Dissertationen zum Thema „Stange energi“

Decisions made at the early stage of building and settlement design can greatly influence the energy performance of the built environment. However, the type of feasible design intervention and their impact strong depends on project: if it is a new development or a re-development, whether the setting of the project is urban or rural, etc. Utilizing Bysjöstrand EcoVillage as a case, the aim of this thesis is to improve the energy performance of a new development at its early design stage through the passive and active use of solar energy. The study evaluated the energy saving potential of various passive solar design strategies as well as the solar energy potential of the new development. The steps taken to reduce the energy consumption are focused on the annual heating demand of buildings, since it accounts for more than a half of the total energy consumed by the village. The energy saving potential of the following passive solar design approaches were considered: building siting, building orientation, windows-to-wall ratio (WWR) analysis and insulation thickness optimization from the economic perspective. Furthermore, an assessment of energy generation potential from on-site photovoltaic (PV) systems was conducted. The financial viability of each building’s PV system was also conducted. According to the results, the evaluated passive solar design strategies can reduce the annual heating energy consumption close to 17 %. Regarding onsite energy generation, electricity from roof-installed PV systems can cover over 100% of the annual energy consumption estimated for the residential lighting and equipment within the eco-village. In summary, this study has demonstrated that with the above design considerations a 50 % reduction of energy consumption from the utility grid is possible. This study is useful for architects, energy engineers, and other parties who are involved in residential buildings energy performance optimization.

The rising cost of energy, particularly in the form of electrical power is a concern for business and households predominately in rural regions of Western Australia. The higher ongoing costs due to aging assets and infrastructure make it a genuine expense that almost always has the customer looking for cheaper options. Two particular businesses commissioned a project for developing a renewable approach to help satisfy their demands which due to the size and nature of the operation required a medium scale system that was both economical and environmentally sustainable. The project purpose was to research and build the first stage or the “source” of a small prototype to address these concerns in the form of a Fully Sustainable Energy Module (FSEM). The objective is to compete or better the average cost per kilowatt hour of the Western Australian electricity suppliers, Horizon Power (HP) and those making up the South West Interconnected System (SWIS). While assessing the design options of the FSEM, various types of software were used extensively to assist in clarifying the optimum designs throughout the project for an initial theoretical approach. Designs such as a custom Parabolic/hyperbolic reflector and Fresnel lens directed to a Concentrator Solar Cell Receiver Assembly (CSCRA), coolant pumping for junction temperature control and simulation of multiple system configurations for electrical power requirements were assessed to maximise energy output per square metre of solar output. Building a prototype requires a sound knowledge base to ensure that it gives the output expected. Data that can assist inform decisions made to further enhance its operation giving the best possible design for final production. Developing an understanding of a feasibility study on the proof of concept for prototype building is further enhanced by researching the importance and structure of project plans and business expectations. It highlights that the strengths and weakness that need considering and help to show a route to a successful finished product. Prevalent was the design issue for the parabolic/hyperbolic reflector and the intricacies that exposed the difficulty in getting the system to work efficiently due to very small tolerances in construction. When finally settling with a Fresnel lens type the “source” of the FSEM prototype at the time of publication showed practical results of DC output of cell capacity and consistent hot water set at various temperatures showing solar energy transferred.

Tesis para optar al grado de Magíster en Ciencias de la Ingeniería, Mención Matemáticas Aplicadas
Memoria para optar al título de Ingeniero Civil Matemático
We consider risk-averse stochastic programming models for the Generation Expansion Planning problem for energy systems with here-and-now investment decisions and generation variables of recourse. The resulting problem is coupled both along scenarios and along power plants. We develop a new decomposition technique to solve the energy optimization problem, resulting from the combination of two existing procedures, one to deal with stochastic programming problems through decomposition for different realizations of the stochastic process representing the uncertain data, and the second one is a method aim to find solutions to nonsmooth optimization problems. More precisely, we combine the Progressive Hedging algorithm to deal with scenario separability, obtaining a separate subproblem for each scenario, and an inexact proximal bundle method to handle separability for different power plants in each subproblem. By suitably combining these approaches, if the evaluation errors of the proximal bundle method vanish asymptotically, then bundle method converges to an approximate solution to each scenario subproblem. Thus, under mild convexity assumptions, the Progressive Hedging algorithm generates a sequence that converges to a solution to the original problem. The methodology is satisfactorily assessed on a test instance of the Generation Expansion Planning problem, whose reduced size allows us to compare the results with those obtained when solving the problem directly, and without decomposition.
CONICYT-PFCHA/Magister Nacional/2018-22181067 y CMM Conicyt PIA AFB170001

In the interest of studying the propagation of shock waves, this work sets out to design, construct, and characterize a pneumatic accelerator that performs high-velocity flyer plate impact tests. A single stage gas gun with a dual diaphragm breach allows for a non-volatile, reliable experimental testing platform for shock phenomena. This remotely operated gas gun utilizes compressed nitrogen to launch projectiles down a 14 foot long, 2 inch diameter bore barrel, which subsequently impacts a target material of interest. A dual diaphragm firing mechanism allows the 4.5 liter breech to reach a total pressure differential of 10ksi before accelerating projectiles to velocities as high as 1,000 m/s (1570-2240 mph). The projectile’s velocity is measured using a series of break pin circuits. The target response can be measured with Photon Doppler Velocimetry (PDV) and/or stress gauge system. A vacuum system eliminates the need for pressure relief in front of the projectile, while additionally allowing the system to remain closed over the entire firing cycle. Characterization of the system will allow for projectile speed to be estimated prior to launching based on initial breach pressure.

This diploma thesis deals with the problematic of utilization of renewable energy sources in regional context. Thesis is divided into two main parts, which are theoretical and empirical. Theoretical part provides general view on renewables, describes its position according to fossil fuels, analysis its potential, ways of development and support. Practical part of the work analysis two projects of biogas stations and also evaluates its impacts on local development. These impacts are compared in the final part of the work and on its basics particular conclusions are drew.

The theme of this diploma thesis is design of recharging station for electrical cars. The result of this thesis is a conceptual design of this station. It summarizes technological, structural, economic, ergonomic and visual aspects with respect to current trends and technical solution.

In traditional planning process, energy analysts work on finalized architectural designs and have limited capability to amend inefficient energy features such as high aspect ratio. Energy efficiency being a major part of sustainable design, the need for performance-oriented design tools has become imminent. There is a wide range of energy simulation tools across the world. Crawley et al. (2005) proposes a plain comparison of the most common ones based on vendor-supplied information. The present report aims to identify simulation tools that can help architects making energy-efficient design decisions in early stage of building process and the most suitable programs will be tested on a standard case in Stockholm area with respect to their architecture, functionalities, usability and limitations.

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 57-59).
In a two-stage reverse osmosis (RO) system of finite size, there are two degrees of freedom not present in a single-stage RO system: distribution of RO elements between the two stages (system design), and feed pressures (system operation). In this study, we investigate the optimal system design and operation of a two-stage RO system with a mass-balance model and establish a lower bound for the energy savings achieved by the optimized two-stage system compared to a single-stage system. A two-stage RO system may consume more or less energy than a single-stage RO system of the same size and freshwater productivity, depending on the first-stage feed pressure and second-stage feed pressure. To minimize energy consumption, feed pressures should be chosen to minimize spatial variance in flux. The optimal element configuration places at least half the elements in the first stage; the exact configuration depends on feed salinity, recovery ratio, and membrane permeability. The greatest energy savings are achieved with a two-stage RO system that has both optimal element configuration and feed pressures. More energy can be saved by adding a stage when the thermodynamic least work of separation is larger. For a given feed salinity, energy savings from adding a second stage grow as recovery ratio increases. Brackish water feeds must be taken to high recovery ratios to achieve substantial energy savings; comparable savings can be achieved at lower recovery ratios for higher salinity feeds. We find that significant energy can be saved with the simplest two-stage RO design, at a system flux similar to today's RO plants and accounting for the effects of concentration polarization.
by Quantum J. Wei.
S.M.

