Scielo RSS <![CDATA[Journal of Energy in Southern Africa]]> http://www.scielo.org.za/rss.php?pid=1021-447X20140003&lang=es vol. 25 num. 3 lang. es <![CDATA[SciELO Logo]]> http://www.scielo.org.za/img/en/fbpelogp.gif http://www.scielo.org.za <![CDATA[<b>A case study of climate variability effects on wind resources in South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2014000300001&lng=es&nrm=iso&tlng=es The wind energy sector is one of the most prominent sectors of the renewable energy industry. However, its dependence on meteorological factors subjects it to climate change. Studies analysing the impact of climate change on wind resources usually only model changes in wind speed. Two elements that have to be calculated in addition to wind speed changes are Annual Energy Production (AEP) and Power Density (PD). This is not only because of the inherent variability between wind speed and wind power generated, but also because of the relative magnitudes of change in energy potentially generated at different areas under varied wind climates. In this study, it was assumed that two separate locations would experience a 10% wind speed increase after McInnes et al. (2010). Given the two locations' different wind speed distributions, a wind speed increase equal in magnitude is not equivalent to similar magnitudes of change in potential energy production in these areas. This paper demonstrates this fact for each of the case studies. It is of general interest to the energy field and is of value since very little literature exists in the Southern African context on climate change- or variability-effects on the (wind) energy sector. Energy output is therefore dependent not only on wind speed, but also wind turbine characteristics. The importance of including wind power curves and wind turbine generator capacity in wind resource analysis is emphasised. <![CDATA[<b>Clear sky solar illuminance using visual band irradiance</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2014000300002&lng=es&nrm=iso&tlng=es Solar illuminance may be quantified by applying relevant efficacy functions to available full spectrum ground irradiance. Alternatively, illuminance may be determined by applying the Photopic function to ground level irradiance spectra obtained from the terrestrial irradiance spectrum adjusted using relevant atmospheric absorption and scattering coefficients. The Photopic function has finite values in the wavelength range of 400 nm to 700 nm and is concentrated around a mean wavelength of 555 nm with irradiance at wavelengths close to 555 nm contributing to the major portion of illuminance. Calculation of ground level direct, diffuse and hence global illuminance is simplified as absorption of irradiance in the atmosphere by water vapour and uniformly mixed gases is negligible and may be ignored. It is shown that due to the small variations in the overall irradiance over wavelengths in the visible bandwidth combined with the concentration effect of the Photopic function in this wavelength range illuminance may be calculated, with good accuracy, using constant extinction functions for both direct and diffuse illuminance. Due to the concentration of illuminance by the Photopic function global illuminance data were also correlated with a simplified description of illuminance attenuation through the atmosphere based on the Beer-Lambert-Bouger Law using a single constant effective extinction coefficient which accounts for all extinction processes under clear sky conditions over the visible range of wavelengths. Constants used in extinction functions for solar irradiance due atmospheric aerosols were obtained by fitting experimental data to analytical descriptions of atmospheric extinction while published constants were used for ozone and Rayleigh scattering. The analytical descriptions of global illuminance with solar elevation were compared with experimental data collected at Johannesburg over both summer and winter clear sky conditions. Correlations of measured and calculated global illuminance data for the method based on extinction of various atmospheric components was 4.47 % and 4.49 % for the method based on the Beer-Lambert-Bouger Law, both normalised using the terrestrial illuminance constant. While measurements were made at a specific site in Gauteng, the methods used to correlate the data are general and location independent but local climatic conditions may need to be taken into account to quantify the extinction coefficients for specific areas. <![CDATA[<b>An assessment of electricity supply and demand at Emfuleni Local Municipality</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2014000300003&lng=es&nrm=iso&tlng=es Globally, electricity has become a modern tool to supply energy to households. This study investigates the supply and demand of household electricity and sustainability of distribution centres at Emfuleni Local Municipality (ELM). South Africa follows a vigorous programme of electrification, spearheaded by Eskom. Eskom is a South African state-owned power company which strives to meet the country's increasing demand for energy. Resi-dential energy demand is growing as population levels rise and the number of households in ELM increases. Recently (2008-2010) in South Africa there have been unprecedented levels of load shedding nationally and there is a shortage of centres to purchase electricity. Furthermore, households do not receive uninterrupted electricity on a daily basis, largely because of stolen electrical cables and illegal connections. Low-income residents of Evaton, ELM, were interviewed. Empirical surveys were conducted and a theoretical exposition drawn up to meet