Scielo RSS <![CDATA[Journal of Energy in Southern Africa]]> http://www.scielo.org.za/rss.php?pid=1021-447X20160002&lang=pt vol. 27 num. 2 lang. pt <![CDATA[SciELO Logo]]> http://www.scielo.org.za/img/en/fbpelogp.gif http://www.scielo.org.za <![CDATA[<b>A literature review on the potential of renewable electricity sources for mining operations in South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2016000200001&lng=pt&nrm=iso&tlng=pt The economic situation of mining corporations operating in South Africa has in recent years created considerable challenges in staying globally competitive. One reason for this is the increase in average electricity costs from 7% to 20% of total operational expenses since 2007. Forecasts for the next decade predict that this development will continue at similar rates. The reliability of Eskom has also decreased, with self-generation being increasingly considered. In addition, the South African government plans to launch a carbon tax in 2016, which will further add to the costs of current electricity sources. This paper investigates the potential of renewable electricity sources for mining operations in South Africa. It is based on an extensive literature analysis, which was conducted in the form of a conceptual review. The investigation of electricity usage patterns reveals that mining operations commonly have a relatively constant day and night consumption. One of the prerequisites for a suitable source is its ability to supply electricity constantly. Most renewable sources can therefore only be used in hybrid versions, owing to relatively high intermittencies, especially with electricity supply from solar photovoltaic and wind generation. Nevertheless, the levelised costs are substantially lower than diesel generators and are already similar to Eskom tariffs, whilst also lowering carbon emissions. The business case of self-generation is shown to be positive. An on-site project can be realised through a power purchase agreement or through own investments. <![CDATA[<b>Incorporating a three dimensional photovoltaic structure for optimum solar power generation - the effect of height</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2016000200002&lng=pt&nrm=iso&tlng=pt In a renewable energy system, incorporating three-dimensional technology in solar power generation takes advantage of the three-dimensional nature of the biosphere so that energy collection occurs in a volume, contrary to what is commonly obtained in planar or flat photovoltaic panel. Three-dimensional photovoltaic technologies are capable of generating more power from the same base area when compared to the conventional flat solar panels. This investigation examines methodologies for computation and analyses the effect of height per unit volume compared with a plain surface arrangement. The results show remarkable increase in the energy generated by the three-dimensional photovoltaic structure over the two-dimensional planar structures. <![CDATA[<b>Experimental investigation on heat extraction from a rock bed heat storage system for high temperature applications</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2016000200003&lng=pt&nrm=iso&tlng=pt Solar energy is available in an intermittent way, and integrating an energy storage system with solar energy collection devices may promote uninterrupted supply of energy in the absence of the availability of solar energy. It has been shown that heat can be stored using rocks packed in a bed, but limited work has been reported on heat extraction from a charged rockbed. This paper reports on the heat extraction from a charged rock bed. Discharging tests were performed under different air flow conditions and initial bed temperatures. Without the blower, the discharging rate is very slow. The discharging rate can be increased, and the cooking time controlled by adjusting the air speed through the rock-bed system. <![CDATA[<b>Modelling household electricity consumption in eThekwini municipality</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2016000200004&lng=pt&nrm=iso&tlng=pt South African municipalities are faced with the challenges of growing demand for services. This study models the energy consumption estimation practice within the Durban municipal area. It was found that an estimation technique that accounts for the seasonal and monthly effects, as well as residential type, predicts monthly individual household electricity consumption with minimum error. Models that were developed may be used to estimate electricity consumption for household billings within a municipality. <![CDATA[<b>Overview of predictive CSP spread prospects and its opportunities</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2016000200005&lng=pt&nrm=iso&tlng=pt An investigation was carried out to illustrate the prospects and challenges associated with implementation of concentrating solar power (CSP) with storage technology in South Africa. Various factors were examined that have an effect on the cost of CSP plants and offer an overall review of the opportunities CSP has for the country. This paper appeals the general idea that CSP is not cost effective enough and attempts to illustrate the feasibility of this technology in South Africa. <![CDATA[<b>Synthesis of zirconia-based solid acid nanoparticles for fuel cell application</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2016000200006&lng=pt&nrm=iso&tlng=pt Zirconia nanoparticles were prepared by the precipitation and ageing methods. The precipitation method was performed by adding ammonium solution to the aqueous solution of zirconium chloride at room temperature. The ageing method was performed by leaving the precipitate formed in the mother liquor in the glass beaker for 48 hours at ambient temperatures. The nanoparticles from both methods were further sulphated and phosphated to increase their acid sites. The materials prepared were characterised by X-ray diffraction (XRD), ther-mo-gravimetric analysis (TGA), Brunauer-Emmett-Teller (BET), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) methods. The XRD results showed that the nanoparticles prepared by the precipitation method contained mixed phases of tetragonal and monoclinic phases, whereas the nanoparticles prepared by ageing method had only tetragonal phase. The TEM results showed that phosphated and sulphated zirconia nanoparticles obtained from the ageing method had a smaller particle size (10-12 nm) than the nanoparticles of approximately 25-30 nm prepared by precipitation only. The BET results showed that the ZrO2nanoparticles surface area increased from 32 to 72 m²/g when aged. <![CDATA[<b>A life cycle assessment of e-books and printed books in South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2016000200007&lng=pt&nrm=iso&tlng=pt This paper presents the results of a study comparing the life cycle environmental impacts and cumulative energy demands of reading printed books (print system) with those of reading e-books from an Apple Air iPad (digital system), with a specific focus on production of books and use of both options in South Africa. The two systems were compared using the ReCiPe midpoint and cumulative energy demand methods. The findings, which are consistent with international findings, demonstrate that the print system has lower impacts than the digital system in the impact categories of freshwater eutrophication, freshwater ecotoxicity, marine ecotoxicity and metal depletion, whilst the digital system has lower impacts in the categories of climate change, ozone depletion, terrestrial acidification, marine eutrophication, human toxicity, photochemical oxidant formation, particulate matter formation, terrestrial ecotoxicity, ionising radiation, agricultural land occupation, urban land occupation, natural land transformation, water depletion and fossil depletion. The major processes contributing to energy demand and environmental impacts of the print system were paper production and printing. For the digital system the major contributing processes were the production of the iPad and e-book reading. Coal-based electricity and coal-mining-related activities featured prominently in both systems, affecting environmental impacts and energy demand of products and services in South Africa. A change in the electricity mix to be less coal-intensive reduced the impacts of both systems. Finally, the products demonstrate that relatively few additional readers result in printed books becoming preferable to e-books in almost all impact categories, suggesting the need to consider housing print books in libraries to reduce their relative environmental impacts.