Pub Date : 2019-12-05DOI: 10.17159/2413-3051/2019/v30i4a5675
W. Shaw, M. Mathews, J. Marais
In the past the cost of electricity was not a significant concern and was not common practice for mining companies to consider peak time-of-use (TOU) tariffs for their shift schedules. It has become more prevalent, as TOU tariffs continue increasing, to consider energy saving important. A study was carried out to analyse the mining operation of a South African deep-level platinum mine in respect of integrated load management, shift changes and TOU schedules. This was achieved by thoroughly analysing energy consumers, mine operational schedules and their interconnectedness. A specific mining system was analysed as a case study and a maximum savings scenario was determined, using the methodology formulated. The maximum savings scenario schedule change resulted in a 1.3% cost reduction. System improvements had an additional potential reduction effect of 8.4%, which was primarily the result of a reduction in compressors’ power consumption. The implications of the proposed schedule adjustments necessitated a realistic scenario. The realistic scenario had an effective financial reduction of 0.7%. The realistic schedule change, however, opened the door for large system operational improvements, which could increase the reduction potential by 7.6%. The study methods described illustrate the potential implications of integrated load management and operational schedule optimisation on the power demand and cost savings in the mining industry, specifically focusing on deep-level platinum mines.
{"title":"Holistic analysis of the effect on electricity cost in South Africa’s platinum mines when varying shift schedules according to time-of-use tariffs","authors":"W. Shaw, M. Mathews, J. Marais","doi":"10.17159/2413-3051/2019/v30i4a5675","DOIUrl":"https://doi.org/10.17159/2413-3051/2019/v30i4a5675","url":null,"abstract":"In the past the cost of electricity was not a significant concern and was not common practice for mining companies to consider peak time-of-use (TOU) tariffs for their shift schedules. It has become more prevalent, as TOU tariffs continue increasing, to consider energy saving important. A study was carried out to analyse the mining operation of a South African deep-level platinum mine in respect of integrated load management, shift changes and TOU schedules. This was achieved by thoroughly analysing energy consumers, mine operational schedules and their interconnectedness. A specific mining system was analysed as a case study and a maximum savings scenario was determined, using the methodology formulated. The maximum savings scenario schedule change resulted in a 1.3% cost reduction. System improvements had an additional potential reduction effect of 8.4%, which was primarily the result of a reduction in compressors’ power consumption. The implications of the proposed schedule adjustments necessitated a realistic scenario. The realistic scenario had an effective financial reduction of 0.7%. The realistic schedule change, however, opened the door for large system operational improvements, which could increase the reduction potential by 7.6%. The study methods described illustrate the potential implications of integrated load management and operational schedule optimisation on the power demand and cost savings in the mining industry, specifically focusing on deep-level platinum mines.","PeriodicalId":15666,"journal":{"name":"Journal of Energy in Southern Africa","volume":"3 1","pages":"26-40"},"PeriodicalIF":0.0,"publicationDate":"2019-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87369803","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-12-05DOI: 10.17159/2413-3051/2019/v30i4a6044
N. Mbuli, A. Dyantyi, J. Pretorius
Transmission interconnecting lines (called interconnectors in this study) are built to facilitate the exchange of active and reactive power between two areas of a network. Step-up and step-down transformers are required at the ends of the interconnector when interconnectors are at a different voltage, usually higher, than the networks to be connected. A study was carried out to examine the impact on active power losses of a combination of leakage reactances of the transformers at the ends of an interconnector. The study assessed whether combinations can lead to different levels of active power losses and can thus affect the efficiency of the system. It was found that the combinations of reactance have a tangible impact on the power that flows through the interconnector and, consequently, on the sharing of apparent power between the interconnector and the rest of the network. The total active power losses varied appreciably with the various combinations of reactances, resulting in the life-cycle cost of active power losses also varying with the combinations. The study showed that the combination needs to be carefully made, considering that such a choice can have a significant impact on techno-economic aspects of the power system.
