بسم اهللا الرحمن الرحيمUNIVERSITY OF KHARTOUM

INSTITUTE OF ENVIRONMENTAL STUDIES

Architectural Integration of Solar Energy Applications With Buildings Special References to Buildings in Khartoum, Sudan A study submitted in partial Fulfillment of the requirements for the Master Degree in Environmental Studies Maha Babiker Hassan February 2004

List of Contents

List of Contents I List of Figures III List of Photographs III List of Tables IV Acknowledgements V Abstract VI Abstract in Arabic VII

Chapter 1: Introductory Chapter 1 1.1- introduction 1 1.2- The Research Problem 1 1.3- The Objectives of the Study 2 1.4- The Methodology of the Study 2 1.5- The Structure of the Study 3

Chapter 2: Solar Technology 4 2-1- Introduction 4 2-2- Solar Thermal Energy 6

2-2-1-Hisorical Background of Solar Thermal Energy 6 2-2-2- Solar Radiation Collectors 6

A-Flat Plate Collectors 7 B-Solar Concentrating Collectors 8 C-Solar evacuated Collectors 9

2-3- Solar Thermal Applications 10 2-3-1-Solar Water Heating 10

A-Needs for Domestic uses 11 B- Needs for Industry 12 C- Needs for Service Buildings 12

2-3-2-Solar Refrigeration and Air Conditioning 13 Cooling Needs 14

2-3-3-Solar Drying 14 Needs for Solar Drying 15

2-3-4-Solar Distillation 15 2-4- Solar Photovoltaics 16

2-4-1-Hisorical Background of Photovoltaics 16 2-4-2- Forms 16 2.4.3- Photovoltaic System Components 17 2.4.4- Photovoltaic Systems 18 2.4.5- Photovoltaic needs 18

2-5- The Main Areas of Concern 19 2-6- Solar Collectors and PVs Orientation 19 2-7- Factors that affect the Performance of Solar

Collectors and PVs 19

2.8- Environmental impact 20 2.9- Visual impact 20 2.10- Summary 20

Chapter 3: Context 21 3-1-Sudan 21 3-2-Sudan Climate 21 3- 3-Khartoum Climate 22 3-4-Design Principles in a Hot Dry Climate 23 3-5-Energy Situation in Sudan 25 3-6-Solar Energy in Sudan 26 3-7- Summary 31

Chapter 4: Solar Technology and Buildings 32 4-1-Building Design 32 4-2- Approaches of Solar Energy to Buildings 33

4-2-1-Passive Design System 33 4-2-2-Active Design System 33

4-3- Integration of Solar Systems with Buildings 34 4-4- Integration Options 35

4-4-1-Integration within Building 35

4-2-2- Integration within Site 37 4-5- Summary 37

Chapter 5: Sudan Solar Technology 38

5-1-Introduction 38 5-2-Applications of Solar Panels in Sudan 38 5-3-Solar Applications Industry in Sudan 39 5-4- Examples from Sudan 40

5-4-1-Sudatel 40 5-4-2-Rural electrification 40

5-5- The study 42 5-5-1- Approaches to integration study 42

A-solar applications 42 B-Buildings 43

5-5-2- factors that determine integration options 46 5-6- Case Studies 47

5-6-1-Houses group 1 49 5-6-2-Houses group 2 51 5-6-3-Houses group 3 53 5-6-4-Industrial buildings 55 5-6-5-Office buildings 57

5-7- Summary 59

Chapter 6: Conclusions and Recommendations 60 6-1-Introduction 60 6-2- Basic Recommendations for Solar Panels Mounting 60 6-3- Guideline for Building Integrated Solar Applications 61 6-4- General Guides 61 6-5- Further Studies 62 6-6- Concluding remarks 62

References 63

Appendices 65

List of Figures:

Fig. (1) Absorption and Reflection of Solar Radiation by the Atmosphere 4

Fig. (2) Direct Conversion of Solar Energy 5

Fig. (3) Flat Plate Collector Components 7

Fig. (4) Cross-Sectional View of a Hemispherical Mirror Concentrator 8

Fig. (5) Evacuated Tube Components 9

Fig. (6) Schematic Drawing of A Forced Circulation Solar Water Heating

System

11

Fig. (7) Conceptual Relationship between the PV Cell, Module and Array 16

Fig. (8) Grid Connected PV System Components 17

Fig. (9) Sudan Location 21

Fig. (10) Annual Global Irradiance on a Horizontal Plane at the Surface of the

Earth

26

Fig. (11) Monthly Mean Global Solar Radiation (MJ/M²)for Summer in Sudan 27

Fig. (12) Monthly Mean Global Solar Radiation (MJ/M²)for Winter in Sudan 28

Fig. (13) Shading Effects by Neighbouring Buildings 34

Fig. (14) Different Alternatives Of Roof Integration 35

Fig. (15) Different Alternatives Of Facade Integration 36

Fig. (16) Different Alternatives Of Sunshades Integration 37

Fig. (17) Solar System Components 42

Fig. (18) A Simple Way of Panels Fixation 43

Fig. (19) Pvs Fixed in Wall 43

Fig. (20) Integration Process 45

Fig. (21) Determination of Integration Option 46

Fig. (22) Section through a Traditional Roof 49

Fig. (23) Suggested Options of Integration 49

Fig. (24) Solar Panels Mounted on Rooftop 51

Fig. (25) Mounting of Solar Panel on Veranda’s Roof 51

Fig. (26) Ventilated Air Space between the Roof and Panels 52

Fig. (27) Different Configurations of Industrial Buildings Roofs 55

Fig. (28) Different Alternatives of Monitoring Roof 56

Fig. (29) Effect of Surrounding Buildings 58

List of Photographs:

Photo.(1) Flat Plate Collector 7

Photo(2) Parabolic Trough System 8

Photo(3) Evacuated Tube Collector 10

Photo(4) Sample of a Local Solar Water Heater 10

Photo(5,6) Water Boiler 12

Photo(7) Water Heating Apparatus 12

Photo(8) Sample of a Local Solar Dryer 15

Photo(9) Photovoltaic Array 16

Photo(10) Most Common View, Charcoal market, in the City of Khartoum,

Located at the Middle of an Open Space within a Neighbourhood

25

Photo(11,12) Roof Integrated Solar Panels 35

Photo(13,14) Façade Integrated Solar Panels 36

Photo(15) Solar Panel Mounted at the Top of a Building 39

Photo(16) Solar Panels Mounted Outdoor 39

Photo(17,18) Use of PVs in Schools in Kordofan State 41

Photo(19) Solar Water Pumping 41

Photo(20) A Simple Way of Panels Fixation 43

Photo(21) First Group of Houses 47

Photo(22) Second Group of Houses 48

Photo(23) Third Group of Houses 48

Photo(24) Solar Panels Mounted on Rooftop 51

Photo(25) Example of Second Group of Houses 51

Photo(26) Mounting of Solar Panels on Rooftop 53

Photo(27) Example of Third Group of Houses 53

Photo(28) Integration of Solar Panel As Integral Part Of Roof 53

Photo(29, 30) Office Buildings In Khartoum 57

List of Tables:

Table

(1)

Hourly Values of Air Temperature Represented in Khartoum by the

21st day of each Month in the Year

23

Table

(2)

Monthly Mean of Daily Sunshine Hours/ Percentage in day for 23

Meteorological Stations (1961-1990) in Sudan

29

Table

(3)

Monthly Mean of Daily Global Solar Radiation (MJ/m²/day) for 15 Metrological Stations (1961-1990) in Sudan

30

Table

(4)

Different Types of Buildings, Materials Used and Construction Techniques in Sudan

44

Acknowledgements

I would like to express my deep gratitude and sincere appreciation to my supervisor Dr. Osman M. Elkheir for his continuous interest, encouragement, patience and genuine guidance throughout the dissertation work. Special thanks for, Dr. Salih Hamadtto and Dr. Hassan Wardi for giving generously of their time in providing information. Thanks are extended to Mr. Nor Allah, in the Swedish Free Mission for providing information about existing projects in Sudan. I would also like to thank the staff in the solar energy department, Energy Research Centre, Khartoum.

My deepest thanks to my friend Wisal B. Hamour, for her help and encouragement during work. I would also like to thank Dr. Wiam and Miss Khalda for their help. Sincere thanks to my family members for great patience and encouragement.

Finally my thanks are extended to every person who helped me through my dissertation work. Above all my special and unlimited thanks are to God.

Abstract

In recent years, there was an improvement in utilizing solar energy and using solar applications in Sudan. This improvement requires

awareness of using this technology and collaboration among all people who have been involved in this process.

In this study, an attempt is made to architecturally incorporate of solar applications with different buildings in Sudan. Mounting of solar applications within buildings in Sudan is not according to any architectural standards. That, therefore, led to losses of its appearance within buildings. Special emphasis on buildings in Khartoum has been made. Samples from different types of buildings have been chosen as a case study, and have been analyzed to indicate how these buildings accept this technology and to study the architectural value of this integration. In addition to that, conclusions and recommendations for buildings integrated solar applications have been made, together with some guidelines for further studies. The goal is to have the solar building.

الخالصة

واستخدام في االستفادة من الطاقة الشمسية املحوظ، هنالك تطور األخيرة األعوامفي التطور يحتاج لدراسة ووعي في استعمال هذه هذا. التطبيقات الشمسية في السودان

.التقنية، هذا باإلضافة للتعاون التام بين آل األشخاص المتضمنين في العملية

األنواعالتطبيقات الشمسية معماريا مع تكامل ة لدراسمحاولة هنالك ،األطروحةفي هذه عملية ترآيب التطبيقات الشمسية في من المالحظ أن . في السودانالمختلفة من المباني

. ال تستند علي أي معايير معمارية مما يؤثر علي جماليات المبني في السودانالمباني

ومن . في مدينة الخرطوم آحالة دراسة المختلفة من المباني األنواع تم اختيار عينة من تلك إلضافة تحليل قابلية تلك المباني الستيعاب هذه التقنية مع دراسة القيمة المعمارية ثم

بعض التوصيات لعملية تكامل التطبيقات الشمسية مع مع وضع ،التطبيقات للمباني .للمبني الشمسي للوصول والتوجيه لدراسات مستقبليةالمباني

CHAPTER 1 INTRODUCTORY CHAPTER 1.1- Introduction

Energy is an essential factor in subsistence and development. Energy demand is, therefore, rapidly increasing year by year. Limited energy sources and growing environment pollution led to intensive search for alternatives of energy sources. Recently there were more trends towards renewable energy sources (solar energy, wind energy, biomass energy, etc) that satisfy world’s need of energy. Theoretically the global supply of energy from such renewable energy sources by far exceeds the earth’s present total energy demand. On the other hand, renewable energy sources make good enhancement to environmental protection activities –no fumes, no emission of pollutant substances that affect environment. Chapter nine of Agenda 21 goes on to make a key statement on energy: "Energy use is a major source of emissions. The use of energy is essential to economic and social development and improved quality of life. Much of the world’s energy, however, is produced and consumed in ways that cannot be sustained if overall quantities increase substantially. Controlling emissions will depend on greater efficiency in energy production, transmission, distribution and consumption, and on creating environmentally sound energy systems". (UNCED, 1993). Renewable energy can be the best energy system specially in developing countries that spend most of hard currency earnings to import oil and that suffer from acute shortages of energy, despite the fact that most of the developing countries are close to the tropical region which enjoys, even in the rainy season, hours of bright sunshine. Solar energy can, therefore, be a good source of energy. Solar energy systems proved to be most appropriate to many energy supply problems especially in rural areas, which are not supported by the required services (pump water for village; operate vaccine refrigerators in health centers, etc).

1.2-The Research Problem

In the third world in general, and in Sudan in particular, the development of infra-structure is far behind the growth of urbanization, while the rural areas are not supported by required services. There is, therefore, a shortage of energy. The depleting sources such as natural oil, gas, etc are expensive and harmful to the environment, at the same time; do not satisfy the energy needs. Renewable sources such as solar energy, wind energy, etc can meet some of the energy demand. Last years, Sudan began to exploit the solar energy. There are several of solar energy applications which have been carried out (solar lighting systems, solar water heating, solar refrigeration, solar cold stores, solar crop dryers, etc). Methods of fixation and mounting of solar applications in Sudan is not according to any architectural standards and they sometimes negatively contribute to buildings appearance. Aesthetics and architectural integration are important factors in public perception and acceptance of solar technology. In Europe, great efforts are given for the incorporation of solar applications especially PVs in the structure of a building. Many of buildings are using solar applications as roof, façade and sunshades'; buildings integrated solar panels are becoming popular. The problem of the research concerns the study of solar energy applications as an integral part of the architectural design of buildings in general, with special references to buildings in Khartoum, in addition to the acceptance of Sudanese buildings to the facilities of solar energy. How to make this is a major concern of this research in which there is an attempt to outline guidelines for further study. This requires awareness of different approaches in Sudanese building designs and different types of buildings in Khartoum.