the objectives of the study. It was found that electricity supply and demand in ELM is adequate but there is a shortage of selling points in Evaton and there are barriers towards the effectiveness of electricity consumption. In addition, public awareness programmes must continue to educate the communities to avoid stealing the electrical cables. Illegal connection must be reported to the local councillors for them to make sure that this activity is stopped in Evaton. <![CDATA[<b>Energy consumption, thermal utilization efficiency and hypericin content in drying leaves of St John's Wort <i>(Hypericum Perforatum)</i></b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2014000300004&lng=es&nrm=iso&tlng=es Massive consumption of energy in the drying industry has prompted extensive research regarding various aspects of drying energy and requirements. Thermal utilization efficiency, specific energy requirement, total energy consumption and hypericin content in drying of St John's Wort were determined using a hot-air dryer. Experiments were conducted at four air temperature levels (40, 50, 60, and 70°C), three air velocities (0.3, 0.7, and 1 m/s) and three sample thicknesses (1, 2 and 3 cm). Based on the results of data analysis, minimum and maximum levels of energy consumption were 0.56 and 3.24 kWh, respectively. The required specific energy decreased with increasing sample thickness. The minimum and maximum required specific energies were 4.41 and 17.53 for 2 cm thick and 4.28 and 13.67 for 3 cm thick layers (kWh/kg), respectively. The maximum and minimum values of thermal utilization efficiency in different treatments were found to be 14% and 72%, respectively. Hypericin content decreased with increasing temperature and increased with air velocity and product sample thickness, so that the minimum and maximum hypericin amounts were 67 and 355 ppm, respectively. <![CDATA[<b>Practical considerations for low pressure solar water heaters in South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2014000300005&lng=es&nrm=iso&tlng=es This paper presents the results of the design parameters that affect natural convection of Low Pressure (LP) Solar Water Heaters (SWH) in South Africa. Fluid flow plays an important role in the heat transfer process associated with natural convection. Three partial differential governing equations were considered. These equations are non-dimensionalized and a similarity solution was applied to obtain two coupled non-linear ordinary differential equations which are solved in MATLAB. Two scenarios were considered for the simulation, a vertical wall with a constant wall temperature and a vertical wall with a constant heat flux. The temperature and velocity profiles were obtained for both scenarios and compared. The effect of the length, diameter and tilt angle of the tube in relation to the amount of heat transferred to the water was investigated specifically for Cape Town. These results are used to discuss design and installation considerations for LP SWHs and are presented in the paper. <![CDATA[<b>The impacts of energy prices and technological innovation on the fossil fuel-related electricity-growth nexus: An assessment of four net energy exporting countries</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2014000300006&lng=es&nrm=iso&tlng=es This study uses annual data from 1974 to 2011 to examine the long-run and short-run relationships between fossil fuel powered electricity consumption, economic growth, energy prices and technological innovation for four net energy exporting countries. Canada, Ecuador, Norway and South Africa are chosen as the main research background in order to investigate how the development degree and economic dependence on energy exports affect the electricity-growth nexus. Based on the results drawing from the ARDL approach and the Granger causality test, economic growth positively influences the variation in fossil fuel powered electricity consumption in both the short-run and long-run for all four countries. The reverse causality from electricity consumption to economic growth is only evident in Ecuador and Norway. The degree of dependence on energy exports is a contributory factor of explaining the causality puzzle of the electricity-growth nexus. Given the fact that technological innovation does not benefit fossil fuel powered electricity generation, this paper suggests these net energy exporting countries to replace fossil fuel with more sustainable and effective sources in the electricity generation process. <![CDATA[<b>Economic implications of constant power outages on SMEs in Nigeria</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2014000300007&lng=es&nrm=iso&tlng=es This paper is concerned with the unabated epileptic power (electric) delivery which is seen to be periodic with a struggling generation capacity and losses-prone inefficient transmission network in Nigeria. Ordinarily, it should mean that only an average Nigerian suffers directly, and only, the burden of this inefficiency, whereby electricity supply to power both household and commercial appliances becomes unpredictable. Yet, further studies have revealed that there is almost no other sector that this ineptitude does not impact indirectly, especially as adverse economic consequences. GDP per Capita versus electrical energy production data for Nigeria and selected countries for the year 2004 served as input parameters which underwent research validation. Small and medium scale enterprises (SMEs) were a case study in this paper. In the end, submissions are that apart from the internal devastating effect on SMEs, constant power outages have a major connection with