Swanepoel, C - Evaluating the Performance of Passive Solar Design Systems Through Modeling and Pr...

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Evaluating the performance of passive solar design systems through modelling and prototyping devices for northern facades in Climatic Zone 2, South Africa

by Cameron Swanepoel 216345126

Submitted in partial fulfilment of the requirements for the degree Master of Architecture in Architectural Technology (MArch) at the Department of Architecture and Industrial Design in the FACULTY OF ENGINEERING AND BUILT ENVIRONMENT at the TSHWANE UNIVERSITY OF TECHNOLOGY

Study leader: Prof J Laubscher Co-study leader: Mr S Steyn and Ms T Gaum

Pretoria January 2022

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DEPARTMENT of ARCHITECTURE and INDUSTRIAL DESIGN

DECLARATION ON PLAGIARISM The Department of Architecture and Industrial Design emphasises integrity and ethical behaviour concerning the preparation of all assignments.

Although the lecturer/study leader/supervisor/mentor will provide you with information regarding reference techniques and ways to avoid plagiarism, you also have a responsibility to fulfil. Should you feel unsure about the requirements, you must consult the lecturer/study leader/supervisor/mentor concerned before submitting an assignment.

You are guilty of plagiarism when you extract information from a book, article, web page, or other sources of information without acknowledging the source and pretending that it is your own work. This applies to cases where you quote verbatim and when you present someone else's work in a somewhat amended (paraphrased) format or when you use someone else's arguments or ideas without acknowledgement. You are also guilty of plagiarism if you copy and paste information directly from an electronic source (e.g., a website, e-mail message, electronic journal article, or CD ROM), even if you acknowledge the source.

You are not allowed to submit another student's previous work as your own. Furthermore, you are not allowed to let anyone copy or use your work to present it as their own.

Any student who produces work alleged to be plagiarised are referred to the Academic Affairs Disciplinary Committee for a ruling. Plagiarism is considered a severe violation of the university's regulations and may lead to your suspension from the university.

In accordance with Regulation 4.1.11.1(j) of Chapter 4 (Examination Rules and Regulations), and Regulations 15.1.16 and 15.1.17 of Chapter 15 (Student Discipline) of Part 1 of the 2021 Prospectus, I (full names & surname):

Shaun-Cameron Swanepoel

Student number:

216345126

Declare the following: 1. I understand what plagiarism entails, and I am aware of the university's policy in this regard.

2. I declare that this assignment is my own original work. Where someone else's work was used, it was acknowledged, and reference was made according to departmental requirements.

3. I did not copy and paste any information directly from an electronic source (e.g., a web page, electronic journal article or CD ROM) into this document.

4. I did not make use of another student's previous work and submitted it as my own.

5. I did not allow and will not allow anyone to copy my work to present it as their own work.

I further declare that this research proposal is substantially my own work. Where reference is made to the work of others, the extent to which that work has been used is indicated and fully acknowledged in the text and list of references.

06 January 2022 Signature

Date

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TABLE OF CONTENTS Acknowledgements .............................................................................................................. v List of figures ...................................................................................................................... vi List of tables...................................................................................................................... viii List of acronyms and abbreviations .................................................................................... ix List of definitions .................................................................................................................. x Abstract................................................................................................................................ 1 Chapter 1: Introduction ........................................................................................................ 2 1.2

Problem and its setting .............................................................................................. 2 1.2.1 Main problem statement ................................................................................. 2 1.2.2 Sub-problems and related hypotheses ........................................................... 3

1.3

Purpose of this study ................................................................................................. 3 1.3.1 Objectives ....................................................................................................... 3 1.3.2 Importance and benefits of this study ............................................................. 4 1.3.3 Researcher's qualification to investigate ......................................................... 4

1.4

Delimitations .............................................................................................................. 5 1.4.1 Assumptions ................................................................................................... 5 1.4.2 Limitations ...................................................................................................... 5

1.5

Research context ...................................................................................................... 5 1.5.1 Research paradigm ........................................................................................ 7 1.5.2 Research design ............................................................................................. 8 1.5.3 Triangulation research approach .................................................................... 9

1.6

Summary of Chapter 1 .............................................................................................. 9

Chapter 2: Literature review ............................................................................................... 10 2.1

Introduction ............................................................................................................. 10

2.2

Residential sector .................................................................................................... 11

2.3

Energy ..................................................................................................................... 13 2.3.1 Active solar ................................................................................................... 14 2.3.2 Passive solar ................................................................................................ 14 2.3.3 Thermal comfort............................................................................................ 15 2.3.4 Thermal mass ............................................................................................... 15

2.4

Passive solar systems ............................................................................................. 17 2.4.1 Trombe wall .................................................................................................. 17 2.4.2 Water wall ..................................................................................................... 19 2.4.3 3D printed modern Trombe wall.................................................................... 20 2.4.4 Thermosyphon effect .................................................................................... 21 2.4.5 Solar air heater ............................................................................................. 22 2.4.6 Light through water ....................................................................................... 23

2.5

Summary of Chapter 2 ............................................................................................ 26

Chapter 3: Pilot study......................................................................................................... 27 3.1

Water as thermal mass material .............................................................................. 27 ii

3.1.1 Methodology ................................................................................................. 27 3.1.2 Apparatus ..................................................................................................... 28 3.1.3 Background .................................................................................................. 31 3.2

Pilot study experiment ............................................................................................. 31 3.2.1 Introduction ................................................................................................... 31 3.2.2 Questions and hypotheses ........................................................................... 31 3.2.3 Design of the experiment .............................................................................. 32 3.2.4 Data analysis and interpretation ................................................................... 33

3.3

Conclusion .............................................................................................................. 34

3.4

Summary ................................................................................................................. 35

Chapter 4: Experiments and data representation .............................................................. 36 4.1

Introduction ............................................................................................................. 36

4.2

Experiment 1: Translucent qualities vs heat storage ............................................... 36 4.2.1 Questions and hypotheses ........................................................................... 36 4.2.2 Design of the experiment .............................................................................. 37 4.2.3 Data representation ...................................................................................... 38 4.2.4 Findings and conclusion ............................................................................... 39

4.3

Experiment 2: Translucent vs coloured water ......................................................... 40 4.3.1 Questions and hypotheses ........................................................................... 40 4.3.2 Design of the experiment .............................................................................. 40 4.3.3 Data representation ...................................................................................... 42 4.3.4 Findings and conclusion ............................................................................... 42

4.4

Experiment 3: Thermosyphon effect........................................................................ 43 4.4.1 Questions and hypotheses ........................................................................... 43 4.4.2 Design of the experiment .............................................................................. 43 4.4.3 Data representation ...................................................................................... 46 4.4.4 Findings and conclusion ............................................................................... 46

4.5

Experiment 4 ........................................................................................................... 47 4.5.1 Questions and hypotheses ........................................................................... 47 4.5.2 Design of the experiment .............................................................................. 47 4.5.3 Data representation ...................................................................................... 50 4.5.4 Findings and conclusion ............................................................................... 50

4.6

Summary of Chapter 4 ............................................................................................ 51

Chapter 5: Findings, conclusions, and recommendations.................................................. 53 5.1

Summary of research .............................................................................................. 53 5.1.1 Summary of Chapter 1: Introduction ............................................................. 53 5.1.2 Summary of Chapter 2: Literature review ..................................................... 53 5.1.3 Summary of Chapter 3: Pilot Study............................................................... 53 5.1.4 Summary of Chapter 4: Experiments ............................................................ 54

5.2

Chapter 4: Findings, conclusions and recommendations ........................................ 54 5.2.1 Sub-problem 1 and resulting hypothesis ....................................................... 55 5.2.2 Sub-problem 2 and resulting hypothesis ....................................................... 55 5.2.3 Sub-problem 3 and resulting hypothesis ....................................................... 56 5.2.4 Sub-problem 4 and resulting hypothesis ....................................................... 56 5.2.5 Sub-problem 5 and resulting hypothesis ....................................................... 57 iii

References ........................................................................................................................ 58 Appendices ........................................................................................................................ 61

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Acknowledgements I wish to acknowledge my supervisor, Prof. Jacques Laubscher for his guidance and support throughout the year.

Further acknowledgements go to my co-supervisor, Mr Stephen Steyn, for his valuable insight and time guiding me to the greatest extent, as this dissertation would not have been possible without his patience and guidance though the year.

I would like to thank my other co-supervisor, Ms Tariené Gaum, for assisting me with formatting and editing to complete this dissertation diligently and correctly.

Lastly, I would like to thank my family sincerely for putting up with me during this stressful time. Micke van Rensburg for your support and encouragement and Christiaan Eckard for your support and always checking up on me. It was an honour to share this journey with you.