1.3 -The Objectives of the Study

The objective is to study and identify the possibility of architectural integration of solar energy appliances with buildings in Sudan focusing on Khartoum. Moreover, study of the effect and advantages of using solar applications as an integral part of buildings. This requires the definition of these appliances, their components, performance and efficiency and problems that cause inefficiencies. As well, it is important to study Sudan location and climate, Khartoum climate, in addition to the energy situation in the Sudan in particular solar energy. Design principles in hot-dry climates also, approaches of solar energy within a building and the different options of integration are to be reviewed and considered.

1. 4-The Methodology of the Study

The methodology of the research is literature review and cases study. This is done by collection of data from textbooks, periodicals, conference papers, etc, and the study, analysis and synthesis of data. Another method is interviews with experts in the area of study, as well as field observations and photographs taken for some appliances and different locations to show installation of these applications in different buildings.

1.5-The Structure of the Study The second chapter is about the solar technology. This part is an overview of solar energy sources, and is followed by a brief description of the solar thermal technology, different types of solar collectors and different thermal applications, then, solar photovoltaics form, components and systems. The last part of this chapter highlights the main areas of concern, panels orientation, factors that affect solar systems and visual and environmental impact of using solar systems. The third chapter describes Sudan location and climate, in addition to Khartoum climate. Follows that, an overview of building designs and the principles of design in hot dry climates. Energy situation in Sudan and solar energy in Sudan are briefly discussed.

Fourth and fifth chapters are the main part of the study. In the fourth chapter different approaches of solar energy to buildings, the integration of building with solar applications and integration options were presented. The fifth chapter, discusses Sudan solar technology, and examines the integration of solar applications with different buildings in Khartoum by choosing examples from different types as a case study. The chapter also throws light on application of solar panels and solar industry in Sudan. In this chapter there are some examples of application of solar technology in Sudan. The last chapter highlights some guidelines and recommendations for the buildings integrated solar applications.

CHAPTER 2 SOLAR TECHNOLOGY 2.1- Introduction

The sun is a completely gaseous body composed mainly of hydrogen. Hankins pointed that; the sun is the earth’s nearest star and the source of virtually all the earth’s energy, producing 3.8x10²³ KW of power in huge nuclear fusion reaction. Most of this power is lost in space, but the tiny fraction that does reach earth, 1.73x106 KW, is thousands times more than enough to provide all of our energy needs (Hankins, 1995). According to Eltom, the solar energy falling just on the land surface of the earth each year equals about 4 times the total estimated fossil fuel reserve, and about 4 thousands times the current humanity’s global energy consumption (Eltom, 1998). Solar radiation is an inexhaustible source of energy. Solar energy is considered as the main source of renewable energy, as well as conventional energy. The solar energy received at the outer frontier of the earth’s atmosphere is equivalent to 1.35KW/m2, a value known as a solar constant (fig.1).

1000 W/m2

21350 W/mRadiation arrived

the atmosphere

Radiation reflectedby clouds

Diffused radiation

Direct radiation

by airRadiation absorbed

Fig. (1): Absorption and Reflection of Solar Radiation by the Atmosphere Source: Hankins M., 1995

Solar radiation is divided into: direct radiation – incident direct from the sun. Diffused radiation - incident from all directions after scattering by the atmosphere, and it increases by increasing of dust, clouds and air molecules. The efficient use of solar energy requires knowledge of the solar energy amount available at any one place for a certain period of time. This requires a considerable amount of data about the various elements of solar radiation and their spatial and time variation. The following elements of solar radiation are the most commonly used in solar energy applications:

- The monthly mean of daily sunshine duration. - The monthly mean of daily global radiation. - The monthly mean of daily diffuse and direct radiation and their variation through the year.

To make use of solar radiation we must convert it into a form that is of use. Solar energy can be directly transformed into three useful forms: chemical, heat or electrical energy (fig. 2). Solar chemical: green plants transform solar energy into chemical energy in sugar or cellulose by the process called photosynthesis that remains a secret of plants. Solar electrical: solar electrical devices transform solar energy into electricity by using solar cells – photovoltaic-for lighting, powering, radio, TV, pumping water, etc. Solar heat: solar heating devices transform solar energy into heat by using solar collectors – for drying, water heating, cooking, generation of steam and distilling water, etc.

photosynthesisby

conversion conversion

by

conversion

by

Thermal Electrical

collectors photovoltaics

Chemical

Solar Energy Conversion

Fig. (2): Direct Conversion of Solar Energy The scope of this study is the direct conversion of solar energy into thermal and electrical energy; hence, the review will be given to literature relating to it, because:

- Their applications have a direct contact with buildings. - They are environmentally friendly sources of energy - Use of solar applications especially photovoltaic in Sudan is in continual growth, and more increase is expected after the decreasing on customs of solar panels.

From the world solar programme 1996-2005, part of the high priority national projects of the UNESCO in the Sudan are the solar home system, vaccine refrigerators, photovoltaic and wind pump systems project, radio power systems, solar energy resource assessment and establishing solar information system, solar cooking stove dissemination project and solar passive cooling.

2.2- Solar Thermal Energy The thermal process can be used to provide thermal energy. This means the conversion of energy coming from the sun in the form of radiation into a form of heat. This heat is used for many applications. Energy from the sun is collected via solar thermal collectors.

2.2.1- Historical Background of Solar Thermal Energy1

1 a1999/solar/407ES/courses/au.edu.uwa.mech.www/ htm. physics

The concept of solar thermal energy had only started in 1767 when the Swiss scientist Horace de Saussure invented the world's first solar collector, or "hot box" which was used to cook food. The use of solar thermal energy in water heating started in 1891 when the first commercial water heater was patented in America Solar water heating technology was widely used during the years of high-energy prices in the 1970's and continues to be popular around the world. Solar heat can be used to produce steam to drive a turbine and produce electricity. Solar thermal electricity is cost-competitive when carried out in large economies of scales. The first commercial applications of this technology appeared in the early 1980's, and the industry grew very rapidly. For example, today, utilities in the U.S. have installed more than 400 megawatts of solar thermal generating capacity, providing electricity to thousands of homes and businesses.

2.2.2- Solar Radiation Collectors The most important part of this system is the collectors. The solar collector is a special kind of heat exchanger that transfers the radiant energy of incident solar radiation into sensible heat of a working fluid – liquid or air. The principal usually followed is to expose a dark surface to solar radiation so that the radiation is absorbed. A part of the absorbed radiation is then transferred to a fluid like air or water. Usually the collector consists of an absorber plate on which the solar radiation falls after coming through a transparent cover. The absorbed radiation is partly transferred to the fluid and the remaining part of the radiation absorbed in the absorber plate is lost by convection and re-radiation to the surroundings. The transparent covers help in reducing the losses by convection and re-radiation while thermal insulation on the backsides and the edges helps in reducing the conduction heat losses (Eltom.1998).

In other words, solar collectors work according to greenhouse effect to generate heat and electromagnetic radiation penetrates the collector and is absorbed by the surface inside the collector. Once radiation is absorbed within the collector, the temperature rises and generates heat. Several kinds of solar collectors differ in respects to heat exchangers.

A/ Flat Plate Collectors A flat plate collector is basically a heat exchanger, which transfers the radiant energy of the incident sunlight to sensible heat of a working fluid – liquid or air. The flat plate collector is designed for operation in a low temperature range (ambient 60°C) or in the medium temperature range (ambient 100°C).

Photo. (1): Flat Plate Collector Source: www.fsec.ucf.edu/solar/images/sponroof.jpg The flat plate collector is usually planted on the top of the building, and it can be installed as a large flat array at a top of a sloping roof or mounted on the ground. Flat plate collectors are basically divided into two categories according to their use, water or liquid heaters and air heaters (Tawari, 2002 – p. 94).

Solar/Solaire - G lazed flat-plate collector / C apteur plan de ty pe v itré

Fig. (3): Flat Plate Collector Components Source: www.flasolar.com/solar.wtr-main.htm Essentially the majority of flat plate collectors consist of several basic elements (fig. 3):

- A flat absorbing plate, normally metallic, upon which the short wave solar radiation falls and is absorbed;

- Tubes, channels or passages attached to the absorber plate to circulate the liquid required to remove the thermal energy from the plate;

- Thermal insulation provided at the back and sides of the absorber plate to minimize the heat loses;

- Transparent cover (one or two sheets of glass or transparent plastic to reduce the upward heat loss from the absorber plate;

- Header or manifolds, to admit and discharge the fluid; - Container or casing, which surrounds the various components and

protects them from dust, moisture, etc. Flat plate collectors have advantages over other types of solar collectors because they absorb direct-diffused and reflected components of solar radiation, fixed in tilt and orientation –no need to tracking sun, easy to make and low in cost, have comparatively low maintenance cost and long life, operate at comparatively high efficiency (Garg and Prakash, 1997 – p.46-49). Major current applications of these units are solar water heating, solar drying, solar distillation and solar ponds.

B/ Solar Concentrating Collectors A solar concentrator is a device that concentrates the solar energy incident over a large surface onto a smaller surface (fig.4). Concentration is achieved by the use of a suitable reflecting or refracting element. Solar concentrators can achieve higher temperature up to 3000ºC. Important use of concentrators is for producing steam for generating electricity.

Solar/Solaire - parabolic trough sy stem / réflecteur cy lindro-parabolique

Photo. (2): Parabolic Trough System Source: www.canren.gc.ca/tech.appl/index.asp Solar concentrators operate only on the direct radiation. They have the potential application in both thermal and photovoltaic. In order to get maximum concentration, an arrangement for tracking the sun’s virtual motion is required (Tawari, 2002 – p.251).

Incident rays

Sun

Centre of curvature

Spherical mirror surface

Absorberboom

Fig. (4): Cross-sectional View of A Hemispherical Mirror Concentrator Source:Tawari, 2001 The solar concentrating collector consists of:

- Focusing devices. - An absorber provided with or without a transparent cover. - Tracking devices for continuously following the sun.

The advantages of the concentrators are as follows according to Garg and Prakash:

- It increases the intensity by concentrating the energy available over a large surface onto a small surface (absorber).

- Due to the concentration on a smaller area, the heat-loss area is reduced. Further the thermal mass is much smaller than that of a flat plate collector and hence transient effects are small.

- The delivery temperature being high, a thermodynamic match between the temperature level and the task occur.

- It helps in reducing the cost by replacing an expensive large receiver by a less expensive reflecting or refracting area (Garg and Prakash, 1997 – p.116).

C/ Solar Evacuated Collectors Evacuated tube collectors are stationary collectors designed to minimize heat losses from conduction and convection by insulating the absorber with a vacuum jacket, and to minimize thermal radiation losses by using selective coating on the absorber. Solar evacuated collector is an improved type of flat plate collector. It is the most efficient and most costly solar collector (Eltom, 1993). According to Tiwari, on a flat plate collector there is further scope of reducing convection heat losses from the absorber to the glass cover. This can be achieved by completely removing the air between absorber and glass cover. The only heat loss mechanism remaining is radiation. The resulting stress on the cover plate due to outside air restricts the use of vacuum in flat plate collectors. To avoid this, the plate must be supported at frequent intervals. Also, it is very difficult to maintain vacuum in a flat plate collector and hence, the evacuated –tube collector was invented (Tiwari, 2002 – p.149).

Sketch of a heat pipe collector

Fig.(5): Evacuated Tube Collector Components Source: www.solarserver.de/index-e.htm/ There are various types of evacuated tube collectors. The main components of it: glass cover, insulation, selective absorber and vacuum (fig.5).

Solar/Solaire - v acuum tube solar collectors / capteurs sous v ide

Photo. (3): Evacuated Tube Collector Source: www.canren.gc.ca/tech.appl/index.asp Evacuated tube collector uses are similar to the flat plate collector. Due to their ability to deliver high temperature efficiency, another potential application is for cooling of buildings by regenerating refrigeration cycles. Similar to a flat plate collector, it works on direct and diffused radiation, and does not need to track sun way. Evacuated –tube collector has an advantage over the flat plate collector, it can operate in lower insulation

levels and can, therefore, collect more energy in cloudy days (Tawari, 2002 - p.149-150).

