Scielo RSS <![CDATA[Journal of Energy in Southern Africa]]> http://www.scielo.org.za/rss.php?pid=1021-447X20150002&lang=es vol. 26 num. 2 lang. es <![CDATA[SciELO Logo]]> http://www.scielo.org.za/img/en/fbpelogp.gif http://www.scielo.org.za <![CDATA[<b>Suppressed demand in the clean development mechanism: Conceptual and practical issues</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2015000200001&lng=es&nrm=iso&tlng=es One of the challenges of applying greenhouse gas emission accounting approaches in poor communities is that the current consumption of many household services (e.g. heating and cooking, lighting and potable water) may not reflect the real demand for those services. This could be the result of lack of infrastructure, lack of natural resources or poverty, particularly the high costs of these services relative to household incomes. The situation of 'suppressed demand' creates a problem for setting emissions baselines against which to compare project performance, and has negatively affected CDM project development in Africa, Least Developed Countries and other regions with very few CDM projects. Ironically, although new large-scale power plants do not have to show that they actually displace other plants (existing or new), many small-scale energy projects can only claim credit for displacing historical (very low level) emissions from households. While the CDM rules are evolving to consider suppressed demand, much more can be done to catalyse investment in these types of climate change mitigation projects in poor communities. Furthermore, making progress will require significant expert and stakeholder input to ensure that simplification is balanced with maintaining overall environmental integrity. <![CDATA[<b>Proposal for improved nuclear fuel utilisation and economic performance by utilising thorium</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2015000200002&lng=es&nrm=iso&tlng=es A systematic and strategic nuclear power reactor deployment roadmap has been developed for South Africa within the national strategic plan, utilizing thorium-based fuel. The roadmap was developed through analysis of economical, strategic and historical aspects. The accumulated advantages of thorium-based fuels are summarized, which could form the initiative to implement thorium-based nuclear fuels in South Africa. A timeline (which forms the basis of the roadmap) was constructed and consists of three different phases. Phase 1 starts in 2015 and extends to 2030. Phase 2 starts in 2031 and ends in 2044 whilst Phase 3 is from 2045 to 2060. Each phase is discussed with regard to construction, implementation and research activities. This roadmap starts at current pressurized water reactors (PWRs) and advances to future reactor technologies, using an evolutionary approach. In addition to the results reported in this paper, the economic advantages to introducing thorium as a fertile component in PWR fuels as compared to once-through conventional uranium-only cycles is explored (Du Toit & Cilliers, 2014). The economic evaluation compares uranium fuel to thorium-uranium fuel in terms of the fuel cycle costs, reactor downtime costs due to refuelling and income derived from electricity sales. <![CDATA[<b>Energy supply in Malawi: Options and issues</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2015000200003&lng=es&nrm=iso&tlng=es Inadequate energy supply is one of the major problems confronting Malawi and limiting its social, economic and industrial development. This paper reviews the current status of energy supply and demand in Malawi; examines the major sources of energy, current exploitation status and their potential contribution to the electricity supply of the country; discusses key issues facing the energy sector; and identifies broad strategies to be implemented to tackle the energy supply challenges. Using secondary data for its critical analysis, the paper also presents modelling of long-term energy demand forecast in the economic sectors of Malawi using the Model for Analysis of Energy Demand (MAED) for a study period from 2008-2030. Three scenarios namely reference (REF), moderate growth (MGS) and accelerated growth (AGS) were formulated to simulate possible future long-term energy demand based on socio-economic and technological development with the base year of 2008. Results from all scenarios suggest an increased energy demand in consuming sectors with biomass being a dominant energy form in household and industry sectors in the study period. Forecast results reveal that energy demand will increase at an annual growth rate of 1.2% and reach 5160 ktoe in 2030 under REF scenario. The growth rates for MGS and AGS are projected at 1.5% each reaching 4639 ktoe and 5974 ktoe in 2030, respectively. The final electricity demand of about 105 ktoe in the base year will grow annually at average rates of 13.8%, 15.3% and 12.6% for REF, AGS and MGS, respectively. Over the study period 2008-2030 the annual electricity per capita will increase from about 111 kWh to 1062, 1418 and 844 kWh for the REF, AGS and MGS, respectively. The final energy intensity will decrease continuously from about 13.71 kWh/US$ in the base year to 3.88 kWh/US$, 2.98 kWh/US$ and 5.27 kWh/US$ for the REF, AGS and MGS, respectively in the year 2030. In conclusion, the paper outlines strategies that could be utilized to