A single-phase grid connected transformerless photovoltaic (PV) inverter for residential application is presented. The inverter is derived from a boost cascaded with buck converter along with a line frequency unfolding circuit. Due to its novel operating modes, high efficiency can be achieved because there is only one switch operating at high frequency at a time, and the converter allows the use of power MOSFET and ultra-fast reverse recovery diode. This dissertation begins with theoretical analysis and modeling of this boost-buck converter based inverter. And the model indicates small boost inductance will leads to increase the resonant pole frequency and decrease the peak of Q, which help the system be controlled easier and more stable. Thus, interleaved multiple phases structure is proposed to have small equivalent inductance, meanwhile the ripple can be decreased, and the inductor size can be reduced as well. A two-phase interleaved inverter is then designed accordingly. The double-carrier modulation method is proposed based on the inverterâ s operation mode. The duty cycle for buck switch is always one if the inverter is running in boost mode. And the duty cycle for boost switches are always zero if the inverter is running in buck mode. Because of this, the carrier for boost mode is stacked on the top of the carrier for buck mode, as a result, there is no need to compare the input and output voltage to decide which mode the inverter should operate in. And the inverter operates smoothly between these two modes. Based on similar concept, three advanced modulation methods are proposed. One of them can help further improve the efficiency, and one of them can help increase the bandwidth and gain, and the last one takes the advantage of both. Based on similar concept, another three dual-mode double-carrier based SPWM inverters are proposed. With both step-up and step-down functions, this type of inverter can achieve high efficiency in a wide range because only one switch operates at the PWM frequency at a time. Finally, the simulation and experiment results are shown to verify the concept and the tested CEC (California Energy Commission) efficiency is 97.4%. It performs up to 2% more efficiently better than the conventional solution.
Ph. D.

To achieve the aim of low carbon cities and zero energy districts, it is important to adapt the efficient technologies while maintaining the thermal comfort and sustainable environment. The new challenge in design and building new districts lies in a sustainable and smart way to minimize energy consumption and thus carbon emission. This challenge can be overcome by the use of early-stage energetic and environmental analysis of the planned districts, which can result in sustainable and efficient use of the resources. This thesis aims to assess the energy demand and the carbon emission for the proposed design of Jakobsgårdarna district in Borlänge, Sweden. The complete analysis of the neighbourhood is assessed through a tool - Urban Modeling Interface, a Rhinoceros-based plugin developed by the Sustainable Design Lab at Massachusetts Institute of Technology, USA. A base case scenario is evaluated for energetic performance, lighting, heating, cooling, hot water, daylight potential, walkability, and life cycle assessment. Then, a sensitivity analysis is addressed, in particular to evaluate the impact of daylight potential, archetypes, window to wall ratio, wall materials, future climate, and a possible lockdown, on energy consumption and carbon emission. In the base case, the analysis shows that preschool has the lowest specific energy consumption of 64.1 kWh/m2, while retail shops have the highest (92.2 kWh/m2) energy consumption. The simulated energy consumption of the offices and residential buildings is 72.1 kWh/m2, and 80.4 kWh/m2 respectively. The life cycle assessment reveals the advantage of the environment from building wooden houses instead of using concrete or masonry. The total embodied carbon for the whole district is 149.3 kgCO2/m2 divided as follow: 160.9 kgCO2/m2 for the school; 164.9 kgCO2/m2 for the offices, 159.6 kgCO2/m2 for the retail shops, 55.0 kgCO2/m2 for the wood residential buildings, 164.9 kgCO2/m2 for the masonry residential buildings. The sensitivity analysis explains exhaustively the influence, which has changes in the base case scenario. In particular, the future climate will decrease heating consumption due to the increase of the mean annual temperature and, on the other hand, increase cooling demand. While a possible lockdown to the district will rise consumption in residential buildings due to a higher use of equipment and lighting, but it will lower the energy use of offices and schools. The overall research results are expected to be useful to propose suggestions and recommendations for the next steps of design about Jakobsgårdarna district in Borlänge.

Although concentrated solar power can be used to produce power using traditional electricity generation, energy storage has become a problem due to the intermittent supply of solar energy. By using solar energy in chemical production processes, the solar energy can be stored in a useful chemical product. The purpose of this thesis will be to examine the possibilities of a new solar chemical cycle the produces iron and ethylene from hematite (a form of iron oxide) and ethane using concentrated solar power. These two products are important stepping stones in the production of steel and polymers. This process could allow for the current process of steel production to move away from processes using coal and towards a more sustainable process using the hydrogen formed from the ethane cracking process and solar energy. The thesis will include: (1) the development of a new solar powered iron and ethylene combined cycle, (2) a feasibility study of a Concentrated Solar Heat Supply System (CSHSS) being developed at Georgia Tech, and (3) an assessment of the proposed cycle. The assessment will include an estimate of production including a thermodynamic ASPEN model, assessment of research to realize actualization of the theoretical cycle, an exergy analysis, and a heat exchanger analysis for the exchange of heat between the CSHSS and the chemical process.

n this thesis project, a proposed architecture for the multiple input, single output conversion stage for the DC House was designed, simulated, and tested. This architecture allows for multiple different input sources to be used to create a single higher power output source. The design uses a DC-DC boost converter with a parallelable output which has been demonstrated to allow increased total output power as a function of the number of input sources available. The parallelable output has been shown to distribute load amongst the input sources relatively closely to optimize the system. This approach is also desirable since it allows for flexibility in multiple configurations it can be used in. The design was tested using hardware and data results show the performance met and exceeded the needs of the DC House project. Data was taken for configuration with 1, 2, 3, and 4 input sources providing greater than 600W of total output power at an efficiency of greater than 92%. This architecture demonstrates the possibility of expanding the total available power for a single output in proportion to the number of available input sources.

Améliorer la représentation de la couche limite stable constitue un des grands challenges de la prévision numérique du temps et du climat. Sa représentation est clé pour la prévision du brouillard, du gel des surfaces, des inversions de température, du jet de basse couche et des épisodes de pollution. De plus, à l'échelle climatique, la hausse de la température moyenne globale de l'air en surface impacte davantage les régions polaires : améliorer la représentation de la couche limite stable est un enjeu important pour réduire les incertitudes autour des projections climatiques. Depuis une quinzaine d'années, les exercices d'intercomparaison de modèles GABLS ont montré que le mélange turbulent dans la couche limite stable est généralement surestimé par les modèles de prévision du temps. En effet, de nombreux modèles intensifient artificiellement l'activité de leur schéma de turbulence afin d'éviter une décroissance inévitable du mélange lorsque la stabilité dépasse un seuil critique en terme de nombre de Richardson gradient. Ce problème numérique et théorique n'est pas en accord avec de nombreuses observations et simulations à haute résolution qui montrent une activité turbulente séparée en deux régimes : un régime faiblement stable dans lequel l'atmosphère est turbulente de manière continue et intense, et un régime très stable dans lequel la turbulence est très intermittente, anisotrope et faible en intensité. Ces travaux de thèse s'articulent autour de deux parties dont l'objectif principal est d'améliorer la paramétrisation de la turbulence dans le modèle atmosphérique de recherche Méso-NH développé conjointement par Météo-France et le Laboratoire d'Aérologie, et dans le modèle opérationnel AROME. Cette étude utilise une méthodologie communément employée dans le développement de paramétrisations qui consiste à comparer des simulations à très haute résolution qui résolvent les structures turbulentes les plus énergétiques (LES) à des simulations uni-colonnes d'un modèle méso-échelle. Plusieurs simulations 3D couvrant différents régimes de stabilité de l'atmosphère sont réalisées avec Méso-NH. Les limites du modèle LES en stratification stable sont documentées. Une première partie répond à la problématique de la surestimation du mélange dans le régime faiblement stable. Une expression originale pour la longueur de mélange est formulée. La longueur de mélange est un paramètre clé pour les schémas de turbulence associés à une équation pronostique pour l'énergie cinétique turbulente. Cette longueur de mélange non-locale combine un terme de cisaillement vertical du vent horizontal à une formulation existante qui repose sur la flottabilité. Le nouveau schéma est évalué dans des simulations 1D par rapport aux LES d'une part ; et dans le modèle opérationnel AROME par rapport aux observations de l'ensemble du réseau opérationnel de Météo-France d'autre part. Une deuxième partie apporte des éléments d'évaluation d'un schéma combinant deux équations pronostiques pour les énergies cinétiques et potentielles turbulentes. En condition stable, le flux de chaleur négatif contribue à la production d'énergie potentielle turbulente. L'interaction entre les deux équations d'évolution permet, via une meilleure prise en compte de l'anisotropie et d'un terme à contre gradient dans le flux de chaleur, de limiter la destruction de l'énergie turbulente dans les modèles. Dans les cas simulés, cette nouvelle formulation ne montre pas un meilleur comportement par rapport à un schéma à une équation pour l'énergie cinétique turbulente car le mécanisme d'auto-préservation n'est pas dominant par rapport au terme de dissipation. Il conviendra d'améliorer la paramétrisation du terme de dissipation dans le régime très stable
The modeling of the stable atmospheric boundary layer is one of the current challenge faced by weather and climate models. The stable boundary layer is a key for the prediction of fog, surface frost, temperature inversion, low-level jet and pollution peaks. Furthermore, polar regions, where stable boundary layer predominates, are one of the region with the largest temperature rise : the stable boundary layer modeling is crucial for the reduction of the spread of climate predictions. Since more than 15 years, the GABLS models intercomparison exercices have shown that turbulent mixing in the stable boundary layer is overestimated by numerical weather prediction models. Numerous models artificially strengthen the activity of their turbulence scheme to avoid a laminarization of the flow at a critical value of the gradient Richardson number. The existence of this threshold is only a theoretical and a numerical issues. Numerous observations and high-resolution numerical simulations do not support this concept and show two different regimes : the weakly stable boundary layer that is continuously and strongly turbulent; and the very stable boundary layer globally intermittent with a highly anisotropic and very weak turbulence. This thesis aims at improving the turbulence scheme within the atmospheric research model Méso-NH developped by Météo-France and the Laboratoire d'Aérologie, and the operational weather forecast model AROME. We use a traditional methodology based on the comparison of high-resolution simulations that dynamically resolve the most energetic turbulent eddies (Large-Eddy Simulations) to single-column simulations. Several LES covering the weakly and the very stable boundary layer were performed with Méso-NH. The limits of applicability of LES in stratified conditions are documented. The first part of the study deals with the overmixing in the weakly stable boundary layer. We propose a new diagnostic formulation for the mixing length which is a key parameter for turbulence schemes based on a prognostic equation for the turbulent kinetic energy. The new formulation adds a local vertical wind shear term to a non-local buoyancy-based mixing length currently used in Méso-NH and in the French operational model AROME. The new scheme is evaluated first in single-column simulations with Méso-NH and compared to LES, and then in the AROME model with respect to observations collected from the operational network of Météo-France. The second part presents a theoretical and numerical evaluation of a turbulence scheme based on two prognostic equations for the turbulent kinetic and potentiel energies. In stratified conditions, the heat flux contributes to the production of turbulent potential energy. The laminarization of the flow is then limited by a reduction of the destruction of the turbulent kinetic energy by a better representation of the anisotropy and a counter-gradient term in the heat flux. On the simulated cases, this new formulation behaves similarly than the scheme with one equation for the turbulent kinetic energy because the self-preservation mechanism is not dominant compared to the dissipation term. Further research should improve the turbulent kinetic energy dissipation closure in the very stable regime

