Yzel, I - The Design of a Low-Tech Solar Heating System for Residential use in Climatic Zone 2 of...

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THE DESIGN OF A LOW-TECH SOLAR HEATING SYSTEM FOR RESIDENTIAL USE IN CLIMATE ZONE 2 OF SOUTH AFRICA

IAN YZEL 209041170

- Research Document by Ian Yzel 209041170 Submitted in partial fulfillment of the requirements for the degree Master of Architecture in Architectural Technology (Structured) at the Department of Architecture and Industrial Design

in the FACULTY OF ENGINEERING AND THE BUILT ENVIRONMENT at the TSHWANE UNIVERSITY OF TECHNOLOGY Supervisor: Prof J Laubscher Co-Supervisors: Mr SP Steyn Mr M van Schoor PRETORIA 2021

Front page - Figure 1: Front page: Nongoma informal settlement: KZN (Author, 2021)

DEPARTMENT of ARCHITECTURE and INDUSTRIAL DESIGN

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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):

Ian Yzel

Student number:

209041170

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 his/her 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.

05 January 2022 Signature

Date

Table of Contents ABSTRACT ................................................................................................................v 1. CHAPTER 1: PROJECT CONTEXT ......................................................................1 2. CHAPTER 2: LITERATURE REVIEW....................................................................5 2.1 Pretoria as study region................................................................................6 2.2 Test results from existing installation ............................................................7 2.3 Internal air circulation ...................................................................................8 2.4 Airborne transmission of infections ...............................................................9 2.5 Heat storage from solar air heater ................................................................9 2.6 Heat storage material and calculations.........................................................9 2.7 Optimum solar angle ..................................................................................11 3. CHAPTER 3: RESEARCH OUTLINE ..................................................................13 3.1 Research Objective ....................................................................................14 3.2 Research Question ....................................................................................14 3.3 Delimitations ...............................................................................................16 3.4 Methodology ...............................................................................................16 3.5 Research Context .......................................................................................17 3.6 Research Paradigm ....................................................................................17 3.7 Research Design ........................................................................................19 4. CHAPTER 4: SYSTEM DESIGN ..........................................................................22 4.1 Concept ......................................................................................................23 -

Detail model of solar air heater Exploded model of rock bed heat collector Exploded model of solar air heater

4.2 Construction of Solar Air Heater .................................................................30 4.2.1 Solar air heater 4.2.2 Rock bed heat collector

5. CHAPTER 5: PILOT STUDY ................................................................................40 5.1 Pilot Study Part 1 ........................................................................................41 5.1.1 Testing equipment 5.1.2 Methodology 5.1.3 Results 5.1.4 Conclusion

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5.2 Pilot Study Part 2 ........................................................................................45 5.2.1 Methodology 5.2.2 Results 5.2.3 Calculations 5.2.4 Conclusions 5.2.5 Alterations and changes

6. CHAPTER 6: DATA PROCUREMENT ................................................................51 Part 3: Introduction ...........................................................................................52 6.1 Full experiment Part 1: Ventilated heating system .....................................52 6.1.1 Introduction 6.1.2 Methodology 6.1.3 Results 6.1.4 Conclusion

6.2 Full experiment Part 2: Enclosed heating system .......................................61 6.2.1 Introduction 6.2.2 Methodology 6.2.3 Results 6.2.4 Conclusion

6.3 Full experiment Part 3: Ventilated cooling system ......................................69 6.3.1 Introduction 6.3.2 Methodology 6.3.3 Results 6.3.4 Conclusion

6.4 Full experiment Part 4: Enclosed cooling system .......................................73 6.4.1 Introduction 6.4.2 Methodology 6.4.3 Results 6.4.4 Conclusion

6.5 Comparison ASHRAE thermal comfort and results from experiment .........79 6.5.1 Ventilated heating system (Winter range 20°C to 23°C) 6.5.2 Enclosed heating system (Winter range 20°C to 23°C) 6.5.3 Ventilated cooling (Summer range 23°C to 26.6°C) 6.5.4 Enclosed cooling (Summer range 23°C to 26.6°C) 6.5.5 ASHRAE standard 6.5.6 Conclusion from comparison

6.6 Application of solar heating/ cooling system ...............................................80 7.2.1 New built solar heating system application 7.2.2 Retrofit solar heating system application

6.7 Cost analysis ..............................................................................................83

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7. CHAPTER 7: CONCLUSION ...............................................................................84 7.4 Recommendation .......................................................................................85 7.4.1 Heating system recommendation 7.4.2 Cooling system recommendation

7.5 Opportunities for communities ....................................................................86 7.5.1 Local labour opportunities 7.5.2 Local economy upliftment

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Water and air, the two essential fluids on which all life depends, have become global garbage cans. ― Jacques-Yves Cousteau

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ABSTRACT According to the latest statistics issued on electricity tariffs in South Africa, the tariffs have increased five times more than inflation between 2007 and 2020. Low-income households often use non-renewable fuels such as coal and paraffin to generate indoor heat to substitute for electricity. Generating heat from non-renewable fuels is the leading cause of indoor air pollution and poor health conditions for the occupants of these households.

The study aims to improve the indoor comfort levels for low-income households by substituting non-renewable fuels. To substitute the use of non-renewable fuels, a costeffective and energy-efficient system should be designed and tested.

To improve the indoor temperature while allowing for ventilation, a solar heating system with heat storage capacity was developed by evaluating existing studies on solar air heaters and heat storage materials and systems. The heating system was constructed and tested to determine its effectiveness. Through developing a cost-effective solution, the study investigated the possibility of constructing the solar heating system from waste and off-cut materials. If solar heating can be implemented successfully, the aim is to substitute nonrenewable fuels. The system will assist with internal ventilation and limit the spread of viruses or infections within enclosed spaces. The proposed heating system will transfer the external, ambient air through the system and allow heated fresh air to enter the housing units without opening windows or doors during the winter season.

The study was carried out with the following components: a solar air heater with dimensions of 1000mm (L) x 500mm (W) x 100mm (H) and a rock-bed heat collector.

A study was conducted to observe the performance of the rock bed heat collector when using different types of rocks to store heat and various positions, layouts, and arrangements for the system to make recommendations regarding optimal performance.

The data acquired from the pilot study was implemented to conduct the final study to determine the effectiveness of the solar heating system. The study used the minimum ASHRAE human comfort levels to assess the efficacy and cost-effectiveness of the design proposal.

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Through testing the proposed heating system, it was anticipated that the indoor temperature and airflow would improve through iterative design. Suppose the use of non-renewable fuels can be replaced by implementing the solar heating system; in that case, the thermal comfort levels of informal dwellings can be improved without reliance on harmful sources of energy.

Keywords: Air pollution, non-renewable fuels, conventional heating, fresh air, rock bed heat collector, alternative heating system, renewable energy, cost-effective.

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PROJECT CONTEXT • History of informal settlements • Existing population of informal settlements in South Africa • Contributing factors to poor indoor thermal comfort • Focus of the study

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1. PROJECT CONTEXT Informal dwellings can be defined as unplanned housing units on land which has not been surveyed or proclaimed (HDA 2017: 8). Furthermore, an informal dwelling can be defined as a makeshift structure without the approval of the Local Municipality. The data published by the Housing Development Agency (HDA) of South Africa (2017) indicates that the number of households living in informal settlements in South Africa stands at a total of 1,249,777 households, containing 3,306,697 individuals with an average of 2,6 people per household of 2 to 3 individuals (HDA 2017: 18).

In a study by the Department of Environmental Affairs (DEA) of South Africa on dense, lowincome households with an income below R3 500 per month, a need is identified to address the impact of air pollution generated from the burning of non-renewable fossil fuels for indoor temperature regulation. (Government Gazette no. 40088, 2016: 11, 23). Information obtained on the ambient air quality from more than 90 monitoring stations identified geographical areas within Gauteng, Free State, Mpumalanga, Limpopo, Northwest, and Western Cape Province, which have polluted ambient air above 50µg/m3 and proved to be unhealthy for human inhabitation (Government Gazette no. 40088, 2016: 8). Due to the lack of thermal insulation in the walls, floor, and roof, the internal temperature of an informal dwelling can differ between as little as 4-5˚C from the ambient temperatures during the winter season (Naicker et al, 2017: 1).

Low-income households burn paraffin or coal (alternatively referred to as non-renewable fuels) within living spaces to generate heat. A research study published by the South African Department of Environmental Affairs (DEA, 2008) has indicated that six metropolitan areas in South Africa are responsible for 69% of the ambient air pollution in the selected geographical areas (Friedl et al, 2008: 2). The study also estimated that 9 000 deaths are caused annually in South Africa due to indoor air pollution from non-renewable fuels.

Therefore, it is essential to investigate, identify and develop an alternative indoor heating method. One such method is solar energy that is both renewable and non-toxic when implemented. Informal dwellings was the focus of the case study.

According to a study published by the World Health Organization (WHO), it was found that the rate of spread of viruses and infections in enclosed and poorly ventilated rooms is much

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higher compared to ventilated spaces (WHO, 2020). It is anticipated that the proposed heating system can improve ventilation by replacing the internal air with warmed fresh air.

The fresh air enters from the bottom of the solar air heater and replaces the internal air.

The proposed study will address indoor air pollution and improve the indoor temperature.

The study will focus on providing a cost-effective and energy-efficient solution for indoor space heating. The integrated indoor heating system should be designed to be retrofitted to any informal dwelling at an affordable price.

The study will also focus on creating job opportunities by making use of local labour within low-income communities. The construction of a solar heating system will require the skills of an electrician, plumber, and carpenter.

Figure 2 illustrates the proposed concept design of the solar air heating system, which will be developed and tested further in Chapters 5 and 6.

Figure 2: Typical illustration of proposed heating system experimental set-up during the winter season (Author, 2021).

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Figure 3 below illustrates the proposed concept design of the solar air heating system, which can be utilised for cooling during the summer season. The concept will be developed, tested, and discussed further in Chapters 5 and 6.

During the evening, the cool ambient airflow through the system cools the rocks. The hot internal airflow over the rocks during the daytime. When implementing the system to a house, the warm air from the internal space will be extracted to flow through the rock bed, transfer heat to the rocks and cool down the air, which will be supplied back to the internal space.

Figure 3: Typical illustration of proposed cooling system experimental set-up during the winter season (Author, 2021).

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LITERATURE REVIEW • • • • • • • •

Chapter 2: Introduction Study region Results from previous studies Air circulation Airborne transmission of infections Heat storage from solar air heater Heat storage material and calculations Optimum solar angle

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2. INTRODUCTION Chapter 2 discusses various topics supporting the study, which will be used throughout the document. This chapter will focus on previous studies, existing problems, and information to form a base for the study.

2.1 Pretoria as the study region A survey (Census, 2019) was carried out on 11 783 798 households to determine the total number of “shacks not in a backyard” (referred to as informal dwellings in this study) in South Africa. The results from the survey indicated that nationally, 1 375 858 households make use of an informal dwelling. The survey indicated that 448 383 households in Gauteng use informal dwellings — this was the highest of all provinces (HDA, 2019:44). Furthermore, the survey results indicated that in Gauteng, Tshwane, and Johannesburg have the highest informal dwellings at 216 066 households (HDA, 2019:46).

