00 AM 72.96 20.56 4.88 8:00 AM 77.16 33.82 4.20 9:00 AM 80.94 47.31 3.78 10:00 AM 84.56 60.93 3.62 11:00 AM 88.56 74.65 4.00 12:00 PM 107.40 88.33 18.84 1:00 PM 270.27 77.81 162.87 Solar position

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Angular speed (deg/ hr) in Date and time Solar azimuth Solar elevation azimuth angle (deg) angle (deg) direction 2:00 PM 274.61 64.09 4.34 3:00 PM 278.24 50.44 3.63 4:00 PM 281.97 36.92 3.72 5:00 PM 286.05 23.60 4.09 6:00 PM 290.75 10.61 4.70 12-6-2010 6:00 AM 68.00 7.66 new day 7:00 AM 72.87 20.54 4.87 8:00 AM 77.07 33.79 4.19 9:00 AM 80.83 47.27 3.77 10:00 AM 84.41 60.90 3.58 11:00 AM 88.29 74.61 3.88 12:00 PM 104.78 88.31 16.48 1:00 PM 270.57 77.87 165.79 2:00 PM 274.75 64.15 4.18 3:00 PM 278.33 50.50 3.59 4:00 PM 282.03 36.98 3.70 5:00 PM 286.11 23.67 4.07 6:00 PM 290.80 10.68 4.69 13-6-2010 6:00 AM 67.92 7.64 new day 7:00 AM 72.79 20.51 4.87 8:00 AM 76.98 33.76 4.19 9:00 AM 80.73 47.24 3.75 10:00 AM 84.28 60.86 3.55 11:00 AM 88.05 74.56 3.78 12:00 PM 102.45 88.28 14.40 1:00 PM 270.83 77.92 168.38 2:00 PM 274.87 64.20 4.04 3:00 PM 278.41 50.56 3.54 4:00 PM 282.09 37.04 3.68 5:00 PM 286.15 23.73 4.06 6:00 PM 290.83 10.74 4.68 14-6-2010 6:00 AM 67.85 7.61 new day 7:00 AM 72.72 20.48 4.87 8:00 AM 76.91 33.73 4.18 9:00 AM 80.64 47.20 3.74 10:00 AM 84.16 60.82 3.52 11:00 AM 87.84 74.52 3.68 12:00 PM 100.43 88.24 12.59 1:00 PM 271.06 77.97 170.63 Solar position

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Angular speed (deg/ hr) in Date and time Solar azimuth Solar elevation azimuth angle (deg) angle (deg) direction 2:00 PM 274.98 64.25 3.91 3:00 PM 278.48 50.61 3.50 4:00 PM 282.14 37.10 3.66 5:00 PM 286.19 23.79 4.05 6:00 PM 290.86 10.80 4.67 15-6-2010 6:00 AM 67.79 7.59 new day 7:00 AM 72.66 20.45 4.87 8:00 AM 76.84 33.69 4.18 9:00 AM 80.56 47.16 3.73 10:00 AM 84.05 60.77 3.49 11:00 AM 87.66 74.47 3.60 12:00 PM 98.70 88.20 11.04 1:00 PM 271.26 78.02 172.56 2:00 PM 275.07 64.31 3.80 3:00 PM 278.54 50.67 3.47 4:00 PM 282.18 37.16 3.65 5:00 PM 286.22 23.85 4.04 6:00 PM 290.89 10.86 4.67 16-6-2010 6:00 AM 67.73 7.56 new day 7:00 AM 72.60 20.42 4.87 8:00 AM 76.78 33.65 4.17 9:00 AM 80.49 47.12 3.72 10:00 AM 83.96 60.73 3.47 11:00 AM 87.50 74.43 3.54 12:00 PM 97.26 88.16 9.76 1:00 PM 271.43 78.07 174.18 2:00 PM 275.14 64.36 3.71 3:00 PM 278.58 50.72 3.44 4:00 PM 282.21 37.21 3.63 5:00 PM 286.25 23.91 4.03 6:00 PM 290.91 10.92 4.66 17-6-2010 6:00 AM 67.68 7.52 new day 7:00 AM 72.55 20.38 4.87 8:00 AM 76.72 33.61 4.17 9:00 AM 80.43 47.08 3.71 10:00 AM 83.88 60.68 3.45 11:00 AM 87.36 74.38 3.48 12:00 PM 96.09 88.11 8.72 1:00 PM 271.57 78.13 175.49 Solar position

