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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Estudo do impacto da incorporação de usinas hidrelétricas a fio d’água no sistema interligado nacional

Gomes, Rafael de Oliveira 02 August 2012 (has links)
Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-04-20T19:23:49Z No. of bitstreams: 1 rafaeldeoliveiragomes.pdf: 1378975 bytes, checksum: acfbbb683eac1c9cda51ec90f2c5c8a6 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-04-24T16:51:01Z (GMT) No. of bitstreams: 1 rafaeldeoliveiragomes.pdf: 1378975 bytes, checksum: acfbbb683eac1c9cda51ec90f2c5c8a6 (MD5) / Made available in DSpace on 2017-04-24T16:51:01Z (GMT). No. of bitstreams: 1 rafaeldeoliveiragomes.pdf: 1378975 bytes, checksum: acfbbb683eac1c9cda51ec90f2c5c8a6 (MD5) Previous issue date: 2012-08-02 / O Plano Decenal de Expansão de Energia (EPE, 2010) apresenta a expansão da oferta (ainda não contratada) 100% atrelada à geração de energia baseada em fontes renováveis: hidrelétricas, eólicas e termelétricas com queima de biomassa. O incentivo a uma maior participação de fontes renováveis na matriz energética é uma atitude louvável do governo brasileiro que, de alguma forma, tenta minimizar a expansão contratada nos leilões de energia nova até o ano de 2008, fortemente baseada em termelétricas a óleo combustível. A maioria das hidrelétricas viáveis para o período está localizada na Região Amazônica e devido a restrições socioambientais não há previsão de implantação de usinas com reservatórios de regularização das vazões afluentes. A maior participação de hidrelétricas de grande porte sem reservatórios implica em consequências diversas para a operação do Sistema Interligado Nacional (SIN), tais como: menor manobra para controle de cheias; maior exigência dos reservatórios; e maior despacho termelétrico para atender às exigências sazonais da carga. Além disso, impactos comerciais podem ser vislumbrados, como maior volatilidade do Preço de Liquidação de Diferenças, aumento dos riscos hidrológicos de usinas participantes do MRE e maior despacho de usinas termelétricas por ordem de mérito econômico. O presente trabalho analisa problemas como a diminuição da capacidade de regularização plurianual dos reservatórios e a necessidade do aumento da participação térmica a fim de conservar a segurança energética do SIN. Utiliza o modelo NEWAVE para examinar diversos cenários de vazões afluentes, baseadas em séries hidrológicas históricas e sintéticas, analisando panoramas futuros e desdobramentos do mercado de energia. Ademais, realiza estudos quanto à opção da expansão da oferta de energia por grandes hidrelétricas a fio d’água em detrimento de usinas com reservatórios de regularização, para isso realiza simulações modificando as características físicas da UHE Jirau de forma a comparar os resultados entre as alternativas. / The Ten-year Plan for Expansion of Energy (EPE, 2010) presents the expansion of offer (not auctioned) 100% tied to power generation based on renewable sources: hydro, wind and thermal power plants with biomass burning. Encouraging greater participation in renewable energy sources is a commendable attitude of the Brazilian government that somehow tries to minimize the expansion contracted in the auctions of new energy by the year 2008, based heavily on fuel oil fired plants. Most hydroelectric ventures considered viable for the period is located in the Amazon region and due to social and environmental restrictions there is no provision for deployment of power plants with reservoirs of regularization of inflows. The high participation of large hydroelectric without reservoirs implies in several consequences for the operation of the National Interconnected System (SIN), such as reduced availability of maneuvers for flood control; a higher demand of the existing reservoirs; and order more frequently thermoelectric power plants to achieve the seasonal demands of the load. Moreover, trade impacts can be envisioned, such as increased volatility of the Settlement Price Differences, increased risks of hydrological plants participating in the MRE and higher order of power plants in order of economic merit. This paper analyzes problems such as decreased ability to multi-annual adjustment of the reservoirs and the need for increased participation in order to conserve thermal energy security of the SIN. Uses NEWAVE model to examine different scenarios of inflows based on historical hydrological series and synthetic overviews analyzing future market developments and energy. Moreover, studies carried out on the option of expanding the supply of energy by large dams to trickle over plants with reservoirs of regularization, for it carries out simulations by modifying the physical characteristics of UHE Jirau in order to compare the results among the alternatives.
42

Analýza nejistot hydrologických a provozních parametrů na vodohospodářské řešení zásobní funkce nádrže / Uncertainty Analysis of Hydrological and Operating Parameters on Water Management Analysis of Reservoir Storage Capacity

Paseka, Stanislav January 2016 (has links)
The aim of the thesis is to introduce the concept of Monte Carlo method for incorporating the uncertainties into the all hydrological and operational data inputs, which are needed to design and operation of large open water reservoir. Incorporating uncertainties into data inputs during calculation of reservoir storage capacity, then the consequent active conservation storage capacity is loaded by uncertainties. In the same way the values of outflow water from reservoir and hydrological reliability are affected by these uncertainties as well. For these kind of calculations the reservoir simulation model has been used, which simulate behavior operation of reservoir and is able to evaluate the results of simulations and help to reduction risk of storage capacity failure, respectively reduction of water shortages during reservoirs operation during low water and dry periods.
43

