OpenUCT :: Browsing by Author "Hughes, Alison"

Browsing by Author "Hughes, Alison"

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Open Access
An Evaluation of The Performance and Comparative Cost of Ground-mounted and Rooftop Mounted Solar Photovoltaic Systems
(2020) Leighton, Michael; Hughes, Alison; McCall, Bryce
In South Africa, there is an increasing interest in installing rooftop mounted solar photovoltaic systems. However, financing the photovoltaic systems causes most interest to be abandoned, largely due to the cost required to replace a building's asbestos roof. An alternative solution to replacing an asbestos roof is to install a ground-mounted photovoltaic system, which is more costly compared to a rooftop mounted system. This study aims to determine if a ground-mounted or a rooftop mounted solar photovoltaic system is the most financially feasible solar photovoltaic configuration. In this study three photovoltaic systems were analysed, all of which are installed in Atlantis, Western Cape (WC). Since all three systems are in the same area, they are all exposed to the same metrological conditions, allowing for identical energy generation potential. Two of the photovoltaic systems are ground-mounted systems located respectfully at the South African Renewable Energy Incubator (SAREBI) and at Stripform Packaging. The third system is a rooftop mounted system located at SA Tyre Recyclers. The photovoltaic system at SAREBI is a 9.75 kWp system consisting of 30 Canadian Solar CS6U-325P modules, one Schneider Electric 20 kW inverter, a tilt angle of 15° and an azimuth angle of -19°. The photovoltaic system at SA Tyre Recyclers is a 231 kWp system consisting of 700 JA Solar JAP72S-01-330-SC modules, 7 SolarEdge 27.6 kW inverters, a tilt angle of 13° and an azimuth angle of 22°. The photovoltaic system at Stripform Packaging is a 20.1 kWp system consisting of 60 Canadian Solar CS6U-335P modules, one SMA 20 kW inverter, a tilt angle of 15° and an azimuth angle of 46°. To achieve the aim of this study, the performance of each of the solar photovoltaic systems was examined, by comparing their annual specific yield. After which the technical aspects and differences of each of the photovoltaic systems were explored, to illustrate how each of the systems differ technically and how each system can be improved. Finally, the comparative cost of each of the solar photovoltaic systems was examined by analysing the levelized cost of energy (LCOE) and the payback period for each of the photovoltaic systems. The results demonstrated that from an annual specific yield perspective, the ground-mounted configuration was the best performing, whilst from a financial perspective, the rooftop mounted configuration had the lowest levelized cost of energy (LCOE) and payback period. However, installing a ground-mounted system is more financially feasible than replacing an asbestos roof and then installing a rooftop mounted system. In conclusion, by fully understanding the performance, payback period and levelized cost of energy, a clear understanding of potential risk can be determined, thus making the installation of photovoltaic systems more appealing for financiers. It is recommended that this study be repeated in a manner in which each of the photovoltaic system configurations are constructed consisting of all the same photovoltaic components, measuring equipment, tilt and azimuth angles. All of which would result in two identical photovoltaic systems where one is installed on a rooftop and the other installed on the ground. Once the two photovoltaic system configurations are equal in all aspects, an accurate comparison to determine which configuration is the most optimal performer and which is the most financially viable will be possible.
Open Access
Cape Town energy futures: Policies and scenarios for sustainable city energy development
(University of Cape Town, 2005) Winkler, Harald; Borchers, Mark; Hughes, Alison; Heinrich, Glen; Visagie, Eugene
The purpose of this report is to develop some scenarios for Cape Town’s energy future. The simulation model, the Long-Range Energy Alternatives Planning (LEAP) system, has been used to simulate how energy might develop in Cape Town over the twenty years from 2000 to 2020. These developments are driven not only by the nature of the energy sector itself, but also by broader factors, notably population, household size, economic growth (which may vary by sector) and other factors. The report builds on previous work done on the ‘state of energy’ for Cape Town (CCT & SEA 2003). That report was useful in capturing the current status of energy in the city, informed the City Energy Strategy conference and Cape Town’s own strategy (SEA, CCT & ICLEI 2003) and provided the starting data for this study. This report takes the work further in developing a tool that simulates what might happen to energy in the future, in a business-as-usual case and with policy interventions. A range of policy interventions are selected, and how these would change energy development in the city is examined, compared to a reference case. Interventions were selected based on various criteria, including implementation cost and technical feasibility, environmental priority, and political will. Different policies can be grouped for their sectors – industry, residential, commercial, government and transport – and also combined to form multiple-policy scenarios. These scenarios should be understood as a series of ‘what if’ questions, e.g. what if the City of Cape Town increased efficiency in its own buildings. The scenarios are not any prediction of the future, nor are any of these scenarios considered more likely than others. Instead, we report the implications of different policies and scenarios. The implications for energy, environment (both local pollutants and global greenhouse gases) and development are of particular interest. This study reports the cost implications of different scenarios only to a limited extent, as to do this adequately for many of the scenarios is beyond the scope of the project. Areas where further work is required, including around costing, are also identified.