{"title":"Potential for grid efficiency based on a combination of leakage reactances of transformers of a transmission interconnecting line: Application of an exhaustive search algorithm","authors":"N. Mbuli, A. Dyantyi, J. Pretorius","doi":"10.17159/2413-3051/2019/v30i4a6044","DOIUrl":"https://doi.org/10.17159/2413-3051/2019/v30i4a6044","url":null,"abstract":"Transmission interconnecting lines (called interconnectors in this study) are built to facilitate the exchange of active and reactive power between two areas of a network. Step-up and step-down transformers are required at the ends of the interconnector when interconnectors are at a different voltage, usually higher, than the networks to be connected. A study was carried out to examine the impact on active power losses of a combination of leakage reactances of the transformers at the ends of an interconnector. The study assessed whether combinations can lead to different levels of active power losses and can thus affect the efficiency of the system. It was found that the combinations of reactance have a tangible impact on the power that flows through the interconnector and, consequently, on the sharing of apparent power between the interconnector and the rest of the network. The total active power losses varied appreciably with the various combinations of reactances, resulting in the life-cycle cost of active power losses also varying with the combinations. The study showed that the combination needs to be carefully made, considering that such a choice can have a significant impact on techno-economic aspects of the power system.","PeriodicalId":15666,"journal":{"name":"Journal of Energy in Southern Africa","volume":"133 1","pages":"1-12"},"PeriodicalIF":0.0,"publicationDate":"2019-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86326867","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-09-19DOI: 10.17159/2413-3051/2019/v30i3a5763
H. Baloyi, Gary M. Dugmore
Co-processing of coal and biomass has been a focus of several research studies aimed at addressing the negative environmental attributes associated with thermal processing of coal alone, as well as improving the thermal behaviour of coal. Biomass materials are regarded as a clean, renewable source, so thermal co-processing of biomass with coal is considered an effective way to utilise coal in a sustainable manner. In this study, coal fines were blended with Scenedesmus microalgae slurry to form a coal-algae composite. Pyrolytic topping of coal-algae composite was performed at 450 ºC on a batch reactor. Parent fuels and resultant chars were analysed for their proximate properties using an Eltra thermostep TGA; a Vario EL cube Elementar was used to determine the elemental composition of the chars and oils. A simulated distillation (SimDis) method was used to determine the boiling point distribution of the produced oils. The objective of the study was to examine the effects of microalgae slurry on the pyrolytic behaviour of waste coal fines with respect to product yields, composition and quality. Results showed that the yields of volatile components from pyrolysis of coal-algae composite were high compared with those from pyrolysis of coal alone. A significant degree of deoxygenation, dehydrogenation and denitrification was observed in coal-algae char than coal char. SimDis results showed that the fossil bio-crude oil has different boiling point characteristics from coal tar. The study has shown that microalgae slurry has potential to influence the pyrolytic behaviour of waste coal under mild inert conditions.
{"title":"Pyrolytic topping of coal-algae composite under mild inert conditions","authors":"H. Baloyi, Gary M. Dugmore","doi":"10.17159/2413-3051/2019/v30i3a5763","DOIUrl":"https://doi.org/10.17159/2413-3051/2019/v30i3a5763","url":null,"abstract":"Co-processing of coal and biomass has been a focus of several research studies aimed at addressing the negative environmental attributes associated with thermal processing of coal alone, as well as improving the thermal behaviour of coal. Biomass materials are regarded as a clean, renewable source, so thermal co-processing of biomass with coal is considered an effective way to utilise coal in a sustainable manner. In this study, coal fines were blended with Scenedesmus microalgae slurry to form a coal-algae composite. Pyrolytic topping of coal-algae composite was performed at 450 ºC on a batch reactor. Parent fuels and resultant chars were analysed for their proximate properties using an Eltra thermostep TGA; a Vario EL cube Elementar was used to determine the elemental composition of the chars and oils. A simulated distillation (SimDis) method was used to determine the boiling point distribution of the produced oils. The objective of the study was to examine the effects of microalgae slurry on the pyrolytic behaviour of waste coal fines with respect to product yields, composition and quality. Results showed that the yields of volatile components from pyrolysis of coal-algae composite were high compared with those from pyrolysis of coal alone. A significant degree of deoxygenation, dehydrogenation and denitrification was observed in coal-algae char than coal char. SimDis results showed that the fossil bio-crude oil has different boiling point characteristics from coal tar. The study has shown that microalgae slurry has potential to influence the pyrolytic behaviour of waste coal under mild inert conditions.","PeriodicalId":15666,"journal":{"name":"Journal of Energy in Southern Africa","volume":"94 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84283862","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-09-18DOI: 10.17159/2413-3051/2019/v30i3a6356
