Wireless access networks today consume 0.5 percent of the global energy. Rapidly growing demand for new services and ubiqutious connectivity, will further increase the energy consumption. This situation imposes a big challenge for mobile operators not only due to soaring cost of energy, but also increasing concern for global warming and sustainable development. This thesis focuses on the energy efficiency issue at the system level and studies how to incorporate energy-awareness into the design of future wireless access networks. The main contributions have been given in the areas of energy efficiency assessment, architectural and operational solutions, and total cost of investment analysis. The precise evaluation of energy efficiency is the first essential step to determine optimized solutions where metrics and models constitute the two key elements.We show that maximizing energy efficiency is not always equivalent to minimizing energy consumption which is one of the main reasons behind the presented contradictory and disputable conclusions in the literature. Further we indicate that in order to avoid the debatable directions, energy efficient network design problems should be formulated with well defined coverage and capacity requirements. Moreover, we propose novel backhaul power consumption models considering various technology and architectural options relevant for urban and rural environments and show that backhaul will potentially become a bottleneck in future ultra-high capacity wireless access networks. Second, we focus on clean-slate network deployment solutions satisfying different quality of service requirements in a more energy efficient manner. We identify that the ratio between idle- and transmit power dependent power consumption of a base station as well as the network capacity requirement are the two key parameters that affect the energy-optimum design.While results show that macro cellular systems are the most energy efficient solution for moderate average traffic density, Hetnet solutions prevail homogeneous deployment due to their ability to increase the capacity with a relatively lower energy consumption and thus enable significant energy savings in medium and high capacity demand regions. Moreover, we investigate the energy saving potential of short-term energy aware management approach, i.e., cell DTX, taking advantage of low resource utilization in the current networks arising from strict QoS requirements. With the help of developed novel quantitative method, we show that Cell DTX brings striking reduction in energy consumption and further savings are achievable if the networks are designed taking into account the fact that network deployment and operation are closely related. Finally, we develop a general framework for investigating the main cost elements and for evaluating the viability of energy efficient solutions.We first reveal the strong positive impact of spectrum on both energy and infrastructure cost and further indicate that applying sustainable solutions might also bring total cost reduction, but the viability highly depends on unit cost values as well as the indirect cost benefits of energy efficiency. Results obtained in this dissertation might provide guidelines for the network designers to achieve future high-capacity and sustainable wireless access networks. / <p>QC 20140505</p>

Den här rapporten har skrivits som en del av ett examensarbete på energiingenjörsprogrammet på Högskolan i Halmstad under våren 2014. Examensarbetet har genomförts i samarbete med AB Färdig Betong samt ÅF Infrastructure AB i Göteborg. Syftet med projektet är att undersöka energibesparingspotentialen hos AB Färdig Betongs produktionsanläggning på Ringön i Göteborg. Projektet har inneburit en energikartläggning av en industriell produktionsanläggning för lösbetong. Utgångspunkt för energikartläggningen har varit energiledningssystemet ISO 50001, med målsättningen att ta fram en teknisk energikartläggningsrapport i enlighet med standarden. Anläggningen har analyserats ur ett energibesparingsperspektiv. Data- och informationsinsamling samt mätningar har genomförts för att ta fram indata som beräkningsunderlag. Genom beräkningar har sedan möjliga energibesparingspotentialer och åtgärdsförslag tagits fram. Den totala energibesparingspotentialen för anläggningen innebär en besparing på 223 MWh av anläggningens totala energianvändning på 857 MWh år 2013, vilket motsvarar en minskning med omkring 26 %. Allmänna slutsatser är bland annat att all produktionsutrustning bör placeras inom klimatskalet, att all uppvärmning bör vara temperaturreglerad samt att ett mer långsiktigt energiperspektiv behövs i anläggningen. Energibesparingsmöjligheterna för anläggningen är mycket goda och investeringskostnaderna är i allmänhet låga. / This report has been written as part of a degree project at the Bachelor’s programme in energy engineering at Halmstad University in the spring of 2014. The project was made in collaboration with AB Färdig Betong and ÅF Infrastructure AB in Gothenburg. The project aims to investigate the potential energy savings of AB Färdig Betong’s production plant at Ringön in Gothenburg. The project was to make an energy audit of an industrial production plant for concrete. The starting point for the energy audit has been the ISO 50001 energy management system with the aim to develop a technical energy audit report in accordance with the standard. The plant has been analyzed from an energy perspective. Measurements, collection of data and information has been carried out to develop the input data basis. Through calculations, potential energy savings and proposals for actions were developed. Among the four largest energy saving potentials, there are two that have no investment cost at all. The total of all potentials represent a saving of 26 % of the total plant energy consumption of 857 MWh in 2013. General conclusions include that all production should be located within the building, that all heating should be temperature regulated and that a long term perspective on energy use is needed.

