Dissertations / Theses on the topic '170305 Energy systems and analysis'

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 53-55).
American consumers make a number of decisions that significantly impact their energy use. Some of the most important of these decisions were identified and analyzed for the purpose of including them in a Consumer Energy Decisions Model (CEDM). These decisions included housing choices that affect space heating, water heating, solar photovoltaic and transportation. The CEDM was used to calculate values of recurring and capital cost for all permutations of all the decision components for New York City, Minneapolis and Seattle. These results were analyzed using Pareto plots of recurring versus capital cost. There was a wide range of costs associated with the different solutions, indicating that there is tremendous value in making good energy decisions. The type of vehicle showed the most notable effect on return on investment. Four vehicles were analyzed, a Toyota Camry, Camry Hybrid, Jetta Turbo Diesel (TDI) and an electric Nissan Leaf. The hybrid showed the worst return on investment relative to the Camry with a payback rate of about 9 years, while the TDI and Leaf had payback rates of 1-2 and 6-10 years relative to the Camry, with the added benefits of using less energy and emitting less CO₂. Housing choices were the next most favorable investments, with payback rates around 10 years for the most economical choices. They showed good returns at some points but showed diminishing returns as continued improvements were made. Finally, the solar PV and solar hot water options are bad investments for the sites analyzed, which receive much less sunlight than other parts of the country. The effects of incentives and tax credits were not analyzed in this study.
by Nicholas Daniel Sisler.
S.B.

A análise de caminhos de transferência de energia (TPA na sigla em inglês para Transfer Path Analysis) corresponde a um grupo de métodos numérico/experimental para análise e solução de problemas vibro-acústicos de sistemas lineares invariantes no tempo, sendo seu principal campo de aplicação a indústria automotiva. A TPA é uma técnica que identifica as principais fontes de vibração e ruído, e os caminhos estruturais e acústicos pelos quais são transmitidas para determinados locais de interesse. Conhecendo as fontes de ruído e vibração e os caminhos de propagação é possível propor modificações eficientes em minimizar o ruído/vibração nas regiões de interesse, ou atribuir características desejáveis para tais componentes, envolvendo técnicas de controle passivo e ativo. Este trabalho apresenta um estudo numérico e experimental das técnicas de TPA, utilizando métodos diretos e inversos de determinação de forças operacionais. Estes estudos foram realizados em um mockup de um veículo, com o objetivo de determinar o caminho de maior contribuição para o ruído no interior do protótipo, e a partir deste resultado, propor um sistema de controle ativo para minimizar este ruído interno.
The Transfer Path Analysis (TPA) is a group of numerical/experimental tools for the analysis and troubleshooting of noise and vibration problems in linear time invariant vibroacoustic systems, being the automotive sector its major user. TPA consists of a numerical/experimental analysis that allows the identification of the main noise and vibration sources and the structural/acoustic transfer paths to the Target points. Based on the sources and paths, it is possible to propose modifications that efficiently minimize noise and vibration at the target positions. By means of active control it is possible to modify noise and vibration in order to change, rather than minimize noise and vibration, achieving certain design targets. This work presents a numerical and experimental study of TPA techniques, using direct and inverse operational loads determination methods. These studies were performed on a vehicle mockup, in order to determine the path of greatest contribution to the noise inside the prototype, and from this result, propose an active control system to minimize this internal noise.

Esta tesis presenta un marco teórico novedoso para el análisis energético biofísico de los sistemas socio-ecológicos basado ​​en la teoría de la complejidad. A través de la implementación de MuSIASEM y el análisis relacional, genera información útil para la discusión de políticas en un mundo complejo donde es necesario comprender la sostenibilidad. Además, es útil para impugnar agendas al integrar información no equivalente. Con la integración de la perspectiva funcional y estructural de los sistemas complejos, preguntas como dónde, cómo, por qué y qué son abordadas. Este marco se expone con algunos ejemplos principalmente en el contexto de la Reforma Energética Mexicana. Se puede encontrar que todos los ejemplos cubren una amplia diversidad de sistemas energéticos: biomasa, petróleo y gas, electricidad, y también se argumenta por qué este marco es necesario en comparación con las metodologías más populares en la era contemporánea. Se evita la reducción de la sostenibilidad en simples proporciones. Esta tesis abarca la complejidad al analizar las relaciones no lineales entre los diferentes sistemas socio-ecológicos con el entorno y dentro de ellos mismos. Cómo estas relaciones afectan los diferentes resultados y debido a esto, la anticipación, que es necesaria al hacer planes para los sistemas en disputa. El Primer Capítulo presenta una aplicación del Análisis Relacional y MuSIASEM al metabolismo de una aldea. Esta aldea se encuentra en la transición de la biomasa al combustible fósil, y por lo tanto implica muchos ajustes sobre los elementos funcionales y estructurales de la aldea, debido al cambio de la subsistencia a una aldea basada en el mercado. Dentro del marco analítico elegido, este cambio puede estar relacionado con el cambio del tipo de combustible y los cambios en las prácticas sociales dentro de la economía. El Segundo Capítulo presenta una aplicación del Análisis Relacional y MuSIASEM al sector de petróleo y gas de México; El análisis se utiliza para comentar sobre la actual Reforma Energética en México. Este capítulo trae un análisis biofísico del sector de petróleo y gas en México. Al observar el patrón actual de producción de petróleo y gas en México, se discute si México debería permanecer con el mismo patrón o cambiarlo. También muestra la importancia de complementar el análisis económico con otros tipos de análisis que abordan temas como la soberanía energética, el impacto ambiental y la ubicación geográfica de las actividades económicas. El tercer capítulo presenta una aplicación del análisis relacional y MuSIASEM a la producción de electricidad en México. El análisis de las relaciones entre elementos estructurales y funcionales permite estudiar el nexo entre tierra, energía y emisiones. En particular, aclara las restricciones espaciales que pueden asociarse con la expansión de fuentes alternativas de electricidad. En el pasado, nos emancipamos de la necesidad de utilizar mucha superficie terrestre con fines energéticos mediante el uso de combustibles fósiles. ¿Pero qué tan fuerte es esta emancipación cuando se depende de la electricidad intermitente (eólica y fotovoltaica)? Para responder a esta pregunta, debemos abordar la creciente demanda de importación de gas natural como respaldo de las fuentes de electricidad intermitentes y el posible efecto de rebote de esta solución, si el patrón de consumo sigue siendo el mismo. En el Cuarto Capítulo, demuestro cómo se puede usar la perspectiva funcional para introducir un enfoque novedoso para el análisis de los sistemas energéticos. Esta aplicación muestra la debilidad de las evaluaciones basadas en proporciones (EROEI, por ejemplo) si queremos abordar la complejidad asociada con la sostenibilidad. Las simplificaciones radicales de los indicadores de rendimiento energético (definiciones simplistas de energía) pueden ser útiles para aquellos interesados ​​en "tecno-composturas" pero no para comprender el funcionamiento del sistema. Por esta razón, un análisis sistémico de las relaciones estructurales y funcionales debe incorporarse en el análisis energético si queremos hacerlo útil para la comprensión de la interacción de los sistemas socio-ecológicos.
This thesis presents a novel framework for the biophysical energetic analysis of social-ecological systems based on complexity theory. Through the implementation of MuSIASEM and Relational Analysis, it generates information useful for policy discussion in a complex world where understanding sustainability is necessary. Also, it is useful for contesting agendas at integrating non-equivalent information. With the integration of the functional and structural perspective of complex systems, questions like where, how, why and what are addressed. This framework is demonstrated with some examples mainly in the Mexican Energy Reform context. You can find that al examples cover a broad diversity of energetic systems: biomass, oil and gas, electricity, and it also is argued why this framework is necessary compared to the most popular methodologies in the contemporary era. Reducing sustainability into some ratios is avoided. This thesis embraces complexity by analyzing the non-linear relations among the different social-ecological systems with the environment and within themselves. How these relations affect different outcomes and by these the anticipation which is necessary to understand when making plans for the systems under dispute. The First Chapter presents an application of the Relational Analysis and MuSIASEM to the metabolism of a village. This village is in the transition from biomass to fossil fuel, and thus implies many adjustments over functional and structural elements in the village, due to the change from subsistence into a market-based village. Within the chosen analytical framework this change can be related to the change of type of fuel and changes in social practices within the economy. The Second Chapter presents an application of the Relational Analysis and MuSIASEM to the oil and gas sector of Mexico; the analysis is used to comment on the current Energy Reform in Mexico. This chapter brings a biophysical analysis of the oil & gas sector of Mexico. Looking at the current pattern of oil and gas production in Mexico it discusses whether Mexico should remain with the same pattern or change it. It also shows the importance of complementing the economic analysis with other types of analysis dealing with issues such as energy sovereignty, environmental impact and geographic location of economic activities. In short, it shows the importance of complementing reductionist analysis when planning. Third Chapter presents an application of the Relational Analysis and MuSIASEM to the electricity production in Mexico. The analysis of the relations between structural and functional elements allow studying the nexus between land, energy, and emissions. In particular, it elucidates the spatial constraints that can be associated with the expansion of alternative sources of electricity. In the past, we emancipated from the need of using a lot of land for energy purposes by using fossil fuels. But how strong is this emancipation when relying on intermittent electricity (wind and PV)? To answer this question, we have to address the increasing demand for importation of natural gas as a back-up of the intermittent sources of electricity, and the potential rebound effect of this solution, if the pattern of consumption remains the same. In the Fourth Chapter I demonstrate how the functional perspective can be used to introduce a novel approach to energy system analysis This application shows the weakness of assessments based on ratios (EROEI for example) if we want to address the complexity associated with sustainability. Radical simplifications of indicators of energy performance (simplistic definitions of energy) can be useful for those interested in “technofixes” but not for understanding the functioning of the system. For this reason, a systemic analysis of structural and functional relations should be incorporated in the energy analysis if we want to make it useful for the understanding of the interaction of socioecological systems.

