Scielo RSS <![CDATA[Journal of Energy in Southern Africa]]> http://www.scielo.org.za/rss.php?pid=1021-447X20170002&lang=pt vol. 28 num. 2 lang. pt <![CDATA[SciELO Logo]]> http://www.scielo.org.za/img/en/fbpelogp.gif http://www.scielo.org.za <![CDATA[<b>Potential for domestic biogas as household energy supply in South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2017000200001&lng=pt&nrm=iso&tlng=pt Biogas is a clean and renewable form of energy accessible to low-income households through anaerobic digestion of readily available organic waste. The objectives of this desktop study were to investigate the feasibility of biogas use for substitution of presently used solid fuels in rural and peri-urban households, the subsequent health co-benefits, and the constraints to adoption of domestic biogas technology in South Africa. The energy demand of low-income South African households for cooking with fuelwood was found to be 27 MJ/day and the total energy demand 68 MJ/day. This is equivalent to 2 500 L/day/household of biogas for cooking and 6 250 L/day/household of biogas for complete substitution of conventional domestic fuels. Complete substitution of fuelwood used for cooking and household fuelwood use with biogas can result in the avoidance of 43% and 85.4% respectively of total disability adjusted life-years lost (702 790) and mortalities (22 365) from indoor smoke as a consequence of solid fuel use. Approximately 625 000 households in South Africa can potentially benefit from bio-digester fed with cattle and pig waste, on the basis of livestock numbers. It is infeasible tc operate a domestic bio-digester fed solely with human waste, chicken waste and food waste because of insufficient feedstock. Non-sewerec households with access to on- and off-site wate supply generate sufficient greywater for feeding a domestic bio-digester for cooking purposes. This is therefore, recommended over the use of drinking water. <![CDATA[<b>Legislation governing the implementation of small-scale hydropower projects for rural electrification in South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2017000200002&lng=pt&nrm=iso&tlng=pt The Department of Energy's 'new household electrification strategy' allows for any appropriate and affordable technology option to be applied towards achieving South Africa's non-grid electrification target of 300 000 households over the period 2014 to 2025. This paper describes the main legislative and regulatory framework governing the implementation of small-scale hydropower (SHP) projects in South Africa with the aim of attaining the objectives of the non-grid electrification component of the 'new household electrification strategy', and indicates that it is possible to implement such projects within South Africa's complex institutional architecture. The inclusion of run-of-river type small-scale hydropower projects for rural electrification in the 2016 updated General Authorisation eased the process of attaining regulatory compliance in terms the National Water Act. This implies that these types of SHP projects would only need to follow a registration process to obtain the required water use authorisation, and not a full water use licence application process. Highlights • Appropriate and affordable technology option applied towards achieving the non-grid electrification target in South Africa. • Small-scale hydropower applied as an appropriate energy solution. • Legislation and regulations governing the implementation of small-scale hydropower for non-grid electrification in South Africa. <![CDATA[<b>The impact of residential rooftop solar PV on municipal finances: An analysis of Stellenbosch</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2017000200003&lng=pt&nrm=iso&tlng=pt Electricity utilities throughout the world are responding to the increased uptake of rooftop solar photovoltaic (PV) in the household sector. Although the increase of decentralised solar PV is seen as progressive for sustainable development, it is not without financial implications for electricity utilities. There is a concern in South Africa that allowing rooftop solar PV connection to the grid will reduce electricity sales for local governments and thus their revenue streams from electricity. An investigation was carried out to examine the financial impact that increasing installations of grid-connected rooftop PV at a household level might have on local governments in South Africa. Stellenbosch Municipality was used as a case study, and two different approaches were used. The first considered the maximum grid capacity for distributed generation, as determined by the South African grid standards. The second was based on individual households that would gain the most financial benefit from investing in rooftop PV. The outcome indicated a financial reduction in total electricity revenue of 0.6-2.4% depending on the approach followed. A fixed monthly charge of about R363 would counter these potential financial loses, but entail a disincentive for households to invest in solar PV installations. <![CDATA[<b>Influence of coal properties on the performance of fixed-bed coal-burning braziers</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2017000200004&lng=pt&nrm=iso&tlng=pt Informal fixed-bed coal-burning braziers are used extensively in low-income communities of South Africa for space-heating and cooking needs. An investigation was carried out on the effects of coal moisture content and coal quality on the thermal and emissions performance of domestic coal-burning braziers in three field-procured braziers (with three different air ventilation rates), using the bottom-lit updraft (BLUD) and top-lit updraft (TLUD) ignition methods. Results showed that an increase in coal moisture content (from 2.4 wt.