A rapid growth in the national electricity demand is placing an ever-increasing demand on the national electricity supply utility, Eskom. Projections show that the load demand in South Africa may exceed the installed capacity by as early as 2007. This is mainly due to the increase in demand in the residential sector as a result of the electrification of rural and previously disadvantaged communities. However, the industrial and commercial sectors also have a role in this increase. In an attempt to reduce the demand for electricity Eskom has adopted its Demand Side Management (DSM) initiative. This initiative is aimed at lowering the electricity demand in peak times through energy efficiency (EE) or load shift, out of peak demand times. Eskom is implementing the DSM strategy by financing Energy Service Companies (ESCOs) to reduce the demand load of major electricity end-users during peak times. Buildings consume a large percentage of the total energy supply in the world. Most of the energy consumed in buildings is used by the heating, ventilation and air-conditioning (HVAC) systems, as well as lighting. However, a large potential for energy savings exists in buildings. Studies have shown that up to 70% of the electricity consumption of a building can be saved through retrofit studies. However, to capitalise on these opportunities, the ESCOs require tools and procedures that would enable them to accomplish energy savings studies quickly and efficiently. It should be a holistic approach to the typical ESCO building audit. A study of current available software programs showed the lack of holistic tools aimed specifically at retrofit audits, and therefore also the need for such a program. The building simulation program most suited to the retrofit study was chosen and it was used in a retrofit audit. By emulating a retrofit audit with this software, its performance in the field, both positive and negative, could be established. With the experience gained from the retrofit study, as well as input from ESCOs in the industry, a need for such a retrofit tool was established. The simulation program that was tested in the retrofit study is the tool Quickcontrol, as well as the newer version of the program, entitled QEC. The case study showed that even though these packages are well suited to ESCO work, they have certain drawbacks in view of the holistic project approach. The ESCOs require a simple, fast, and integrated procedure for energy audits. This procedure should be embodied in a software program. This study proposes a new integrated procedure for energy audits and the analyses of buildings, in the form of a software tool. This new tool is geared towards the ESCO building audit, in both South A6ica and internationally. It is designed to enable a diplomate engineer to accomplish a building energy and retrofit analysis in two weeks, leading the user through all the main project steps, from data acquisition to writing of the final project report. This is a significant improvement, since it normally takes 50 man-days for an experienced and trained engineering team to complete a full building audit. This tool was used in a case study to test its validity and accuracy. It was found that certain situations would arise in which the criteria that were set for the program would not be adequate. The results from the case study were favourable and satisfied the criteria that were set for the procedure. / Thesis (Ph.D. (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2004.

Unreliable and unsustainable electricity supply has been experienced in South Africa since 2007. Eskom implemented Demand Side Management (DSM) as a short-term solution to alleviate this problem. Several compressed-air DSM projects were implemented to help reduce the strain on the electrical network. Compressed air is an integral part of production in deep-level mining, and is extensively utilised. Problems are encountered with the effective management and repairing of leaks, since the majority of mines have little to no procedures in place for leak management. Awareness of the condition of the compressed-air system and leaks needed to be created at management level in order to achieve the best results. The purpose of this study is to investigate the effect of proper leak management on compressed-air systems in the mining industry. Peak-clipping DSM projects implemented in the mining industry were used for evaluation of results. Contribution to the sustainability of compressed-air DSM projects savings through successful leak documentation was the prime focus of this study. This was achieved through the development of a Compressed Air Leakage Documentation System (CALDS). This entailed the electronic field-data capture and record keeping of field data, using rugged PDA devices suitable for the extreme environmental conditions encountered in deep-level mining. Report generation on the status of detected leaks created awareness of compressedair- system performance and leak-repair tracking at management level. Audible detection was sufficient for this study, since the focus was on the larger more-severe leaks. Leaks were expressed in monetary terms to indicate the severity. It was found that successful management of leaks could contribute to an increase of as much as 85% in project savings. The results also showed that creating awareness through documentation of leaks, and the effect this has on the system, resulted in regular repairing of these leaks. Sustainability of projects was maintained during an evaluation period of ten months, with projects achieving on average 125% of target savings. The study showed that effective reporting on compressed-air leaks resulted in increased system efficiency and sustainable DSM project savings. It was also seen that leak detection by outsourced companies did not necessarily result in financial savings. When the mine took responsibility for its own leak detection and repairs, significant savings were realised. / Thesis (M.Ing. (Electrical and Electronic Engineering))--North-West University, Potchefstroom Campus, 2011.

