Desalination technologies are being used to augment access to safe drinking water around the world. Nonetheless, most of these technologies are energy-intensive and driven by fossil fuels which emit greenhouse gases into the atmosphere, thereby contributing to climate change. Additionally, fossil fuels are non-renewable sources of energy and the exhaustion of such reserves can cause a threat to energy security. Consequently, exploitation of sustainable sources of energy for the desalination process has attracted a lot of attention. One such strategy is the use of a solar still which utilises solar energy to produce fresh water from saline or brackish water. However, the major drawback of a solar still lies in its low productivity. Many studies have investigated means of increasing the productivity of a solar still. One such technique which has recently been studied is to disperse nanoparticles into the impure water inside the basin of a solar still in order to obtain a nanofluid with enhanced optical and heat transfer characteristics. Since this is a relatively new topic, very few numerical studies on solar stills with nanofluids are available. Moreover, based on a literature review, no study examining the effect of nanoparticle size on the productivity of solar stills, and on the economic and environmental performance of solar stills was found. Additionally, the few available numerical studies on solar stills with nanofluids have not taken into account the view factor in the computation of the internal radiative heat transfer coefficient. Therefore, the aim of this study was to investigate both numerically and experimentally the effect of nanoparticle size on the performance of solar stills. Mathematical models with the view factor (Model 1) and without the view factor (Model 2) were developed for single slope solar stills, and a code was written in MATLAB software to solve a system of equations iteratively. Calculations were performed using climatic data from Stellenbosch (latitude 33.93°S, longitude 18.86°E) and University of Cape Town (latitude 33.96°S, longitude 18.46°E), South Africa, in order to evaluate the performance of solar stills with varying nanoparticle sizes. For the experimental phase, four identical solar stills were designed and built, and they were first tested with water only (base fluid) in all of them to test their performance and for calibration purposes. An Analysis of Variance (ANOVA) test was conducted on the experimental data collected from this first test. Subsequently, nanofluids containing aluminium oxide (Al2O3) nanoparticles of size 10 nm, 50 nm and 100 nm were used in three of the solar stills, with the other solar still containing the base fluid only. All the experiments were conducted at the University of Cape Town. The mathematical models were then validated using experimental data. Simulations in MATLAB based on Stellenbosch climatic data showed that for the month of January, which is a summer month in South Africa, the productivity of the solar still with the 10 nm, 50 nm and 100 nm Al2O3 nanoparticles was 9.01%, 8.94% and 8.89%, respectively higher than the productivity of the solar still with the base fluid only. On the other hand, for the month of July, which is a winter month in South Africa, the average productivity of the solar still with the 10 nm, 50 nm and 100 nm Al2O3 nanoparticles was 1.31%, 1.23% and 1.19%, respectively higher than the productivity of the solar still with base fluid only. In terms of the economic analysis, the simulations in MATLAB based on annual climatic data from Stellenbosch revealed that the cost of distilled water obtained from the solar still with the 10 nm, 50 nm and 100 nm Al2O3 nanoparticles was 10.42%, 6.21% and 3.51%, respectively higher than the cost of water obtained from the solar still with the base fluid only. Additionally, the payback period for the solar still with the 10 nm, 50 nm and 100 nm Al2O3 nanoparticles was 13.32%, 7.86% and 4.37%, respectively higher than the payback period for the solar still with the base fluid only. In terms of the environmental performance, the amount of carbon dioxide equivalent (CO2 equivalent) mitigated by the solar still with the 10 nm, 50 nm and 100 nm Al2O3 nanoparticles was 6.18%, 6.11% and 6.06%, respectively higher than the amount of CO2 equivalent mitigated by the solar still with the base fluid only. For the experimental phase, the ANOVA test based on the first set of experimental data (with base fluid only in all four solar stills) gave a probability-value (P-value) of 1.00. Moreover, experimental data collected from solar stills with base fluid and nanofluids revealed that the productivity of the solar still with nanoparticles of size 10 nm and 50 nm was 26.46% and 1.46%, respectively higher than the productivity of the solar still with base fluid only. On the other hand, the productivity of the solar still with nanoparticles of size 100 nm was 9.38% lower than that of the solar still with base fluid only. Furthermore, the root mean square error (RMSE) for the solar stills with nanofluids for Model 1 and Model 2 was 22.02% and 36.03%, respectively. It was confirmed that the performance of the calibrated solar stills was not significantly different. Moreover, the enhancement in the productivity of a solar still with nanofluids is much more distinct in summer than in winter. It was also demonstrated that the productivity of a solar still decreases with increasing nanoparticle size. Additionally, it was established that the cost of distilled water, the payback period and the amount of mitigated CO2 equivalent decrease with increasing nanoparticle size. Theoretically, the distillate yield and environmental performance of a solar still with nanofluids were marginally sensitive to the nanoparticle size while the cost of distilled water and payback period were significantly affected by the nanoparticle size. The effect of nanoparticle size on distillate yield was experimentally significant. Finally, it was demonstrated that the inclusion of the view factor improves the accuracy of modelling of solar stills with nanofluids.