Glucose and ketones are important energy substrates in the human body and brain. Their use is highly regulated depending on energy status which can vary according to multiple factors such as type of cell, fed or fasted state, type of diet, or health state. Use of either substrate is also subject to multiple homeostatic feedback loops. Energy substrate availability has implications in several disorders including declining cognitive function in the elderly. While glucose availability is known to decrease in elderly with cognitive deficits, it is unclear whether this also occurs in healthy elderly, either in the body or brain. Also unknown is whether, in healthy elderly, the use of ketones as energy substrates is affected, and whether ketones could be used as an alternative energy substrate in situations of a decline in glucose availability. A clearer understanding of the use of glucose and ketones in aging is necessary to determine whether declining energy substrate availability that may occur in the elderly is a contributing factor to cognitive deficits, a result of cognitive pathology, or simply a feature of the physiological aging process. Objective. The overall goal of the laboratory where this research was carried out is to ascertain whether alternate energy sources to glucose, i.e. ketones, may help alleviate the risk of declining cognitive function during aging. The specific objective of the research project presented in this thesis was to evaluate the metabolism of glucose and ketones in the healthy elderly compared to young or middle age subjects during mild, short-term ketosis induced by a ketogenic breakfast. Results. Elderly people in relatively good health have a similar capacity to produce ketones and to oxidize [superscript 13]C-glucose and [superscript 13]C-β-hydroxybutyrate as middle-aged or young adults. Discussion. The results of this project encourage further exploration of whether ketones could be used as and alternative energy substrate to glucose as, at least in healthy elderly, there is no impedance of raising plasma ketones in response to a ketogenic intervention. // Résumé : Introduction. Le glucose et les cétones sont des substrats énergétiques importants pour le corps et le cerveau humain. Leur utilisation est spécifiquement régulée selon I'état énergétique qui varie en fonction du type de cellule, de I'état nourrie ou à jeun, du type de diète, de I'état de la santé. L'utilisation est également régulée par des voies de rétrocontrôle homéostatique. La disponibilité des substrats énergétiques est impliquée dans plusieurs désordres, dont le déclin des fonctions cognitives, chez les personnes âgées où une diminution de la disponibilité du glucose est démontrée. Cependant, il n'est pas encore connu si cette diminution est présente chez les personnes âgées en bonne santé ; soit dans le corps ou le cerveau. La capacité d'utiliser les cétones comme substrats énergétiques chez les personnes âgées saines et la possibilité d'utiliser les cétones comme substrat énergétique alternatif dans le cas d'un déclin de la disponibilité de glucose sont inconnues. Une meilleure compréhension de I'utilisation du glucose et des cétones sera nécessaire pour clarifier si une diminution de la disponibilité des substrats énergétique contribue au déclin cognitif, se manifeste à la suite des pathologies cognitives, ou encore est simplement une caractéristique du processus physiologique du vieillissement. Objectif. L'objectif principal du laboratoire est de déterminer si les sources d'énergie alternatives au glucose, c'est-à-dire les cétones, pourraient ralentir le déclin cognitif chez les personnes âgées. L'objectif du projet de recherche de ce mémoire était d'évaluer le métabolisme du glucose et des cétones chez les sujets âgés, d'âge moyen, et jeune après la prise d'un déjeuner induisant une faible cétogénèse de courte durée. Résultats. Les personnes âgées en santé ont une capacité similaire au sujet d'âge moyen et jeune à produire des cétones et à oxyder le [indice supérieur 13]C-glucose et le [indice supérieur 13]C-β- hydroxybutyrate. Perspectives. Les résultats de ce projet incitent à continuer à explorer si les cétones pourraient être utilisés comme substrats énergétiques afin de contourner le problème d'un déclin de I'utilisation du glucose, car il n'y a aucun obstacle dans la production des cétones suite a une intervention cétonique chez des sujets âgées en bonne santé.

Le principe de récupération d'énergie est appliqué dans cette thèse à un système de micro-actionneur bistable sans fil, développé au laboratoire de Roberval. Le micro-actionneur bistable est composé de deux poutres antagoniste bistable, de deux éléments en alliage à mémoire de forme (SMA) et d'une source laser. Le faisceau laser est utilisé comme source de transfert d'énergie sans contact pour actionner les éléments SMA. A leur tour, les éléments SMA sont les composants de transition pour activer les faisceaux bistables entre ses deux positions stables. Dans ce contexte, l'objectif de cette thèse est de récolter différents types d'énergies disponibles inutilisées dans ce système. Pour commencer, l'énergie optique est récupérée en utilisant l'effet photovoltaïque transformant l'énergie optique en énergie électrique. De plus, du fait de l'échauffement ambiant, la différence de température est captée par effet thermoélectrique transformant cette différence de température en une différence de tension. L'objectif global est de créer deux différents systèmes pour la récupération d'énergie dans le système. Le premier système repose sur la récupération de l'énergie optique uniquement. Cette conception sera utilisée lorsque le micro-actionneur nécessite une énergie électrique supplémentaire sans nécessiter une grande vitesse d'actionnement. Cependant, lorsque la vitesse représente une priorité par rapport à l'énergie électrique demandée, le micro-actionneur bascule pour fonctionner dans le deuxième système de récupération d’énergie où les énergies optiques et thermiques sont récupérées alors que la vitesse d'actionnement du micro-actionneur est supérieure à la première conception
The principle of energy harvesting is applied in this thesis to a wireless bistable micro-actuator system, developed in the Roberval laboratory. The bistable micro-actuator is made up of an antagonistic pre-shaped double beams, two shape memory alloy (SMA) elements and a laser source. The laser beam is used as a contactless energy transfer source to actuate the SMA elements. At their turn, SMA elements are the transitional components to activate the bistable beams among its two stable positions. From this context, the aim of this thesis is to harvest different types of unused available energies in this system. To start with, optical energy is harvested using the photovoltaic effect transforming optical energy into electrical energy. Moreover, due to the environment heating, the difference in temperature is harvested using thermoelectric effect transforming this difference in temperature into a voltage difference. The overall objective is to create two different playgrounds of energy harvesting in the system. The first one relies on harvesting only the optical energy. This design will be used when the micro-actuator requires an additional electrical energy without requiring high speed of actuation. However, when the speed represents a priority comparing to the electrical energy in demand, the micro-actuator switches to operate in the second playground where optical and thermal energies are harvested while the speed of actuation of the micro-actuator is higher than the first design

