Scielo RSS <![CDATA[Journal of Energy in Southern Africa]]> http://www.scielo.org.za/rss.php?pid=1021-447X20150004&lang= vol. 26 num. 4 lang. <![CDATA[SciELO Logo]]> http://www.scielo.org.za/img/en/fbpelogp.gif http://www.scielo.org.za <![CDATA[<b>A roadmap framework for solar aided power generation in South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2015000400001&lng=&nrm=iso&tlng= Technology roadmaps are critical for decisions pertaining to technology development. They have been utilised in the renewable energy sector to assist in filtering alternative technology options in order to support energy policy formulation, energy security and energy independence, among others. However, solar aided power generation is a recent concept and no roadmap has been developed for the technology as yet. This paper thus reviewed the literature related to roadmapping with the aim of understanding the methods and tools that have been utilised in other settings. Informed by the literature, a conceptual framework was developed, which was further utilised for the initial analysis for developing a roadmap for solar aided power generation in South Africa. Generally, it would be beneficial for South Africa to integrate solar aided power generation within its current Renewable Energy Independent Power Producer Procurement Programme (REIPPPP) or the National Treasury Public-Private Partnership (PPP) programme. However, it should be noted that this is only feasible in the short- and medium-term. In the long-term, there is a need to support stand-alone solar thermal technologies. <![CDATA[<b>Influence of fire-ignition methods and stove ventilation rates on gaseous and particle emissions from residential coal braziers</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2015000400002&lng=&nrm=iso&tlng= Despite extensive electrification of low-income residential areas on the South African Highveld, extensive use is still made of wood and coal as domestic fuels, particularly for winter space heating. In informal settlements characterised by poverty and lacking electrification, coal is combusted in non-standardised, inefficient and polluting metal braziers, colloquially known as imbaulas. Copious emissions from domestic coal fires result in elevated household and ambient air pollution levels well above national air quality limits. Despite the severity of this pollution as a public health issue, emissions data from residential coal-burning braziers are still scarce. Consequently, there is a need to evaluate the emission characteristics of these devices. In this paper, we report on controlled combustion experiments carried out to investigate systematically influences of fire-ignition methods and stove ventilation rates on gaseous and condensed matter (smoke) emissions from informal residential coal combustion braziers. Two methods of stove ignition-conventional bottom-lit updraft (BLUD) and the top-lit updraft (TLUD) (colloquially known as the Basa njengo Magogo) were investigated. Emission factors (EFs) were found to be dependent on fire ignition method and stove ventilation rates. The top-lit ignition method reduces PM10/PM2.5 by 76% to 80% compared to the BLUD method. Carbon monoxide emissions do not change significantly with the ignition method. Pollutant emissions from normal combustion in high ventilation conditions were low compared to pollutants emitted when an oxygen deficient atmosphere was created under low ventilation conditions. High stove ventilation rates resulted in a 50% reduction in PM10/PM2.5 emissions compared to the low ventilation rates. Emissions of gaseous and particulate matter from incomplete combustion can be minimised by design optimisation of the braziers. Ideally, the emissions of condensed matter particles (which form the bulk of emitted particles in residential coal fires) can be reduced through good mixing of emitted gases and air, and by ensuring a long residence time in the high temperature oxygen rich post combustion zone, to allow for complete oxidation. This study is significant in that it presents the first systematic and comprehensive study of factors affecting emissions from coal braziers. <![CDATA[<b>Batteryless PV desalination system for rural areas: A case study</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2015000400003&lng=&nrm=iso&tlng= The use of photovoltaics (PVs) to power reverse osmosis (RO) desalination can potentially break the dependence of this desalination process on conventional energy sources (oil, coal, electricity from national grid), reduce operational costs, and improve environmental sustainability. In this paper, a methodology for the optimal sizing and performance evaluation of a stand-alone PV system to power an RO desalination unit is presented. This unit covers the water needs of inhabitants of a small isolated village called Mrair-Gabis, near the Ajdabiya city in north-eastern Libya. A photovoltaic-reverse osmosis (PV-RO) system offers good possibilities for satisfying this need. Due to the many technical problems with batteries, as well as their high cost, the system studied in this paper will not consider the use of batteries; the viability of a batterryless system is facilitated by the high solar radiation at the selected site, and long daily average insolation duration. From the water consumption records it was noticed that during some days in summer the water produced by the RO unit does not meet the water demand; on the other hand, during some days of the month there will be an excess of water production. The above considerations led to the design of a freshwater tank, to cover the potable water needs for people in cases of the desalination unit breaking down, either due to tech-nical problems or on the cloudy days. The purpose of the water tank is therefore to store excess water when production exceeds supply. Simulations were carried out using MATLAB Software to size and assess the performance of a stand-alone PV system. The computer program can be applied to any site with different weather conditions. <![CDATA[<b>Comparative evaluation of the performance of an improved solar-biomass hybrid dryer</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2015000400004&lng=&nrm=iso&tlng= A solar biomass hybrid dryer intially designed with a front pass flat plate solar air heater and a biomass heating stove was redesigned, reconstructed in order to minimize the excessive convective heat losses and its performance re-evaluated. Due to poor design and contruction of the biomass heating and solar collector sections, the efficiency of the initial design was low. It is believed that the drying efficiency of the dryer could be enhanced if a back pass solar collector and a biomass heating stove incorporated with a gas to gas heat exchanger to ensure that the hot air reaching the samples is clean, smokeless and ash free, substitute for the original solar collector and biomass unit respectively in the improved version. The