Scielo RSS <![CDATA[Journal of Energy in Southern Africa]]> http://www.scielo.org.za/rss.php?pid=1021-447X20110004&lang=es vol. 22 num. 4 lang. es <![CDATA[SciELO Logo]]> http://www.scielo.org.za/img/en/fbpelogp.gif http://www.scielo.org.za <![CDATA[<b>The technical pre-feasibility to use briquettes made from wood and agricultural waste for gasification in a downdraft gasifier for electricity generation</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2011000400001&lng=es&nrm=iso&tlng=es Biomass can be converted to energy through various thermochemical and biological processes. Gasification is one of the thermochemical processes that has recently gained popularity, because it achieves higher conversion efficiencies than, for example, incinerators, boilers or furnaces. Fixed-bed downdraft gasifiers are preferred for electricity generation, because they produce very little tar, but on the other hand, they are limited with regard to biomass properties, such as particle size, bulk density and moisture content. Biomass material with a heterogeneous size is usually processed into pellets or briquettes, which have to be mechanically strong enough to be handled. Cohesive strength is provided by residual moisture and lignin present in most biomass. However, the briquetting process becomes more complicated if one wants to add agricultural waste products that do not necessarily contain lignin as binders. The aim of this work was to process wood chips, grape skins and chicken litter into briquettes that are mechanically stable and have a sufficiently high energy content, as well as adequate bulk density for gasification. The performance of these briquettes in a downdraft gasifier was simulated with a program developed for wood, which was modified to optimise the briquette yield. The results showed a gasification performance comparable to solid pine wood, implying that the blended briquettes could be used as fuel for a downdraft biomass gasifier. Unfortunately, the briquettes proved too instable to experimentally verify the performance in a gasifier. This paper describes the properties of the briquettes as well as the gasification simulation results. <![CDATA[<b>What is the carbon emission factor for the South African electricity grid?</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2011000400002&lng=es&nrm=iso&tlng=es One of the most important parameters for developing Clean Development Mechanism (CDM) project proposals in the electricity sector (both supply and efficiency) is the standard electricity 'grid emission factor', which represents the carbon dioxide related to a megawatt hour of electricity supplied or saved on the grid. While there are detailed guidelines from the CDM Executive Board on how to calculate this emission factor, the values used in registered CDM projects in South Africa vary widely, both due to changes in the rules over time and also to misapplication of the rules. This paper shows how the application of the latest guidelines gives a 'combined margin emission factor' for South Africa of 0.957 tCO2/MWh in 2009/2010. The variation in emission factors in the literature, as well as the importance of reducing the transaction costs for South African project developers, points to the need for an official published grid emission factor from the CDM host country authority in South Africa, the Designated National Authority (DNA), within the Department of Energy. <![CDATA[<b>Industrial and commercial opportunities to utilise concentrating solar thermal systems in South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2011000400003&lng=es&nrm=iso&tlng=es A solar energy technology roadmap has been developed for South Africa. The roadmap lists a number of technological systems that fulfil three requirements from a South African perspective. First, they have clearly been demonstrated or commercialised. Second, a local industry could be stimulated including the potential to export, with associate socio-economic growth; and the other requirements of government can be met in terms of improving energy security and access, and addressing climate change. Third, they have a medium to high R&D intensity, in terms of available capacity and associate resources needed to support the further development of the technological systems. Concentrated Solar Thermal systems feature prominently in the list of technologies. These systems can generate electrical power, then referred to as Concentrating Solar Power systems, typically in the 1 to 100 MW range for on- and off-grid applications. They can also simply produce heat, typically in the 100 to 1000°C range, primarily for commercial and industrial process applications. This paper discusses the international trends and drivers for these systems to generate power and heat, and then focuses on the specific potential in the South African context. A number of barriers to realizing the potential are discussed and recommendations are made accordingly to stimulate the growth of this industry sector in South Africa. <![CDATA[<b>Energy demand projections and relevance of income dynamics in Gauteng's residential sector</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2011000400004&lng=es&nrm=iso&tlng=es Energy modelling serves as a crucial tool for informing both energy policy and strategy development. But the modelling process is faced with both sectoral energy data and structural challenges. Among all the sectors, the residential sector usually presents a huge challenge to the modelling profession due to the dynamic nature