Centre for Renewable and Sustainable Energy Studies
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Stellenbosch University has been awarded the responsibility to act as the hub of a Postgraduate Programme in Renewable and Sustainable Energy Studies by the South African National Energy Research Institute (SANERI), a division of the Central Energy Fund (CEF). The overall objective of this initiative is to develop and enhance national capacity in renewable and sustainable energy in support of accelerated and shared economic growth within the area of sustainable energy. This will be achieved by building the human resource capacity, create and disseminate knowledge, and lastly to stimulate innovation and enterprise in the field of renewable and sustainable energy.
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- ItemAerodynamic optimisation of a small-scale wind turbine blade for low windspeed conditions(Stellenbosch : Stellenbosch University, 2006-12) Cencelli, Nicolette Arnalda; Von Bakstrom, T. W.; Denton, T. S. A.; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronical EngineeringENGLISH ABSTRACT: Wind conditions in South Africa determine the need for a small-scale wind turbine to produce useable power at windspeeds below 7m/s. In this project, a range of windspeeds, within which optimal performance o the wind turbine is expected, was selected. The optimal performance was assessed in terms of the Coefficient of Power(Cp), which rates the turbines blade's ability to extract energy form the avalible wind stream. The optimisation methods employed allowed a means of tackling the multi-variable problem such that the aerodynamic characteristics of the blade were ideal throughout the wind speed range. The design problem was broken down into a two-dimensional optimisaion of the airfoils used at the radial stations, and a three-dimensional optimisation of the geometric features of the wind rotor. by means of blending various standard airfoil profiles, a new profile was created at each radial station. XFOIL was used for the two-dimensional analysis of these airfoils. Three-dimensional optimisn involved representation of the rotor as a simplified model and use of the Blade Element Momentum(BEM) method for analysis. an existimg turbine blade, on which the design specifications were modelled, was further used for comparative purposes throughout the project. The resulting blade design offers substantial improvements on the reference design. The application of optimisation methods has successfully aided the creation of a wind turbine blade with consistent peak performance over a range of design prints.
- ItemAgricultural residue as a renewable energy resource(Stellenbosch : University of Stellenbosch, 2011-03) Potgieter, Johannes George; Van Niekerk, J. L.; De Lange, L.; University of Stellenbosch. Faculty of Engineering. Centre for Renewable and Sustainable Energy StudiesENGLISH ABSTRACT: In the Greater Gariep agricultural area adjacent to the Orange River between Prieska and the Vanderkloof dam alone an estimated 311 000 ton/yr of maize and wheat straw is available. These agricultural residues have an energy equivalent of 196 000 ton of coal per year and should be utilised as a renewable energy resource. A technical and financial evaluation on the collection and transport of agricultural residue showed that the Hopetown area has the highest concentration of agricultural residue in the Greater Gariep agricultural area with approximately 68 000 ton/yr that is spread out over 76 kmª. Briquetting, combustion, pyrolysis and gasification were identified as the technologies with the highest potential to convert agricultural residue into a higher grade energy product in this area. The expected overall energy conversion efficiency for a plant capacity between 5 000 to 100 000 ton/yr is 98.9%, 10-25%, 25-30% and 28-36% for the briquetting, combustion, pyrolysis and gasification plants respectively. A financial evaluation based on the internal rate of return and the net present value of investment showed that the briquetting plant is financially feasible and the most profitable for capacities between 25 000 and 60 000 ton/yr while the pyrolysis plant was financially feasible and the most profitable technology for capacities greater than 60 000 ton/yr. A sensitivity and risk analysis done on the proposed briquetting and pyrolysis plants to evaluate the impact of market fluctuations on the profitability of the power plants exposed the briquetting plant as a very high risk investment, mainly because of the sensitivity to the selling price of fuel briquettes and the high maintenance cost associated with the briquetting equipment. Although the proposed pyrolysis plant is sensitive to variation in the electricity price, the risks associated with the market conditions for the pyrolysis plant is very low and an internal rate of return of 15% is still projected at the minimum expected electricity price. From the study it is clear that the utilisation of agricultural residue available in the Greater Gariep agricultural area is technically and financially viable.
