Scielo RSS <![CDATA[Journal of Energy in Southern Africa]]> http://www.scielo.org.za/rss.php?pid=1021-447X20160001&lang=pt vol. 27 num. 1 lang. pt <![CDATA[SciELO Logo]]> http://www.scielo.org.za/img/en/fbpelogp.gif http://www.scielo.org.za <![CDATA[<b>Introduction to changes in JESA from 2016</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2016000100001&lng=pt&nrm=iso&tlng=pt <![CDATA[<b>Primary energy sources planning based on demand forecasting: The case of Turkey</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2016000100002&lng=pt&nrm=iso&tlng=pt Forecasting electricity consumption is a very important issue for governments and electricity related foundations of public sector. Recently, Grey Modelling (GM (1,1)) has been used to forecast electricity demand successfully. GM (1,1) is useful when the observed data is limited, and it does not require any preliminary information about the data distribution. However, the original form of GM (1,1) needs some improvements in order to use for time series, which exhibit seasonality. In this study, a grey forecasting model which is called SGM (1,1) is proposed to give the forecasting ability to the basic form of GM(1,1) in order to overcome seasonality issues. The proposed model is then used to forecast the monthly electricity demand of Turkey between 2015 and 2020. Obtained forecasting values were used to plan the primary energy sources of electricity production. The findings of the study may guide the planning of future plant investments and maintenance operations in Turkey. Moreover, the method can also be applied to predict seasonal electricity demand of any other country. <![CDATA[<b>Evaluation of the impact of distributed synchronous generation on the stochastic estimation of financial costs of voltage sags</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2016000100003&lng=pt&nrm=iso&tlng=pt Power system faults can cause voltage sags that, if they are less than voltage sensitivity threshold of equipment, can lead to interruption of supply and lead to incurring of financial losses. The impact of distributed generation (DG) on these financial losses is investigated in this work. Using the method of fault positions, a stochastic approach to determine voltage sag performance, profiles of magnitudes of remaining voltages at a monitoring point for faults occurring along lines in the network is developed. It follows that an expected number of critical voltage sags at a monitoring point is calculated and the expected cost of these sags is derived for various voltage sensitivity threshold limits. An illustrative study is carried out comparing the expected costs of voltage sags for a network without DG with a DG case, for various mixes of customers. It is shown that in the presence of DG, the expected costs of voltage sags are lesser for all voltage sensitivity criteria assumed and for all customer mixes. The study demonstrates that the impact of incorporating DG sources results in a reduction in the expected cost of voltage sags. <![CDATA[<b>Dynamic model of a small scale concentrating solar cooker with rock bed heat storage</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2016000100004&lng=pt&nrm=iso&tlng=pt This study presents a dynamic model for a concentrating solar energy collector with an integrated rock bed heat storage system. The model is based on numerical integration of a set of conservation equations for mass, momentum and energy of the heat carrier, the rock pebbles and the walls. The heat carrier is compressible air. Numerical solutions are implemented based on implicit time integration without iterations. Stability problems at large time steps do not occur but the accuracy is reduced. The model predicts pressure, velocity, density and temperatures of the fluid, rock bed and wall in time and along the bed. The model is validated with experimental results in a laboratory setting on temperature profiles during charging and discharging of rock bed heat storage. The intention is that the model shall serve as a computational tool for upscaling of air based concentrating solar energy systems with rock bed heat storage units. <![CDATA[<b>Performance analysis of thermosyphon hybrid photovoltaic thermal collector</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2016000100005&lng=pt&nrm=iso&tlng=pt The conversion of solar irradiance into electricity by a photovoltaic module (PV) is 6-17% of the incoming energy from the sun depending on the type of technology and the environmental parameters. More than 80% of incoming energy from the sun is reflected or absorbed by the solar module. The fraction of energy absorbed increases with solar cell temperature and the cells' efficiency drops as a consequence. The efficiency of a PV module is improved by combining a PV module and a thermal collector in one unit, resulting in a hybrid photovoltaic and thermal collector (PV/T). The purpose of this paper is to present the behavior a ther-mosyphon hybrid PV/T when exposed to variations of environmental parameters and to demonstrate the advantage of cooling photovoltaic modules with water using a rectangular channel profile for the thermal collector. A single glazed flat-box absorber PV/T module was designed, its behavior for different environmental parameters tested, the numerical model developed, and the simulation for particular days for Durban weather run. The simulation result showed that the overall efficiency of the PV/T module was 38.7% against 14.6% for a standard PV module while the water temperature in the storage tank reached 37.1 °C. This is a great encouragement to the marketing of the PV/T technology in South Africa particularly during summer, and specifically in areas where the average annual solar irradiance is more than 4.70 kWh/m²/day. <![CDATA[<b>Evaluation of a wind farm project for a smart city in the South-East Coastal Zone of Mauritius</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2016000100006&lng=pt&nrm=iso&tlng=pt A study was carried out to analyse the potential of wind energy in the generation of electricity for a smart city which is located in the South-East Coastal Zone of Mauritius. A flat land area of 10 square km situated about 3.5 km from the smart city was chosen for the placement of a wind farm. The viability of the location was assessed by analysing ten years (Jan 2005 to Dec 2014) of mean hourly wind speed measured at a height of 10 m above ground level (m.a.g.l). The speed data was filtered according to the AWS (1997) guidelines and computed at 60 m.a.g.l using the power law formula. At this height, the average wind speeds was approximately 6.5 m/s, which was considered cost effective, as per the European Wind Energy Union guidelines for the harvesting of wind power. Estimated yearly power generated by a wind farm consisting of 40 wind turbines, each of rating capacity 275 kW, placed at a hub height of 60 m were made. The study resulted in an investment proposal for a 11 MW wind farm project in Mauritius.