This paper investigates, in the context of Cape Town the emission reduction potential (ERP) of energy from biogas and related cost. Two project-scale models and a city-scale model were developed. Substrates for project model 1 were organic fraction of municipal solid waste (OFMSW) and primary sludge (PS) from sewage works. Project model 2 considered waste paper sludge (WPS) and PS. For the city-scale model, substrates for project model 1 were extended to include total amounts of OFMSW and PS generated in Cape Town. Financial results show that at the REFIT tariff model 1 would have a higher internal rate of return (20.5%) than model 2 (5.6%). The landfill ERP of the project-scale models is 98 600 CO2 equivalent tons per year, corresponding to a weighted average capital investment of R372 per CO2 equivalent ton saved in year 1. The results for the city-scale model indicate that a landfill ERP of 458 000 CO2 equivalent tons per year can be expected at an investment cost of R287 per CO2 equivalent ton saved in year 1. Energy emissions from fossil fuels at city-scale are most effectively mitigated if coal rather than other fossil fuel based power and heat generation are replaced.

Energy poverty undermines development at a large scale. It is most overtly experienced in informal settlements, where the use of fuels like paraffin, charcoal and wood prove hazardous and harmful to health and wellbeing. The expenditure on and use of energy services in informal settlements are largely undefined, which severely undermines the success of energy access and safety initiatives. Despite the poverty of informal settlements, mobile phone ownership is high in these areas. This research aims to explore the potential and applicability of a digital data collecting systems using a mobile application that is accessible on entry-level mobile phones with basic internet access to collect information about energy access, affordability and multiple fuel use in these areas. As part of this research, a mobile application platform and data collection platform was developed which enables survey design and data collection in real time. The platform allows for creation of weekly surveys that question energy use, expenditure and affordability; it also offers other functions that are designed to increase awareness of fuel safety and efficiency. The application was piloted in lmizamo Yethu in Cape Town. Six weeks of continuous data was extracted from 200 users using airtime incentives with an overall reach of 306 households. The quality and quantity of data received was of high calibre. The results indicate that the potential for using this system and mobile phones as a data-collecting tool in Africa is high.

