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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.
1

The accelerated life cycle testing and modelling of Li-ion cells used in electric vehicle applications

Rossouw, Claire Angela January 2012 (has links)
Li-ion batteries have become one of the chosen energy storage devices that are used in applications such as power tools, cellular phones and electric vehicles (EV). With the demand for portable high energy density devices, the rechargeable Li-ion battery has become one of the more viable energy storage systems for large scale commercial EVs because of their higher energy density to weight or volume ratio when compared to other current commercial battery energy storage systems. Various safety procedures for the use of Li-ion batteries in both consumer and EV applications have been developed by the international associations. The test procedures studied in this dissertation demonstrated the importance of determining the true capacity of a cell at various discharge rates. For this, the well known Peukert test was demonstrated. The study also showed that cells with different battery geometries and chemistries would demonstrate different thermal heating during discharge and slightly different Ragone results if different test methods were used as reported in the literature. Accelerated ageing tests were done on different cells at different Depth-of-Discharge (DoD) regions. The different DoD regions were determined according to expected stresses the electrode material in a cell would experience when discharged to specific DoD that follows the discharge voltage profile. Electrochemical Impedance Spectroscopy (EIS) was used to measure various electrochemical changes within these cells. The EIS results showed that certain observed modelled parameters would change similarly to the ageing of the cell as it aged due to the accelerated testing. EIS was also done on cells at different State-of-Charge (SoC) and temperatures. The results showed that EIS can be used as an effective technique to observe changes within a Li-ion cell as the SoC or temperature changed. For automotive vehicles that are powered by a fuel cell or battery, a supercapacitor can be coupled to a battery in order to increase and optimize the energy and power densities of the drive systems. A test procedure in the literature that evaluated the use of capacitors with Pb-acid batteries was applied to Li-ion type cells in order to quantify the increased power due to the use of a supercapacitor with a Li-ion cell. Both a cylindrical LiCoO2 cell and a VRLA Pb-acid cell showed some additional charge acceptance and delivery when connected to the supercapacitors. A LiMn2O4 pouch cell showed significant charge acceptance and delivery when connected to supercapacitors. The amount of additional charge acceptance and delivery of the different combinations could be explained by EIS, in particular, the resistance and capacitance of the cell in comparison to the combination of the cell and supercapacitor. A large capacity LiCoO2 cell showed high charge acceptance and delivery without connection with a supercapacitor. The study proved that EIS can be used to model the changes within cells under the different conditions and using different test procedures.
2

Technology Planning for Aligning Emerging Business Models and Regulatory Structures: the Case of Electric Vehicle Charging and the Smart Grid

Cowan, Kelly R. 07 December 2017 (has links)
Smart grid has been described as the Energy Internet: Where Energy Technology meets Information Technology. The incorporation of such technology into vast existing utility infrastructures offers many advantages, including possibilities for new smart appliances, energy management systems, better integration of renewable energy, value added services, and new business models, both for supply- and demand-side management. Smart grid also replaces aging utility technologies that are becoming increasingly unreliable, as the average ages for many critical components in utility systems now exceed their original design lives. However, while smart grid offers the promise of revolutionizing utility delivery systems, many questions remain about how such systems can be rolled out at the state, regional, and national levels. Many unique regulatory and market structure challenges exist, which makes it critical to pick the right technology for the right situation and to employ it in the right manner. Technology Roadmapping may be a valuable approach for helping to understand factors that could affect smart grid technology and product development, as well as key business, policy and regulatory drivers. As emerging smart grid technologies are developed and the fledgling industry matures, a critical issue will be understanding how the combination of industry drivers impact one another, what barriers exist to achieving the benefits of smart grid technologies, and how to prioritize R&D and acquisition efforts. Since the planning of power grids often relies on regional factors, it will also be important investigate linkages between smart grid deployment and regional planning goals. This can be used to develop strategies for overcoming barriers and achieving the benefits of this promising new technology. This research builds upon existing roadmapping processes by considering an integrated set of factors, including policy issues, which are specifically tuned to the needs of smart grids and have not generally been considered in other types of roadmapping efforts. It will also incorporate expert judgment quantification to prioritize factors, show the pathways for overcoming barriers and achieving benefits, and discussing the most promising strategies for achieving these goals.
3

Analysis of fuel consumption reduction potential through the use of an electrically driven air conditioning compressor

Marais, Charel January 2007 (has links)
The disturbing current situation regarding the world climate has initiated a major wave of urgent developments towards decreasing the overall impact of human activities on the living environment. A major role player in this development is the automobile industry that is inherently connected to pollution of various types, be it air, water or noise pollution. There have been drastic changes not only in the technologies employed in producing vehicles and components, but also in the construction and technologies built into modern automobiles to lessen the overall environmental impact of the industry. Noxious emissions have been decreased, overall efficiencies increased and vehicles are becoming more economical with each new generation. Stricter laws dictate that the level of acceptable vehicle emissions is to be decreased ever further and all manufacturers are developing various possibilities to achieve this. With the emergence of hybrid vehicle technology, there was also a sudden development of different electrical systems that were made viable by the higher onboard voltage systems employed in hybrid vehicles. One of these developments was the electrical air conditioning compressor for use in automobile applications. Although it is designed to operate with a higher voltage than the traditional 12V onboard vehicle systems, it is theoretically possible to incorporate it into a 12V system by making use of a DC-DC converter to step up the supply voltage of the electrical compressor sufficiently to allow for its successful operation. The question therefore arises whether it would be feasible and sensible to employ an electrical air conditioning system in conventional combustion engine vehicles from an overall fuel consumption and vehicle emissions point of view. A modelling approach was taken where an overall vehicle driving simulation was created to represent an average modern production vehicle. The simulation was then extended to include the options of incorporating models for both mechanically and electrically driven air conditioning systems. This provides insight into the influences of the air conditioning system on the vehicle’s overall fuel consumption and an opportunity to compare the influences from the two different systems. This study attempted to provide answers to some of the viability questions regarding the incorporation of electrically driven air conditioning systems into vehicles that use standard 12V onboard voltage systems. It was found that the electrical system has definite potential as a viable replacement option for the conventional system should it be combined with an appropriate alternator and equipped with an efficient control system.
4

PV Based Converter with Integrated Battery Charger for DC Micro-Grid Applications

Salve, Rima January 2014 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / This thesis presents a converter topology for photovoltaic panels. This topology minimizes the number of switching devices used, thereby reducing power losses that arise from high frequency switching operations. The control strategy is implemented using a simple micro-controller that implements the proportional plus integral control. All the control loops are closed feedback loops hence minimizing error instantaneously and adjusting efficiently to system variations. The energy management between three components, namely, the photovoltaic panel, a battery and a DC link for a microgrid, is shown distributed over three modes. These modes are dependent on the irradiance from the sunlight. All three modes are simulated. The maximum power point tracking of the system plays a crucial role in this configuration, as it is one of the main challenges tackled by the control system. Various methods of MPPT are discussed, and the Perturb and Observe method is employed and is described in detail. Experimental results are shown for the maximum power point tracking of this system with a scaled down version of the panel's actual capability.

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