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Angular speed (deg/ hr) in Date and time Solar azimuth Solar elevation azimuth angle (deg) angle (deg) direction 2:00 PM 275.20 64.41 3.63 3:00 PM 278.62 50.78 3.42 4:00 PM 282.24 37.27 3.62 5:00 PM 286.26 23.96 4.02 6:00 PM 290.92 10.98 4.65 18-6-2010 6:00 AM 67.64 7.49 new day 7:00 AM 72.51 20.34 4.87 8:00 AM 76.68 33.57 4.17 9:00 AM 80.38 47.03 3.70 10:00 AM 83.82 60.64 3.44 11:00 AM 87.26 74.33 3.44 12:00 PM 95.17 88.07 7.91 1:00 PM 271.68 78.18 176.51 2:00 PM 275.25 64.47 3.57 3:00 PM 278.65 50.83 3.40 4:00 PM 282.25 37.32 3.61 5:00 PM 286.27 24.02 4.02 6:00 PM 290.92 11.03 4.65 19-6-2010 6:00 AM 67.60 7.45 new day 7:00 AM 72.47 20.30 4.87 8:00 AM 76.64 33.53 4.17 9:00 AM 80.34 46.99 3.70 10:00 AM 83.77 60.59 3.43 11:00 AM 87.18 74.29 3.41 12:00 PM 94.49 88.02 7.32 1:00 PM 271.75 78.23 177.26 2:00 PM 275.27 64.52 3.53 3:00 PM 278.66 50.88 3.38 4:00 PM 282.26 37.37 3.60 5:00 PM 286.27 24.07 4.01 6:00 PM 290.92 11.09 4.64 20-6-2010 6:00 AM 67.57 7.41 new day 7:00 AM 72.45 20.26 4.88 8:00 AM 76.61 33.48 4.17 9:00 AM 80.31 46.94 3.70 10:00 AM 83.73 60.54 3.42 11:00 AM 87.12 74.24 3.39 12:00 PM 94.04 87.97 6.92 1:00 PM 271.79 78.28 177.75 Solar position

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Angular speed (deg/ hr) in Date and time Solar azimuth Solar elevation azimuth angle (deg) angle (deg) direction 2:00 PM 275.29 64.57 3.50 3:00 PM 278.66 50.93 3.38 4:00 PM 282.26 37.43 3.60 5:00 PM 286.27 24.12 4.01 6:00 PM 290.91 11.14 4.64 21-6-2010 6:00 AM 67.54 7.37 new day 7:00 AM 72.42 20.21 4.88 8:00 AM 76.59 33.44 4.17 9:00 AM 80.29 46.89 3.70 10:00 AM 83.71 60.49 3.42 11:00 AM 87.09 74.19 3.38 12:00 PM 93.80 87.92 6.71 1:00 PM 271.80 78.33 177.99 2:00 PM 275.28 64.62 3.49 3:00 PM 278.66 50.98 3.37 4:00 PM 282.25 37.48 3.59 5:00 PM 286.26 24.17 4.01 6:00 PM 290.89 11.18 4.64 22-6-2010 6:00 AM 67.53 7.32 new day 7:00 AM 72.41 20.16 4.88 8:00 AM 76.58 33.39 4.17 9:00 AM 80.28 46.84 3.70 10:00 AM 83.70 60.44 3.42 11:00 AM 87.08 74.14 3.38 12:00 PM 93.76 87.87 6.67 1:00 PM 271.77 78.38 178.01 2:00 PM 275.27 64.67 3.50 3:00 PM 278.64 51.03 3.37 4:00 PM 282.23 37.52 3.59 5:00 PM 286.24 24.22 4.00 6:00 PM 290.87 11.23 4.63 23-6-2010 6:00 AM 67.51 7.27 new day 7:00 AM 72.40 20.11 4.89 8:00 AM 76.58 33.34 4.18 9:00 AM 80.28 46.79 3.70 10:00 AM 83.71 60.39 3.43 11:00 AM 87.10 74.09 3.40 12:00 PM 93.90 87.82 6.79 1:00 PM 271.71 78.43 177.81 Solar position

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Angular speed (deg/ hr) in Date and time Solar azimuth Solar elevation azimuth angle (deg) angle (deg) direction 2:00 PM 275.23 64.72 3.52 3:00 PM 278.61 51.08 3.38 4:00 PM 282.21 37.57 3.60 5:00 PM 286.21 24.26 4.00 6:00 PM 290.84 11.27 4.63 24-6-2010 6:00 AM 67.51 7.22 new day 7:00 AM 72.40 20.06 4.89 8:00 AM 76.58 33.29 4.18 9:00 AM 80.29 46.74 3.71 10:00 AM 83.73 60.34 3.44 11:00 AM 87.15 74.04 3.42 12:00 PM 94.20 87.77 7.06 1:00 PM 271.61 78.48 177.40 2:00 PM 275.18 64.76 3.57 3:00 PM 278.57 51.12 3.39 4:00 PM 282.17 37.61 3.60 5:00 PM 286.18 24.30 4.01 6:00 PM 290.81 11.31 4.63 25-6-2010 6:00 AM 67.51 7.17 new day 7:00 AM 72.40 20.01 4.90 8:00 AM 76.59 33.23 4.19 9:00 AM 80.31 46.69 3.72 10:00 AM 83.76 60.29 3.45 11:00 AM 87.22 73.99 3.46 12:00 PM 94.67 87.72 7.45 1:00 PM 271.48 78.52 176.81 2:00 PM 275.11 64.81 3.63 3:00 PM 278.52 51.17 3.41 4:00 PM 282.13 37.66 3.61 5:00 PM 286.14 24.34 4.01 6:00 PM 290.76 11.35 4.63 26-6-2010 6:00 AM 67.52 7.12 new day 7:00 AM 72.42 19.95 4.90 8:00 AM 76.61 33.18 4.19 9:00 AM 80.34 46.63 3.73 10:00 AM 83.81 60.24 3.47 11:00 AM 87.31 73.94 3.51 12:00 PM 95.29 87.67 7.97 1:00 PM 271.31 78.57 176.02 Solar position