- ItemAn automotive interior lighting application using white light-emitting diodes(Cape Town : Cape Town University, 2008) Solomon, Ramzi; Pillay, P.; Sebitosi, A.B.; Stellenbosch University. Faculty of Engineering. Department of Mechanical and Mechatronic EngineeringEnergy drives technological societies. Developing countries such as South Africa are caught between the desperate need for economic growth and the emerging obligations to the environment. Efficient technologies can be used to mitigate the impact of these seemingly conflicting requirements in urban and rural environments. In this thesis the commercially available white light-emitting diode (LED) with its inherent efficiency, longevity and mechanical strength, is used to show, that success in energy efficiency can be obtained. Two cases are used to illustrate the need for efficient demand-side technology: the electricity shortages of the Western Cape Province in South Africa and a white LED pilot project in Namulonge, Uganda. The Namulonge Solar-Home System (SHS) is analyzed with the intention of creating a more acceptable general lighting solution. The concept of appropriateness through self-determination is discussed within the context of location-specific information integrated into a design procedure. The major thrust and contribution of this thesis, however, is the design of an interior luminaire for Golden Arrow Bus Services (GABS). This is in part based on the hypothesis that application-specific information will lead to implementation and human-needs success, and is researched, designed, fabricated and then laboratory tested. The biggest challenge to be overcome was the spatial light distribution of the LED array. Thus non-imaging optical lens design became the main focus of this project as it held the key to utilizing available light while conserving the light-systems energy. Circular Fresnel and Linear Fresnel (an adaptation of the concentric design) lenses were designed. Electrical, mechanical and thermal aspects of design are also detailed. Far-field, horizontal plane detection over the specified area is used to best gain the uniformity of distribution. The four criteria namely luminance, illuminance, intensity and étendue (collection efficiency), against which each design and focal length iv configuration is compared to, are extensively explored and eventually lead to a final design. In the first designs, the area of the spatial distribution between 50% and 80% of its relative intensity is collimated. The Hybrid Circular Fresnel and Hybrid Linear Fresnel lenses now redirects the relative intensity in two areas, from 50% to 70% (creating parallel rays) and then from 70% to 100% (away from the central axis), renders a distinct difference is spatial uniformity and a reduction in the peak and offaxis located intensity. All four criteria are met, with a minor adjustment of configuration within the bus internal luminaire spacing, with the hybrid designs. It is proposed that GABS employ polished designs of the Hybrid Circular Fresnel, in any of the configurations, which have collection efficiencies ranging between 64.8% and 78.3%.
- ItemBiodiesel analytical development and characterisation.(Stellenbosch : University of Stellenbosch, 2010-03) Prah, Ebenezer; Callanan, L. H.; Lorenzen, L.; University of Stellenbosch. Faculty of Engineering. Dept. of Process Engineering.ENGLISH ABSTRACT: Development of analytical methods to characterise biodiesel has become central to the overall success of the marketing of biodiesel fuel. In this regard, different bodies including the American Society for Testing and Materials (ASTM) and the European normalization (EN) have come up with various methods to determine important biodiesel parameters such as total glycerol, methanol and the fatty acid methyl esters (FAMEs), etc. Various studies have been conducted on the parameters mentioned above using a variety of instrumentation and sample preparations. The best methods reported are those that have been adopted by both the ASTM and EN standards. The purpose of this study was to develop alternative analytical methods to both the recommended ASTM and EN methods and, in some cases, to make modifications to both standards (ASTM D 6571 and EN 14214) and methods to determine total and bound glycerol, the ester content and also methanol content in biodiesel. Moreover, water washing after transesterification and the effect this practice has on biodiesel cold flow properties such as kinematic viscosity, cloud and pour point and density were evaluated. The possibility of using the iodine value to predict the feedstock source of an unknown biodiesel was also investigated. Six different vegetable oil samples were transesterified with methanol and used for this study. The six samples used were palm, crown, sunflower, waste vegetable oil (wvo), peanut and rapeseed biodiesel. Quantitative results indicated that the use of programmable temperature volatilisation (PTV) for total glycerol did not produce the required repeatability of between 1-4% relative standard deviation(RSD) for total glycerol analyses in biodiesel with precision of 25%, 86%, 25% and 56% for free glycerol (FG), monoglycerides (MG), diglycerides (DG), and triglycerides (TG) respectively. The standard requires a relative standard of between 1-4% As an alternative to the method using gas chromatography, normal phase high performance chromatography (HPLC) with