The annual mean temperature in Pretoria is 18.25 C° (using the annual maximum and minimum temperatures). During May to August (winter season), the average temperature is 13.5 C° (Climate-data.org, 2020). According to the Koppen-Geiger climate classification, Pretoria is classified as ‘humid subtropical’ with cold interior temperatures (Kottek et al., 2006). Pretoria has almost no rainfall during the winter season, with 28 days of sunshine each month from May-August. Therefore, the experiment will be conducted in Pretoria, situated in climatic zone two (temperate interior) of the South African climatic zones map (SANS 204:2011: 30).

A further study can be done by testing the system on informal dwellings in the remaining regions and climate zones.

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Figure 4: Map of South Africa and Gauteng (Vectorstock, 2021)

2.2 Test results from existing installations Classrooms in New Zealand are grossly under-ventilated in cold weather and have excessively high bacteria levels, potentially leading to adverse respiratory infections and other health effects (Bassett et al., 1999, McIntosh 2011). Nearly all New Zealand classrooms depend entirely on natural ventilation via open windows (Cutler-Welsh, 2006).

The school days are in line with the availability of solar radiation. Therefore, it is found that schools are the ideal environment for utilising solar air heaters for indoor heating and ventilation (Boulic et al., 2014: 1).

The problem identified within the classrooms of New Zealand is similar to that identified within the informal dwellings based in South Africa. The system was implemented to address under-ventilated spaces, high levels of bacteria, and indoor temperatures.

The results proved that solar air heaters, with the dimension of 75 mm x 3 000 mm x 1 020 mm (3m²) constructed from a 6 mm thick transparent cover, 2 mm thick black felt absorbent layer, perforated aluminium backplate, and 18-watt photovoltaic panel, providing electricity to the circulation fan, can generate sufficient heat for a classroom of 200 m² (Boulic et al., 2014: 2).

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The results showed that the intervention positively impacted the school environment with decreased carbon dioxide levels and 2,5 times less energy consumption (Boulic et al., 2014: 3).

The study on classrooms shows that human comfort levels can be improved by using a solar air heater system by improving indoor temperatures and air quality. The solar air heater still requires a circulation fan assisting with the indoor air ventilation and a method to store heat.

2.3 Internal air circulation In Switzerland, an investigation was done using a vertical, wall-mounted solar air heater (13.1m x 2.2m) with an electrical fan to circulate fresh air into an industrial building to improve the indoor air quality and temperature (Sicre and Baumann 2015: 140).

The industrial building does not have any thermal insulation other than the sheet metal skin of the building with a floor area of 300 m² and 8.2 m high; the total volume of the structure is 2 460 m³. The scale of this project is larger than the proposed housing units used in this study; however, the solar air heater should be able to perform equal or better on a smallscale project like the industrial building (Sicre and Baumann 2015: 139).

The data gathered from the study indicated that the solar air heater replaced the indoor air sufficiently at a flow rate of 50m³/h per 1m² from provided by a 28m² solar-air heater. The air within the building was replaced by fresh air within 1 hour 35 minutes, which indicates that, on a larger scale, using a solar air heater for ventilation proved efficient. The solar air heater produced an average of 30°C of heating into the indoor space over three months (Sicre and Baumann 2015: 142).

The similarity between the industrial building and the informal-dwelling units is that both are constructed primarily from sheet metal and a mild steel frame with no additional thermal insulation in the walls or roof to improve the thermal comfort levels. Although there are similarities between the industrial building and the housing units, the system should still be tested in a controlled environment in South Africa to obtain results that can be used in a further study to implement the system on informal dwellings.

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2.4 Airborne transmission of infections According to a study by the KTH Royal Institute of Technology, it was found that tuberculosis is one of the top ten causes of death and is spread through the air. Ten million people fell ill with tuberculosis, and 1.5 million people died in 2018. Furthermore, it was found that an infected person spreads these viruses into the air by coughing, sneezing, or spitting. Only a few germs are required to be inhaled to infect another person (Lutzow & Mikiver, 2020:6).

According to a World Health Organization (WHO) study, the spread of these viruses can be reduced when internal spaces are ventilated by replacing the internal air approximately three times per hour (WHO, 2020). It is anticipated that the spread of these viruses can be reduced when implementing a solar heating system with fresh air circulation.

2.5 Heat storage from the solar air heater When a solar air heater is used in conjunction with a rock bed, the rock bed can store heat for optimal efficiency and supply heat during the evening (Marongiu, Soprani, Engelbrecht, 2019: 1). Developing a cost-effective solar air heater that can be constructed from waste material will enable communities to construct their own solar heating systems.

According to a study by Politeknik Dergisi (2020), it is found that a solar air heater can be constructed from waste materials and still be effective (Sözen et al., 2020: 9). Further in the study, it was indicated that a solar air heater, constructed from waste materials, increased the thermal internal comfort levels between 33% and 42% (Sözen et al., 2020: 6).

2.6 Heat storage material and calculations A study was conducted to investigate the possibility of storing heat within a rock, water, and phase change materials (Eckhoff and Okos 2013: 2). After comparing the three alternatives, it was found that rock would be the best material for heat storage on a solar air heater system, which uses air to transfer heat (Eckhoff and Okos 2013: 5). Once the system is installed, maintenance is minimal, and few elements can decrease the performance of the storage (Eckhoff and Okos 2013: 2). Furthermore, rock is readily available and affordable and relatively easy to compose, compared to water and phase change material which can also be used as heat storage materials. From previous test results, rocks between 100 mm

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to 150 mm with round edges have shown the best results to store heat with airflow velocity at 10 m per second. The rocks must be free of dust and small stones, which will restrict airflow (Eckhoff and Okos 2013: 6).

Table 1: Heat storage characteristics of rock (Eckhoff and Okos 2013: 4) HEAT STORAGE CHARACTERISTICS OF ROCK Storage material

Bulk density

Specific heat

Imperial information Rock

100lb/ft³

0.2BTU/lb.°F

Metric translated information Rock

1601.8kg/m³

0.658J/kg.°C

The information in Table 1 will be used in Table 2 to determine the amount of rock required to discharge sufficient heat into a room or space. Table 2 will indicate the formula used in Chapter 4 to calculate the amount of rock required for the experiment.

The information available from the study conducted is all in imperial format. It will be translated to the metric format as indicated in Tables 1 and 2. Table 2 is utilised to determine the amount of rock required for a specific room/ space as heat storage material.

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Table 2: Calculation for heat storage material required (Eckhoff and Okos 2013: 6) VOLUME OF ROCK REQUIRED AS STORAGE MATERIAL Description

Example

Example (Metric)

(Imperial) a

Heating requirement of space/ room

15000BTU

4396 Watt/ hour

b

Duration for the heat required

24 hours

24 hours

c

Storage reserve

3 days

3 days

d

Total heat required (a x b x c)

1 080 000BTU

316 512 Watt/ hour

e

Bulk storage material (table 1)

100lb/ft³

1601.8kg/m³

f

Specific heat storage material (table 1)

0.2BTU/lb°F

0.658J/kg.°C

g

Temperature range

50°F

10°C

h

Heat from storage material (e x f x g)

1000BTU/ft³

10 550.4 Watt/m³

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Storage material required (d / h)

1080ft³

30m³

2.7 Optimum solar angle According to a study conducted by the Department of Mechanical and Aeronautical Engineering at the University of Pretoria, the optimum tilt and azimuth angles were determined through a system called Solys 2 tracking system. Furthermore, the system was used to track the solar exposure for 365 days in Bloemfontein, Durban, Graaff-Reinet, Pretoria, Richtersveld, Stellenbosch, Van Rhynsdorp and Vryheid (Le Roux, 2019: 6). The azimuth is the angle between the horizontal axes and vertical perpendicular axes.

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The study proved that a solar panel at the optimum tilt and azimuth angle could generate 10% more solar energy when placed in a fixed position. A solar panel tracking the sun’s movement can generate, on average, 45% more solar energy (Le Roux, 2019: 17). The results from the study are tabled below: Table 3: Optimum solar angles (Le Roux, 2019: 15).

Study Results Location Optimum Tilt

Optimum Azimuth

Bloemfontein

28⁰

6⁰

Durban

29⁰

8⁰

Graaff-Reinet

29⁰

-7⁰

Pretoria

26⁰

4⁰

Richtersveld

26⁰

-14⁰

Stellenbosch

27⁰

-4⁰

Van Rhynsdorp

27⁰

-12⁰

Vryheid

29⁰

1⁰

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RESEARCH OUTLINE • • • • • • • •

Chapter 3: Introduction Research objective Research questions Delimitations Methodology Research Context Research Paradigm Research Design

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INTRODUCTION

Chapter 3 sets an outline of the research document, which will be used throughout. This chapter discusses the following aspects: • • • • • • •

Research objective Research questions Delimitations Method Research Context Research Paradigm Research Design

This chapter ends with the design summary, which combines the process of unfolding the research document.

3.1 RESEARCH OBJECTIVE The study aims to determine the potential use of a solar air heating system with heat storage material (rock) by testing the system’s performance as an alternative method for indoor heating and ventilation in informal dwellings based in South Africa.

Consequently, the objectives of the study are: 3.1.1 To acquire the initial ambient temperatures.

3.1.2 To acquire specific temperature and solar radiation data to identify indoor comfort levels defined by ASHRAE comfort models.

3.1.3 To conduct a detailed experiment by constructing the solar heating system with all its parts.

3.1.4 To analyse the data and determine findings and infer recommendations.

3.2 RESEARCH QUESTIONS: A solar air heating system is proposed to address the current living conditions and thermal comfort levels in informal dwellings by testing the potential use of a cost-effective and energy-efficient heating system. The occupants of the identified dwellings generally cannot afford to purchase electricity for space heating. The households instead make use of affordable non-renewable fuel resources; however, they compromise their health in the process. A rock-bed heat collector will be combined with a solar air heater system to produce sufficient heat during the day and night. The study will focus on informal dwellings based in

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South Africa. The current problem identified for informal dwellings is uniform across all lowincome communities.

The main problem is divided into sub-problems with the related hypothesis in Table 1 below.

Table 4: Integrating the main aim, sub problem and hypotheses SUB-PROBLEM (1 - 5)

HYPOTHESIS (1 – 5)

(Posed as a question) Sub-Problem 1:

Hypothesis 1:

What alternative method of heating is It is hypothesised that a solar air heating system available without using hazardous fuels can be used as an alternative heating method to generate sufficient indoor heat? by using solar energy in South Africa.

Sub-Problem 2:

Hypothesis 2:

How can a solar-air-heater system improve indoor air quality?

It is hypothesised that when a solar-air-heater system with a solar-powered fan and rock bed heat collector is implemented, the system will circulate and replace internal, stale air with cleaner external air.

Sub-Problem 3:

Hypothesis 3:

How will the solar air heater store sufficient heat to be used during the evening if the system relies only on solar energy?

It is hypothesised that a solar air heater system combined with a rock bed heat collector to store heat during the day could discharge heat that can be used during the evening.

Sub-Problem 4:

Hypothesis 4:

Can the system produce sufficient heat It is hypothesised that the proposed system can and ventilation? produce sufficient heat and ventilation.

Sub problem 5:

Hypothesis 5:

Will the resulting system be costeffective for low-income communities?

It is hypothesized that constructing a solar air heater with a rock bed is an affordable heating method with low maintenance costs for lowincome communities.

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3.3 DELIMITATIONS The following delimitations are applicable to the study: 3.3.1 The proposed study will investigate the performance of the rock bed heat collector by providing heat during the evening.

3.3.2 Weather data from Pretoria will be obtained to compare the effectiveness of the system.

3.3.3 The study will aim to improve internal airflow but will not pay attention to the health impact of occupants due to the polluted air and deaths caused by polluted air.