the recent trends of big companies closing or relocating from Nigeria. To sum up, measures were suggested for improvement. <![CDATA[<b>Renewable energy investment in Nigeria: A review of the Renewable Energy Master Plan</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2014000300008&lng=es&nrm=iso&tlng=es Data for investment into renewable energy resources in Nigeria is mainly unavailable due to over reliance on conventional resources for energy generation. However, recent developments in the energy sector have portrayed gradual attention to investments in renewable energy resources. This paper reviews the Renewable Energy Master Plan (REMP) which identifies this improvement and presents a draft on how an increase in investment in renewable energy resources, which will in the long run balance the national energy equation, ensure energy security and promote sustainable development. <![CDATA[<b>A pilot test of ethanol gel as a paraffin replacement in a low-income urban environment</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2014000300009&lng=es&nrm=iso&tlng=es This paper describes the results of a pilot programme to introduce ethanol gel as a replacement for paraffin for cooking in a low-income informal settlement, Samora Machel, in the Philippi district of Cape Town. A baseline study had shown that paraffin was the dominant source of energy in this community, and that the community knew that its use was both hazardous and unhealthy, but they had no apparent alternative. A gel fuel meeting the requirements of SANS 448 was identified and supplies ordered. A burner system meeting the requirements of SANS 666 was not available on the market; instead it was necessary to use all that could be found. The Agrifood Technology Station at the Cape Peninsula University of Technology (CPUT) was tasked with finding ways to cook using ethanol gel, with accent being placed on cooking safely and using the least possible quantity of gel for a standard menu. After several fruitless attempts to launch a programme, a successful meeting was held at the creche in Samora Machel at which a number of residents agreed to take part in the pilot programme. Soon thereafter, there was a fire in which many residents lost all their possessions, and when stoves were distributed free of charge, and five litres of gel sold at a subsidised price, all stoves were eagerly taken. The demonstration of how to cook using the gel was held at the point of distribution, and people taking stoves were shown how they worked and how to keep them clean. Every week for four weeks, a sample of the participants was contacted to determine their response to cooking on gel. Virtually every response was most positive, and at the end of that period the participants in the pilot programme requested that the supply of gel should continue as long as possible. <![CDATA[<b>The energy profile of a low-income urban community</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2014000300010&lng=es&nrm=iso&tlng=es As part of a household energisation experiment, a baseline survey was undertaken from a sample of 152 households in the informal settlement of Samora Machel. The survey covered energy needs for cooking, space heating, water heating, lighting and any other demands, the costs of energy and total household monthly expenses. The average home had 3-4 inhabitants in less than 2 rooms. Paraffin was the primary source of energy for cooking and space heating, and played a significant role in water heating and lighting. Electricity was quite widely available, but was used primarily for low-power services such as radios and cellphones. Only 10% of all homes had a refrigerator. 20% of all homes purchased LP gas regularly but only used it on social occasions. Fuelwood was collected rather than purchased, and mainly burned in an open brazier, both for cooking and space heating. Space heating was primarily by cookstove; only one home had a specially designed heater using paraffin fuel. The median household expenditure was R1 800/month and 20% of this was spent on energy services. About half the homes are at risk of energy poverty, where lack of energy could give rise to a range of health problems, particularly during the colder months. <![CDATA[<b>Palz, Wolfgang. 2014. <i>Solar power for the world. What you wanted to know about photovoltaics</i></b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2014000300011&lng=es&nrm=iso&tlng=es As part of a household energisation experiment, a baseline survey was undertaken from a sample of 152 households in the informal settlement of Samora Machel. The survey covered energy needs for cooking, space heating, water heating, lighting and any other demands, the costs of energy and total household monthly expenses. The average home had 3-4 inhabitants in less than 2 rooms. Paraffin was the primary source of energy for cooking and space heating, and played a significant role in water heating and lighting. Electricity was quite widely available, but was used primarily for low-power services such as radios and cellphones. Only 10% of all homes had a refrigerator. 20% of all homes purchased LP gas regularly but only used it on social occasions. Fuelwood was collected rather than purchased, and mainly burned in an open brazier, both for cooking and space heating. Space heating was primarily by cookstove; only one home had a specially designed heater using paraffin fuel. The median household expenditure was R1 800/month and 20% of this was spent on energy services. About half the homes are at risk of energy poverty, where lack of energy could give rise to a range of health problems, particularly during the colder months.