system's drying performance was tested on both no load and full capacity load under different meteorological conditions within Nsukka (Lat. 7ºN) for two weeks. The testing results showed that the incorporation of a new back pass solar collector and the heat exchanger enhanced the trays temperatures on no load test. Similarly, the efficiency of the dryer based on solar, biomass and solar-biomass heating in drying of fresh okra, fresh groundnut and fresh cassava chips increased from 5.19 - 16.04%, 0.23 - 3.34% and 1.636 - 8.96% respectively over the initial construction. This shows that the dryer can help improve the post-harvest processing and storage quality of farm produce by drying if further optimized. <![CDATA[<b>Selection of the best location for solar plants in Turkey</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2015000400005&lng=&nrm=iso&tlng= The unique properties of solar energy have led to increasing demands in various countries. In order to use solar energy effectively, environmental and geographical circumstances related to solar intensity must be considered. Different factors may affect the selection of suitable locations for solar plants. These factors must be considered concurrently for optimum location identification. This article presents an approach for the location of solar plants by data envelopment analysis (DEA). Efficiency scores over a twelve month period were evaluated by using a modified similarity to ideal solution (TOPSIS) method. This approach was applied to 30 different cities in different regions of Turkey. <![CDATA[<b>Technical and economic evaluation of energy production from wind in Istanbul and surrounds</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2015000400006&lng=&nrm=iso&tlng= Istanbul is located in the northwest part of Turkey and has the greatest population of any city in the country. Istanbul and its surroundings were researched for wind potential. Energy production from wind was evaluated technically and economically in this study. Çorlu, Kumköy and Şile sites were examined. Other sites in the same region (Göztepe, Kireçburnu, Bahçeköy, Florya and Kartal) were also evaluated but the results were not satisfactory, and for this reason, these sites were not examined in this study. When we checked daily, monthly and yearly wind speed values and frequency distributions, the wind energy potential of Çorlu, Kumköy and Şile were greater than other sites. Çorlu, Kumköy and especially Şile's wind speed data are statistically decreasing. A Nordex N117 91m hub height wind turbine can produce 6099 MWh in Çorlu, 6459 MWh in Şile, 7265 MWh in Kumköy. A Nordex N117 140 m hub height wind turbine can produce 6471 MWh in Çorlu, 7439 MWh in Şile and 8175 MWh in Kumköy. The energy costs were calculated by the average of 36 years of wind measurement data using Nordex N117 turbines. Energy costs with Nordex N117 91 m and 140 m hub height in Çorlu, Şile and Kumköy are 0.025-0,027 US$/KWh, 0.022-0,025 US$/KWh, 0.020-0,023 US$/KWh, respectively. <![CDATA[<b>Sizing, design, and installation of an isolated wind-photovoltaic hybrid power system with battery storage for laboratory general illumination in Afyonkarahisar, Turkey</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2015000400007&lng=&nrm=iso&tlng= In this study, a battery-reinforced hybrid wind-solar power generation system of a size able to meet the electric power requirement for general illumination of the electric laboratory at Afyon Kocatepe University was dimensioned and installed. While determining the installation power of the hybrid wind-solar power generation system, the regional wind-solar energy potential and the magnitude of demanded power were the most important factors. It was decided to supply 400 W of the total 500 W of electric power required by the lamp group used for illumination of the electric laboratory from solar panels and 100 W from a wind turbine according to the wind-solar energy potential of the region and the cost analysis. For the hybrid energy-generation system that was designed and installed, by considering the data for the annual mean sunshine period and wind speed, the most suitable system components and thus the installation cost were determined. The electric power generated by the hybrid wind-solar power generation system and the electric power consumed by the laboratory illumination elements supplied with this system during one year were compared. According to the 12-month measurement results for power generation and consumption in the installed system, it was observed that the generated electric power was higher than the consumed electric power. Consequently, by not paying the total electric bill for electric power consumed by the general illumination elements, use of it for other education expenses was made possible. Besides, the installation costs in Turkey were compared with those in the countries of Denmark, Germany, Spain, and Portugal, where two important components of the dimensioned and installed hybrid wind-solar power generation system - wind and solar energy - are used effectively. <![CDATA[<b>Improving voltage profile of load bus of wind generation system using DSTATCOM</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2015000400008&lng=&nrm=iso&tlng= In a low voltage distribution system with integrated wind plant, voltage stability is impacted by the large variation of load and wind penetration. The compensators like SVC and DSTATCOM are currently being used to address such issue of voltage instability. This paper analyses the impact of wind penetration and variation of active and reactive power of the load on voltage profile of a wind generation system with and without DSTATCOM. It also analyses the performance of the system during fault by calculating various parameters of the system. It has been demonstrated that voltage stability margin increases using DSTATCOM at different wind penetration levels. This system has been simulated and analysed in MATLAB 2011b using a power system toolbox under steady state and transient conditions. <![CDATA[<b>Erratum</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2015000400009&lng=&nrm=iso&tlng= In a low voltage distribution system with integrated wind plant, voltage stability is impacted by the large variation of load and wind penetration. The compensators like SVC and DSTATCOM are currently being used to address such issue of voltage instability. This paper analyses the impact of wind penetration and variation of active and reactive power of the load on voltage profile of a wind generation system with and without DSTATCOM. It also analyses the performance of the system during fault by calculating various parameters of the system. It has been demonstrated that voltage stability margin increases using DSTATCOM at different wind penetration levels. This system has been simulated and analysed in MATLAB 2011b using a power system toolbox under steady state and transient conditions.