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List of figures Figure 1: Energy demand by sectors (Government of South Africa, 2018) ........................ 11 Figure 2: Climatic zones of South Africa (SANS 10400-XA, 2011). ................................... 12 Figure 3: Thermal mass diagram of a Trombe wall and sunspace (Venturewell, 2013) .... 16 Figure 4: Trombe wall diagram (by MyPoolGuy) edited (Author, 2021) ............................. 17 Figure 5: Trombe wall diagram (MyPoolGuy) edited (Author,2021) ................................... 18 Figure 6: Trombe wall thermal mass setup (J.M.K.C, 2015). ............................................. 19 Figure 7: Sun-lite thermal storage tubes (Solar Components, 2019) ................................. 20 Figure 8: (Left) Double face 2.0, a geometrically optimised Trombe wall (TUDelft, Farrugia, E, 2018) ..................................................................................................................... 21 Figure 9: (Right) Double face 2.0, 3D model (TUDelft, Farrugia, E, 2018)......................... 21 Figure 10: Solar air heater (Fratzel n.d.) ............................................................................ 22 Figure 11: Types of DIY solar air heaters (Rimstar, 2005) ................................................. 23 Figure 12: Refraction of light in water (Science Learning Hub, 2012) ................................ 24 Figure 13: Refraction of light in a water bottle (Bansod, 2015) .......................................... 24 Figure 14: Bleach-and-water filled bottle light (Mae 2018) ................................................. 25 Figure 15: Indoor/Outdoor Thermometer with Hygrometer (Author, 2021) ........................ 28 Figure 16: Gemini Tinytag TGP-4020 (Author, 2021) ........................................................ 29 Figure 17: Gemini Tinytag TGP-4500 (Author, 2021) ........................................................ 29 Figure 18: Elitech RC-5 USB (Author, 2021) ..................................................................... 30 Figure 19: Modelled pilot study experiment (Author 2021) ................................................ 32 Figure 20: Photograph of pilot study experiment (Author, 2021) ........................................ 33 Figure 21: Water temperature measured during the pilot study (Author, 2021) ................. 33 Figure 22: Room temperature and humidity measured during the pilot study (Author, 2021) .................................................................................................................................. 34 Figure 23: Water temperature findings (Author, 2021) ....................................................... 34 Figure 24: ArchicCAD modelled experiment (Author 2021) ............................................... 37 Figure 25: Photograph of Experiment 1: Boxed water bottle with probe (Author, 2021) .... 38 Figure 26: Water temperature during Experiment 1 ........................................................... 38 Figure 27: Room temperature graph during Experiment 1 ................................................. 39 Figure 28: ArchicCAD model of Experiment 2 (Author 2021)............................................. 41 Figure 29: Photograph of pigmented water for Experiment 2 (Author, 2021) ..................... 41

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Figure 30: Water and room temperatures of the colour-pigment experiment (Author, 2021). .................................................................................................................................. 42 Figure 31: 3D model of Experiment 3 (Author, 2021) ........................................................ 44 Figure 32: Experiment 3 prototype (Author, 2021) ............................................................. 44 Figure 33: Photograph of prototype for Experiment 3 (Author, 2021) ................................ 45 Figure 34: Photographs of connections (Author, 2021) ..................................................... 45 Figure 35: Experiment 3 system temperature (Author, 2021) ............................................ 46 Figure 36: 3D model of Experiment 4 (Author, 2021) ........................................................ 48 Figure 37: Experiment 4 prototype (Author, 2021) ............................................................. 48 Figure 38: Experiment 4 prototype (Author, 2021) ............................................................. 49 Figure 39: Experiment 4 reservoir system temperature ..................................................... 50 Figure 40: Modelled Experiment 4 and installed into a room (Author, 2021) ..................... 51 Figure 41: Modelled Experiment 4 installed into a room (Author, 2021) ............................ 52

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List of tables Table 1: Setting out of problems as questions and hypotheses ........................................... 3 Table 2: Research paradigm of the researcher developed by Laubscher (2011:15) ........... 7 Table 3: Summary of the research design ........................................................................... 8 Table 4: Chapter 2 questions and hypotheses................................................................... 10 Table 4: Environmental implications (Eskom, 2015) .......................................................... 14 Table 5: Comparison of heat capacities and density of selected materials (Hanania et al.

2015) ......................................................................................................................... 16 Table 10: Experiment 1 questions and hypotheses ........................................................... 36 Table 12: Experiment 6 questions and hypotheses ........................................................... 47 Table 13: Sub-problem 1, associated hypothesis, findings, conclusion, and recommendation .................................................................................................................................. 55 Table 14: Sub-problem 2, associated hypothesis, findings, conclusion, and recommendation .................................................................................................................................. 55 Table

15:

Sub-problem

3

associated

hypothesis,

findings,

conclusions,

and

recommendations ...................................................................................................... 56 Table

16:

Sub-problem

4

associated

hypothesis,

findings,

conclusions,

and

recommendations ...................................................................................................... 56 Table

17:

Sub-problem

5,

associated

hypothesis,

findings,

conclusions

and

recommendations ...................................................................................................... 57

viii

List of acronyms and abbreviations ASHRAE

American Society of Heating, Refrigerating and Air-Conditioning Engineers

GHG

Greenhouse gasses

SANS

South African National Standards

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List of definitions Climatic zones

South Africa is divided into six main climatic regions, according to its climatic conditions, to assist with the design of a building into South African climate according to the National Building Standards (SANS 2042,2011).

C-value

The ability to store heat energy; thermal capacity (kJ/m2.K) of a material; is the arithmetical product of specific heat capacity (kJ/kg.K), density (kg/m3) and thickness (m) (SANS 204-2, 2011).

CR-value

Time constant (hours) of a composite element; product of the total C-value and the total R-value; higher CR-value the greater ability to moderate and minimise the effects of the external climatic conditions on the interior of a building (SANS 204-2, 2011).

Direction of heat flow Most significant heat flow at a given time; Heat flow from hot to cold environment, the direction of natural heat flow (SANS 204-2, 2011).

Fenestration

Section transmitting light into a building, including a glazing material (may be glass or plastic), framing (mullions, muntins, and dividers) (SANS 2042, 2011).

Glazing

Windows glazed doors or other transparent and translucent elements including their frames located in the building envelope (SANS 204-2, 2011).

Latitude and longitude

Pretoria has a latitude of 25.7479⁰ S and longitude of 28.2293⁰ E

Orientation

Direction which a buildings envelope faces (SANS 204-2, 2011).

R-value

Measurement of the thermal resistance of a material which is the effectiveness of a material to resist the flow of heat, thermal resistance (m2.K/W) thickness divided by its thermal conductivity (SANS 204-2, 2011).

Solar heat gain coefficient (SHGC)

Measure of the amount of solar radiation (heat) passing through the glazing (SANS 204-2, 2011).

Thermal capacity

The ability of a material to store heat; measured as a C-value. The higher the c-value, the greater the heat-storing capability (SANS 204-2, 2011).

Thermal comfort

“The condition of mind that expresses satisfaction with the thermal environment and is assessed by subjective evaluation” (ASHRAE 90.2, 2018)

Visible transmittance (VT)

The amount of visible light that comes through glazing is expressed as a number between 0 and 1,0, the higher number, the more light is transmitted, the better the VT

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Abstract Research indicates that South Africa is one of the world’s largest emitters of greenhouse gases due to a heavy reliance on coal as the primary source of energy supply. South Africa has abundant natural resources such as sunlight to use as sustainable, renewable and costeffective energy to moderate indoor climates. Solar design is one of the most economical solutions for improving buildings energy and indoor climates.

Homeowners, builders, and designers are once again encouraged to use and invest in renewable energy sources with the rising coal-powered energy prices and load-shedding crises in the country. Passive solar systems address heat losses through direct solar gains through wall openings, and the thermal mass of walls to absorb the heat. Efficient visual comfort can be achieved by controlling natural lighting. In order to guide seasonal variations for maximum efficiency, passive systems often require mechanisms to adapt as the climate changes. There for this study will investigate possible passive solar systems that could be implemented to improve energy efficiency in buildings with an emphasis on adaptability and versatility of use.

This study aims to improve indoor thermal comfort and contribute to energy savings, through the introduction of thermal mass to north-facing windows. This study will focus on investigating and evaluating the thermal performance of passive solar systems, to make recommendations for their adaptation achieving optimal performance in a variety of weather conditions. Prototypes of passive solar systems such as solar air heaters, trombe walls and water walls will be constructed to test, develop and propose the ideal a possible low-tech system. Numerical and experimental studies will be conducted to analyse the thermal performance of the system.

Keywords: Energy efficiency, passive solar systems, residential buildings, thermal comfort, thermal performance, Trombe walls, water walls

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Chapter 1: Introduction 1.2

Problem and its setting

South Africa’s heavy reliance on coal as the primary energy supply caused South Africa to be one of the world’s largest emitters of greenhouse gases (GHG) (Hausfather 2017).

According to the South African Energy Sector Report (Government of South Africa, 2018) less than 4% of South Africa’s energy supply is powered by renewable energy such as sun.

The residential sector's energy consumption consists of 72% coal-powered electricity and less than 20% renewable (Government of South Africa, 2011). South Africa has significant potential for renewable energy from its abundant natural resource of sunlight (Heggie, 2020).

Using renewable energy results in energy savings and reduced reliance on the grid provided energy, leading to a positive impact on sustainability in South Africa's built environment (Government of South Africa, 2018).

Solar systems are mainly divided into two groups: active and passive solar design systems.

