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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.
381

Modelling and Simulation to Improve Antimalarial Therapy

Lohy Das, Jesmin Permala January 2017 (has links)
The introduction of artemisinin-based combination therapy (ACT) substantially reduced malaria-related mortality and morbidity during the past decade. Despite the widespread use of ACT, there is still a considerable knowledge gap with regards to safety, efficacy and pharmacokinetic properties of these drugs, particularly in vulnerable populations like children and pregnant women. In addition, there is growing evidence of widespread artemisinin-resistance across the Greater Mekong Subregion. Expedited delivery of novel antimalarial drugs with different mechanisms of action to the clinical setting is still far off; therefore, it is crucial to improve the use of existing antimalarial drugs for optimal outcome in order to prolong their therapeutic life span. This thesis focuses on utilizing pharmacometric tools to support this effort for malaria prevention and treatment. An extensive simulation framework was used to explore alternative malaria chemopreventive dosing regimens of a commonly used ACT, dihydroartemisinin-piperaquine. Different monthly and weekly dosing regimens were evaluated and this allowed an understanding of the interplay between adherence, loading dose and malaria incidence. A weekly dosing regimen substantially improved the prevention effect and was less impacted by poor adherence. This is also expected to reduce selection pressure for development of resistance to piperaquine. Population pharmacokinetics-pharmacodynamic models were developed for artesunate and the active metabolite dihydroartemisinin, effect on parasite clearance, in patients with artemisinin-resistant and -sensitive malaria infections in Southeast Asia. The modeling identified an association between parasite density and drug bioavailability. It predicted the presence of high levels of artemisinin resistant infection among patients in Cambodia and its spread into Myanmar. A nomogram to identify patients with artemisinin resistant infections was developed. Furthermore, the model was used to demonstrate the need for extended treatment duration to treat patients with artemisinin resistant infections. A population pharmacokinetic model developed from data on pregnant women in East Africa allowed further understanding of artemether-lumefantrine exposure in pregnant populations. It also suggested that the lumefantrine exposure in this population is not compromised. In summary, the results presented in this thesis demonstrate the value of pharmacometric approaches for improving antimalarial drug treatment and prevention. This ultimately contributes to overcoming the prevailing challenges to malaria control.
382

Utilizing Energy Storage Applied on Floating Wind Turbine Economics Using a Spot-Price Based Algorithm

Johansson, Jim January 2017 (has links)
In this paper, a new algorithm for utilizing energy storage is proposed and applied on floating wind turbine economics. The proposed algorithm’s decision making on storing energy or selling electricity onto the grid is based on the electricity price, which makes it unique and different from similar algorithms. From the literature review, it was concluded Ocean Renewable Energy Storage to be most suitable with the Spar-Type and Semi-Submersible floating wind turbine to which the paper is based upon. The objective of this paper is to find the suitable ratio of energy storage versus wind farm, find the product of increase in wholesale, and evaluate whether the proposed method makes the hybrid economically sound. The algorithm was applied on spot-price data from Denmark due to its large share of wind energy with wind data from off the coast of Morro Bay in California, USA. Additionally, a sensitivity analysis is applied to evaluate to energy storage cost impact as well as evaluate the algorithm by lowering the required energy storage size.   Using the algorithm, the wind farm must account for nine days’ worth of energy production with a product of energy storage versus wind farm ratio of 1.42. The wholesale price increased with 11.9-21.5% for the four years studied, however, all financial results favored not utilizing energy storage. By the results derived from the sensitivity analysis, it was concluded that with future cost reductions, the algorithm will still favor no energy storage. However, by fine tuning the algorithm to reduce the need for storage, positive financial result might be achievable. The key to achieve a profitable result seems to rely on minimizing the need for energy storage, to which the proposed algorithm fail to achieve. Conclusively, spot-price decision-based energy storing is not economically sound.
383

Comparaison de la production de trois technologies différentes de panneaux solaires en fonctionnement réel avec suivi du soleil et intégration de batteries lithium innovantes adaptées au stockage des énergies intermittentes / Comparison of the production of three technologies different from solar panels in real functioning with follow-up of the sun and the integration of battery lithium innovative adapted to the storage of the intermittent energies