The concept of exergy is defined and applied to district heating systems. The influence from different reference state conditions and system boundaries are explained in some detail. The aim is to show the simplicity and value of using the concept of exergy when analyzing district heating processes. The exergy factor is introduced and applied for a number of Swedish and Danish district heating systems. This varies from 14.2% to 22.5% for Swedish district heating systems. The higher the exergy factor, the more the exergy losses in the passive conversion towards space heating. Large losses revealed in an exergy treatment of a process should be seen as a challenge to achieve technical improvements of the system.

The objective of this thesis is to model and analyze the energy consumption in heterogeneous cellular systems and develop techniques to minimize it. First, the energy consumption is modeled and analyzed for multi-layered heterogeneous wireless systems. This work encompasses the characterization of all the energy consumed at the base stations. Then, a novel on-off and cell-association scheme is proposed to minimize the overall network energy consumption while satisfying the spatially- and temporally-varying traffic demands. Second, we exploit the use of multi-stream carrier aggregation not only to improve the energy efficiency, but also to balance it with the conflicting objective of capacity maximization. Third, we analyze the performance of discontinuous reception methods for energy savings within the user equipments. Then, for scenarios that support carrier aggregation, we develop a cross-carrier-aware technique that further enhances such savings with minimum impact on the packet delay. Fourth, the use of small cells as an energy-saving tool and its limitations are analyzed and modeled in OPNET, a high-fidelity simulation and development platform. To bypass such limitations, a novel small cell solution is proposed, modeled, and analyzed in OPNET and then compared against its existing alternative.

Attualmente è riscontrabile a livello globale un aumento del numero di giacimenti offshore contenenti un piccolo quantitativo di gas a bassa pressione e dunque destinati ad essere avviati alla procedura finale di chiusura. Per eliminare gli elevati costi di trasporto del gas e valorizzare il sito, nasce il concetto di Gas-to-Wire. Esso consiste nella produzione di elettricità attraverso la combustione del gas naturale in sito. Allo stesso tempo, la consapevolezza che le risorse oil & gas sono destinate ad estinguersi con gli anni ha spinto la comunità scientifica a concentrare l’attenzione su nuove forme di energia rinnovabile, come le onde marine. Nonostante ciò, vi sono ancora delle barriere da abbattere legate sia al prezzo di tali tecnologie che alla produzione di energia in modo discontinuo che rende problematica la loro integrazione nella rete elettrica. Al fine di superare tali problematiche, si è pensato di adottare un sistema ibrido di energia offshore costituito da convertitori di onda e microturbine a gas installate sulla piattaforma presente nel giacimento depleto. Esse forniscono potenza addizionale di bilanciamento sfruttando il concetto di Gas-to-Wire, consentendo una maggiore dispacciabilità dell’energia rinnovabile da onde. Lo scopo del presente lavoro è quello di analizzare le prestazioni energetiche, economiche e d’impatto ambientale del sistema ibrido di energia offshore. Due differenti siti, Mare del Nord e Mar Adriatico, sono stati presi in considerazione al fine di valutare l’influenza delle diverse condizioni meteo-marine, diversi mercati elettrici di dispacciamento e diversi incentivi fiscali per l’integrazione di energia rinnovabile sulle prestazioni del sistema ibrido di energia offshore. Attraverso l’approccio seguito per il dimensionamento e gestione dei due sistemi ibridi, è stato possibile calcolare gli indicatori tecnici, ambientali ed economici.

Thesis (S.M. in Technology and Policy)--Massachusetts Institute of Technology, Engineering Systems Division, Technology and Policy Program, 2012.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 151).
One of the key impediments to the development of enhanced geothermal systems is a deficiency in the tools available to project planners and developers. Weak tool sets make it difficult to accurately estimate the cost and schedule requirements of a proposed geothermal plant, and thus make it more difficult for those projects to survive an economic decision-making process. This project, part of a larger effort led by the Department of Energy, seeks to develop a suite of decision analysis tools capable of accurately gauging the economic costs and benefits of geothermal projects with uncertain outcomes. In particular. this project seeks to adapt a set of existing tools, the Decision Aids for Tunnelling, to the context of well-drilling, and make them suitable for use as a core software set around which additional software models can be added. We assess the usefulness of the Decision Aids for Tunnelling (DAT) by creating two realistic case studies to serve as proofs of concept. These case studies are then put through analyses designed to reflect project risks to which geothermal wells are vulnerable. We find that the DAT have sufficient flexibility to model geothermal projects accurately and provide cost and schedule distributions on potential outcomes of geothermal projects, and recommend methods of usage appropriate to well drilling scenarios.
by Keith A. Yost..
S.M.in Technology and Policy

In this thesis, several configurations of combined cycle cogeneration systems proposed by the author and an existing system, the Bilkent Combined Cycle Cogeneration Plant, are investigated by energy, exergy and thermoeconomic analyses. In each of these configurations, varying steam demand is considered rather than fixed steam demand. Basic thermodynamic properties of the systems are determined by energy analysis utilizing main operation conditions. Exergy destructions within the system and exergy losses to environment are investigated to determine thermodynamic inefficiencies in the system and to assist in guiding future improvements in the plant. Among the different approaches for thermoeconomic analysis in literature, SPECO method is applied. Since the systems have more than one product (process steam and electrical power), systems are divided into several subsystems and cost balances are applied together with the auxiliary equations. Hence, cost of each product is calculated. Comparison of the configurations in terms of performance assessment parameters and costs per unit of exergy are also given in this thesis.