2.3- Solar Thermal Applications 2.3.1- Solar Water Heating

Solar energy to heat water has been in use for many years. Technological advances in solar water heating have been very rapid in the last 40 years. The obvious benefit to the householders can no longer be overlooked, where the climate is ideally suited for the application of solar energy for water heating, particularly, in the present situation of acute energy shortage. Solar water heaters find wide applications in large establishments like hostels, hotels, hospitals, industry such as textile, paper and food processing, domestic use and heating swimming pools (Tawari, 2002 - p.169). The main components are: flat plate collector, heat exchanger and an insulated storage tank.

Photo(4): Sample of a Local Solar Water Heater (Energy Research Center) Water circulating through the collector, is heated, and is held in the tank for use when needed. The transfer of heated water may be carried out either directly or through a heat exchanger. The use of a heat exchanger mainly depends upon the quality of water and climatic condition of a location where the system is to be installed.

The mode of transfer of water from the collector to an insulated storage tank can be either natural circulation thermosiphen or forced circulation (fig.6). Domestic installing employ thermosiphon circulation, which allows the water to recycle through the absorber without a pump, but large commercial and industrial plants delivering some thousands of liters of hot water per day use forced circulation with thermostatic control.

TANK

HEATERTO LOAD

COLD WATER SUPPLLYCHECK VALVE

PUMP

COLL

ECTO

R

CONTROL& DATA

ACQUESITION

SOLAR RADIATION

AUXILIARY

Fig.(6): Schematic Drawing of A Forced Circulation Solar Water Heating System

Solar water heaters offer a number of advantages such as: being simple to construct and install, almost no maintenance and running cost, save time and energy, economically competitive with electric water heater, required temperature easily achieved with simple requirements.

A/ Needs for Domestic uses Hot water uses in households are for: washing clothes, cleaning dishes, preparing tea, and taking shower mainly in winter. According to a survey on the hot water demand of Khartoum households, (ERI, 1986), the percentage of households that uses heated water frequently is low. Most users are from the high-income group. There is misconception concerning use of hot water, although, hot water has its advantages: firstly; from a hygienic point of view. Secondly it can be a good solution for manholes drainage problems due to the nature of Sudanese food that contains a lot of fats.

B/ Needs for Industry As shown before, hot water is needed for many of industries like textile, paper, food processing, etc. The conventional way for preparing hot water in factories leads to a lot of problems including: environmental pollution, worker injuries, hazard and cost.

Photos (5, 6): Water Boiler Above photographs show the water boiler in one of the food industry factories in Khartoum. It is clear that the walls are affected by the smoke that generated from the powering of boiler; this smoke has a negative impact on the environment. Solar water heating can provide hot water with different quantities and without the previous problems.

C/ Needs for Service Buildings Large buildings like hotels, hostels, offices and hospitals need to use large amounts of hot water in kitchens, laundries, bathes, etc.

Photo (7): Water Heating Apparatus Above photograph shows part of the ancient boiler that provides Khartoum hospital laundry with steam for heating water and hot air. This part is not, currently, working and the laundry lost availability of hot

water, which is an important factor in sterilization. At the same time solar water heating can be an efficient and economic solution to satisfy the continuous need of hot water and air.

2.3.2- Solar Refrigeration and Air Conditioning Solar energy can also be used for cooling or for refrigeration required for preserving food. Solar cooling appears to be an attractive proposition due to the fact that when cooling demand is more, the sunshine is strongest. This along with the necessity for providing thermal comfort for people in hot areas of the world for providing food preservation facilities may be the motivating factor in continuing research development in field of solar cooling. Similarly solar refrigerators or cooled spaces. Cold storage can be provided economically for preserving essential drugs and food in isolated localities (Tawari, 2002 - p.278). The application of solar energy to provide cooling was demonstrated in France over 100 year ago. Since that time there has been serious effort to provide commercially available solar cooling or refrigeration systems until the recent increase in energy price (Eltom, 1993). Space cooling using solar thermal technologies consist of three main classes: 2 Adsorption Cooling: In adsorption cooling systems, heat collected from a solar thermal collector is used to evaporate a pressurized refrigerant in a vapor generator. Desiccant Cooling: Desiccant cooling systems use a desiccant, such as a water absorbing wheel, to remove most of the moisture content from the air, making it feel cooler, particularly in humid, tropical climates. The heated air then passes through a heat exchanger, which is then exhausted, from the system that passes the water-absorbing wheel, drying it out for use again. The desiccated, cooler air passes through an evaporative cooler to chill the air further before exiting the system.

2 http:// acre.murdoch.edu.au/refiles/lowtemp/text.html

Heat Engine (Rankine cycle): Heat engine cooling is similar to that of conventional air conditioning systems, except that solar collectors are used to heat the working fluid. This heated working fluid is then used to power a Rankine cycle heat engine. The choice of a particular system not only depends on its economics but also on local factors such as climate, availability of cooling water, auxiliary energy source and the type of collector available. The temperature limitation of solar energy collectors along with the need of a suitable heat storage device makes the solar cooling system costly. The solar air conditioning system consists of many components: the solar collector – heat storage devices – solar cooling devices (based on absorption or vapor cycle). The use of collector, depending on the temperature- requirement, can be employed to heat a fluid, which is used to operate the cooling device. The heat collected from the building is rejected to the atmosphere using a cooling tower or any other suitable heat rejection devices (Tawari, 2002 – p.278).

Cooling Needs Sudan is one of the developing countries located in the tropical zone that is the hottest zone in the world. At same time Sudan suffered from a severe shortage in electrical supply in its towns and there is no electrical supply at all in most of its rural areas. In Khartoum the accelerating rate of urban growth due to the internal immigration of people without equivalent growth rate of services, led to failure in the supply of electricity which resulted in electrical cuts most of the day, especially in summer during peak demand of cooling. This led to unpleasant internal environment during harsh summer. The use of a generator is not the best solution; firstly: because of its environmental impact – producing of pollution and noise. Secondly; it can obtained just by the high-income group and even can’t meet peak demand. It is necessary, therefore, to consider a simple system that does not require conventional electrical power. Solar cooling can be an optimum solution that satisfies cooling demand in Sudan, but unfortunately there is no progress in solar cooling technology.

Eltom, noted that, In fact solar cooling is the most promising application of solar energy in the Sudan especially if subsides or loans were made available to help the public to produce locally and install solar refrigeration and air conditioning systems. Moreover, in remote locations a solar thermal system offers considerable advantages for refrigeration and freezing of food, drugs and other materials (Eltom, 1993).

2.3.3- Solar Drying A traditional and widespread use of solar energy is for drying, particularly of agricultural products. The customary technology is to spread the materials to be dried in a thin layer on the ground to expose it to solar radiation and wind. In recent years solar drying technology was well developed and it now provides an improved efficiency and controlled exposure to solar radiation and wind. Solar driers are expected to be used by farmers with limited technical skills and small capital. Solar dryers are classified into three different types:

- The direct dryers in which the material to be dried is placed in an enclosure with a transparent cover and surrounding absorbing media. Heat will be generated by absorption of solar radiation on the product itself as well as the enclosure surface.

- Indirect dryers are those in which the products are dried by heated

air drawn from a separate solar air heater. - The third is the combined dryer in which both solar radiation and

indirect heated air from separate collectors can be utilized (Taha, 1989).

Photo(8): A Sample of a Local Solar Dryer (Energy Research Center) The solar dryer consists of a solar collector, a dryer, where both are covered with transparent foil, and two small axial direct current fans powered by 53W solar module. The fan is installed at backsides of the collector to ensure continuous ventilation by sucking the ambient air into the dryer. In the drying process there are many interacting variables such as airflow rate, temperature, relative humidity, characteristics of the material to be dried and its shape (Eltom, 1998).

Needs for Solar Drying In Sudan many of seasonal crops need to be reserved and used in other seasons. Sun drying is one of the methods of drying in Sudan. Crops are spread on trays under the sun for several days depending on the size of the product. Conventional sun drying has many disadvantages: product contamination from wind blown dust and dirt, as well, it takes much land. Solar drying can meet the problems of conventional sun drying. These proposed devices, therefore, should be simple, inexpensive and use least land area.

2.3.4- Solar Distillation Water distillation is essential for the provision of water suitable for drinking and cooking where water quality is poor, either because it is saline, as in many parts of central Australia, or contaminated with biological organisms.

The basic method of water distillation is to admit solar radiation through a transparent cover to a shallow; covered brine basin; water evaporates from the brine; and the vapor condenses on the covers which are so arranged that the condensate flows therefore into a collection trough and hence into a product – water storage tank (Taha, 1989). Solar distillation mainly provides distilled water for batteries, Laboratories, food and textile industries, etc.

2.4- Solar Photovoltaic The direct conversion of sunlight to electricity by means of solar cells is the photovoltaic effect. Solar cells use energetic photons of the incident solar radiation, converting solar energy to electricity. Photovoltaics (PV) cells respond to direct and diffused radiation. PV can be used for many purposes. In the developing countries, due to the decentralization of its power grid, PVs are used for operation-localized tasks like refrigerators of vaccine and water pumping.

Photo. (9): Photovoltaic Array

2.4.1- Historical Background of Photovoltaic

The development of photovoltaic cell started in 1839 when the French physicist Alexander Edmand Becquerel discovered that some copper oxide electrons could produce electrical power, when they were lighted. 3 In 1877, Adams and Day observed the photovoltaic effect in selenium, followed that in 1914 solar selenium and copper oxide cells with 1% efficiency. Fuller, Pearson, and Chapin produced the first photovoltaic cell of silicon, which had an efficiency of 6%, in 1954 in the USA. By 1958 efficiency reached 14% and in 1988 Velinden et al came with a 28% efficiency cell (Wisal, 2001). 4

2.4.2- Forms

The basic component is the photovoltaic cell. At the manufacturing stage, the photovoltaic cells are assembled into modules, which, in turn, are assembled into the arrays that are fixed on supports in the field (fig.7).

Fig. (7): Conceptual Relationship between the PV Cell, Module and Array SSoouurrccee:: WWiissaall,, 22000011

2.4.3- Photovoltaic System Components

3 www.nmsea.org 4 (Wisal, 2001) based on ( Bube, 1998)

A complete PV system to deliver electricity to an end use has a variety of components in addition to its PV array, depending on the system (fig.8). PV system components include:

Fig. (8): Grid Connected PV System Components

Source:www.flasolar.com/PV cells arrays.htm

Photovoltaic cell The cells (as described by Ross M & Royer J, 1999) are encapsulated in a plastic material sandwiched between a sheet of tempered glass and a backing material. The backing material is usually plastic, but sometimes aluminum/glass are used. Often the edge is framed in Aluminum for strength and easiness of attaching the module to a structure (Wisal, 2001). A typical solar cell consists of a cover glass or other encapsulate, an-anti reflective layer, a front contact to allow the electrons to enter a circuit and a back contact to allow them to complete the circuit, and the semiconductor layers which is the most important part where the electron begin and complete their voyages. The most common PV devices at present are based on silicon. Three kinds of silicon cells are manufactured: mono-crystalline, poly-crystalline and amorphous.

PCU The Power-Conditioning Unit (PCU) is the device that regulates and modifies the electrical output to meet the requirements of the rest of the system. PCU consists of the battery, charge regulators, inverters and power-point conditioners. Charge regulators: an electronic charge controller is used to protect the battery from the excessive charging and discharging. Inverter: PV systems are usually designed to produce a direct current at 12 volts. Where a 220 volt alternating current is required, it can be provided through an electronic inverter. A significant power loss – up to 15%- may be incurred.

Energy Storage and Batteries Used to balance the mismatch between the electrical load and the electricity production. In most stand-alone PV power systems, storage batteries with charge regulators have to be incorporated to provide a back-up power source during periods of low solar irradiance.

Cables To carry low voltage DC over any distance thicker cables are needed to limit losses of power due to voltage drop. With longer cables resistance to current increases and the greater is the power loss. (Wisal, 2001)

Other Components Other components include connectors, switches, junction boxes, fuses and small items.

