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Context. In newer database solutions designed for large-scale, cloud-based services, database performance is of particular concern as these services face scalability challenges due to I/O bottlenecks. These issues can be alleviated through various data model optimizations that reduce I/O loads. Object serialization is one such approach. Objectives. This study investigates the performance of serialization using the Apache Avro library in the Cassandra database. Two different serialized data models are compared with a traditional relational database model. Methods. This study uses an experimental approach that compares read and write latency using Twitter data in JSON format. Results. Avro serialization is found to improve performance. However, the extent of the performance benefit is found to be highly dependent on the serialization granularity defined by the data model. Conclusions. The study concludes that developers seeking to improve database throughput in Cassandra through serialization should prioritize data model optimization as serialization by itself will not outperform relational modelling in all use cases. The study also recommends that further work is done to investigate additional use cases, as there are potential performance issues with serialization that are not covered in this study.

For the grid to be stable, the supply of power must equal the demands of the consumer at every moment during the day. The unpredictable intermittent nature of wind results in inconsistent power generation. Energy storage technologies coupled with a wind farm can not only provide power during fluctuations but also maintain a stable and reliable grid. The objective of the thesis is to perform a comprehensive analysis of different types of energy storage technologies that can be coupled with a wind farm. The analysis is performed on the basis of multiple characteristics which affect their viability. We identified key characteristics for a range of storage technologies, including lead-acid, sodium-sulphur, nickel cadmium, lithium-ion, superconducting magnetic energy storage, electrochemical capacitors, flywheels, flow batteries, pumped hydro and compressed air energy storage systems. We performed a comparison study to analyze trade-offs and assessed potential improvement areas that will make them more competitive in the electric power industry. We suggested viable energy storage systems that could be better and suitable for different applications for an electric grid integrated with a wind farm.

This master thesis deals with the untraditional application domain of logistics in libraries which is demonstrated with the help of concrete examples of libraries from the Czech Republic, Finland and Australia. The main goal of the thesis is to compare the library logistics of the City Library of Hradec Králové, the Municipal Library of Prague and the Turku City Library with the focus on the equipment and logistics technologies used, especially storage technologies and technologies for automatic identification. The most sophisticated technologies used in libraries are demonstrated using the example of the Australian Macquarie University Library and the project Eye over Prague. A classification of libraries according to their size in terms of the number of library items and the number of loans is created in the thesis and the appropriate library logistics solutions are then assigned to the particular classification groups.

The energy system is undergoing a transformation on a never before witnessed scale. The changes are driven by global market forces and technological advancements, improving on a seemingly exponential scale. This in turn has led to the price of both renewables and the accompanying technology decrease over time, making the transition into renewables more economically viable. The drawback of variable renewable energy is that it is variable and dependent on the surrounding environment. Therefore, storing the energy during hours of production, to be used at a later stage when energy demand is higher is becoming ever more important and an attractive option. The purpose of this degree project is to, from a set of performance indicators, evaluate three different energy storage technologies and their respective impact on a distribution grid. The examined storage technologies are: Batteries, Capacitators and a H2 Fuel cell. A literature study was performed in order to find out how grid performance is evaluated, and how the different storage technologies operate. The obtained literature comes from scientific reports, and papers, found by utilizing Mälardalens University library-database. A model representing a Swedish grid with a connection point to the distribution side was created. The model is taken from previous credited work, and customized to fit the operational parameters of a Swedish grid. It was decided that the key indicators for evaluating the state of a grid was to look at the: voltage- and frequency variations, load factor, capacity factor and the overall system efficiency. The simulation is a discrete time simulation that utilizes parameters indicative of one full day of data. The results showed that, from a technological standpoint, the supercapacitor performed better in more categories than the Li-ion battery and H2 fuel cell. However, the Li-ion battery reduced the peaks of the frequency measurements which is a key metric when deciding on grid health. Also, there is the added benefit of the battery and fuel cell of having a longer operational time before the state of charge is depleted. This increases the flexibility of the technology and could therefore be more beneficial in other applications where power supply is more scarce.