Water and wastewater treatment is a critical service provided for protecting human health and the environment. Over the past decade, increasing attention has been placed on energy consumption in water and wastewater systems for the following reasons: (1) Water and energy are two interrelated resources. The nexus between water and energy can intensify the crises of fresh water and fossil fuel shortages; (2) The demand of water/wastewater treatment services is expected to continue to increase with increasing population, economic development and land use change in the foreseeable future; and (3) There is a great potential to mitigate energy use in water and wastewater systems by recovering resources in wastewater treatment systems. As a result, the goal of this dissertation study is to assess the life cycle energy use of both water supply systems and wastewater treatment systems, explore the potential of integrated resource recovery to reduce energy consumption in wastewater systems, and understand the major factors impacting the life cycle energy use of water systems. To achieve the goal, an input-output-based hybrid embodied energy model was developed for calculating life cycle energy in water and wastewater systems in the US. This approach is more comprehensive and less labor intensive than the traditional life cycle assessment. Additionally, this model is flexible in terms of data availability. It can give a rough estimation of embodied energy in water systems with limited data input. Given more site specific data, the model can modify the embodied energy of different energy paths involved in water related sectors. Using the input-output-based hybrid embodied energy model, the life cycle energy of a groundwater supply system (Kalamazoo, Michigan) and a surface water supply system (Tampa, Florida) was compared. The two systems evaluated have comparable total energy embodiments based on unit water production. However, the onsite energy use of the groundwater supply system is approximately 27% greater than the surface water supply system. This was primarily due to more extensive pumping requirements. On the other hand, the groundwater system uses approximately 31% less indirect energy than the surface water system, mainly because of fewer chemicals used for treatment. The results from this and other studies were also compiled to provide a relative comparison of embodied energy for major water supply options. The comparison shows that desalination is the most energy intensive option among all the water sources. The embodied energy and benefits of reclaimed water depend on local situations and additional treatment needed to ensure treated wastewater suitable for the desired application. A review was conducted on the current resource recovery technologies in wastewater treatment systems. It reveals that there are very limited life cycle studies on the resource recovery technologies applied in the municipal wastewater treatment systems and their integrations. Hence, a life cycle study was carried out to investigate the carbon neutrality in a state-of-art wastewater treatment plant in Tampa, FL. Three resource recovery methods were specifically investigated: onsite energy generation through combined heat and power systems, nutrient recycling through biosolids land application, and water reuse for residential irrigation. The embodied energy and the associated carbon footprint were estimated using the input-output-based hybrid embodied energy model and carbon emission factors. It was shown that the integrated resource (energy, nutrient and water) recovery has the potential to offset all the direct operational energy; however, it is not able to offset the total embodied energy of the treatment plant to achieve carbon neutrality. Among the three resource recovery methods, water reuse has the highest potential of offsetting carbon footprint, while nutrient recycling has the lowest. A final application of the model was to study on the correlation between embodied energy in regional water supply systems and demographic and environmental characteristics. It shows that energy embodied in water supply systems in a region is related to and can be estimated by population, land use patterns, especially percentage of urban land and water source, and water sources. This model provides an alternative way to quickly estimate embodied energy of water supply in a region. The estimated embodied energy of water supply can further be used as a supporting tool for decision making and planning.

The aim of this thesis is to take a broad conceptual overview of the global energy system and investigate what the aims of sustainability might entail for such a system. The work presented uses a biophysical economic approach in that the dynamics of the global economy are investigated using the tool box of the physical sciences, including the laws of thermodynamics and the methods of energy analysis. Modern society currently uses approximately 500 exajoules (EJ = 10^18 J) of total primary energy supply (TPES) each year. This energy consumption has been increasing at roughly 2% per year for the past two hundred years. TPES is currently dominated by three non-renewable energy sources: coal, oil and gas which, together with energy from nuclear fission of uranium, make up around 85% of the energy market. Consumption of finite resources at a continuously growing rate is not sustainable in the long-term. A trend in policy direction is to seek a transition to renewable sources of energy. This thesis seeks to explore two questions: are the technical potentials of renewable energy sources enough to supply the current and/or projected demand for energy and what would be the effect on the physical resource economy of a transition to an energy supply system run entirely on renewable energy sources? The Global Energy Model using a Biophysical Approach (GEMBA) methodology developed here is compared and contrasted with other approaches that are used to study the global energy-economy system, including the standard neoclassical economic approach used in such models as MESSAGE and MARKAL. A number of meta-analyses have been conducted in support of the GEMBA model. These include: meta-analysis of historic energy production from all energy sources; meta-analysis of global energy resources for all energy sources; meta-analysis of energy-return-on-investment (EROI) for all energy sources. The GEMBA methodology uses a systems dynamic modelling approach utilising stocks and flows, feedback loops and time delays to capture the behaviour of the global energy-economy system. The system is decomposed into elements with simple behaviour that is known through energy analysis. The interaction of these elements is captured mathematically and run numerically via the systems dynamics software package, VenSim. Calibration of the model has been achieved using historic energy production data from 1800 to 2005. The core of the GEMBA methodology constitutes the description of a dynamic EROI function over the whole production cycle of an energy resource from initial development, through maturation to decline in production, in the case of non-renewable resources, or to the technical potential in the case of renewable resources. Using the GEMBA methodology, the global energy-economy system is identified as a self-regulating system. The self-regulating behaviour acts to constrain the amount of total primary energy supply that the system can produce under a renewable-only regime. A number of analyses are conducted to test the sensitivity of the system to such changes as: an increase of the technical potential of renewable resources; technological breakthroughs which would significantly increase the EROI of renewable resources; a decrease in the capital intensity of renewable resources and; an increase in the energy intensity of the economy, A statistical analysis reflecting the wide range of values of both the estimates of EROI and technical potentials of renewable energy sources has also been undertaken using a Monte Carlo approach. The results from the modelling suggest that not all levels of energy demand projected by the WEA can be supplied by an energy system running solely on renewable energy. The Monte Carlo analyses suggest that reduction in total energy yield over current (2010) levels might occur with a 20-30% possibility. The middle and high growth scenarios from the WEA are greater than 95% of all scenarios modelled, hence seem unlikely to be sustained by an energy system running solely on renewable energy. This finding has implications for the future direction of both engineering and technology research as well as for energy policy. These implications are discussed.

Background and Motivation

Unlike what is common in Europe and the rest of the world, Norway has traditionally met most of its stationary energy demand (including heating) with electricity, because of abundant access to hydropower. However, after the deregulation of the Norwegian electricity market in the 1990s, the increase in the electricity generation capacity has been less than the load demand increase. This is due to the relatively low electricity prices during the period, together with the fact that Norway’s energy companies no longer have any obligations to meet the load growth. The country’s generation capacity is currently not sufficient to meet demand, and accordingly, Norway is now a net importer of electricity, even in normal hydrological years. The situation has led to an increased focus on alternative energy solutions.

It has been common that different energy infrastructures – such as electricity, district heating and natural gas networks – have been planned and commissioned by independent companies. However, such an organization of the planning means that synergistic effects of a combined energy system to a large extent are neglected. During the last decades, several traditional electricity companies have started to offer alternative energy carriers to their customers. This has led to a need for a more comprehensive and sophisticated energy-planning process, where the various energy infrastructures are planned in a coordinated way. The use of multi-criteria decision analysis (MCDA) appears to be suited for coordinated planning of energy systems with multiple energy carriers. MCDA is a generic term for different methods that help people make decisions according to their preferences in situations characterized by multiple conflicting criteria.

The thesis focuses on two important stages of a multi-criteria planning task:

- The initial structuring and modelling phase

- The decision-making phase

The Initial Structuring and Modelling Phase

It is important to spend sufficient time and resources on the problem definition and structuring, so that all disagreements among the decision-maker(s) (DM(s)) and the analyst regarding the nature of the problem and the desired goals are eliminated. After the problem has been properly identified, the next step of a multi-criteria energy-planning process is the building of an energy system model (impact model). The model is used to calculate the operational attributes necessary for the multi-criteria analysis; in other words, to determine the various alternatives’ performance values for some or all of the criteria being considered. It is important that the model accounts for both the physical characteristics of the energy system components and the complex relationships between the system parameters. However, it is not propitious to choose/build an energy system model with a greater level of detail than needed to achieve the aims of the planning project.

In my PhD research, I have chosen to use the eTransport model as the energy system model. This model is especially designed for planning of local and regional energy systems, where different energy carriers and technologies are considered simultaneously. However, eTransport can currently provide information only about costs and emissions directly connected to the energy system’s operation. Details about the investment plans’ performance on the remaining criteria must be found from other information sources. Guidelines should be identified regarding the extent to which different aspects should be accounted for, and on the ways these impacts can be assessed for each investment plan under consideration. However, it is important to realize that there is not one solution for how to do this that is valid for all kind of local energy-planning problems. It is therefore necessary for the DM(s) and the analyst to discuss these issues before entering the decision-making phase.

The Decision-Making Phase

Two case studies have been undertaken to examine to what extent the use of MCDA is suitable for local energy-planning purposes. In the two case studies, two of the most well-known MCDA methods, the Multi-Attribute Utility Theory (MAUT) and the Analytical Hierarchy Process (AHP), have been tested. Other MCDA methods, such as GP or the outranking methods, could also have been applied. However, I chose to focus on value measurement methods as AHP and MAUT, and have not tested other methods. Accordingly, my research cannot determine if value measurement methods are better suited for energy-planning purposes than GP or outranking methods are.