binary gradient elution was used to determine the bound glycerol content. This method proved accurate and repeatable with RSD % of 0.33, 1.12, and 1.2 for TG, DG and MG respectively. Following the EN14103 protocol (European standard ester determination), the Zebron ZBWAX column which is comparable to the specification recommended by EN14103 but afforded the determination of ester content from the esters of myristic acid (C14:0) to behenic acid (C22:0) with reproducibility with RSD % of 6.81, 1.91, 7.27, 0.64, 1.18, 1.55, 6.03, 1.96, and 5.21 for methyl esters of myristic, palmitic, stearic, oleic, linoleic, linolenic, arachidoic, gadoleic and behenic acid respectively. Solid phase micro extraction (SPME) using GC-MS was developed as an alternative to both the EN14110 and ASTM D93 protocols for determining the methanol content in biodiesel. For this method, polyethylene glycol fibre (PEG) was used together with a deuterated methanol internal standard and a DB-FFAP (60m×0.25um×0.25um) column. Less volume of sample was required as compared to the EN14214 method. This method was found to be sensitive, accurate and repeatable with a RSD % of 4.82. The Iodine number of biodiesel decrease compared to their corresponding feed stock and therefore predicting the feed stock of an unknown biodiesel was going to be difficult .Results from this study indicated that it is not possible to predict the feed stock source of an unknown biodiesel from its iodine value. The effect of water washing after phase separation on biodiesel cold flow properties such as kinematic viscosity, density, cloud and pour point depended on the type of biodiesel produced. We observed that water washing after transesterification caused an increase in all the cold flow properties of sunflower biodiesel, whereas only the densities and kinematic viscosities increased in the case of palm and waste vegetable oil biodiesel. The cloud and pour point of the latter two diesel samples remained unchanged after water washing. Thus, the effect of water washing on biodiesel cold flow depended on the type of biodiesel. Blending a highly saturated biodiesel (fewer numbers of double bonds) with a less saturated biodiesel (higher number of double bonds) resulted in an improvement of both the pour and cloud points of the resultant biodiesel blend.
- ItemCharacterisation of a solar roof tile (SunSlates™) : with focus on local applicability and conditions(Stellenbosch : Stellenbosch University, 2008-12) Rautenbach, Karel Frederick; Swanepoel, R.; Meyer, R.; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.Three SunSlates™ were investigated to predict the performance of a fully installed system. The three slates were mounted on a fixed tilt of 30°, but with different orientations. The tilt is close to latitude of the Stellenbosch site, which is 33.92°. The one faces due east, another due west and last due north. This is to determine the effect that orientation has on the energy from the SunSlates™. Another slate, also facing north, was mounted on an adjustable framework. The framework was used to adjust the tilt angle of the slate, the orientation of the slate was constantly north. This slate was used to determine the effect of tilt on the total daily energy produced by the slate. To determine the performance of the slates daily measurements of temperature, solar insolation and wind was taken. These were used to investigate the effects on the SunSlates™. During the test period, which scheduled from September to November, the results show a difference, smaller than commonly believed, in the daily and annual energy delivered from the differently orientated slates. The slates facing east and west, however, have similar energy outputs, even though the power profiles differ. The north facing slate has the highest annual energy output, as expected. It was found that during the months of summer, November to January, the optimal tilted slate (Slate tilted to have a incidence angle of 0° from solar rays at noon) had a slightly lower energy output, but higher maximum power output per day than the 30 degree tilted slate. This is in contrast to the energy output predictions for the winter months where in the winter the energy can be as much as double that of the 30 degree tilted slate. The thorough testing and expert installation of the SunSlates™ are essential. From the case study it can be seen that some problems during installation, possibly a single faulty slate or shadowing, can cause a complete system to lose 30% of its efficiency.
- ItemCommercial biodiesel production in South Africa : a preliminary economic feasibility study(Stellenbosch : University of Stellenbosch, 2007-03) Nolte, Mirco; Lorenzen, L.; University of Stellenbosch. Faculty of Engineering. Dept. of Process Engineering.Biodiesel, a fatty acid alkyl ester, derived from the transesterfication of vegetable oil, is considered a renewable fuel that can be used as a replacement for fossil diesel. The urgency for biofuel production in South Africa is motivated by the vulnerability of crude oil prices, high unemployment, climate change concerns and the need for the growing economy to use its resources in a sustainable manner. The technical feasibility of biodiesel production has been proven and this study investigates its preliminary economic feasibility in South Africa by looking at the market, financial and agricultural feasibility of commercial biodiesel production.