Goemaere, Loïc 16 December 2011 (has links)
Dans une vision de développement durable et d'indépendance énergétique visant l'intégration massive des énergies renouvelables à moyen terme dans le mix énergétique, les travaux menés au cours de cette thèse se sont axés sur deux thématiques :- d'une part, la comparaison de la production de trois technologies différentes de panneaux solaires (silicium, silicium avec concentration, CdTe) en fonctionnement réel dans une centrale photovoltaïque au sol dotée du suivi deux axes de la course du soleil ;- d'autre part et étant donné la nature intermittente de l'énergie photovoltaïque et son non-synchronisme avec la consommation, le développement et l'intégration de batteries à base de lithium comme moyen de stockage électrochimique de l'énergie photovoltaïque. L'approche est novatrice et a permis l'étude de nouveaux composés d'électrodes étudiés sous contraintes photovoltaïques réelles et utilisant différentes stratégies de restitution de l'énergie en vue du déploiement prochain des réseaux intelligents. Les simulations portent sur des accumulateurs de petites tailles classiquement utilisés dans les laboratoires de recherche mais préfigurant ce qui pourra être construit à plus grande taille. / In a vision of sustainable development and energy independence aiming at the massive integration of the medium-term renewable energies in the energy mix, the research works are centered on two themes:- On one hand, the comparison of the production of three technologies different from solar panels (silicon, silicon with concentration, CdTe) installed into a photovoltaic power plant with 2-axes sun tracking;- On the other hand and given the intermittent nature of the photovoltaic energy and its non-simultaneity with the consumption, the development and the integration of batteries with lithium as means of electrochemical storage of the photovoltaic energy. The approach is innovative and allowed the study of new compounds of electrodes studied under real photovoltaic constraints and using various strategies of return of the energy with the aim of the next deployment of the intelligent networks. The simulations concern batteries of small sizes classically used in research laboratories but prefiguring what can be built in bigger size.
384

Lesões em DNA promovidas por ácido 5-aminolevulínico: uma proposta de bases moleculares para hepatomos associados a porfirinopatias / DNA damage induced by 5-aminolevulinic acid: a molecular basis proposal for the hepatomas associated to porphyrinopathies

Janice Onuki 01 August 2000 (has links)
O ácido 5-aminolevulínico (ALA) é o primeiro precursor do grupo heme acumulado, principalmente no fígado, em alguns tipos de porfirias hepáticas hereditárias (porfiria aguda intermitente-AIP e tirosinemia) ou adquiridas (intoxicação por chumbo) devido à diminuição da atividade da enzima porfobilinogênio deaminase. Amostras de biópsias de fígado de pacientes portadores de AIP revelaram alterações estruturais nas mitocôndrias e no retículo endoplasmático, acúmulo de lipofuscina, gordura e corpúsculos de ferritina. Têm sido demonstrado que mutações mitocondriais induzidas por pró-oxidantes também contribuem para o envelhecimento celular e para o desenvolvimento do câncer. Esses dados podem estar relacionados à maior incidência de carcinoma hepatocelular (HCC) em pacientes sintomáticos de AIP. In vitro, ALA produz espécies reativas de oxigênio (ROS), através da oxidação catalisada por metais, e pode ser visto como uma fonte endógena de ROS, iniciando danos oxidativos a estruturas celulares como o DNA, podendo estar envolvido na iniciação e promoção do câncer. Além disso, o produto final de oxidação do ALA, o ácido 4,5-dioxovalérico (DOVA) é capaz de induzir modificações nas bases do DNA como outros derivados carbonílicos reativos. Neste estudo, demonstramos que o ALA é capaz de produzir danos ao DNA como quebras de fita de DNA plasmidial, aumento do nível de 8-oxo-7,8- dihidro-2\'-desoxiguanosina e 5-hidroxi-2´-desoxicitidina em DNA de órgãos de ratos tratados com ALA e aumento da formação de diversas bases modificadas em DNA de timo de bezerro. O DOVA reagiu com 2´-desoxiguanosina e DNA de timo de bezerro isolado produzindo dois adutos diastereoisômeros. O ALA e o DOVA foram capazes de aumentar a mutagenicidade em S. typhimurium TA104 e induzir resposta SOS em E. coli PQ37. Danos ao DNA mitocondrial e nuclear também foram detectados através da técnica de reação quantitativa em cadeia da polimerase em fibroblastos humanos transformados tratados com ALA. Todos esses dados fornecem informações referentes ao potencial genotóxico do ALA e permitem estabelecer uma proposta de bases moleculares para conectar as lesões ao DNA promovidas pelo ALA com a maior incidência de carcinoma hepatocelular em pacientes sintomáticos de AIP. / 5-Aminolevulinic acid (ALA) is a heme precursor accumulated in some inborn (acute intermittent porphyria-AIP and tyrosinosis) or acquired (lead poisoning) types of hepatic porphyria. In AIP patients, ALA is overproduced and accumulated in the liver. Liver biopsy samples of AIP patients revealed mitochondrial and endoplasmic reticulum structural alterations and accumulation of lipofucsin, fat and ferritin bodies. Mitochondrial mutations induced by pro- oxidants were suggested to contribute to cellular aging and cancer. These findings may be connected to the higher frequency of hepatocellular carcinoma (HCC) associated to symptomatic AIP patients. In vitro, ALA produces reactive oxygen species (ROS) upon metal- catalyzed oxidation and can be viewed as a deleterious endogenous source of ROS, triggering oxidative damage to cell structures and organs and being involved in the initiation and promotion of cancer. Besides, the final oxidation product of ALA, the 4,5-dioxovaleric acid (DOVA) is expect to induce DNA base modifications as already shown for other reactive carbonyl derivatives. In this study we demonstrated that ALA is able to produce DNA lesions such as strand breaks in plasmid DNA, increased steady state level of 8-oxo-7,8- dihydro-2\'-deoxyguanosine and 5-hydroxy-2´-deoxycytidine in rat organs DNA of ALA-treated rats and increased formation of several modified DNA bases in calf thymus DNA. 4,5-Dioxovaleric acid was showed to react with 2\'-deoxyguanosine and isolated calf thymus DNA through Schiff?s base formation to produce two diastereisomeric adducts. Aminolevulinic acid and DOVA were able to increase mutagenicity of the S. typhimurim strain TA104 and induce SOS response in E. coli PQ37. The mitochondrial and nuclear DNA damage were also detected by quantitative polymerase chain reaction technique in transformed human fibroblasts treated with ALA. All these data provide additional information on the genotoxic potential of ALA and reinforce the hypothesis that ALA may be involved in the induction of HCC in symptomatic AIP patients.
385

