The master´s thesis focuses on problematics associated with data backup and storages. It deals with the realistic data backup issue at a real municipal office. Part of the work is a thorough analysis of the current state and suggestions for improvement.

Climate change impacts on snow storages and spring runoff in the Vydra river basin Abstract As a result of increasing air temperature, the fraction of precipitation falling as snow decreases. This affects snow cover indicators including snow cover duration, snow cover extent and the amount of water that accumulates in snow cover during winter. These changes further propagate through local runoff process and alter winter and spring runoff. The impacts of air temperature warming of 1℃, 2℃ and 3℃ on the above-mentioned indicators were simulated using a conceptual catchment runoff model HBV-light. Multi- criteria calibration, based on functions describing the goodness of fit of simulated runoff and snow water equivalent (SWE) values was performed. The temperature change scenarios were derived using the delta-change method from reference dataset 1980-2014. The indicator changes were evaluated for 5 elevation belts of the catchment as well as for the catchment as a whole, so that the observed alternations of snow cover indicators could be related to the modelled alternations of runoff. The changes in snow cover characteristics based on these simulations include a decrease of snowfall fraction, shortened snow season, decrease in average and maximal SWE values, and the shift of the average day of year of SWEmax to...

Aujourd'hui et à l'avenir, l'augmentation des prix du carburant, la déréglementation et les contraintes de l'environnement donnent plus de possibilités pour l'utilisation des sources d'énergie renouvelables (SER) dans les réseaux électriques. Un concept de microgrid est nécessaire afin d'intégrer les sources d'énergie renouvelables dans le réseau électrique. Ce microgrid comprend un réseau de basse tension (BT) avec les ressources d'énergie distribuées (DER) ainsi que les moyens de stockage et des charges flexibles. L'intégration des énergies renouvelables dans un microgrid peut causer des enjeux et des impacts sur le fonctionnement du microgrid. C'est pourquoi dans cette thèse, un dimensionnement optimal et les stratégies de fonctionnement en sécurité, fiabilité et efficacité d'un microgrid comportant des productions photovoltaïques (PV), des systèmes de stockage d'énergie de la batterie (BESS) et / ou les diesels sont proposés. Tout d'abord, la technique d'optimisation itérative est utilisée pour trouver le dimensionnement optimal d'un microgrid. Deuxièmement, les stratégies de contrôle de tension et de fréquence pour un microgrid en mode îloté en utilisant les statismes sont étudiées. De plus, nous proposons les stratégies intelligentes de contrôle de tension et de la fréquence à l'aide de la logique floue. De cette manière, la fréquence est exprimée non seulement en fonction de la puissance active, mais aussi de l'état de charge de BESS et des régimes de fonctionnement de microgrid. Et enfin, une méthode pour optimiser la gestion de l'énergie dans l'exploitation d'un microgrid est proposée dans cette thèse. La programmation dynamique est utilisée pour trouver le minimum du coût du carburant compte tenu des émissions par la planification des ressources énergétiques distribuées (de DER) dans un microgrid en mode îloté ainsi que pour minimiser le coût d'énergie et les puissances d'échange avec le réseau en mode connecté. Les résultats de simulation obtenus montrent la précision et l'efficacité des solutions proposées. / Today and in the future, the increase of fuel price, deregulation and environment constraints give more opportunities for the usage of the renewable energy sources (RES) in power systems. A microgrid concept is needed in order to integrate the renewable sources in the electrical grid. It comprises low voltage (LV) system with distributed energy resources (DERs) together with storage devices and flexible loads. The integration of RES into a microgrid can cause challenges and impacts on microgrid operation. Thus, in this thesis, an optimal sizing and security, reliability and economic efficiency operation strategies of a microgrid including photovoltaic productions (PV), battery energy storage systems (BESS) and/or diesels is proposed. Firstly, the iterative optimization technique is used to find the optimal sizing of a microgrid. Secondly, the voltage and frequency control strategies for an island microgrid by using droop control methods are studied. Furthermore, we propose intelligent voltage and frequency control strategies by using fuzzy logic. By this way, the frequency is expressed not only as the function of active power but also the state of charge of BESS and the operation states of microgrid. And finally, a method to optimize the energy management in operation of a microgrid is proposed in this thesis. Dynamic programming is used to find the minimum the cost of fuel considering the emissions by scheduling of distributed energy resources (DERs) in an island microgrid as well as to minimize the cash flows and the exchanged power with the main grid in a grid-connected mode. The simulation results obtained show the accuracy and efficiency of the proposed solutions.

Today agriculture sector has a big contribution to the development of economy for many countries. Irrigation is a method which supplies amount of water required in proper time to the cropped land and contributes to the increases of agriculture productivity. Using diesel pump to deliver water to the place of use causes problems both in terms of profitability and environmental perspectives. Higher price of diesel increases operation costs of diesel water pumping system thereby reducing the incomes. In addition the use of diesel pump emits a huge amount of CO2 emissions which cause global warming. A possible solution to those problems is to use solar energy, a source of energy which is environmental friend and available for free. The main target of this thesis is to design and optimize a cost effective PVWPs considering three alternatives with tank storage, battery storage and a system without storages medium. The two areas in Eastern province of Rwanda were taken as case study to grow coffee and cassava with five hectares each. To run simulations, different tools have been used. Those includes CROPWAT to determine water requirements for two crops; MS Excel to design a PVWPs directly connected to irrigation system, make economic analysis, evaluate CO2 emissions and calculate other parameters. Furthermore in PVsyst software the design and simulation for PVWPs with storages medium has been carried out.  Results showed that using PVWPs directly connected to irrigation system is the most profitable way when compared to the rest two alternatives.  They also showed that systems designed to irrigate coffee becomes the most profitable due to huge amount of electricity surplus and higher price per kilogram of coffee. Finally fully replacement of DWPs results in annual reduction of CO2 emissions by 6.6 tonnes. Keywords: Photovoltaic system, storages medium, pumping system, economic analysis, reduction in CO2 emissions.