Includes bibliographical references. / South Africa has its fair share in the global greenhouse gas (GHG) emissions, with recorded 2010 emissions per capita of 10tons/year. This is caused by the energy supply of the country which relies heavily on fossil fuels to drive its energy intensive economy. If this continues under “business as usual”, consequences like water and food shortage may be exacerbated. The waste sector has a share of 3 in national GHG emissions. These are caused by methane from biogas produced through anaerobic digestion of organic waste. The objective of this study was to assess the potential contribution that can be achieved in reducing the national GHG emissions by converting waste emissions into useful energy or capturing and destroying them. Three waste resources were investigated because of their abundance in the country: municipal solid waste, municipal wastewater and livestock manure. The national picture of municipal waste was extrapolated from the waste data available in 7 metros in the country (City of Cape Town, Johannesburg, Tshwane, Ekurhuleni, EThekwini, Nelson Mandela Bay, and Buffalo City municipalities). Projected GDP and population growths were used as indicators for extrapolating the national data. The total national organic waste derived from these waste categories was used to estimate their emission share in national GHG emissions and biogas generation in terms of methane production from each waste type. This was forecasted from 2010 to 2025. The methane gas production was optimised by assuming different waste combinations like: municipal solid waste and wastewater, wastewater and livestock manure, and remaining wastewater. In addition, the possible amount of electricity or heat produced from this biogas was estimated. This useful energy was used to evaluate the emission reduction potential (ERP) in the national GHG emissions of the country under “growth without constraints”. All these computations were performed by using MS Excel software. It was found that the total organic waste predicted during this period varied from 12 to 17Mton, with the waste emissions share being about 2 of the national GHG emission. Methane generated from this waste was about 644-1075Mm3 while the total optimal methane generated from these waste combinations was estimated to be 1770- 2650Mm3. In addition, 673-1123GWh of electricity and 1255-2150GWh of heat could be produced (without optimization) from methane over the same period of the forecast. For optimal methane production, the possible useful energy was estimated to be 1362-2037GWh of electricity and 2894- 4362GWh of heat. The ERP of methane capture and conversion to useful energy was about 2.1- 2.5. It is concluded that a) capturing and utilisation of methane gas from waste contributes to the reduction of the GHG emissions, b) optimisation of biogas production from waste increase methane yield and therefore useful energy, and c) the best contribution of biogas in climate change mitigation in South Africa would come from the optimal production of methane from waste.

Includes bibliographical references. / The South African wine industry has seen a growing interest in the field of renewable energy in recent years. This has been due, in part, to rising energy costs a long with increased public and consumer awareness around the issues of global warming and sustainability. This project was conceived in the light of these developments, and centres on an investigation into the feasibility and design of a renewable - energy portfolio for the Klein Constantia Wine Estate, located in the Western Cape. A literature survey was undertaken, shedding light on the common uses of energy on wine farms, renewable energy initiatives within the industry and the technologies available. A case study was then conducted using Klein Constanta Wine Estate as the subject. Physical measurements were taken where possible and, along with a combination of topographical, satellite and local climate data , were used to develop estimates f or the energy - generation potential of the farm's renewable resources and the cost implications thereof. Following this, a qualitative and quantitative analysis was conducted to determine the most favourable technologies from a portfolio design perspective. From these findings, three potential portfolio designs were developed, each covering varying degrees of the farm's energy consumption. Based on the se final designs, it was concluded that there was indeed significant potential for investment in renewable energy at Klein Constantia; and that the farm could more than cover its energy requirements. While the financial returns would be minimal, with relatively long payback - periods, the secondary benefits to the farm were considered to be sufficient to justify the investments. The final decision, however, would likely rest on the weight given to the secondary benefits by the farm owners. It was also determined that, in the case of Klein Constantia, the larger the investment the less secure it would be. This was primarily due to the need for higher - risk and more expensive technology options being required when the energy target was raised. With this in mind a renewable energy portfolio, covering only the farm's electricity use, was found to be the most favourable option available to the farm.