Demand Side Management (DSM) is one of the most viable and sustainable short term methods to address the shortfall in electricity generation in South Africa. This is because DSM projects can be implemented relatively quickly and inexpensively when compared with alternative generation options. This specifically applies to the mining industry. South African mines presently consume 15% of Eskom-generated electricity. Mine compressed air systems are some of the biggest users, consuming approximately 21% of mine electricity consumption. Electricity savings on compressed air systems are therefore important. With this study, various Energy Efficiency methods on compressed air systems were investigated. These methods include variable speed drives on compressor motors, temperature control of compressor discharge, minimising pressure drops in the air distribution systems, eliminating compressed air leaks, and optimising compressor selection and control. The most efficient strategies were identified, taking into account factors such as financial viability, sustainability, and ease of implementation. The best strategies were found to be the optimised control and selection of compressors, minimising compressed air leaks, and the optimal control of system pressure. These strategies were implemented and tested on large compressed air systems in gold and platinum mines. Savings of between 10% and 35% on the maximum demand of the systems were achieved. In present monetary terms this translates to as much as R108 million savings for the mines per year at the end of 2009 tariffs. If total mine compressed air electricity consumption can reduce by 30%, it will result in nearly a 1% reduction in total Eskom demand. This shows that mine compressed air savings can make a significant contribution to the drive for Energy Efficiency in South Africa. / Thesis (M.Ing. (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2010.

The demand for forensic social work as a specialist field is increasing rapidly, due to the increasing moral decline of the community and consequent higher demands set to generic social workers. Amendments to existing acts as well as the development of new legislation, lead to more opportunity for the prosecution of the perpetrator, and therefore a higher utilization of the forensic social worker. A need was experienced to do research regarding the gaps experienced by social workers or any other workers who are currently executing forensic assessments with the sexually traumatised child. The aim of the investigation was to determine which gaps social workers experience in the field when assessing a child forensically. A recording procedure was used to obtain qualitative as well as quantitative data. A purposive sampling was used were interviews were held with five participants to obtain the data. A selfdeveloped questionnaire was used as measuring instrument. It is clear from the findings that there are definite gaps within the field of forensic social work and the need of further research within the field of forensic social work in South Africa is highlighted. / Thesis (MIng (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2012.

Data aggregation is an important technique in wireless sensor networks. The data are gathered together by data fusion routines along the routing path, which is called data-centralized routing. We propose a localized, Delay-bounded and Energy-efficient Data Aggregation framework(DEDA) based on the novel concept of DEsired Progress (DEP). This framework works under request-driven networks with realistic MAC layer protocols. It is based on localized minimal spanning tree (LMST) which is an energy-efficient structure. Besides the energy consideration, delay reliability is also considered by means of the DEP. A node’s DEP reflects its desired progress in LMST which should be largely satisfied. Hence, the LMST edges might be replaced by unit disk graph (UDG) edges which can progress further in LMST. The DEP metric is rooted on realistic degree-based delay model so that DEDA increases the delay reliability to a large extent compared to other hop-based algorithms. We also combine our DEDA framework with area coverage and localized connected dominating set algorithms to achieve two more resilient DEDA implementations: A-DEDA and AC-DEDA. The simulation results confirm that our original DEDA and its two enhanced variants save more energy and attain a higher delay reliability ratio than existing protocols.

