Low power and Lossy Networks (LLNs) such as wireless sensor networks are currently used in many important applications fields such as remote environment monitoring and target tracking. This deployment has been enabled by the availability, especially in recent years, of embedded micro-controller devices that are smaller and cheaper. These devices are equipped with wireless interfaces, with which they can communicate with each other to form a network. In this thesis we focus on studying the energy consumption of reliable transport protocols over LLNs. Recently, much research has been carried out to improve the reliability and the congestion control on low power networks. Some of these works have considered TCP inappropriate for this kind of networks. Indeed, the idea of deploying TCP was rejected due to its header overhead, its end-to-end retransmission mechanism, its large rate of acknowledgment, and the impact of the lower layers fragmentation on the energy consumption. Nonetheless, the use of standard TCP/IP protocols offers the advantage of a seamless connectivity between the wireless network and the Internet. TCP allows easily the use of standard applications (HTTP, SSH) for some tasks like reprogramming of nodes or firmware updates, without the need of deploying complex proxies in border routers. In the first part of this work, we study the energy consumption of TCP and the ways that reduce its energy consumption. We study one of the proposed TCP algorithms to reduce the end-to-end retransmissions cost and we propose some improvements that allow it to reduce the energy consumption. Then, we study the compression of the TCP header over low-power and lossy networks and we consider IPv6 over Low power Wireless Personnel Area Networks (6LoWPAN) as an example. We propose a new TCP header compression algorithm that reduces the TCP header size to about six bytes. In the second part, we propose a mathematical model that allows to estimate the energy consumption of wireless nodes. Using the model, we study the tradeoff between sending long and short TCP segments and their impact on the energy consumption. Finally, we study the impact of a new fragment recovery mechanism on the energy performance of TCP.

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

The energy performance in buildings is influenced by many factors, such as ambient weather conditions, building structure and characteristics, occupancy and their behaviors, the operation of sub-level components like Heating, Ventilation and Air-Conditioning (HVAC) system. This complex property makes the prediction, analysis, or fault detection/diagnosis of building energy consumption very difficult to accurately and quickly perform. This thesis mainly focuses on up-to-date artificial intelligence models with the applications to solve these problems. First, we review recently developed models for solving these problems, including detailed and simplified engineering methods, statistical methods and artificial intelligence methods. Then we simulate energy consumption profiles for single and multiple buildings, and based on these datasets, support vector machine models are trained and tested to do the prediction. The results from extensive experiments demonstrate high prediction accuracy and robustness of these models. Second, Recursive Deterministic Perceptron (RDP) neural network model is used to detect and diagnose faulty building energy consumption. The abnormal consumption is simulated by manually introducing performance degradation to electric devices. In the experiment, RDP model shows very high detection ability. A new approach is proposed to diagnose faults. It is based on the evaluation of RDP models, each of which is able to detect an equipment fault.Third, we investigate how the selection of subsets of features influences the model performance. The optimal features are selected based on the feasibility of obtaining them and on the scores they provide under the evaluation of two filter methods. Experimental results confirm the validity of the selected subset and show that the proposed feature selection method can guarantee the model accuracy and reduces the computational time.One challenge of predicting building energy consumption is to accelerate model training when the dataset is very large. This thesis proposes an efficient parallel implementation of support vector machines based on decomposition method for solving such problems. The parallelization is performed on the most time-consuming work of training, i.e., to update the gradient vector f. The inner problems are dealt by sequential minimal optimization solver. The underlying parallelism is conducted by the shared memory version of Map-Reduce paradigm, making the system particularly suitable to be applied to multi-core and multiprocessor systems. Experimental results show that our implementation offers a high speed increase compared to Libsvm, and it is superior to the state-of-the-art MPI implementation Pisvm in both speed and storage requirement.