2.4.4- Photovoltaic Systems Stand-alone Photovoltaic systems

Stand alone systems are virtually self sufficient, are not hooked into the electricity grid, have backup system. Autonomous systems include stand-alone photovoltaic system without a battery, stand-alone photovoltaic system with battery and stand-alone photovoltaic-hybrid system that is supported by a genset. A genset is a generator powered by a diesel, gas or gasoline engine (Wisal, 2001). Grid connected photovoltaic systems A grid connected PV power system is connected to the commercial electricity grid (fig.8). These systems use photovoltaic electricity mainly and the net supply as a back up system. The operation of such systems is based on the principle of feeding power into the grid when solar generation exceeds load demand (during daytime) and taking power from the grid during night. These systems don’t require storage of energy but require additional components to regulate voltages.

2.4.5- Photovoltaics Need In Sudan, the accelerating rate of urbanization and industrialization is not supported by the required services. There is, therefore, severe shortage of electrical supply in all country including Khartoum, while there is no electrical supply in most remote areas. In Khartoum, during harsh summer days residents are faced with intolerable living conditions. Different types of buildings are affected by electrical cuts because many of activities depend mainly on electrical supply, even with the presence of stand by generators and other alternative solutions that cannot cope with the long periods of electrical cuts. A need for a reliable alternative solution appeared.

2.5- The Main Areas of Concern

The most common part of thermal applications is the solar collector. Use of any applications requires the use of a solar collector, while PV array is the most important part in PV system. Both a solar collector and PV array are outdoor panels used to collect solar radiation. Most types of collectors used with buildings are the flat plate collectors which can be justified as panels. Mounting of these panels on a building influences the appearance of the buildings. In addition to that other components of these two systems have influence on the building internally and need to be studied in design stage while thinking of space requirements. This dissertation, therefore, is oriented to the study of the integration of solar panels with different buildings with special references to building in Khartoum from an architectural point of view, as well as the treatment of other components of system.

2.6- Solar Collectors and PVs Orientation In Khartoum, a large annual total of solar radiation is available with clear sky. The aim is to collect as much radiation as possible. The surface of a solar collector, ttherefore, must be oriented towards the sun most of a day and avoid over shadowing by other buildings and high trees. Proper orientation depends on latitude and the time of the year of most solar collection is required, which is summer time. In Khartoum it is recommended that orientation of solar panels should be at an angle 15° towards south (tilt angle equal to the latitude).

2.7- Factors that affect the Performance of Solar Collectors and PVs

There are many factors that affect the performance of solar collectors and PV: Dust and suspended particulate: affect the amount of solar radiation by reflecting part of it, in addition to that accumulation of dust and suspended particulates on the collector’s top insulate collector from solar radiation.

Water vapor, high humidity and clouds: Work as shading to solar radiation then decrease the amount of solar radiation received. In case of PV Water can cause corrosion to metal parts, penetrate the laminations protecting the cells leading to increased resistive losses or even shortcuts (Wisal, 2001) Wind: Helps in increasing of heat losses and decreasing air temperature then affect solar radiation amount. High velocity wind can distort the supports structure of a collector. Daily variation of temperature: In case of PV expansion and contraction caused by daily solar heating and cooling of the array can also cause cracks, short circuits or disconnection. Lifetime of systems is usually not less than 20 years. Some last for more than 25 years.

Goossens, pointed that, during the last few years, there has been an increasing interest in the natural degradation processes that occurs on solar collectors mounted outdoors. Many freshly installed collectors already show a reduction in their thermal or electrical performance. Since the losses continuously increase in the course of time, collector efficiency drops to very low values after only a few years. Many collectors are designed to remain operational for period of 20 years and more; hence the study of natural degradation of solar cells is of particular importanance. The primary sources of solar collector degradation are: hail, chemical weathering and contamination with airborne particulate either natural (soil) or industrial (carbon, soot, other dirt) origin (Goossens et al., 1999).

2.8- Environmental impact Solar applications are environmentally friendly because the operation of solar applications does not emit irradiative substances or any gaseous/ liquid pollutants. Also, they do not emit noise.

22..99-- VViissuuaall iimmppaacctt

Proper mounting of solar collector within a building has its effect on the appearance of the building.

22..1100-- SSuummmmaarryy IInn tthhiiss cchhaapptteerr,, aa rreevviieeww aabboouutt ssoollaarr eenneerrggyy,, ssoollaarr tthheerrmmaall eenneerrggyy aanndd ssoollaarr pphhoottoovvoollttaaiiccss wweerree pprreesseenntteedd.. TThhee ppaarrtt ooff tthhee ssoollaarr tthheerrmmaall eexxppllaaiinneedd iittss hhiissttoorryy,, ddiiffffeerreenntt ttyyppeess ooff ssoollaarr ccoolllleeccttoorrss,, ddiiffffeerreenntt tthheerrmmaall aapppplliiccaattiioonnss aanndd tthheeiirr nneeeeddss.. SSoollaarr pphhoottoovvoollttaaiiccss wweerree bbrriieeffllyy ddiissccuusssseedd,, ttooggeetthheerr wwiitthh hhiissttoorriiccaall bbaacckkggrroouunndd,, PPVV ffoorrmm,, ccoommppoonneennttss aanndd ssyysstteemmss.. TThhee llaasstt ppaarrtt eexxppllaaiinneedd ssoollaarr ppaanneellss oorriieennttaattiioonn,, ffaaccttoorrss tthhaatt aaffffeecctt tthheeiirr ppeerrffoorrmmaannccee aanndd tthhee vviissuuaall aanndd eennvviirroonnmmeennttaall iimmppaacctt ooff uussiinngg ssoollaarr ssyysstteemmss,, aass wweellll aass,, tthhee mmaaiinn aarreeaass ooff ccoonncceerrnn.. CHAPTER 3 CONTEXT 3.1- Sudan

Sudan is a vast country in North Africa with a total land area of one million square miles (2.5 million square kilometers). It lies between latitudes 3° and 23° north; and longitudes 21° and 39° east. Sudan extends approximately between nine African countries (Egypt, Libya, Chad, Central Africa Republic, Zaire, Uganda, Kenya, Ethiopia and Eritrea) and has only a short coastline along the red sea in the extreme northeast (fig.9). The total population in Sudan according to census 1993 was 25.5 million inhabitants with an annual growth rate of 2.8%.

Sudan in A frica

Fig. (9): Sudan Location 3.2- Sudan Climate

Climatically, Sudan is considered as a tropical country with different climatic zones, though strict lines can’t separate these zones and the character of each zone merges gradually into the other. The climate of the Sudan is wholly tropical; therefore, there is no part of the country where the sun does not pass directly overhead at sometimes of the year. Un-nerving heat and the steady progress of climatic change from south to north are the dominant features of the Sudan climate. In the northern frontier region, conditions vary from very hot desert with daily maximum temperature and no rainfall, through a belt of summer rainfall of varying intensity and duration to an almost equatorial type of climate in the extreme south, where the dry season is very short. Because of the absence of mountain barriers obstructing the flow of air stream between north and south, there is a gradual change of conditions with latitude, and it is not easy to indicate obvious divisions between one type of climate region of Sudan and another (Eltom, 1998). According to Omer, Sudan has predominately continental climate, which is roughly divided, into three climatological regions: Region 1 is situated north of the latitude 19°N. The summer is invariably hot (mean maximum temperature 41°C and mean minimum temperature 25°C with large diurnal variation; low relative humidity average 25%). Winter can be quite cool. Sunshine is very prevalent. Dust storms occur in summer. The climate is a typical desert climate where rain is infrequent and diurnal (annual rain fall of 75-300mm) the annual variation in temperature is large (maximum and minimum pattern corresponding to winter and summer). The fluctuations are due to the dry and rainy seasons.

Region 2 is situated south of latitude 19°N. The climate is a typical tropical continental climate. Region 3 comprises the areas along the red sea coast and eastern slopes of the red sea hills. The climate is basically as region 1, but it is affected by the maritime influence of the red sea. The two main air movements determine the general nature of the climate. Firstly, a very dry air movement, from the north that prevails throughout the year, but lacks uniformity; and secondly, a major flow of maritime origin that enters Sudan from the south carrying moisture and bringing rain. The extent of penetration into the country by airflow from the south determines the annual volume of rainfall and its monthly distribution. The average monthly rain fall for Sudan indicates the decreasing trend in the volume of rain fall, as well as in the duration as one moves generally from the south towards the north and from the east towards the west (Omer, 1997).

3.3- Khartoum Climate Khartoum, the Sudan’s capital, lies within a hot dry climatic belt, at 15° north and 30° east. It has two main seasons; the first is summer from April until October, hot and dry from April to June, becomes slightly humid and a little cooler from July to October. The severness of climatic condition is modified by a short rainy season. Another season is winter, which is from November to March when it is cool and nice. Severe weather conditions arise during early part of summer season when there are the highest daily maximum temperature and the longest sunshine hours and the greatest intensities of solar radiation. Temperature is at its lowest just before sunrise and highest over land about two hours afternoon when the effects of the direct solar radiation and the high air temperature already prevailing are combined (Wisal, 2001). 5

5 (Wisal, 2001) based on ( Konya, 1984)

hour of dayJan Feb March April May June July August September October November December1 15.4 20 22.9 25.3 30.2 28.9 28.7 30.2 28.4 29.6 24.7 19.62 15.3 19.6 22.2 24.5 29.7 29 28.7 28.8 28.1 29.9 24.8 18.73 14.9 19 21.5 24.2 28.6 28.8 28.1 28.1 28 28.9 23.8 18.64 14.6 17.6 20.9 24.5 27.8 28.3 27.3 27.7 27 28.7 23.4 18.35 14.7 17.2 20.4 24.3 28.9 28.2 27.1 27.4 27.2 28.3 22.8 17.46 14.7 16.5 19.7 24.6 29.3 28.2 27.4 26.7 27.3 28 22.5 17.27 15.5 17.6 20.6 25.7 29.9 28.3 28.5 28 28.6 29.5 23.5 17.58 16.8 19.7 22.9 27.3 31.5 29.7 29.6 28.9 30.8 31.4 24.6 19.39 20.9 22.3 25.7 29.3 33.5 31.2 30.7 30.1 32.8 33.5 26.3 21.1

10 23.9 25.8 27.6 31.5 35.8 33.1 33.1 31.7 35.1 35.3 29.2 23.911 27 29.2 30.2 33.8 38.2 35.1 35.9 34.7 36.8 38.2 32.1 26.712 30.5 32.7 32.6 37 40.7 36.5 37.5 36.8 39.2 40.5 34.1 29.313 32.7 34.8 35.3 39.5 42.9 37.8 39.3 39.1 41.1 43.4 36.3 32.914 34.5 36.9 36.8 41.4 44.1 39.2 41.6 40.6 42.5 44.2 37.2 34.415 34.7 35.8 37.3 43.2 45.3 40.1 41.6 41.3 43.6 43.7 38.1 33.916 33.8 34.8 36.3 42.8 44.9 40 41.9 41.5 43.2 43.8 36.9 31.617 31.3 31.9 34.1 41.3 43.7 39.2 40.2 40.4 42.1 41.6 34.2 27.918 28.5 28.4 31.7 39.9 41.1 38.5 38.8 38.4 41.5 37.4 31.3 24.719 25.4 25.1 29.2 37.8 38.9 37.1 37.2 37.2 39.7 34.5 29.2 21.520 23.7 23 27.1 36 36.8 35.5 35.8 35.4 37.6 33.4 27.7 20.421 22.3 21 26.4 34.2 34.7 34.2 33.9 33 35.7 31.5 26 19.522 21.4 20.1 24.6 33.4 33.1 32.5 32.7 31.6 34.3 30 25.2 18.223 20.4 19.1 23.4 31.7 31.6 31.6 31.1 29.6 33.6 30 24.8 17.524 20.1 17.9 22.4 30.3 30.4 30.7 30.3 29.1 32.8 29.5 24.9 17

Table (1): Hourly Values of Air Temperature Represented in Khartoum by the 21st day of each Month in the Year Yellow-shaded cells: represent the hours of the day of highest temperatures. It shows that from April until October the temperature reaches over 40° C for several hours. Green-shaded cells: represent the minimum temperatures reached during the day; except for December, it is the first hour before sunrise. Even during winter, from November to March the highest temperature is more than 30° C and the minimum temperature reached is not less than 14.6° C during February (Source: Wisal-2001).

3.4- Design Principles in a Hot Dry Climate In hot climates, the sun is the major source of heat. Climatic characteristics of hot arid climates, as summerarised by abundance of literature, are high intensity of direct and diffused solar radiation, high diurnal6 and annual temperature ranges, low precipitation and low percentage of humidity. Dust storms occur at part of the year. All these elements composed an uncomfortable environment.