Although all MCDA methods are constructed to help DMs explore their ‘true values’ – which theoretically should be the same regardless of the method used to elicit them – our experiments showed that different MCDA methods do not necessarily provide the same results. Some of the differences are caused by the two methods’ different ways of asking questions, as well as the DMs’ inability to express clearly their value judgements by using one or both the methods. In particular, the MAUT preference-elicitation procedure was difficult to understand and accept for DMs without previous experience with the utility concept. An additional explanation of the differences is that the external uncertainties included in the problem formulation are better accounted for in MAUT than in AHP. There are also a number of essential weaknesses in the theoretical foundation of the AHP method that may have influenced the results using that method. However, the AHP method seems to be preferred by DMs, because the method is straightforward and easier to use and understand than the relatively complex MAUT method.

It was found that the post-interview process is essential for a good decision outcome. For example, the results from the preference aggregation may indicate that according to the DM’s preferences, a modification of one of the alternatives might be propitious. In such cases, it is important to realize that MCDA is an iterative process. The post-interview process also includes presentation and discussion of results with the DMs. Our experiments showed that the DMs might discover inconsistencies in the results; that the results do not reflect the DM’s actual preferences for some reason; or that the results simply do not feel right. In these cases, it is again essential to return to an earlier phase of the MCDA process and conduct a new analysis where these problems or discrepancies are taken into account.

The results from an MAUT analysis are usually presented to the DMs in the form of expected total utilities given on a scale from zero to one. Expected utilities are convenient for ranking and evaluation of alternatives. However, they do not have any direct physical meaning, which quite obviously is a disadvantage from an application point of view. In order to improve the understanding of the differences between the alternatives, the Equivalent Attribute Technique (EAT) can be applied. EAT was tested in the first of the two case studies. In this case study, the cost criterion was considered important by the DMs, and the utility differences were therefore converted to equivalent cost differences. In the second case study, the preference elicitation interviews showed, quite surprisingly, that cost was not considered among the most important criteria by the DMs, and none of the other attributes were suitable to be used as the equivalent attribute. Therefore, in this case study, the use of EAT could not help the DMs interpreting the differences between the alternatives.

Summarizing

For MCDA to be really useful for actual local energy planning, it is necessary to find/design an MCDA method which: (1) is easy to use and has a transparent logic; (2) presents results in a way easily understandable for the DM; (3) is able to elicit and aggregate the DMs' real preferences; and (4) can handle external uncertainties in a consistent way.

Increased energy demands and fear of global warming due tothe emission of greenhouse gases call for development of newefficient power generation systems with low or no carbondioxide(CO₂) emissions. In this thesis, two different gasturbine power generation systems, which are designed with theseissues in mind, are theoretically investigated and analyzed.Inthe first gas turbine system, the fuel is combusted using ametal oxide as an oxidant instead of oxygen in the air. Thisprocess is known as Chemical Looping Combustion (CLC). CLC isclaimed to decrease combustion exergy destruction and increasethe power generation efficiency. Another advantage is thepossibility to separate CO₂without a costly and energy demanding gasseparation process. The system analysis presented includescomputer-based simulations of CLC gas turbine systems withdifferent metal oxides as oxygen carriers and different fuels.An exergy analysis comparing the exergy destruction of the gasturbine system with CLC and conventional combustion is alsopresented. The results show that it is theoretically possibleto increase the power generation efficiency of a simple gasturbine system by introducing CLC. A combined gas/steam turbinecycle system with CLC is, however, estimated to reach a similarefficiency as the conventional combined cycle system. If thebenefit of easy and energy-efficient CO₂separation is accounted for, a CLC combined cyclesystem has a potential to be favorable compared to a combinedcycle system with CO₂separation.

In the second investigation, a solid, CO₂-neutral biomass fuel is used in a small-scaleexternally fired gas turbine system for cogeneration of powerand district heating. Both open and closed gas turbines withdifferent working fluids are simulated and analyzed regardingthermodynamic performance, equipment size, and economics. Theresults show that it is possible to reach high power generationefficiency and total (power-and-heat) efficiency with thesuggested system. The economic analysis reveals that the costof electricity from theEFGT plant is competitive with the moreconventional alternatives for biomass based cogeneration in thesame size range (<10 MW_e).

Keywords:power generation, Chemical Looping Combustion,CO₂separation, oxygen carrier, biomass fuel, closedcycle gas turbine, externally fired gas turbine

This thesis investigates electro-mechanical generator systems which harvest energy from their environment. Such systems are needed to create maintenance-free sensor nodes for use in autonomous wireless sensor networks which have applications in health monitoring. Inertial microgenerators are investigated in detail. Inertial micro-generators produce electrical energy when subjected to acceleration. Three architectures of inertial micro-generator were identi ed as suitable for implementation using MEMS technology. Two of these architectures, both resonant in nature, have been reported in the existing literature. The third, a non-resonant type, is new. The architectures have been analysed and compared within a common framework, based on sinusoidal driving signals and a common set of normalisation factors. A simple procedure for the design process of micro-generators was established. Within the analytical framework, the non-resonant generator achieved the highest power density of the three architectures when powered from large amplitude motion, making it the most suitable for powering implanted medical devices. Comparing the performance of the three architectures on measured acceleration data from human subjects showed that this result is more widely applicable than for simple sinusoidal driving motions. Bio-compatibility of microgenerator systems has not been addressed in this work. The non-resonant architecture was investigated in more detail. To maximise nal energy yield taking into account interactions between various generator sub-systems, a uni ed simulation of a power supply system built around the non-resonant generator was developed and includes detailed models of the required semiconductor devices. A prototype generator was used to verify the behaviour of the model. The concept of system effectiveness was introduced which accounts for both the ef ciency of the energy conversion stages and the success in coupling energy from what is assumed to be a large and free original source.

Recent advancement in wireless communication networks expect exponential growth of smart phones, diverse wireless services and Internet of Things (IoT) applications. The extensive growth of wireless devices can significantly increase energy consumption, and therefore, creates environmental pollution. An urge for green communication is building up day by day. As a matter of fact, there is a need to design environment friendly wireless communication technologies and energy efficient resource allocation solutions, which will potentially drive the next generation of wireless communication. In this thesis, we design and analyse energy harvesting wireless communication system by considering both renewable energy and RF energy sources. For a relayed communication system, we develop joint optimal power and power-splitting ratio allocation scheme where relay does not have its own energy supply. The relay harvests energy from interference and the signal received from the source. We consider both half-duplex and full-duplex relaying. For half-duplex relaying, we analyse the amount of harvested energy by controlling the amount of incoming interference using power splitting ratio. In addition, we show the impact of self-interference for full-duplex relay and compare the results with half-duplex cooperative energy harvesting wireless networks. Next, we consider multi-relay network, where relays harvest renewable energies from the surrounding environment. For this setup, we propose the optimal policy for relay selection and power allocation under unknown statistics of the channel fading and energy arrival processes. In particular, we develop an efficient low-complexity learning algorithm that does not require the statistics of the channel fading and energy harvesting processes to be known.
Applied Science, Faculty of
Engineering, School of (Okanagan)
Graduate

Embodied energy is the energy consumed in all activities necessary to support a process in its entire lifecycle. For power generation systems, this includes the energy cost of raw material extraction and transportation, plant construction, energy generation and the recycling and disposal stages following actual use. Embodied energy analysis is a crude method of estimating the environmental impacts and depletion of natural resources consequent to a certain process. In effect, the higher the embodied energy of a process, the greater the green house gas emissions and the depletion of the natural resources. This thesis presents the embodied energy analysis carried out on some New Zealand power plants belonging to various methods of generation, namely, natural gas combined cycle (NGCC), natural gas open cycle (NGOC), wind, reservoir hydro and run of river hydro power plants. The analysis was carried out using a combination of process chain analysis and input output analysis, which are the two fundamental methodologies for embodied energy analysis. It follows the standards set out by the International Organisation for Standardisation 14040 series, and uses some guidelines given in the International Federation of Institutes for Advanced Study workshop on energy analysis methodology and conventions. From the analysis, it was found that for renewable generation power plants, the exploration and plant construction phase of the lifecycle contributes the largest amount of embodied energy, while for the non renewable power plants, the largest amount of embodied energy is contributed by the plant operation and maintenance phase of the lifecycle. The lifecycle energy payback ratio, which corresponds to the ratio of electrical energy output over the total lifecycle energy input, of the power plants are 96.9, 62.8, 7.96, 0.487 and 0.354 for run of river hydro, reservoir hydro, wind, NGCC and NGOC, respectively. Therefore, the lifecycle performance of renewable electricity generation is superior to non renewable electricity generation. Hence, the environmental impacts and depletion of natural resources from non renewable electricity generation is higher than renewable electricity generation. From the generation methodologies, hydro power plants have exceptional performance characteristics.