Active solar systems include harvesting solar heat for re-use and photovoltaics as solar energy stores. Passive solar systems affect the energy demand directly by virtue of the performance characteristics of forms and materials themselves. By implementing passive design strategies and elements in buildings, the amount of energy required for heating and cooling can be decreased. The project is located on the northern facades of small buildings in Climate Zone 2 of South Africa.

1.2.1 Main problem statement The main problem is if passive solar design systems could be implemented in existing residential buildings to improve their thermal comfort and energy efficiency while ensuring compliance with the SANS 204 standards for active and passive systems.

Passive solar systems include addressing heat losses, direct solar gains through wall openings and thermal mass. Heat gains and efficient visual comfort can be achieved by controlling natural lighting. This study investigates solar air heating, natural lighting, and thermal mass in the context of operable north-facing windows. The design research focuses on passive solar systems by modelling and prototyping translucent low-tech, passive solar systems and introducing water as thermal mass.

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1.2.2 Sub-problems and related hypotheses Table 1: Setting out of problems as questions and hypotheses Sub-problems 1–5 (posed as questions)

Hypothesis 1–5

Sub-problem 1: Will passive solar systems improve residential buildings' indoor thermal comfort and visual comfort in Climatic Zone 2?

Hypothesis 1: It is hypothesised that passive solar systems will improve the indoor thermal and visual comfort in residential buildings in Climatic Zone 2.

Sub-problem 2: Will passive solar systems influence the energy demand of residential buildings in Climatic Zone 2?

Hypothesis 2: It is hypothesised that passive solar design systems will improve the energy efficiency of residential buildings, decreasing the energy demand of residential buildings.

Sub-problem 3: What are the most common and effective passive solar systems in residential buildings?

Hypothesis 3: It is hypothesised that passive solar systems such as solar air heaters, Trombe walls, and solar water heating are the most effective passive solar systems used in residential buildings.

Sub-problem 4: Can water be used as a thermal mass within the design of a passive solar system?

Hypothesis 4: It is hypothesised that water can be used as thermal mass in a passive solar system.

Sub-problem 5: What factors influence the implementation of these systems in residential buildings?

Hypothesis 5: It is hypothesised that the main factors influencing the installation are limited space, high construction costs, and ease of operability.

1.3

Purpose of this study

The purpose of this study is to investigate and gain knowledge about passive solar systems to determine if there is a potential of using water as thermal mass or a thermal buffer to improve the indoor thermal comfort of residential buildings in Climatic Zone 2 of South Africa.

In addition, this study determines how these passive solar systems can be implemented.

1.3.1 Objectives The main objective of this study is to investigate and evaluate passive solar systems to develop a system that improves thermal comfort and positively impact the energy efficiency of residential buildings in Climatic Zone 2 of South Africa. The investigation and prototyping

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evaluate the performance of combined passive solar systems, including technology developed with solar air heaters, Trombe walls, and water walls.

•

To investigate possible passive solar systems

•

To conduct experiments to investigate and evaluate whether water can absorb solar heat

•

To develop a water-based passive solar system for experimenting

•

To conduct experiments on developed systems

•

To analyse the data and make recommendations

•

To conduct experiments to improve on the developed system

•

To analyse the data and determine results.

1.3.2 Importance and benefits of this study South Africa has abundant natural resources, specifically sunlight, resulting in significant potential for using the resources as a renewable energy source (Heggie, 2020). Solar design strategies are economical solutions for improving most buildings’ climates.

This study investigates passive solar systems that could be implemented to the northern façade of residential buildings in Climatic Zone 2 of South Africa. Passive solar systems include addressing heat loss, direct solar gains through wall openings (windows), and using the walls' thermal mass to absorb heat.

An emphasis on adaptability and versatility introduces a water-based system as thermal mass to north-facing windows. This strategy improves indoor thermal comfort. A contribution to efficient visual comfort can be achieved by controlling natural lighting and improving energy efficiency, reducing GHG emissions.

1.3.3 Researcher's qualification to investigate The researcher has a formal qualification obtained in 2019: BTech Architectural Technology from Tshwane University of Technology. The researcher completed the required subjects, Environmental Science and Technical Design Studio V, during his first year of MArch: Architectural Technology in 2020. These subjects raised the researcher’s interest in the chosen research topic.

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1.4

Delimitations

The following delimitations apply to this study: •

This study focuses on the South African built environment because of its high reliance on coal for energy supply instead of the abundant natural resources of sunlight.

•

This study focuses on the residential sector.

•

Only passive solar strategies are investigated and applied to this study. No reference is made to the impact of wind and rain on residential buildings.

•

This study focuses on interior zones with habitable spaces such as bedrooms, dining rooms, and living rooms where air conditioning would be installed.

•

The SANS 204 standards for energy efficiency in buildings set the requirements for active and passive design systems. The systems in question are aimed at retrofitting existing buildings to make them SANS 204 complaint

•

This study does not focus on new regulations or improvements to existing regulations.

1.4.1 Assumptions This study assumes the following: •

All the materials required to construct the experiments are readily available

•

The weather conditions are favourable.

1.4.2 Limitations The following limitations apply to this study: •

The apparatuses used for this study may only produce limited results within the timeframe available.

•

The thermal measurement apparatuses are only available for a limited period due to borrowing them from a company.

•

Due to financial constraints, the apparatuses are borrowed and are only available for a short time.

• 1.5

Organic elements such as plants and trees are excluded from the thermal simulations.

Research context

The research context derives from the researcher's interest in designing green homes for sustainability. In Table 2, the researcher's paradigm explains the relationship between the researcher and the research. The researcher gathered knowledge regarding these 5

strategies for more energy-efficient buildings. The summary of the research objectives and specific phases of the execution plan are explained in Table 3.

The primary methodology for this study is design research. Accordingly, design decisions inform the development of new or refined hypotheses and research questions. This information is used in a feedback loop to improve prototypes to develop further questions.

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1.5.1 Research paradigm Table 2: Research paradigm of the researcher developed by Laubscher (2011:15)

Ontology

Epistemology

Research object

Meta-theoretical assumptions

Research method

Theory of truth

Statement = truth→ objective reality establishing a direct relationship between the research statements and reality

Validity

Certainty: The data truly measures reality A direct relationship exists between measurements + phenomena

Reliability

Replicability Research results can be reproduced by the researcher or other researchers to achieve a consistent result

~

Interpretivism

Alternative terms: Qualitative, soft, non-traditional, holistic, descriptive, phenomenological, anthropological, naturalistic, illuminative, among others Integrated experience Person (researcher) and reality are inseparable (life-world) Subjectivity Knowledge of the world is intentionally constituted through a person's lived experience Incorporated The research object is interpreted in the light of the meaning structure of the person's (researcher's) lived experience Content analysis through interpretation Preferred research methods include case studies, ethnographic studies, phenomenographic studies, ethnomethodological studies, among others Initial interpretation = truth → confirms a meaning (from researcher's experience) Truth as intentional fulfilment: interpretations of research object match lived experience of the subject The knowledge (claim) is defensible Evaluation criteria include credibility, transferability, dependability, and ability to confirm Interpretive awareness Researchers recognise and address the implications of their subjectivity

Normative position of the researcher

Strongly agree

Disagree

Alternative terms: Quantitative, scientific, experimental, difficult, reductionist, prescriptive, psychometric, among others Detached experience Person (researcher) and reality are separate Objectivity Objective reality exists beyond the human mind Separate The research object has inherent qualities that exist independently of the researcher Content analysis through statistics Preferred research methods include laboratory experiments, field experiments, surveys, among others

Pre-disposition of the researcher on a continuum scale

Neutral

+

Strongly agree Agree

Researcher's paradigm Positivism

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There is a definite relation between the researcher and the research process Research is objective information and is fact-based according to data collection and analyses Research object has inherent value, and the researcher will gain knowledge about this topic Most of the research is a desk study, the rest of this study are based on experiments and prototypes

Previous experience in design disciplines has a meaningful impact on the outcomes and procedures followed throughout this study.

Validation of the relationship is based on the data collected and analysed as well as simulations created Study can be repeated by someone else, and the result is comparable.

Recommendations are different

1.5.2 Research design Table 3: Summary of the research design Research design: Evaluating the performance of passive solar systems through modeling and prototyping devices for the northern facades of buildings in Climatic Zone 2 Phase 1: A review of pertinent literature and the existing practice model Phase 1.1 (Chapter 2) Theme: Solar systems Focus area: Passive solar systems Data source: Selected literature 1.1 Define passive solar systems.