6 Defined as day and night temperature variations

Building design must consider all these characteristics and must be adapted to summer conditions, basically a problem of protection from intense radiation from all around. The main objective is to establish the optimum orientation with regard to the sun and prevailing wind. Other factors must be considered: the façade exposure to the sun, the openings, and the roof. Fathi, discussed the factors to be considered in hot dry climates: Orientation: In a hot dry climate the optimum orientation of the building block with regard to the sun and prevailing wind is east- west. Façade: the north façade is the least exposed to the sun7 – exposure occurs only in the early and late hours of summer day. The Southern façade exposure is high over the horizon in summer and can be shaded using a relatively small overhang. In winter it is low, allowing sunshine to penetrate when it is most desirable. The exposure of the eastern façade is from sunrise to noon and the western façade exposure is from noon to sunset. Openings: A window opening has functions that it helps the sun light and air to enter and it provides a view. Windows size, form and location are determined by local climate conditions. So, in hot dry climates it is rare to combine these three functions in a single architectural solution. Roof: is the most exposed element to the sun, therefore, the reflectivity of the outer surface of the roof and the thermal resistivity of its materials used is important. The shape of the roof is considerably important in a sunny climate. A flat roof receives solar radiation continuously throughout the day. A pitched or arched roof has advantages over a flat structure. The area where the warm air rises, to emit through the roof, is farer from the level of the inhabitants. Also, the total area of the roof is increased so that the intensity of solar radiation is spread over larger surface reducing the average heat increase of the roof and the heat transmission to the interior of the house. Also, part of the roof is self-shaded by the other part. This shaded area acts as a radiator absorbing heat form the interior space and from the sunlit part of the roof. This

7 in area north to the tropic of cancer

partial shading is effective especially in vaulted roofs. The shape also increases the speed of the air flowing over their curved surfaces that helps reducing the temperature of such roofs (Fathi, 1986). Givoni, discussed that, Bioclimatic architecture in hot dry regions involves architectural design, choice of materials aiming at providing comfort and minimizing the demand of energy used to cool a building by minimizing heat gain and the solar heating of the building envelope and the solar penetration through windows. The conventional architectural design elements to achieve this are orientation and the windows size, location and details. Also, shading devices, thermal resistance and heat capacity of the building envelope (Givoni, 1994). The courtyard is the most common element in hot arid climates; it has a lot of advantages in creating a good environment. Ratti et al, pointed that, an abundance of literature claims that courtyards are an environmentally responsive building form for hot arid climates. The courtyard introversion fulfils several functions in hot arid regions: the creation of an outdoor yet sheltered space; the potential to exploit ingenious natural cooling strategies; the protection against wind-blown dust or sand; and the mitigation of the effects of the solar excess (Ratti et al, 2003). The courtyard has strong presence in Islamic architecture. Thus, in the design process in hot arid zones the main problems that confront the architect are protection against heat and provision of adequate cooling. According to Wisal, people in hot dry lands for whom air conditioning is a luxury they can’t afford, most of the large population in the developing countries, have thrown a tremendous challenge to architects and engineers who are faced with the responsibility of providing comfort in buildings by means other than complete air conditioning (Wisal, 2001). 8

3.5- Energy Situation in Sudan During last decade, Sudan, like most of the oil importing countries, suffered a lot from spending more of its hard currency earning in importing oil, but could not meet the increased demand of energy.

8 (Wisal, 2001) based on (Saini, 1980)

Nonetheless, after exploiting oil in last years Sudan still suffered from acute shortages in energy. Traditional biomass, mainly fuel wood and charcoal is by far the most significant fuel, according to Wisal, in the Sudan, 31 Km² of the woodland savannah are lost annually. That led to the problem of over-exploitation of wooded lands. Biomass is a renewable source yet; overuse can lead to shortage as the fuel-wood crisis that occurred in North Africa in the eighties (Wisal, 2001).

Photo. (10): Most Common View, Charcoal Market, in the City of Khartoum, Located at the Middle of an Open Space within a Neighbourhood Omer pointed that, Biomass energy supply continued to show the domination in the total energy supply (87%) since 1970’s. The basic form of biomass comes mainly from firewood, charcoal, crops residue. Out of total fuel wood and charcoal supplies, 94% was consumed with household sector with most of the fire wood consumption in the rural areas. Petroleum energy supply represented about (12%) of the total energy supplies (mainly furnace, and diesel consumed by electricity sector and the remaining 80% consumed by other sectors with half of the quantity [50.4%] in transportation sector). The electricity sector represented almost (1%) of the total energy supplies with hydropower representing 55% of the total electricity supplies and the remaining 45% comes mainly from thermal generation.

The household sector consumed 50% of the total electricity supplies (Omer, 1998). Despite these, the availability of electrical power is very low. The accelerating rate of urbanization is not parallel to the extension of infra-structure. Most of households, with a high standard of living, installed electric power generators, which have bad environmental impact, that they produce pollution and noise. The rapid increase of population growth rate, improving standard of living, economic development, urbanization and industrialization led to increased demand of energy. The fossil fuels are depleting sources and can’t meet this demand. The need of renewable sources appeared. Solar energy can be the best solution while Sudan possesses a high abundance of sunshine most of the year.

3.6- Solar Energy in Sudan Sudan, due to its geographic location, enjoys a variety of climate zones, from tropical climate in Southern regions to desert in its Northern regions. This makes Sudan rich with solar energy sources all the year especially in the North (fig.10).

Fig (10): Annual Global Irradiance on a Horizontal Plane at the Surface of the Earth (W/m² average over 24 hours). Source: Eltom, 1993

Taha, discussed that, clearly with such a feature as the geographical location and the extensive area, Sudan can be considered as one of the most solar rich countries in the world. It appears from meteorological data, that solar radiation of the order of 1.2KW/m² can be reached. The sunshine duration in the Sudan on the average varies between 10-12 hours/day. Among the main atmospheric sources of solar radiation depletion (i.e., dust, clouds cover and water vapor), dust is considered to be the most significant source. The diffused solar radiation, in Khartoum for example, is about 20%-40% of total solar radiation: cloudiness, sand rising and sand storms (haboob) are major causes of the diffusion of direct solar radiation. Even with a relatively high fraction of diffuse solar radiation, Sudan enjoys considerable solar radiation ranging between 6-10 GJ/m²/year on a horizontal surface (it should be noted that the amount of solar energy received on a tilted surface facing the equator will be in average 10% higher than the energy received on a horizontal surface). The annual total solar radiation is low in the Southern regions of Sudan and increases as we move to the North (Taha, 1989). Omer pointed that, Sudan has been considered as one of the best countries for exploiting solar energy. The sunshine duration is ranging from 7 to 11 hours per day (see table 2) with high level of solar energy regime at an average of 20-25MJ/m²/day 9 on a horizontal surface (see table 3). The annual daily mean global radiation ranges from 3.05 to 7.62 KWh/m²/day (Omer, 1998).

9 To convert MJ/m² to KWh/m² multiply by 0.278

Fig.(11): Monthly Mean of Global Solar Radiation(MJ/m²) for Summer in Sudan / Source: Eltom, 1993

Fig.(12): Monthly Mean of Global Solar Radiation (MJ/m²)for Winter in Sudan /Source: Eltom, 1993 In Sudan, solar radiation has been recorded at 15 meteorological stations since1957. According to Eltom, several stations spread fairly uniform over the Sudan, which record meteorological data including sunshine duration, water vapor, solar radiation, air temperature, extra. Since such stations have been in operation for a long period, an appreciable number of recordings of this nature are available (Eltom, 1998). Solar energy constitutes the main renewable energy source in Sudan. The following are some of the uses in the field of solar energy: - Photovoltaics: a number of pilot stations (more than 50) employ PV generators for water pumping, lighting, refrigeration and telecommunication. - Solar Thermal Application: in this area research and development is progressing in a very satisfactory manner and some of the products have already reached the consumer. Example of these are solar cooker-ovens and Commercial solar applications which are investigated including a solar crop dryer, water desalination, cold store for vegetables and fruits and solar water heating (Omer, 1994).

3.7- Summary A review about Sudan and Khartoum climate were presented in this chapter, in addition to the design principles in hot dry climates. In hot region, like Khartoum, building design requires applying of these principles for minimizing heat gain and consequently energy demand of building. Followed that, the energy situation in Sudan showing the problems of energy shortage. It appears that conventional energy can’t meet energy demand and there is a need for alternative energy sources.

It has also been explained that Sudan enjoys a considerable amount of solar radiation all around the year. Solar energy can, therefore, be the most promising source of energy.

CHAPTER 4 SOLAR TECHNOLOGY AND BUILDINGS 4.1- Building Design

Buildings design is a creation of variety of architectural actions for the purpose of habitation and settlement. Climatically, building is a creation of a structure whose internal environment is different from the external environment. One of the main purpose of building is to provide an artificial environment that is aesthetically appealing and more conductive to particular processes or to human occupancy than the natural environment. In the design process, one tries to achieve function and appropriation to cultural needs. There is a need to the study of the building’s form, orientation, facade exposure and materials used. Design process requires a multimedia of information; geographical (climate, topography), climate appears to be one of the strongest determinants of architectural form (Fathi-1986), as well as, socio-cultural background (economics, culture, etc). Capeluto, mentioned that, during the preliminary stages of a building design, the architect deals with the general geometrical factors related to the building’s shape. These factors include the building height in relation to street dimensions, facade orientation and the building proportions. In these early stages the solar potential of the building and the surrounding area are determined, assuring the exposure of the elevation and side walks to the winter sun, and creating the appropriate shading during the critical hours of the summer days (Capeluto, 2003). Proper design can be achieved also by using least amounts of energy and materials, which is a response to the environment. According to Sam C. M, buildings are significant users of energy and materials in society and energy conservation in buildings plays an important role in urban environment sustainability. A challenging task to architects and other building professionals today is to design and promote low energy buildings in a cost effective and environmentally responsive way (Sam C. M, 2001).

Building design needs to consider the new trends towards the renewable energy and the sustainability. Tombazic pointed new approaches in architecture, indicating that, architectural design has, in recent years, started to alter course and become much more holistic in its approach while trying to address itself to: the achievement of sustainable development, the depletion of non-renewable resources and materials, the life cycle analysis of building, the total pollution effects of buildings in the environment, and the reduction of energy consumption and human and comfort (Tombazic, 1994). As a result of using renewable energy technology, specifications and requirements for the construction and design of buildings have also changed. Hagemann, discussed that, new technological developments have allowed completely different visions of a conventional façade or roof to be created. A part from providing protections against the weather and acting as a defense mechanism against intruders, the envelope must increasingly meet society’s growing insistence on comfort, the obligation to save fossil energy, the need to avoid the unwholesome effects of a man-made environment such as noise pollution, waste gas emissions or other influences and the demand to make use of active and passive solar design principles and techniques (Hagemann, 1996).

4.2- Approaches of Solar Energy to Buildings If the 19th centaury was the age of coal and the 20th of oil, the 21st will be the age of the sun. Solar energy is set to play an ever-increasing role in generating the form, and affecting the appearance and construction, of buildings. (Thomas R. et al, 1999). Basically, there are two approaches of applications of solar energy to buildings: Passive systems and active systems. The way solar systems are used in buildings is different from what it used to be. Buildings are no longer designed to use just passive solar energy systems, such as windows and sunspaces, or active solar systems, such as solar water collectors. In fact, the words passive and active no longer make sense, as the newer buildings combine several of these technologies. They may be both energy efficient, solar heated and cooled, and PV powered, i.e. they are simply "solar buildings".

4.2.1- Passive design system Passive solar design is the use of the form and fabric of the building to admit, store and distribute primarily solar energy for heating and lighting. According to Yakubu, basically, passive solar building design utilizes the form and fabric of building to collect, store and distribute solar energy. With passive system, the method of collection of solar energy is simple. Orientation of the house due south with large windows exposure is sufficient. The exact amount of heat gained depends upon climatic conditions, the latitude and the amount of the insulation used (Yakubu, 1996). Pitts, discussed that, passive solar design can be defined as the optimization of building form, orientation, materials structure and glazing area to make the best use of available solar energy both to offset demands for heating during winter and to avoid overheating during summer (Pitts, 1994).