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Clean energy and development for South Africa: Results, Report 3 of 3.
(2007) Hughes, Alison; Haw, Mary
The objective of this document is to report on the scenarios considered and compare the costs and social impacts using the sustainability indicators. The scenarios reported on are the energy efficiency improvements in the commercial, industrial, transport and residential sector, an increased penetration of biofuels and renewables and increased use of nuclear energy. The scenarios contain alternative fuel and appliance choices. Deviations from the base case are introduced in order to determine the effect specific policies or actions will have on the final energy demand and related emissions and costs of the system.
Metadata only
Clean energy and development for South Africa: Scenarios, Report 2 of 3
(2007) Hughes, Alison; Haw, Mary
This report is the second of three reports outlining sustainable development pathways for South Africa. It forms part of the reporting for the project entitled “Clean Energy and Development for South Africa” funded by the British Foreign Commonwealth office. The study has three main objectives, firstly to update both the national LEAP and MARKAL models and the data developed and captured during the first integrated energy planning process. Secondly to project future scenarios for the South African energy system and develop “roadmaps” for sustainable development using sustainability indicators and thirdly to develop additional capacity for energy modelling in South Africa and in particular within the Department of Minerals and Energy (DME). The objective of this document is to lay out the scenarios considered. It attempts to clearly define and record all the assumptions used to develop the scenarios. As the model is to be made available to the DME for use by its energy modelers and planners on completion of the project, the document serves as a guide to the scenarios in the model for the energy officers who will be using it. All model results and sustainability indicators developed are reported in the third report. Sustainable development has several objectives, it aims to improve the environmental impact of energy use as well as the social impact of energy use. The scenarios are designed to offer insight into the effect that following different policy pathways will have on the goals of sustainable development.
Open Access
Determining the impacts of selected energy policies on Gauteng's residential energy consumption and the associated emissions using LEAP as a tool for analysis : implications for sustainable livelihoods for the poor
(2011) Senatla, Mamahloko; Hughes, Alison
Energy is a key factor in economic growth and also central to meeting basic socio-economic goals. The use and production of energy in South Africa is associated with greenhouse gas (GHGs) emissions and pollution problems. Gauteng‘s residential sector is faced with a slowing rate of electrification due to high in-migration rates and high pollution levels in households that use coal to meet their energy needs. This study analyses whether the energy policies in Gauteng can help to steer Gauteng‘s residential sector toward sustainable use of energy by reducing the energy demand and associated GHG and pollutants emissions. Long range Energy Alternative Planning system (LEAP) was used as a tool for analysis.