1.2 History of passive solar systems 1.3 Advantages and benefits of passive solar systems 1.4 Types of passive solar systems: 1.5 Trombe wall 1.6 Water wall 1.7 Solar air heater

Phase 1.2 (Chapter 2) Theme: Focus area: Identifying specific demands of residential buildings Data source: Selected literature 1.2.1 Thermal mass 1.2.2 Thermal comfort 1.2.3 ASHRAE Standard 55-thermal environmental conditions for human occupancy 1.2.4 Energy efficiency within the context of the South African built environment 1.2.5 ASHRAE 90.2-2018 Energy efficiency design of low-rise residential buildings ▼

▼

Phase 2: Pilot study Phase 2.1 (Chapter 3)

Phase 3: Exploratory study (Chapter 4)

Theme:

Passive Solar Systems

Focus area:

Modelling and building of passive solar systems for testing

Theme:

Passive solar system prototyping

Focus area:

Prototyping and modelling of the passive solar system

Data source:

Data source: Selected literature 2.1.1 Identifying possible passive solar systems for experiments 2.2.1 Modelling and building of a low-tech passive solar system 2.3.1 Conducting of experiment on the low-tech system

3.1 3D modelling of the water-based low-tech passive solar system on ArchicCAD 3.2 Building of full-scale low-tech prototype of the passive solar system 3.3 Installation of full-scale low-tech prototype 3.4 Gathering of data during the experiment on the installed low-tech prototype of the passive solar system 3.5 Evaluating performance of the installed full-scale low-tech prototype

▼

Phase 2.2 (Chapter 3) ▼

Theme:

Thermal mass Evaluating the thermal performance Focus area: of materials for passive solar systems Data source: Numerical model from experiments 2.4.1 Numerical model to obtain thermal behaviour of systems and their materials 2.5.1 Numerical model displayed in tables and graph to show analysis

Phase 4: Rationalisation (Chapter 4) 4.1 4.2 4.3

Graphic presentation of the data Statistical description and analysis of the data Interpretation of the data

▼ ▼

Phase 6: Findings and conclusions (Chapter 5) Conclusions of the findings during the experiments to make recommendations

Progress Review (see Note 1) NOTE 1: When conducting a progress review, the researcher decides whether further investigation is needed. If yes, the researcher may proceed with the next phase.

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1.5.3 Triangulation research approach More than one research method is used. Multiple methods result in a triangulation approach to enhance confidence in the findings and results of the research (Bryman, 2004).

As a qualitative (secondary) research approach, a desk study is conducted about passive solar systems such as Trombe walls, water walls, thermal mass, thermal comfort, and energy efficiency (SANS 10400) to analyse and use as grounded theory for this study.

A quantitative approach that provides a numerical model of the room and water temperature is generated from the data obtained during the experiments to analyse the developed system’s thermal behaviour over time and give unbiased results (McLeod, 2019).

The following methods were used to gather data: •

Desk study

•

Experimental study

•

Numerical model.

1.6

Summary of Chapter 1

Chapter 1 introduces South Africa’s heavy reliance on coal-powered energy and its potential to use the abundant natural resource of sunlight. The residential sector forms the setting and the background of this study. The main problem statement forms sub-problems (posed as questions) and their hypotheses. Delimitations, assumptions were listed, and objectives of this study were created. The research context and paradigm were discussed to define the normative position of the researcher. The research design in Table 3 explained the structure of this study, including the pilot study through to the experiments and their conclusions and recommendations in the following chapters.

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Chapter 2: Literature review 2.1

Introduction

The purpose of this chapter is to: •

Briefly discuss the current state of South Africa’s energy supply

•

Define active and passive solar

•

Investigate different passive solar systems

•

Advantages of passive solar systems

•

Disadvantages of passive solar systems.

Table 4: Chapter 2 questions and hypotheses Sub-problem 1

Hypothesis 1

Will passive solar systems improve indoor thermal comfort and visual comfort of residential buildings in Climatic Zone 2?

It is hypothesised that passive solar systems will improve the indoor thermal and visual comfort in residential buildings in Climatic Zone 2.

Sub-problem 2

Hypothesis 2

Will passive solar systems influence the energy demand of residential buildings in Climatic Zone 2?

It is hypothesised that passive solar design systems will improve the energy efficiency of residential buildings, decreasing the energy demand of residential buildings

.

The literature review serves as background to this study and focuses on existing information regarding: •

Climatic responses to Climatic Zone 2

•

Methods, materials and implementations of thermal mass

•

Passive solar systems to improve thermal conditions

•

Thermal comfort.

Research has shown that the heavy reliance on coal as the primary energy supply makes South Africa is one of the world's largest emitters of GHG (McSweeney, 2018). According to the South African Energy Sector Report (Government of South Africa, 2018), South Africa's energy supply is predominantly (83%) coal-powered. A fraction (4%) of the energy is supplied from renewable energy sources.

The residential sector's energy consumption consists mostly (72%) of coal-powered electricity, and less than a quarter (20%) is renewable energy (Government of South Africa,

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2018). South Africa has a significant potential for renewable energy with its abundant natural resources of sunlight (Heggie, 2020). Renewable energy use results in energy savings and reduced reliance on grid-provided energy, leading to a positive impact on energy sustainability in South Africa's built environment (Government of South Africa, 2018).

2.2

Residential sector

In South Africa, almost a third (27%) of supplied energy was consumed by the residential sector, according to the South African Energy Sector Report (Government of South Africa, 2018). The residential sector's energy consumption is expected to increase with population growth and economic growth. Over the past 15 years, consumption has risen with more than 10% of the total consumed energy in South Africa (Government of South Africa, 2018). In light of the figures in Figure 1, the residential sector shows a potential for energy savings.

Figure 1: Energy demand by sectors (Government of South Africa, 2018)

Climate around the globe ranges from cold and dry polar climates to hot and wet tropical climates. The sun’s energy heats the land and water masses and primarily influences climatic zones. The climate is also influenced by the topography, geomorphology, altitude, the relation to water masses, ocean currents, patterns of wind, and the vegetation pattern at a regional level.

Figure 2 illustrates the six climatic zones of South Africa according to SANS 10400-XA.

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Figure 2: Climatic zones of South Africa (SANS 10400-XA, 2011).

According to SANS 10400-XA (2011), Climatic Zone 2 is defined as ‘temperate interior’, and has the following main characteristics: •

Low diurnal temperature range near the coast but range increases in the interior

•

Four distinct seasons

•

Summer and winter can exceed the human comfort range

•

Spring and autumn are ideal for human comfort

•

Mild to cold winter with low humidity

•

Hot to very hot summers with moderate humidity.

The following design responses are best used in Climatic Zone 2 (Schmidt, 2013): •

Use passive solar principles

•

High thermal mass solutions are recommended

•

Use high insulation levels, especially to thermal mass

•

Maximise north-facing walls and glazing, especially in living areas with passive solar access

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•

Minimise all east and west glazing

•

Use adjustable shading

•

Use double glazing and heavy drapes with sealed pelmets to insulate windows

•

Minimise external wall areas

•

Use cross-ventilation and passive cooling in summer

•

Use convective ventilation and heat circulation

•

Site new buildings for solar access, exposure to cooling breezes and protection from cold winds

•

Draught seal thoroughly and use entry airlocks

•

No auxiliary heating or cooling is required in these climates with good design

•

Use reflective insulation to keep out summer heat

•

Use bulk insulation to walls, ceilings, and exposed floors.

Climatic Zone 2 is classified as a temperate interior according to the SANS 204. The summer is very hot, with moderate humidity. The winters are cold with low humidity. Summer and winter can exceed the human comfort range.

Some of the best design responses to Climatic Zone 2 are using passive solar principles, high thermal mass solutions, adjustable shading, double glazing, heavy drapes, crossventilations, passive cooling, convective ventilation, and heat circulation. According to these principles, no auxiliary heating or cooling is required if a good design is present.

2.3

Energy

Energy efficiency implies using energy wisely and performing tasks using the least energy possible. Energy efficiency in the built environment can result in energy savings and reduced reliance on coal-powered electricity, positively impacting South Africa's residential sector and natural environment.

Table 4 illustrates the positive environmental implications by saving only one kilowatt-hour of electricity.

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Table 4: Environmental implications (Eskom, 2015)

As temperature drops during the winter, a typical 200-litre household geyser could double a household’s electricity bill. A geyser cools faster in the winter due to natural thermodynamics as the hot air escapes into the surrounding cold air. Between a third and a half (30–50%) of a domestic electricity bill is used to heat water with energy-intensive elements (Eskom, 2015).

Two predominant types of solar-gain strategies are used in buildings to reduce energy consumption without affecting comfort level: active and passive solar strategies.

2.3.1 Active solar Active solar designs use equipment to convert solar energy into usable electricity. These strategies are rapidly evolving, and their efficiency is constantly improving. Active solar strategies include solar water heating, and solar energy harvesting, among others (Phelan Energy Group, n.d.).

2.3.2 Passive solar The term 'passive' indicates that the sun's heat energy is absorbed by direct exposure to the sun. The conventional method is indoor cooling and heating to reduce energy costs (and ultimately GHG emissions). Examples of passive solar design options include insulation, window placement, thermal mass, ventilation, circulation, angle and direction of the sun, surface colours, and geographical location (Gevorkian 2009).

Passive solar systems only use the sun's energy to provide heating and cooling ventilation.

These systems do not rely on auxiliary energy sources and work when the municipal

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electrical supply is unavailable. Passive solar systems are comparatively inexpensive, often simple to build, do not need a specialist to install, and require little to no maintenance, resulting in a long life (Manson & Yahooti 2017).