Edifícios são responsáveis por cerca de 40% da demanda global de energia. Para reduzir este consumo utilizando métodos de avaliação de energia (Energy Assessment – EA), as primeiras etapas de projeto arquitetônico (Early Architectural Design Stages – EADS) são especialmente adequadas para implementar medidas eficientes com a melhor relação custo-benefício. Para integrar a EA na EADS, dois desafios principais devem ser abordados simultaneamente: (a) a (não-)amigabilidade para arquitetos dos modelos computacionais e (b) a confiabilidade dos resultados. Para realizar ambos os objetivos, é apresentado neste trabalho um ambiente para o desenvolvimento de ferramentas de aferição de energia em EADS (Framework for Energy Assessment Tools in Early Architectural Design Stages –FORwArDS) e uma metodologia de validação, a validação relativa (Relative Validation – RV). FORwArDS possui três componentes: o modelo de entrada, o modelo de avaliação e o modelo de saída, mas o trabalho concentra-se na criação de um modelo de entrada simplificado (Simplified Input Model – SIM) através da redução de parâmetros, da criação de valores alternativos para os parâmetros escolhidos e, por fim, passos de simplificação matemática e geométrica. A estrutura aberta do ambiente permite uma ampla variedade de aplicações em pesquisa, prática e educação. A metodologia de validação proposta baseia-se no conceito de que a contextualização dos resultados obtidos representa a mais importante contribuição para a orientação de projeto no EADS. Este trabalho confronta pares de resultados, representando a mudança de projetos arquitetônicos similares originados em dois modelos de entrada diferentes, visando avaliar a precisão de seus correspondentes. No estudo de caso, um SIM, proveniente de um modelo de projeto detalhado, é criado de acordo com as regras de simplificação descritas no FORwARrDS. Os resultados são apresentados e analisados permitindo conclusões sobre as principais contribuições deste trabalho. O trabalho apresenta uma ferramenta útil para o desenvolvimento de metodologias de simplificação de modelos e EA para arquitetos durante EADS.
Today’s buildings are responsible for about 40% of the global energy demand. To reduce energy consumption by using Energy Assessment (EA) methods, the Early Architectural Design Stages (EADS) are especially suitable to implement the best cost-benefit measures. To integrate EA into EADS, two main challenges must be simultaneously tackled: (a) the architect-(un)friendliness of computational models and (b) the results’ reliability. To accomplish both goals a Framework for Energy Assessment Tools in Early Architectural Design Stages (FORwArDS) and a validation methodology, Relative Validation (RV), is presented. FORwArDS feature three components: Input Model, Assessment Model, and Output Model, but focuses on the creation of a Simplified Input Model (SIM) throughout parameters reduction, the creation of alternative values for the chosen parameters and exemplary mathematical and geometrical simplification steps. In the case study, a SIM is created according to the exemplary simplification rules described in FORwArDS, springing from a detailed project model; a validation procedure follows the proposed methodology. The results are presented, analyzed and conclusions are drawn regarding the framework’s and validation methodology’s contributions to the improvement of the EADS. The framework’s open structure and the applicability of the validation methodology to any simulation contribute to the discussion about the integration problems of energy assessment in EADS and present useful tools for the creation and test of model simplification methodologies and EA for architects during EADS.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 173-177).
Simulation tools, when applied early in the design process, can considerably reduce the energy demand of newly constructed buildings. For a simulation tool to assist with design, it must be easy to use, provide feedback quickly, and allow rapid comparisons. Most existing tools do not meet these needs, usually because they were intended for modeling finalized building designs. Often there is no user interface, and it can take hours or days to prepare, run, and interpret results. Such tools are too sophisticated for design purposes. In this document the MIT Design Advisor is presented as a simple and rapid building energy simulation tool, developed specifically for architects and building designers. Conceptual building designs can be modeled quickly and without formal training. Results are interpreted graphically and displayed to the user in a simple user interface. Side-by-side comparisons of building designs can be made, allowing users to quickly learn which building components have the biggest impact on energy consumption (heating, cooling, and lighting), indoor daylight levels, and thermal comfort. User-specified building parameters are used together with local weather data to predict monthly and annual energy use. The heat transfer model used to make the energy predictions is explained in detail in this thesis. Calculation methods are given and validated. Agreement with existing models is quite good. The MIT Design Advisor is available at http://designadvisor.mit.edu.
by Bryan J. Urban.
S.M.

The dissertation presents a generalized control structure for two-stage power converters operated in a renewable energy power system for smart grid and micro grid systems. The generalized control structure is based on the two-loop average-mode-control technique, and created by reconstructing the conventional control structure and feedback configuration. It is broadly used for both dc-dc and dc-ac power conversion based on the two-stage converter architecture, while offering several functionalities required for renewable energy power systems. The generalized control structure improves the performance and reliability of renewable energy power systems with multiple functionalities required for consistent and reliable distributed power sources in the applications of the smart grid and micro grid system. The dissertation also presents a new modeling approach based on a modification of the subsystem-integration approach. The approach provides continuous-time small-signal models for all of two-stage power converters in a unified way. As a result, a modeling procedure is significantly reduced by treating a two-stage power converter as a single-stage with current sinking or sourcing. The difficulty of linearization caused by time-varying state variables is avoided with the use of the quasi-steady state concept. The generalized control structure and modeling approach are demonstrated using the two-stage dc-dc and dc-ac power conversion systems. A battery energy storage system with a thermoelectric source and a grid-connected power system with a photovoltaic source are examined. The large-signal averaged model and small-signal model are developed for the two demonstrated examples, respectively. Based on the modeling results, the control loops are designed by using frequency domain analysis. Various simulations and experimental tests are carried out to verify the compensator designs and to evaluate the generalized control structure performance. From the simulation and experimental results, it is clearly seen that the generalized control structure improves the performance of a battery energy storage system due to the unified control concept. The unified control concept eliminates transient over-voltage or over-current, extra energy losses, power quality issues, and complicated decision processes for multiple-mode control. It is also seen that the generalized control structure improves the performance of a single-phase grid-connected system through increased voltage control loop bandwidth of the active ripple current reduction scheme. As a result of the increased loop bandwidth, the transient overshoot or undershoot of the dc-link voltage are significantly reduced during dynamic load changes.
Ph. D.

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 104-108).
A variety of improvements to the MIT Design Advisor, a whole-building energy usage modeling tool intended for use during early design stages, are investigated. These include changes to the thermal mass temperature distribution and lighting requirement calculations, the formulation of a representative day scheme to reduce the number of days that need to be simulated to find energy usage for a full year, the creation of an optimization algorithm to allow users to improve on their designs, and the addition of an algorithm to predict potential savings from retrocommissioning (RCx) using a limited set of simple inputs. Design Advisor itself is also tested for usability, speed, and accuracy using three existing buildings. The frequency of thermal mass-related calculations is reduced by finding the limits of the semi-implicit Crank-Nicolson method before it begins to return physically implausible oscillatory temperature profiles. An effort is made to speed up lighting calculations using a multivariate regression analysis in place of a multiple-reflection-based illuminance model. Representative days are formed by creating an average and two extreme weather days per month using existing climatological data, reducing the number of simulated days per year from 365 to 72 (three per month, repeated once for training). Combined, these changes lead to reductions in run time of up to 50% with roughly 10% loss of accuracy. The optimizer leverages these run time improvements to rapidly find optimal building designs given a set of input constraints. Initially, a multistep multivariate regression is used to reduce the given search space and tighten the constraints. Then, a genetic algorithm is used to find the target solution. Initial tests of this combination have led to average reductions in energy usage of 25% given 6 minutes of calculation. To extend Design Advisor's applicability to existing buildings, an algorithm for predicting potential energy savings from RCx is implemented and tested. A database of 90 buildings that have undergone an RCx process and had their resulting energy savings documented has been collected. A k-nearest neighbors algorithm is used to evaluate the potential savings of test buildings based on this data set, operating on the assumption that similar buildings (in terms of location, size, and energy usage intensity) will present similar faults or opportunities for savings. While the average savings percentage prediction error is 0.02, the root-mean-square error is 12.4, which is greater than the actual savings potential of many buildings. Model validation is performed using three existing buildings; two in the Philadelphia area and one on MIT's campus. For energy types for which no building faults or other issues were later found (as in the MIT building), final usage predictions are found to be accurate to within a mean bias error of 11.2% to 2.6%. To improve upon these accuracies, further details about key building parameters and modes of operation would be required. These studies also inform further usability improvements, including reporting site (rather than primary) energy usage and expending reported electricity usage to include loads other than lighting.
by Andrew Mandelbaum.
S.M.