A. Dalton, B. Bekker, A. Kruger
Wind is a naturally variable resource that fluctuates across timescales and, by the same token, the electricity generated by wind also fluctuates across timescales. At longer timescales, i.e., hours to days, synoptic-scale weather systems, notably cold fronts during South African winter months, are important instigators of strong wind conditions and variability in the wind resource. The variability of wind power production from aggregates of geographically disperse turbines for the passage of individual cold fronts over South Africa was simulated in this study. When considering wind power variability caused by synoptic-scale weather patterns, specifically cold fronts, the timescale at which analysis is conducted was found to be of great importance, as relatively small mean absolute power ramps at a ten-minute temporal resolution, order of 2-4% of simulated capacity, can result in large variations of total wind power production (at the order of 32–93% of simulated capacity) over a period of three to four days as a cold front passes. It was found that when the aggregate consists of a larger and more geographically dispersed set of turbines, as opposed to a smaller set of turbines specifically located within cold-front dominated high wind areas, variability and the mean absolute ramp rates decrease (or gets ‘smoothed’) across the timescales considered. It was finally shown that the majority of large simulated wind power ramp events observed during the winter months, especially at longer timescales, are caused by the passage of cold fronts.
{"title":"Wind power variability during the passage of cold fronts across South Africa","authors":"A. Dalton, B. Bekker, A. Kruger","doi":"10.17159/2413-3051/2019/v30i3a6356","DOIUrl":"https://doi.org/10.17159/2413-3051/2019/v30i3a6356","url":null,"abstract":"Wind is a naturally variable resource that fluctuates across timescales and, by the same token, the electricity generated by wind also fluctuates across timescales. At longer timescales, i.e., hours to days, synoptic-scale weather systems, notably cold fronts during South African winter months, are important instigators of strong wind conditions and variability in the wind resource. The variability of wind power production from aggregates of geographically disperse turbines for the passage of individual cold fronts over South Africa was simulated in this study. When considering wind power variability caused by synoptic-scale weather patterns, specifically cold fronts, the timescale at which analysis is conducted was found to be of great importance, as relatively small mean absolute power ramps at a ten-minute temporal resolution, order of 2-4% of simulated capacity, can result in large variations of total wind power production (at the order of 32–93% of simulated capacity) over a period of three to four days as a cold front passes. It was found that when the aggregate consists of a larger and more geographically dispersed set of turbines, as opposed to a smaller set of turbines specifically located within cold-front dominated high wind areas, variability and the mean absolute ramp rates decrease (or gets ‘smoothed’) across the timescales considered. It was finally shown that the majority of large simulated wind power ramp events observed during the winter months, especially at longer timescales, are caused by the passage of cold fronts. ","PeriodicalId":15666,"journal":{"name":"Journal of Energy in Southern Africa","volume":"62 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73355328","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-09-18DOI: 10.17159/2413-3051/2019/v30i3a5691
A. A. Ajayi-Obe, M. A. Khan, P. Barendse
Developers and operators are interested in improving the reliability and reducing the associated costs of wind power plants (WPPs) because of the continuous increase in the power capacity of wind energy conversion systems (WECSs) and the increasing development of WPPs. The electrical subsystem of the WPP experiences the highest failure rate and constitutes a significant proportion of its total cost. Reliability of the WECS can be increased and its cost reduced by eliminating the wind turbine transformer from the electrical subsystem. This study gives a techno-economic evaluation of a five-level nested neutral point clamped (NNPC) converter topology for transformer-less connection of high- power WECSs. The approach entailed the calculation of reliability of five-level NNPC converter topology deployed in the grid-side of a WECSs. This method presents a mathematical formula for deriving the reliability of a five-level NNPC converter topology by using the reliability block diagram and reliability estimation-based models in the military handbook (MIL-HDBK-217F). The cost analysis model shows that the total cost of the five-level diode clamped converter topology was higher than the five-level NNPC converter topology. The study could be extended by carrying out accurate modelling of the mission profile of the presented converter by using multi-domain simulation technique.