In the framework of the micro-CHP (Combined Heat and Power) energy systems and the Distributed Generation (GD) concept, an Integrated Energy System (IES) able to meet the energy and thermal requirements of specific users, using different types of fuel to feed several micro-CHP energy sources, with the integration of electric generators of renewable energy sources (RES), electrical and thermal storage systems and the control system was conceived and built. A 5 kWel Polymer Electrolyte Membrane Fuel Cell (PEMFC) has been studied. Using experimental data obtained from various measurement campaign, the electrical and CHP PEMFC system performance have been determinate. The analysis of the effect of the water management of the anodic exhaust at variable FC loads has been carried out, and the purge process programming logic was optimized, leading also to the determination of the optimal flooding times by varying the AC FC power delivered by the cell. Furthermore, the degradation mechanisms of the PEMFC system, in particular due to the flooding of the anodic side, have been assessed using an algorithm that considers the FC like a black box, and it is able to determine the amount of not-reacted H2 and, therefore, the causes which produce that. Using experimental data that cover a two-year time span, the ageing suffered by the FC system has been tested and analyzed.

The continuous growth of high data rates with huge increase in the number of mobile devices and communication infrastructure have led to greenhouse gas emission, higher pollution and higher energy costs. After the deployment of 4G and immense data rate and QoS requirements for 5G, there is an urgent need to design future wireless systems that aim to improve energy efficiency (EE) and spectral efficiency (SE). One of the possible solutions is to use energy harvesting (EH), which promises to reduce energy consumption issues in information and communication technology sector. In order to tackle these challenges, this thesis is focused on the design and performance analysis of EH systems. EH has emerged as a potential candidate for green wireless communication which not only provides solution to the energy limitation problem but also prolongs the lifetime of batteries. First, the performance evaluation of an EH-equipped dual-hop relaying system is proposed to improve the system throughput and the end-to-end signal-to-noise ratio (SNR). We derive novel closed-form expressions for cumulative distribution function of individual link's SNR and of the end-to-end SNR. In addition, the proposed model analyses the ergodic capacity which is an important performance metric for delay-sensitive services. Further, these closed-form expressions reduce the computational complexity of the receiver architecture for practical systems. An insight through system parameters provide significant improvement in end-to-end SNR especially when both transmitter and relay nodes are equipped with harvesting sources. Second, performance analysis and optimal transmission power allocation techniques for EH-equipped system are studied. Our proposed model investigates and provides the conditions under which the harvesting can improve the system performance. In this work, novel closed-form expressions are calculated for the maximum achievable EE, SE and EH beneficialness condition. We studied two cases such as power is adapted to variations in the channel and when transmit power is fixed. We proved that EE-optimum input power decreases with EH power level. Also, system parameters demonstrate the conditions under which EH improves overall system performance. Finally, a multi-objective optimization problem is formulated that jointly maximizes EE and SE for point-to-point EH-equipped system. We introduce new importance weight which set the priority levels of EE versus SE of the system. The formulated problem is solved by using convex optimization method to achieve optimal solution. The proposed system model provides freedom to choose any value for importance weight to satisfy quality of service (QoS) requirements and the flexibility of balancing between EE and SE performance metrics.

At present, the battery is employed as a power source for wide varieties of microelectronic systems ranging from biomedical implants and sensor net-works to portable devices. However, the battery has several limitations and incurs many challenges for the majority of these systems. For instance, the design considerations of implantable devices concern about the battery from two aspects, the toxic materials it contains and its lifetime since replacing the battery means a surgical operation. Another challenge appears in wire-less sensor networks, where hundreds or thousands of nodes are scattered around the monitored environment and the battery of each node should be maintained and replaced regularly, nonetheless, the batteries in these nodes do not all run out at the same time. Since the introduction of portable systems, the area of low power designs has witnessed extensive research, driven by the industrial needs, towards the aim of extending the lives of batteries. Coincidentally, the continuing innovations in the field of micro-generators made their outputs in the same range of several portable applications. This overlap creates a clear oppor-tunity to develop new generations of electronic systems that can be powered, or at least augmented, by energy harvesters. Such self-powered systems benefit applications where maintaining and replacing batteries are impossi-ble, inconvenient, costly, or hazardous, in addition to decreasing the adverse effects the battery has on the environment. The main goal of this research study is to investigate energy harvesting aware design techniques for computational logic in order to enable the capa- II bility of working under non-deterministic energy sources. As a case study, the research concentrates on a vital part of all computational loads, SRAM, which occupies more than 90% of the chip area according to the ITRS re-ports. Essentially, this research conducted experiments to find out the design met-ric of an SRAM that is the most vulnerable to unpredictable energy sources, which has been confirmed to be the timing. Accordingly, the study proposed a truly self-timed SRAM that is realized based on complete handshaking protocols in the 6T bit-cell regulated by a fully Speed Independent (SI) tim-ing circuitry. The study proved the functionality of the proposed design in real silicon. Finally, the project enhanced other performance metrics of the self-timed SRAM concentrating on the bit-line length and the minimum operational voltage by employing several additional design techniques.

The thesis addresses electronic power distribution systems for the residential applications. Presented are both, renewable energy ac-nanogrid system along with the vehicle-to-grid technology implementation, and envisioned structure and operation of dc-nanogrid addressing all system components chosen as an inherent part of the future electrical architecture. The large-scale model is built and tested in the laboratory environment covering a few operational modes of the ac-nanogrid, while later in the thesis is shown how dc bus signaling technique could be contemplated for the energy management of the renewable energy sources and their maximal utilization. Thesis however puts more focus on the dc-nanogrid system to explore its benefits and advantages for the electrical systems of the future homes that can easily impact not only residential, but also microgrid, grid and intergrid levels. Thus, presented is low frequency terminal behavioral modeling of the system components in dc-nanogrid motivated by the fact that system engineers working on the system-level design rarely have access to all the information required to model converters and system components, other than specification and data given in the datasheets. Using terminal behavioral modeling, converters are measured on-line and their low frequency dynamics is identified by the means of the four transfer functions characteristically used in two port network models. This approach could significantly improve system-level design and simulations. In addition to previously mentioned, thesis addresses terminal behavioral modeling of dc-dc converters with non-linear static behavior showing hybrid behavioral models based on the Hammerstein approach.
Master of Science

We present an extension of the popular probabilistic model checker PRISM with multi-actions that enables the modeling of complex coordination between stochastic components in an exogenous manner. This is supported by tooling that allows the use of the exogenous coordination language Reo for specifying the coordination glue code. The tool provides an automatic compilation feature for translating a Reo network of channels into PRISM's guarded command language. Additionally, the tool supports the translation of reward monitoring components that can be attached to the Reo network to assign rewards or cost to activity within the coordination network. The semantics of the translated model is then based on weighted Markov decision processes that yield the basis, e.g., for a quantitative analysis using PRISM. Feasibility of the approach is shown by a quantitative analysis of an energy-aware network system example modeled with a role-based modeling approach in Reo.

The continuous escalation of intermittent energy added to the grid and forecasts of peaking power demand increments are rising the effort spent for evaluating the economic feasibility of energy storages. The aim of this research is the techno-economic analysis of Compressed Air Energy Storage (CAES) systems, capable of storing large quantities of off-peak electric energy in the form of high-pressure air, as an ―energy stock‖ which allows the production of high-profit on-peak electricity when required by the grid. Several studies of both conventional and innovative adiabatic concepts are carried out in order to identify and improve the parameters that mostly affect the plant performances. Technical models, that consider the effect of time, are developed to evaluate the parameters that reduce the electric energy spent for compressing the air and that maximize the electric energy produced. In the conventional plant, particular attention is put on the understanding of the effects of air storage pressure range, recuperator, reheating and Turbine Inlet Temperature. For the adiabatic instead, a thorough analysis of the challenging Thermal Energy Storage (TES) is performed for understanding the advantages and drawbacks of this novel efficient concept of CAES. In a further step the economic analyses are aimed at evaluating the different configurations proposed in the technical investigation and the effects that variations of generation train and storage characteristics have on the profitability. After an analysis of the TES impact on the profits, a final comparison is carried out against two existing technologies: Pumped Hydro Energy Storage and gas turbine. The results of these studies confirm, from a technical and economic point of view, the reasons of the growing interest toward CAES as a feasible solution to manage the intermittent energy production. In particular they underline the conventional CAES as promising technology to undertake.