- ItemConcentrated solar power (CSP) innovation analysis in South Africa(Southern African Institute for Industrial Engineering, 2017) Craig, Toyosi Onalapo; Brent, Alan C.; Dinter, FrankSouth Africa aims to generate 42 per cent of its electricity from renewable energy technology sources by 2030. Concentrating solar power (CSP) is one of the major renewable energy technologies that have been prioritised by South Africa, given the abundant solar resources available in the region. Seven CSP plants have been, or are being, built; three of them are already connected to the national grid. However, the impacts of this technology on South African research, development, and innovation have not been investigated to date. This paper thus analyses the CSP technologies in South Africa in terms of the existing technology adoption models and diffusion strategies, used by government and its agencies, to improve the development and deployment of these technologies. It is found that CSP has been treated generally like other renewable energy technologies through the Renewable Energy Independent Power Producer Procurement Programme (REIPPPP), although a tariff plan for CSP plants of the future has been made. No specific technology diffusion or adoption model for CSP was found; so this paper explores how it can be developed.
- ItemCrystalline silicon solar cells - a glance from Europe(Stellenbosch : University of Stellenbosch, 2008-02-12) John, Joachim; University of Stellenbosch. Faculty of Engineering. Centre for Renewable and Sustainable Energy Studies.The invitation to the presentation by Dr Joachim John at the Stellenbosch University. A lecture on the Current and Future Technology of Thin Crystalline Silicon Solar Cells will be given on Tuesday 12 February 2008 at 15h00 in Room M203 of the Mechanical Engineering Building of Stellenbosch University on the corner of Joubert & Banghoek Street. Dr. John is Section Head, Team and Project Leader in the Process Technology Division at the Interuniversity Micro Electronic Centre (IMEC) in Leuven, Belgium, where he is presently engaged in the development of industrial Silicon solar cells. Dr. John has published more than 60 papers and presented 15 invited lectures at international conferences, holds 3 patents and has written 2 textbook chapters on the topic of solar cells.
- ItemDecoupling infrastructure services from unsustainable resource use : cases from Cape Town(Stellenbosch : University of Stellenbosch, 2011-03) Robinson, Blake; Swilling, Mark; University of Stellenbosch. Faculty of Economic and Management Sciences. School of Public Leadership.Please refer to full text to view abstract.
- ItemDesign and analysis of a gearless, direct grid, permanent magnet induction wind generator(Stellenbosch : University of Stellenbosch, 2011-03) Potgieter, Johannes H. J.; Kamper, M. J.; University of Stellenbosch. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.; Stellenbosch University. Faculty of Engineering. Centre for Renewable and Sustainable Energy StudiesENGLISH ABSTRACT: In this study a new type of gearless, direct-drive wind generator, which can be connected directly to the grid, is proposed. The working characteristics of this generator are based upon the principles of the permanent magnet induction generator (PMIG). By omitting the need for a gearbox and power electronic converter this generator type has several advantages regarding cost and reliability. Although the PMIG is proposed in previous studies as favourable for wind power generation, the mechanical complexity and difficult construction associated with these types of generators, seems to be the main reason why these generator systems are not used. The design methods presented in this study are intended to alleviate these constructional issues by proposing the split-PMIG (S-PMIG), where the stator winding and the induction cage-rotor windings are electromagnetically separated. The machine is basically split into two permanent magnet (PM) machines, a grid connected synchronous generator (SG) unit and a turbine connected induction generator (IG) unit. These two units are mechanically linked by a common PM-rotor. To evaluate this concept a finite element (FE) design analysis is done independently for both machine components. The emphasis of the design optimisation is the minimisation of the cogging torque, while still having a decent performing, easily constructible generator. This generator should also have low load ripple content. Cogging torque can result in the failure of the turbine to start up, especially at low wind speeds. As this is a directly grid connected generator, torque ripple transferred to the common PM-rotor can destabilise the generator. Based upon the FE designs a preliminary S-PMIG system is constructed and practically evaluated. Due to the modular nature of the design it is possible to implement the synchronous generator part of the S-PMIG in conjunction with a grid-connected solid state converter (SSC). This allows for a useful comparison with the S-PMIG system. Promising results are obtained from initial tests of the S-PMIG directly connected to the grid. It is shown that the operation of this generator is stable under a wide range of wind load conditions. However, some important machine design issues are identified from these practical results, which could prove vital in the implementation of future S-PMIG designs.