3.3.4 The study will address the internal temperature.

3.3.5 The focus of the study will not be on the thermal performance of the external envelope.

3.3.6 The focus of the study will be to provide a heating system that is not reliant on electricity or non-renewable fuels to create a healthier environment for low-income households.

3.3.7 The study will not involve heat-storage materials other than rock.

3.4 METHODOLOGY The proposed study will be done through iterative design development research. The results from the experiment will be used to determine if the system will improve the internal temperature and facilitate ventilation during both day and night. The ambient temperature readings during the experiment will be used to determine the effectiveness of the system.

3.4.1 Phase 1: Pilot Study (Chapter 3) The study will consist of the following three phases: •

Phase 1 – Pilot study,

•

Phase 2 – Data procurement, and

•

Phase 3 – Design iteration.

During the pilot study, a basis for the study will be formed by gathering information on each component used during the test. Data from previous studies will be used to determine the optimum size of the solar air heater and the rock bed heat collector. The solar air heater will be tested to determine the total heat generated during the day. The rock bed heat collector will be connected to the solar air heater to test the heat storage capacity of the rock bed.

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3.4.2 Phase 2: Data procurement (Chapter 4 & 5) During Phase 2 of the study, the three components tested in the pilot study will be connected. The test during Phase 2 will determine the performance of the solar air heater during the day and night. The results from the pilot study are used to indicate the heat loss factor between the components. The experiment will be done in isolation to determine the optimum performance without any tampering on the system. The results will indicate whether the thermal comfort increases when the solar air heater system with the rock bed heat collector is implemented.

3.4.3 Phase 3: Design iteration (Chapter 6) During Phase 3, the experiment will be conducted through iterative design development research by testing the solar heating system over multiple days during both the summer and winter seasons. The potential for space heating will be tested over multiple days to explore the possibility of seasonal charging.

The solar heating system will be tested during the summer season to determine the potential to cool internal spaces. The solar air heater will be covered and inactive during the summer to limit solar energy and heat. The methodology will be discussed further in chapter 6, parts 3 and 4.

After completing phases 1, 2, and 3, a feasibility study will be done to determine the exact cost of the system to be constructed from waste or off-cut materials available in low-income communities.

3.5 RESEARCH CONTEXT The research context was formed through research done on previous studies published about the existing real world problem and previous experiments done on a solar air heater in combination with a rock bed to address the problem of indoor air pollution.

3.6 RESEARCH PARADIGM Table 5 communicates the researcher’s normative position regarding the positivist and interpretivist research paradigms, using a scale of predispositions formulated by Laubscher (2011:15):

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Table 5: The researcher’s paradigm indicated on the model developed by Laubscher (2011:15) RESEARCHER’S PARADIGM

Meta-theoretical assumptions

Ontology

Detached experience Person (researcher) and reality are separate.

Epistemology

Objectivity Objective reality exists beyond the human mind.

Research object

Separate The research object has inherent qualities that exist independently from the researcher.

Research method

Content analysis through statistics Preferred research methods include laboratory experiments, field experiments, surveys, etc.

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.

~

Strongly Agree

Agree

Neutral

Alternative terms: Quantitative, scientific, experimental, hard, reductionist, prescriptive, psychometric, etc.

Disagree

+

Pre-disposition of the researcher on a continuum scale Strongly Disagree

Positivism

Interpretivism

Alternative terms: Qualitative, soft, non-traditional, holistic, descriptive, phenomenological, anthropological, naturalistic, illuminative, etc.

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, phenomena-graphic studies, ethnomethodological studies, etc.

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.

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Normative position of the researcher:

The researcher can separate himself from the research process. The researcher can only be isolated from the process for not less than a week.

An objective thought process will be followed, focusing on facts and observations from the research.

The research object exists independently from the researcher and won’t be affected by the researcher’s experience. However, since the experimental setup is a design project, the researcher’s frame of reference will influence the trajectory of the study, and new data may reframe the original research questions.

The primary method for obtaining data will be through the use of data loggers. The use of surveys will also be implemented to obtain information on the knowledge of this research topic.

The researcher has no previous experience or involvement with this study; therefore, the outcome will not be influenced by past familiarity.

There is a direct connection between the data composed and the results thereof. The researcher will be observant and truthful throughout the research process.

It is possible that the study can be repeated by different researchers, but the outcome may vary because of environmental circumstances.

3.7 RESEARCH DESIGN The relationship between the research question, data required, and data analysis constitute the basis of the research design. Fellows and Liu argue that the definition of different research styles varies to such an extent that the boundaries between different styles are not well defined (2003:21). However, in Research Methods for Construction, Fellows and Liu (2003:21-28) discuss different research styles and strategies according to the respective authors in Table 6 below.

Table 6: Summary of research styles Research styles/strategies Research styles as termed by Bell (1993) (as cited in Fellows & Liu, 2003: 21-28)

Research strategies as termed by Yin (1994) (as cited in Fellows &

Implementation in the proposed (1997) (as cited in Fellows & Liu, 2003: 21-28) study Shortened description as defined by Fellows and Liu

Liu, 2003: 21-28)

Action

Research intentionally attempts to affect change in the social system.

Not applicable

Ethnographic

A scientific study of races and cultures involving the hermeneutic circle.

Not applicable

Histories

The past is studied based on the research questions

Yes

‘How?’ and ‘Why?’ Archival analysis

Present or past is studied; little control over independent variables is required.

Yes

Surveys

Surveys

Statistical sampling represents a population and often employs questionnaires and interviews.

Not applicable

Case studies

Case studies

An in-depth investigation of certain aspects through interviews with key’ factors.’

Partially

This is usually conducted in laboratories to determine the relationship between variables.

Yes

Experiments Experimental

(Including quasiexperiments)

Using the format and outline developed by Laubscher (2011: 19), the different phases of the research design are communicated in Table 7.

19

Table 7: Summary of the research design RESEARCH DESIGN: IMPLEMENTATION OF SOLAR AIR HEATER WITH HEAT STORAGE MATERIAL AS AN ALTERNATIVE HEATING SYSTEM ON RDP AND INFORMAL DWELLINGS IN CLIMATIC ZONE 4 OF SOUTH AFRICA. PHASE 1: A REVIEW OF APPLICABLE LITERATURE PHASE 1.1 (Refer to Chapter 2)

Theme: Thermal comfort (Indoor ventilation and temperature) Focus area: Informal dwellings in dense low-income communities Data source: Selected literature 1.1 Understanding the current problem identified for space heating in informal dwellings.

1.2 Determine the minimum requirements and standards for indoor air quality 1.3 Shortly describe the current methods of indoor heating 1.4 Briefly describe the impact of the current methods used for heating in informal and RDP dwellings PHASE 1.2 (Refer to Chapter 2)

Theme: Climatic classification Focus area: Identifying the available alternative methods for indoor heating Data source: Relevant Literature 1.2.1 Investigate the available alternative methods of heating that can benefit the study and the community 1.2.2 Determine the viability of the proposed heating system proposed in the study through previous studies conducted 1.2.3 Investigate and analyse previous applications and results of the proposed heating system in regions with similar environmental characteristics. ▼

PHASE 2: PILOT STUDY PHASE 2.1: (Refer to Chapter 5) Theme:

Experiment

Focus Area:

Determine the appropriate size of the solar air heater and rock bed heat collector applicable to the volume of the units used in the study.

Data source:

Research material and computer analysis

2.1.1

Determine the size/ ratio of the solar air heater when taking into consideration the floor area of the housing units and also the type of material to be used for the solar air heater for optimal performance.

2.1.2

Determine the size of the rock bed heat collector to be constructed for sufficient heat storage. ▼

20

PHASE 2.2 (Refer to Chapter 5) Theme:

Testing of measuring instruments

Focus Area:

Determine the accuracy of the data obtained from the simulation when comparing the results with the results of previous studies and experiments

Data source:

Research material + experiment results

2.2.1

Determine the effectiveness of the experiment compared to the results of previous studies conducted and weather data of Pretoria to determine the viability of the study. ▼

PROGRESS REVIEW (See note1) NOTE1: When conducting a progress review, the researcher should decide whether a further investigation into the thermal performance of insulation materials will be beneficial to the study. ▼

PHASE 3: DATA PROCUREMENT (cf. Chapter 6) Theme:

Collection data

Focus area:

Data collection from the experiment when implementing the system

Data source:

Experiment

3.1

Determine the correct size and ratio of the solar air heater and rock bed on an informal dwelling.

Use the annual weather data to determine the effectiveness of the system.

3.2

▼

PHASE 4: DATA INTERPRETATION (cf. Chapter7) 4.1

Analysis of data collected and compared

4.2

Statistical description and analysis of the data

4.3

Interpretation of the data ▼

PHASE 5: FINDING & CONCLUSION (Chapter 7) Recommendation and conclusion deduced from the produced and analysed data during chapters 4 and 5. ▼

PHASE 6: PROPOSAL Proposal to implement the solar air heater system in informal dwellings for better thermal comfort and the lowering of air pollution.

21

SYSTEM DESIGN • Chapter 4: Introduction • Concept designs - Detail model of solar heating system - Exploded model rock bed heat collector - Exploded model of solar air heater • Construction of Solar Heating System - Solar air heater - Rock bed heat collector

22

4 INTRODUCTION Chapter 4 presents the concept development of the solar heating system. The concepts are presented through annotated hand sketches. The chapter also presents the concept sketches developed into 3D rendered models. The chapter discusses the materials used for constructing the full-scale model to be tested in chapters 5 and 6. The chapter ends with calculating the amount required for the rock bed heat collector to determine the size of the box to be constructed.

4.1 CONCEPT The basic principles of the proposed solar heating system are based on a solar air heater providing heat during the day and a rock bed heat collector storing heat during the day to produce heat during the evening.

Figure 5 illustrates the concept of the solar heating system. The ambient air enters the solar air heater from the bottom, and exchanges heat between the air and the heat collector plate.

The heated air is transferred through the solar air heater into the rock bed heat collector. It is anticipated that the heat from air flowing from the solar air heater is transferred to the surface and core of the rocks.

The heat is stored within the rocks during the evening by circulating air through the rock bed into a room or space.

Figure 5: Concept diagram drawing of solar air heater and rock bed heat collector (Author, 2021).

23

Figure 6 illustrates the concept sketches of the solar air heater to be used for the experiment. The solar air heater will be constructed from waste and off-cut materials as per section 4.2.

Figure 6: Concept diagram drawing of a solar air heater (Author, 2021)

24

Figure 7 illustrates the obstacles placed within the solar air heater to increase the heat transfer rate between the air and backing plate. Obstacles increase the time the airflow through the solar air heater and therefore increase the heat transfer rate.

Figure 7: Concept drawing of obstruction in solar air heater (Author, 2021).

25

Figure 8 illustrates that the rock bed heat collector consists of an inner and outer envelope.

The outer envelope consists of a 19mm thick timber shutter board with a 50mm thick polystyrene insulation between the inner and outer envelope.

The inner envelope consists of a 19mm thick timber shutter board filled with 100mm 150mm rock to capture the heat from the solar air heater.

The box will have an inlet for hot air from the solar air heater and an outlet for heat from the rock to be circulated into a room or space.

Figure 8: Concept drawing of rock bed (Author, 2021)

26

Figure 9 illustrates the complete solar heating through a concept model, which will be used during the experiment to determine the efficiency. The concept model consists of the solar air heater fixed on the enclosed rock bed heat collector box. As indicated in the literature review section, the optimum tilt angle for Pretoria is 26°; this will be the angle of the solar air heater during the experiment.