Stratégies thérapeutiques par conditionnement hypoxique : modalités pratiques et effets sur la santé cardio-respiratoire et métabolique / Therapeutic strategies by hypoxic conditioning : practical modalities and effects on cardiorespiratory and metabolic health

Chacaroun, Samarmar 29 June 2018 (has links)
L’hypoxie désigne une baisse de la biodisponibilité en oxygène au niveau tissulaire. La combinaison de l’hypoxie intermittente et de l’hypercapnie est identifiée dans le cadre de plusieurs maladies respiratoires comme un élément physiopathologique déterminant. Cependant, des travaux de recherche suggèrent qu’une exposition à l’hypoxie hypo- ou normocapnique à l’éveil peut améliorer la santé cardiovasculaire. La combinaison d’une exposition hypoxique et de l’entraînement à l’effort est utilisée par les athlètes pour améliorer la performance sportive aérobie. Des études pilotes récentes y compris chez le malade chronique indiquent que l’exposition à l’hypoxie modérée au repos ou à l’effort chez le patient est susceptible d’induire des gains significatifs en termes de santé cardiovasculaire, de composition corporelle et de statut métabolique.Nous nous sommes intéressés aux effets cardiorespiratoires et tissulaires de l’exposition hypoxique normobarique chez le sujet sain et chez la personne en surpoids ou obèse présentant un risque ou des anomalies cardio-métaboliques. Nous avons étudié l’efficacité de 2 types de conditionnement au repos consistant en une hypoxie continue ou une hypoxie intermittente et un entraînement à l’effort hypoxique par comparaison à la situation normoxique. Nous avons tout d’abord étudié les effets d’une exposition hypoxique à court terme au repos chez 14 sujets sains. Nous avons ensuite étudié les effets cardiorespiratoires, tissulaires, vasculaires et métaboliques d’un programme de conditionnement hypoxique normobarique à moyen terme au repos chez 35 patients en surpoids ou obèse. Nous avons de plus réalisé chez 24 sujets sains une étude préliminaire afin de vérifier la faisabilité et de caractériser les réponses cardio-respiratoires et l’oxygénation tissulaire au cours d’un exercice aigu à charge constante d’intensité modérée ou intermittent intense en hypoxie comparé à une condition placébo normoxique. La dernière étude a consisté à étudier les conséquences cardiorespiratoires, tissulaires, vasculaires et métaboliques d’un programme d’entraînement à l’effort en hypoxie par rapport au même programme en normoxie chez 23 patients en surpoids ou obèses.L’étude réalisée chez le sujet sain met en évidence l’intérêt à court terme d’un conditionnement hypoxique intermittent au repos sur des variables associées aux risques cardiovasculaires (diminution de la pression artérielle systolique en normoxie et augmentation de la variabilité sinusale) et une modulation de l’hypoxie tissulaire. Nous avons montré chez le sujet sain que l’hypoxie combiné à l’exercice aigu provoque une diminution de l’oxygénation musculaire similaire mais une diminution de l’oxygénation du cortex préfrontal plus importante par comparaison à un effort normoxique à même intensité relative. Ensuite, chez le sujet en surpoids ou obèse, nous avons montré que le conditionnement hypoxique passif chronique induit une diminution de la pression artérielle diastolique de repos en normoxie, une augmentation de la réponse ventilatoire hypoxique et une diminution de la variabilité cardiaque (après conditionnement par hypoxie intermittente seulement) et que le conditionnement hypoxique actif chronique améliore l’aptitude maximale aérobie par rapport à une situation placébo normoxique.Les résultats obtenus montrent la faisabilité de plusieurs conditionnements hypoxiques prometteurs au plan vasculaire y compris chez le sujet en surpoids ou obèse limité à l’exercice musculaire. Le conditionnement hypoxique actif