Scielo RSS <![CDATA[Journal of Energy in Southern Africa]]> http://www.scielo.org.za/rss.php?pid=1021-447X20080003&lang=es vol. 19 num. 3 lang. es <![CDATA[SciELO Logo]]> http://www.scielo.org.za/img/en/fbpelogp.gif http://www.scielo.org.za <![CDATA[<b>Technological investigations and efficiency analysis of a steam heat exchange condenser: Conceptual design of a hybrid steam condenser</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2008000300001&lng=es&nrm=iso&tlng=es Most of the electricity being produced throughout the world today is from steam power plants. At the same time, many other competent means of generating electricity have been developed viz. electricity from natural gas, MHD generators, biogas, solar cells, etc. But steam power plants will continue to be competent because of the use of water as the main working fluid which is abundantly available and is also reusable. The condenser remains among one of the key components of a steam power plant. The efficiency of a thermal power plant depends upon the efficiency of the condenser. In this paper, a theoretical investigation about thermal analysis and design considerations of a steam condenser has been undertaken. A hybrid steam condenser using a higher surface area to diameter ratio of cooling a water tube has been analyzed. The use of a hybrid steam condenser enables higher efficiency of the steam power plant by lowering condenser steam pressure and increasing the vacuum inside the condenser The latent/sensible heat of steam is used to preheat the feed water supply to the boiler. A conceptual technological design aspect of a super vacuum hybrid surface steam condenser has been theoretically analyzed. <![CDATA[<b>Design analysis methods for Stirling engines</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2008000300002&lng=es&nrm=iso&tlng=es Worldwide attempts are being made to increase the use of our renewable energy sources as well as to use our current fossil fuel energy sources more efficiently. Waste heat recovery forms a substantial part of the latter and is the focus of this project. Stirling technology finds application in both the renewable energy sector and in waste heat recovery. Investigating the applicability of Stirling engines in the above-mentioned fields is relevant to develop more efficient external combustion units as well as to utilize our renewable energy sources. Developing a design analysis and synthesis tool capable of optimizing Stirling powered units forms the main objective of this project. The methodology followed to achieve this, involved the application of three different methods of analysis, namely the method of Schmidt, the adiabatic analysis and the simple analysis based on a five volume approach. The Schmidt analysis is used to obtain the internal engine pressure which is a required input for the adiabatic analysis while the simple analysis introduces pumping losses and regenerator inefficiencies. These methodologies are discussed briefly in this paper. Experimental verification of the analytical data was carried out on a Heinrici Stirling engine and both the analytical data and the experimental data are presented here. Shortcomings of these methods of analysis are highlighted and an alternative approach to solve particular shortcomings is presented. <![CDATA[<b>Potential transportation measures to reduce South Africa's dependency on crude oil</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2008000300003&lng=es&nrm=iso&tlng=es Transportation, including the movement of people and freight, accounts for over 60% of all oil consumed globally, and the world's transportation systems are over 90%o dependent on oil and oil byproducts. Oil represents the single largest item on South Africa's import account. Gasoline and diesel fuels, which are almost exclusively used for transportation services, form a significant proportion of these imports. Globally, transport systems have been built on an over-reliance on cheap oil, allowing towns, cities and the movement of people and goods to be designed around the automobile. People in most South African cities require the use of motorised transport in order to travel efficiently, as public transport systems either do not exist, are too sparse or are difficult to use in many areas. The predicted depletion of oil and thus rising prices will significantly affect the choice of transportation systems and their use, as well as increase South Africa's vulnerability to 'oil shocks'. Transport planning policies must, therefore, prepare for the likelihood of such shocks and ameliorate them via policy options. A precautionary approach needs to be adopted to reduce our dependency on oil. This paper addresses the global shift towards the reduction of transport's dependency on, or reduction in, oil consumption and describes potential ways in which South Africa can reduce its oil dependency along with an indication of a timeframe for implementation. <![CDATA[<b>A system methodology for an energy planning model and renewable energy technologies for agriculture in Nigeria</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2008000300004&lng=es&nrm=iso&tlng=es This paper analyses the system methodology of an energy planning model and renewable energy technology for agricultural operations in Nigeria. The study applies an energy building scenarios approach and with a computer software FORTRAN regression method. Agricultural productivity and value added depend very much on certain factors such as the area of the land under cultivation, extent of multiple cropping, the choice of crop, use of high yielding varieties, use of organic and inorganic fertilizers, the coverage of surface and ground water irrigation schemes, and the extent of mechanization for land preparation.