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HIGH ENERGY SODIUM BASED ROOM TEMPERATURE FLOW BATTERIES
Title
HIGH ENERGY SODIUM BASED ROOM TEMPERATURE FLOW BATTERIES
Creator
Shamie, Jack
Date
2015, 2015-12
Description
As novel energy sources such as solar, wind and tidal energies are explored it becomes necessary to build energy storage facilities to load...
Show moreAs novel energy sources such as solar, wind and tidal energies are explored it becomes necessary to build energy storage facilities to load level the intermittent nature of these energy sources. Energy storage is achieved by converting electrical energy into another form of energy. Batteries have many properties that are attractive for energy storage including high energy and power. Among many di erent types of batteries, redox ow batteries (RFBs) o er many advantages. Unlike conventional batteries, RFBs store energy in a liquid medium rather than solid active materials. This method of storage allows for the separation of energy and power unlike conventional batteries. Additionally ow batteries may have long lifetimes because there is no expansion or contraction of electrodes. A major disadvantage of RFBs is its lower energy density when compared to traditional batteries. In this Thesis, a novel hybrid Na-based redox ow battery (HNFB) is explored, which utilizes a room temperature molten sodium based anode, a sodium ion conducting solid electrolyte and liquid catholytes. The sodium electrode leads to high voltages and energy and allows for the possibility of multi-electron transfer per molecule. Vanadium acetylacetonate (acac) and TEMPO have been investigated for their use as catholytes. In the vanadium system, 2 electrons transfers per vanadium atom were found leading to a doubling of capacity. In addition, degradation of the charged state was found to be reversible within the voltage range of the cell. Contamination by water leads to the formation of vanadyl acetylacetonate. Although it is believed that vanadyl complex need to be taken to low voltages to be reduced back to vanadium acac, a new mechanism is shown that begins at higher voltages (2.1V). Vanadyl complexes react with excess ligand and protons to reform the vanadium complex. During this reaction, water is reformed leading to the continuous cycle in which vanadyl is formed and then reduced back to the original state. In the discharged state, it was found that precipitation occurs, but is due to solubility limits and not chemical reactions. The TEMPO system showed the potential of higher concentration catholytes although large capacity losses were found. Although no explanation is found, the behavior of the fade is related to time and concentration.
Ph.D. in Mechanical, Materials and Aerospace Engineering, December 2015
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ESTIMATION OF THERMAL STATE OF CHARGE FOR PCC BASED LITHIUM-ION BATTERY PACKS
Title
ESTIMATION OF THERMAL STATE OF CHARGE FOR PCC BASED LITHIUM-ION BATTERY PACKS
Creator
Salameh, Mohamad
Date
2016, 2016-07
Description
With continuing efforts to improve energy and power density of Li-ion batteries, heat generation and thermal safety remain critical barriers...
Show moreWith continuing efforts to improve energy and power density of Li-ion batteries, heat generation and thermal safety remain critical barriers to commercial success. Energy conversion in a battery is an exothermic process. Whenever the temperature of lithium-ion batteries increases, there can be direct consequences-reduced calendar and cycle life and higher risk of a battery re or explosion. Conventional approaches to prevent overheating use active thermal management systems, such as air conditioning or liquid cooling. However, these systems can be costly, bulky, and consume energy during operation. In addition they o er no overheat protection while the application or the vehicle is powered down. Phase change material composites (PCC) can be employed to rapidly absorb heat from the battery and distribute it, thereby enabling lightweight and compact packs with extended cycle-life and safety. This thesis proposes an online temperature estimation technique for a novel intelligent battery thermal management to actively monitor thermal mass of the phase change material. Such a system will not only enable avoidance of thermal issues, but will extend life of the battery pack by optimally selecting the operating point of the Energy Storage System. It can also be used to predict when active cooling should be employed just before the battery exits the phase change temperature plateau, to ensure latent heat absorption is spread across the entire drive cycle.
M.S. in Electrical Engineering, July 2016
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