ensure adequate supply of modern energy which is a key ingredient for achieving sustainable social and economic growth. <![CDATA[<b>Bio-oil yield potential of some tropical woody biomass</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2015000200004&lng=es&nrm=iso&tlng=es Six tropical biomass samples namely: Ogbono wood (Irvingia wombolu), Mango wood (Mangifera indica), Neem wood (Azadiracta indica), Ogbono shell (Irvingia wombolu), Ogirisi wood (Neubouldia laevis) and Tropical Almond wood (Terminalia cat-appa) were pyrolyzed in a bench scale screw reactor at 450oC. The physicochemical properties of the samples were determined prior to the pyrolysis experiments. The bio-oil and bio-char produced were similarly characterized using standard procedures established by American Standard and Test Methods (ASTM). The highest bio-oil yield of 66 wt% and least bio-oil yield of 53 wt% were obtained from Neem wood and Tropical Almond wood respectively. The characterization results of the products show that even though the moisture content of the bio-oil was quite higher than those of the original feedstock, their higher heating values were higher than those of the parent feedstock. Both characterization results show that the feedstock and their fast pyrolysis products are good materials for bioenergy production. The Gas Chromatography Mass Spectroscopy (GC-MS) analysis of the bio-oil shows the presence of useful chemicals such as phenols and levoglucosan, which could be harnessed for industrial applications. <![CDATA[<b>Using participatory GIS to examine social perception towards proposed wind energy landscapes</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2015000200005&lng=es&nrm=iso&tlng=es Thirteen onshore wind farm projects, totalling approximately 700 wind turbines, are proposed for the West Coast Region (WCR) of the Western Cape Province in South Africa. Wind energy exploitation possesses the ability to transform what can be classified as natural landscapes into landscapes of power, making the type of landscape on which wind turbines are deployed a prominent factor in its social acceptance or rejection. This paper examines the landscape aesthetics and land use interference of proposed wind farms in the WCR of South Africa through determining if social acceptance or rejection of proposed wind farms is dependent on the residents and visitors scenic and land use valuation of the natural landscape. The results indicate that the visual intrusion of wind turbines is the impact that respondents are least concerned with contrasting with the findings of international literature and further reasons for this anomaly are interrogated against the background of South Africa's dire electricity needs. The paper concludes that visual impact assessments alone are not sufficient for evaluating landscapes and this paper recommends that participatory geographic information systems (PGIS) be used in addition to existing wind energy landscape assessments. <![CDATA[<b>The optical design and performance of a concentrator photovoltaic module</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2015000200006&lng=es&nrm=iso&tlng=es Concentration photovoltaic (CPV) modules promise a more efficient, higher power output than traditional photovoltaic modules. This is achieved by concentrating sunlight onto a small 1 cm2 concentrator triple-junction (CTJ) InGaP/InGaAs/Ge cell by using high quality precision optics. In order to achieve high energy performance and reliability, well thought-out design decisions must be made in the development of a CPV module. This paper investigates the design of two CPV modules (Module I and II), which are based on the Sandia III Baseline Fresnel module. The investigation concentrated on the effect of the optimization of the optical design on the electrical performance characteristics of CTJ cells with good thermal dissipation. The best performance achieved by Module I was at 336 times operational concentration (Xo), which produced a Pmax of 10.29 W per cell, with cell and module efficiencies of 39% and 24%, respectively. In the development of the second module (Module II) pre-deployment criteria such as the CTJ cell and system components characteristics was used to eliminate faulty components from the system what was observed in Module I. Cell units that were optimized in Module II showed no form of degradation in their Current-Voltage (I-V) characteristics. The cell unit operating under optical misalignment showed a progressive degradation with long term operation in the field. <![CDATA[<b>Energy improvement in induction furnace using foaming slag with variation of carbon injection</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2015000200007&lng=es&nrm=iso&tlng=es Energy efficiency is nowadays one of the biggest concerns worldwide. It has become one of the critical matters to any country and industry particularly in South Africa. Because of the complexities and challenges found in industries and especially in foundry, many strategies have been established to measure and regulate more efficiently the energy. Many studies have been conducted in steelmaking process and electrical arc furnace using foaming slag to reduce energy consumption. As such, in this case study, the experiment will be conducted in a small foundry metal casting laboratory using an Induction Furnace (IF), which