montre également des bénéfices accrus sur l’aptitude aérobie. Ces protocoles de conditionnement doivent être affinés en vue d’optimiser leur efficacité en termes de perte de poids et d’amélioration du risque cardio-vasculaire et métabolique dans des populations présentant une obésité associée à une morbidité cardio-métabolique. Ils représentent également une piste thérapeutique innovante dans d’autres pathologies chroniques / Hypoxia refers to a decrease in the oxygen bioavailability at the tissue level. The combination of intermittent hypoxia and hypercapnia is identified in several respiratory diseases as a critical pathophysiological element. However, research suggests that exposure to hypo- or normocapnic hypoxia can improve cardiovascular health. The combination of hypoxic exposure and exercise training has been used by athletes to improve aerobic exercise performance. Recent pilot studies in patients with chronic diseases indicate that exposure to moderate hypoxia at rest or during exercise is likely to induce significant gains in cardiovascular health, body composition and metabolic status.We investigated the effects of normobaric hypoxic exposure on cardiorespiratory and tissue function in healthy subjects, overweight or obese subjects at risk or with cardio-metabolic abnormalities. We assessed the efficacy of 2 types of passive hypoxic conditioning consisting in sustained hypoxia or intermittent hypoxia and hypoxic exercise training in comparison with normoxic condition. First, we assessed the effects of short-term hypoxic exposure at rest in 14 healthy subjects. Then, we evaluated the cardiovascular and metabolic effects of a 8-week normobaric hypoxic conditioning program at rest (intermittent or sustained hypoxia) in 35 overweight or obese patients, compared to placebo normoxic exposure. Next, we conducted a preliminary study in 24 healthy subjects to assess the acute responses to submaximal constant-load and high intensity interval cycling exercise performed in normoxia and in hypoxia. The last study aimed to compare the effect of an 8-week exercise training program performed either in normoxia or hypoxia on maximal aerobic capacity in overweight or obese subjects.In the healthy subject, we emphasized the rapid benefits of intermittent hypoxic conditioning on cardiovascular function (lower baseline systolic blood pressure and increased heart rate variability) and the modulation of tissue deoxygenation in response to hypoxia. We have also shown in healthy subjects that acute exercise (combined with hypoxia causes a similar decrease in muscle oxygenation but a greater prefrontal cortex deoxygenation compared to normoxic condition. Then, in the overweight or obese subject, we have shown that chronic passive hypoxic conditioning induces a decrease in diastolic blood pressure at rest in normoxia, an increase in the hypoxic ventilatory response and a decrease in heart rate variability after intermittent hypoxic conditioning only. In addition, chronic active (exercise training) hypoxic conditioning improves the maximal aerobic capacity compared to placebo normoxic training.Our results show the feasibility of several hypoxic conditioning strategies and their interesting effects on the vascular function in overweight/obese subjects presenting exercise limitations impeding exercise reconditioning. In addition, active hypoxic conditioning showed a greater effect on physical fitness than normoxic exercise training. These hypoxic conditioning strategies must be further optimized to improve their efficacy regarding weight loss and cardiometabolic morbidity in obese. They also represent promising therapeutic opportunities for other chronic diseases
386

Commande intermittente de la machine à réluctance variable à double saillance / Intermittent control of the switched reluctance machine