Thesis (S.M. in Technology and Policy)--Massachusetts Institute of Technology, Engineering Systems Division, Technology and Policy Program, 2010.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 85-87).
Public and private organizations try to forecast the future of technological developments and allocate funds accordingly. Based on our interviews with experts from MIT's Entrepreneurship Center, Sloan School of Management, and IBM, and review of literature, we found out that this important fund allocation process is dominated by reliance on expert opinions, which has important drawbacks alongside its advantages. In this Thesis, we introduce a data-driven approach, called early growth technology analysis, to technology forecasting that utilizes diverse information sources to analyze the evolution of promising new technologies. Our approach is based on bibliometric analysis, consisting of three key steps: extraction of related keywords from online publication databases, determining the occurrence frequencies of these keywords, and identifying those exhibiting rapid growth. Our proposal goes beyond the theoretical level, and is embodied in software that collects the required inputs from the user through a visual interface, extracts data from web sites on the fly, performs an analysis on the collected data, and displays the results. Compared to earlier software within our group, the new interface offers a much improved user experience in performing the analysis. Although these methods are applicable to any domain of study, this Thesis presents results from case studies on the fields of solar and geothermal energy. We identified emerging technologies in these specific fields to test the viability of our results. We believe that data-driven approaches, such as the one proposed in this Thesis, will increasingly be used by policy makers to complement, verify, and validate expert opinions in mapping practical goals into basic/applied research areas and coming up with technology investment decisions.
by Ayse Kaya Firat.
S.M.in Technology and Policy

This study explored energy solutions for Ghana by analysing alternative pathways from 2010 to 2040. The Long-range Energy Alternating Pathways (LEAP) tool was used the scenarios analysis. Four scenarios were developed based on key influencing factors identified in the literature. These are Base case, Coal, Modest Renewable Energy Technology (RET), and High RET scenarios. The Base case scenario was based on government-planned expansion and assumed no shift in policy. The Coal scenario assumed the same expansion trend as Base case with introduction of coal plants replacing a percentage of natural gas generation. Modest and High RET scenarios examined the development of the system with increased renewable energy integration. The results revealed that overall benefits are achieved with higher integration of renewable energy technologies. Economic benefits of 0.5 –13.23% is achieved in the RET scenarios depending on the cost development over the 30 year study period. The high RET offers the highest economic and environmental benefits. Subsequently, the optimal development of the system was examined using the LEAP/OSeMOSYS (Open Source Energy Modelling System) optimisation methodology. The least cost system developed by LEAP (Optimum scenario), was used as a reference to examine future possible energy policy direction in Ghana. The policy constraints analysed included emission targets, carbon taxes and transmission, distribution losses improvements and demand side efficiency. The results show that: suitable policies for clean power generation have an important role in CO2 mitigation in Ghana. The introduction of carbon minimisation policies will also promote diversification of the generation mix with higher penetration of renewable energy technologies. The study proposes promoting energy efficiency and improvement in transmission and distribution losses and utilisation of renewable energy as the best energy strategy for Ghana. Ghana needs ambitious targets, policies and implementation strategies to enhance energy efficiency, and decrease demand in the long term. Stable funding and promotion of transparent policies are required to promote high development of renewable energy technologies.

Snow-free surfaces is needed for parking place, platform, and playground and even in city center square. With energy prices rising, energy saving is becoming a hot topic. Meanwhile environmental problems are becoming more and more serious, thus, the ways to saving energy is becoming an eye-catcher. So burring heating pipes underground has been a popular way to get ice-free surfaces. Using heating pipes for melting snow is much more efficient and more benefit for the environment comparing with using other methods.   In this project, an energy analysis of a football pitch with an area of 5000 m2 is carried out under a series of conditions between insulated and uninsulated construction. All calculations are done with the so-called finite element method (FEM), in the COMSOL. COMSOL is used for simulating and calculating the energy use with outdoor temperatures of -5 ºC and -10 ºC. Top layer materials concrete, grass and stone are also discussed. The ability of XPS and EPS insulation material is compared and noted. The models are divided into two parts, one is with snowfall and the other is without snowfall.   The results in the report shows that adding insulation under the heating pipe has significant energy saving potential. The surface with concrete layer has the best insulated ability, which can prevent more heat losses. The EPS insulated construction has a better performance in keeping more heat in the soil.

Thesis (M.S.)--West Virginia University, 2003.
Title from document title page. Document formatted into pages; contains vi, 97 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 97).

Though mandatory to be pursued, improved energy efficiency is not the only target to reach. The quality of energy has to be assessed as well. Most of the overall energy use in residential building is for low temperature heat, i.e. temperatures relatively close to the outdoor conditions. From a thermodynamic point of view, this is a degraded form of energy with low potential to be converted into work. On the other hand energy demand is mostly met with high quality energy, such as electricity and natural gas. There is a mismatch between supply and demand, which is not clearly shown by the sole energy analysis. Target of this thesis is to analyze the energy use in buildings from the point of view of its quality, to provide effective theoretical and calculation tools to investigate this mismatch, to assess its magnitudo and to propose improvements aiming at a more rational use of the energy. The idea behind the quality is clarified with the concept of exergy.

The potential for improvement in space heating is shown. In no heating system the overall exergy efficiency is above 20%, with fossil fuels. Using direct electricity heating results in exergy efficiency below 7%. Most of the household appliances processes have low-exergy factors but still are supplied with electricity. This results in poor exergy efficiencies and large exergy losses.

Systems are poorly performing because little consideration is explicitly given to energy quality. Policies to lower the energy demand, though vital as first step towards an improved use of energy, should not neglect the exergy content.

The problem is then shifted to find suitable supplies. Electricity can be exploited with low exergy losses with high-COP heat pumps. Use of fossil fuels for heating purposes should be avoided. District heating from cogeneration and geothermal proves to be a suitable solution at the building level. The issues connected to its exploitation forces to shift the boundary layers of the analysis from the building level to the community level. A rational use of energy should address the community level. The system boundaries have to be enlarged to a dimension where both the energy conversion and use take place with reduced energy transportation losses. This is a cost-effective way to avoid the waste of the exergy potential of the sources with exergy cascade and to make it possible the integration of with renewable sources. Exergy efficiency of the buildings is a prerequisite for a better of energy in this field.

IEA ECBCS Annex 49: Low Exergy Systems for High Performance Buildings and Communities
ESF Cost C24: Analysis and Design of Innovative Systems for Low-EXergy in the Built Environment: COSTeXergy

Solar energy is an abundant renewable source, which is expected to play an increasing role in the grid's future infrastructure for distributed generation. The research described in the thesis focuses on the analysis of integrating multi-megawatt photovoltaics (PV) systems with battery energy storage into the existing grid and on the theory supporting the electrical operation of components and systems. The PV system is divided into several sections, each having its own DC-DC converter for maximum power point tracking and a two-level grid connected inverter with different control strategies. The functions of the battery are explored by connecting it to the system in order to prevent possible voltage fluctuations and as a buffer storage in order to eliminate the power mismatch between PV array generation and load demand. Computer models of the system are developed and implemented using the PSCADTM/EMTDCTM software.

Thesis (M.S.)--West Virginia University, 2006.
Title from document title page. Document formatted into pages; contains vii, 83 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 80-82).

"Large amounts of renewable energy generation are being introduced into modern power systems to decrease the environmental impact of power generation. Despite benefits, increased renewable energy penetration will likely create additional system instability and unpredictability. Increasing line capacity via redundancy of transmission networks and utilizing energy storage are two methods that can be used to increase transmission power system stability. This thesis investigates the economic effects of energy storage and line capacity in isolated test systems. Utilizing Powerworld Simulator, test systems based off two common industry test bed standards (WECC 9-bis, IEEE 14-bus) were built using scaled real-world generation and load data. Multiple Optimal Power Flow studies performed on the test systems with and without the addition of energy storage model revealed the incremental change in overall system cost of adding energy storage and highlighted the impact energy storage has on isolated systems with renewable energy."