will reduce energy usage by using the foaming slag and as well pointing out the importance and the impact of carbon rate change on the foaming creation. After experiments all results show that the melting time can be reduced from 42min to 35 min, which is 20% time saving, the electrical energy consumption also has been reduced from 13.93kWh to 10kWh which is 39.3% saving. On the other hand, the foaming slag optimum height was reached at 1 cm. Therefore, a simple modelling has been designed and calculations have been made on heat transfer at the surface opening of the Induction Furnace and temperature loss has been reduced from 878°C to 870°C, with heat transfer loss reduced from 27.99kW to 26.38kW which was 6.10% of energy saving. <![CDATA[<b>Prediction of diesel engine performance, emissions and cylinder pressure obtained using Bioethanol-biodiesel-diesel fuel blends through an artificial neural network</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2015000200008&lng=es&nrm=iso&tlng=es The changes in the performance, emission and combustion characteristics of bioethanol-safflower biodiesel and diesel fuel blends used in a common rail diesel engine were investigated in this experimental study. E20B20D60 (20% bioethanol, 20% biodiesel, 60% diesel fuel by volume), E30B20D50, E50B20D30 and diesel fuel (D) were used as fuel. Engine power, torque, brake specific fuel consumption, NOx and cylinder inner pressure values were measured during the experiment. With the help of the obtained experimental data, an artificial neural network was created in MATLAB 2013a software by using back-propagation algorithm. Using the experimental data, predictions were made in the created artificial neural network. As a result of the study, the correlation coefficient was found as 0.98. In conclusion, it was seen that artificial neural networks approach could be used for predicting performance and emission values in internal combustion engines. <![CDATA[<b>Exhaust gas treatment for reducing cold start emissions of a motorcycle engine fuelled with gasoline-ethanol blends</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2015000200009&lng=es&nrm=iso&tlng=es In countries like India, transportation by a two wheeled motorcycle is very common owing to affordable cost, easy handling and traffic congestion. Most of these bikes use single cylinder air cooled four-stroke spark ignition (SI) engines of displacement volume ranging from 100 cm³ to 250 cm³. CO and HC emissions from such engines when started after a minimum stop-time of 12 hours or more (cold-start emissions) are higher than warmed-up emissions. In the present study, a 150 cm³ single cylinder air cooled SI engine was tested for cold start emissions and exhaust gas temperature. Different gasoline-ethanol blends (E0 to E20) were used as fuel expecting better oxidation of HC and CO emissions with additional oxygen present in ethanol. The effect of glow plug assisted exhaust gas ignition (EGI) and use of catalytic converter on cold start emissions were studied separately using the same blends. Results show that with gasoline-ethanol blends, cold start CO and HC emissions were less than that with neat gasoline. And at an ambient temperature of 30±1°C, highest emission reductions were observed with E10. EGI without a catalytic converter had no significant effect on emissions except increasing the exhaust gas temperature. The catalytic converter was found to be active only after 120 seconds in converting cold start CO, HC and NOx. Use of a catalytic converter proves to be a better option than EGI in controlling cold start emissions with neat gasoline or gasoline-ethanol blends. <![CDATA[<b>Building power control and comfort management using genetic programming and fuzzy logic</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2015000200010&lng=es&nrm=iso&tlng=es In the last couple of years, energy management in the building environment has been a topic of interest to the research community. A number of renowned methods exist in the literature for energy management in buildings, but the trade-off between occupants comfort level and energy consumption is still a major challenge and needs more attention. In this paper, we propose a power control model for comfort and energy saving, using a fuzzy controller and genetic programming (GP). Our focus is to increase the occupants' comfort index and to minimize the energy consumption simultaneously. First, we implemented a Genetic Algorithm (GA) to optimize the environmental parameters. Second, we control the environment using fuzzy logic and third, we predict the consumed power using GP. The environmental and comfort parameters considered are temperature, illumination and air quality. At the end of the work we compare the power consumption results with and without prediction. The results confirmed the effectiveness of the proposed technique in getting the solution for the above mentioned problem. <![CDATA[<b>Differential power algorithm based maximum power point tracking for a standalone solar PV system</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2015000200011&lng=es&nrm=iso&tlng=es We report on an improved maximum power point tracking (MPPT) system based on a differential power algorithm. In the proposed algorithm, which is a modified form of a perturb and observe (P&O) algorithm, differential powers, as well