Nguyen, Duy-Minh 08 July 2019 (has links)
La commande intermittente a pour but principal d'augmenter le rendement de l'ensemble machine-convertisseur par une réduction des pertes. Dans le but de maintenir le couple moyen de la machine requis par la charge, cette commande augmente le couple de référence et éteint quelques phases pendant chaque période électrique ou chaque période mécanique. Par ce fait, elle réduit les pertes du convertisseur et les pertes ferromagnétiques de la machine. Elle dispose également d'une liberté de sélection des phases activées qui influence des fréquences générées du courant, de la force radiale et du couple. Par conséquent, cette stratégie de la commande intermittente, qui est appelée le glissement, peut éviter l'excitation de fréquences naturelles du stator, ou bien celles de la chaine cinématique. Elle a pour but de réduire les effets négatifs de la commande intermittente vis-à-vis de comportements vibratoire du stator et pulsatoire de la chaine cinématique qui sont respectivement à l'origine du bruit acoustique et des à-coups mécaniques. En fin, la commande intermittente est validée sur des cycles de conduite et peut économiser jusqu’à 5,17 % de l’énergie électrique consommée. / The intermittent control aims to increase the efficiency of the machine-converter system by reducing the losses. In the purpose to maintain the average torque of the machine required by the load, this control increases the reference torque and turns off some phases during each electrical period or each mechanical period. By this fact, it reduces the converter losses and the ferromagnetic losses of the machine. It also has a freedom in the selection of the activated phases which influences the generated frequencies of the current, the radial force and the torque. Therefore, this strategy of the intermittent control, which is called sliding strategy, can avoid the excitation of the natural frequencies of the stator, or those of the drivetrain. It aims to reduce the negative effects of the intermittent control vis-à-vis the vibration of the stator and the pulsation of the drivetrain which are respectively at the origins of acoustic noise and mechanical jerks. Finally, the intermittent control is validated on driving cycles and can save up to 5.17 % of the consumed electrical energy.
387

Phénoménologie de particules actives à états internes finis et discrets : une étude individuelle et collective / Phenomenology of active particles with finite and discrete internal states : an individual and collective study

Gómez Nava, Luis Alberto 05 November 2018 (has links)
Dans cette thèse, nous présentons un cadre théorique pour étudier les systèmes de particules actives fonctionnant avec une quantité discrète d'états internes qui contrôlent le comportement externe de ces objets. Les concepts théoriques développés dans cette thèse sont introduits afin de comprendre un grand nombre de systèmes biologiques multi-agents dont les individus présentent différents types de comportements se succédant au cours du temps. Par construction, le modèle théorique suppose que l'observateur extérieur a accès uniquement au comportement visible des individus, et non pas à leurs états internes. C'est seulement après une étude détaillée de la dynamique comportementale que l'existence de ces états internes devient évidente. Cette analyse est cruciale pour pouvoir associer les comportements observés expérimentalement avec un ou plusieurs états internes du modèle. Cette association entre les états et les comportements doit être faite selon les observations et la phénoménologie du système biologique faisant l'objet de l'étude. Les scénarios qui peuvent être observés en utilisant notre modèle théorique sont déterminés par la conception du mécanisme interne des individus (nombre d'états internes, taux de transition, etc…) et seront de nature markovienne par construction. Tous les travaux expérimentaux et théoriques contenus dans cette thèse démontrent que notre modèle est approprié pour décrire des systèmes réels montrant des comportements intermittents individuels ou collectifs. Ce nouveau cadre théorique pour des particules actives avec états internes, introduit ici, est encore en développement et nous sommes convaincus qu'il peut potentiellement ouvrir de nouvelles branches de recherche à l'interface entre la physique, la biologie et les mathématiques. / In this thesis we introduce a theoretical framework to understand collections of active particles that operate with a finite number of discrete internal states that control the external behavior of these entities. The theoretical concepts developed in this thesis are conceived to understand the large number of existing multiagent biological systems where the individuals display distinct behavioral phases that alternate with each other. By construction, the premise of our theoretical model is that an external observer has access only to the external behavior of the individuals, but not to their internal state. It is only after careful examination of the behavioral dynamics that the existence of these internal states becomes evident. This analysis is key to be able to associate the experimentally observed behaviors of individuals with one or many internal states of the model. This association between states and behaviors should be done accordingly to the observations and the phenomenology displayed by the biological system that is being the subject of study. The possible scenarios that can be observed using our theoretical model are determined by the design of the internal mechanism of the individuals (number of internal states, transition rates, etc...) and will be of markovian nature by construction. All the experimental and theoretical work contained in this thesis is evidence that our model is suitable to be used to describe real-life systems showing individual or collective intermittent behaviors. This here-introduced new framework of active particles with internal states is still in development and we are convinced that it can potentially open new branches of research at the interface between physics, biology and mathematics.
388