4.2.2- Active design system Active system is the use of solar collecting panels, storage units, energy transfer mechanism and energy distribution system. This type of system always uses one or more working fluids, which collect, transfer, store and distribute the collected solar energy. Basically, there are two different systems: firstly, the electrical system, the use of photovoltaics in converting solar energy into electrical. Secondly, the thermal system, in which the solar energy is converted into heat. Different applications of the active system were mentioned before and this chapter will study the integration with building.

4.3- Integration of Solar Systems with Buildings PVs can influence the building’s orientation, layout and form; they will affect the building fabric and will be an important element of the environment and building systems. They need to be considered as an integral part of the energy strategy of the building and of its functioning. Appearance and aesthetics are, as ever, especially important (Thomas R. et al., 2001). Building integrated solar systems have some advantages:

- The building becomes a net energy producer; the environmental effects of electricity distribution are reduced. - By utilizing the existing unused areas of a building, there is no additional requirement for land to install panels. - The cost of the solar applications can be offset against the cost of the building element it replaces. Some factors must be considered in the integration of solar systems with building: Building type: A wide range of buildings can use the solar system (residential- industrial- services buildings). The type of building, occupancy of building and load determines the needs of solar energy then the size of collectors and equipment used. Building site: the location of the site is obviously important, as well as, the topography of the site. Orientation of building in site must have right accesses to solar radiation. In addition to that overshadowing of the building by other buildings (fig.13) or by high trees may affect the efficiency of the solar system.

46% of unshaded output41° horizon

41°

15° horizon83% of unshaded output

15°

36% of unshaded output

50°

50° horizon

30°

61% of unshaded output30° horizon

Fig. (13): Shading Effects by Neighbouring Buildings Source: (Thomas R. et al., 2001)

4.4- Integration Options

Solar panels have their own visual impact and contribution to the external appearance of a building. There are options of integration of solar panels; firstly, direct integration within building or building integrated solar applications. Secondly, indirect integration where solar collectors are fixed outdoor within the building site without direct contact with the building. In other word, these could be named building attached solar applications.

4.4.1- Integration within Building: According to Thomas R. et al., there are three ways for integration of solar panels within a building (Thomas R. et al., 2001): Roof based system: Roof can be the best site for solar panels; firstly, because they are often free from over shadowing, it can be inclined with selected slope for high performance and it may be easier to integrate collectors aesthetically safely and functionally into roof than a wall. Solar panels can integrate as inclined roof or as a part of inclined roof. Also, as pitching roof (fig.14).

Roof with integrated tilesInclined roof Curved roof Atrium

Fig. (14): Different Alternatives of Roof Integration

Photo (11, 12): Roof Integrated Solar Panels Roof integration is convenient to both solar collectors and PV panels, except in case of curved roof, which is most convenient to PV panels. Façade system: most of modern buildings have glazed façades, despite that it is not preferable in a hot dry climate due to the impact of glazing (green house effect), but proper orientation and good design can confront most of this problem (this is beyond the study). The glazing in façade can be replaced by the solar panels and have same result. In addition to appearance, it supplies buildings with energy used in many facilities. Senug, pointed that, in the past, architects have tended to use glazed facades mainly for aesthetic reasons, but in fully glazed facades, the heat losses tend to be excessive, and the energy consumption for cooling in summer becomes critical. Consequently, double-building skin is being developed, then if a building skin is properly designed, these can be made to convert not only solar energy but electricity as well (Senug –2002). Solar panels can be integrated as vertical or inclined curtain walls or inclined collectors with windows (fig.15).

with windowsInclined panelsVertical Vertical with windows Inclined walls

with windows

Fig. (15): Different Alternatives of Façade Integration

Photo (13, 14): Façade Integrated Solar Panels Façade integration is convenient only to PV panels, because the main features of PVs used as a cladding material are basically the same as tinted glass. Sunshades: Solar panels can integrate as sunshades with windows canopies (fig.16). With the increasing use of large window openings and curtain walls in today’s architecture, there is a growing need for carefully designed shading systems. Windows must be shielded from direct radiation and glare. Solar panels can be perfectly mounted on shading devices, either

fixed or moveable, and it can work in two ways, energy supplier and shading units.

Fixed sunshades Moveable sunshades

Fig. (16): Different Alternatives of Sunshades Integration Sunshade integration is convenient to both solar collectors and PV panels.

4.4.2-Integration within site: Solar panels can be mounted outdoor in courtyards with different layouts for example, in a verandah within a garden or around a swimming pool or as a shed for car parking.

4.5- Summary This chapter explained the process of building design, the importance to achieve comfort by proper design and the need to deal with the new technologies. Different approaches of solar energy to building were discussed briefly, the integration of solar appliances with building, factors to be considered in the integration and different options of integration. The following chapter will study and analyze the integration of solar application with buildings in Sudan with special emphasis to buildings in Khartoum, and draws an overview of solar technology uses and its acceptance in Sudan.

CHAPTER 5 SUDAN SOLAR TECHNOLOGY 5.1- Introduction

As mentioned before, in Sudan increasing attention is given to the utilization of the solar energy. Several solar applications have been carried out. To make use of these applications, they must be integrated with the building directly or indirectly according to many factors. Applications for buildings integrated solar panels are essentially unlimited. Solar panels can be integrated with every conceivable structure from car parking shed to high rise office building. Solar technology is also appropriate for all buildings types. In this chapter there is an attempt to distinguish the possibility of the integration of solar panels/applications with different types of building with special emphasis on buildings in Khartoum. In other words, to study the ability of buildings in Khartoum to accept solar technology, as well as factors that determine the way that solar panels can be integrated. Moreover, it is important to know the application of solar panels in Sudan, the solar panel and applications industry in Sudan and examples to express the use of solar applications.

5.2- Applications of Solar Panels in Sudan Most attention, in the solar applications field, is given to solar photovoltaics more than solar collectors and solar thermal applications. Most people seem to think that a solar collector means a solar PV due to the widespread of PV commercialization. In Sudan, most uses of solar applications are in rural areas where there is acute shortage or lack of energy (Appendix 1). Most of these projects are financed by NGOs. Use of solar PVs is normally for lighting and vaccine refrigeration and the use of solar thermal applications is mostly for cooking and distilling. Lately, Sudan government started to finance the projects of rural electrification by using solar PVs (The project of electrification of 1000 villages by using PVs).

In Khartoum, solar PVs are used in some private houses as backup systems. Solar energy is still expensive compared to other grid energy sources. Now, after the recent decreasing of the customs on solar PVs, an increase in the use of solar PVs is expected. Treatment of solar panels as a part of building is still unstudied. Mounting of solar panels in most buildings is not properly planned, nor according to any architectural standards. Following photographs (photo. 15, 16) express the improper integration and mounting of solar panels:

Photo. (15): Solar Panel Mounted At the Top of a Building Improper mounting leads to breaking the integrity of the building. Secondly, fixation of the solar panel on a steel pipe is not enough to resist the lifting effects of strong winds.

Photo. (16): Solar panels mounted outdoor *incompatible appearance of solar panels and the fence.

5.3- Solar Applications Industry in Sudan Integration approach of solar applications with buildings must take into account the production system of solar panels that result in improving efficiency and appearance of panels. Panels shape, color and texture were offered as enhancement to the aesthetics of panels that have influence on the building. Additional care must be given during the production process of solar panels to the materials used, efficiency, thermal performance and appearance. Solar industry in Sudan is still in its preliminary stage. Some of solar thermal applications like solar cookers, solar distillers are carried out by groups or individuals. Production process uses local materials that lead to cost reduction. Thus, it can be available to use in rural areas. Also, Ministry of Science And Technology has recently started a small factory for solar cells assembly, which started to produce solar modules. Solar industry in Sudan requires major efforts to be promoted to the level of the commercialization. One of the reasons that affect the consumer acceptance is the appearance of solar panels beside the performance and the cost.

5.4- Examples from Sudan

In the Sudan, the use of solar applications especially photovoltaics is growing significantly, mostly in the remote areas that suffer from energy shortage.

5.4.1-Sudatel The continuity of electrical power is important in telecommunication and monitoring systems. A power outage can mean the loss of valuable data or the in ability to communicate. As a result, photovoltaics are a viable solution especially in remote areas. Recently, Sudan telecommunication company (SUDATEL), started to use photovoltaics to power the telephone communications in the satellite stations surrounding major urban areas. This way, the telephone network has become extendable to rural areas where there is no electricity supply. Using solar photovoltaics in these areas leads to wide awareness and willingness of inhabitants to utilize this technology.

5.4.2- Rural Electrifications Different organizations provided a framework to introduce effective and sustainable use of solar energy resources to improve services and to strengthen the economy of poor rural communities. Most of rural areas suffer from inadequate energy supplies and low coverage of the electricity grid. Photovoltaic technology was widely implemented in many of Sudan rural areas that are not supported with the required services and the police, army and customs points in the geographical boundaries. In rural areas, PV systems were installed in schools and learning centers. They were also used to power refrigeration systems, lighting and communication systems and water pumps. Following photographs (photos. 17, 18, 19) show examples of different uses of PVs in Kordofan state:

Photo. (17): Use of PVs in Schools in Kordofan State Photo. Above is for Kanalle School for Swedish – Sudanese Friendship- Bara Town.

Photo. (18): Use of PVs in Schools in Kordofan State Photo. Above is for School in remote area in Kordofan, the use of PV is for lighting.

Photo. (19): Solar Water Pumping Photo. Above is for one of the village in the Swedish project near Bara Town, enjoying a solar water pumping set. 5.5- The Study

5.5.1- Approaches to integration study: Integration of solar applications with buildings concerns both solar applications and the buildings. To determine if solar systems can be properly integrated with buildings, it is important to start with an over view and analysis of these two parts in terms of aspects related to the integration. A/ Solar applications: Solar applications whether thermal or PVs can be divided into:

-Outdoor units: include all components that need to be outdoor, which are mainly the solar panels (solar collectors or PVs array) and component related to them. Solar panels affect the appearance of the buildings, therefore, they need to be considered as an integral part of buildings. -Indoor units: include appliances, small items and wiring.

-connecting units: connect between indoor and outdoor units. They include other components like cables, pipes, control units, and pumps. These units can be outdoor or indoor, but they must be shaded and protected from climatic changes, especially the control units. In small buildings, a control cabinet can be used to protect these units. While in large buildings, a plant room space is required for control units and associated equipments. Ideally the plant room will be as close to panels as possible for ease of routing and minimize energy losses in cables. The room needs to be ventilated.

-should generally be inaccessible to

-Need to be exposed to the sun

occupants but accessible to maintenance

and avoid over-shadowing

-Important to blend surface, colors-Proper fixation and right orientation

solar collectors/PVs

of panels with building features

cables/control units/pipes/auxiliary pumps

Load

Connecting units

Out-door units

In-door unitsappliances/wiring-wiring needs to be hiden from normal view

-plant room and ducts can be used toprotect these units

-appliances in the right location for use

Fig. (17): Solar System Components Panels Fixation: For integration of solar panels with buildings, support structure or carrier will be needed to help in the fixation process. The support is fixed directly to the building structure either on roof or wall by bolting or welding it with existing structure. Panels are already provided with holes for bolting and fastening.

solar panels fixed to support structure

weld or bolt

support structure fixed to the building structure by

support structure air

building structure

Fig.(18), Photo (20): A Simple Way of Panels Fixation

Fig. (19): PVs Fixed in Wall B/ Buildings: There is a large diversity of buildings types, constructions techniques and materials used. To determine the suitability of the integration, it is necessary to know information on each. The following table (table 4) represents different types of buildings and the most common materials used in construction and the techniques used in Sudan.

In assessing the suitability of integration process, many factors must be considered. Each factor interferes with the others, therefore, these factors need to studied together to come out with the optimum system.

APPLICATIONS SOLAR

RESIDENTIAL BUILDINGS

APPLICATIONSCOST

SOLAR

INTEGRATED

OTHERS

AGRICULTURAL BUILDINGS

INDUSTRIAL BUILDINGS

SERVICE BUILDINGS

BUILDINGS

BUILDINGS

TECHNIQUES

OUTDOOR UNITS

CONNECTING UNITS

INDOOR UNITS

AESTHETIC

Fig. (20): Integration Process Cost: solar applications are currently an expensive technology. It is important to use them as optimally as possible. Aesthetics: positive influence of panels on buildings is required. Unstudied installation of panels leads to negative impact on the appearance and breaks the integrity of the building. Technical consideration: the integration of solar applications with buildings should be considered in terms of installation and fixation. Installation must be compatible with the building structure. Panels need to be accessible for maintenance. Others: include safety, accessibility, right orientation, performance, etc.