as voltages at different time, are compared. The proposed algorithm has been implemented with a highly efficient boost converter, in which duty cycle of a switch is varied in such a way, that the power reaches a maximum at any instant of the day, irrespective of the environmental conditions. The improved MPPT is able to reduce the number of oscillations and tracking time significantly before reaching the maximum power point (MPP). The simulated I-V and P-V characteristic curves (individual and combined) of a solar PV module were generated in MATLAB. <![CDATA[<b>Thermodynamic analysis of a direct expansion solar assisted heat pump water heater</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2015000200012&lng=es&nrm=iso&tlng=es In this paper, the thermodynamic performance of a direct expansion solar assisted heat pump (DX-SAHP), which is used to heat domestic water from 20°C to 45°C, is theoretically investigated. The system includes a 3m² single-cover flat plate solar collector, 0.150m³ water tank and 70m tube immersed in the water tank as a condenser. The effect of various parameters such as radiation on the collector surface, compressor speed and the ambient temperature on the coefficient of performance (COP) are calculated. Results show that obtained COP is considerably more than that of a conventional heat pump water heater when radiation on the collector is high. Also, increasing collector area and reducing compressor speed enhance COP. The same occurs when the ambient temperature increases. For instance, at an ambient temperature of 15°C and 450 w/m² irradiation on collector surface, the calculated COP was 6.37. <![CDATA[<b>Coherence and time-frequency analysis of impulse voltage and current measurements</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2015000200013&lng=es&nrm=iso&tlng=es The aim of this paper is to point out the advantages of the use of the time-frequency analysis in the digital processing of waveforms recorded in high voltage impulse tests. Impulse voltage tests are essential to inspect and test insulation integrity of high voltage apparatus. On the other hand, generated impulse currents are used for different test applications such as investigation of high current effects, electromagnetic interference (EMI) testing, etc. Obtained voltage and current waveforms usually have some sort of interferences originated from the different sources. These interferences have to be removed from the original impulse data in order to evaluate the waveform characteristics precisely. When the interference level is high enough, it might not be possible to distinguish signal parameters from the recorded data. Conventional filtering methods cannot be useful for some interference like white noise. In that case, time-frequency filtering methods might be necessary. In this study, the wavelet analysis, which is a powerful time-frequency signal processing tool, is used to recognize the noise of impulse current and voltage data. Thus, the noise sources can be determined by short time Fourier Transform, and a coherence approach is used to determine the bandwidth of noises. <![CDATA[<b>The determination of short circuits and grounding faults in electric power systems using time-frequency analysis</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2015000200014&lng=es&nrm=iso&tlng=es In order to ensure that electrical energy reaches consumers uninterrupted, researchers constantly try to improve power transmission lines. To realize this improvement, probable faults should be analysed through every known method, and new methods should also be implemented. In this study, firstly, the Keban power transmission line located in the Eastern Anatolia region of Turkey was modelled. After that, probable short circuit scenarios were applied on the model, and the short circuit faults in the scenarios were analysed by using the Fourier analysis. The Fourier analysis is a mathematical method that is used as an effective way to determine the sudden changes in the frequency and time band. The study was successful in determining phase and grounding faults through the analyses of the scenarios using Fourier analysis. The fact that the mathematical method was applied on the probable scenarios on a physical model increases the importance of the study. <![CDATA[<b>Erratum</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2015000200015&lng=es&nrm=iso&tlng=es In order to ensure that electrical energy reaches consumers uninterrupted, researchers constantly try to improve power transmission lines. To realize this improvement, probable faults should be analysed through every known method, and new methods should also be implemented. In this study, firstly, the Keban power transmission line located in the Eastern Anatolia region of Turkey was modelled. After that, probable short circuit scenarios were applied on the model, and the short circuit faults in the scenarios were analysed by using the Fourier analysis. The Fourier analysis is a mathematical method that is used as an effective way to determine the sudden changes in the frequency and time band. The study was successful in determining phase and grounding faults through the analyses of the scenarios using Fourier analysis. The fact that the mathematical method was applied on the probable scenarios on a physical model increases the importance of the study.