Electrical energy is commonly used in households and in industry - demand continues to rise due to economic and population growth. This requires that energy suppliers must increase their supply capacity. The result is that end–user energy costs continue to increase, therefore a growing need exists to reduce electrical energy demand in South Africa and internationally. Households account for the majority of electrical energy customers, but they only consume a fraction of the total energy supplied. The industrial sector and mines combined consume approximately 42% of the total electrical energy produced. Approximately 10% of this energy goes into compressed air production. This study focuses on methods of reducing the requirement of compressed air in industry so that the demand for electrical energy can be reduced. Many studies have focused on specific methods of reducing energy usage associated with compressed air production. These methods are categorised into methods of reducing compressed air requirements and methods of increasing compressed air supply efficiency. This study aims to combine these efforts into a single optimised solution. Although this study includes industry in general, the central focus is on the South African mining industry. Two different mining sites are considered and analysed as case studies. Methods of reducing energy required to produce compressed air were applied to each case study. Case Study 1 only allowed limited control of the compressed air system. In Case Study 2 integrated control was realised. Energy usage of compressors was reduced by 18.9% and 42.9% respectively. Results show that system savings can be doubled by combining different methods of reducing energy usage of compressed air. This, however, requires continuous monitoring and control of the air network at each section supplied with compressed air. The study is limited to achieving savings by changing the air system. Additional savings can be achieved by training personnel, altering schedules of production activities and implementing a system designed to locate air leaks. / Thesis (M.Ing. (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2012.

Mines in general, make use of compressed air systems for daily operational activities. Compressed air on mines is traditionally distributed in two typical fashions. Firstly, direct pipe feed systems for single shafts or compressed air ring networks where multiple shafts are supplied with compressed air from an integral system. These compressed air networks make use of number compressors feeding the ring from various locations in the network. While mines have sophisticated control systems to control these compressors they are not dynamic. Compressors are selected on static priorities for a chosen time period of the day. While this is acceptable for some days it is not always the ideal solution. The compressed air demand of the ring is dynamic and it is difficult to estimate the future need of the system. The Dynamic Compressor Selector (DCS) is described as a solution to this problem. DCS is a computer based control system featuring a Graphical User Interface (GUI). The aim of DCS is to dynamically calculate a control pressure set-point, given the demand for compressed air as well as choose the optimal compressors to supply the given compressed air. This will reduce the power requirement of the compressed air ring as well as reduce compressor cycling. DCS was implemented and tested on a single mine compressed air system. Achieved results were 1.8 MW in electricity savings as well as the added benefit of reduced cycling. This saving results in a cost saving of R3.7 million per annum. The problems and shortfalls of the system are also discussed as well as possible future directions for moving forward. / MIng (Computer and Electronic Engineering), North-West University, Potchefstroom Campus, 2014

Compressed air makes up an important part of South African precious metal mining processes. Rising operational costs in the struggling mining sector increased the interest of the power utility, Eskom, and mine management in achievable electrical energy savings. Demand side management initiatives, funded by Eskom, realised a significant improvement in electrical energy efficiency of compressed air networks. Supply side interventions further aided optimisation by lowering operational costs. Previous research identified the need for integrating compressed air supply and demand side initiatives. Automated compressor control systems were needed in industry to realise missed opportunities due to human error on manual control systems. Automatic systems were found to be implemented in the industry, but missed savings opportunities were still encountered. This was due to the static nature of these control systems, requiring human intervention from skilled artisans. A comprehensive system is required that can adjust dynamically to the ever-changing demand and other system changes. Commercially available simulation software packages have been used by various mine groups to determine an optimal control philosophy. Satisfactory results were obtained, but the simulations were still based on static control inputs. No simulation system was found that could solve and optimise a system based on real-time instrumentation feedback. By combining simulation capabilities with dynamic control in real time, advanced optimisation could be achieved. Development was done on the theoretical design of the system, where mathematical calculations and the accuracy of the system were evaluated. This study proved that the new controller was viable and, as a result, the development of a fully dynamic control Automation of compressor networks through a dynamic control system iii system incorporating the verified mathematical models followed. All of this was done following a theoretical approach. Intricate control requirements on the supply side were evaluated to determine the impact of new intelligent compressor control strategies. It was found that improved compressor control realised an additional 6.2% electrical energy saving on top of existing savings initiatives. Practical limitations and human perception issues were also addressed. Financial cost-benefit analyses were used to evaluate the viability of using automated compressor control. Ample maintenance data obtained from two leading mining companies was used to evaluate the impact of increased stopping and starting of compressors. Financial cost savings from electrical energy efficiency control strategies were found to considerably outweigh the minimal increase in compressor maintenance. Savings potential on deep-level mines proved to be in the order of 5% of the baseline consumption. When these results are extrapolated to the remaining 22 South African deep-level gold and platinum mines already subjected to demand side management initiatives, potential savings of 12.67 MW can be realised. Based on the Eskom 2014/2015 Megaflex tariff structure, the financial cost saving from 12.67 MW is R61 million. / PhD (Electrical Engineering), North-West University, Potchefstroom Campus, 2015