5.5.2- Factors That Determine Integration Options

FACTORDAYLIGHT

TYPE

STRUCTUREBUILDING

INTEGRATION

OFBUILDING

OCCUPANCY

OPTION

BUILDING

SIZEBUILDING

Fig. (21): Determination of Integration Option Building’s type, size and occupancy of building determine its energy demand. Energy demand is different from service buildings to industrial buildings to residential buildings and even between different types of houses. In residential buildings, low energy demand is expected compared with other buildings and in different categories the lowest demand is expected in the first group (photo. 21) and it rises with the increase of the standard of living. In service buildings the high numbers of occupants require a high supply of energy, as well as, industrial buildings where the industrial process depends mainly on energy. However, in most cases, use of solar energy is restricted in these situations to lighting and low energy appliances.

Energy demand determines the number and size of solar panels, which will be needed. Buildings with high demand of energy require large areas of panels to collect a great amount of solar radiation to satisfy the needs. Number and size of panels define best option of integration; whether solar panels can integrate as a roof, fully or partially, or as a façade, part of glazing façade or windows, or as sunshades. In buildings with high demand of energy like service buildings façade/roof integration can be optimum, while in low energy demand buildings like houses integration can be as a part of roof or sunshades. To determine best option of integration, the daylight factor must be considered. There is a need to study daylight to determine the area, which is best for mounting panels, either roof or wall. The building structure determines the way of integration. Weight and load of solar panels on the building require a support structural system.

5.6- case studies The study of the integration of solar applications with buildings in Khartoum, in particular, concern with the exist buildings because it is expected that most of these buildings will use these technology. In addition, in existing buildings we need to look carefully for most convenient spaces for panels to be integrated without interfering with other building's function and breaking building integrity. The integration of solar applications with new buildings is more flexible and can be involved in the design process. The first task, then, in the study of the integration of solar panels with buildings in Khartoum, in particular, is to divide buildings into categories, then select one from each category as a study case. Three categories of buildings are considered: Service buildings: From different service buildings in Khartoum, office buildings were selected as a case study. The majority of new office buildings in Khartoum are multi-stories buildings.

Industrial buildings: factories and workshops. Double pitched roof with steel structure and brick wall is a most common shape of industrial buildings in Khartoum. Residential buildings: In Khartoum, there is segregation of housing according to the income group. The following Photographs (21, 22, and 23) show the variations in size and materials of houses in Khartoum.

Photo (21): First Group of Houses The first group is made of “unburnt” Green bricks, galoos, and sometime red bricks, with a traditional roof made of palm logs and leaves in most cases.

Photo (22): Second Group of Houses

The second group, which is wide spread, is houses with red brick walls and zinc sheets roof. Verandas are quite common.

Photo (23): Third Group of Houses The third group is the Reinforced concrete houses, with reinforced concrete roof-slabs. The study takes a sample of each category and makes a general analysis to samples as a preliminary study for existing buildings integrated solar applications. More detailed studies are expected in the following years due to the expected increase of solar applications uses.

5.6.1- Case study 1- Houses group1 Study of integration options: In the first group of houses, which is mostly made from galoos, it is expected that direct integration with building is difficult. The integration of solar panels with roof is difficult because the materials used in the traditional roof are not strong enough for mounting solar panels.

zibala

galoos or mud brick wall

mirigrassas

fallakab or gareednal

earth

Fig. (22): Section through a Traditional Roof From the section above fig. (22), it is clear that it is difficult to weld or bolt for mounting a solar panel frame on rooftop, due to the nature of the materials used. At the same time it is difficult to fix collectors as windows or sunshades on the wall, which is made of galoos.

Suggested options: In this type the integration can be as a separate structure system. Solar panels can be mounted on the ground, closed to building as a veranda with a separate structural system as shown in fig. (23a), or as out door shed as shown in fig. (23b), most of these houses enjoy large courtyards between buildings.

(a) Use of solar panels as a roof of verandah in front of building

(b) Use of solar panels as a roof of a shed in the courtyard

Fig. (23): Suggested Options of Integration

Analysis: Suggested options of integration require a separate system of structure to mount the panels. Then, panel's integration becomes expensive and increase in the cost is, however, beyond means of the inhabitants. In addition, merging of this shed with galoos visually is an architectural challenge, due to the wide variation of building materials. At the same time, fixation of the ground leads to many problems; firstly it is unsafe for panels. In addition, it interferes with other out space usage like outdoor sleeping which is one of inhabitant needs in Khartoum. Conclusion: In this group of houses individual mounting of solar panels for each house is not the optimum solution, due to the high cost of support system.

The cost is important factor here. A detailed study is needed for the Collection systems of solar panels of many houses and distribution of the energy produced to each house.

5.6.2- Case study 2 - Houses group 2 Study of integration options: Integration in the second group of houses is easier than the first group. Building materials used in the second group are stronger. This type of houses provided with different spaces for integration beside roofs like sheds, windows canopies and verandahs. Suggested options: In roof integration, solar panels can be mounted on roof top or as integral part of the roof, partially or fully. There is a need for a sub frame for mounting the panels onto the rooftop.

Fig.(24) photo.(24) Fig.(24), Photo (24): Solar Panels Mounted on Rooftop Façade integration is undesirable because people can misdeal with the panels. Existing verandahs roof, sun shades and window canopies can be integrated with solar panels if they are strong enough to carry the panels.

Fig. (25) Photo. (25) Fig. (25): Mounting Of Solar Panels on a Veranda’s Roof Photo. (25): Example of Second Group of Houses

Photo. (25) Shows a common view in Khartoum houses, use of a veranda in front of house. Analysis: Roof integration leads to partially or fully double roof that is most appropriate in hot climates and has its advantages. At the same time, double roof has a positive influence to the buildings appearance. Mounting of solar panels on top of a roof leads to reduction of solar radiation received to the roof and utilizes this radiation and converts it to energy, as well as allowing a ventilated air space between the two layers will prevent heat from being transmitted to the inside, (fig. 26). This will also help cooling the panels that will otherwise reach a high temperature.

Air current

Fig. (26): Ventilated Air Space between the Roof and Panels

In mounting solar panels, existing structure in the building can be used. Veranda’s roof can be optimum to replace by solar panels, but it is important in installation process to avoid any matter that affect the panel's performance like over shadowing by buildings and rainwater falling from the roof (photo. 25). This solution can help in reducing the installation cost which is important factor in this type. Conclusions: This type of integration can be carried out in verandas, sheds, shelters, garages and any convenient existing structure. In most of Sudanese houses there is a verandah close to the kitchen. Verandas roof can be merged with solar collectors to provide the kitchen with hot water, as well as PVs. Roof integration is safer in houses and need to be accessible.

5.6.3- Case study 3 - houses group 3 Study of integration options: In the third group of houses mounting of solar panels is more convenient. Use of reinforced concrete helps in fixation of solar panels.

Flat concrete roofs, which are most common in this type, have the advantages of good accessibility and ease of installation. Pitched or arched roofs can be also proper for mounting solar panels. Suggested options: Solar panels can be integrated as a second layer of roof, as well as integral part of the light roof. Solar panels can be integrated as sun shades above windows.

Photo. (26): Mounting of Solar Panels on Rooftop Photo. 26 show Solar panels integrated in the roof top as a partial double roof without making negative impact.

Photo. (27) Photo.(28) Photo. (27): Example of Third Group of Houses

Photo. (28): Integration of Solar Panel as Integral Part of Roof Photos.(27) show a common view in the third type of houses in Khartoum- Use of a second layer of a roof top of the last floor or a light roof on the last floor. Solar panels can be an integral part of the light roof as shown in (photo. 28), where there is match between the panels and building features. Analysis: On flat roofs, the classical way of integration has been to mount the panels on a substructure which is then fixed to the roof (photo. 26). Fixing of panels on a stable horizontal roof plane leading to partially or fully double roof that is also recommended. Double roof provides the building with a cooler internal environment that is already suggested in hot dry climates as mentioned before. Usually, the double roof has a lower heavy portion with a reflective upper portion. Hence, in case of solar panels, the upper portion can be collective solar panels.

Installation of panels in pitching roof is similar to that in the flat roof, but special care must be given to the mounting of panels without breaking the integrity of the roof and to the added weight on the roof. Pitching roof has its advantages in hot climates as mentioned before. If roof panels are used, panels can be replaced with solar panels. It is important to combine solar panels with the other panels by using compatible color and surface (photo.28). Direct mounting as integral part of the roof can actually increase roof temperature and may require increased ventilation to offset thermal gains. The use of solar panels as a shading system does not exert any heavy load on the building structure. Since many houses already provide some sort of structure for shading windows, solar panels can be mounted on the existing window canopy or it can replace Marseille tiles, which is most common.

Conclusions:

This type of houses considered as the type in which more demand of solar applications is expected. Their inhabitants look for other alternatives of energy supply. Stand by generators are quite a common phenomena in this type of houses, but it is not very efficient because long period of electrical cut, as well as the noise and pollution generated from it. There is a need to calculate the exact cost of energy from generator and make a comparison with the exact cost of same amount of energy generated from PV panels. Even with high cost solar panels are optimum if environmental cost is added.

5.6.4- Case study 4 - Industrial buildings Study of integration options: Integration of solar panels with industrial buildings like factories, workshops and large stores, is simple. The type of structure used in these buildings is suitable for panels' fixation. Truss roofs are common in most industrial buildings. Most of industrial buildings in Khartoum have double pitched roofs. Solar panels can integrate as roof sheeting or as a second layer of roof. Industrial buildings are unsuitable for façade integration because the nature of the industrial processes makes the use of panels in façades unsafe.

Suggested options: Industrial buildings roofs by its different shapes can accept fixation of solar panels. Direct or indirect integration of solar panels with roof seem to be the best option of integration.

Double-pitched Roof

Monitor Roof

Mono-pitched RoofGlazed window

Fig. (27): Different Configurations of Industrial Buildings Roofs

Analysis: Using solar panels as an integral part of the roof leads to decreasing the total cost of the system. The double roof system, in addition to the improvement of internal environment, adds to the aesthetical value of the building. Use of monitoring roof is desirable. Long extension of these buildings makes it rigid and bulky. Therefore, monitoring roof designed with different shapes breaks this rigidity, although it leads to increasing of structural complexity and cost. Moreover, using glazed windows in the vertical part of roof allows day light to penetrate into the building and provide the building with the natural lighting and ventilation.

X

Daylight

X

Shading Daylight

(A) widely spaced monitoring roof (B) Closely spaced monitoring roof

Fig. (28): Different alternatives of monitoring roof In mounting of panels over monitoring roof, it is important to locate the panels in the right orientation and to assess sufficiency of space between units of the monitoring roof (fig. 28A), to avoid overshadowing of panels (fig.28B) which is not recommended. Conclusions: In industrial buildings, different shapes of roof can accept panels installation. This can be same with the all long extended buildings and small work shops and stores.

5.6.5- Case study 5 - Office buildings Study of integration options: Office buildings, especially multi-stories ones, accept the different options of integration. The application of solar energy into a building often depends on its ability to be integrated into common buildings structure. Solar panels are just added on to the structure. Suggested options: Solar panels can be mounted on the unused top of the roof as a second layer, partially or fully. Integration of solar panels with buildings can go parallel with modern trends of architecture, like using of glazing facades that is most common in office buildings. Glazed panels can be replaced with solar panels.

Photo. (29, 30): Office Buildings in Khartoum Photographs above (photos.30, 31) show some of new office buildings, which have glazed facades in Khartoum. The use of glazing is not recommended for hot climates due to the greenhouse effect, despite that many of new buildings in Khartoum have glazing panels. Use of glazed façade increase amount of energy needed. The use of solar panels instead of glazing panels can solve some problems of the glazed facade. Inclined walls can be also proper for PVs istallations, as well as sunshades. Analysis: Using solar PV, as a glazed façade, cannot be for aesthetical reasons only but it can provide the building with energy for cooling, heating and also electricity. This can be achieved by replacing some of the glazing panels by solar panels according to the needs. In using solar panels, it is important to assess the effect of surrounding buildings in terms of shading of façade (fig. 29).