Figure 9: Concept model of complete solar air heating system to be tested during the experiment (Author, 2021)

27

Figures 10 and 11 below illustrate the concept models illustrate the exploded view of the rock bed heat collector and the solar air heater with all the components.

Figure 10: Concept model: Exploded view of rock bed heat collector box (Author, 2021)

28

In Figure 11, the exploded concept model of the solar air heater is illustrated.

Figure 11: Concept model: Exploded view of a solar air heater (Author, 2021).

29

4.2 CONSTRUCTION OF SOLAR HEATING SYSTEM Most of the materials to construct the solar heating system was procured from local resources or waste and off-cut materials from previous construction projects. The electrical components such as the electric fan and solar panel were bought from an electronics shop.

In this section, the materials used during the construction process are documented. The materials are grouped for the construction of the solar air heater and the rock bed heat collector. Each item will indicate the original use, origin (if applicable), type of material and the material’s use for the project.

4.2.1 Solar air heater: 4.2.1.1

Heat collector plate and obstruction material

The original use of material: 0,8mm thick Chromadek roof sheeting.

Origin: Obtained from scrap metal yard in Silverton, Pretoria.

Use of material: The material is used for the heat collector plate of the solar air heater.

Cost: R10 per/kg with a total cost of R70.00.

The material was cut to size to fit the internal dimensions of the solar air heater.

Figure 12: Chromadek roof sheet (Author, 2021)

Figure 13: Obstacles in solar air heater (Author, 2021)

30

4.2.1.2 Timber frame The original use of material: 152mm x 38mm SA Pine roof trusses.

Origin: Obtained from a construction project; the material was removed and redundant.

Use of material: Main external frame of the solar air heater.

Cost: No cost, redundant material from a construction project.

Figure 14: SA Pine timber frame for solar air heater (Author, 2021)

Figure 15: SA Pine timber planks

4.2.1.3 Glass panel The original use of material: Off-cut glass from large panes cut to size for window frames.

Origin: Off-cut glass obtained from BJ Glass and Aluminium in Silverton, Pretoria.

Use of material: Translucent panel over solar air heater box.

Cost: R30.00

Figure 16: Glass panel (Author, 2021)

31

4.2.1.4 Insulation The original use of material: Bubble wrap packaging material and used newspapers.

Origin: Obtained from a waste bin in Silver Lakes, Pretoria.

Use of material: Insulation material between the heat collector plate and backing board.

Cost: No cost.

Figure 17: Newspaper insulation (Author, 2021)

Figure 18: Bubble wrap insulation (Author, 2021)

In Figures 17 and 18, the newspaper was placed on the heat collector plate with the bubble wrap placed on top of the newspaper to act as insulation material to prevent heat loss from the solar air heater.

32

4.2.1.5 Backing board The original use of material: Timber courier box for fragile items.

Origin: Put out as waste by neighbouring house Use of material: 20mm Thick backing board for solar air heater box.

Cost: No cost.

The timber courier box was dismantled and cleaned.

Only the timber without any water damage was used for the construction of the solar air heater.

Figure 19: Timber courier box (Author, 2021)

4.2.1.6 Solar panel and circulation fan Origin: The solar panel and circulation fan was bought from Electronics FG Description: The circulation fan is 12 V, 1,5 Watt with a 12 V, 5 Watt solar panel fixed to the front of the solar air heater.

Cost: Total cost R168.00 The total cost of the solar air heater will be discussed further in Chapter 7.

Figure 20: Circulation fan (Author, 2021) Figure 21: Solar panel (Author, 2021)

33

4.2.1.7 Complete solar air heater box: In Figure 22, the complete solar air heater box, which will be used during the pilot study in Chapter 4.

The internal surface of the solar air heater was painted black to increase the heat generated.

The box consists of the main frame, translucent glass panel, heat collector plate, circulation fan, solar panel, backing board, insulation, and black paint for the internal surface.

Figure 22: Complete solar air heater (Author, 2021)

4.3 CONSTRUCTION OF ROCK BED HEAT COLLECTOR To enable the system to store heat generated from the solar air heater, a rock bed heat collector will be utilised with the solar air heater to store the heat.

The rock bed heat collector will be constructed from waste or off-cut materials. The rock bed heat collector needs to be insulated to reduce the heat-loss factor when the rocks within the box are charged during the day. The rock bed heat collector has a size of 500mm x 500mm x 1000mm and can store 0.25³ of rock. The rocks within the box will be 100mm to 150mmØ in size, as indicated in the literature review in Chapter 3.

All of the materials used to construct the rock bed heat collector are off-cut and waste materials available from previous construction projects and dumpsites. Below are the materials used for the construction of the rock bed heat collector.

34

4.3.1 Rock bed heat collector 4.3.2.1 Envelope construction The original use of material: 19mm Thick timber shutter board.

Origin: Off-cut timber obtained from a previous construction project Use of material: External envelope constructed from the timber shutter board.

Cost: No cost The timber shutter board was cut to size to construct a 1000mm x 500mm x 500mm box filled with rock. The internal surface is to be covered with insulation material to prevent heat loss.

Figure 23: Off-cut shutter board (Author, 2021) (Author, 2021)

Figure 24: Construction of heat collector box

35

4.3.2.2 Insulation material The original use of material: 50mm Thick polystyrene packaging material Origin: Waste bin in Silver Lakes, Pretoria.

Use of material: The polystyrene material was used to insulate the envelope of the rock bed heat collector.

Cost: No cost The insulation material used to construct the rock bed heat collector was obtained from a waste bin where packaging material is disposed of. The polystyrene was in different sizes and shapes and was cut to fit the internal surface of the box.

Figure 25: Insulation in waste bin (Author, 2021)

Figure 26: Bulk insulation obtained (Author, 2021)

Figure 27: Insulation fixed to timber box (Author, 2021)

36

4.3.2.3 Heat storage material The original use of material: Excavated slate rock from a construction site.

Origin: Obtained from a construction site in Olympus, Pretoria.

Use of material: The rock is used as heat storage material in the rock bed heat collector box.

Cost: No cost The nominal size of the rocks should be between 100mm and 150mm dia. for optimum performance, as indicated in the literature review in Chapter 3.

Figure 28: Rocks from a construction site (Author, 2021)

Figure 29: Size of rocks obtained (Author, 2021)

37

4.3.2.4 Circulation pipes The original use of material: Redundant 50mmØ plumbing pipes.

Origin: Off-cut pipes obtained from a construction site in Olympus, Pretoria.

Use of material: The pipes transfer the air from the solar air heater through the rock and out into the living space or room.

The U-PVC bents required for the project were bought from Plumblink to connect the pipes.

Cost: R64.00 The inlet pipes are connected to the top of the solar air heater and the top and the outlet at the bottom of the rock heat collector box. The hot air must flow over the rock before the air reaches the outlet pipe. The outlet of the rock bed heat collector will supply hot air to a space or room when implemented on a house.

Figure 30: Placement of U-PVC pipes

Figure 31: Inlet pipe to rock bed heat collector

Figure 32: Outlet from rock bed heat collector

38

4.3.2.5 Rock bed The size of the rock bed heat collector box was determined by the amount of rock required for the system. In Table 8, the amount of rock required for the rock bed heat collector is calculated in accordance with Table 2 of Chapter 2. The calculation will be based on a 1m³ space/ room, which requires heat for 12hours per day.

Table 8: Total rock required for heat storage.

VOLUME OF ROCK REQUIRED AS STORAGE MATERIAL

a

Description

Imperial

Metric

Heating requirement of space/ room of

968BTU

283 Watt/ hour

1m³ b

Duration for the heat required

12 hours

12 hours

c

Storage reserve

0 days

0 days

d

Total heat required (a x b x c)

11 616BTU

3396 Watt/ hour

e

Bulk storage material (table 1)

100lb/ft³

1601.8kg/m³

f

Specific heat storage material (slate)

0.18BTU/lb°F

0.658Watt/kg.°C

(table 1) g

Temperature range

70°F

21°C

h

Heat from storage material (e x f x g)

1260BTU/ft³

22 133.67 Watt/m³

i

Storage material required (d / h)

9.2ft³

0.26m³

4.4 CONCLUSION According to the calculations in Table 8, a total of 0.26m³ of rock is required to discharge heat to a volume of 1m³ for 12 hours during the night-time.

The results will be carried over to Chapter 5 to implement and test the heat storage efficiency of the rock through a pilot study. The full-scale model constructed from the waste and off-cut materials will be utilised in chapters 5 and 6 to test the system's performance in a controlled environment.

39

PILOT STUDY • Chapter 5: Introduction • Pilot study (Part 1) - Test equipment - Method - Results - Conclusion • Pilot study (Part 2) - Method - Results - Calculations - Conclusion - Alterations and changes

40

5

INTRODUCTION

Chapter 5 presents the testing equipment utilised for both the pilot study in Chapter 5 and the main study in Chapter 6. The Chapter focuses on the pilot study conducted to determine the system's efficiency prior to conducting full experiment. The results from the pilot study are presented through a table and graphs extracted from the temperature loggers. After presenting the pilot study results, calculations based on the results are done to confirm the system`s performance and compliance with the South African Bureau of Standards: Part O (2011: 17). The chapter ends with the alterations made to the system to improve its performance.

5.1 PILOT STUDY (Part 1) The pilot study is divided into the following two parts: •

Part 1 of the pilot study will determine the efficiency of the solar air heater before connecting the rock bed heat collector.

•

Part 2 of the pilot study will focus on the performance of the solar heating system when the rock bed heat collector is connected to the solar air heater.

5.1.1 TESTING EQUIPMENT •

BTU (British thermal units) Psychrometer: This testing equipment was used during the experiment to determine the flow speed of the air circulating through the solar air heater and rock bed heat collector. The meter is used to test the airflow in ventilation systems installed in commercial buildings.

Figure 33: Psychrometer (Author, 2021)

41

•

Data Logger: The data logger is used to track the temperature within a room or space for an extended period. The data logger will track the temperature within the solar air heater and rock bed heat collector.

The data from the logger will be extracted and transferred into a graph and table to determine the efficiency of the system.

Figure 34: Data logger (Author, 2021)

The data loggers were calibrated after the study was completed by comparing the room temperature of a standard digital thermometer and a contactless infrared thermometer (on room mode). The data loggers measured 25.7°C, the standard digital thermometer measured 25.7°C, and the infrared thermometer measured 25.9°C. The difference in temperature measured was less than 1% and is deemed to be calibrated correctly compared to alternative devices.

42

5.1.2 EXPERIMENT METHODOLOGY The experiment was conducted for 24 hours from 30 June 2021 at 6:00 am till 1 July 2021 at 6:00 am. The solar air heater was placed at a 26° angle facing North with full solar exposure.

The temperature was measured at the outlet of the solar air heater with a data logger capturing the temperature every hour. A data logger was placed outside the solar air heater to measure the ambient temperature every hour.

The airflow speed was measured with a psychrometer at the outlet of the solar air heater.

The difference between the temperature measured at the outlet and the ambient temperature will be compared to determine the efficiency of the solar air heater. The airflow speed will be utilised to determine the replacement of fresh air within a room or space.