Food webs are structured by intricate nodes of species interactions which govern the flow of organic matter in natural systems. Despite being long recognized as a key component in ecology, estimation of food web functioning is still challenging due to the difficulty in accurately measuring species interactions within a food web. Novel tracing methods that estimate species diet uptake and trophic position are therefore needed for assessing food web dynamics. The focus of this thesis is the use of compound specific nitrogen and carbon stable isotopes and molecular techniques for assessing predator-prey interactions and energy flow in natural aquatic ecosystems, with a particular focus on the species links between phytoplankton and zooplankton. The use of δ15N amino acid values to predict organism trophic position are evaluated through a meta-analysis of available literature which included measurements from 359 marine species (article I). Through a controlled feeding study isotope incorporation in aquatic organisms, across both plant-animal and animal-animal species linkages is further assessed (article II). These studies showed that δ15N amino acid values are useful tools for categorizing animal trophic position. Organism feeding ecology influenced nitrogen trophic discrimination (difference in isotope ratio between consumer and diet), with higher discrimination in herbivores compared to omnivores and carnivores (article I). Nitrogen isotope trophic discrimination also varied among feeding treatments in the laboratory study (article II). The combined findings from articles I & II suggest that researchers should consider using group specific nitrogen trophic discrimination values to improve accuracy in species trophic position predictions.  Another key finding in the controlled laboratory study (article II) was consistently low carbon isotope discrimination in essential amino acids across all species linkages, confirming that these compounds are reliable dietary tracers. The δ13C ratios of essential amino acids were applied to study seasonal dynamics in zooplankton resource use in the Baltic Sea (article III). Data from this study indicated that zooplankton assimilate variable resources throughout the growing season. Molecular diet analysis (article IV) showed that marine copepod and cladoceran species ingested both autotrophic and heterotrophic resources. Evidence from both articles III & IV also revealed that zooplankton feed on a relatively broad range of diet items but not opportunistically on all available food sources. Mesozooplankton feeding patterns suggested that energy and nutritional flows were channelled through an omnivorous zooplankton food web including microzooplankton prey items. Overall the results of this thesis highlight that stable isotope ratios in specific compounds and molecular techniques are useful tracing approaches that improve our understanding of food web functioning.

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 4: Manuscript.

 

Thesis (M.S. in civil engineering)--Washington State University, August 2010.
Title from PDF title page (viewed on July 28, 2010). "Department of Civil and Environmental Engineering." Includes bibliographical references (p. 24-26).

According to the Swedish Government's set targets for energy use and environmental quality imposed by the European Union, the total energy per heated unit area in residential and commercial buildings will have to be decreased by 20% in 2020 and 50% by 2050 in relation to the annual consumption of 1995. The building sector should additionally be completely independent of fossil fuels for energy usage, with the increasing sector of renewable energy continuously growing until 2020. In its current state, the number of multistory buildings and single-family houses in Sweden exceeds 4 000 000 units. In order to attain the set goals, renovation of the existing housing stock is a necessity given its current relatively slow turnover. As a result of the Swedish Million Unit Program undertaken during 1965−1974, about 750 000 apartments are currently in need of renovation in order to meet today's building standards. Simultaneously, new buildings are built with energy efficiency in mind. In this study an early stage methodology is developed for building refurbishment that takes advantage of a multi-faceted approach. The methodology comprises of multiple dimensions related to a techno-economic, environmental and building occupancy approach. The work presented herein includes a thorough literature review of decision making tools within the built environment and identifies major research efforts in sustainable refurbishment. The technical aspect of this study deals with the proper identification of high-efficient insulation materials that would serve one of the set purposes of energy efficiency when utilized within building envelopes. Further, results are shown for case studies, in which economic investments in Vacuum Insulation Panels (VIPs) and a coupled heat and moisture transport for predefined configurations of VIPs with supplementary insulation of balcony slabs and wall cross-sections are considered. The developed methodology also examines simulations of the total energy consumption utilizing a set of different insulation materials such as mineral wool and VIPs, for a number of locations in Northern and Southern Europe. The research findings of this study identify several aspects of a new developed tool for decision making, to be used in sustainable renovation and refurbishment.

QC 20120918

Contact-less transfer of energy has always been a desired feature for systems that require reliable and durable power transfer across their moving parts. In rotary equipment in particular, slip-rings are the established solution with off-the-shelf and customised solutions readily available in the market. Despite the mature technology, slip-rings suffer wear and are prone to arcing, making frequent maintenance a necessity. In this project a rotating transformer is proposed as an alternative solution for contact-less transfer of energy across the revolving frame of an airborne electronic-scanning radar. This thesis is based on the hypothesis that the Phase-Shifted Full Bridge (PSFB) topology can efectively utilise the parasitic components of the rotating transformer to achieve efficient (over 90%) power conversion at the kW range. The first part of this work concentrates on the study of the magnetic interface and its electrical properties. Initially the magnetic structure of the transformer is studied in order to gain understanding of the effects of the physical layout of the component to its electrical behaviour. The problems of low magnetising and increased leakage inductance are quantified by measurements, calculations and finite element analysis. An accurate electrical model is built and used to calculate the transformer voltage and current gain. The second part of the research programme aims at the compilation of a design strategy for a PSFB incorporating a rotating transformer. An algorithm is presented, that optimises the magnetic component structure in order to achieve minimum switching losses and spread the conduction losses between the transformer and power switches. The last stage involves the evaluation of the design algorithm through prototyping and testing. Some topological variations are tested and compared with the original conventional PSFB converter. The thesis concludes with a discussion of the results and future challenges.

The subject of this thesis is to evaluate investments in biogas plant purchased by company AGRA Deštná, a.s., which is located in Deštná, near Jindřichův Hradec. The thesis is divided into two main parts. The theoretical part is devoted to theoretical assumptions of investment evaluation, grants, theories and legislation related to the biogas plant. The practical part of the thesis describes the current situation of the company, investment, and economic evaluation of investment in the construction of biogas plants.

This thesis is a proposal for a business plan for the construction of biogas plants. The first part is to find a theoretical basis of the work. The second section analyzes the current situation of the company. After a chapter with a proposal for investment in construction of biogas plants, the economic part and final part of the evaluation indicated the proposed solution.