{"title":"Techno-economic evaluation of five-level nested neutral point clamped converter topology for transformer-less connection of high-power wind energy conversion systems","authors":"A. A. Ajayi-Obe, M. A. Khan, P. Barendse","doi":"10.17159/2413-3051/2019/v30i3a5691","DOIUrl":"https://doi.org/10.17159/2413-3051/2019/v30i3a5691","url":null,"abstract":"Developers and operators are interested in improving the reliability and reducing the associated costs of wind power plants (WPPs) because of the continuous increase in the power capacity of wind energy conversion systems (WECSs) and the increasing development of WPPs. The electrical subsystem of the WPP experiences the highest failure rate and constitutes a significant proportion of its total cost. Reliability of the WECS can be increased and its cost reduced by eliminating the wind turbine transformer from the electrical subsystem. This study gives a techno-economic evaluation of a five-level nested neutral point clamped (NNPC) converter topology for transformer-less connection of high- power WECSs. The approach entailed the calculation of reliability of five-level NNPC converter topology deployed in the grid-side of a WECSs. This method presents a mathematical formula for deriving the reliability of a five-level NNPC converter topology by using the reliability block diagram and reliability estimation-based models in the military handbook (MIL-HDBK-217F). The cost analysis model shows that the total cost of the five-level diode clamped converter topology was higher than the five-level NNPC converter topology. The study could be extended by carrying out accurate modelling of the mission profile of the presented converter by using multi-domain simulation technique.","PeriodicalId":15666,"journal":{"name":"Journal of Energy in Southern Africa","volume":"70 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87996188","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-09-18DOI: 10.17159/2413-3051/2019/v30i3a5669
D. Pullinger, A. Ali, M. Zhang, N. Hill, T. Crutchley
This study addresses two key objectives using operational performance data from most of the Round 1 wind farms connected to the grid in South Africa: benchmarking of wind farm performance and validation of the pre-construction energy yield assessments. These wind farms were found to perform in line with internationally reported levels of wind farm availability, with a mean energy-based availability of 97.8% during the first two years of operation. The pre-construction yield assessments used for financing in 2012 were found to over-predict project yield (P50) by 4.9%. This was consistent with other validation studies for Europe and North America. It was also noted that all projects exceed the pre-construction P90 estimate. The reasons for this discrepancy were identified, with the largest cause of error being wind flow and wake-modelling errors. Following a reassessment using up to date methodologies from 2018, the mean bias in pre-construction predictions was 1.4%.
{"title":"Improving accuracy of wind resource assessment through feedback loops of operational performance data: A South African case study","authors":"D. Pullinger, A. Ali, M. Zhang, N. Hill, T. Crutchley","doi":"10.17159/2413-3051/2019/v30i3a5669","DOIUrl":"https://doi.org/10.17159/2413-3051/2019/v30i3a5669","url":null,"abstract":"This study addresses two key objectives using operational performance data from most of the Round 1 wind farms connected to the grid in South Africa: benchmarking of wind farm performance and validation of the pre-construction energy yield assessments. These wind farms were found to perform in line with internationally reported levels of wind farm availability, with a mean energy-based availability of 97.8% during the first two years of operation. The pre-construction yield assessments used for financing in 2012 were found to over-predict project yield (P50) by 4.9%. This was consistent with other validation studies for Europe and North America. It was also noted that all projects exceed the pre-construction P90 estimate. The reasons for this discrepancy were identified, with the largest cause of error being wind flow and wake-modelling errors. Following a reassessment using up to date methodologies from 2018, the mean bias in pre-construction predictions was 1.4%.","PeriodicalId":15666,"journal":{"name":"Journal of Energy in Southern Africa","volume":"30 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76471175","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-09-18DOI: 10.17159/2413-3051/2019/v30i3a5654
Steven Matome Mathetsa, M. D. Simatele, I. Rampedi, G. Gericke
It is increasingly acknowledged that the water-energy-climate change (WECC) nexus is one of the synergies that pose a significant risk to achievement of sustainable development goals (SDGs), specifically numbers six, seven and thirteen. There are suggestions that climate change outcomes such as increased temperature and drought episodes have implications for water availability, which in turn affects energy production in countries dependent on hydropower, pump-storage or coal-generated electricity, including South Africa. This development therefore calls for improved understanding of how to effectively manage the challenges that arise from this nexus, to mitigate the impacts it may have on achieving the associated SDGs. This study, which is based on an in-depth appraisal of existing developments, assessed the potential of the integrated water resource management framework in understanding the WECC nexus and its implications for South Africa’s sustainable development endeavours, particularly in the context of water resource management and utilisation. The study revealed South Africa’s lack of integrated, effective, and efficient institutions and policy framework to comprehensively manage the challenges emanating from this nexus. It identified an urgent need to develop systems and processes through which South Africa can handle the challenges as well as capture the benefits that may be obtained from this nexus.