Figure 35: Solar air heater outlet (Author, 2021)

Figure 36: Complete solar air heater

43

5.1.3 RESULTS Figure 37 and Table 9 illustrate the temperatures recorded from the solar air heater and the ambient air.

Table 9: Pilot study part 1 results TIME

TEMPERATURE AT SOLAR AIR HEATER OUTLET

AMBIENT TEMPERATURE

DIFFERENCE BETWEEN AMBIENT AND OUTLET

06:00

8,4

7

1,4

07:00

9,2

8

1,2

08:00

15,4

10

5,4

09:00

26,5

16

10,5

10:00

35,6

18

17,6

11:00

42,1

23

19,9

12:00

37,8

25

12,8

13:00

35,3

27

7,3

14:00

31,7

29

2,7

15:00

31,1

27

4,1

16:00

24,4

25

-1,4

17:00

20,3

23

-2,7

18:00

17,8

21

-2,2

19:00

17

17

0

20:00

16,2

15

1,2

21:00

14,7

14

1,7

22:00

14

13

1

23:00

13,6

12

1,6

00:00

13,8

12

1,8

01:00

13,9

11

1,9

02:00

13,2

12

1,2

03:00

11,5

10

1,5

04:00

11,4

10

1,4

05:00

10,7

10

0,7

06:00

10,2

9

1,2

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Figure 37: Pilot study part 1 results

Solar Air Heater: Pilot Study 45 40 35 30 25 20 15 10 5 0 06:00

08:00

10:00

12:00

14:00

16:00

Outlet of SAH

18:00

20:00

22:00

00:00

02:00

04:00

06:00

Ambient Temperature

After analysing the data, it is clear that the solar air heater produced sufficient heat when solar energy was available from 8:00 till 16:00, as indicated in red in Table 9. After the solar energy was unavailable from 16:00, the heat generated from the solar air heater simultaneously went down. The airspeed was measured at 2m/s at the outlet of the solar air heater.

5.1.4 CONCLUSION From the data gathered during part 1 of the pilot study, the solar air heater can generate sufficient heat from solar energy but will require additional heat storage material to provide heat after the solar energy is not available. The solar air heater only discharged sufficient heat for 8 hours of the day at 2m/s.

5.2 PILOT STUDY (Part 2) Part 2 of the pilot study will focus on the performance of the solar heating system when the rock bed heat collector is connected to the solar air heater. The rock bed heat collector will only be filled with 50% of the required rock to determine the heat storage capacity of the rocks.

45

5.2.1 EXPERIMENT METHOD The rock bed heat collector will be filled with 0.125m³ of rock. The solar air heater will be connected to the rock bed heat collector with 2 x 50mmØ U-Pvc pipes at the inlet and 2 x 50mmØ U-Pvc pipes at the outlet. The solar air heater was placed at a 26° angle facing North with full solar exposure.

The experiment was conducted for 72 hours from 8:00 on 1 July 2021 till 8:00 on 4 July 2021 during the winter season.

Four data loggers are used during the experiment, and the results from each will be compared to determine the system’s efficiency. One data logger is placed at the outlet of the solar air heater, one within the rock bed heat collector, one at the outlet of the rock bed heat collector, and one logger is placed on top of the rock bed heat collector box to track the ambient temperatures during the day and night.

Figure 38: Solar heating system front view

Figure 39: Solar heating system side view

(Author, 2021)

(Author, 2021)

46

5.2.2 RESULTS Figure 40: Pilot study part 2 experiment results – Day 1

Figure 41: Pilot study part 2 experiment results – Day 2

Heat storage Day 2 80 70 60 50 40 30 20 10 0 06:00:00 08:30:00 11:00:00 13:30:00 16:00:00 18:30:00 21:00:00 23:30:00 02:00:00 04:30:00 Amient Temperature Ambient Temperature

Top of SAH

47

Rockbed Outlet

Figure 42: Pilot study part 2 experiment results – Day 3

Heat storage Day 3 80 70 60 50 40 30 20 10 0 06:00:00 08:30:00 11:00:00 13:30:00 16:00:00 18:30:00 21:00:00 23:30:00 02:00:00 04:30:00

Ambient Temperature Amient Temperature

Top of SAH

Rockbed Outlet

The results from the 3-day experiment indicate that the solar air heater generated a maximum of 75°C during the day. The temperature within the rock bed reached a maximum of 40°C during the same time the solar air heater reached its peak. The solar air heater is charged from 8:00 till 16:00 each day. The results indicate that the heat storage from the rock bed heat collector proved to store and discharge sufficient heat, which is 5°C or more, compared to the ambient temperature, from 10:00 till 23:00. From 23:00 onward, the rocks discharged heat which is at 4°C and below, compared to the ambient temperature The results indicate that the system can generate and store heat sufficiently by making use of solar energy. The system will be tested further during the complete experiment.

5.2.3 CALCULATIONS The results from Part 1 and 2 of the pilot study will be used to calculate the efficiency of the solar air heater.

By calculating the rate at which the solar air heater can replace the air volume within a room or space, the size and efficiency of the solar air heater can be determined. The following formula is used to calculate the rate of airflow at litre per second.

48

Total area: Area = π x r² Area = 3.14 x 55mm² Area = 3.14 x 3025mm² Area = 9498.5mm² Area = 9498.5mm² / 1000 (Converted to metric scale) Volume of heated air supply by the solar air heater: = Area x Flow rate = Litre/second = 0.9498 x 2m/s = 1,8996 L/s Replacement of air: 1000L of air is equal to 1m³ at 23°C 1000L / 1,8996/s = 526,42 seconds to fill air volume 526.42/ 60 seconds per minute = 8.7 minutes It will take 8.7 minutes/ 526.42 seconds to fill up or replace the air of 1m³.

According to the South African Bureau of Standards: Part O (2011: 17), it is illustrated in table 2 that the number of air changes per hour for a living room situated in a dwelling unit should be a minimum of 2. The calculation results indicate that the system will replace the air within a 1m³ air volume 6,8 times within one hour. The air changes will depend on the air volume of the room/ space and will need to be calculated individually when implementing the system on a housing unit.

5.2.4 ALTERATIONS AND CHANGES After conducting the pilot study, some areas were identified to ensure the system’s heat storage at an optimum rate. Below is a list of items to improve: •

Pipe length between the solar air heater and the rock bed heat collector to be shortened to reduce heat loss.

•

Insulate all exposed pipes.

•

Ensure all joints of the solar air heater and rock bed heat collector are sealed.

49

•

The rock bed heat collector is filled to full capacity to store heat for more extended periods.

Figures 43 and 44 illustrate the alterations made to the system. The system was used during the entire experiment in Chapter 6.

Figure 43: Revised solar heating system (Author, 2021)

Figure 44: Insulation over exposed pipes (Author, 2021)

5.2.5 CONCLUSION: From the results in Part 2 of the pilot study, it is clear that the system can store heat for at least 7 hours after no solar energy is available by adding the rock to the solar air heater.

Comparing the results from the calculations with the South African Bureau of Standards, the system achieves the minimum requirement of 2 air changes per hour. The results from the pilot study and the calculations indicate that the system can be tested further through the full experiment in Chapter 6. The alterations to the system were done before conducting the full experiment during the next chapter.

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DATA PROCUREMENT • •

Chapter 6: Introduction Full experiment Part 1: Ventilated heating system - Introduction - Methodology - Results - Conclusion

•

Full experiment Part 2: Enclosed heating system - Introduction - Methodology - Results - Conclusion

•

Full experiment Part 3: Ventilated cooling system - Introduction - Methodology - Results - Conclusion

•

Full experiment Part 4: Enclosed cooling system - Introduction - Methodology - Results - Conclusion

•

Comparison ASHREA thermal comfort and results from experiment

•

Conclusion from comparison

•

Application of solar heating/ cooling system

•

Cost analysis

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6 INTRODUCTION The information and results from Chapter 5 will the used in Chapter 6 to conduct the full experiment. The pilot study identified the shortcomings and alterations required before conducting the full experiment. In Chapter 6, the complete experiment will be conducted in the following four parts: •

Part 1 will focus on a ventilated heating system by allowing ambient air to flow through the system 24 hours per day during the winter season.

•

Part 2 will focus on an enclosed heating system. The air will be circulated through the solar heating system without any fresh air ventilation.

•

Part 3 will focus on a semi-ventilated cooling system, which will be tested during the summer season by enclosing one of the inlet pipes and leaving one open for 24 hours per day to allow ambient air to enter the system.

•

Part 4 will focus on an enclosed cooling system by connecting the inlet of the solar air heater and outlet of the rock bed during the day and opening the inlet of the solar air heater during the evening to absorb the ambient air in the rock bed.

The chapter will compare the results from the full study with ASHRAE 55 to determine the system`s efficiency. It illustrates the application of the system to newly built houses and retrofitting the system on an existing house. The chapter ends with the cost analysis of the system constructed from the material obtained in Chapter 5.

6.1 FULL EXPERIMENT - PART 1: VENTILATED HEATING SYSTEM 6.1.1 INTRODUCTION During Part 1 of the experiment, the ventilated system, the inlet of the solar air heater, and the outlet of the rock bed heat collector will be open. During Part 2, the enclosed system, the inlet of the solar air heater, and the outlet of the rock bed heat collector will be connected to allow the heated air to circulate through the system.

The potential to use the heating system during the summer for cooling will also be tested.

The rocks will be cooled by circulating the ambient air through the system during the evening and circulating the warm air during the day. The experiment will be discussed further in sections 6.3 and 6.4 below.

52

Figure 45 illustrates a typical diagram of a ventilated heating system. Ambient air circulates through the solar air heater and is heated by solar energy. The heated air from the solar air heater circulates through to the rock bed heat collector to store heat within the rocks and supply warm air at the outlet of the rock bed.

Figure 45: Diagram of ventilated heating system

53

6.1.2 METHODOLOGY The rock bed heat collector reaches full capacity with 0.25m³ of rock. The outlet solar air heater will be connected to the rock bed heat collector’s inlet with 2 x 50mmØ U-PVC pipes. The inlet of the solar air heater, 2 x 50mmØ U-PVC pipes, will be open to allow the flow of the fresh ambient air into the solar air heater. The solar air heater is placed at a 26° angle facing North with full solar exposure.

Figure 46: Pipes of ventilated heating system (Author, 2021)

The circulation fan will be powered by a solar panel during the day, 8:00 am till 16:00 pm and after 16:00 pm till 8:00 am; the circulation fan will be powered by a 5000mah power bank. The experiment was conducted for a duration of 168 hours/ 7 days from 8:00 am on 1 July 2021 till 8:00 am on 8 July 2021 during the winter season.

Four data loggers are used during the experiment, and the results from each will be compared to determine the system’s efficiency. One data logger is placed at the outlet of the solar air heater, one within the rock bed heat collector, one at the outlet of the rock bed heat collector, and one logger is placed on top of the rock bed heat collector box to track the ambient temperatures during the day and night.

6.1.3 RESULTS Figures 47 to 53 illustrate the results from the ventilated heating system. Each figure illustrates the results for one day from 6:00 am to next 6:00 am (24 hours). In Figure 54, the combined results are illustrated for the 7-day experiment.