Men's and women's time-use in relation to wellbeing is well-investigated and understood within the context of the developed world. There has been limited research into the gendered experiences of time-use and three dimensional (3D) wellbeing in rural communities of sub-Saharan Africa and particularly so in semi-arid areas. As a result, failure to appreciate how time-use and wellbeing are experienced by the rural population in semi-arid areas impedes a full understanding of how rural inhabitants spend their time and how this makes them worse off or better off in different aspects of their wellbeing. This subsequently challenges the appropriateness of efforts to improve the lived experience of rural inhabitants. The study aimed to make a contribution to the knowledge gap on time-use and wellbeing by assessing how time-use relates to the experiences of material, subjective and relational aspects of wellbeing in a semi-arid area. It hypothesised that if men and women who are household-heads spend their time-use differently this has implications on their experiences of material, subjective and relational wellbeing. The study adopted a quantitative approach to primary data collection, analysis and interpretation of results. A questionnaire survey consisting of 93 randomly selected male and female headed households was conducted using stratified sampling techniques. Data was analysed using Microsoft Excel and SPSS software including regression analysis and statistical tests (Mann Witney U test) from which descriptive and statistical results were presented in tables and graphs following regression analysis. The study yielded several findings including the importance of personal care for improved subjective wellbeing despite the trade-off with material wellbeing; the importance of age and social grants for ensuring a better experience of material wellbeing; the importance of social connections particularly for widows and widowers; as well as the significance of time spent on leisure and work-outside for improving relational wellbeing. In addition, women's disproportionally high time spent on domestic work leaves them feeling subjectively worse-off while the persistence of traditional gender role division seems to have a determining effect on the time-use and wellbeing experiences of household-heads in the study area. Overall, the study highlights time-use related opportunities and constraints for improving the wellbeing of rural inhabitants in Onesi, Namibia.

To deal with the adverse impacts of climate change, index-based or parametric insurance has been recognized as an adaptation technique to compensate farmers for economic losses from extreme weather events. The insurance can be either private or sovereign. African Risk Capacity Insurance (ARC Ltd) offers the latter to African countries against drought events through contingency planning, risk pooling and transfer facilities. While the ARC insurance initiative seems promising, the current approaches used to estimate risk and determine premiums do not consider the change in risk from anthropogenic climate change. As the frequency of extreme weather events changes, the price of insurance premiums is likely to rise. Representing a cutting-edge science from weather to impact attribution, this study links attribution modelling with parametric insurance modelling to quantify how the probability of drought events has changed due to human influence on the climate system and translates the impacts into actual costs. To quantify this change, global climate models consisting of both factual and counterfactual world (with and without human forcing of climate, respectively) experiments were post-processed and used as rainfall inputs into an insurance risk modelling software, Africa RiskView. Estimated response costs needed for drought assistance in a world with and without climate change were calculated in Malawi, Zimbabwe, Senegal and Mauritania for the last 30 years. The empirical cumulative distribution function plots show that the distributions of models that represent the counterfactual natural world estimate lesser drought-affected population and lower response costs for assistance than those of the factual world distributions. The results suggest that climate change is likely to increase the price of insurance premiums. Therefore, there is a need for blended financing models that integrate international climate funds generated on a responsibility-based approach to cater for the added cost brought in by climate change.

Building ventilation is crucial for improving the indoor air quality and thermal comfort. Nowadays, mechanical ventilation systems such as air conditioning and fans are most commonly used in buildings. However, these devices consume a lot of electricity which is mainly generated from the combustion of fossil fuels, resulting in the release of greenhouse gases and thereby contributing to climate change. Consequently, it is essential to switch to natural ventilation systems which are environmentally friendly as they are based on renewable sources of energy. One such type of natural ventilation system is the solar chimney which can either be roof-mounted or wall-mounted in buildings. The aim of this study was to develop a mathematical model for assessing the thermal performance of roof-mounted (inclined) and wall-mounted (vertical) solar chimneys. The model was validated using numerical simulations in MATLAB. Different configurations of solar chimneys were designed and modelled in MATLAB in order to compare their performances, in terms of the ventilation rate expressed as the number of air changes per hour, ACH. Raw climatic data, including the intensities of global and diffuse solar radiation on a horizontal plane, wind speed and ambient temperature were obtained for Stellenbosch, located in the Western Cape Province of South Africa. This was used for the MATLAB modelling of the solar chimneys. The effects of inclination angle, air gap, chimney height and view factor on the thermal performance of solar chimneys were explored in this study.