Hochauflösender mikromechanischer Sensor zur Erfassung von Oberflächenprofilen

Kotarsky, Ulf 26 November 2004 (has links)
In der vorliegenden Arbeit wird die Entwicklung von ausschließlich elektrostatisch arbeitenden Sensor-Aktor-Arrays zur Oberflächenprofilbestimmung an Mikroteilen beschrieben. Ein wesentliches Merkmal der Strukturen ist ihr großer Eigenzustellbereich von bis zu 20 Mikrometer. Die Auswertung atomarer Kräfte ermöglicht Wegauflösungen im Nanometerbereich. Auf Grund der geringen Abmessungen durch die mikromechanische Fertigung des Sensorelements und der integrierten Sensor-Aktorfunktion sind Anordnungen als Zeilenarray möglich. Die Entwicklung richtet sich auf Strukturen, welche in klassischer Oberflächentechnologie gefertigt werden können. Durchgeführte experimentelle Tests wurden mit Sensoren in Silizium-bulk-Mikromechanik (SCREAM) realisiert. Der Schwerpunkt der Arbeit behandelt die Charakterisierung der Sensorelemente und damit verbundene Layoutverbesserungen, wie das Einbringen von Feldstoppern und die Nutzbarkeit des Sensors zur Profilbestimmung von Oberflächen unter Beachtung industrieller Anforderungen. Vorteile des Einsatzes eines solchen Sensor-Aktor-Arrays liegen in der Miniaturisierung und dem vergleichsweise großen Eigenzustellbereich jedes einzelnen Sensors. Dadurch ist es möglich, technische Oberflächen, welche im Eigenzustellbereich des Sensorarrays liegen, ohne das Nachregeln einer übergeordneten Positioniereinheit im Profil zu bestimmen. Es wird gezeigt, wie die angewandte kapazitive Wirkungsweise des Sensors mit den sehr kleinen Nutzkapazitäten im Beisein von großen Parasitärkapazitäten zur Signalauswertung genutzt werden kann.
389

Vätgasens roll i det regionala energisystemet : Tekno-ekonomiska förutsättningar för Power-to-Power / Hydrogen in a Regional Energy System Context : Techno-economic prerequisites for Power-to-Power