A range of different scenarios have been predicted for future UK energy supply. While there is significant uncertainty, all expect an increase in small-scale distributed generation integrated in constrained or independent networks and with predominantly domestic consumers. This reduction in system scale has not, however, driven a significant change in design practices, with deterministic models and rules-of-thumb prevalent. Little consideration has been given to how the specific household characteristics and the size of system impact on demand level and timing, the degree of uncertainty in anydemand prediction, and how design practices should change to reflect this. The main contribution of the presented work has been to address this. To allow the variation and uncertainty to be quantified; a highly differentiated, probabilistic, bottom-up demand model has been developed for electrical and hot water use. The 1-minute resolution model incorporates an enhanced Markov chain occupancy model and is based on a newly developed discrete-event approach for occupant-initiated demands. Utilising realistic factoring for appliance ownership, income, occupancy, and random energy-use behaviours, the model has been shown to capture the range of potential household demands. Assessment that the developed model, and any existing model calibrated using group data, tended to rapidly converge to the group average basis, prompted further method development to improve the model's performance in capturing individual household demand behaviours. Analysis of both existing data and the demand model output has shown that energy system demand can vary significantly based on socio-economic characteristics and the types of households supplied. It also highlights that demand uncertainty for individual households can exceed an order of magnitude, even if household characteristics are known. As the system scale is increased, the level of overall demand uncertainty remains significant to at least 200 household systems. A method has therefore been developed that allows multiple runs of the probabilistic model to be reduced to a representative subset, which can be used to analyse potential energy system performance scenarios probabilistically using existing optimisation tools.

Presently, wireless sensor nodes are widely used and the lifetime of the system is becoming the biggest problem with using this technology. As more and more low power products have been used in WSN, energy harvesting technologies, based on their own characteristics, attract more and more attention in this area. But in order to design high energy efficiency, low cost and nearly perpetual lifetime micro energy harvesting system is still challenging. This thesis proposes a new way, by applying three factors of the system, which are the energy generation, the energy consumption and the power management strategy, into a theoretical model, to optimally design a highly efficient micro energy harvesting system in a real environment. In order to achieve this goal, three aspects of contributions, which are theoretically analysis an energy harvesting system, practically enhancing the system efficiency, and real system implementation, have been made. For the theoretically analysis, the generic architecture and the system design procedure have been proposed to guide system design. Based on the proposed system architecture, the theoretical analytical models of solar and thermal energy harvesting systems have been developed to evaluate the performance of the system before it being designed and implemented. Based on the model's findings, two approaches (MPPT based power conversion circuit and the power management subsystem) have been considered to practically increase the system efficiency. As this research has been funded by the two public projects, two energy harvesting systems (solar and thermal) powered wireless sensor nodes have been developed and implemented in the real environments based on the proposed work, although other energy sources are given passing treatment. The experimental results show that the two systems have been efficiently designed with the optimization of the system parameters by using the simulation model. The further experimental results, tested in the real environments, show that both systems can have nearly perpetual lifetime with high energy efficiency.

The wind energy industry has undergone a dramatic transformation during the last decade. The total operating wind power capacity in the world has increased greatly. As more and more attention is paid to the increase in both the size and number of wind farms, a number of problems should be investigated in more detail. The voltage stability problem primarily focuses on the reactive power management that affects voltage stability and transmission losses. Wind power farm installations that have the potential to displace a large percentage of fossil-fuel generation must be designed to avoid unacceptable frequency and voltage disturbances due to fluctuations in the wind power farm output.
The focus of this research is on the modeling of wind farms and the issues related to the interconnection of wind farms with the utility grid. Voltage stability problems are investigated for both strong and weak interconnections. Furthermore, the model and control of the Superconducting Magnetic Energy Storage (SMES) system is introduced into the wind farms to improve the power quality of wind farms. The study is conducted firstly, on a single wind energy conversion system, followed by addition of the issues of voltage stability and VAr compensation, and finally the investigation of the impact of wind farms on power quality are discussed in detail.

To this day, most of the communication networks are characterized by a "monolithic" operating approach. Network elements are configured and operate without any reconfiguration for long time periods. Softwarization, whereby dedicated elements are being replaced by more general-purpose devices, has been lately challenging this existing approach. Virtualizing the infrastructure through the softwarization can provide significant benefits to end users and operators, supporting more flexible service deployment, providing real time monitoring and operational changes.  In Paper I we study a novel allocation technique and traffic optimization process for the access network. Cellular network technologies (i.e. UMTS, LTE, LTE-A) will coexist with non-cellular small cells and offload traffic from cellular to non-cellular networks mainly operating in 3GPP Wi-Fi (IEEE 802.11 standards). This is a scenario for indoor wireless access implementations where offloading mechanisms can improve the QoS offered by the operators, and reduce the traffic handled by the access fronthaul. The analysis of a novel optimization algorithm exhibited a holistic solution for access-core interworking where LWA (LTE-WiFi Aggregation) offers improved performance for the end users.  In order to optimize core network operations factors such as the operational costs should be addressed. Following this approach in Paper II we analysed how environmental factors (e.g. temperature, humidity) can affect the power consumption of core network data centers (cooling systems). By applying machine learning techniques using data from a data center, we were able to forecast the power consumption based on to atmospheric weather conditions and analyse its accuracy.  Optimizing the access network operations and the interworking (resource allocation, scheduling, offloading) can lead to highly configurable and secure operations. These have been factors of great concern as wireless connectivity increases in denser populated areas. In Paper III we examine the physical layer secrecy aspects of a collaborative small cell network in the presence of parallel connections and caching capabilities at the edge nodes. Using tools from the probability theory, we examined how the power allocation for the transmissions can ensure secrecy in the presence of an eavesdropper.

Funding agencies: Europen Union's Horizon 2020 Marie Sk lodowska-Curie Actionsproject WiVi-2020 (H2020-MSCA-ITN-2014-EID 642743-WiVi-2020)

The use of an attached sunspace is one of the most popular passive solar heating techniques. One of the main drawbacks of the sunspace is getting over heated by the sun energy during the hot season of the year. Even in northern climates overheating could be problematic and there is a considerable cooling demand. Shading is one of the most efficient and cost effective strategies to avoid overheating due to the high irradiation especially in the summer. Another strategy is using ventilation system to remove the excess heat inside the sunspace. However this rejected energy can be captured and stored for future energy demands of the sunspace itself or nearby buildings. Therefore the Solar blind system has been considered here for the shielding purpose in order to reduce the cooling demand. By considering the PV/T panels as the solar blind, the blocked solar energy will be collected and stored for covering part of the heating demand and the domestic hot water supplies of the adjacent building.  From a modeling point of view, the sunspace can be considered as a small-scale closed greenhouse. In the closed greenhouse concept, available excess heat is indeed utilized in order to supply the heating demand of the greenhouse itself as well as neighboring buildings. The energy captured by PV/T collectors and the excess heat from the sunspace then will be stored in a thermal energy storage system to cover the daily and seasonal energy demand of the attached building. In the present study, a residential building with an attached sunspace with height, length and width of 3, 12 and 3.5 meters respectively has been assumed located in two different locations, Stockholm and Rome. Simulations have been run for the Solar blind system integrated with a short-term and a long-term TES systems during a year to investigate the influence of the sunspace equipped with a PV/T Solar blind on the thermal behavior of the adjacent building. The simulated results show that the Solar blind system can be an appropriate and effective solution for avoiding overheating problems in sunspace and simultaneously produce and store significant amount of thermal energy and electricity power which leads to saving considerable amount of money during a year.

Wind energy is a major part of renewable energy production. With fossil fuel depletion and climate change at the cusp, it is an absolute need to implement or evolve the current source or utilization of renewable energy. The wind has been dominating the onshore for many decades and offshore wind turbines are available at shallow depths.  To extract more wind energy source deep sea location is recommended. Also, in deep seas, ocean current energy is utilized very sparsely compared to the dominating wind and solar energy. So far no hybrid offshore horizontal axis and ocean current system are in existence. Based on the depth of the sea water the offshore floating structure is classified. Usually, for any floating structure stability is an apprehension. In an offshore floating structure, the damping with respect to the thrust force exerted on the wind turbine will affect the life of the wind turbine. During high wind speed, the angle of inclination would go up to about 4 degrees. The time required for the floating structure to come to rest may also be high. We present an analysis based on an existing floating structure which is a ballast stabilized the floating structure. In this paper, we add an additional submerged turbine and do a 2D analysis on the floating structure to find out whether the structure’s oscillation is well damped or not. We also discuss whether the weight of the submerged will influence the stability or by changing the radius of blades of the submerged turbine will affect the damping.