- ItemDesign of a pump-as-turbine microhydro system for an abalone farm(Stellenbosch : University of Stellenbosch, 2010-03) Teuteberg, B. H.; Van Niekerk, W.; University of Stellenbosch. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.ENGLISH ABSTRACT: This document details the design process of a 97 kW microhydro system for Roman Bay Sea Farm in Gansbaai in the Western Cape Province of South Africa. It contains a literature study of microhydro power, with a focus on the use of Pump-as-Turbine technology and direct-drive systems. The literature study leads to several possible concepts for the project, which are then evaluated and the most suitable design is found to be a reverse running pump that powers a different pump through a direct drive system. Experimental data from KSB is used to test the accuracy of various correlations that can be used to generate turbine-mode operation curves from pump curves. The final design parameters for the complete system are then determined, and presented along with a cost benefit analysis.
- ItemDesign, build and test a passive thermal system for a loft : a roof solar chimney application for South African weather conditions(Stellenbosch : Stellenbosch University, 2007) Beviss-Challinor, Lauren Margaret; Dobson, R. T.; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.ENGLISH: The design, construction and testing of a passive thermal system, a roof solar chimney, for a loft is considered. Unlike conventional solar chimneys the solar collector is constructed from corrugated iron roof sheets with the aim that it can be integrated into existing buildings at a lower cost or used in low cost housing developments. The main objective of the study was to determine the feasibility of such low-cost design to regulate thermal conditions in a loft, that is heating the loft during winter and enhancing natural ventilation during summer, by carrying out an experimental and analytical study. The results obtained from the experimental study showed that for winter the solar chimney, having a channel width, depth and length of 0.7 m, 0.1 m and 1.8 m respectively and with a peal solar radiation of 850 W/m², heated the room air 5°C higher than the ambient temperature during the hottest periods of the day, which is only marginally better than a loft with conventional roof insulation. At night, it was found that reverse airflow occurred through the chimney, cooling the loft down to ambient temperature, due to radiation heat loss from the roof collector to the night sky. For summer operation, the experimental data showed that the chimney was able to maintain the loft at ambient temperature and the analytical study found that the chimney was able to enhance natural ventilation effectively, reaching air exchange rate of 6.6 per hour for the 4.6 m³ volume space. It was also found that the chimney’s performance dropped rapidly and significantly during periods of low solar radiation and at night. A sensitivity analysis illustrated that for both summer and winter operation, the size, tilt angle and absorptivity of the roof collector greatly effected the efficiency and mass flow rates of the system, agreeing well with other literature. These results prove that this low cost solar chimney cooling design was feasible to enhance natural ventilation mainly during hot summer conditions with high solar radiation. Compared to a loft with only conventional roof insulation, the chimney did not perform effectively during the winter to heat the loft up, meaning that winter operation for this specific design is not feasible. Possible improvements to the design include using construction materials with higher thermal capacities to retain heat energy and ensure continued operation during periods of low solar radiation, as well as using selective absorber coatings on the collector surface. It is recommended that further work on the project include the integration of these improvements into the present design and to use the findings obtained from the sensitivity analysis to improve system efficiencies. CFD analysis of the test-rig will be insightful as an additional means to validate and compare with the analytical and experimental data obtained in this report. With the continuation of these studies, this low-cost solar chimney design can be optimised, validated on a commercial scale and built into existing and new housing developments. Incorporating such a passive thermal device will aid homeowners in air regulation and thermal comfort of their living space as well as saving on energy requirements.