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Figure 47: Ventilated heating system experiment results – Day 1

Figure 48: Ventilated heating system experiment results – Day 2

Ventilated heat storage - Day 2 50 40 30 20 10 0 06:00:00 08:30:00 11:00:00 13:30:00 16:00:00 18:30:00 21:00:00 23:30:00 02:00:00 04:30:00 Amient AmbientTemperature Temperature

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Rockbed Outlet

Figure 49: Ventilated heating system experiment results – Day 3

Ventilated heat storage - Day 3 50 40 30 20 10 0 06:00:00 08:30:00 11:00:00 13:30:00 16:00:00 18:30:00 21:00:00 23:30:00 02:00:00 04:30:00

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Figure 50: Ventilated heating system experiment results – Day 4

Ventilated heat storage - Day 4 50 40 30 20 10 0 06:00:00 08:30:00 11:00:00 13:30:00 16:00:00 18:30:00 21:00:00 23:30:00 02:00:00 04:30:00

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Figure 51: Ventilated heating system experiment results – Day 5

Ventilated heat storage - Day 5 50 40 30 20 10 0 06:00:00 08:30:00 11:00:00 13:30:00 16:00:00 18:30:00 21:00:00 23:30:00 02:00:00 04:30:00

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Rockbed Outlet

Figure 52: Ventilated heating system experiment results – Day 6

Ventilated heat storage - Day 6 50 40 30 20 10 0 06:00:00 08:30:00 11:00:00 13:30:00 16:00:00 18:30:00 21:00:00 23:30:00 02:00:00 04:30:00

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Figure 53: Ventilated heating system experiment results – Day 7

Ventilated heat storage - Day 7 50 40 30 20 10 0 06:00:00 08:30:00 11:00:00 13:30:00 16:00:00 18:30:00 21:00:00 23:30:00 02:00:00 04:30:00 Amient Temperature Ambient Temperature

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Rockbed Outlet

Figure 54: Ventilated heating system experiment results – Combined 7 Days

The results from the 7-day experiment indicate that the solar air heater generated a maximum of 43°C during the day. The temperature within the rock bed reached a maximum of 40°C during the same time the solar air heater reached its peak. The solar air heater is charged from 8:00 till 16:00 each day. The results indicate that the heat storage from the rock bed heat collector discharged sufficient heat, which is 5°C or more, compared to the ambient temperature, from 10:00 till 19:00. From 19:00 onward, the rocks discharged heat which is at 4°C and below, compared to the ambient temperature The ventilated heating system lost most of the heat stored in the rock bed heat collector by 19:00 pm, 3 hours after the solar energy was unavailable. The cooler ambient air flowing through the system after 16:00 pm cools down the rocks.

At 13:00 pm when the ambient temperature reached its peak at 19°C, the rock bed heat collector’s temperature was at 36°C, 48% higher than the ambient air. The air temperature from the solar air heater was at 41°C, 54% higher than the ambient temperature.

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At 5:30 am, when the ambient air is at the lowest temperature of 12°C, the heat from the rock bed heat collector was also at 12°C, and all the heat from the rock heat collector was lost.

Figure 54 illustrates that the minimum temperature of the rock bed heat collector is lower than the minimum ambient temperature. As illustrated in Figures 55 and 56, the core temperature of the rocks remains cold, and only the surface absorbs the heat from the solar air heater. As soon as the surface temperature is being lost at 19:00 pm, the core temperature cools down air flowing through the rock bed heat collector below the minimum temperature of the ambient temperature, it is illustrated in Figures 55 and 56.

Figures 55 and 56 illustrate the effect, also known as the flywheel effect. The flywheel effect is when a thermal mass, such as rock, absorb the heat when the surrounding air temperature is higher than the thermal mass during the day and transfer the heat back to its surrounding air when it is cooler than the thermal mass. During the flywheel effect, an equilibrium is never reached as the core of the rocks is colder than the ambient air.

Therefore, the air from the rock bed is cooler than the ambient air as soon as the surface of the rocks loses all the heat stored.

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Figure 55: Rock diagram of the ventilated system during daytime (Author, 2021)

Figure 56: Rock diagram of the ventilated system during the night-time (Author, 2021)

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6.1.4 CONCLUSION The ventilated experiment concludes that the system requires human intervention after the solar energy is not available from 16:00 pm. The system needs to be closed from 16:00 pm till 8:00 to limit the heat loss from the rock bed heat collector. Smaller rocks or gravel can be used during the same experiment to heat the core of the rock faster, which will also increase the heat loss rate of the rocks. The study will test the heat storage capacity of the rocks utilised in part 1 of the full experiment, further in part 2 by testing the possibility of seasonal charging to heat the core of the rocks and not only the surface.

6.2 FULL EXPERIMENT - PART 2: ENCLOSED HEATING SYSTEM 6.2.1 INTRODUCTION The enclosed system will focus on the heating system’s performance by circulating the air through the solar heating system and rock bed heat collector to limit the amount of heat loss.

The system will not be able to provide fresh air into the interior space/ room.

Figure 57 illustrates the typical diagram of the enclosed heating system. The air within the solar heating system continues to recirculate through the system, which will heat the already heated air through the solar energy from the solar air heater.

Figure 57: Diagram of enclosed heating system

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6.2.2 METHODOLOGY The rock bed heat collector is filled to full capacity with 0.25m³ of rock. The outlet solar air heater will be connected to the rock bed heat collector’s inlet with 2 x 50mmØ UPVC pipes. The inlet of the solar air heater, 2 x 50mmØ UPVC pipes, will be connected to the outlet of the rock bed heat collector to recirculate the air. The solar air heater is placed at a 26° angle facing north with full solar exposure.

Figure 58: Pipes of enclosed heating system (Author, 2021)

The circulation fan will be powered by a solar panel during the day, 8:00 am till 16:00 pm and after 16:00 pm till 8:00 am; the circulation fan will be powered by a 5000mah power bank. The experiment was conducted for a duration of 168 hours/ 7 days from 8:00 am on 5 July 2021 till 8:00 am on 12 July 2021 during the winter season.

Four data loggers are used during the experiment. The results from each will be compared to determine the system’s efficiency. One data logger is placed at the outlet of the solar air heater, one within the rock bed heat collector, one at the outlet of the rock bed heat collector. One logger is placed on top of the rock bed heat collector box to track the ambient temperatures during the day and night.

6.2.3 RESULTS Figures 59 to 65 illustrate the results from the enclosed heating system. Each figure illustrates the results for seven day from 6:00 am to 6:00 am (24 hours). Figure 66 illustrates the combined results for the 7-day experiment.

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Figure 59: Enclosed heating system experiment results – Day 1

Figure 60: Enclosed heating system experiment results – Day 2

Heat storage Day 2 80 70 60 50 40 30 20 10 0 06:00:00

08:30:00

11:00:00

13:30:00

16:00:00

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23:30:00

02:00:00

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Figure 61: Enclosed heating system experiment results – Day 3

Heat storage Day 3 80 70 60 50 40 30 20 10 0 06:00:00 08:30:00 11:00:00 13:30:00 16:00:00 18:30:00 21:00:00 23:30:00 02:00:00 04:30:00

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Figure 62: Enclosed heating system experiment results – Day 4

Heat storage Day 4 80 70 60 50 40 30 20 10 0 06:00:00 08:30:00 11:00:00 13:30:00 16:00:00 18:30:00 21:00:00 23:30:00 02:00:00 04:30:00 Amient Temperature Ambient Temperature

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Rockbed Outlet

Figure 63: Enclosed heating system experiment results – Day 5

Heat storage Day 5 80 70 60 50 40 30 20 10 0 06:00:00

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13:30:00

16:00:00

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02:00:00

04:30:00

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Figure 64: Enclosed heating system experiment results – Day 6

Heat storage Day 6 80 70 60 50 40 30 20 10 0 06:00:00 08:30:00 11:00:00 13:30:00 16:00:00 18:30:00 21:00:00 23:30:00 02:00:00 04:30:00

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Rockbed Outlet

Figure 65: Enclosed heating system experiment results – Day 7

Heat storage Day 7 80 70 60 50 40 30 20 10 0 06:00:00 08:30:00 11:00:00 13:30:00 16:00:00 18:30:00 21:00:00 23:30:00 02:00:00 04:30:00 Amient Temperature Ambient Temperature

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Figure 66: Enclosed heating system experiment results – Combined 7 Days

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The results from the 7-day experiment indicate that the solar air heater generated a maximum of 79°C during the day. The temperature within the rock bed reached a maximum of 49°C during the same time the solar air heater reached its peak. The solar air heater is charged from 8:00 am till 16:00 pm each day. The results indicate that the heat storage from the rock bed heat collector proved to store sufficient heat, which is 5°C or more, compared to the ambient temperature, from 6:00 am to 6:00 am (24 hours). From the 7 days combined figure, the temperature stored within the rock bed heat collector increased each day. All the heat is not lost by 8:00 am when the solar energy becomes available for the next day.

At 13:00 pm when the ambient temperature reached its peak at 22,2°C, the rock bed heat collector’s temperature was 45,4°C, 52% higher than the ambient air and the air temperature from the solar air heater was 72°C, 70% higher than the ambient temperature.

At 5:30 am, when the ambient air was at the lowest temperature of 11,2°C, the heat from the rock bed heat collector was still at 19,4°C, 43% higher than the ambient temperature.

Figures 66 and 67 illustrate the minimum temperature the rocks increase each day. Due to the flywheel effect, the rock’s core temperature increases and stores additional heat in incremental portions. The results illustrated in Figure 66 indicate the possibility of seasonal charging, which can be explored in more detail through further study. It is anticipated that when the core of the rocks is at its optimum temperature, the rock will be able to discharge sufficient heat to the air passing through the system. This can be confirmed by further studies by testing the system for more extended periods.

6.2.4 CONCLUSION The enclosed system proved to store sufficient heat during the day to discharge warm air into a room/ space during the evening. The enclosed system can be tested further to establish the results when tested for extended periods. The results from the enclosed system indicate that the solar heating system can be charged seasonally during the summer to improve the heat supply during the winter season. By charging the solar heating system seasonally, the core of the rock can be heated by the time the winter season starts, and the heat required to heat the rock bed heat collector will be less.

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Figure 67: Rock diagram of enclosed heating system (Author, 2021)

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6.3 FULL EXPERIMENT - PART 3: VENTILATED COOLING SYSTEM 6.3.1 INTRODUCTION In parts 3 and 4 of the experiment, the possibility of using the solar heating system as a cooling device was tested. Part 3 focussed on a ventilated cooling system, which uses ambient air to cool the rocks of the rock bed. The system provides fresh air 24 hours per day.

Figure 68 illustrates the ventilated cooling system. The system runs for 24 hours per day without any human intervention. The system allows for 50% fresh air, and 50% recirculated air; this will be discussed further under the methodology. Cool ambient air /cools the rocks during the evening. During the day, the warm air flows over the rocks, and the heat is exchanged between the air and rocks, which allows the warm air to cool down. Cool air is supplied through the outlet of the rock bed.

Figure 68: Diagram of ventilated cooling system

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6.3.2 METHODOLOGY The rock bed heat collector is filled to full capacity with 0.25m³ of rock. The outlet solar air heater will be connected to the rock bed heat collector’s inlet with 2 x 50mmØ U-PVC pipes. The system will make use of 50% fresh ambient air, and 50% recirculated air. One outlet pipe of the rock bed and one inlet pipe (50mmØ U-PVC pipes) will be connected, while the remaining inlet and outlet pipes (50mmØ U-PVC pipes) will remain open 24 hours per day. The glazed panel of the solar air heater is covered with a 500mm x 1000mm x 20mm thick chipboard with 50mm thick polystyrene fixed to the timber board, as illustrated in Figure 69.

Figure 69: Solar heating system glazed panel enclosed (Author, 2021)

The circulation fan will be powered by a solar panel during the day, 8:00 am till 16:00 pm and after 16:00 pm till 8:00 am; a 5000mah power bank will power the circulation fan. The experiment was conducted for 72 hours/ 3 days from 6:00 am on 10 October 2021 till 6:00 am on 13 October 2021 during the summer season.