Open Access
Development and application of a multi-criteria decision-support framework for planning rural energy supply interventions in low-income households in South Africa
(2022) Dzenga, Bruce; Stewart, Theodor J; Hughes, Alison
Problems in the public policy decision-making environments are typically complex and continuously evolve. In a resource-constrained environment, several alternatives, criteria, and conflicting objectives must be considered. As a result, solutions to these types of problems cannot be modelled solely using single-criteria techniques. It has been observed that most techniques used to shape energy policy and planning either produce sub-optimal solutions or use strong assumptions about the preferences of decision-maker(s). This difficulty creates a compelling need to develop novel techniques that can handle several alternatives, multiple criteria and conflicting objectives to support public sector decision-making processes. First, the study presents a novel scenario-based multi-objective optimisation framework based on the augmented Chebychev goal programming (GP) technique linked to a value function for analysing a decision environment underlying energy choice among low-income households in isolated rural areas and informal urban settlements in South Africa. The framework developed includes a multi-objective optimisation technique that produced an approximation of a Pareto front linked to an a priori aggregation function and a value function to select the best alternatives. Second, the study used this model to demonstrate the benefits of applying the framework to a previously unknown subject in public policy: a dynamic multi-technology decision problem under uncertainty involving multiple stakeholders and conflicting objectives. The results obtained suggest that while it is cost-optimal to pursue electrification in conjunction with other short-term augmentation solutions to meet South Africa's universal electrification target, sustainable energy access rates among low-income households can be achieved by increasing the share of clean energy generation technologies in the energy mix. This study, therefore, challenges the South African government's position on pro-poor energy policies and an emphasis on grid-based electrification to increase energy access. Instead, the study calls for a portfolio-based intervention. The study advances interventions based on micro-grid electrification made up of solar photovoltaics (PV), solar with storage, combined cycle gas turbine (CCGT) and wind technologies combined with either bioethanol fuel or liquid petroleum gas (LPG). The study has demonstrated that the framework developed can benefit public sector decision-makers in providing a balanced regime of technical, financial, social, environmental, public health, political and economic aspects in the decision-making process for planning energy supply interventions for low-income households. The framework can be adapted to a wide range of energy access combinatorial problems and in countries grappling with similar energy access challenges.
Open Access
Energy emissions: a modelling input into the Long Term Mitigation Scenarios process
(Energy Research Centre, University of Cape Town., 2007) Hughes, Alison; Haw, Mary; Winkler, Harald; Marquard, Andrew; Merven, Bruno
Emissions from energy supply and use constitute by far the largest part of South Africa’s total greenhouse gas (GHG) emissions. Hence energy modeling is a key analytical basis for the information provided to the long-term mitigation scenarios (LTMS) process. This report contains the technical information provided by the energy modeling team at the Energy Rserach Centre, led by Alison Hughes, to the Scenario Building Team which developed the LTMS scenarios. The information was integrated into the overall Technical Report (with appendices), its Technical Summary and the Scenario Document.
Metadata only
Energy Modeling: A modelling input into the Long Term Mitigation Scenarios process
(2007) Hughes, Alison; Haw, Mary; Winkler, Harald; Marquard, Andrew; Merven, Bruno
Emissions from energy supply and use constitute by far the largest part of South Africa’s total greenhouse gas (GHG) emissions. Hence energy modeling is a key analytical basis for the information provided to the long-term mitigation scenarios (LTMS) process. This report contains the technical information provided by the energy modeling team at the Energy Rserach Centre, led by Alison Hughes, to the Scenario Building Team which developed the LTMS scenarios. The information was integrated into the overall Technical Report (with appendices), its Technical Summary and the Scenario Document.
Open Access
Greenhouse gas mitigation cost of energy from biogas : a techno-economic analysis of co-digestion of three types of waste in Cape Town
(2011) Malla, Lesego; Hughes, Alison; Von Blottnitz, Harro
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.
Open Access
An investigation into increased productivity of small scale anaerobic digesters by means of temperature management
(2018) Carolissen, Sanchez; Hughes, Alison; Von Blottnitz, Harro
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.
Open Access
Measuring the rebound effect of energy efficiency initiatives for the future: A South African case study
(2011) Davis, Stephen; Cohen, Brett; Hughes, Alison; Durbach, Ian; Nyatsanza, Kudakwashe
The rebound effect is a phrase which was originally defined to refer to the extent to which energy efficiency improvements are lost due to subsequent behavioural changes. This report documents almost three years of research work that set out to quantify the rebound effect of energy efficiency initiatives in South Africa’s residential sector, and to explore ways of mitigating that effect using awareness and education. Society is in an era where energy commodities are characterised by constrained supply, increasing demand, and higher prices, and where the harmful social and environmental externalities resulting from the conversion of primary into useful energy can no longer be ignored. Part of the solution to the sustainable energy provision and consumption challenge has focused on the technology devices used to convert primary and secondary energy to useful energy that can be used for lighting, water heating, space heating and cooling (and a host of other end-uses). Given that all energy demand can ultimately be traced to the energy required for survival, a study of the residential sector is the natural place to begin.