- ItemThe development of a biofuels engine testing facility(Stellenbosch : Stellenbosch University, 2008-12) Palmer, Duncan; Lorenzen, L.; Van der Spuy, Johan; Stellenbosch University. Faculty of Engineering. Dept. of Process Engineering.; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.This report covers the development of a biofuels engine testing facility at Stellenbosch University. The motivation for the project was three fold: a) a desire to establish biofuels and engine testing know-how; b) to test the performance characteristics of biodiesel; and c) make a facility available for future research. The two main conclusions drawn from the initial test results are: 1) the test cell is fully operational and 2) biodiesel can be substituted for mineral diesel. To the author’s knowledge this is the first biofuel specific engine testing facility in South Africa. After a literature study the test cell was realised in three phases. • Firstly, the hardware layout was designed and the necessary equipment was sourced from respectable suppliers including the judicious use of good qaulity second hand components to minimize capital cost. • The test cell was then instrumented with new sensors. Key components among these are the K-type thermocouples, barometric pressure, humidity, oil pressure and an Allen-Bradley programmable controller to serve as a data acquisition card. Two software programs were chosen, ETA for the control of the test cell and RSLogix to program the programmable logic controller (PLC). • The complete system was then integrated, debugged and validated. The design methods and procedures have been documented throughout the project along with user manuals to facilitate further research. To determine the difference in combustion parameters between biodiesel and mineral diesel an autonomous power curve test was conducted. This revealed little difference in terms of performance between the two fuels, although biodiesel had on average a marginal 0.4% decrease in power over mineral diesel. The fuel consumption for pure biodiesel was found to be higher, which is as expected as it is has a lower calorific value than mineral diesel. As a final validation, an energy balance was conducted. Here the calculated calorific value of biodiesel was compared to the results from a calorie bomb test, and the two results were found to be within 2% of each of other.
- ItemAn economic evaluation of a wind power electricity generating farm in South Africa(2011-12) Menzies, Greig Hamilton; Hosking, S. G.; Sale, M. C.; Stellenbosch University. Faculty of Engineering. Centre for Renewable and Sustainable Energy StudiesENGLISH ABSTRACT: Renewable energy technology has received much attention over recent years. The depletion of known fossil fuel reserves and the volatility of international fuel prices require that society looks beyond the current coal-dominated electricity generation methods. Wind energy is an internationally well-established technology with large markets in major countries around the world, such as the USA and Germany. South Africa has the potential to generate large amounts of electricity from the wind because of the strength of the country’s wind resource. The long coast line and open areas are ideal for the exploitation of wind energy.
- ItemEvaluation of different process designs for biobutanol production from sugarcane molasses(Stellenbosch : Stellenbosch University, 2010-03) Van der Merwe, Abraham Blignault; Knoetze, J. H.; Gorgens, Johann F.; Stellenbosch University. Faculty of Engineering. Dept. of Process Engineering.ENGLISH ABSTRACT: Recently, improved technologies have been developed for the biobutanol fermentation process: higher butanol concentrations and productivities are achieved during fermentation, and separation and purification techniques are less energy intensive. This may result in an economically viable process when compared to the petrochemical pathway for butanol production. The objective of this study is to develop process models to compare different possible process designs for biobutanol production from sugarcane molasses. Some of the best improved strains, which include Clostridium acetobutylicum PCSIR-10 and Clostridium beijerinckii BA101, produce total solvent concentrations of up to 24 g/L. Among the novel technologies for fermentation and downstream processing, fedbatch fermentation with in situ product recovery by gas-stripping, followed by either liquid-liquid extraction or adsorption, appears to be the most promising techniques for current industrial application. Incorporating these technologies into a biorefinery concept will contribute toward the development of an economically viable process. In this study three process routes are developed. The first two process routes incorporate well established industrial technologies: Process Route 1 consist of batch fermentation and steam stripping distillation, while in Process Route 2, some of the distillation columns is replaced with a liquid-liquid extraction column. The third process route incorporates fed-batch fermentation and gas-stripping, an unproven technology on industrial scale. Process modelling in ASPEN PLUS® and economic analyses in ASPEN Icarus® are performed to determine the economic feasibility of these biobutanol production process designs. Process Route 3 proved to be the only profitable design in current economic conditions. For the latter process, the first order estimate of the total project capital cost is $187 345 000.00 (IRR: 35.96%). Improved fermentation strains currently available are not sufficient to attain a profitable process design without implementation of advanced processing techniques. Gas stripping is shown to be the single most effective process step (of those evaluated in this study) which can be employed on an industrial scale to improve process economics of biobutanol production.
- ItemExplore, design and act for sustainability : a participatory planning approach for local energy sustainability(MDPI, 2020-01-23) Fouche, Elaine; Brent, Alan C.ENGLISH ABSTRACT: This paper focuses planning approach for local energy sustainability. The characteristics of a complex problem were reviewed to establish that the problem of sustainable energy at a local government level is complex. In order to better manage complex problems, the literature shows that soft operational research or problem-structuring methods need to be applied, and hence these methods were used as a starting point for developing a participatory planning approach. The requirements for a planning approach were elicited, namely that the approach must be participative and inclusive, holistic, simple and transparent. In addition, the approach must include the identification and assessment of risks as part of the deliberation process, the development of a realistic action plan must be attainable at the end of the stakeholder engagement, the approach must be dynamic, and should be formalised with clear institutional arrangements. A novel participatory approach, namely EDAS—to Explore, Design and Act for Sustainability—was then developed, applied, and evaluated as part of a case study with a local municipality in theWestern Cape Province of South Africa. The insights are relevant not only for local governments, but for any institution on a journey towards sustainability.