With the current trend of CO2 mitigation in process industries, the primary goal of this thesis is to promote biomass as an energy and reduction agent source to substitute fossil sources in the steel industry. The criteria for this substitution are that the steel process retains the same function and the integrated energy efficiency is as high as possible. This work focuses on advanced gasification of biomass and waste for substitution of fossil fuels in steel industry heat treatment furnaces. To achieve this, two approaches are included in this work. The first investigates the gasification performance of pretreated biomass and waste experimentally using thermogravimetric analysis (TGA) and a pilot plant gasifier. The second assesses the integration of the advanced gasification system with a steel heat treatment furnace. First, the pyrolysis and char gasification characteristics of several pretreated biomass and waste types (unpretreated biomass, steam-exploded biomass, and hydrothermal carbonized biomass) were analyzed with TGA. The important aspects of pyrolysis and char gasification of pretreated biomass were identified. Then, with the objective of studying the gasification performance of pretreated biomass, unpretreated biomass pellets (gray pellets), steam-exploded biomass pellets (black pellets), and two types of hydrothermal carbonized biomass pellets (spent grain biocoal and horse manure biocoal) were gasified in a fixed bed updraft gasifier with high-temperature air/steam as the gasifying agent. The gasification performance was analyzed in terms of syngas composition, lower heating value (LHV), gas yield, cold gas efficiency (CGE), tar content and composition, and particle content and size distribution. Moreover, the effects on the reactions occurring in the gasifier were identified with the aid of temperature profiles and gas ratios. Further, the interaction between fuel residence time in the bed (bed height), conversion, conversion rate/specific gasification rate, and superficial velocity (hearth load) was revealed. Due to the effect of bed height on the gasification performance, the bed pressure drop is an important parameter related to the operation of a fixed bed gasifier. Considering the limited studies on this relationship, an available pressure drop prediction correlation for turbulent flow in a bed with cylindrical pellets was extended to a gasifier bed with shrinking cylindrical pellets under any flow condition. Moreover, simplified graphical representations based on the developed correlation, which could be used as an effective guide for selecting a suitable pellet size and designing a grate, were introduced. Then, with the identified positive effects of pretreated biomass on the gasification performance, the possibility of fuel switching in a steel industry heat treatment furnace was evaluated by effective integration with a multi-stage gasification system. The performance was evaluated in terms of gasifier system efficiency, furnace efficiency, and overall system efficiency with various heat integration options. The heat integration performance was identified based on pinch analysis. Finally, the efficiency of the co-production of bio-coke and bio-H2 was analyzed to increase the added value of the whole process. It was found that 1) the steam gasification of pretreated biomass is more beneficial in terms of the energy value of the syngas, 2) diluting the gasifying agent and/or lowering the agent temperature compensates for the ash slagging problem in biocoal gasification, 3) the furnace efficiency can be improved by switching the fuel from natural gas (NG) to syngas, 4) the gasifier system efficiency can be improved by recovering the furnace flue gas heat for the pretreatment, and 5) the co-production of bio-coke and bio-H2 significantly improves the system efficiency. / <p>QC 20160825</p>

<p>Na regionalnom planu evidentne su potrebe za visokim energetskim performansama, promenom strukture izvora energije i modernizacijom energetske infrastrukture, što zahteva novi i inoviran razvojni put praćen korenitim promenama i sistemskim pristupom a u skladu sa novim društvenim, ekonomskim i tehnološkim prilikama. Takav razvojni put bi učinio regionalne energetske sisteme efikasnim i održivim i predstavlja energetsku tranziciju. Disertacija kombinuje različite tehnike i pristupe za analizu mnogih aspekata razvoja regionalnih energetskih sistema od kojih su najvažniji povećanje energetske efikasnosti u sistemima proizvodnje energije, diversifikaciju izvora energije (kombinovanje obnovljivih i neobnovljivih izvora energije) i poboljšanja u energetskoj infrastrukturi (nova i savremena tehnološka rešenja).</p> / <p>At the regional level, there are evident needs for a high energy performance, change the structure of energy sources and modernization of the energy infrastructure, which requires a new and innovative development path, followed by fundamental changes and systemic approach in accordance with the new social, economic and technological conditions. Such a development path would make regional energy systems efficient and sustainable and represents the energy transition.<br />The thesis combines a variety of techniques and approaches for the analysis of many aspects of the development of regional energy systems, but especially increasing of energy efficiency in energy production systems, diversification of energy sources (a combination of renewable and non-renewable energy sources) and improvements in energy infrastructure (new and modern technological solutions).</p>

<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>

<p>Modern sensing apps require continuous and intense computation on data streams. Unfortunately, mobile devices are failing to keep pace despite advances in hardware capability. In contrast to powerful system-on-chips that rapidly evolve, battery capacities merely grow. This hinders the potential of long-running, compute-intensive sensing services such as image/audio processing, motion tracking and health monitoring, especially on small, wearable devices. </p><p>In this thesis, we present three pieces of work that target at improving the energy efficiency for mobile sensing. (1) In the first work, we study heterogeneous mobile processors that dynamically switch between high-performance and low-power cores according to tasks' performance requirements. We benchmark interactive mobile workloads and quantify the energy improvement of different microarchitectures. (2) Realizing that today's users often carry more than one mobile devices, in the second work, we extend the resource boundary of individual devices by prototyping a distributed framework that coordinates multiple devices. When devices share common sensing goals, the framework schedules sensing and computing tasks according to devices' heterogeneity, improving the performance and latency for compute-intensive sensing apps. (3) In the third work, we study the power breakdown of motion sensing apps on wearable devices and show that traditional offloading schemes cannot mitigate sensing’s high energy costs. We design a framework that allows the phone to take over sensing and computation by predicting the wearable's sensory data, when motions of the two devices are highly correlated. This allows the wearable to offload without communicating raw sensing data, resulting in little performance loss but significant energy savings.</p> / Dissertation