The operation of electric grids depends on the balance between the electric generation and the demand. In France, the Transmission System Operator, RTE, is responsible for the stability and the security of the grid. Today, the electric generation follows the variations of the demand. However, environmental concerns prompt to develop new strategies and policies for Energy Transition. The development of Smart Grids, the uncertain future of nuclear generation, the massive integration of renewable sources are the focus of those. Furthermore, renewable energies generation is intermittent and can not be controlled. The current strategy for the balance between generation and demand is challenged. The electric grid has to be readjusted by adding more electric flexibility to ensure its stability. The electric flexibility is usually associated to storage technologies as batteries or pumping stations. A state of art review is used to define this notion and to evaluate the technological and economic maturity of different electric flexibility vectors. The following report is based on a selection of prospective scenarios, development plans already launched in France, proposing a significant share of renewable energies in a future energy mix and current French energy data. Two studies were carried out : one at a regional level, for Bretagne and one at national level for France. An evaluation at 2050 is carried out to determine the load factors of intermittent energies, consumption and residual demand in Bretagne. On the basis of these prospective estimates, a need for electric flexibility can be determined for the Bretagne region. This first study highlights an issue related to future needs for electric flexibility. However, since the balance between production and consumption is achieved at a national level, a second study on France is necessary. The French need for electric flexibility is then estimated through a linear optimization that evaluates the energy production required to achieve a generation/consumption balance taking into account energy sources merit order. / Det franska elnätets funktion beror på balansen mellan elproduktionen och efterfrågan. Transmissionssystemoperatören, RTE, ansvarar för nätets stabilitet och säkerhet. Idag följer den elektriska generationen variationerna i efterfrågan. Miljömässiga frågor är emellertid snabba för att utveckla nya strategier och strategier för energiövergång. Utvecklingen av Smart Grids, den osäkra framtiden för kärnkraftsproduktion, den massiva integrationen av förnybara källor är deras fokus. Vidare är generering av förnybara energikällor intermittent och kan inte kontrolleras. Den nuvarande strategin för balans mellan produktion och efterfrågan utmanas. Elnätet måste justeras genom att lägga till mer elektrisk flexibilitet för att säkerställa stabiliteten. Den elektriska flexibiliteten är vanligtvis förknippad med lagringsteknik som batterier eller pumpstationer. En allmänt erkända tekniska används för att definiera denna uppfattning och att utvärdera den tekniska och ekonomiska mognaden hos olika elektriska flexibilitetsvektorer. Följande undersökningar grundar sig på ett urval av framtida scenarier, utvecklingsplaner som redan lanserats i Frankrike, och föreslår en betydande andel förnybara energikällor i en framtida energimix och nuvarande franska energidata. Två studier utfördes på olika perimetrar: på Bretagne-regionen och i Frankrike. En utvärdering vid 2050 utförs för att bestämma belastningsfaktorerna för intermittent energi, förbrukning och återstående efterfrågan i Bretagne. På grundval av dessa framtida uppskattningar kan ett behov av elektrisk flexibilitet bestämmas för Bretagne-regionen. Denna första studie lyfter fram ett problem som rör framtida behov av elektrisk flexibilitet. Men eftersom balansen mellan produktion och konsumtion uppnås på nationell nivå krävs en andra studie om Frankrike. Det franska behovet av elektrisk flexibilitet uppskattas sedan genom en linjär optimering som utvärderar den energiproduktion som krävs för att uppnå en generation / konsumtionsbalans med hänsyn tagen till energikällans meriteringsordning. / Le fonctionnement du réseau électrique français repose sur l’équilibre entre la production et la consommation d’électricité. Le gestionnaire du réseau de transport, RTE, est responsable de la stabilité et de la sécurité du réseau. Aujourd’hui, la production électrique s’adapte aux variations de la consommation. Cependant, des préoccupations environnementales incitent à la mise en place de nouvelles stratégies et politiques pour la transition énergétique. Le développement d’un réseau intelligent, l’avenir incertain du nucléaire et l’intégration massive d’énergies renouvelables sont au centre de celles-ci. De plus, la production électrique des énergies renouvelables s’avère intermittente et fatale. La stratégie actuelle du maintien de l’équilibre production/consommation est remise en question. Le système électrique doit être repensé en y intégrant plus de flexibilité électrique pour en garantir la stabilité. La flexibilité électrique est usuellement associée aux technologies de stockage comme les batteries électrochimiques et les STEP hydrauliques. Un état de l’art permet de définir précisément cette notion et d’évaluer la maturité technologique et économique en France de ces différents vecteurs de flexibilité électrique. L’objet des recherches suivantes est basé sur une sélection de scénarios prospectifs, de plans de développement d’ores et déjà lancés en France, proposant une part importante d’énergies renouvelables dans un futur mix énergétique et des données énergétiques actuelles françaises. Deux études ont été menées sur différents périmètres : sur la région Bretagne et sur la France entière. Une évaluation à 2050 est effectuée pour déterminer facteurs de charge des énergies intermittentes, consommation et demande résiduelle en Bretagne. A partir de ces estimations prospectives, un besoin en flexibilité peut être déterminé sur le périmètre de la Bretagne. Cette première étude permet de mettre en exergue une problématique liée aux futurs besoins de flexibilité électrique. Cependant, l’équilibre entre production et consommation étant réalisé à un niveau national, une seconde étude sur le périmètre français est nécessaire. Le besoin français en flexibilité est alors estimé par le biais d’une optimisation linéaire qui évalue la production énergétique nécessaire pour obtenir un équilibre production/consommation en tenant compte de la préséance économique.