- ItemExploring the possibility of the insurance industry as a solar water heater driver in South Africa(Stellenbosch : University of Stellenbosch, 2011-03) Kritzinger, Karin; Sebitosi, A. B.; University of Stellenbosch. Faculty of Economic and Management Sciences. School of Public Leadership.ENGLISH ABSTRACT: South Africa is facing an energy crisis on two levels; the existing capacity to supply electricity is unable to support future growth in demand, and the electricity being produced comes mostly from coal-fired power stations with associated emission problems. The South African government has a target for renewable energy to service 23% of the country’s energy consumption by 2013. This could potentially be realised through achievement of another government target, the installation of one million Solar Water Heaters (SWHs). On a technical level, Solar Water Heaters (SWHs) represent a completely viable renewable energy alternative for South Africa. It is an established and proven technology which has the potential to have a big impact on the country’s electricity capacity problems. SWHs can be used in a variety of applications from industry to households. Most of the hot water in South African homes is heated by electric resistance heating in standard electric water heaters and there are no technical obstacles to replacing most of these with SWHs, thereby delivering a saving of up to 70% of the water heating energy bill. Water heating currently accounts for 40% of domestic electricity consumption within a residential sector that uses 20-30% of the national supply. At the macroscale, the roll out of SWH programmes is completely scalable. The benefits of SWH installation accrue to the consumer in the form of a financial saving in the long-term and to society in the form of reduced emissions. Awareness of the benefits is growing amongst the general public, commercial institutions and in government. Sales are starting to pick up due to, amongst other reasons, electricity price hikes and government subsidies for SWH installations offered through the national electricity supply company, Eskom. A national building regulation enforcing energy-efficient water heating in new buildings has been drafted and is expected to be in place by mid 2011. The rate of change from electric to solar water heaters remains disappointingly slow, however. The SWH industry in South Africa accounts for less than 10% of total hot water solutions sold. This study sought to establish the opportunities as well as possible barriers for the creation of SWH programmes within the insurance sector. Close to 50% of all standard electric water heaters installed in South Africa are procured and installed via the insurance industry due to the failure of units that have endured beyond the manufacturer’s guarantee period. This presents an opportunity for interventions that encourage policyholders to change to SWHs. Such interventions, if successful, would dramatically speed up the roll out of SWHs in South Africa. In addition the study sought to determine the barriers to the uptake of SWHs by policyholders in the case of the two insurance companies that currently have SWH programmes in operation. Data was collected through interviews with representatives in the insurance industry and a range of SWH industry stakeholders and consumers. The literature review focused on SWH policies and regulations and corporate and marketing theories. The material on transition in socio-technological systems proved especially useful in understanding the complex dynamics of the study topic. The conclusion drawn from the research is that the South African insurance industry has the capacity and opportunity to drive the penetration of SWH technology. The opportunity is, however not being exploited to anywhere near its potential. The entire system is geared towards providing a particular ‘business-as-usual’ solution. Analysis conducted in this study confirms that the system is in a “locked-in” state and extremely resistant to change. If the opportunity is to be acted on, to supplant the dominant technology for water heating installed by the insurance industry with what is currently a niche technology (SWHs), an external landscape shock is almost certainly needed. This shock to the system could be aided by interventions that target a change in the current system’s logic. The study provides some suggestions in this regard.