Elements that contribute to passive solar heating are examined throughout this study, including buffer spaces, double facades, insulation, and thermal mass.

2.3.3 Thermal comfort A building is the main instrument used to achieve thermal comfort requirements (Olgyay 1963). People strive towards the minimum energy expenditure required to adjust to a specific environment (Olgyay 1963).

The ‘comfort zone’ represents the conditions under which this point is achieved. In the ‘comfort zone’, people’s energy becomes available for productivity.

Thermal comfort is a condition of mind that expresses satisfaction with the thermal environment (ASHRAE 2004). Because there are large variations from person to person, both physiologically and psychologically, satisfying everyone in a space is difficult (ANSI date??; ASHRAE 2004).

2.3.4 Thermal mass Thermal mass is a material's ability to absorb, store, and release heat. The higher the thermal mass, the more heat the material can absorb and the longer the material takes to cool down. The thermal mass of building materials helps prevent high interior temperature fluctuations, making the interior temperature more moderate, resulting in a more comfortable building environment (Figure 3) (Schmidt 2013).

As shown in Figure 3, a wall absorbs the sun’s heat and radiates its heat into the room.

There are many ways to introduce thermal mass to the design of a building, especially into the envelope of the building.

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Figure 3: Thermal mass diagram of a Trombe wall and sunspace (Venturewell, 2013)

A material ideal for thermal mass has a high heat capacity and high material density. The heat capacity of materials is the amount of energy needed to change the temperature of the material and is measured in joules per kelvin (J/K). The density of a material is proportional to the thermal mass system’s total amount of energy stored. The specific heat capacity of a material is then determined by multiplying the heat capacity with its density (J/m3K) to determine if a material should be used as thermal mass material in a building.

Table 5: Comparison of heat capacities and density of selected materials (Hanania et al.

2015)

As shown in Table 4, water has a density of 1000kg/m3, which is low compared to more commonly used structural building materials such as concrete (with a density of 2371kg/m3) or brick (with a density of 2611kg/m3). Although water has a lower density, it has a very high heat capacity of 4.18 J/K compared to a heat capacity of 0.84 J/K for brick and 0.88 J/K for concrete. The high heat capacity of water means a high volumetric heat capacity of 4.18

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MJ/m3K. Thus, water is a material with a high potential for use in passive solar design systems of a building.

The energy consumption of a building’s heating and cooling systems can be reduced significantly by correctly using passive solar systems such as solar walls, Trombe walls, or water walls (Hanania et al. 2015).

2.4 2.4.1

Passive solar systems Trombe wall

In South Africa, a Trombe wall is a sun-facing or north-facing wall or panel, usually made of a material with a high thermal mass. The Trombe wall absorbs solar heat during the day and slowly releases heat into the interior. Trombe walls are reliable with a simple, low-cost design that can play a vital role in green architecture (Omara & Abuelnuor 2019).

The system in Figure 4 is covered with glazing outside, creating an air gap where the air heats from solar radiation, resulting in convection in the air and causing hot air to rise.

Figure 4: Trombe wall diagram (by MyPoolGuy) edited (Author, 2021)

Heat exchange with the interior takes place through the thermal mass, to distribute the heat temporally. Vents are added to the bottom and top of the system to control the convection of the air. These vents can be closed in summer to prevent hot air from getting in (Schmidt

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2013). The setup in shows the radiated heat from the Trombe wall that acts as the thermal mass of the room (Figures 5 and 6).

Figure 5: Trombe wall diagram (MyPoolGuy) edited (Author,2021)

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Figure 6: Trombe wall thermal mass setup (J.M.K.C, 2015).

2.4.2 Water wall A water wall is a system that works similarly to Trombe walls. The water wall is a non-loadbearing wall made from water tanks or water silos located on the solar-access sunny, which is the northern façade of a building in South Africa. The water is subject to convection during heating, causing the system to conduct the heat more rapidly than a Trombe wall system with a much higher thermal lag (Figure 7) (Gut & Ackerknecht 1993).

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Figure 7: Sun-lite thermal storage tubes (Solar Components, 2019)

The water acts as a thermal mass and heats passively with solar energy. This energy can then be used for heating and cooling homes. Colour pigments are also added to some silos to tint the water dark blue, thus absorbing more heat without significantly blocking the sunlight. The more sun exposure, the more heat the system absorbs. Therefore, more heat can be radiated into the house during the cooler evenings (Bainbridge 2015).

2.4.3 3D printed modern Trombe wall The system in Figures 8 and 9 is 3D printed from translucent recycled PET plastic. The system is a double-layered, hollow-cored design with phase changing material (PCM) in the core to absorb solar heat during the day and radiate heat into the room during the evening.

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Figure 8: (Left) Double face 2.0, a geometrically optimised Trombe wall (TUDelft, Farrugia, E, 2018) Figure 9: (Right) Double face 2.0, 3D model (TUDelft, Farrugia, E, 2018)

Phase-changing materials can absorb the same amount of solar energy through latent heat storage in a much smaller volume. The heat is absorbed via an endothermic reaction during the temperature increase of the material changes from solid to liquid. The stored heat is released into the building via an exothermic reaction when the material changes from liquid to solid during cool nights.

These passive solar systems work with similar principles, absorbing solar heat during the day and radiating the heat into the room throughout the day and evening. Another principle of passive solar systems is the thermosyphon effect. The hot air rises above the cooler air as the system radiates heat. This hot-air-rising principle could be implemented into a system to create hot and cold air circulation.

2.4.4 Thermosyphon effect The thermosyphon effect is a method of passive heat exchange based on natural convection. The thermosyphon effect exists when water heats. The water becomes less dense, lighter, with less hydrostatic pressure, causing the heated water to rise above the

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colder water. The greater hydrostatic pressure of the colder water forces the water through the system by gravity, resulting in natural convection.

The thermosyphon effect is created by the difference in hot and cold water density. This effect relies on gravity. The hot water has more energy, is less dense, and rises above the cold water, causing the water to circulate.

2.4.5 Solar air heater A solar air heater sucks air in at the bottom and heats the air through solar radiation in pipes, causing convection. The hot air is pushed out into the room through a fan at the top of the system. The system should be installed on the sunny, northern side of a building to get as much solar exposure and be most effective (Baruah & Choudhury 2017).

Figure 10 shows how the room air is heated with an external solar air heater.

Figure 10: Solar air heater (Fratzel n.d.)

Figure 10 shows how room air enters the system at the inlet and moves underneath the black collector plate. The black collector plate is heated by solar radiation and heats the air as it moves through the gap at the bottom. The hot air rises and enters the room to heat it.

Figure 11 shows easy and low cost do-it-yourself solar air heaters examined for this study.

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Figure 11: Types of DIY solar air heaters (Rimstar, 2005)

These designs shown in Figures 10 and 11 are all similar where cool air enters from the bottom, heats the air as it moves through the painted-black system (to absorb as much solar heat as possible), and then the hot air exits at the top to heat the room. The image to the left of Figure 11 is a screen design, where the air enters at the bottom of the system and moves in front of the black screen. The air exits at the top as it rises when heated by the sun-heated screen. In the ‘back pass with baffles’ system in Figure 11, the air enters at the bottom hole and is heated as it moves under a black screen in the direction of the exit hole as it is diverted. The last two images in Figure 11 indicate where the air enters the system and is heated as it moves through black painted cans (which are connected through holes at the bottom and top of the cans), or when moving through a black painted downspout.

2.4.6 Light through water The law of refraction (or Snell’s Law) was discovered in the fifteenth century by a Dutch mathematician and geodesist Willebrord Snel van Royen. Figure 12 illustrates the refraction of a light ray as it hits the water.

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Figure 12: Refraction of light in water (Science Learning Hub, 2012)

This effect is manipulated by filling a bottle with water and exposing it to sunlight. As the light enters the bottle of water, the light reflects back and forth as it travels through the water and lights up the room evenly (Figure 13).

Figure 13: Refraction of light in a water bottle (Bansod, 2015)

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Figure 13 is a photograph of a bottle in the Liter of Light project.

Figure 14: Bleach-and-water filled bottle light (Mae 2018)

The Liter of Light project directs users to put a mixture of water and bleach into a plastic bottle. Sunlight is reflected from the outside, through the water and into the room. This bottle works most efficiently when installed in the roof. This bottle of light is a very inexpensive and adequate light source. Alfredo Moser had the original idea. He shared the idea with the nonprofit organisation MyShelter Foundation that started the Litre of Light project in 2012 in the Philippines. The goal of the project is to provide a sustainable alternative to electricity in poor areas. The life expectancy of a bottle is roughly five years. The one litre of water and three millilitres of bleach is cheap to replace.

Most countries carelessly dispose of plastic bottles. Roughly eight million tons of plastic end up in the ocean each year (Von Troscke 2015). This project reduces the amount of garbage discarded by re-using plastic bottles, and light is provided in poor communities. Thus, two problems are solved (Fielder 2017).

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2.5

Summary of Chapter 2

Chapter 2 concludes Phase 1 and 1.2 of this study, as presented in the research design.