Over the last twenty-five years, fuel poverty in England has successfully transitioned from niche academic interest to mandated concern of the state. More recently still, government have opted to charge energy suppliers with primary delivery responsibility for fuel poverty programmes. The original contribution to knowledge made by this thesis is in offering a novel comparative analysis of the potential for the state and energy suppliers to effectively support fuel poor households. This research offers one of the first academic assessments of the new suite of policies championed by the coalition government formed in 2010. It is also amongst the first pieces of work to apply and critically assess the new official metric for fuel poverty, the Low Income, High Costs definition. By assessing delivery choices against the tenets of neoliberalism identified as guiding recent UK governments, the work further takes into account the motivations of policymakers. A diverse methodological approach is applied, incorporating policy evaluation, quantitative analysis, synthesis of existing literature, and professional engagement. This research establishes that in passing the Warm Homes and Energy Conservation Act 2000, politicians did not appreciate the demands of the commitment to eradicate fuel poverty by 2016. Subsequently, supplier obligations initially intended as a means of mitigating climate change have become the primary policy tool for tackling fuel poverty. The evidence presented here suggests, however, that suppliers are inherently poorly suited to this task for a variety of reasons: their access to the data required to successfully identify fuel poor households is limited; they fund activity in a manner that is unavoidably regressive; and the extent to which they are able to deliver programmes more efficiently than the state is, particularly for economic interventions, subject to question. It is consequently argued that, whilst supplier obligations are likely to appeal to an austerity-driven, neoliberal government as an expedient means of keeping expenditure away from the public purse and of limiting the role of the state, this work demonstrates that increased government involvement and greater political ambition will be required if fuel poverty policies are to be successful.

On appelle clinker le matériau obtenu par cuisson de calcaire et d'argile et qui constitue le principal ingrédient du ciment Portland, composant essentiel de la majorité des bétons produits dans le monde. Ce clinker doit être finement broyé avant de pouvoir présenter une réactivité suffisante. La maîtrise des procédés de broyage représente un enjeu considérable pour l'industrie cimentière : il s'agit du premier poste en termes de consommation électrique d'une usine, en partie du fait de l'inefficacité des procédés employés. Les techniques de broyage par compression, apparues au cours des années 80, ont constitué un progrès majeur du point de vue de l'efficacité énergétique, mais la généralisation de leur utilisation a été freinée par des problèmes de maîtrise du procédé, en particulier pour des finesses importantes. L'enjeu de cette thèse est une meilleure compréhension des phénomènes en jeu lors du broyage par compression du clinker, en vue d'un meilleur contrôle des installations industrielles lors de la fabrication de produits fins. Nous nous sommes intéressés en particulier au comportement, du point de vue fondamental, d'un matériau granulaire subissant une fragmentation de ses grains, en nous appuyant sur la simulation numérique d'un Volume Elémentaire Représentatif de matière par les éléments discrets (DEM). Nous avons aussi recherché une loi de comportement permettant de relier contraintes, déformation, et évolution de la taille des particules pour le matériau broyé, en nous appuyant à la fois sur la micromécanique et les techniques d'homogénéisation, et un modèle semi-empirique de bilans de masses. Enfin, un premier pas vers la modélisation du procédé industriel et notamment sa simulation par éléments finis a été esquissé, afin de résorber les difficultés rencontrées en pratique par les industriels / Noindent Clinker is the material obtained by calcination of a mix of clay and limestone, and it is the main component of Portland cement, a crucial ingredient for the majority of concrete used around the world. This clinker must be finely ground to have a sufficient reactivity. Mastering the grinding process is a key issue in the cement industry: it is the first source of expense in terms of electric consumption in a factory, partially because of the overall inefficiency of the process. Compressive grinding techniques, first appeared during the 80's, allow major improvements in terms of energy efficiency, but the general implementation is yet to come, hindered by process control issues, especially for high fineness. The goal of this study is a better understanding of phenomenons occurring during compressive grinding of clinker, in order to provide better process control for industrial installations when dealing with fine products. We particularly choose to study the behaviour, on a fundamental point of view, of a granular material subjected to grain fragmentation, using the numerical simulation of an Elementary Representative Volume of material through Discrete Element Method (DEM). We also looked for a behaviour law able to provide a link between stress, strain, and grain size evolution for the ground material, using at the same time micromechanics and homogenization technique, and a semi-empirical mass balance model. Finally, we made first efforts in the direction of modelling the whole process through numerical simulation by Finite Element Method (FEM), in order to tackle the issue met by the industrials in operations

The aim of my thesis is to create a comprehensive overview of energy law with special focus on its influence on the environment. It especially deals with individual renewable energy sources and their support, construction of facilities utilizing these sources and their impact on the environment. Last but not least, in each chapter I draw attention to recent or expected amendments to relevant legislation. In the first chapter I divide sources of energy into the fossil, nuclear and renewable ones. Besides presenting the basic characteristics of such sources, I also deal with the time period in which the humankind will run out of their supplies, as well as with detrimental effects that their mining and processing have on the environment. Based on the classification included in the Act on the Promotion of Renewable Energy Sources, I continue with classifying the renewable energy sources to wind power, energy of water and solar radiation, geothermal energy, biomass and biogas. I consider their benefits, but also their harmful effects on the environment. Each subchapter also contains a part that deals with the potential of such resources in the Czech Republic. Since Czech energy law is influenced by both international and European laws, I dedicate the next chapter to them. On the level of international...