This research work is on the determination of the properties of palm oil as potential base oil for producing bio based lubricants. The samples analysed were obtained from the open markets in the South West, South East and South South zones of Nigeria. Some of the physical and chemical properties such as viscosity, flash point, pour point, cloud point, specific gravity, acid number, noack volatility and aniline point were analysed. The samples were degummed, neutralised and bleached to remove the red colour (carotene) and gummy materials. The bleached samples were tested to determine the above mentioned properties. Comparison of the crude palm oil and the bleached samples with the conventional lubricants Mobil Super SAE20W40 and Mobil gear oil SAE75W90 was made. Finally, it was observed that the crude palm oil and the bleached sample exhibit good lubricating characteristics to be used as base oils for formulation of bio-lubricants. Despite palm oil being a food crop, an abundance of available land and the scale of prospective market demand suggest that commercial cultivation is unlikely to negatively affect food cultivation and the prices of food products.

The use of biological waste as a primary energy source for the production of biogas, by the process of anaerobic digestion, has been commonly used in the past by small communities and on a larger scale by waste water treatment plants. In the latter, the biogas is traditionally used for heating of the digesters in order to increase process performance. Smaller scale anaerobic digesters using food waste as a primary energy source for biogas production could be implemented for residences and restaurants. The biogas produced could be used for cooking and heating purposes. Whilst common designs for such smaller digesters do not provide for heating, there may be warm waste water on site to elevate the operating temperature and thus improve gas yield. This dissertation reports an experiment aimed at improving the performance of an existing anaerobic digester located at the Leo Marquard Hall (LMH) residence of the University of Cape Town. The 6 m³ digester has been operated using food waste as its sole substrate. The volume of gas produced is unknown as there are no gas measurement devices on site. In the past it has been roughly estimated from pressure readings before and after gas use. The digester operates at ambient temperature which averages 16 °C over the year, which is suboptimal. The anaerobic digester is not equipped with a temperature measurement device to monitor operating temperature. Two hypotheses were formulated and tested. The first stated that the temperature profile of the waste water leaving the LMH residence will have peaks in the morning and evening periods when the majority of students shower. The peak temperature periods will be in the morning before breakfast and in the evening after dinner. The temperature during these times is expected to be above 30 °C. In order to test the first hypothesis, a thermocouple with temperature data logger was installed to record the temperature of waste water in the manhole drain leaving the LMH residence. The temperature data recordings confirmed the temperature peak of waste water leaving LMH residence at an average temperature of 30.5 °C in the morning. However, a clear evening temperature peak was not identified. Thus the hypothesis was only true for the morning temperature peak of waste water leaving LMH residence for weekdays when lectures take place. The second hypothesis stated that, adding a portion of the 30 °C waste water into the LMH anaerobic digester will result in the digester running at 5 °C above the normal average operating temperature, and thus increase the productivity of the anaerobic digester. In order to test the second hypothesis the design and installation of a pumped pipe system was completed in order to pump waste water from the LMH residence waste water outlet manhole gravity sewer to the LMH anaerobic digester. By loading the LMH anaerobic digester with 600 ℓ of warm waste water, the maximum digester temperature increase obtained was 5 °C relative to the normal cold water operation. The maximum increases in total weekly biogas and methane production achieved were 238 % and 260 % respectively, relative to the average weekly cold water operation. The operating temperature of small scale anaerobic digesters is a very important factor for the performance of the anaerobic digester. This research shows that increasing the operating temperature of a small scale anaerobic digester by as little as 5 °C could double the performance of the anaerobic digester. The site location for the installation of small scale anaerobic digesters should be investigated at design stage by taking into consideration the operating temperature. The digester could be installed in close proximity to both an organic waste stream and warm waste water stream that could affect the feasibility of a particular project installation.