Open Access
Modelling the potential impact of net metering in South Africa
(2013) McCall, Bryce; Hughes, Alison; Merven, Bruno
This work has two main objectives, first to create a working energy model of South Africa’s electricity sector using the open source software; OSeMOSYS, and secondly, using this model to understand the unstudied effects of net metered capacity within the country and how this affects the planning of the energy sector in the future, which is done through processes such as the Integrated Resource Plan (IRP). Using a combination of electricity tariffs and solar PV price projections, and the Bass diffusion model, an estimated range of the total amount of installed MW capacity of rooftop solar PV within the residential sector of South Africa was determined.
Open Access
Policy options for the sustainable development of the power sector in Zambia
(2012) Tembo, Bernard; Hughes, Alison; Merven, Bruno
Many climate change studies project that occurrence of droughts (due to dry years) in Southern Africa will increase; this raises concerns over Zambia's electricity system. Currently, over 99% of Zambia's electricity is supplied by hydropower, which is vulnerable to droughts. With Zambia targeting to be a middle income industrialised country by 2030, it isimportant that the impacts of droughts on the electricity system are understood, and how the system's adaptive capacity can be improved. This is imperative if the system were to enhance economic development. The main focus of this research therefore, was to develop an understanding of how Zambia's electricity system would evolve in different economic and climatic scenarios. A comprehensive electricity model for Zambia was developed after reviewing literature on Zambia's electricity sector and energy planning in a developing country context. A Scenario planning approach was used to model and analyse the electricity system that would be required to meet demand in two climatic scenarios (average and dry year river-flows) and for different economic growth scenarios. The results showed that the supply system has to be increased in order to support economic development. In a dry year scenario, the availability of the hydro technologies reduces significantly and this leads to a considerable increase in the average generation cost of the system. The introduction of renewable energy and coal technologies into the system lessens the impacts of droughts. Carbon emitting technologies such as coal and oil are still viable supply options even with a carbon price of $50 per tonne. Only low and base-case growth scenarios need an explicit diversification policy since least cost policy in the high growth scenario (the middle income growth trajectory) leads to a diverse supply system. Implementing a diversification policy in the high growth scenario increases average generating cost without improving the system's adaptive capacity. The most cost effective way of increasing the system's adaptive capacity is by importing electricity and gradually increasing share of renewable and coal technologies in the system. Further research on how electricity trade in Southern Africa could be enhanced, should be done.
Open Access
Quantifying the energy needs of the transport sector for South Africa: a bottom-up model
(Energy Research Centre, University of Cape Town., 2012) Merven, Bruno; Stone, Adrian; Hughes, Alison; Cohen, Brett
Transport is a large consumer of energy in South Africa and vital for economic development. Currently the transport sector consumes 28% of final energy, the bulk of which, 97%, is in the form of liquid fuels. As the population grows and becomes wealthier, so the demand for passenger transport and private vehicles increases; similarly, rising GDP drives the demand for freight transport. Supply interruptions are costly to the economy and careful long‐term planning is required to ensure that there is sufficient infrastructure to support the efficient functioning and growth of the transport sector in the future.
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Technology learning for renewable energy: implications for South Africa's long-term mitigation scenarios
(Elsevier, 2009) Winkler, Harald; Haw, Mary; Hughes, Alison
Technology learning can make a significant difference to renewable energy as a mitigation option in South Africa’s electricity sector. This article considers scenarios implemented in a Markal energy model used for mitigation analysis. It outlines the empirical evidence that unit costs of renewable energy technologies decline, considers the theoretical background and how this can be implemented in modeling. Two scenarios are modelled, assuming 27% and 50% of renewable electricity by 2050, respectively. The results show a dramatic shift in the mitigation costs. In the less ambitious scenario, instead of imposing a cost of Rand 52/tCO2-eq (at 10% discount rate), reduced costs due to technology learning turn renewables into negative cost option. Our results show that technology learning flips the costs, saving R143. At higher penetration rate, the incremental costs added beyond the base case decline from R92 per ton to R3. Including assumptions about technology learning turns renewable from a higher-cost mitigation option to one close to zero. We conclude that a future world in which global investment in renewables drives down unit costs makes it a much more cost-effective and sustainable mitigation option in South Africa.

Browsing by Author "Hughes, Alison"

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