Le travail présenté ici a pour objectifs d’étudier et d’optimiser les performances énergétiques d’un chauffe-eau thermodynamique couplé à un stockage par chaleur sensible. La ressource utilisée consiste en la récupération de chaleur sur l’air extrait d’un logement de type collectif. L’enjeu est de caractériser les conditions dans lesquelles le système est capable d’assurer les besoins avec des performances requises lorsque les conditions aux limites sont très fluctuantes. Sur le plan fonctionnel, le système doit être le plus simple possible du point de vue de sa configuration hydraulique et de sa stratégie de régulation.Pour cette étude, nous avons développé un modèle physico-corrélatif sur TRNSYS pour simuler et analyser les différents scenarios et les couplages thermohydrauliques entre les composants du système. En parallèle de cette démarche de modélisation, nous avons conçu et mis en œuvre un dispositif expérimental à l’échelle 1 à des fins de validation du modèle sur une large plage de conditions opératoires.L’analyse des résultats, notamment sur la nature des écoulements au sein du ballon de stockage, a mis en évidence l’influence majeure d’un certain nombre de paramètres sur les performances du système. En particulier, la robustesse des performances face à des fluctuations importantes des conditions aux limites peut être assurée grâce à une stratégie de régulation adaptée.Cette étude a finalement conduit à proposer un modèle réduit pour le dimensionnement du système qui prend en compte les paramètres le plus pertinents pour la stratégie de régulation. / The work presented here aims to study and optimize the energy efficiency of a heat pump water heater coupled with a sensible heat storage. The resource used consists of heat recovery from exhaust air of a collective type of housing. The challenge is to characterize the conditions in which the system is capable of ensuring the needs with performance required when the boundary conditions are very volatile. Functionally, the system should be as simple as possible from the viewpoint of its hydraulic configuration and its control strategy.For this study, we developed a TRNSYS numerical model to simulate and analyze different scenarios and thermal hydraulic couplings between the system components. In parallel with this modeling approach, we designed and implemented an experimental set up with realistic scale to validate the model over a wide range of operating conditions.The analysis of the results, including the nature of flows within the storage tank, highlighted the major influence on a number of parameters on the system performance. In particular, the robust performance in the face of significant fluctuations of the boundary conditions can be ensured through appropriate control strategy.This study eventually led to propose a model for the design of the system that takes into account the most relevant parameters for the control strategy.

The aim of master thesis was to create a program for the quantitative analysis of data backup schemes and with its help to identify and analyze the properties of commonly used schemes for different loads. Based on the obtained results, compile a set of principles for choosing the optimal data backup scheme. The program was created by Matlab. It can be used to find out parameters for individual backup schemes: Parameters C (total backup volume) and E (medium volume of recovery backups), backups size of individual days, workload of individual storages, cost of storages and cost of overall backup scheme, size the total amount of data written per storage per time slot. At the end of the thesis is defined a scheme for choosing the optimal backup scheme.

This report travels through multiple disciplines to seek innovative and sustainable energy solutions for wastewater treatment plants. The first subject is a report about increased global temperatures and an over-exploitation of natural resources that threatens ecosystems worldwide. The situation is urgent where the current trend is a 2°C increase of global temperatures already in 2040. Furthermore, the energy-land nexus becomes increasingly apparent where the world is going from a dependence on easily accessible fossil resources to renewables limited by land allocation. A direction of the required transition is suggested where all actors of the society must contribute to quickly construct a new carbon-neutral resource and energy system. Wastewater treatment is as required today as it is in the future, but it may move towards a more emphasized role where resource management and energy recovery will be increasingly important. This report is a master’s thesis in energy engineering with an ambition to provide some clues, with a focus on energy, to how wastewater treatment plants can be successfully integrated within the future society. A background check is conducted in the cross section between science, society, politics and wastewater treatment. Above this, a layer of technological insights is applied, from where accessible energy pathways can be identified and evaluated. A not so distant step for wastewater treatment plants would be to absorb surplus renewable electricity and store it in chemical storage mediums, since biogas is already commonly produced and many times also refined to vehicle fuel. Such extra steps could be excellent ways of improving the integration of wastewater treatment plants into the society. New and innovative electric grid-connected energy storage technologies are required when large synchronous electric generators are being replaced by ‘smaller’ wind turbines and solar cells which are intermittent (variable) by nature. A transition of the society requires energy storages, balancing of electric grids, waste-resource utilization, energy efficiency measures etcetera… This interdisciplinary approach aims to identify relevant energy technologies for wastewater treatment plants that could represent decisive steps towards sustainability.