Four data loggers are used during the experiment. The results from each will be compared to determine the system’s efficiency. One data logger is placed at the outlet of the solar air heater, one within the rock bed heat collector, one at the outlet of the rock bed heat collector. One logger is placed on top of the rock bed heat collector box to track the ambient temperatures during the day and night.

6.3.3 RESULTS Figures 70 to 72 illustrate the results from the ventilated cooling system. Each figure illustrates the results for one day from 6:00 am to 6:00 am (24 hours). Figure 73 illustrates the combined results for the 3-day experiment.

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Figure 70: Ventilated cooling experiment results – Day 1

Figure 71: Ventilated cooling experiment results – Day 2

Ventilated Cooling Day 2 40 35 30 25 20 15 10 5 0 06:00:00 08:30:00 11:00:00 13:30:00 16:00:00 18:30:00 21:00:00 23:30:00 02:00:00 04:30:00

Ambient Temperature Amient Temperature

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Rockbed Outlet

Figure 72: Ventilated cooling experiment results – Day 3

Ventilated Cooling Day 3 40 35 30 25 20 15 10 5 0 06:00:00 08:30:00 11:00:00 13:30:00 16:00:00 18:30:00 21:00:00 23:30:00 02:00:00 04:30:00 Amient Temperature Ambient Temperature

Rock bed Storage

Rockbed Outlet

Figure 73: Combined Results: Ventilated cooling experiment – 3 Days

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Figures 70 to 73 illustrate that the rock bed can provide cool air, 5°C lower than the ambient temperature, from 10:00 am till 18:00 pm. From 18:00 pm, the ambient temperature drops gradually till the next day, 7:00 am.

The rock remains warmer than the ambient air during the evening from 18:00 pm till 7:00 am due to the flywheel effect explained in paragraph 6.1.3. The core of the rock is warmer than the ambient air and cools down much slower than the ambient air due to the rock’s thermal mass.

During the peak temperature of the ambient air at 13:00 pm, the air from the rock bed showed a temperature difference of 29% on day one, 29% on day two, and 28% on day three. The system cooled the ambient air on average 28,5% over the three days the system was tested.

6.3.4 CONCLUSION Using the solar heating system for cooling during the summer has shown positive results to cool the ambient air during the daytime by using the cooled ambient air during the night. The system also improves the indoor air quality by ventilating fresh ambient air through the system for 24 hours per day.

6.4 FULL EXPERIMENT - PART 4: ENCLOSED COOLING SYSTEM 6.4.1 INTRODUCTION Part 4 of the experiment will focus on an enclosed cooling system; this system will use the cool ambient air during the evening and circulate the internal air during the day.

Figures 74 and 75 illustrate the enclosed cooling system for the day and night-time. As illustrated in Figure 74, the system will be enclosed to recirculate the cool air through the system. In Figure 75, it is illustrated that the system will be opened during the night-time to cool the rocks of the rock bed with means of cool ambient air.

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Figure 74: Enclosed cooling system diagram: Daytime

Figure 75: Enclosed cooling system diagram: Night-time

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6.4.2 METHODOLOGY The rock bed heat collector is filled to full capacity with 0.25m³ of rock. The outlet solar air heater will be connected to the rock bed heat collector’s inlet with 2 x 50mmØ U-PVC pipes.

Figure 74 illustrates the inlet of the solar air heater and the outlet of the rock bed. As illustrated in Figure 74, the inlet of the covered solar air heater and outlet of rock bed, 2 x 50mmØ U-PVC at each inlet and outlet, will be open during the evening from 18:00 pm for circulation of cool ambient air and closed at 6:00 am. The glazed panel of the solar air heater is covered with a 500mm x 1000mm x 20mm thick chipboard with 50mm thick polystyrene fixed to the timber board.

The circulation fan will be powered by a solar panel during the day, 8:00 am till 16:00 pm, and after 16:00 pm till 8:00 am, the circulation fan will be powered by a 5000mah power bank.

The experiment was conducted for a duration of 72 hours/ 3 days from 6:00 am on 21 October 2021 till 6:00 am on 24 October 2021 during the summer season.

Four data loggers are used during the experiment. The results from each will be compared to determine the system’s efficiency. One data logger is placed at the outlet of the solar air heater, one within the rock bed heat collector, one at the outlet of the rock bed heat collector. One logger is placed on top of the rock bed heat collector box to track the ambient temperatures during the day and night.

6.4.3 RESULTS Figures 76 to 78 illustrate the results from the enclosed cooling system. Each figure illustrates the results for one day from 6:00 am to 6:00 am (24 hours). Figure 79 illustrates the combined results for the 3-day experiment.

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Figure 76: Enclosed cooling experiment results – Day 1

Figure 77: Enclosed cooling experiment results – Day 2

Enclosed Cooling Day 2 40 35 30 25 20 15 10 5 0 06:00:00 08:30:00 11:00:00 13:30:00 16:00:00 18:30:00 21:00:00 23:30:00 02:00:00 04:30:00 Amient Temperature Ambient Temperature

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Rockbed Outlet

Figure 78: Enclosed cooling experiment results – Day 3

Enclosed Cooling Day 3 50 45 40 35 30 25 20 15 10 5 0 06:00:00 08:30:00 11:00:00 13:30:00 16:00:00 18:30:00 21:00:00 23:30:00 02:00:00 04:30:00

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Rock bed Storage

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Figure 79: Combined Results: Enclosed cooling experiment – 3 Days

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Figures 76 to 79 illustrate that the rock bed can provide cooled air, which is 5°C lower than the ambient temperature, from 10:00 am till 16:00 pm. Between 16:00 pm and 18:00 pm, the difference between the ambient air temperature and the rock bed is less than 2°C. From 18:00 pm, the ambient temperature drops gradually till the next day, 7:00 am. The discharging air should be ventilated to the ambient air and not back into the space/ room during the evening.

The rock remains warmer than the ambient air during the evening from 18:00 pm till 7:00 am due to the flywheel effect explained in paragraph 6.1.3. The core of the rock is warmer than the ambient air and cools down much slower than the ambient air due to the rock’s thermal mass.

During the peak temperature of the ambient air at 13:00 pm, the air from the rock bed showed a temperature difference of 20% on day one, 19% on day two, and 17% on day three. The system cooled the ambient air on average 18,6% over the three days the system was tested.

6.4.4 CONCLUSION When comparing the ventilated cooling experiment`s results with the enclosed cooling system, the ventilated system indicated an improvement of 10% on average. Due to the constant flow of air through the system, any radiant heat penetrating through the thermal insulation can be extracted. The enclosed system was not as efficient as the ventilated system. This can be due to any heat transferring through the thermal insulation cannot being extracted during the daytime as the system is enclosed. Furthermore, the enclosed system did not provide fresh air during the day.

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6.5 COMPARISON ASHREA THERMAL COMFORT AND RESULTS FROM THE CURRENT EXPERIMENT This section will compare the results from Chapter 6 with the ASHRAE 55 standards to indicate the system’s effectiveness.

6.5.1 Ventilated heating system (Winter range 20°C to 23°C) Chapter 6.1 indicates that the ambient temperature reached an average of 21°C between 13:00 pm and 16:00 pm. The solar heating system discharged heat between 20°C and 23°C from 18:00 pm till 20:00 pm; after that, the temperature dropped below the minimum of 20°C. 6.5.2 Enclosed heating system (Winter range 20°C to 23°C) The results in Section 6.2 indicate that the ambient temperature reached an average of 21°C between 13:00 pm and 16:00 pm. The solar heating system discharged heat between 20°C and 23°C from 18:00 pm till 1:00 am the following day; the temperature dropped below the minimum of 20°C. 6.5.3 Ventilated cooling (Summer range 23°C to 26.6°C) The results from section 6.3 indicate that the ambient temperature ranged between 23°C to 26.6°C from 10:00 am till 12:00 pm and 17:00 pm till 19:00 pm. The rock bed of the ventilated system was able to provide an air temperature of between 23°C and 26.6°C from 12:00 pm till 00:00 am; after that, the temperature dropped below 23°C. 6.5.4 Enclosed cooling (Summer range 23°C to 26.6°C) The results from section 6.3 indicate that the ambient temperature ranged between 23°C to 26.6°C from 10:00 am till 12:00 pm and 17:00 pm till 19:00 pm. The rock bed of the enclosed system was able to provide an air temperature of between 23°C and 26.6°C from 20:00 pm and 1:00 am; after that, the temperature dropped below 23°C. 6.5.5 ASHRAE STANDARD According to a National Institute for Occupational Safety and Health published in the United States of America, thermal comfort is related to metabolic heat production, heat transfer to the environment, physiological adjustments, and body temperature. Heat transfer from the body to the environment is influenced by temperature, humidity, air movement, personal activities, and clothing. According to the ASHRAE Standard 55-2013, the thermal

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environmental conditions for human occupancy specify the combinations of indoor environmental and personal factors that produce acceptable thermal conditions for most occupants within a space (ASHRAE, 2013). Furthermore, assuming slow air movement (less than 12m per minute) and 50% indoor relative humidity, the operative temperatures recommended by ASHRAE range from 20°C to 23°C in the winter, and from 23°C to 26.6°C in the summer. The temperature range is related to the change in clothing depending on the season.

6.5.6 CONCLUSION FROM COMPARISON After comparing the results with the ASHRAE standards, the enclosed heating system proved to be the most efficient as the system was able to discharge heat within the thermal comfort range for 5 hours on average. The ventilated system was only able to discharge heat within the thermal comfort range for 2 hours.

After comparing the results from the cooling system, the ventilated system proved to be the most efficient as the system proved to provide cooled air between the range of 23°C and 26.6°C for 12 hours on average compared to the 5 hours of cooled air provided from the enclosed system.

6.6 APPLICATION OF SOLAR HEATING/ COOLING SYSTEM The solar heating system is proposed to be installed on housing units either as a retrofit or as part of a newly built housing unit. For this section, a 24.3m³ (3000mm x 3000mm x 2400m) housing unit will be used as an example.

Calculation of rock bed required: 24.3m³ x 0,25m³ (Rock) = 6.075m³ Calculation of solar air heater: 0,5m² x 24.3m³ = 12,15m² The solar air heater can be constructed in separate panels to make up the required size of the panel or constructed in one large panel.

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6.6.1 New built solar heating system application To install the solar heating system on a newly built housing unit, it is proposed that the rock bed be placed below the surface bed of the housing unit with the solar air heater fixed to the northern wall in a vertical position. The solar air heater should swivel to allow for seasonal change as and when the system is required.

The rock bed below the floor slab will be heated by the hot air supplied by the solar air heater during the winter season; the heat from the rocks will also radiate through the floor slab into the space/room. Refer to Figure 80 for an illustration of the proposed application of the solar heating system.

It is proposed that the solar air heater be placed on the side of the housing at a vertical position with hinges to lift the bottom of the solar air heater during the winter to generate heat and retract during the summer for the system to be used for cooling.

Figure 80: Solar heating system application on newly built housing unit (Author, 2021)

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6.6.2 Retrofit solar heating system application To retrofit the solar heating system on an existing housing unit, it is proposed that the rock bed be placed in a trench next to the housing unit. As illustrated in Figure 81, the trench is proposed to be covered with a timber sheet with a concrete slab cast in-situ on top of the rock bed. A concrete slab is cast in situ at the bottom of the rock bed with a wall on the side to limit heat loss.

As illustrated in Figure 81, it is also proposed that the solar air heater is placed on the northern with hinges to tilt for seasonal change. The disadvantage of this system is that the heat will not transfer directly into the space through the floor. Refer to Figure 81 for the illustration of the retrofit application.