% to 8.6 wt.%) led to 18% and 30% decreases in fire-power when using the TLUD and BLUD methods, respectively. The combustion efficiency increased by 25% with an increase in moisture content. Measured carbon monoxide (CO) emission factors increased with an increase in moisture content, while carbon dioxide (CO2) emission factors remained unchanged. The use of A-grade coal resulted in a 49% increase in PM emissions compared with D-grade coal at high ventilation rates, despite no statistically significant differences (p > 0.05) in CO and CO2 emission factors produced between coal grades. <![CDATA[<b>Is the summer season losing potential for solar energy applications in South Africa?</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2017000200005&lng=pt&nrm=iso&tlng=pt Seasonal trends using in situ sunshine duration (SD) and satellite, incoming shortwave solar radiation (SIS) data for South Africa over a period up to six decades were investigated. Trend analysis was applied to SD data of 22 sunshine-recording stations from the South African Weather Service that cover the length and breadth of South Africa. Satellite application facility on climate monitoring provided the high-resolution derived SIS for the period 1983-2013. A number of stations show a statistically significant decreasing trend in SD in all four seasons on a seasonal scale. Declines (number of stations showing significant trend) in SD at 17(7), 8(3), 7(3) and 3(0) stations, were observed for summer, autumn, winter and spring, respectively. The SIS has also shown a decreasing trend over South Africa in most of the regions during the summer season followed by autumn. The results indicated a general tendency of decrease in incoming solar radiation mostly during summer which could be of some concern for solar energy applications. <![CDATA[<b>Solar resource classification in South Africa using a new index</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2017000200006&lng=pt&nrm=iso&tlng=pt This paper introduces a solar resource index that responds to site-specific sky conditions resulting from stochastic movement and evolution of clouds. The developed solar resource classification index called probability of persistence (POP D) had limited capabilities to distinguish persistent clear-sky conditions from persistent overcast-sky conditions. The metric proposed in this investigation, referred to as the solar utility index (SUI), seeks to extend the POPD index to a simple enough index that can singly discriminate different states of a solar resource. It gives a measure of the fractional time during which a solar resource exhibits predefined characteristics over a specific time period not exceeding the time interval between sunrise and sunset. These solar resource qualities, which are user-defined, measure: (1) the fluctuation characteristic of the solar resource magnitude, and (2) the solar resource diffuse and beam composition. Values of the indexes computed over daily time intervals of 7:00-17:00 apparent solar time were tested for their solar resource classification qualities. Five distinct classes using K-means clustering algorithm were identified for the solar radiation resource measured at eight stations in South Africa. The SUI was found to have superior solar resource discriminating and grouping abilities when compared with other indexes like POPD and fractal dimension. Highlights • Solar utility index, a new solar resource classification index was defined. • Five classes of the solar resource in South Africa were identified. • The five clusters showed reasonably homogeneous solar resource properties. <![CDATA[<b>Power calculation accuracy as a function of wind data resolution</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2017000200007&lng=pt&nrm=iso&tlng=pt Wind power calculations are usually based on average wind data taken over one-hour intervals. The effect of the wind data resolution on the statistical techniques used to calculate the probable power output (PPO) is commonly overlooked. This effect is analysed in this paper by iteratively calculating and comparing the PPO of a wind turbine using data, averaged over different periods, obtained from Wind Association of South Africa. The power is calculated using both Weibull representation and direct polynomial substitution techniques in order to compare and verify the results. The results indicate a fairly linear relationship between the resolution used and the PPO error incurred. These results raise an interest to examine the effects of a fine resolution on the data in terms of data dependence, which may violate the criteria for the majority of statistical tests and procedures.