{"title":"Perspectives on integrated water resource management and its relevance in understanding the water-energy-climate change nexus in South Africa","authors":"Steven Matome Mathetsa, M. D. Simatele, I. Rampedi, G. Gericke","doi":"10.17159/2413-3051/2019/v30i3a5654","DOIUrl":"https://doi.org/10.17159/2413-3051/2019/v30i3a5654","url":null,"abstract":"It is increasingly acknowledged that the water-energy-climate change (WECC) nexus is one of the synergies that pose a significant risk to achievement of sustainable development goals (SDGs), specifically numbers six, seven and thirteen. There are suggestions that climate change outcomes such as increased temperature and drought episodes have implications for water availability, which in turn affects energy production in countries dependent on hydropower, pump-storage or coal-generated electricity, including South Africa. This development therefore calls for improved understanding of how to effectively manage the challenges that arise from this nexus, to mitigate the impacts it may have on achieving the associated SDGs. This study, which is based on an in-depth appraisal of existing developments, assessed the potential of the integrated water resource management framework in understanding the WECC nexus and its implications for South Africa’s sustainable development endeavours, particularly in the context of water resource management and utilisation. The study revealed South Africa’s lack of integrated, effective, and efficient institutions and policy framework to comprehensively manage the challenges emanating from this nexus. It identified an urgent need to develop systems and processes through which South Africa can handle the challenges as well as capture the benefits that may be obtained from this nexus.","PeriodicalId":15666,"journal":{"name":"Journal of Energy in Southern Africa","volume":"108 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87629790","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-09-18DOI: 10.17159/2413-3051/2019/v30i3a6314
P. Govender, V. Sivakumar
Diffuse irradiance is important for the operation of solar-powered devices such as photovoltaics, so it is important to analyse its behaviour under different sky conditions. The primary cause of short-term irradiance variability is clouds. One approach to analyse the diffuse irradiance variation is to use cluster analysis to group together days experiencing similar cloud patterns. A study was carried out to examine the application of k-means clustering to daily cloud data in Durban, South Africa (29.87 °S; 30.98 °E), which revealed four distinct day-time cloud cover (CC) patterns classified as Class I, II, III and IV, corresponding to cloudy, sunny, or a combination of the two. Diffuse irradiance was then correlated with each of the classes to establish corresponding diurnal irradiance patterns and the associated temporal variation. Class I had highest diffuse irradiance variation, followed by Classes III, IV and II. To further investigate the local cloud dynamics, cloud types were also analysed for Classes I−IV. It was found that stratocumulus (low cloud category); altocumulus translucidus, castellanus and altocumulus (middle cloud category); and cirrus fibrates and spissatus (high cloud category), were the most frequently occurring cloud types within the different classes. This study contributes to the understanding of the diurnal diffuse irradiance patterns under the four most frequently occurring CC conditions in Durban. Overall, knowledge of these CC and associated diffuse irradiance patterns is useful for solar plant operators to manage plant output where, depending on the CC condition, the use of back-up devices may be increased or reduced accordingly.