Figure 81: Solar heating system application on an existing housing unit (Author, 2021)

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6.7 COST ANALYSIS In Table 10, the total cost of the solar heating system was utilised in this experiment to determine the project’s cost-effectiveness.

Table 10: Cost analysis Material Solar air heater: Chromadek sheeting 152mm x 38 Timber frame 4mm thick clear glass News Paper Bubble wrap Backing board 5 Watt solar panel 1.5 Watt circulation fan Fixing screws (50) Wood glue (500ml) Sub-total for solar air heater Rock bed heat collector: 100-150mm Rock Shutter board 50mm Thick polystyrene U-Pvc pipes Fixing screws (50) Wood glue (500ml) Sub-total for rock bed Total cost

Cost R70,00 No cost R30,00 No cost No cost No cost R90,00 R87,00 R37,00 R45,00 R359,00 No cost No cost No cost R68,00 R37,00 R45,00 R150,00 R509,00

The total cost for the solar air heater is R359,00, and the cost for the rock bed heat collector is R150,00. The total cost for the solar heating system is R509,00. The cost of the system is competitive with the commercial products available on the market.

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CONCLUSION • Chapter 7: Introduction • Recommendation • Opportunities for communities

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INTRODUCTION Chapter 7 discuss the recommendations of the solar heating system after completing the full experiment in Chapter 6. Furthermore, the chapter focus on the potential for further study. The chapter ends with the potential impact the system can have on low-income communities when the solar heating system is implemented successfully

7.1 RECOMMENDATIONS 7.1.1 Heating system recommendation Taking into consideration the results from Chapter 6, the following items are recommended for the heating system: It is recommended that –

•

The enclosed system is used for space heating during the winter season as it proved to discharge the most sufficient heat.

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The enclosed system be tested further to establish the possibility of seasonal charging. The results of section 6.2 showed a gradual increase in the minimum temperature from the rocks each day.

•

Alternative rocks sizes are tested to improve the efficiency of the heating system.

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The heating system be tested on a large-scale experiment to determine its effectiveness on a housing unit.

7.1.2 Cooling system recommendations: The following items are recommended for the cooling system. It is recommended that-

• The ventilated cooling system be used for the implementation during the summer season as it proved to be the most efficient during this experiment.

• Alternative rocks sizes be tested to improve the cooling system’s efficiency as smaller rocks can charge and discharge much quicker.

• The ventilated cooling system be tested on a large-scale experiment to determine its effectiveness on a housing unit.

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7.2 OPPORTUNITIES FOR COMMUNITIES 7.2.1 Local labour opportunities Implementing the system on low-cost housing within communities can create new opportunities for local labour. Opportunities for the following trades and categories can arise by implementing this system: •

Electrician: Installation of the solar panel, circulation fan, and power port.

•

Carpenter: Construction of the rock bed box and main frame of the solar air heater.

•

Plumber: Connection of circulation pipes on the system.

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Contractors: Install the systems on housing units either as a retrofit or a new build.

•

Maintenance: Service provider to do routine checks on the systems installed in a community every month and fix the systems as required.

7.2.2 Local economy upliftment To construct the solar heating/ cooling system, the material required will need to be sourced on a large scale. Similar to recycling plastic, glass, and paper within low-income communities, a new system can be developed whereby waste pickers source and locate second-hand materials required to construct the system. The materials can be sourced from dumpsites, redundant construction projects, existing buildings’ demolition, or off-cut material from existing construction projects.

The products can be sold to the contractors constructing the systems or the maintenance service provider requiring materials to fix the existing systems.

The implementation of the solar heating/cooling system will not only impact the thermal comfort and living conditions of low-income communities. It can also create local opportunities for labour and entrepreneurial innovation. This will be able to uplift the economy of low-income communities and help the people to take matters into their own hands to improve their overall living conditions.

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LIST OF FIGURES (All figures by Author unless referenced otherwise) Figure 1: Front page: Nongoma informal settlement: KZN ..................................................... 2 Figure 2: Typical illustration of proposed heating system experimental set-up during the winter season ......................................................................................................................... 3 Figure 3: Typical illustration of proposed cooling system experimental set-up during the winter season. ........................................................................................................................ 4 Figure 4: Map of South Africa and Gauteng ........................................................................... 7 Figure 5: Concept diagram drawing of solar air heater and rock bed heat collector. ............ 23 Figure 6: Concept diagram drawing of a solar air heater ...................................................... 24 Figure 7: Concept drawing of obstruction in solar air heater................................................. 25 Figure 8: Concept drawing of rock bed ................................................................................. 26 Figure 9: Concept model of complete solar air heating system to be tested during the experiment ............................................................................................................................ 27 Figure 10: Concept model: Exploded view of rock bed heat collector box ............................ 28 Figure 11: Concept model: Exploded view of a solar air heater............................................ 29 Figure 12: Chromadek roof sheet & Figure 13: Obstacles in solar air .................................. 30 Figure 14: SA Pine timber frame for solar & Figure 15: SA Pine timber planks .................... 31 Figure 16: Glass panel.......................................................................................................... 31 Figure 17: Newspaper insulation & Figure 18: Bubble wrap insulation ................................. 32 Figure 19: Timber courier box............................................................................................... 33 Figure 20: Circulation fan...................................................................................................... 33 Figure 21: Solar panel .......................................................................................................... 33 Figure 22: Complete solar air heater .................................................................................... 34 Figure 23: Off-cut shutter board & Figure 24: Construction of heat collector box ................. 35 Figure 25: Insulation in waste bin & Figure 26: Bulk insulation obtained .............................. 36 Figure 27: Insulation fixed to timber box ............................................................................... 36 Figure 28: Rocks from a construction site............................................................................. 37 Figure 29: Size of rocks obtained ......................................................................................... 37 Figure 30: Placement of U-PVC pipes .................................................................................. 38 Figure 31: Inlet pipe to rock bed heat collector ..................................................................... 38 Figure 32: Outlet from rock bed heat collector ...................................................................... 38 Figure 33: Psychrometer ...................................................................................................... 41 Figure 34: Data logger .......................................................................................................... 42 Figure 35: Solar air heater outlet .......................................................................................... 43 Figure 36: Complete solar air heater .................................................................................... 43 Figure 37: Pilot study part 1 results ...................................................................................... 45 Figure 38: Solar heating system front view & Figure 39: Solar heating system side view .... 46 Figure 40: Pilot study part 2 experiment results – Day 1 ...................................................... 47 Figure 41: Pilot study part 2 experiment results – Day 2 ...................................................... 47 Figure 42: Pilot study part 2 experiment results – Day 3 ...................................................... 48 Figure 43: Revised solar heating system & Figure 44: Insulation over exposed pipes ......... 50 Figure 45: Diagram of ventilated heating system.................................................................. 53 Figure 46: Pipes of ventilated heating system ...................................................................... 54 Figure 47: Ventilated heating system experiment results – Day 1 ........................................ 55 Figure 48: Ventilated heating system experiment results – Day 2 ........................................ 55 Figure 49: Ventilated heating system experiment results – Day 3 ........................................ 56

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Figure 50: Ventilated heating system experiment results – Day 4 ........................................ 56 Figure 51: Ventilated heating system experiment results – Day 5 ........................................ 56 Figure 52: Ventilated heating system experiment results – Day 6 ........................................ 57 Figure 53: Ventilated heating system experiment results – Day 7 ........................................ 57 Figure 54: Ventilated heating system experiment results – Combined 7 Days ..................... 58 Figure 55: Rock diagram of the ventilated system during daytime ....................................... 60 Figure 56: Rock diagram of the ventilated system during the night-time .............................. 60 Figure 57: Diagram of enclosed heating system................................................................... 61 Figure 58: Pipes of enclosed heating system ....................................................................... 62 Figure 59: Enclosed heating system experiment results – Day 1 ......................................... 63 Figure 60: Enclosed heating system experiment results – Day 2 ......................................... 63 Figure 61: Enclosed heating system experiment results – Day 3 ......................................... 64 Figure 62: Enclosed heating system experiment results – Day 4 ......................................... 64 Figure 63: Enclosed heating system experiment results – Day 5 ......................................... 65 Figure 64: Enclosed heating system experiment results – Day 6 ......................................... 65 Figure 65: Enclosed heating system experiment results – Day 7 ......................................... 66 Figure 66: Enclosed heating system experiment results – Combined 7 Days ...................... 66 Figure 67: Rock diagram of enclosed heating system .......................................................... 68 Figure 68: Diagram of ventilated cooling system .................................................................. 69 Figure 69: Solar heating system glazed ............................................................................... 70 Figure 70: Ventilated cooling experiment results – Day 1 ..................................................... 71 Figure 71: Ventilated cooling experiment results – Day 2 ..................................................... 71 Figure 72: Ventilated cooling experiment results – Day 3 ..................................................... 72 Figure 73: Combined Results: Ventilated cooling experiment – 3 Days ............................... 72 Figure 74: Enclosed cooling system diagram: Daytime ........................................................ 74 Figure 75: Enclosed cooling system diagram: Night-time ..................................................... 74 Figure 76: Enclosed cooling experiment results – Day 1 ...................................................... 76 Figure 77: Enclosed cooling experiment results – Day 2 ...................................................... 76 Figure 78: Enclosed cooling experiment results – Day 3 ...................................................... 77 Figure 79: Combined Results: Enclosed cooling experiment – 3 Days ................................ 77 Figure 80: Solar heating system application on newly built housing unit .............................. 81 Figure 81: Solar heating system application on an existing housing unit .............................. 82 LIST OF TABLES (All tables by Author unless referenced otherwise) Table 1: Heat storage characteristics of rock (Eckhoff and Okos 2013: 4) ..........................10 Table 2: Calculation for heat storage material required (Eckhoff and Okos 2013: 6)...........11 Table 3: Optimum solar angles (Le Roux, 2019: 15). ..........................................................12 Table 4: Integrating the main aim, sub problem and hypothesis..........................................15 Table 5: The researcher’s paradigm indicated on the model developed by Laubscher (2011:15) .............................................................................................................................18 Table 6: Summary of research styles ..................................................................................19 Table 7: Summary of the research design ...........................................................................20 Table 8: Total rock required for heat storage. ......................................................................39 Table 9: Pilot study part 1 results ........................................................................................44 Table 10: Cost analysis .......................................................................................................83

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Eckhoff S.& Okos,M., (2013). Suggestions on selecting and using thermal storage materials and facilities, Purdue University Cooperative Extension Service, vol. 1, pp. 1-10.

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SABS & NRCS, (2011). Energy efficiency in buildings, South African National Standards, SANS 204:2011, pp.30.

Sicre B. & Baumann P., (2015). High-efficiency ventilation and heating systems by means of solar air collectors for industry building refurbishment, International Journal of Low-Carbon Technologies, vol. 2, pp.130-142.

Sözen A., Khanlari A., Tuncer A.D., Şirin C., Afshari F.&Güngör A., (2020). Wool packed solar air heater made with waste material, Empirical Investigation of Small Scale Aluminium, March 2020, pp.6-9.

The Housing Development Agency (HDA), (2017). South Africa: Informal settlement status, South Africa Research Report, viewed 20 July 2020, from http://www.thehda.co.za/uploads/files/HDA_Informal_settlements_status_South_Africa.pdf Vyas S. & Punjabi S., (2014). Thermal performance testing of a flat plate solar air heater using optical measurement technique, Material Science, vol. 3, pp.1.

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