Numerical modeling and analysis of heat and mass transfers in an adsorption heat storage tank : Influences of material properties, operating conditions and system design on storage performances / Modélisation et analyse numériques des échanges de chaleur et de masse dans un réacteur de stockage de chaleur par adsorption : Influence des propriétés des matériaux, des conditions opératoires et du système sur les performances de stockage

Gondre, Damien 21 March 2016 (has links)
Le développement de solutions de stockage de l'énergie est un défi majeur pour permettre la transition énergétique d'un mix énergétique fortement carboné vers une part plus importante des énergies renouvelables. La nécessité de stocker de l'énergie vient de la dissociation, spatiale et temporelle, entre la source et la demande d'énergie. Stocker de l'énergie répond à deux besoins principaux : disposer d'énergie à l'endroit et au moment où on en a besoin. La consommation de chaleur à basse température (pour le chauffage des logements et des bureaux) représente une part importante de la consommation totale d'énergie (environ 35 % en France en 2010). Le développement de solutions de stockage de chaleur est donc d'une grande importance, d'autant plus avec la montée en puissance des énergies renouvelables. Parmi les technologies de stockage envisageables, le stockage par adsorption semble être le meilleur compromis en termes de densité de stockage et de maintient des performances sur plusieurs cycles de charge-décharge. Cette thèse se focalise donc sur le stockage de chaleur par adsorption, et traite de l'amélioration des performances du stockage et de l'intégration du système au bâtiment. L'approche développée pour répondre à ces questions est numérique. L'influence des propriétés thermophysiques de l'adsorbant et du fluide sur la densité de puissance d'une part, mais aussi sur la densité de stockage et l'autonomie du système, est étudiée. L'analyse des résultats permet de sélectionner les propriétés des matériaux les plus influentes et de mieux comprendre les transferts de chaleur et de masse au sein du réacteur. L'influence des conditions opératoires est aussi mise en avant. Enfin, il est montré que la capacité de stockage est linéairement dépendante du volume de matériau, tandis que la puissance dépend de la surface de section et que l'autonomie dépend de la longueur du lit d'adsorbant. Par ailleurs, le rapport entre l'énergie absorbée (charge) et relâchée (décharge) est d'environ 70 %. Mais pendant la phase de charge, environ 60 % de la chaleur entrant dans le réacteur n'est pas absorbée et est directement relâchée à la sortie. La conversion globale entre l'énergie récupérable et l'énergie fournie n'est donc que de 25 %. Cela montre qu'un système de stockage de chaleur par adsorption ne peut pas être pensé comme un système autonome mais doit être intégré aux autres systèmes de chauffage du bâtiment et aux lois de commande qui les régissent. Utiliser la ressource solaire pour le préchauffage du réacteur est une idée intéressante car elle améliore l’efficacité de la charge et permet une réutilisation de la part récupérée en sortie pour le chauffage direct du bâtiment. La part stockée sous forme sensible peut être récupérée plusieurs heures plus tard. Le système est ainsi transformé en un stockage combiné sensible/adsorption, avec une solution pour du stockage à long terme et pour du stockage à court terme. / The development of energy storage solutions is a key challenge to enable the energy transition from fossil resources to renewable energies. The need to store energy actually comes from a dissociation between energy sources and energy demand. Storing energy meets two principal expectations: have energy available where and when it is required. Low temperature heat, for dwellings and offices heating, represents a high share of overall energy consumption (i.e. about 35 %). The development of heat storage solutions is then of great importance for energy management, especially in the context of the growing part of renewable energies. Adsorption heat storage appears to be the best trade off among available storage technologies in terms of heat storage density and performances over several cycles. Then, this PhD thesis focuses on adsorption heat storage and addresses the enhancement of storage performances and system integration. The approach developed to address these issues is numerical. Then, a model of an adsorption heat storage tank is developed, and validated using experimental data. The influence of material thermophysical properties on output power but also on storage density and system autonomy is investigated. This analysis enables a selection of particularly influencing material properties and a better understanding of heat and mass transfers. The influence of operating conditions is also underlined. It shows the importance of inlet humidity on both storage capacity and outlet power and the great influence of discharge flowrate on outlet power. Finally, it is shown heat storage capacity depends on the storage tank volume, while outlet power depends on cross section area and system autonomy on bed length. Besides, the conversion efficiency from absorbed energy (charge) to released energy (discharge) is 70 %. But during the charging process, about 60 % of incoming heat is not absorbed by the material and directly released. The overall conversion efficiency from energy provided to energy released is as low as 25 %. This demonstrates that an adsorption heat storage system cannot be thought of as a self-standing component but must be integrated into the building systems and control strategy. A clever use of heat losses for heating applications (in winter) or inlet fluid preheating (in summer) enhances global performances. Using available solar heat for system preheating is an interesting option since a part is instantly retrieved at the outlet of the storage tank and can be used for direct heating. Another part is stored as sensible heat and can be retrieved a few hours later. At least, it has the advantage of turning the adsorption storage tank into a combined sensible-adsorption storage tank that offers short-term and long-term storage solutions. Then, it may differ avoidable discharges of the sorption potential and increase the overall autonomy (or coverage fraction), in addition to optimizing chances of partial system recharge.
44