Mattsson, Helen, Lindberg, Jonatan January 2020 (has links)
Alltmer intermittent elkraft byggs idag i Sverige för att öka andelen förnybar el i energisystemet. Detta leder till mer ojämn elproduktion, vilket skapar problem i form av mer volatila och oförutsägbara elpriser. Ett sätt att dämpa effekten av den ökande intermittenta kraften är att använda förnybar vätgasproduktion som lastutjämning. På detta sätt kan vätgasen potentiellt bli en viktig del i den fossilfria energimixen. Att använda vätgas som energilager i en Power-to-Power-applikation (P2P) möjliggör även utnyttjandet av prisarbitrage på elmarknaden. Ett ökat klimatfokus har återuppväckt intresset för hur vätgasproduktion kan göras lönsamt. Några tecken på att satsningar sker är att flera länder satsar stora pengar på vätgastekniker och infrastruktur, där flertalet samarbeten över nationella gränser har etablerats.Denna studie syftar till att undersöka de tekno-ekonomiska förutsättningarna för produktion av förnybar vätgas där lönsamheten av arbitragehandel på elmarknaden Elspot bedöms. Detta innefattar en gedigen granskning av kommersiella tekniker lämpade för Linköpings energisystem, däribland elektrolys, ångreformering och bränslecell. Tre fall konstruerades med olika uppsättningar av ingående komponenter. Sedan utfördes en driftoptimering som tog fram övre och undre prisgränser för produktion respektive konvertering av vätgas mot spotpriset. Optimeringsverktyget Problemlösaren i Excel användes för att få fram dessa gränser. Visual Basic (VBA) användes sedan för att genomföra en lagersimulering som visualiserar lagersaldot för alla årets timmar. För att få fram kostnaden för varje kilogram producerad vätgas användes nuvärdesberäkningen Levelised Cost of Energy (LCOE), vilket även underlättade jämförelsen av de tre fallen. Vilka effekter i form av växthusgasutsläpp de olika anläggningarna medför utvärderades också genom beräkningssättet konsekvensanalys. Där jämfördes effekten i form av nettoutsläpp i koldioxidekvivalenter för integrering av respektive anläggning. Resultaten visar på att det finns kommersiella tekniker som kan integreras med det befintliga energisystemet på ett resurseffektivt sätt, däremot är de ekonomiska förutsättningarna inte lika bra och P2P-lösningarna är idag långt ifrån lönsamma. Anledningen tros vara en kombination av otillräckliga elprisfluktuationer samt låg total systemverkningsgrad (som högst 14%) för samtliga konstruerade fall. De årliga intäkterna från elförsäljningen motsvarar cirka 1 procent av de årliga kostnaderna för anläggningen, och LCOE landade på cirka 1500 kronor. Resultaten från investeringskalkyleringen visar på att en högre utnyttjandegrad leder till en lägre LCOE. Lagersimuleringen visar på att säsongslagring krävs för denna typ av anläggning då fluktuationerna inte är tillräcklig stora på en daglig, veckovis eller månatlig basis. Känslighetsanalys på LCOE och driftoptimeringen visar inte heller på lönsamhetsmöjligheter i P2P-fallen även vid gynnsamma justeringar på parametrarna investeringskostnad, elpris och verkningsgrad. Ur ett klimatperspektiv visar samtliga fall, med ett undantag, på en minskade växthusgasutsläpp i regionen.  Slutsatsen som dras av resultaten från fallstudien är att, trots goda tekniska förutsättningar och positiv inverkan på lokala växthusgasutsläpp, kan en P2P-applikation med vätgaslagring inte göras lönsam i en svensk kontext inom en nära framtid. Däremot visar ett Power-to-Gas-fall potential för lönsamhet, då dess investeringskostnad är mindre samt att systemverkningsgraden är högre. / More and more intermittent electric power is being built in Sweden today to increase the share of renewable electricity in the energy system. This leads to more uneven electricity generation, which creates problems in terms of more volatile and unpredictable electricity prices. One way to dampen the effect of the increasing intermittent power is to use renewable hydrogen production as load shedding. In this way, the hydrogen gas can potentially become an important part of the fossil-free energy mix. Using hydrogen as energy storage in a Power-to-Power application (P2P) also enables the use of price arbitrage in the electricity market. An increased climate focus has rekindled interest in how hydrogen production can be made profitable. Some signs that investments are taking place are that several countries are investing big money on hydrogen technologies and infrastructure, and collaborations across national borders have been established. This study aims to investigate the techno-economic prerequisites for renewable hydrogen production where the profitability of arbitrage on the Elspot market is explored. This comprises a thorough investigation of commercial technologies suited for Linköping’s energy system. Three cases where constructed with different component constellations. Then the operational strategy was optimised which generated a lower and upper price limit for production and conversion of hydrogen with input price data from Elspot. The optimisation tool in Excel was used in order to obtain these price limits. Visual Basic (VBA) was then used for storage simulation in order to get a perception of the storage development through all the hours of the year. The cost of every kilogram of hydrogen produced was then calculated through Levelized Cost of Energy (LCOE), which made the comparison of the three cases easier. The resulting greenhouse gas emissions when integrating the facilities in each case were also evaluated with a so-called impact analysis. The effect was compared in net emissions in carbon dioxide equivalents for an integration of each facility.     The results show that there are commercial technologies that can be integrated with the existing energy system in a resource efficient manner, whereas the economic prerequisites are not as good, where today’s Power-to-Power (P2P) solutions are not profitable. The reason seems to be the combination of insufficient spot price fluctuations and a low system efficiency (14% at best) for each case. The annual revenues correspond to 1 percent of the annual costs and that LCOE lands at about 1500 SEK. A higher utilization percentage of the plant shows a lower LCOE in the investment calculation. The storage simulation indicates that a seasonal storage is needed for this type of facility because of that the spot price fluctuations are not big enough on a daily, weekly or monthly basis. The sensitivity analysis made on the investment calculation and operational strategy also shows that there is no profitability in the P2P cases where parameters regarding investment cost, efficiency and electricity price were set optimistically. The Power-to-Gas case on the other hand shows potential for profitability, all because of lower total investment costs and higher efficiency. All cases except the case with steam methane reforming shows reductions in greenhouse gas emissions when integrated in the regional energy system.   The conclusion that can be drawn from the results in the case study is that, in spite of good technological prerequisites and a positive effect on local greenhouse gas emissions, a P2P-application with hydrogen storage cannot be made profitable in a Swedish context in the near future. However, a Power-to-Gas case shows potential for profitability because of its lesser investment cost and that the system efficiency is higher.
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Analysis of the Resilience of Intermittent Water Supply Systems and the Disruption-Dynamics of Stakeholders