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Angular speed (deg/ hr) in Date and time Solar azimuth Solar elevation azimuth angle (deg) angle (deg) direction 2:00 PM 275.03 64.85 3.72 3:00 PM 278.46 51.21 3.43 4:00 PM 282.08 37.70 3.62 5:00 PM 286.09 24.38 4.01 6:00 PM 290.72 11.38 4.63 27-6-2010 6:00 AM 67.53 7.06 new day 7:00 AM 72.44 19.90 4.91 8:00 AM 76.64 33.12 4.20 9:00 AM 80.38 46.58 3.74 10:00 AM 83.87 60.19 3.49 11:00 AM 87.43 73.88 3.56 12:00 PM 96.04 87.62 8.61 1:00 PM 271.11 78.61 175.07 2:00 PM 274.93 64.90 3.82 3:00 PM 278.39 51.25 3.46 4:00 PM 282.02 37.73 3.63 5:00 PM 286.03 24.41 4.02 6:00 PM 290.66 11.41 4.63 28-6-2010 6:00 AM 67.55 7.00 new day 7:00 AM 72.46 19.84 4.91 8:00 AM 76.67 33.07 4.21 9:00 AM 80.43 46.53 3.75 10:00 AM 83.94 60.14 3.51 11:00 AM 87.57 73.83 3.63 12:00 PM 96.92 87.56 9.35 1:00 PM 270.87 78.66 173.95 2:00 PM 274.81 64.94 3.95 3:00 PM 278.31 51.29 3.49 4:00 PM 281.95 37.77 3.64 5:00 PM 285.97 24.45 4.02 6:00 PM 290.60 11.44 4.63 29-6-2010 6:00 AM 67.58 6.94 new day 7:00 AM 72.50 19.78 4.92 8:00 AM 76.72 33.01 4.22 9:00 AM 80.48 46.47 3.77 10:00 AM 84.03 60.08 3.54 11:00 AM 87.74 73.78 3.71 12:00 PM 97.92 87.51 10.18 1:00 PM 270.59 78.70 172.68 Solar position

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Angular speed (deg/ hr) in Date and time Solar azimuth Solar elevation azimuth angle (deg) angle (deg) direction 2:00 PM 274.68 64.98 4.09 3:00 PM 278.21 51.33 3.53 4:00 PM 281.87 37.81 3.66 5:00 PM 285.90 24.48 4.03 6:00 PM 290.54 11.46 4.63 30-6-2010 6:00 AM 67.61 6.88 new day 7:00 AM 72.54 19.72 4.93 8:00 AM 76.77 32.95 4.23 9:00 AM 80.55 46.42 3.78 10:00 AM 84.13 60.03 3.58 11:00 AM 87.93 73.73 3.80 12:00 PM 99.03 87.45 11.10 1:00 PM 270.28 78.74 171.25 2:00 PM 274.53 65.02 4.25 3:00 PM 278.11 51.37 3.58 4:00 PM 281.79 37.84 3.68 5:00 PM 285.83 24.50 4.04 6:00 PM 290.46 11.48 4.64 Maximum Speed 178.01 Solar position

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Appendix 8.1 Global radiation and sunshine duration Table A(8.1).1: Global radiation and sunshine duration Year Mean Global radiation (W/sq.m) 2002 2003 2004

650.9 635.5 644.1

Averages

643.5

Mean sunshine duration (hr) 9.7 8.8 7.5 8 2�3

Location: Muscat at latitude: 23 35 43.4 N and longitude: 58 17 44.3 E (14 m elevation). Reference: Directorate General of Civil Aviation and Meteorology (Oman)

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Appendix 8.2 Average temperatures in Muscat (Seeb) Table A(8.2).1: Average temperatures in Muscat (Seeb) Average Temperature ̊ C Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Daily Daily Minimum Maximum 16.7 25.1 17.8 26.4 20.3 29.5 24.2 34.7 28.7 39.6 30.3 40 30.1 38 28.2 35.6 26.8 35.6 24.2 34.6 20.8 30.3 18.3 26.8 Average

Daily Average 20.9 22.1 24.9 29.45 34.15 35.15 34.05 31.9 31.2 29.4 25.55 22.55 28.4

Reference: http://worldweather.wmo.int/030/c00112.htm Directorate General of Civil Aviation and Meteorology (Oman) Note: the temperatures are high in the months: May, June and July and therefore water heating is not required.

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