The urgent need for a clean and sustainable power supply for wireless sensor nodes and low-power electronics in various monitoring systems and the Internet of Things has led to an explosion of research in substitute energy technologies. Traditional batteries are still the most widely used power source for these applications currently but have been blamed for chemical pollution, high maintenance cost, bulky volume, and limited energy capacity. Ambient energy in different forms such as vibration, movement, heat, wind, and waves otherwise wasted can be converted into usable electricity using proper transduction mechanisms to power sensors and low-power devices or charge rechargeable batteries. This dissertation focuses on the design, modeling, optimization, prototype, and testing of novel piezoelectric energy harvesters for extracting energy from human walking, bio-inspired bi-stable motion, and torsional vibration as an alternative power supply for wireless monitoring systems. To provide a sustainable power supply for health care monitoring systems, a piezoelectric footwear harvester is developed and embedded inside a shoe heel for scavenging energy from human walking. The harvester comprises of multiple 33-mode piezoelectric stacks within single-stage force amplification frames sandwiched between two heel-shaped aluminum plates taking and reallocating the dynamic force at the heel. The single-stage force amplification frame is designed and optimized to transmit, redirect, and amplify the heel-strike force to the inner piezoelectric stack. An analytical model is developed and validated to predict precisely the electromechanical coupling behavior of the harvester. A symmetric finite element model is established to facilitate the mesh of the transducer unit based on a material equivalent model that simplifies the multilayered piezoelectric stack into a bulk. The symmetric FE model is experimentally validated and used for parametric analysis of the single-stage force amplification frame for a large force amplification factor and power output. The results show that an average power output of 9.3 mW/shoe and a peak power output of 84.8 mW are experimentally achieved at the walking speed of 3.0 mph (4.8 km/h). To further improve the power output, a two-stage force amplification compliant mechanism is designed and incorporated into the footwear energy harvester, which could amplify the dynamic force at the heel twice before applied to the inner piezoelectric stacks. An average power of 34.3 mW and a peak power of 110.2 mW were obtained under the dynamic force with the amplitude of 500 N and frequency of 3 Hz. A comparison study demonstrated that the proposed two-stage piezoelectric harvester has a much larger power output than the state-of-the-art results in the literature. A novel bi-stable piezoelectric energy harvester inspired by the rapid shape transition of the Venus flytrap leaves is proposed, modeled and experimentally tested for the purpose of energy harvesting from broadband frequency vibrations. The harvester consists of a piezoelectric macro fiber composite (MFC) transducer, a tip mass, and two sub-beams with bending and twisting deformations created by in-plane pre-displacement constraints using rigid tip-mass blocks. Different from traditional ways to realize bi-stability using nonlinear magnetic forces or residual stress in laminate composites, the proposed bio-inspired bi-stable piezoelectric energy harvester takes advantage of the mutual self-constraint at the free ends of the two cantilever sub-beams with a pre-displacement. This mutual pre-displacement constraint bi-directionally curves the two sub-beams in two directions inducing higher mechanical potential energy. The nonlinear dynamics of the bio-inspired bi-stable piezoelectric energy harvester is investigated under sweeping frequency and harmonic excitations. The results show that the sub-beams of the harvester experience local vibrations, including broadband frequency components during the snap-through, which is desirable for large power output. An average power output of 0.193 mW for a load resistance of 8.2 kΩ is harvested at the excitation frequency of 10 Hz and amplitude of 4.0 g. Torsional vibration widely exists in mechanical engineering but has not yet been well exploited for energy harvesting to provide a sustainable power supply for structural health monitoring systems. A torsional vibration energy harvesting system comprised of a shaft and a shear mode piezoelectric transducer is developed in this dissertation to look into the feasibility of harvesting energy from oil drilling shaft for powering downhole sensors. A theoretical model of the torsional vibration piezoelectric energy harvester is derived and experimentally verified to be capable of characterizing the electromechanical coupling system and predicting the electrical responses. The position of the piezoelectric transducer on the surface of the shaft is parameterized by two variables that are optimized to maximize the power output. Approximate expressions of the voltage and power are derived by simplifying the theoretical model, which gives predictions in good agreement with analytical solutions. Based on the derived approximate expression, physical interpretations of the implicit relationship between the power output and the position parameters of the piezoelectric transducer are given.
Doctor of Philosophy
Wireless monitoring systems with embedded wireless sensor nodes have been widely applied in human health care, structural health monitoring, home security, environment assessment, and wild animal tracking. One distinctive advantage of wireless monitoring systems is to provide unremitting, wireless monitoring of interesting parameters, and data transmission for timely decision making. However, most of these systems are powered by traditional batteries with finite energy capacity, which need periodic replacement or recharge, resulting in high maintenance costs, interruption of service, and potential environmental pollution. On the other hand, abundant energy in different forms such as solar, wind, heat, and vibrations, diffusely exists in ambient environments surrounding wireless monitoring systems which would be otherwise wasted could be converted into usable electricity by proper energy transduction mechanisms. Energy harvesting, also referred to as energy scavenging and energy conversion, is a technology that uses different energy transduction mechanisms, including electromagnetic, photovoltaic, piezoelectric, electrostatic, triboelectric, and thermoelectric, to convert ambient energy into electricity. Compared with traditional batteries, energy harvesting could provide a continuous and sustainable power supply or directly recharge storage devices like batteries and capacitors without interrupting operation. Among these energy transduction mechanisms, piezoelectric materials have been extensively explored for small-size and low-power generation due to their merits of easy shaping, high energy density, flexible design, and low maintenance cost. Piezoelectric transducers convert mechanical energy induced by dynamic strain into electrical charges through the piezoelectric effect. This dissertation presents novel piezoelectric energy harvesters, including design, modeling, prototyping, and experimental tests for energy harvesting from human walking, broadband bi-stable nonlinear vibrations, and torsional vibrations for powering wireless monitoring systems. A piezoelectric footwear energy harvester is developed and embedded inside a shoe heel for scavenging energy from heel striking during human walking to provide a power supply for wearable sensors embedded in health monitoring systems. The footwear energy harvester consists of multiple piezoelectric stacks, force amplifiers, and two heel-shaped metal plates taking dynamic forces at the heel. The force amplifiers are designed and optimized to redirect and amplify the dynamic force transferred from the heel-shaped plates and then applied to the inner piezoelectric stacks for large power output. An analytical model and a finite model were developed to simulate the electromechanical responses of the harvester. The footwear harvester was tested on a treadmill under different walking speeds to validate the numerical models and evaluate the energy generation performance. An average power output of 9.3 mW/shoe and a peak power output of 84.8 mW are experimentally achieved at the walking speed of 3.0 mph (4.8 km/h). A two-stage force amplifier is designed later to improve the power output further. The dynamic force at the heel is amplified twice by the two-stage force amplifiers before applied to the piezoelectric stacks. An average power output of 34.3 mW and a peak power output of 110.2 mW were obtained from the harvester with the two-stage force amplifiers. A bio-inspired bi-stable piezoelectric energy harvester is designed, prototyped, and tested to harvest energy from broadband vibrations induced by animal motions and fluid flowing for the potential applications of self-powered fish telemetry tags and bird tags. The harvester consists of a piezoelectric macro fiber composite (MFC) transducer, a tip mass, and two sub-beams constrained at the free ends by in-plane pre-displacement, which bends and twists the two sub-beams and consequently creates curvatures in both length and width directions. The bi-direction curvature design makes the cantilever beam have two stable states and one unstable state, which is inspired by the Venus flytrap that could rapidly change its leaves from the open state to the close state to trap agile insects. This rapid shape transition of the Venus flytrap, similar to the vibration of the harvester from one stable state to the other, is accompanied by a large energy release that could be harvested. Detailed design steps and principles are introduced, and a prototype is fabricated to demonstrate and validate the concept. The energy harvesting performance of the harvester is evaluated at different excitation levels. Finally, a piezoelectric energy harvester is developed, analytically modeled, and validated for harvesting energy from the rotation of an oil drilling shaft to seek a continuous power supply for downhole sensors in oil drilling monitoring systems. The position of the piezoelectric transducer on the surface of the shaft is parameterized by two variables that are optimized to obtain the maximum power output. Approximate expressions of voltage and power of the torsional vibration piezoelectric energy harvester are derived from the theoretical model. The implicit relationship between the power output and the two position parameters of the transducer is revealed and physically interpreted based on the approximate power expression. Those findings offer a good reference for the practical design of the torsional vibration energy harvesting system.

The aim of this thesis is upgrading the existing remuneration system that supports employee performance, and thus performance across the organization. Analyze the current situation in the particular company and on that basis to suggest possible changes in the existing system of employee compensation. The work is detailed in the company BGS Energy Plus, Inc., which makes use of market opportunities in renewable energy.

A search for vector-like quarks (VLQs) decaying to a Z boson using multi-stage machine learning was compared to a search using a standard square cuts search strategy. VLQs are predicted by several new theories beyond the Standard Model. The searches used 20.3 inverse femtobarns of proton-proton collisions at a center-of-mass energy of 8 TeV collected with the ATLAS detector in 2012 at the CERN Large Hadron Collider. CLs upper limits on production cross sections of vector-like top and bottom quarks were computed for VLQs produced singly or in pairs, T_single, B_single, T_pair, and B_pair. The two stage machine learning classification search strategy did not provide any improvement over the standard square cuts strategy, but for T_pair, B _pair, and T_single, a third stage of machine learning regression was able to lower the upper limits of high signal masses by as much as 50%. Additionally, new test statistics were developed for use in the Neyman construction of confidence regions in order to address deficiencies in current frequentist methods, such as the generation of empty set confidence intervals. A new method for treating nuisance parameters was also developed that may provide better coverage properties than current methods used in particle searches. Finally, significance ratio functions were derived that allow a more nuanced interpretation of the evidence provided by measurements than is given by confidence intervals alone.

Autor no autoriza el acceso a texto completo de su documento hasta el 25/9/2020.
Ingeniero Civil Matemático
Se presenta un modelo para diseñar un plan de acción para la generación eléctrica que incorpora futuro riesgo de cambio en la política de energía renovable. El modelo permite un plan en múltiples etapas, en donde algunas decisiones pueden ser tomadas hoy y otras pospuestas al futuro, cuando la incerteza de un cambio de política es revelada. El modelo es lo suficientemente flexible para considerar diversas potenciales medidas de energías renovables, las cuales pueden ser implementadas por medio de penaltis, impuestos a la emisión de carbono, subsidios u otros. El modelo es resuelto por medio de una descomposición tipo Benders para poder lidiar con un problema de altas dimensiones como la planificación eléctrica de un país. Se muestra que la planificación en múltiples etapas muestras mejorías substanciales en términos de costos y reducción de riesgo. El modelo es implementado para el SIC (Sistema Interconectado Central de Chile), para 2 etapas o años objetivos, 2025 y 2035, en que se elaboraron 3 casos, el primero en el cual no hay cambios en políticas de energía renovable, el segundo en el cual desde el año 2035 hay un chance de que se imponga una política de impuesto a las emisiones de carbono y finalmente, el último caso en que en el año 2035 se impone una política de 33% de generación mínima renovable no convencional. Para los 3 casos mencionados anteriormente se tienen distintos portafolios energéticos, donde se puede apreciar el efecto que tiene cada cambio de política para el sistema de generación eléctrica de un país.