Mines in general, make use of compressed air systems for daily operational activities. Compressed air on mines is traditionally distributed in two typical fashions. Firstly, direct pipe feed systems for single shafts or compressed air ring networks where multiple shafts are supplied with compressed air from an integral system. These compressed air networks make use of number compressors feeding the ring from various locations in the network. While mines have sophisticated control systems to control these compressors they are not dynamic. Compressors are selected on static priorities for a chosen time period of the day. While this is acceptable for some days it is not always the ideal solution. The compressed air demand of the ring is dynamic and it is difficult to estimate the future need of the system. The Dynamic Compressor Selector (DCS) is described as a solution to this problem. DCS is a computer based control system featuring a Graphical User Interface (GUI). The aim of DCS is to dynamically calculate a control pressure set-point, given the demand for compressed air as well as choose the optimal compressors to supply the given compressed air. This will reduce the power requirement of the compressed air ring as well as reduce compressor cycling. DCS was implemented and tested on a single mine compressed air system. Achieved results were 1.8 MW in electricity savings as well as the added benefit of reduced cycling. This saving results in a cost saving of R3.7 million per annum. The problems and shortfalls of the system are also discussed as well as possible future directions for moving forward. / MIng (Computer and Electronic Engineering), North-West University, Potchefstroom Campus, 2014

Compressed air makes up an important part of South African precious metal mining processes. Rising operational costs in the struggling mining sector increased the interest of the power utility, Eskom, and mine management in achievable electrical energy savings. Demand side management initiatives, funded by Eskom, realised a significant improvement in electrical energy efficiency of compressed air networks. Supply side interventions further aided optimisation by lowering operational costs. Previous research identified the need for integrating compressed air supply and demand side initiatives. Automated compressor control systems were needed in industry to realise missed opportunities due to human error on manual control systems. Automatic systems were found to be implemented in the industry, but missed savings opportunities were still encountered. This was due to the static nature of these control systems, requiring human intervention from skilled artisans. A comprehensive system is required that can adjust dynamically to the ever-changing demand and other system changes. Commercially available simulation software packages have been used by various mine groups to determine an optimal control philosophy. Satisfactory results were obtained, but the simulations were still based on static control inputs. No simulation system was found that could solve and optimise a system based on real-time instrumentation feedback. By combining simulation capabilities with dynamic control in real time, advanced optimisation could be achieved. Development was done on the theoretical design of the system, where mathematical calculations and the accuracy of the system were evaluated. This study proved that the new controller was viable and, as a result, the development of a fully dynamic control Automation of compressor networks through a dynamic control system iii system incorporating the verified mathematical models followed. All of this was done following a theoretical approach. Intricate control requirements on the supply side were evaluated to determine the impact of new intelligent compressor control strategies. It was found that improved compressor control realised an additional 6.2% electrical energy saving on top of existing savings initiatives. Practical limitations and human perception issues were also addressed. Financial cost-benefit analyses were used to evaluate the viability of using automated compressor control. Ample maintenance data obtained from two leading mining companies was used to evaluate the impact of increased stopping and starting of compressors. Financial cost savings from electrical energy efficiency control strategies were found to considerably outweigh the minimal increase in compressor maintenance. Savings potential on deep-level mines proved to be in the order of 5% of the baseline consumption. When these results are extrapolated to the remaining 22 South African deep-level gold and platinum mines already subjected to demand side management initiatives, potential savings of 12.67 MW can be realised. Based on the Eskom 2014/2015 Megaflex tariff structure, the financial cost saving from 12.67 MW is R61 million. / PhD (Electrical Engineering), North-West University, Potchefstroom Campus, 2015

Submitted in fulfillment of the requirements of the degree of Master of Engineering: Mechanical Engineering, Durban University of Technology, Durban, South Africa, 2016. / Pneumatic tyres are of major importance in the modern life. It is estimated that over one billion tyres are manufactured worldwide annually. The manufacturing process is rather power consuming one, mainly to a curing operation taking place in a press dome. The tyre compression mould warm up process is a powerful heat transfer technique. Saturated steam is fed into a press dome to directly transfer heat energy into the prismatic container through convection and conduction heat transfer. This dissertation concerns the work done at Apollo-Dunlop tyres, the tyre compression mould warm up process was optimised to reduce the high energy cost. A heat transfer numerical analysis was carried out to investigate the steam quantity required to warm up the tyre compression mould from an ambient temperature ( ) to operational temperature ( ). Thereafter, an experimental work was performed to investigate the actual duration required to warm up the tyre compression mould to the operational temperature. This was achieved by establishing a temperature profile of the tyre compression mould during the warm up session. The numerical analysis and the experimental results were correlated to create a new warm up process with reduced steam consumption and warm up duration. The new warm up process was tested and the results are furnished in this study (see Appendix B for the performance results sheet). Apollo-Dunlop tyres (Pty) Ltd reduced a five hour tyre compression mould warm up process to a three hour process. The implementation of the proposed reduced warm up process occurred after the research work in this paper was presented to Apollo-Dunlop tyres (Pty) Ltd board members. This work was acknowledged by the company management and a new technological process has been implemented (Appendix A for the relevant documents, note: the specifications sheet show the warm-up duration as four hours, but the actual operational warm up duration is five hours). A cost saving analysis on energy usage was carried out to indicate that Apollo–Dunlop tyres will currently save approximately around about 0.64 million per year after implementing this study. / M