- ItemFeasibility study for wind power at SAB Newlands(Stellenbosch : University of Stellenbosch, 2009-12) Brosius, Walter; Von Backstrom, T. W.; Van Niekerk, W.; University of Stellenbosch. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.This paper describes a MEng thesis project for a MEng in Renewable Energy Systems program at the Centre for Renewable Energy Studies at the University of Stellenbosch, South Africa. The aim of this paper was to offer to SAB (South African Breweries), in Cape Town, a feasibility study for the possibilities of the usage of wind energy on site. The small scale wind power technology has a long history and has been in South Africa for more than a hundred years in the form of water pump wind mills. All wind mills have an absolute maximum power output defined by the Betz limit. The choice of a wind turbine depends not only on this, but also on the wind speed distribution, the power curve, the location and financing. The small scale turbines have many different design which are predominantly grouped in horizontal axis (HAWT) and vertical axis (VAWT) machines. The choice of turbine for SAB depends on the available wind energy, the available budget, the available space and the application. The aim of the measurements on site was threefold; find a correlation with existing weather stations in the area like at Cape Town International Airport, propose a turbine for SAB’s budget and research the possibility for installing the turbine on one of the buildings. This is also known as building integrated wind turbines. Wind speeds can increase over buildings due to venturi effects and it could therefore be viable to locate these acceleration zones and install a turbine there. The data analysis shows that the wind above the brewery is very well correlated with the wind at the airport. We can therefore use the average speed values of this station to predict average power production. This leads to the proposal of a 1kW or 3kW turbine from a South African manufacturer: Kestrel. Building integration is however not a good idea. The wind is too turbulent and can therefore not be used. This is mainly caused by the fact that the surroundings of the brewery are too high and irregularly shaped. This makes it difficult for the wind to “lower” in between the buildings and accelerate. The wind turbine for SAB is proposed to be installed on the highest point of the roof and based on the neighbouring average wind speed values. The wind turbine should be connected directly to the brewery’s grid with an inverter and would then solely function as an energy saver. Another important aspect is the promotional value in the energy efficiency strategy of SAB.
- ItemA finite element based optimisation tool for electrical machines(Stellenbosch : University of Stellenbosch, 2011-03) Gerber, Stiaan; Strauss, J. M.; Randewijk, P. J.; University of Stellenbosch. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.ENGLISH ABSTRACT: Knowledge of the magnetic fields in the domain of electrical machines is required in order to model machines accurately. It is difficult to solve these fields analytically because of the complex geometries of electrical machines and the non-linear characteristics of the materials used to build them. Thus, finite element analysis, which can be used to solve the magnetic field accurately, plays an important part in the design of electrical machines. When designing electrical machines, the task of finding an optimal design is not simple because the performance of the machine has a non-linear dependence on many variables. In these circumstances, numerical optimisation using finite element analysis is the most powerful method of finding optimal designs. In this thesis, the work of improving an existing finite element simulation package, formerly known as the Cambridge package among its users, and the use of this package in the optimisation of electrical machine designs, is presented. The work involved restructuring the original package, expanding its capabilities and coupling it to numerical optimisers. The developed finite element package has been dubbed SEMFEM: the Stellenbosch Electrical Machines Finite Element Method. The Cambridge package employed the air-gap element method, first proposed by Razek et. al. [2], to solve the magnetic field for different positions of the moving component in a time-stepped finite element simulation. Because many new machine topologies have more than one air-gap, the ability to model machines with multiple air-gaps is important. The Cambridge package was not capable of this, but during the course of this work, the ability to model machines with multiple air-gaps using the air-gap element method was implemented. Many linear electrical machines have tubular, axisymmetric topologies. The functionality to simulate these machines was newly implemented because the original program was not capable of analysing these machines. Amongst other things, this involved the derivation of the coefficients of an axisymmetric air-gap element’s stiffness matrix. This derivation, along with the original air-gap element derived by Razek et. al. [2] and the extension of the method to the Cartesian coordinate system by Wang et. al. [29, 30], completes the derivation of all two-dimensional air-gap elements. In order to speed the numerical optimisation process, which is computationally expensive, parallelisation was introduced in two areas: at the level of the finite element simulation and at the level of the optimisation program. The final product is a more powerful, more usable package, geared for the optimisation of electrical machines.
- ItemGuidelines for energy management in the South African wine industry(Energy Research Centre, 2016-11) Brent, Alan C.; Silinga, Cebo; Sanetra, NadiaPressure is mounting on the wine industry to consider energy management interventions to, inter alia, reduce energy consumption – to be more competitive, become more self-reliant, and to reduce the carbon footprint of the sector. This paper then summarises the process that was undertaken to develop an appropriate energy management guideline for the South African wine industry. It is based on a literature analysis of best practices elsewhere, and a number of case studies across different sizes of winery operations in South Africa. The positive outcomes from energy management interventions at these cases are demonstrated, but a number of challenges are also highlighted. Recommendations are made accordingly.
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