This thesis deals with the possibilities of using waste heat for power generation with a focusing on biogas plants (BGS). The produced biogas is mainly used for combustion in cogeneration units with internal combustion piston engines. The first part this paper describes the biogas plants. The division of BGS and the biogas processing is mentioned there. Another part is focused on the combined production of electricity and heat. The principles and description various types of cogeneration technologies are presented here. The following are specific options for waste heat utilization for biogas plants. The last section contains proposals to increase electricity production by the BGS with the steam engine and economic evaluation of these proposals is made.

Thesis is oriented on project construction universal apparatus for introduction and research effects deceleration and impact with possibility setting initial velocity. Basic application proposed test station is crash simulation for diagnostic safety belts. At first there're in work presented physical value that describe action in progress at impact, further safety belts, their testing and test . Considerable volume of work is devoted to project actuation, system obstruction kinetic energy and basic construction. Subsequently is presented proposed construction and performed strenght calculation. In the end there are summarized basic characteristics proposed construction, short financial opinion, process of installation and safety rules for using this equipment.

It has been argued that traditional building energy simulation methods can be a slow process, which often fails to integrate into the design process of architects at the early design stages. Furthermore, studies have shown that the actual energy consumption of buildings once built and in operation is often far greater than the energy consumption predictions made during design. The difficulty of simulating real-world systems, such as the stock market or buildings, is the lack of understanding of the complex, non-linear and random interactions that take place. This is in part due to the involvement of people, whose behaviour is difficult to predict. An alternative to simulating complex systems with mathematical models is an approach based on real-world data, where system behaviour is learned through observations. Display Energy Certificates (DECs) are a source of observed building 'behaviour' in the UK and machine learning, a subset of artificial intelligence, can predict global behaviour in complex systems. In view of this, this thesis presents research that explores a method to predict and communicate the operational energy use of buildings in real-time as early design and briefing parameters are altered interactively. As a demonstrative case, the research focuses on school design in England. Artificial neural networks, a machine learning technique, were trained to predict thermal (gas) and electrical energy use of school designs based on a range of design and briefing parameters. In order to generate data for the artificial neural networks to learn from, a building characteristics dataset was developed which contains real-world data on 502 existing school buildings across England. A product of this research is a user-friendly design tool based on the psychological principles of 'flow', aimed at non-simulation experts, such as architects. The tool is named the 'SEED Tool' (School Early Environmental Design Tool).

Understanding the relationship between diet, physical activity and health in humans requires accurate measurement of body composition and daily energy expenditure. Stable isotopes provide a means of measuring total body water and daily energy expenditure under free-living conditions. While the use of isotope ratio mass spectrometry (IRMS) for the analysis of 2H (Deuterium) and 18O (Oxygen-18) is well established in the field of human energy metabolism research, numerous questions remain regarding the factors which influence analytical and measurement error using this methodology. This thesis was comprised of four studies with the following emphases. The aim of Study 1 was to determine the analytical and measurement error of the IRMS with regard to sample handling under certain conditions. Study 2 involved the comparison of TEE (Total daily energy expenditure) using two commonly employed equations. Further, saliva and urine samples, collected at different times, were used to determine if clinically significant differences would occur. Study 3 was undertaken to determine the appropriate collection times for TBW estimates and derived body composition values. Finally, Study 4, a single case study to investigate if TEE measures are affected when the human condition changes due to altered exercise and water intake. The aim of Study 1 was to validate laboratory approaches to measure isotopic enrichment to ensure accurate (to international standards), precise (reproducibility of three replicate samples) and linear (isotope ratio was constant over the expected concentration range) results. This established the machine variability for the IRMS equipment in use at Queensland University for both TBW and TEE. Using either 0.4mL or 0.5mL sample volumes for both oxygen-18 and deuterium were statistically acceptable (p>0.05) and showed a within analytical variance of 5.8 Delta VSOW units for deuterium, 0.41 Delta VSOW units for oxygen-18. This variance was used as “within analytical noise” to determine sample deviations. It was also found that there was no influence of equilibration time on oxygen-18 or deuterium values when comparing the minimum (oxygen-18: 24hr; deuterium: 3 days) and maximum (oxygen-18: and deuterium: 14 days) equilibration times. With regard to preparation using the vacuum line, any order of preparation is suitable as the TEE values fall within 8% of each other regardless of preparation order. An 8% variation is acceptable for the TEE values due to biological and technical errors (Schoeller, 1988). However, for the automated line, deuterium must be assessed first followed by oxygen-18 as the automated machine line does not evacuate tubes but merely refills them with an injection of gas for a predetermined time. Any fractionation (which may occur for both isotopes), would cause a slight elevation in the values and hence a lower TEE. The purpose of the second and third study was to investigate the use of IRMS to measure the TEE and TBW of and to validate the current IRMS practices in use with regard to sample collection times of urine and saliva, the use of two TEE equations from different research centers and the body composition values derived from these TEE and TBW values. Following the collection of a fasting baseline urine and saliva sample, 10 people (8 women, 2 men) were dosed with a doubly labeled water does comprised of 1.25g 10% oxygen-18 and 0.1 g 100% deuterium/kg body weight. The samples were collected hourly for 12 hrs on the first day and then morning, midday, and evening samples were collected for the next 14 days. The samples were analyzed using an isotope ratio mass spectrometer. For the TBW, time to equilibration was determined using three commonly employed data analysis approaches. Isotopic equilibration was reached in 90% of the sample by hour 6, and in 100% of the sample by hour 7. With regard to the TBW estimations, the optimal time for urine collection was found to be between hours 4 and 10 as to where there was no significant difference between values. In contrast, statistically significant differences in TBW estimations were found between hours 1-3 and from 11-12 when compared with hours 4-10. Most of the individuals in this study were in equilibrium after 7 hours. The TEE equations of Prof Dale Scholler (Chicago, USA, IAEA) and Prof K.Westerterp were compared with that of Prof. Andrew Coward (Dunn Nutrition Centre). When comparing values derived from samples collected in the morning and evening there was no effect of time or equation on resulting TEE values. The fourth study was a pilot study (n=1) to test the variability in TEE as a result of manipulations in fluid consumption and level of physical activity; the magnitude of change which may be expected in a sedentary adult. Physical activity levels were manipulated by increasing the number of steps per day to mimic the increases that may result when a sedentary individual commences an activity program. The study was comprised of three sub-studies completed on the same individual over a period of 8 months. There were no significant changes in TBW across all studies, even though the elimination rates changed with the supplemented water intake and additional physical activity. The extra activity may not have sufficiently strenuous enough and the water intake high enough to cause a significant change in the TBW and hence the CO2 production and TEE values. The TEE values measured show good agreement based on the estimated values calculated on an RMR of 1455 kcal/day, a DIT of 10% of TEE and activity based on measured steps. The covariance values tracked when plotting the residuals were found to be representative of “well-behaved” data and are indicative of the analytical accuracy. The ratio and product plots were found to reflect the water turnover and CO2 production and thus could, with further investigation, be employed to identify the changes in physical activity.

The rupture of an aneurysm in subarachnoid hemorrhage (SAH) is a dramatic event causing a severe impact on the brain and a transient or permanent ischemic condition. Several types of responses to meet the challenges of SAH have been found in the acute phase, including activation of the hypothalamic-pituitary-adrenal (HPA) axis and the sympathetic nervous system, elevated levels of brain natriuretic peptide (BNP), and disturbances in cerebral and systemic metabolism. Cerebral metabolism and the endocrine stress response in the ultra-early phase was investigated in a novel porcine model of SAH in which autologous blood was injected to the anterior skull base. Early activation of the HPA axis was found with rapid elevation of adrenocorticotrophic hormone, cortisol and aldosterone. The peak values of these hormones were early and may be impossible to catch in patients. There were indications of a sympathetic nervous response with excretion of catecholamines in urine as well as plasma chromogranin-A elevation. Cerebral microdialysis suggested immediate substrate failure followed by hypermetabolism of glucose. The animal model seems suited for further studies of aneurysmal SAH. NT-proBNP was investigated in 156 patients with SAH, there was a dynamic course with increasing levels during the first 4 days of the disease. Factors predicting high NT-proBNP load included female sex, high age, high Troponin-I at admission, angiographic finding of an aneurysm and worse clinical condition at admission. High levels of NT-proBNP were correlated to factors indicating a more severe disease, suggesting the initial injury in aneurysmal SAH is an important factor in predicting high NT-proBNP during the acute stage of the disease. Measurements with indirect calorimetry were performed daily during the first week after SAH on 32 patients with SAH. There was a dynamic course with increasing energy expenditure (EE) the first week after SAH. Comparisons with three predictive equations indicated that measured EE generally is higher than predicted, but considerable variation exists within and between patients, indicating that prediction of EE in SAH is difficult. Altogether, the studies demonstrate a complicated response in acute SAH that needs to be further studied to increase possibility of good outcome in SAH patients.