Saad I Aljadhai (9029648) 27 June 2020 (has links)
<p>Millions of households around the world rely on intermittent water supply systems (IWS), where piped water supply is limited to specific hours during the day or on specific days during the week. Households relying on IWS systems, as their primary water source, often adapt to supply intermittency by installing in-house water storage and/or supplying water from non-piped sources (for instance, in the form of water tanker trucks). The piped water distribution network (WDN) in IWS systems is subject to short-term disruptions that cause dynamic behavior and interactions of the system’s stakeholders, including households, vendors of non-piped water, and the water utility. During disruptions of the WDN, households make decisions about obtaining water from different non-piped sources at different prices and wait times. These decisions, made by a large number of households, have an impact on the dynamics (in particular, the prices and availability) of the non-piped water market, which may in turn affect each household decision. Prior studies on the literature of the analysis of IWS systems focused on analyzing each of the components (namely the WDN, households, vendors of non-pied water, and the water utility) of the IWS in isolation, assuming static behavior of the other components.</p><p>The overreaching objective of this dissertation is to bridge the gap in knowledge and practice in analyzing the short-term dynamics within each component of the IWS system (focusing on the WDN and the households) and the interactions among all components of the IWS system when responding to physical disruptions of the WDN. First, a new framework for quantifying and analyzing the resilience of intermittent WDNs is presented. The framework incorporates the aspects of intermittent supply (including household storage and supply scheduling) into a hydraulic model that examines the network’s hydraulic performance and its topology to assess three resilience capacities: absorptive, adaptive, and restorative, against various types of physical disruptive events. The evaluation of the model, using the IWS network of a case study city in the Middle East, shows that household storage capacities, timing and length of the disruption, supply inequity, and the supply scheduling are significant factors in determining the resilience of the WDN, and the interactions of these variables result in different combinations of direct and post effects on households. The framework was also used to evaluate the impact of temporary modifications of the supply schedule on the network’s resilience. The results show that this short-term utility adaptive measure can significantly improve the resilience of the network. The proposed framework can assist utilities in the operation of the intermittent WDN under normal conditions and in the evaluation of the impact of different short- and long-term resilience enhancement strategies.</p><p>Next, based on empirical data from a survey of households in a city in the Middle East, the households’ decision-making in response to disruptions of the WDN was evaluated using econometric methods. A set of Binary Probit models were developed to model the decision of households regarding their risk attitudes toward running out of water (represented by the timing of their response actions), their willingness to pay for faster delivery of non-piped water, and their willingness to wait in-line to obtain water from a non-piped source. The results show how variables related to household characteristics, wealth, age and occupation of the household’s manager, knowledge of household manager about their households’ water situation, and prior experience with disruptions affect the households’ decisions when the piped-network is disrupted. The outputs of the econometric models can assist the city’s water managers in understanding the behavior of households that affect the demand and prices of different non-piped water sources.</p><p>The final component in this research integrates the two previous components into an Agent-Based Model (ABM) to evaluate the dynamics of the stakeholders’ interactions in response to disruptions of the WDN and to evaluate the impact of these interactions on the resilience of the whole system. The ABM examines the interactions between households and vendors of water tankers under utility’s policies that regulate the water tanker market while integrating variables that describe the response of the WDN to the disruption. The demonstration of the model using a representative subset of the IWS system in the case study city shows dynamic behavior patterns in: (a) the dynamics of households, and (b) the performance of the non-piped water market under different deterministic and stochastic scenarios of disruptions of the WDN.</p><p>The results of this research address many IWS systems in the Middle East and around the world that are characterized by household storage, as well as households’ dependency on the piped network as the main water supply. The models developed in this dissertation are expandable to adopt various systems’ configurations in terms of types and capacities of household storage, types and attributes of non-piped water sources, and attributes and preferences of households. The results of this doctoral research can assist water managers in cities in understanding the behavior of their IWS system (including the WDN and the system’s stakeholders), evaluating long-term resilience enhancement policies, and planning for short-term response to disruptions of the WDN.</p>

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