The figures were presented regarding South Africa’s high energy demand for coal-powered energy and energy from the natural resource of sunlight for powering electricity. The definition of active and passive solar systems was introduced. A literature review was conducted on pertinent literature regarding passive solar systems available in the built environment.

This chapter introduced the first two sub-problems as enumerated in Chapter 1: Table 6: Chapter 2 focused on sub-problem 1 and 2 Sub-problem 1

Will passive solar systems improve indoor thermal and visual comfort of residential buildings in Climatic Zone 2?

Sub-problem 2

Will passive solar systems influence the energy demand of residential buildings in Climatic Zone 2?

Furthermore, thermal comfort and thermal mass were discussed in Chapter 2 and enabled the framework development of this study.

Chapter 3 focuses on designing and testing a passive solar system using water as thermal mass to contribute to thermal comfort and energy efficiency in residential buildings.

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Chapter 3: Pilot study 3.1

Water as thermal mass material

This chapter aims to identify if water can absorb solar energy as heat. If so, water could be used as a thermal mass material in passive solar systems to improve thermal comfort in the habitable zones within residential buildings in Climatic Zone 2 of South Africa. A prototype was executed by modelling and building a low-tech passive solar system to evaluate solar heat absorbing performance.

Chapter 3 initiates Phase 2 of the research design, outlined in Phase 2.1 of the pilot study (Table 3). Chapter 3 focuses on sub-problem 4 and its related hypothesis (Table 6).

Table 7: Chapter 3 focuses on sub-problem 4 and its related hypothesis Sub-problem 4

Hypothesis 4

Can water be used as thermal mass within the design of a passive solar system?

It is hypothesised that water absorbs and stores heat that can be used as thermal mass in a passive solar system.

3.1.1 Methodology The first experiment was conducted to overview the thermal absorbing properties of water when exposed to solar radiation during the day. The first experiment consisted of testing the thermal mass capabilities of water by logging the temperature of the water regularly during the day when exposed to solar radiation. The experiment showed how much solar energy heat water absorbs and releases during the evening. The water temperature was monitored to see how long the water stores heat energy before cooling down and reaching room temperature. This experiment was carried out in a habitable zone, a bedroom, of a residential building in Pretoria (in Climatic Zone 2).

The experiment’s sampling size consists of: • 0.75 litre plastic PET bottles •

1.5 litre plastic PET bottles

•

5 litre plastic PET bottles

•

1.25 litre glass bottles

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3.1.2 Apparatus This section introduces the apparatus used during the experiments to measure the temperature of the water and the room temperature during the selected time for each experiment. These temperatures were then logged and graphed to analyse the temperature changes during the experiment.

The following apparatuses (Figures 15 to 18) were used: Indoor/Outdoor Thermometer with Hygrometer •

Thermometer probe was inserted into the water to measure the water temperature

•

This less-expensive temperature logger meant the researcher had to log the temperature at the desired intervals.

•

Measurements were logged to generate graphs for analysing.

Figure 15: Indoor/Outdoor Thermometer with Hygrometer (Author, 2021)

Gemini Tinytag TGP-4020 •

Temperature and humidity data logger

•

Logger should be programmed to measure the water temperature at the desired time and over the desired period for accurate results

•

Thermistor probe should be inserted into the water to measure the water temperature

•

The results were downloaded to a computer for viewing and analysing the data.

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Figure 16: Gemini Tinytag TGP-4020 (Author, 2021)

Gemini Tinytag TGP-4500 •

Temperature and humidity data logger

•

Logger should be programmed to measure the room temperature at the desired time and over the desired period for accurate results

•

The results were downloaded to the computer for viewing and analysing the data.

Figure 17: Gemini Tinytag TGP-4500 (Author, 2021)

Elitech RC-5 USB •

Temperature data logger

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•

Logger should be programmed to measure the room temperature at the desired time and over the desired period for accurate results

•

The results can then be downloaded to a computer for viewing and analysing the data.

Figure 18: Elitech RC-5 USB (Author, 2021)

Figure 15 illustrates the Indoor/Outdoor Thermometer and Hygrometer used to measure water temperature by the researcher at indicated intervals. The data was noted into Microsoft Excel for analysis. The researcher programmed the Gemini Tinytag loggers (Figures 16 and 17) and the Elitech logger (Figure 17) to measure the water and room temperatures at the desired intervals. The loggers automatically logged the data to generate graphs.

The apparatus used for the experiment was calibrated by comparing the room temperatures and water temperatures logged against each other. The Indoor/Outdoor Thermometer probes with Hygrometer (Figure 15) and the Gemini Tinytag TGP-4020 (Figure 16) were placed in a 1.5 litre water bottle, and the data was logged hourly. The Indoor/Outdoor Thermometer (Figure 15) logged the water temperature at 41°C by 14:00, and the Gemini data logger (Figure 16) logged the water temperature at 41,5°C. The Gemini Tinytag TGP-4500 (Figure 17) and the Elitech RC-5 USB (Figure 17), temperature loggers were compared to the Indoor/Outdoor Thermometer with Hygrometer (Figure 15) by placing the loggers in the same location in a room for 24 hours and logging the data hourly. During the calibration test, the Gemini Tinytag TGP-4500 (Figure 17) and Elitech RC-5 USB data loggers logged the same room temperatures of 25,3°C at 14:00 and the Indoor/Outdoor Thermometer with Hygrometer (Figure 15) room temperature of 26°C.

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The calibration of the apparatus was satisfactory when compared and received similar results.

3.1.3 Background Research regarding water walls, thermal mass, and thermosyphon indicates the possibility of using water to absorb solar energy as heat to radiate into the interior. This radiation reduces sizeable indoor temperature fluctuations and creates a more thermally comfortable indoor climate. Prototypes are modelled and constructed during the experiments to test and evaluate.

3.2

Pilot study experiment

3.2.1 Introduction The experiment was divided into four levels. The first and lower level consisted of three 5 litre plastic PET bottles. The second level consisted of four 1.5 litre plastic PET bottles. The third level consisted of four 0.75 litre plastic PET bottles. The fourth level was presented and tested after the pilot experiment. The fourth level consisted of four 0.75 litre plastic PET, with a closed-off back and a 250-micron DPC sheet. Each of the bottles was filled with normal tap water. A model of the first experiment was shown in Figure 18 and the built experiment in Figure 19.

The Indoor/Outdoor Thermometer and Hygrometer (Figure 15) and Gemini Tinytag TGP4020 logger (Figure 16) were used to measure the water temperature during the experiment.

The water measurements of each bottle were taken hourly for two days and logged into Microsoft Excel to generate graphs to evaluate the temperature changes. The Gemini Tinytag TGP-4500 logger (Figure 17) was used to measure the room temperature during the experiment. The room temperature was taken hourly for two days and logged into Microsoft Excel to generate graphs and evaluate the temperature changes.

3.2.2 Questions and hypotheses Chapter 3 pilot study questions and hypotheses are shown in Table 8.

Table 8: Pilot study experiment questions and hypotheses Question

Hypothesis

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Can the water absorb the solar heat energy?

It is hypothesised that the water in the bottles can absorb and store heat energy from the sun.

How long can water store It is hypothesised that water can store heat energy absorbed from the the heat energy absorbed sun for the whole night. from the sun?

3.2.3 Design of the experiment Figure 19 is an annotated 3D representation of the design and materials used in the system to be built for the first experiment. Figure 20 is a photograph of the built and installed system used in the pilot study experiment. The system was installed on a windowsill inside a habitable zone in a residential building in Pretoria (Climatic Zone 2).

Figure 19: Modelled pilot study experiment (Author 2021)

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Figure 20: Photograph of pilot study experiment (Author, 2021)

3.2.4 Data analysis and interpretation Figure 21 indicates the fluctuation in water temperature logged during the pilot study experiment over two days. Figure 22 shows the room temperature during the same period.

Figure 21: Water temperature measured during the pilot study (Author, 2021)

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Figure 22: Room temperature and humidity measured during the pilot study (Author, 2021)

3.3

Conclusion

The combined data from Figures 21 and 22 is illustrated in Figure 23. The graph in Figure 23 illustrates that when water is exposed to sunlight, it absorbs heat and reaches a higher temperature than the room. The heat radiates into the room during the evening.

Figure 23: Water temperature findings (Author, 2021)

The water absorbed heat from the sunlight and reached a temperature of 41°C by 14:00 when the room temperature was only 25°C. By midnight, the water temperature was still 2°C above the 23.3°C room temperature. As the water bottle cooled, the heat was radiated into the room until the water bottles reached the same temperature as the room at 07:00 the next morning, just before the new day’s sunlight would heat the water again.

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3.4

Summary

Based on results in the pilot experiment, the water absorbed a significant amount of solar energy as heat during the day. The water radiated the heat into the room during the cooler evening. Consequently, water was found to be fit for use as a thermal mass material in a passive solar system. The next section consists of experiments to further test and evaluate the water’s performance to develop and improve the system.

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Chapter 4: Experiments and data representation 4.1

Introduction

This chapter focuses on Phase 3 of the research design (Table 3). Each experiment is formed by a question with its related hypothesis formed from the findings and conclusion of the previous experiment.