15°

X

shaded area

Fig. (29): Effect of Surrounding Buildings It is necessary to avoid mounting of panels in the shaded area. Also, distance(X) between the building integrated solar panels and surrounding buildings must be considered. A maximum unshaded area is required. Integration of solar panels with facades requires using materials of high quality and neat panels to have a fine appearance. Therefore, PVs are the solar panels that can be integrated as curtain walls. Amorphous silicon modules, both opaque and semi-transparent are commonly used. In inclined glazing walls PV out put is improved compared with the vertical ones, in addition to that inclined walls potentially enhance architectural interest. Conclusions: Office buildings are considered to be the most promising building type for PV façades. This is because there are large areas of façades available and the demand for electricity is more closely matched to the availability of sunshine than for residential buildings. As well, panels utilize existing unused areas of building façades rather than taking up valuable land area, since, most of the office buildings are normally located in the center of the city or in valuable plots.

5.7- Summary Solar technology are advanced technology that help in designing buildings which are environmentally friendly and exciting. If they are applicable, they need to be part of the initial building concept and must comply with the architect's design needs, as well as the engineer's functional ones. A study of the integration of solar applications with buildings in Khartoum was presented. This study takes a sample from different types of buildings as a case study. In each type, it distinguishes problems that confront the integration, suggests some options of integration and makes an analysis for these suggestions to conclude with an optimum integration option. It is clear that, the cost is an important factor in the integration process especially in residential buildings. In first type of houses, where the structure cannot carry the panels. That requires, therefore, using a separate structure which leads to increase of cost. Increase of cost is not advisable in this type.

At the same time, technical considerations play an important role in determining integration option. Capability of building structure to carry solar applications lead to reduce in installation cost. In the second type of houses, the acceptability of its structure to carry panels helps in reducing the total cost of installation. One of the advantages of solar panels is its capability to be mounted on existing structures. Almost, different buildings in Khartoum have a sort of structure that can be convenient for fixing of solar panels. The challenge is to create added values to the panels and the building itself with the optimum cost, high performance and safety installation of panels. Another challenge that will face the architect in the coming years is the incorporation of solar applications with new buildings. In the existing buildings the integration is restricted according to the existing situation, while in new buildings integration options are unlimited. Solar applications provide a chance for buildings to become more dynamic, therefore, different changes in architectural concepts will be expected.

CHAPTER 6 CONCLUSIONS AND RECOMMENDATIONS 6.1- Introduction

Solar energy technology components are essential for a sustainable energy supply. Solar technology is today a popular part of the buildings vocabulary. It can be used on both existing and new buildings. As result goals, specifications, and design of buildings need to be changed and modified to accept this technology. The integration aspects of panels need to be fully understood and researched. It can’t suffice to simply replace existing building elements by those, which additionally incorporate solar elements. The integration must always be planned in the context of the buildings as a whole. An overall energy scheme must be developed for the building right at the beginning of the construction project, when the building size, shape and orientation are being made. In other words, energy demand should be considered as one of the main space requirements that need to be solved architecturally from the beginning. The integration requires a study by experts, architects and buildings engineers fully collaborating in the building design process. Moreover, industry performance and selection of advanced glazed materials are required for a higher degree of achievement.

6.2- Basic Recommendations for Solar Panels Mounting Roof Mounting: It is recommended, when solar panels are mounted on the building roof to have:

- A space between the panels and the roof surface, or use of panels as a second layer of the roof to allow for air circulation and to prevent excessive heat buildup. Double roof is recommended in hot dry climates as mentioned before.

- Avoid overshadowing of solar panels by the neighbouring buildings. In Khartoum, Building regulations state that the minimum distance of any house should be at least at 1.5 m from the

separating wall from east and west neighbours and one third of height from north and south neighbours, where there is no road.

- Access for regular cleaning and maintenance. - Enough fixation of panels to resist the lifting effects of the strong

wind if affecting the area. "In Kordofan state, recently, strong wind led to large damage of PVs systems in many buildings".

Façade Mounting: If the façade mounting is chosen, it is recommended:

- Basic information of façade exposure must be kept in mind while locating solar panels:

From the northern side, solar radiation is the minimum. The exposure of east and west sides to solar radiation is only in half of day. From the south, minimum solar radiation is during summer that is why people tend to open their windows on the southern side. The prevailing wind, summer breeze, also comes from a southerly direction. Solar panels must be located without interfering with other matters.

- Avoid mounting of panels in shaded areas of façade. Sunshades Mounting: Using of fixed solar sunshades is recommended, in case of using solar panels as shading devices. Using of fixed or movable shading devices is according to climatic conditions. Movable sunshade use is to track sun radiation. Therefore, most use of movable shading devices is in contexts that do not enjoy continuous supply of solar radiation during day. In Sudan, which possesses a relatively high abundance of sunshine, fixed shading systems can collect enough solar radiation. Use of movable sunshades increases the complexity of construction that leads to an increase of cost. The only exception, is the buildings that need to be different and the cost is not important factor.

6.3- Guidelines for Building Integrated Solar Applications Office buildings: In the multi stories office buildings, façade integration is recommended as a first choice, because of large unused areas of façades and the widespread of glazed façades in this type.

Roof integration is also recommended especially in buildings not using glazed façades. Rooftop usually enjoys large unused areas. Industrial buildings: The roof mounted system is recommended in industrial buildings. Roof is more safe to solar panels than other options. Façade Integration is undesirable because the nature of industrial buildings doesn’t accept glazed façades. Residential buildings: In different types of houses, roof integration-directly or indirectly- is recommended. Solar panels on roof are safer from improper use and other risks; rooftop is relatively out of reach. The only exception is the first type of houses, it is recommended to use a collective system of solar panels for neighbourhood's houses. Panels mounting cost is an important issue for this group of inhabitants.

6.4- General Guides There should be a good match between the building’s energy demand pattern and the energy available from the panels. This match can be achieved by correct calculation of solar panels needed. There is a need of a computerized programme that contains tools of solar cells calculation to help in calculating needs of each building and the size of the cell. Using a computer tool has several advantages: (a) using such a tool is easy and fast, therefore it is possible to study and evaluate several design alternatives for building orientation and geometry; (b) the model can be used for any geographical location; (c) the determination of the critical date and time is not an easy task, especially when the building plan is not rectangular and is rotated from the north-south axis, by using the computer model this process is automatically done (Capeluto, 2002).

6.5- Further Studies Buildings can incorporate passive solar systems, active solar systems (thermal applications, solar PVs) and day light. To achieve this, detailed studies for specific buildings are needed. This requires knowing the exact energy needed for a building to calculate solar panels needed and define

the proper way of integration. In addition, detailed information of climatic characteristics and sun movement in the building context is required. Climate affects building orientation, opening spaces and materials used.

6.6- Concluding Remarks Solar energy promises to be the optimum energy source in Sudan that can meet some of the energy demand. Sudan has an excellent annual mean solar radiation of 5.44KWh/m²/day throughout the year. Encouragement from government is needed for promoting research and development, demonstration of clean, safe and abundant energy sources. Moreover, there is a need to make people aware of the destruction of the natural environment and problems of conventional energy sources. Government support is needed to make solar applications accessible for all. This can be achieved by support of local manufactures to develop cheaper and efficient solar applications, and decreasing of the customs of the exported materials that are used in the manufacturing process of the solar applications. Decreasing of cost increases the public perception of this technology and makes it competitive. Architectural integration of solar appliances with buildings requires flexibility of design to implement this technology. Close collaboration among all the people involved in the design process of a building is necessary. The goal is to have a “whole building perspective”.

References:

Capeluto G.(2003), Energy Performance of The Self Shading Building Envelope, Energy and Buildings, Vol.35, pp.327-336. Eltom O. M.(1998), Solar Thermal Refrigeration Systems Experience of Energy Research Institude, ERI, Sudan. Eltom O. M.(1993), Solar Refrigeration Applications in the Sudan, PhD thesis, University of Reading, UK. Fathi, H. (1986), Natural Energy and Vernacular Architecture, University of Chicago press, Chicago and London. Garg H.P. and Prakash J.(1997), Solar Energy Fundamentals and Applications, Tata Mc Graw-Hill publishing company limited, India. Givoni, B. (1994), Passive and Low Energy Cooling of Buildings, Van Nostrand Reinhold, USA. Goossens, D and Kerschaever, E. V. (1999) Aeolian Dust Deposition on Photovoltaic Solar Cells: The Effects of Wind Velocity and Airborne Dust Concentration on Cell Performance, Solar Energy Vol.66, No.4, pp. 227-289.

Hankins M. (1995), Solar Electrical System for Africa, common wealth science council, UK. Hagemann I. (1996), PV in Building- The Influence Of PV on The Design and Planning Process of A Building, Renewable Energy, Vol.8, part I, pp.467-470.

Hamour, W. B. (2001) Architectural Integration of Photovoltaics in Hot-Dry Climates, Viability And Constraints, M.Sc. thesis, University of Sheffield, UK. Omer, A. M. (1998), Sudan Energy Background; an Overview, Renewable energy Vol.14, Nos.1-4, pp. 467-472. Omer, A. M. (1994), Renewable Energy Technology Applications in The Sudan, Renewable Energy, Vol.5, part П, pp.1394-1397. Posorski R. et al.(1986), Survey on the Hot Water Demand of Khartoum Household, ERI, Sudan. Pitts A.C.(1994), Building design: Realizing the Benefits of Renewable Energy Technology, Renewable Energy, Vol.5, part П, pp.959-966.

Ratti C. et al.(2003), Building Form and Environmental Performance: Archetypes, Analysis and an Arid Climate, Energy and Buildings, Vol.35, pp.49-59. Sam C. M.(2000), Low Energy Building Design in High Urban Cities, World Renewable Energy Congress VI- Brighton- UK. Seung H.Y. and Lee E.T.(2002), Efficiency Characteristic of Building Integrated Photovoltaics as Shading Device, Building and Environment, Vol.37, pp.615-623. Taha A. Z.(1989), The Solar Energy in the Sudan, ERI, Sudan. Tiwari G.N.(2002), Solar Energy Fundamentals, Design, Modeling and Applications, Narosa Publishing House, India. Thomas, R. et al.(2001), Photovoltaics and Architecture, Spon press, London.

Tombazic, A. N. (1994), Architectural Design- A Multi Faceted Approach, Renewable Energy, Vol.5, part П, pp.893-899. Yakubu, G. S.(1996), The Reality of Living in Passive Solar Homes: A User-Experience Study, Renewable Energy, Vol.8, part I, pp.177-181.

* Plan is not to scale NORTHERN KURDOFAN STATE

Hamrt Elwiz

Solar RefrigeratorsLighting

KEY:

El-Obied

Bara

Hamrt Elsheikh

Um-Bader

Sudary

Um-Ruwaba

El-Rahad

Solar Pumps

Locations of Using PV Technology In North Kordofan State

SOUTHERN DARFUR STATE* Plan is not to scale

Rihaad Elbardi

Niala

Solar Refrigerators

KEY:

Lighting

CENTRAL AFRICA REPUBLIC OF

WESTERN DARFUR STATE

Kas

BAHR ELGHAZAL STATES

Buram

NORTHERN DARFUR STATE

Solar Pumps

LLooccaattiioonnss ooff UUssiinngg PPVV TTeecchhnnoollooggyy iinn SSoouutthheerrnn DDaarrffuurr SSttaattee

AAppppeennddiixx ((11--11))

* Plan is not to scale

Solar RefrigeratorsLighting

GEDAREF

GEDAREF STATE- CENTRAL BUTANA

El Subagh

El Bugah

GEZIRA STATE

Geili

El Ideid

KHARTOUM STATEKASALA

GEDAREF STATE

El HsheibEl Takoon

Solar PumpsWind Pumps

LLooccaattiioonnss ooff UUssiinngg PPVV TTeecchhnnoollooggyy iinn GGeeddaarreeff SSttaattee

From the illustration plans it is clear that: - The most use of the solar PV is for lighting followed by solar

refrigeration, due to low coverage of the electricity grid. - Wide spread of using PV technology in Kordofan.

AAppppeennddiixx ((11--22))

SSoollaarr CCooookkeerr

- One unit solar thermal application, does not need to be integrated with the building.

- In solar cookers, light from the sun focuses onto one point then high temperature is obtained.

- Cook in a similar way to single hot plate. - Wide use in Sudan is in large communities, like prisons.

SSoollaarr DDiissttiilllleerr - Essential for the provision of water suitable for dinking, therefore

most use is in remote areas.

- Can be as one unit or with many components according to the needs. - Need to be integrated with buildings in large demanded buildings

like factories. AAppppeennddiixx ((22))