CO2 storage in deep saline aquifers : Models for geological heterogeneity and large domains / 二氧化碳的深部盐水层地质封存 : 储层非均质性及大尺度模型的研究

Tian, Liang January 2016 (has links)
This work presents model development and model analyses of CO2 storage in deep saline aquifers. The goal has been two-fold, firstly to develop models and address the system behaviour under geological heterogeneity, second to tackle the issues related to problem scale as modelling of the CO2 storage systems can become prohibitively complex when large systems are considered. The work starts from a Monte Carlo analysis of heterogeneous 2D domains with a focus on the sensitivity of two CO2  storage performance measurements, namely, the injectivity index (Iinj) and storage efficiency coefficient (E), on parameters characterizing heterogeneity. It is found that E and Iinj are determined by two different parameter groups which both include correlation length (λ) and standard deviation (σ) of the permeability. Next, the issue of upscaling is addressed by modelling a heterogeneous system with multi-modal heterogeneity and an upscaling scheme of the constitutive relationships is proposed to enable the numerical simulation to be done using a coarser geological mesh built for a larger domain. Finally, in order to better address stochastically heterogeneous systems, a new method for model simulations and uncertainty analysis based on a Gaussian processes emulator is introduced. Instead of conventional point estimates this Bayesian approach can efficiently approximate cumulative distribution functions for the selected outputs which are CO2 breakthrough time and its total mass. After focusing on reservoir behaviour in small domains and modelling the heterogeneity effects in them, the work moves to predictive modelling of large scale CO2  storage systems. To maximize the confidence in the model predictions, a set of different modelling approaches of varying complexity is employed, including a semi-analytical model, a sharp-interface vertical equilibrium (VE) model and a TOUGH2MP / ECO2N model. Based on this approach, the CO2 storage potential of two large scale sites is modelled, namely the South Scania site, Sweden and the Dalders Monocline in the Baltic Sea basin. The methodologies developed and demonstrated in this work enable improved analyses of CO2 geological storage at both small and large scales, including better approaches to address medium heterogeneity. Finally, recommendations for future work are also discussed.
45

Systematisk optimering av transportskydd för anslutningsstudsar på plattvärmeväxlare / Systematic optimization of transport protection for connection nozzles on plate heat exchangers

Blennow, Emil, Österberg, John January 2020 (has links)
Ett sätt för företag att öka lönsamhet och behålla marknadsandelar och konkurrenskraft är att ständigt förbättra sina produkter genom systematisk produktutveckling. Alfa Laval AB i Ronneby tillverkar lödda plattvärmeväxlare som förses med skyddslock och/eller skyddspluggar i flera storlekar och varianter under transport. Syftet med studien är därför att optimera skyddet med avseende på arbetsmiljö, miljö, lagerkapacitet och till en likvärdig eller lägre kostnad. Målet är att generera förbättringsförslag som ersätter de nuvarande transportskydden med ett fåtal standardskydd. Studien genomfördes som en fallstudie och följde den ingenjörsvetenskapliga Systems Engineering-metoden Design For Six Sigma (DFSS). DFSS-processen är uppdelad i fyra steg för att på ett systematiskt sätt uppnå önskat resultat och generera förbättringsförslag till fallföretaget. Studien resulterade i ett förbättringsförslag i form av en krympfilm som ersättande transportskydd. Förbättringsförslaget genererade även en reducering av antal storlekar och varianter med 80 %, vilket i sin tur reducerade lagernivåer. / One way for companies to increase profitability and maintain market shares and competitiveness is to constantly improve their products through systematic product development. Alfa Laval AB in Ronneby manufactures soldered plate heat exchangers which are provided with protective covers and/or protective plugs in several sizes and variants during transport. The purpose of this study is, therefore, to optimize the protection with regard to the work environment, environment, storage capacity and at an equivalent or lower cost. The goal is to generate improvement proposals that replace the current transport protections with a few standard protections. The study was conducted as a case study and followed the Engineering Scientific Systems Engineering method Design For Six Sigma (DFSS). The DFSS process is divided into four steps in order to systematically achieve desired results and generate improvement proposals for the case company. The study resulted in an improvement proposal in the form of a shrink film as a replacement for the transport protection. The improvement proposal also generated a reduction of 80 % in the number of sizes and variants, which in turn reduced stock levels.

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