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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.
201

Physics-Based Modeling of Degradation in Lithium Ion Batteries

Surya Mitra Ayalasomayajula (5930522) 03 October 2023 (has links)
<h4>A generalized physics-based modeling framework is presented to analyze: (a) the effects of temperature on identified degradation mechanisms, (b) interfacial debonding processes, including deterministic and stochastic mechanisms, and (c) establishing model performance benchmarks of electrochemical porous electrode theory models, as a necessary stepping stone to perform valid battery degradation analyses and designs. Specifically, the effects of temperature were incorporated into a physics-based, reduced-order model and extended for a LiCoO<sub>2</sub> -graphite 18650 cell. Three dimensionless driving forces were identified, controlling the temperature-dependent reversible charge capacity. The identified temperature-dependent irreversible mechanisms include homogeneous SEI, at moderate to high temperatures, and the chemomechanical degradation of the cathode at low temperatures. Also, debonding of a statistically representative electrochemically active particle from the surrounding binder-electrolyte matrix in a porous electrode was modeled analytically, for the first time. The proposed framework enables to determine the space of C-Rates and electrode particle radii that suppresses or enhances debonding and is graphically summarized into performance–microstructure maps where four debonding mechanisms were identified, and condensed into power-law relations with respect to the particle radius. Finally, in order to incorporate existing or emerging degradation models into porous electrode theory (PET) implementations, a set of benchmarks were proposed to establish a common basis to assess their physical reaches, limitations, and accuracy. Three open source models: dualfoil, MPET, and LIONSIMBA were compared, exhibiting significant qualitative differences, despite showing the same macroscopic voltage response, leading the user to different conclusions regarding the battery performance and possible degradation mechanisms of the analyzed system.</h4>
202

Začleňování fotovoltaických elektráren do elektrizační soustavy / Integration of Photovoltaic Power Plants in the Electricity System

Michl, Pavel January 2010 (has links)
The thesis discuses an integration of photovoltaic power stations to electric network. The first part describes connecting conditions of small sources to distribution system, including administrative requirements, feasibility study, and requirements to the energy meters, measuring, control devices, switching devices and protection. The second part is aimed to describe problems of the photovoltaic system. Solar radiation generating and reducing of its intensity incident upon the earth surface are described in this part. The quantum of produced electric power depends on climatic conditions in the fixed area, seasons, etc. This work also discusses the types of photovoltaic cells and their actual efficiency. Inverters are further important components of the photovoltaic system. The parameters of the inverters have a great influence on the total actual efficiency of the photovoltaic system. Different methods of the photovoltaic panels’ connection with the inverters and their advantages and disadvantages are also mentioned. The supporting structure of the photovoltaic panels and eventually transformer are further important components of photovoltaic system. The work also analyze the methods of connection of the photovoltaic power station to distributive low voltage and medium voltage network, electric energy accumulation and possibilities of the sale of produced electric energy. The large number of the connected photovoltaic power stations has negative influences to electric network. The third part contains the design of a photovoltaic power plant with a capacity of 516,24 kWp on the scoped area in southern Bohemia. The project documentation for the location where the power plant is designed is also made. It contains the design of photovoltaic panels, the design of the inverters to get an optimal power load. This part also contains a calculation of the photovoltaic system losses and the design of transformer and the cable junction calculation of the distributive system. The feasibility study of the power plant connected to distributive system is also conducted. Its delivery rate will be connected to the distribution point Řípov (110/22 kV). The calculation results show us that this photovoltaic power plant can be linked to the distribution system. The final part of this paper contains an economic estimate of the photovoltaic power plant operating and the calculation of the return. An Economic return is influenced by the wide range of values that affect the total return rate. The calculation of an operating economy is made for several variants. The return rate in refer to contemporary redemption price for 2010 with no consideration for a bank loan is 7 years. If we consider the bank loan it would be 12 years. The penetrative reduction of the redemption price is expected for 2011. Calculation works with the decline of 30 %. It would extend the rate of return to 11 years without a bank loan or to 22 years with the bank loan. The bank loan is considered to cover 80 % of the investment.

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