Geothermal energy is an important source of clean and renewable energy. This project deals with the study of deep geothermal power plants for the generation of electricity. The design involves the extraction of heat from the Earth and its conversion into electricity. This is performed by allowing fluid deep into the Earth where it gets heated due to the surrounding rock. The fluid gets vaporized and returns to the surface in a heat pipe. Finally, the energy of the fluid is converted into electricity using turbine or organic rankine cycle (ORC). The main feature of the system is the employment of side channels to increase the amount of thermal energy extracted. A finite difference computer model is developed to solve the heat transport equation. The numerical model was employed to evaluate the performance of the design. The major goal was to optimize the output power as a function of parameters such as thermal diffusivity of the rock, depth of the main well, number and length of lateral channels. The sustainable lifetime of the system for a target output power of 2 MW has been calculated for deep geothermal systems with drilling depths of 8000 and 10000 meters, and a financial analysis has been performed to evaluate the economic feasibility of the system for a practical range of geothermal parameters. Results show promising an outlook for deep geothermal systems for practical applications.

A reduced order model describing the energy and heading angle dynamics of a scramjet missile is developed using a singular perturbation technique. The cruise analysis is briefly reviewed to determine the conditions at which the missile will cruise most efficiently. The turn and climb performance of the missile over the conditions of interest is then examined and a family of extremal trajectories is constructed which asymptotically approach the cruise at an intermediate altitude.
Master of Science

As more countries progress towards renewable energy, intermittency in the power system is causing an unreliable power supply. Flexibility solutions from prosumers, which both consume and produce electricity, is one solution to provide stability to the power system. Households with both PV and energy storage are studied for this purpose in this thesis where the following flexibility services for both a household and the electricity grid of Sweden are studied: Increasing PV self-consumption, peak shaving, energy arbitrage at the day-ahead electricity market and providing the frequency regulation reserves FCR-N, FCR-D, aFRR and mFRR. Each house is assumed to have a 10 kW PV capacity and a battery capacity of 7.68 kWh. The services are studied in the software HOMER Grid and are modelled in different scales to see how the load in different aggregated levels affect the services. The case studies are a single family house, an overloaded transformer, an energy community and on a national scale. For the aggregated case studies, the potential capacity for PV will be based on the existing Swedish policies and the number of energy storages will be inspired by one the leading countries in Europe in energy storage installations, Germany. The results showed that for a single household the self-consumption and self-sufficiency increased the most with an addition of a battery. The battery was most efficient in peak shaving and reducing the overall electricity cost when the electricity fee targeted both the electricity consumption during peak hours and the monthly peaks. With this price scheme, the payback time of the battery and PV system is around 14 years. However, when the electricity fee is only targeting the electricity consumption during peak hours, the results showed that the monthly electricity demand peaks actually increase with an addition of a battery. For the aggregated case studies, it showed that decentralized batteries are not as effective in decreasing the electricity demand peaks if the peak lasts more than a few hours. On a national scale the results show that 20% of the aggregated batteries capacity is sufficient to provide around 70-100% of each of the frequency reserves individually. The highest savings are gained for the households when both the primary frequency reserves, FCR-N and FCR-D, are provided by the aggregated batteries together with increasing the PV self-consumption, peak shaving and energy arbitrage. The battery payback time is then reduced to 11 years. Based on a sensitivity analysis, the costs that affects the battery payback the most are the investment cost and the power fee.
I takt med att fler länder använder sig mer av förnybar energi, ökar opålitligheten i kraftsystemet på grund av förnybar energis intermittenta natur. Flexibilitetslösningar från konsumenter som kan både producera och konsumera el är en lösning för att förse stabilitet till kraftsystemet. Hushåll med både PV och batteri studeras för detta ändamål i detta examensarbetet där följande flexibilitetstjänster för både hushållet och elnätet studeras: Öka egenkonsumtionen av solel, kapning av effekttoppar, energiarbitrage samt tillhandahålla frekvensregleringens reserver FCR-N, FCR-D, aFRR och mFRR. Varje hus antas ha en 10 kW installerad kapacitet för PV och 7.68 kWh för batteriet. Tjänsterna studeras i programmet HOMER Grid och modelleras i olika skalor för att undersöka hur elkonsumtionen i aggregerade nivåer påverkar dessa tjänster. Fallstudierna är ett enskilt hus, en överbelastad transformator, en samling av hus samt i nationell skala. För de aggregerade fallstudierna kommer den potentiella kapaciteten för PV baseras på Energimyndighetens målbild för produktion av solel och antalet batterier är inspirerade av ett av de ledande länderna i Europa inom energiinstallationer, Tyskland. Resultaten visar att för ett enskilt hushåll ökar egenförbrukningen och självförsörjningen som mest med både batteri och PV. Batteriet var mest effektiv med att minska effekttopparna och den totala elkostnaden när eltariffen innehöll både effekttariffen och tidstariffen. PV systemet med batteriet hade då en återbetalningstid på 14 år. Med endast tidstariffer visar resultatet att de månatliga effekttopparna ökar med tilläggen av batteriet. För de aggregerade fallstudierna visar resultatet att decentraliserade batterier inte är lika effektiva att minska effekttopparna om de varar mer än några timmar. På nationell skala visar resultaten att 20% av den sammanlagda batterikapaciteten är tillräcklig för att förse cirka 70–100% av varje frekvensreserv. Den högsta besparingen för hushållen för den nationella fallstudien fås när både av de primära frekvensreserverna, FCR-N och FCR-D tillhandahålls av de aggregerade batterierna, tillsammans med tjänsterna för att öka PV-konsumtionen, kapning av effekttopparna och energiarbitrage. Batteriets återbetalningstid reduceras då till 11 år. Känslighetsanalysen visar att de kostnader som påverkar batteriets återbetalning mest är investeringskostnaden och effekttariffen.

By utilizing the electric motor as the propulsion system, the electric vehicle (EV) establishes a new bridge between renewable energies and our daily life, which meanwhile has to face with a brand new technical issue, namely the energy management and conversion. Then, the performance of energy conversion systems has become a new evaluation criteria for EVs. Accordingly, this study works on the analysis and control of the EV energy conversion system, including the secure charging system via wireless power transmission (WPT), advanced driving control via electric propulsion system, and bidirectional power interface via electromagnetic interference (EMI) mitigation technique. First, this study proposes a novel energy encryption algorithm for WPT systems. In the presented scheme, the energy can be encrypted by chaotically regulating the frequency of the power source based on the unpredictable security key. The authorized receptor can effectively receive the energy by simultaneously adjusting the circuit to decoding the encrypted energy based on the acquired security key, while the unauthorized receptor cannot obtain the energy without knowledge of the security key. In this study, both simulation and experimental results are provided to verify the feasibility of the proposed secure WPT system. Subsequently, this study proposes a new dynamic model of EV powering steering systems, by synthetically taking into account characteristics of the electric propulsion motor, driver’s operation, and uncertain disturbances caused by irregularities of the road surface. By using various nonlinear analysis methods, the unstable chaotic behaviors can be revealed in the power steering system, especially when the vehicle turns a concern at a high speed. Additionally, a new control algorithm is designed and implemented to stabilize the EV power steering system, and corresponding validity is also mathematically proved in this study. Thirdly, an integrated driving control system is designed based on the aforementioned dynamic analysis, which is used to enhance the stability and maneuverability performances of four-in-wheel independently-driven (4WID) EVs. By adopting the supervisor-actuator structure, the proposed driving control scheme not only effectively improves the performance of tracking reference paths, but also optimally distribute the desired yaw moment to each in-wheel motor. In this study, the mathematical proof and the simulation are both conducted to demonstrate the feasibility of the proposed integrated driving control strategy. Lastly, this study also works on the EMI issue caused by switch-mode energy conversion devices for EVs. In this section, a new pulse-width-modulation (PWM) method is designed by utilizing the random-like sequence, aiming to suppress the conducted peaky EMI over the whole power spectrum, thereby ensuring the working performance for electronic instruments in EVs. For demonstrating the effectiveness of the proposed soft-chaoizing scheme, this study takes two exemplifications such as the electric propulsion drive system and the bidirectional power interface for vehicle-to-grid (V2G) systems.
published_or_final_version
Electrical and Electronic Engineering
Doctoral
Doctor of Philosophy