Chapter 4 initiates Phase 3, the experimental study of the research design (Table 3).

Chapter 4 focuses on sub-problems 4 and 5, and their related hypotheses are shown in Table 9.

Table 9: Chapter 4 focuses on sub-problems 4 and 5 and their related hypotheses Sub-problem 4

Hypothesis 4

Can water be used as a thermal mass within It is hypothesised that water can absorb and store the design of a passive solar system? heat in thermal mass in this passive solar system.

Sub-problem 5

Hypothesis 5

What factors influence the implementation of It is hypothesised that the main factors influencing these systems in residential buildings? the installation are limited space, high construction costs, and ease of operability

4.2

Experiment 1: Translucent qualities vs heat storage

This experiment was constructed with the design of a Trombe wall and solar air heater in mind. The water bottles were placed on a shelf and closed off by wrapping them with black plastic to absorb more heat. Table 10 indicates questions and their hypotheses formed as the experiments progress.

4.2.1 Questions and hypotheses Table 10: Experiment 1 questions and hypotheses Question

Hypothesis

What is the effect of closing It is hypothesised that the water bottles in the boxes will take longer off the system in a box? to cool down to room temperature due to reaching higher temperatures and radiating heat slower through the box. The heat stays in the box.

What is the effect of closing It is hypothesised that the water bottles in the box with black backing off the system in a box with will absorb more heat due to the high absorbent properties of darker black backing material? colours.

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4.2.2 Design of the experiment

Figure 24: ArchicCAD modelled experiment (Author 2021)

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Figure 25: Photograph of Experiment 1: Boxed water bottle with probe (Author, 2021)

4.2.3 Data representation

Figure 26: Water temperature during Experiment 1

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Figure 27: Room temperature graph during Experiment 1

4.2.4 Findings and conclusion This experiment was constructed with a closed back of black plastic material. The water reached a temperature of 67,1°C by 14:00, when the room temperature was 27,2°C. By midnight, the water temperature was still 30°C and still 2°C above the room temperature of 22.7°C at 07:00, when the sunlight heated the water again. The water bottle radiated heat throughout the night until the next morning, when the water absorbed heat from the sun again.

The water bottles in the closed-off box with black plastic inside reached higher temperatures with access to sun exposure. However, the box obstructed the room from receiving solar heat gains. The box also darkens the room, resulting in electrical lighting required during the day.

Thus, the translucent water bottles were taken further for additional experiments to improve and absorb more heat from the sun without influencing the solar access for heat gains or the room’s lighting.

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4.3

Experiment 2: Translucent vs coloured water

This experiment tested if adding colour pigments or bleach to water positively impacts its ability to absorb heat. This experiment uses four 1.5 litre bottles filled with water, each with colour pigments: red, blue, and green.

4.3.1 Questions and hypotheses Table 11: Experiment 2 questions and hypotheses Question

Hypothesis

Will the water absorb more solar heat energy when a mixture such as colour pigments is added to the water?

It is hypothesised that water’s ability to absorb more solar heat will improve by adding a darkcoloured pigment.

Will the water radiate light and act as a light It is hypothesised that the water and bleach source when a mixture such as bleach is added mixture will radiate light during the day when the to the water? sun shines.

4.3.2 Design of the experiment An annotated 3D model of the design of the experiment is illustrated in Figure 28. Figure 29 is a photograph taken of the pigment-coloured bottles used for the experiment. The bottles were placed in the window frame for solar exposure, and the results are shown in Figure 30.

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Figure 28: ArchicCAD model of Experiment 2 (Author 2021)

Figure 29: Photograph of pigmented water for Experiment 2 (Author, 2021)

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4.3.3 Data representation The graph in Figure 30 illustrates the temperature fluctuations of each water bottle with colour pigment and the room temperature over two days during the experiment.

Figure 30: Water and room temperatures of the colour-pigment experiment (Author, 2021).

4.3.4 Findings and conclusion An experiment was constructed to test if adding colour pigments to water improves the water heat-absorbing properties from the sun. The water bottle with the green pigment reached the highest temperature of 43.7°C, then the water with the blue colouring pigment with 43.6°C, then the red colouring pigment with 43.3°C. The bottle with clear water reached a lower temperature of 40.8°C. The darkest colour reached the highest temperature. However, by midnight the temperature of all the water bottles was almost the same at around 25°C with the room temperature at 24°C. The researcher noted that there was a difference in water temperature of almost 2°C from the bottom to the top of the bottle. This temperature difference developed the questions for the next experiment looking further into convection and the thermosyphon effect and if it is possible to create the effect and increase the temperature of the water.

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4.4

Experiment 3: Thermosyphon effect

In the previous experiment, the researcher noted a difference in the water temperature at the top and bottom of the bottles. This temperature difference is called convection and is created by the hot and cold water density difference. When using this temperature difference in a closed system, convection creates the thermosyphon effect. This effect relies on gravity.

The hot water has more energy and is less dense and rises above the dense cold water, causing the water to circulate and creating natural convection.

This experiment tested if higher temperatures were reached by connecting the top of one bottle to the bottom of the next and creating a thermosyphon effect.

4.4.1 Questions and hypotheses Table 12: Experiment 3 questions and hypotheses Question

Hypothesis

Will it be possible to create a thermosyphon effect when connecting the water bottles?

It is hypothesised that connecting the bottles in a series will cause the warmer water to rise, creating circulation.

What effect will the thermosyphon effect have on the proposed system?

It is hypothesised that the water will not reach higher temperatures and delay the cooling down of the water.

4.4.2 Design of the experiment Figure 31 is an annotated 3D model design of the proposed design of the system thus far.

The system can be installed in an interior during the winter months to radiate the heat into the interior. The system can be installed on the exterior during the summer months to keep the heat outside.

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Figure 31: 3D model of Experiment 3 (Author, 2021)

Figures 32 and 33 are photographs of the built and installed system.

Figure 32: Experiment 3 prototype (Author, 2021)

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Figure 33: Photograph of prototype for Experiment 3 (Author, 2021)

Figure 34 shows photographs of the connections to connect the bottles in the prototype. The connections are 13mm Nylon 90° fittings glued to the bottle cap and the bottom of the bottle.

The fittings are then connected with a 15mm translucent hosepipe to connect the bottles.

Figure 34: Photographs of connections (Author, 2021)

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4.4.3 Data representation The graph in Figure 35 illustrates the outdoor temperature and the temperature of the water system.

Figure 35: Experiment 3 system temperature (Author, 2021)

4.4.4 Findings and conclusion During the experiment, the water absorbed heat from the sun and reached temperatures up to 49,5°C by 15:00 when the outdoor temperature was only 30°C. By midnight, the water temperature was still 1°C above the outside temperature of 18°C. The bottle cooled until it reached the same temperature as outside and heated again from 07:00 the next morning when the sun reached the water.

The temperatures did not reach higher temperatures when connected as anticipated as the system is closed. All the bottles reached the same temperature during solar exposure, raising the next question for the next experiment. Will the thermosyphon effect in the prototype system heat the water of a reservoir when it is added to the system? The reservoir experiment tested if the system could be linked to a geyser of a household to preheat the water in the geyser and reduce the electricity bill of the household.

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4.5

Experiment 4

Experiment 4 links with Experiment 3, where the thermosyphon effect was tested.

Experiment 4 was conducted by connecting a reservoir to the system to identify if the water in the reservoir can be preheated before entering the geyser by the thermosyphon effect caused by solar heat. The thermosyphon effect would then heat a room and result in energy savings.

4.5.1 Questions and hypotheses Table 12: Experiment 6 questions and hypotheses Question

Hypothesis

Will the system heat water stored in a reservoir? It is hypothesised that the system will heat water in a reservoir.

Will adding a reservoir to the system improve the thermosyphon effect?

The cold water in the reservoir will move to the bottom, circulating through the system by gravity. The water will then be heated by the sun. The water will heat and become less dense, resulting in hot water rising through the system and entering the reservoir from the top.

4.5.2 Design of the experiment Figure 36 is an annotated 3D ArchicCAD model of the proposed design for the next experiment of the system. This experiment followed the previous experiment by adding a reservoir to the system. Figures 37 and 38 are photographs taken of the full-scale built system. Figure 37 illustrates the link between the bottles that consists of 13mm nylon elbows and 13mm T-inserts connected by a 15mm translucent hose pipe for water circulation. The 13mm nylon fittings are inserted and glued with Pratley Powda Bond Adhesive and a powder filler applied to the drilled holes in both the bottle caps and lowest point of the bottles.

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Figure 36: 3D model of Experiment 4 (Author, 2021)

Figure 37: Experiment 4 prototype (Author, 2021)

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Figure 38: Experiment 4 prototype (Author, 2021)

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4.5.3 Data representation Figure 39 illustrates the logged outdoor temperature, the water temperature of the 5-litre water reservoir added to the system, and a 5-litre water bottle next to the reservoir (which is not connected to the system) during the period of the experiment.