This research examines energy poverty in the Daniel McIntyre and St. Matthews (DMSM) neighbourhoods in the city of Winnipeg. Energy poverty, defined as households spending more than 6% of their income on energy expenditures, affects as many as 50% of households in DMSM. Energy poverty can be alleviated through energy retrofits for dwellings such as weather stripping; increasing insulation in exterior walls, the attic and basement; and installing a high-efficiency furnace. The recommendations include: establishing consistent housing and energy efficiency policies; increasing the flexibility of utility on-bill financing; levying the necessary capital for energy retrofits through municipal financing mechanisms; increasing the knowledge and capacity of local residents; increasing the knowledge and capacity of local contractors for sustainable design and construction; creating a provincial strategy to increase the energy efficiency of social housing; developing low-income energy efficiency programs for rental properties; and increasing access to renewable energy sources.

Unreliable and unsustainable electricity supply has been experienced in South Africa since 2007. Eskom implemented Demand Side Management (DSM) as a short-term solution to alleviate this problem. Several compressed-air DSM projects were implemented to help reduce the strain on the electrical network. Compressed air is an integral part of production in deep-level mining, and is extensively utilised. Problems are encountered with the effective management and repairing of leaks, since the majority of mines have little to no procedures in place for leak management. Awareness of the condition of the compressed-air system and leaks needed to be created at management level in order to achieve the best results. The purpose of this study is to investigate the effect of proper leak management on compressed-air systems in the mining industry. Peak-clipping DSM projects implemented in the mining industry were used for evaluation of results. Contribution to the sustainability of compressed-air DSM projects savings through successful leak documentation was the prime focus of this study. This was achieved through the development of a Compressed Air Leakage Documentation System (CALDS). This entailed the electronic field-data capture and record keeping of field data, using rugged PDA devices suitable for the extreme environmental conditions encountered in deep-level mining. Report generation on the status of detected leaks created awareness of compressedair- system performance and leak-repair tracking at management level. Audible detection was sufficient for this study, since the focus was on the larger more-severe leaks. Leaks were expressed in monetary terms to indicate the severity. It was found that successful management of leaks could contribute to an increase of as much as 85% in project savings. The results also showed that creating awareness through documentation of leaks, and the effect this has on the system, resulted in regular repairing of these leaks. Sustainability of projects was maintained during an evaluation period of ten months, with projects achieving on average 125% of target savings. The study showed that effective reporting on compressed-air leaks resulted in increased system efficiency and sustainable DSM project savings. It was also seen that leak detection by outsourced companies did not necessarily result in financial savings. When the mine took responsibility for its own leak detection and repairs, significant savings were realised. / Thesis (M.Ing. (Electrical and Electronic Engineering))--North-West University, Potchefstroom Campus, 2011.

Demand Side Management (DSM) is one of the most viable and sustainable short term methods to address the shortfall in electricity generation in South Africa. This is because DSM projects can be implemented relatively quickly and inexpensively when compared with alternative generation options. This specifically applies to the mining industry. South African mines presently consume 15% of Eskom-generated electricity. Mine compressed air systems are some of the biggest users, consuming approximately 21% of mine electricity consumption. Electricity savings on compressed air systems are therefore important. With this study, various Energy Efficiency methods on compressed air systems were investigated. These methods include variable speed drives on compressor motors, temperature control of compressor discharge, minimising pressure drops in the air distribution systems, eliminating compressed air leaks, and optimising compressor selection and control. The most efficient strategies were identified, taking into account factors such as financial viability, sustainability, and ease of implementation. The best strategies were found to be the optimised control and selection of compressors, minimising compressed air leaks, and the optimal control of system pressure. These strategies were implemented and tested on large compressed air systems in gold and platinum mines. Savings of between 10% and 35% on the maximum demand of the systems were achieved. In present monetary terms this translates to as much as R108 million savings for the mines per year at the end of 2009 tariffs. If total mine compressed air electricity consumption can reduce by 30%, it will result in nearly a 1% reduction in total Eskom demand. This shows that mine compressed air savings can make a significant contribution to the drive for Energy Efficiency in South Africa. / Thesis (M.Ing. (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2010.