Growing demand for electricity forces suppliers to expand their generation capacity. Financing these expansion programmes results in electricity cost increases above inflation rates. By reducing electricity consumption, additional supply capacity is created at lower costs than the building of conventional power stations. Therefore, there is strong justification to reduce electricity consumption on the supplier and consumer side. The mining and industrial sectors of South Africa consumed approximately 43% of the total electricity supplied by Eskom during 2012. Approximately 10% of this electricity was used to produce compressed air. By reducing the electricity consumption of compressed air systems, operating costs are reduced. In turn this reduces the strain on the South African electricity network. Previous energy saving projects on mine compressed air systems realised savings that were not always sustainable. Savings deteriorated due to, amongst others, rapid employee turnover, improper training, lack of maintenance and system changes. There is therefore a need to improve projects that have already been implemented on mine compressed air systems. The continuous improvement of equipment (such as improved control valves) and the availability of newer technologies can be used to improve existing energy saving strategies. This study provides a solution to reduce the electricity consumption and operating costs of a deep level mine compressed air system. This was achieved by modernising and improving an existing underground compressed air saving strategy. This improvement resulted in a power saving of 1.15 MW; a saving equivalent to an annual cost saving of R4.16 million. It was found that the improved underground compressed air DSM project realised significant additional electrical energy savings. This resulted in ample cost savings to justify the implementation of the project improvements. It is recommended that opportunities to improve existing electrical energy saving projects on surface compressed air systems are investigated. / MIng (Mechanical Engineering), North-West University, Potchefstroom Campus, 2014

Renewable Energy is by nature intermittent and matching the supply of energy to specific time dependent demand poses huge challenges. Energy storage is a useful tool in handling this temporal disparity, although except for regions very suitable for pumped hydroelectric storage schemes, it suffers from being technically difficult to implement and costly as a result. This study investigates the potential benefits offered by various scales of energy storage to different types of renewable energy generation. It also explores the economic drivers behind energy storage operating as part of an electricity spot market. A stochastic optimisation algorithm for determining the maximum possible arbitrage revenue available to energy storage devices is presented and schedule of operation of storage acting in this manner is analysed. The schedule of operation for maximising the revenue is compared to the schedule of operation for minimising the fuel cost to the network and it is demonstrated that because prices are more volatile than the demand which drives them, storage devices do not always act to decrease the fuel cost to the network. It is shown that storage behaving in the right manner can offer significant benefits to electricity systems, and increases the usage of base-load generation, reducing peak electricity demands and the need for expensive peaking plants. The value of storage also increases as the penetration of renewable energy generation increases, although the current electricity market framework is perhaps not the best way to encourage this behaviour. Advanced Adiabatic Compressed Air Energy Storage (AA-CAES) is also identified as a theoretical storage option which deserves further scrutiny. Using thermodynamic modelling the efficiency of this type of system is estimated in the range of 63-67%, and we suggest that this may be increased closer to 73% by using direct contact heat exchangers rather than indirect contact heat exchangers (and a separate thermal fluid), as described in the currently available literature. However, dealing with large pressure ranges (leading to large variations in pressure ratios) encountered in the expansion process is a problematic area which will have to be resolved before this type of system can be constructed with “off-the-shelf” components. Some small scale experiments are used to gain valuable insights into a AA-CAES system. While these suffer from a very low overall efficiency, they highlight the effect of variable pressure ratio on expander efficiency. We conclude that AA-CAES is thermodynamically sound and will be achieved one of two ways: either through the construction of expanders that can work with high efficiency over large pressure ratios, or by resolving the engineering issues with maintaining a constant storage pressure.