Figure 39: Experiment 4 reservoir system temperature

4.5.4 Findings and conclusion Two 5-litre water bottles were placed outside in the shade. One of the 5-litre water bottles was connected to the built prototype system and used in Experiment 3. This experiment was constructed to test if connecting the 1.5-litre water bottles to a 5-litre bottle will create the 5litre bottle as a reservoir. In addition, this experiment tested if the water is heated in the added reservoir by the thermosyphon effect.

As seen in the graph shown in Figure 39, the system can heat the water in the connected reservoir to 40°C by absorbing heat energy from the sun, while the outdoor temperature is only 30°C. The other 5-litre water bottle only reached 27,7°C by 15:00.

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4.6

Summary of Chapter 4

As shown in Figure 40, the water bottles can absorb heat energy from the sun during the day and radiate that heat into the room during cool evenings. The system could be installed on the interior during the winter and the exterior during the summer.

Figure 40: Modelled Experiment 4 and installed into a room (Author, 2021)

By connecting the bottles to a reservoir, the bottles heated the reservoir using the thermosyphon effect. This effect can heat water in remote areas or preheat a household geyser and reduce electricity costs.

Figure 41 is a system design for recommended future studies where the system could be installed on the interior windowsill. During the cool evenings, the system could then be moved away from the windows to reduce the heat loss through the window and radiate absorbed heat into the room.

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Figure 41: Modelled Experiment 4 installed into a room (Author, 2021)

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Chapter 5: Findings, conclusions, and recommendations 5.1

Summary of research

5.1.1 Summary of Chapter 1: Introduction Chapter 1 introduces South Africa’s heavy reliance on coal-powered energy and the potential to use the abundant natural resource of sunlight in the residential sector. The residential use of natural resources forms the setting and background of this study. The main problem statement was to form sub-problems (posed as questions) and their hypotheses. Delimitations and assumptions were listed, and objectives were created for this study. The research context and paradigm were discussed to define the normative position of the researcher. The research design was laid out in Table 3 that explained the structure of this study, from the pilot study to the experiments, conclusions, and recommendations.

5.1.2 Summary of Chapter 2: Literature review Chapter 2 concludes Phase 1 and 1.2 of this study, as presented in the research design.

The current state of South Africa’s high energy demand of coal-powered energy was presented and its relation to using natural resources such as sunlight to power electricity.

The definition of passive solar systems is introduced. A literature review was conducted on pertinent literature of different passive solar systems available in the built environment.

This chapter introduced the first two sub-problems as enumerated in Chapter 1: Sub-problem 1

Sub-problem 2

Will passive solar systems improve residential buildings' indoor thermal comfort and visual comfort in Climatic Zone 2?

Will passive solar systems influence the energy demand of residential buildings in Climatic Zone 2?

Furthermore, thermal comfort and thermal mass were discussed in Chapter 2 and assisted in developing this study's framework.

5.1.3 Summary of Chapter 3: Pilot Study Chapter 3 focused on designing and testing a passive solar system using water as thermal mass to contribute to thermal comfort and energy efficiency in residential buildings.

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Based on results in the pilot experiment, the water absorbed a significant amount of solar energy as heat during the daytime. Water can radiate heat into the room during a cooler evening. Consequently, water is fit to be used as a thermal mass material in a passive solar system. The next section consists of experiments to further test and evaluate the water’s performance to develop and improve the system.

5.1.4 Summary of Chapter 4: Experiments The water bottles can absorb heat energy from the sun during the day and radiate that heat into the room during cool evenings. The system could be installed on the interior during the winter and the exterior during the summer.

By connecting the bottles to a reservoir, the bottles heated the reservoir using the thermosyphon effect. This passive system could heat water in remote areas or preheat a household’s geyser to reduce electricity costs.

5.2

Chapter 4: Findings, conclusions and recommendations

Chapter 4 presented the sub-problems their hypotheses with findings, conclusions, and research recommendations.

The main problem statement was presented in Chapter 1: The main problem is whether passive solar design systems could be implemented in existing residential buildings to improve thermal comfort and energy efficiency while ensuring compliance with the SANS 204 standards for active and passive systems.

Passive solar systems include addressing heat losses, direct solar gains through wall openings and thermal mass. Heat gains and efficient visual comfort can be achieved by controlling natural lighting. This study investigated solar air heating, natural lighting, and thermal mass in the context of operable north-facing windows. The design research focused on passive solar systems by modelling and prototyping a translucent low-tech, passive solar system and introducing water as thermal mass.

The main problem statement was divided into five sub-problems that were posed as questions: •

What impact will passive solar systems have on the indoor thermal and visual comfort of residential buildings in Climatic Zone 2?

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•

What impact will passive solar systems have on the energy demand of residential buildings in Climatic Zone 2?

•

What are the most common and effective passive solar systems in residential buildings?

•

Can water be used as a thermal mass within the design of a passive solar system?

•

What factors influence the implementation of these systems in residential buildings?

The findings, conclusions, and recommendations were gathered from the sub-problems and are presented in Tables 13 to 17.

5.2.1 Sub-problem 1 and resulting hypothesis Table 13: Sub-problem 1, associated hypothesis, findings, conclusion, and recommendation Sub-problem 1

Hypothesis 1

Result

What impact will passive solar systems have on the indoor thermal and visual comfort of residential buildings in Climatic Zone 2?

It is hypothesised that passive solar Hypothesis design systems will improve indoor proved positive thermal and visual comfort in residential buildings.

Findings based on the desk review The literature review determined that passive solar responses are the most effective solutions to improve indoor thermal and visual comfort levels.

Solar systems are often costly to install and cost effective over time.

Conclusion Introducing the correct solar passive systems to a building will reduce the thermal fluctuations within the building, making it a more comfortable building and no need for additional heating and cooling systems.

5.2.2 Sub-problem 2 and resulting hypothesis Table 14: Sub-problem 2, associated hypothesis, findings, conclusion, and recommendation Sub-problem 2

Hypothesis 2

Result

What impact will passive solar systems have on the energy demand of residential buildings in Climatic Zone 2?

It is hypothesised that passive solar Hypothesis proved design systems will improve the energy positive efficiency of residential buildings, decreasing the energy demand of residential buildings.

Findings based on the desk review

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The literature review stated that passive solar responses are the most effective and energy-efficient solutions to improve the energy efficiency of a residential building in Climatic Zone 2 and contribute to positive environmental implications.

Conclusion The heating and cooling systems of a building are a great part of the energy consumption of a building and can be reduced greatly by introducing a passive solar system. These systems reduce the energy demand and have positive implications for the environment. By saving one kilowatt-hour, 0,53kg coal is saved with up to 1kg less CO2 emissions.

Solar systems are the most costly to install and most cost effective over time.

5.2.3 Sub-problem 3 and resulting hypothesis Table 15: Sub-problem 3 associated hypothesis, findings, conclusions, and recommendations Sub-problem 3

Hypothesis 3

Result

What are the most common and effective passive solar systems in residential buildings?

It is hypothesised that passive solar Hypothesis proved systems such as solar air heaters, positive Trombe walls and solar water heating are the most effective passive solar systems used in residential buildings.

Findings based on the desk review The literature introduces passive solar systems such as Trombe wall, water walls, solar water heating, and solar heaters.

Conclusion These are the most common and effective systems used in residential buildings because of their size and cost. These systems can be integrated into the building envelope or installed afterwards.

5.2.4 Sub-problem 4 and resulting hypothesis Table 16: Sub-problem 4 associated hypothesis, findings, conclusions, and recommendations Sub-problem 4

Hypothesis 4

Result

Can water be used as a thermal mass within the design of a passive solar system?

It is hypothesised that water can be used as thermal mass in a passive solar system.

Hypothesis proved positive

Findings based on the desk review and pilot study

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In the literature review conducted, the researcher found that although water has a low density of 1000kg/m3 compared to concrete and brick of 2371kg/m3 and 2611kg/m3, that water has a high heat capacity of 4,18J/K, which is five times the capacity of brick and concrete.

The water in the bottles reached temperatures of up to 60°C during the day due to solar exposure and stayed at least 2°C above room temperature during the night until sunrise the next morning.

Conclusion The high heat capacity of water means that water has a high potential for absorbing heat and can be used as a thermal mass material within a passive solar system.

Recommendation for further study Future research could include investigating, testing, and assessing water, brick, concrete to compare the thermal capacities, thermal absorbing, and time lag.

5.2.5 Sub-problem 5 and resulting hypothesis Table 17: Sub-problem 5, associated hypothesis, findings, conclusions and recommendations Sub-problem 5

Hypothesis 5

Result

What factors influence the implementation of these systems in residential buildings?

It is hypothesised that the main factors Hypothesis influencing the installation are limited proved positive space, high construction costs, and ease of operability.

Findings based on the desk review Solar exposure and radiation are big influences; the system can only contribute during sunny days. The cost of solar systems are very high and take up space.

Conclusion The duration and potency of the solar radiation determine the heat energy absorption of the system. Building a system from low-cost and recycled products lowers the costs.

Introducing the solar systems into the envelope of the building takes less space, save money, and improves the building.

Recommendation based on the findings The systems should be installed to receive the most solar radiation.

Recommendation for further study The system rotates during the day to face the sun and have maximum solar exposure.

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Appendices

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