Thesis advisor: Dunwei Wang
Non-aqueous Li-O2 batteries promise the highest theoretical specific energy among all rechargeable batteries. It is the only candidate that can be comparable with the internal combustion engine in terms of gravimetric energy density. This makes Li-O2 batteries preferable in the application of electric vehicles or drones. However, the materialization of this technology has been hindered by the poor cycling performance. The major reason for the degradation of the battery at the current research stage has been identified as the decomposition of the electrolyte and the cathode. These parasitic reactions will lower the yield of the desired product and induce huge overpotential during the recharge process. By carefully examining the degradation mechanism, we have identified the reactive oxygen species as the culprit that will corrode the cathode and attack the organic solvents. While parallel efforts have been devoted to reduce the reactivity of these species toward electrolyte, the main focus of this thesis is to identify suitable material platforms that can provide optimum performance and stability as cathodes. A bio-inspired wood-derived N-doped carbon is first introduced to demonstrate the benefit of hierarchical pore structures for Li-O2 cathodes. But the instability of the carbon cathode itself limits the lifetime of the battery. To improve the stability of carbon, we further introduce a catalytic active surface coating of FeOx on a three dimensionally ordered mesoporous carbon. The isolation of carbon from the reactive intermediates greatly improves the stability of the cathode. Yet the imperfections of the protection layer on carbon calls for a stable substrate that can replace carbon. TiSi2 is explored as the candidate. With the decoration of Pd catalysts, the Pd/TiSi2 cathode can provide extraordinary stability toward reactive oxygen species. But this composite cathode suffers from the detachment of the Pd catalyst. A Co3O4 surface layer is further introduced to enhance the adhesion of the catalyst, which doubles the lifetime of the cathode. To achieve a fully stable cathode, Ru catalyst with stronger adhesion on TiSi2 directly is explored and identified to be robust in the operating conditions of Li-O2 batteries. The expedition for stable cathodes in Li-O2 batteries is expected to provide a clean material platform. This platform can simplify the study in evaluating the effectiveness of catalysts, the reaction mechanism at the cathode and the stability of the electrolyte. Toward the end of this thesis, an exploration is made to enable rechargeable Mg metal battery with a conversion Br2 cathode. This new system can avoid the dendritic growth of Li metal by the adoption of Mg as the anode and can promise better cathode kinetics by forming a soluble discharge product
Thesis (PhD) — Boston College, 2017
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Chemistry

In this thesis, the numerical solution of time-dependent partial differential equations (PDE) is studied. In particular high-order finite difference methods on Summation-by-parts (SBP) form are analysed and applied to model problems as well as the PDEs governing aerodynamics. The SBP property together with an implementation of boundary conditions called SAT (Simultaneous Approximation Term), yields stability by energy estimates. The first derivative SBP operators were originally derived for Cartesian grids. Since aerodynamic computations are the ultimate goal, the scheme must also be stable on curvilinear grids. We prove that stability on curvilinear grids is only achieved for a subclass of the SBP operators. Furthermore, aerodynamics often requires addition of artificial dissipation and we derive an SBP version. With the SBP-SAT technique it is possible to split the computational domain into a multi-block structure which simplifies grid generation and more complex geometries can be resolved. To resolve extremely complex geometries an unstructured discretisation method must be used. Hence, we have studied a finite volume approximation of the Laplacian. It can be shown to be on SBP form and a new boundary treatment is derived. Based on the Laplacian scheme, we also derive an SBP artificial dissipation for finite volume schemes. We derive a new set of boundary conditions that leads to an energy estimate for the linearised three-dimensional Navier-Stokes equations. The new boundary conditions will be used to construct a stable SBP-SAT discretisation. To obtain an energy estimate for the discrete equation, it is necessary to discretise all the second derivatives by using the first derivative approximation twice. According to previous theory that would imply a degradation of formal accuracy but we present a proof that this is not the case.

The goal of my thesis is to evaluate the importance of maize in biogas plants. The questionnaire was made to determine the parameters of hybrid corn, its harvest, subsequent silage, inclusion in the daily batch of biogas plants, and various technical and economic parameters. Twenty five biogas plants were addressed to participate in the survey. Despite the promise of anonymity, the data were obtained from only six biogas plants. Biogas plants are located in different regions of the Czech Republic, at different altitudes. The sixth and the last biogas plant is located in Austria.

The topic of the thesis is biogas stations - renewable energy sources. This thesis focuses on energy from biomass which is generated inside stations, and on appropriate use of energy. It deals with thermal energy that is produced as a waste product inside the biogas stations. The main objective is to evaluate the effectiveness of the biogas stations as a source of heat for the municipalities in southern Bohemian and create evaluation criteria of suitability of using heat from biogas stations in specific communities.

In Mobile Ad-hoc Networks, cluster based routing protocol(CBRP) is robustly used since they combine the advantages of Reactive and Proctive routing protocols. And they have less routing overhead and less end-to-end delay compared to Reactive and Proctive routing protocols respectively. Energy source for a mobile node is limited, and even difficult to recharge. The life time of the network depends on the life time of the nodes. So we propose different shemes to have energy efficient stable clusters. By using stable clustering algorithm to avoid frequent reclustering, efficient clustering scheme to minimize overlapping clusters, and allow nodes to save their energy by changing their mode to sleep mode.

博士
國立成功大學
電機工程學系
89
As opposed to conventional two-stage designs, a single stage photovoltaic (PV) energy conversion system is implemented, resulting in size and weight reduction and increased efficiency. The nonlinear output power relation of versus and the near linear relation of versus are discussed. Using as an index for current control is easier than voltage control, allowing a simpler design. The proposed current controller allows a PV energy conversion system to track the maximum power point very rapidly and smoothly. In addition, single current loop controller simplifies the conventional double loop design. The proposed controller performs maximum power point tracking (MPPT) and provides power to utilities with a unity power factor. Further, the proposed controller architecture is employed to the single-phase three-wire photovoltaic energy conversion system. The proposed system employs a three-leg inverter to control the MPPT process, the line current and neutral line current. A neutral line mode controller maintains a utility neutral line current to be zero. A line mode controller controls the line current so as to provide power to the utility with a unity power factor. The proposed system acts as a solar generator on sunny days and functions as an active power filter on rainy or cloudy days. In this thesis, the voltage and current hybrid PWM inverters using fuzzy variable structure control technique is proposed for parallel operation. The voltage-controlled PWM inverter (VCPI) unit is developed to provide a specific sinusoidal output voltage and the current-controlled PWM inverter (CCPI) units are employed to track the distributive current. Each of the VCPI and CCPI units can be operated independently. By using the fuzzy variable structure control scheme, the parallel inverters can provide excellent performance without phase-lock-loop (PLL) circuit for synchronization. The proposed scheme can result in fast dynamic response and robustness to parameter variations. Finally, computer simulations and experimental results demonstrate the superior performance of the proposed technique.

碩士
國立成功大學
電機工程學系碩博士班
93
In this thesis, a controller IC of signal-stage photovoltaic energy conversion system is designed by cell-based IC design flow. The advantages of the study are to reduce the circuit volume and to finish a SoC (System on Chip) product. In this study, the Verilog HDL code is written, then the code is downloaded into FPGA (Field Programmable Gate Array) chip in order to verify the functions. After the grammar and functions are corrected, the prototype chip is finished by TSMC 0.35 Cell-based Design Flow. Both the stand-alone mode and the utility mode are employed into the controller chip. The system is developed to provide the 110V/60Hz sinusoidal output voltage by voltage-controlled mode and deliver real power to the load. The excess power is supported to utility line with nearly unity power factor by current-controlled mode. Finally, experimental results of the 1kW PV energy conversion system are performed to verify the FPGA functions and simulation results of EDA (Electronic Design Automation) tool are executed to demonstrate the design of digital controller chip.