<p>U radu se proučava kvalitet vazduha pod pritiskom iz aspekta održive proizvodnje. Zahtevani kvalitet vazduha postiže se primenom filtera<br />i sušača. Filteri vazduha izazivaju pad pritiska, koji ako se smanji,<br />smanjuje se i ukupna količina proizvedenog vazduha pod pritiskom, čime<br />se povećava energetska efikasnost. Utvrđuje se povezanost primene<br />različitih filtera i pada pritiska, uz poštovanje kvaliteta vazduha.<br />Osim toga, analiziran je kondenzat, koji se pri filtraciji javlja u<br />sistemu, i kreirane su odgovarajuće preporuke za njegovo odlaganje, jer<br />se on svrstava u opasan otpad zbog prisustva ulja.</p> / <p>This paper examines the quality of compressed air from the aspect of<br />sustainable production. The required air quality is achieved by using filters<br />and dryers. Air filters generate the pressure drop, which, if reduced, reduces<br />the total volume of produced compressed air, which lead to increase in<br />energy efficiency. Connections between the application of different filters and<br />pressure drops with respect to quality are explored. In addition, the<br />condensate from the compressed air system is analysed, and appropriate<br />recommendations for its disposal are created because it is classified as<br />hazardous waste due to the presence of oil.</p>

A escassez de água e a grande geração de esgoto doméstico com necessidade de tratamento estimulam o uso de águas residuárias na agricultura. A irrigação por gotejamento caracteriza-se como um sistema seguro para esta finalidade, mas possui como barreira tecnológica o entupimento dos gotejadores. Neste trabalho, objetivou-se selecionar modelos de gotejadores e manejos mitigadores do entupimento por uso de água residuária oriunda de tratamento secundário de esgoto doméstico. Desenvolveu-se o estudo em três etapas: (I) a caracterização de 15 modelos de gotejador novos, (II) a préseleção dos emissores e (III) a seleção da combinação manejo e modelo. Os manejos foram controle, cloração a 0,5 mg L-1 de cloro residual livre ao final da irrigação medido ao final do sistema, ar comprimido a 1,96 kPa na entrada dos emissores e a combinação de cloração e ar comprimido, utilizando-se filtragem de areia (De = 0,59 mm), disco (120 mesh) e tela (200 mesh) em todos os tratamentos. Procederam-se avaliações de vazão e cálculos de coeficiente de variação de vazão (CVq) e de grau de entupimento (GE). Os modelos apresentaram coeficiente de variação de fabricação aceitável e diferentes sensibilidades ao entupimento. O entupimento foi parcial, ocorreu de maneira desuniforme, independente da uniformidade de distribuição de água (UD) do emissor novo, e surgiu pela formação de biofilme bacteriano associado a sólidos dissolvidos. Houve aumentos de vazão em alguns modelos. A cloração reduziu o grau de entupimento ao longo do tempo e evitou o entupimento total em emissores. O modelo B associado à cloração apresentou a maior probabilidade de encontrar emissores na faixa de 5 % de variação de vazão em relação aos novos e o modelo M associado à filtragem ou a tratamentos com ar comprimido, as menores probabilidades. Os manejos mostraram-se semelhantes quanto ao GE e ao CVq e obtiveram-se valores de UD inferiores a 60 %, CVq superiores a 20 % e GE superiores a 5 %. Finalmente, de acordo com o objetivo, selecionou-se o modelo B associado à cloração como a combinação que melhor atenuou o entupimento dos emissores. / The sustainable management of water resources, given the current and projected severe water shortages, requires that appropriate methods of water usage be implemented. One of these is the application of treated wastewater to agricultural land using drip irrigation systems, which is safe and among the most resource efficient methods of irrigation. However, the use of drip irrigation with wastewater is constrained by the potential for clogging in the emitters. To elucidate the mechanism of clogging, fifteen drip emitters models from different manufacturers were tested with secondary treated wastewater in the laboratory and two field experiments were conducted to evaluate emitters and treatments according to the degree of clogging (DC) and flow rate coefficient of variation (CVq). The treatments were control (filtrage only), chlorination (0.5 mg L-1 free residual chlorine injected at the end of each irrigation cycle), compressed air (1.96 kPa in the inlet drippers) and the chlorine and compressed air combination. The manufacture coefficient of variation was acceptable and different clogging susceptibility. The clogging was partial, non-uniform and was caused by biofilm with dissolved solids. Some drippers with overflow rates were noted. The chlorination decreased clogging overtime and reduced the complete clogging. The dripper model B (pressure compensated, flat and inserted in the line, with rectangular elastic membrane over a 30 mm passageway, 0.8 mm narrowest aperture, 1.61 L h-1 under 98 kPa) with chlorination was identified as having the best performance, with the highest number of emitters with a flow rate within five percent of the flow rate when new, and the dripper model M with chlorination was the worst performance with the lowest percent. The filtrage, chlorine and air treatments did not have a statistically significant affect in the DC or CVq. Distribution uniformities higher than 60 %, CVq higher than 20 % and DC higher then 5 % were found. Finally, according to the purposed, It was selected the dripper model B with chlorination as the best combination to mitigate the clogging