{"title":"Investigating diffuse irradiance variation under different cloud conditions in Durban, using k-means clustering","authors":"P. Govender, V. Sivakumar","doi":"10.17159/2413-3051/2019/v30i3a6314","DOIUrl":"https://doi.org/10.17159/2413-3051/2019/v30i3a6314","url":null,"abstract":"Diffuse irradiance is important for the operation of solar-powered devices such as photovoltaics, so it is important to analyse its behaviour under different sky conditions. The primary cause of short-term irradiance variability is clouds. One approach to analyse the diffuse irradiance variation is to use cluster analysis to group together days experiencing similar cloud patterns. A study was carried out to examine the application of k-means clustering to daily cloud data in Durban, South Africa (29.87 °S; 30.98 °E), which revealed four distinct day-time cloud cover (CC) patterns classified as Class I, II, III and IV, corresponding to cloudy, sunny, or a combination of the two. Diffuse irradiance was then correlated with each of the classes to establish corresponding diurnal irradiance patterns and the associated temporal variation. Class I had highest diffuse irradiance variation, followed by Classes III, IV and II. To further investigate the local cloud dynamics, cloud types were also analysed for Classes I−IV. It was found that stratocumulus (low cloud category); altocumulus translucidus, castellanus and altocumulus (middle cloud category); and cirrus fibrates and spissatus (high cloud category), were the most frequently occurring cloud types within the different classes. This study contributes to the understanding of the diurnal diffuse irradiance patterns under the four most frequently occurring CC conditions in Durban. Overall, knowledge of these CC and associated diffuse irradiance patterns is useful for solar plant operators to manage plant output where, depending on the CC condition, the use of back-up devices may be increased or reduced accordingly.","PeriodicalId":15666,"journal":{"name":"Journal of Energy in Southern Africa","volume":"32 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77817000","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-08-05DOI: 10.17159/2413-3051/2018/V29I4A6503
M. J. Roberts, G. Landwehr
{"title":"SAWEA's WindAc 2019 Conference Editorial","authors":"M. J. Roberts, G. Landwehr","doi":"10.17159/2413-3051/2018/V29I4A6503","DOIUrl":"https://doi.org/10.17159/2413-3051/2018/V29I4A6503","url":null,"abstract":"","PeriodicalId":15666,"journal":{"name":"Journal of Energy in Southern Africa","volume":"20 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73906819","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-24DOI: 10.17159/2413-3051/2019/V30I2A6375
E. Mkhwebane, N. Ntuli
Over the past decade South Africa has seen an increase in the uptake of solar energy as a result of the Renewable Energy Independent Power Producer Programme, which led to a sharp increase in procurement of utility-scale solar PV projects. On the other hand, the load shedding which was implemented by the national power utility in response to electricity supply and demand challenges resulted in the rise in procurement of small-scale embedded generation solar PV systems. While the REIPPPP has had minimal impact in terms of incorporating small, medium and micro scale enterprises (SMMEs) in the renewable energy value chain, there is a significant opportunity for SMMEs in the small scale embedded generation (SSEG) market segment. This study investigated the challenges and opportunities for SMMEs in SSEG.
{"title":"Alternatives for small, medium and micro scale enterprises participation in the renewable energy industry - small scale embedded generation review","authors":"E. Mkhwebane, N. Ntuli","doi":"10.17159/2413-3051/2019/V30I2A6375","DOIUrl":"https://doi.org/10.17159/2413-3051/2019/V30I2A6375","url":null,"abstract":"Over the past decade South Africa has seen an increase in the uptake of solar energy as a result of the Renewable Energy Independent Power Producer Programme, which led to a sharp increase in procurement of utility-scale solar PV projects. On the other hand, the load shedding which was implemented by the national power utility in response to electricity supply and demand challenges resulted in the rise in procurement of small-scale embedded generation solar PV systems. While the REIPPPP has had minimal impact in terms of incorporating small, medium and micro scale enterprises (SMMEs) in the renewable energy value chain, there is a significant opportunity for SMMEs in the small scale embedded generation (SSEG) market segment. This study investigated the challenges and opportunities for SMMEs in SSEG.","PeriodicalId":15666,"journal":{"name":"Journal of Energy in Southern Africa","volume":"2 6 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81970246","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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