Scielo RSS <![CDATA[Journal of Energy in Southern Africa]]> http://www.scielo.org.za/rss.php?pid=1021-447X20200003&lang=en vol. 31 num. 3 lang. en <![CDATA[SciELO Logo]]> http://www.scielo.org.za/img/en/fbpelogp.gif http://www.scielo.org.za <![CDATA[<b>The adoption of energy efficiency and a policy framework for Zimbabwe</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2020000300001&lng=en&nrm=iso&tlng=en Recent policy discussions on energy use in Zimbabwe sparked interest in the economic case for energy efficiency, suggesting the need to investigate the relevant costs and benefits. This paper investigated the potential of energy efficiency in manufacturing industries in Zimbabwe. Data collection was done using questionnaires, walk-through audits and semi-structured interviews. The data set was then analysed using regression analysis. The results show that there would be significant potential energy saving in Zimbabwe through adopting various energy efficiency programmes. The main energy efficiency barriers identified were: poorly structured electricity tariffs; risk of production disruption; resistance of operational staff to a changed working style; lack of coordination between company divisions; lack of information on energy efficiency programmes; and lack of support from senior management on issues that relate to energy efficiency. A straightforward energy efficiency policy framework is proposed, and three main players identified, namely government, energy regulator, and research institutions. <![CDATA[<b>Intelligent techniques, harmonically coupled and SARIMA models in forecasting solar radiation data: A hybridisation approach</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2020000300002&lng=en&nrm=iso&tlng=en The unsteady and intermittent feature (mainly due to atmospheric mechanisms and diurnal cycles) of solar energy resource is often a stumbling block, due to its unpredictable nature, to receiving high-intensity levels of solar radiation at ground level. Hence, there has been a growing demand for accurate solar irradiance forecasts that properly explain the mixture of deterministic and stochastic characteristic (which may be linear or nonlinear) in which solar radiation presents itself on the earth's surface. The seasonal autoregressive integrated moving average (SARIMA) models are popular for accurately modelling linearity, whilst the neural networks effectively capture the aspect of nonlinearity embedded in solar radiation data at ground level. This comparative study couples sinusoidal predictors at specified harmonic frequencies with SARIMA models, neural network autoregression (NNAR) models and the hybrid (SARIMA-NNAR) models to form the respective harmonically coupled models, namely, HCSARIMA models, HCNNAR models and HCSARIMA-NNAR models, with the sinusoidal predictor function, SARIMA, and NNAR parts capturing the deterministic, linear and nonlinear components, respectively. These models are used to forecast 10-minutely and 60-minutely averaged global horizontal irradiance data series obtained from the RVD Richtersveld solar radiometric station in the Northern Cape, South Africa. The forecasting accuracy of the three above-mentioned models is undertaken based on the relative mean square error, mean absolute error and mean absolute percentage error. The HCNNAR model and HCSARIMA-NNAR model gave more accurate forecasting results for 60-minutely and 10-minutely data, respectively.HIGHLIGHTS: • HCSARIMA models were outperformed by both HCNNAR models and HCSARIMA-NNAR models in the forecasting arena. • HCNNAR models were most appropriate for forecasting larger time scales (i.e. 60-minutely). • HCSARIMA-NNAR models were most appropriate for forecasting smaller time scales (i.e. 10-minutely). • Models fitted on the January data series performed better than those fitted on the June data series. <![CDATA[<b>Design of an electrostatic precipitator for a novel bituminous coal-fired circulating fluidised bed combustion power plant in Namibia</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2020000300003&lng=en&nrm=iso&tlng=en Coal-fired power plants utilising fluidised bed technologies emit copious amounts of fly-ash, which is harmful to people owing to its particulate nature. A planned 300 MW power plant will have an electrostatic precipitator (ESP) for fly-ash emissions control, in line with power generation industry best practices. This ESP should meet a fly-ash emission limit value < 50 mg/Nm³. This paper details the design process and resultant technical specifications of a cold-side, single-stage, and plate-wire dry ESP designed for the power plant. The ESP will consist of twin-chambers with quadruple-fields (2 x 4 x 315 m³) and octonary bus-sections independently energised by individual high-frequency three-phase switched integrated rectifiers (70 kV, 800 mA) to maximise ionisation. Dynamically balanced, single-impact, tumbling hammer rappers (857.5 rpm) will dislodge fly-ash from the collector plates into mass-flow wedge-shaped hoppers. A specific collection area (&gt; 56.9 m²/m³/s) and an ESP index (&gt; 709.2 (kV/cm)²m²/m³/s) should guarantee a collection efficiency ( r\ &gt; 99.5 %) and the specified emission limit value at 100 % boiler capacity and normal operating conditions (gas velocity < 2.4 m/s; gas temperature < 137 °C; fly-ash loading < 10 000 kg/Nm³; resistivity < 10(10) (Ω -cm). The design was successfully verified in principle using the validation square method, in conjunction with the leading comparable historical case studies approach. It is recommended to simulate ESP designs using suitable programs like Comsol Multiphysics and construct a pilot plant before attempting scaled-up construction and commissioning. HIGHLIGHTS: • A cold-side, single-stage plate-wire dry ESP system designed. • Theoretical collection efficiency in excess of 99.5%. • High-frequency, three-phase switched integrated rectifiers to be used for ionisation. <![CDATA[<b>Russian energy projects in South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2020000300004&lng=en&nrm=iso&tlng=en From early 2019, South Africa and Russia have planned to increase their energy trade. Russia can become one of the world's five largest energy exporters. This study examines of the cost of a kilowatt of electricity generated by coal power projects in South Africa and compares nuclear electricity with other types of green energy. This method must help to improve the management decision-making process in South Africa for energy exporta. Reasons for this persistence include the marketing strategies of Russian companies for seeking new markets in industrialised and postindustrial countries where, due to intensive competition, sales of Russian high-tech products are often unsuccessful. Renewable energy gives a chance to potentially reduce poverty in South Africa. The study concludes that imported crude oil is more suited to the needs of the refining industry of South Africa. The consumption for this type of energy in areas not concerning industry is insignificant and its increase is unlikely to be observed in the future.HIGHLIGHTS: • Nuclear energy is popular energy source in South Africa now. • Provision of sustainable energy services helps to find the sources for economic growth. • Renewable energy technologies have opportunity for reduce nuclear production in South Africa. • Bio-energy can become the main source of energy in South Africa.