1,720,963 research outputs found
Metodi e strumenti per la caratterizzazione e lo sviluppo delle batterie al litio - Methods and Tools for Characterizaton and Development of Lithium Batteries
Get PDFNegli ultimi anni, il mercato per le batterie al litio sta crescendo in maniera esponenziale. Anche le prestazioni delle batterie stanno crescendo grazie ai continui miglioramenti tecnologici ma le richieste di mercato crescono ancor più velocemente.
Le batterie basate sulla tecnologia al litio hanno bisogno di un sistema embedded, il Battery Management System, che monitora lo stato delle varie celle e controlla l’intera batteria. Per ottimizzare e velocizzare sviluppo di questi sistemi embedded è fondamentale avere un ambiente di simulazione adatto e dei modelli elettro-termici delle celle che devono essere state prima accuratamente caratterizzate. Le variazioni statistiche fra le caratteristiche elettro-termiche delle celle al litio che compongono la batteria, infatti, portano ad una riduzione consistente delle performance dell’intera batteria.
Inizialmente viene definito un nuovo modello elettro-termico a parametri concentrati della singola cella al litio e contestualmente viene descritta la procedura per l’estrazione dei parametri durante alcuni cicli di carica e scarica. Di seguito viene proposto e descritto un ambiente di simulazione in SystemC-WMS per la simulazione dell’intero battery-pack. Il modello della cella proposto è stato validato utilizzando delle misure sperimentali attenute a diverse temperature utilizzando una camera climatica. Il modello è stato poi utilizzato per simulare una batteria composta da 48 celle introducendo delle variazioni statistiche fra i parametri. L’ambiente di simulazione proposto consente di evidenziare ed analizzare i differenti comportamenti fra le celle in termini di stato di carica, correnti, tensioni, e flusso di calore. Alcune simulazioni portate a termine con il metodo Montecarlo hanno consentito di analizzare l'influenza della variazione statistica di ciascun parametro sulle prestazioni della batteria.
Nella parte finale della tesi viene presentata una piattaforma hardware composta da un BMS, un carica-batterie, sei celle al litio ed un software che gestisce la simulazione. La piattaforma agevola lo sviluppo di algoritmi di carica e bilanciamento ed alcuni test dimostrano l’utilità della piattaforma durante il confronto di alcuni algoritmi di bilanciamento proposti.The market for lithium-ion batteries is growing exponentially. The performance of battery cells is growing due to improving production technology, but market request is growing even more rapidly. The lithium batteries embeds a battery management system that measure the voltage and temperature of the cells and controls the battery. Modeling and characterization of single cells and an efficient simulation environment is fundamental for the development of an efficient battery management system. One of the critical aspects of the use and management of lithium-ion battery packs is the statistical variations of the electro-chemical-thermal characteristics of the single cells. The first part oh this thesis is devoted to defining a novel lumped electrothermal circuit of a single battery cell, the extraction procedure of the parameters of the single cell from experiments, and a simulation environment in SystemC-WMS for the simulation of a battery pack. The electrothermal model of the cell was validated against experimental measurements obtained in a climatic chamber. The model is then used to simulate a 48-cell battery, allowing statistical variations among parameters. The different behaviors of the cells in terms of state of charge, current, voltage, or heat flow rate can be observed in the results of the simulation environment. The Montecarlo method on the SystemC-WMS simulations has also been used. In the last chapter is presented an HW platform composed by a custom open-source BMS with a standard Arduino Uno compatible pin-out, a battery charger, six lithium cells, and the software that manages the test. The platform is validated by using a passive cells balancing algorithm and a charging algorithm that interacts between them. The test shows as during the passive balancing the algorithm must take into account also the temperature of the board. The platform helps to develop of charging and balancing algorithms and some experiments shown the benefits of the platform during the comparison of some balancing algorithms
Design and energetic analysis of a self-powered Bluetooth low energy speed sensor
No full textMost of the speedometers on bicycles uses batteries. Batteries are polluting materials and they must be replaced. This paper presents an implementation of a self-powered speed sensor that uses energy harvesting to power itself, it measures the speed and transmits the data using Bluetooth Low Energy (BLE) to external devices such as smartphones. The energy harvester is a coil that acts as sensor, too. A prototype of the sensor has been built and a voltage regulation circuit has been simulated by using a SPICE simulator. Furthermore, a custom firmware has been designed using a Bluetooth Low Energy nRF51822 SoC by Nordic Semiconductor and the parameters of the BLE connection has been accurately chosen to obtain low energy consumptions. Finally, the energy balance between the harvested energy by the coil and the used energy by the SoC has been accomplished. The results demonstrate the technical feasibility of the self-powered BLE speed sensor for bicycles
Lithium-ion Battery Electrothermal Model, Parameter Estimation, and Simulation Environment
Get PDFThe market for lithium-ion batteries is growing exponentially. The performance of battery cells is growing due to improving production technology, but market request is growing even more rapidly. Modeling and characterization of single cells and an efficient simulation environment is fundamental for the development of an efficient battery management system. The present work is devoted to defining a novel lumped electrothermal circuit of a single battery cell, the extraction procedure of the parameters of the single cell from experiments, and a simulation environment in SystemC-WMS for the simulation of a battery pack. The electrothermal model of the cell was validated against experimental measurements obtained in a climatic chamber. The model is then used to simulate a 48-cell battery, allowing statistical variations among parameters. The different behaviors of the cells in terms of state of charge, current, voltage, or heat flow rate can be observed in the results of the simulation environment
Statistical characterization of lithium-ion batteries using SystemC-WMS
No full textThe mismatch of the electro-chemical-thermal characteristics of lithium-ion cells represents a critical aspect in the use and control of a battery pack. When the cells are placed in series or in parallel the effect of the mismatch between the cells causes degradation of the performances of the battery pack. This paper presents a simulation environment for the analysis of the performances of a battery pack affected by mismatch of its cell parameters
Effects of variability of the characteristics of single cell on the performance of a lithium-ion battery pack
No full textRising crude oil prices and worldwide awareness of environmental issues have resulted in increased research and development of energy storage systems. Batteries are one of the most attractive energy storage systems because of their high efficiency and low pollution. Because of their high-energy densities and long lifetimes, lithium-ion batteries are increasingly used not only in electrical vehicles, but also in other applications. A key point in the management of lithium-ion batteries is expanding their energy storage capability and lifetimes. To achieve this, a fundamental embedded system is the battery management system (BMS) needed to ensure optimal, reliable and safe operation of the battery. Modelling and characterization of the single cells and an efficient simulation environment is fundamental for the development of an efficient BMS. This work presents a study of the statistical variations of the characteristic parameters of the single cells on the performances of a battery pack. The Montecarlo method on the SystemC-WMS simulations has been used
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
- …