of the sector. The challenge is brought by the fact that each an every household in a region may have different energy consumption characteristics and the computing power of the available models cannot incorporate all the details of individual household characteristics. Even if there was enough computing power within the models, energy consumption is collected through surveys and as a result only a sample of a region is captured. These challenges have forced energy modellers to categorise households that have similar characteristics. Different researchers choose different methods for categorising the households. Some researchers choose to categorise households by location and climate, others choose housing types while others choose quintiles. Currently, there is no consensus on which categorisation method takes precedence over others. In these myriad ways of categorising households, the determining factor employed in each method is what is assumed to be the driver of energy demand in that particular area of study. Many researchers acknowledge that households' income, preferences and access to certain fuels determine how households use energy. Although many researchers recognise that income is the main driver of energy demand in the residential sector, there has been no energy modelling study that has tried to categorise households by income in South Africa. This paper chose to categorise households by income because income is taken to be the main driver of energy demand in the urban residential sector. Gauteng province was chosen as a case study area for this paper. The Long-range Energy Alternatives Planning System (LEAP) is used as a tool for such analysis. This paper will further reveal how the dynamics of differing income across the residential sector affects total energy demand in the long run. The households in Gauteng are classified into three income categories - high, middle and low income households. In addition to different income categories, the paper further investigates the energy demand of Gauteng's residential sector under three economic scenarios with five energy demand scenarios. The three economic scenarios are first economic scenario (ECO1), second economic scenario (ECO2) and third economic scenario (ECO3). The most distinguishing factor between these economic scenarios is the mobility of households from one income band to the next. The model results show that electricity demand will be high in all the three economic scenarios. The reason for such high electrical energy demand in all the economic scenarios compared to other fuels is due to the fact that among all the provinces, Gauteng households have one of the highest electricity consumption profiles. ECO2 showed the highest energy demand in all the five energy demand scenarios. This is due to the fact that the share of high income households in ECO2 was very high, compared to the other two economic scenarios. The favourable energy demand scenarios will be the Energy Efficiency and MEPS scenarios due to their ability to reduce more energy demand than other scenarios in all the three economic scenarios. <![CDATA[<b>Sustainable cooling alternatives for buildings</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2011000400005&lng=es&nrm=iso&tlng=es Four sustainable alternative-energy cooling system options are investigated to quantify the actual energy that may be saved when employed in conjunction with conventional air conditioning systems. The four systems considered are active mass cooling, night flushing, roof-spraying and a roof-pond. A one-room building configuration is assumed of which the hourly cooling load and temperature is modelled for both a base case and different combinations of the four sustainable cooling alternative systems. Active mass cooling, night flushing and the roof-spray system proved to be viable options in which the cooling load of an air conditioner may be reduced to maintain a constant room temperature. The roof-spray system showed the most effective results in limiting heat gains to the one-room building and keeping peak room temperatures low. <![CDATA[<b>Policy review and analysis: Energy efficiency strategy for the Republic of South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2011000400006&lng=es&nrm=iso&tlng=es This paper aims to draw attention to the complex landscape of translating policy into implementation actions. It underscores the disjuncture between a broad global response to climate change mitigation measures and the requirements for national action in this regard. Individual countries face this challenge of interpreting and translating the cross-cutting response measures into local action. Climate change mitigation and energy security are two themes that are growing in importance in terms of its contribution towards South Africa's developmental agenda, thereby requiring an understanding of how policies and strategies are geared towards supporting this developmental agenda, in a way that does not compromise existing or future growth and progress. An assessment of the implementation of the South African energy efficiency strategy, demonstrates that the translation of policy intent into implementation is not self evident and associated with a number of prerequisites. These do not merely relate to the competence or capacity of an institution to implement the policy, but to a complex interrelationship of a number of factors. This includes supporting legislation, institutional arrangements, sources of finance and the need for co-operative governance.