David A. Wetz

Permanent gas analysis using gas chromatography with vacuum ultraviolet detection.

The analysis of complex mixtures of permanent gases consisting of low molecular weight hydrocarbons, inert gases, and toxic species plays an increasingly important role in todays economy. A new gas chromatography detector based on vacuum ultraviolet (VUV) spectroscopy (GC-VUV), which simultaneously collects full scan (115-240 nm) VUV and UV absorption of eluting analytes, was applied to analyze mixtures of permanent gases. Sample mixtures ranged from off-gassing of decomposing Li-ion and Li-metal batteries to natural gas samples and water samples taken from private wells in close proximity to unconventional natural gas extraction. Gas chromatography separations were performed with a porous layer open tubular column. Components such as C1-C5 linear and branched hydrocarbons, water, oxygen, and nitrogen were separated and detected in natural gas and the headspace of natural gas-contaminated water samples. Of interest for the transport of lithium batteries were the detection of flammable and toxic gases, such as methane, ethylene, chloromethane, dimethyl ether, 1,3-butadiene, CS2, and methylproprionate, among others. Featured is the capability for deconvolution of co-eluting signals from different analytes.

Design and Active Control of a Microgrid Testbed

Researchers at the University of Texas at Arlington (UTA) have installed a novel Microgrid testbed architecture that will be used for educational and research purposes. This paper documents the architecture of the UTA grid, the development of the national instruments based active control system, and some of the research progress made thus far. The specific commercial off the shelf components that make up the hardware in the system, which is actually broken up into three independent smaller grids, is described. A custom interconnection architecture will also be discussed that enables the three individual Microgrids to operate independently or in an actively interconnected mode of operation. The implementation of system control software will be presented in terms of the state machine used to develop the software. Finally, experimental data gathered from the dynamic performance of the Microgrid will be presented.

Evaluation of a Hybrid Energy Storage Module for Pulsed Power Applications

Before pulsed power systems can be fielded in either mobile or small footprint stationary applications, the prime power source must be optimized for both size and operational efficiency. In large footprint laboratories, prime power supplies are connected to a local utility grid to charge intermediate storage systems. In mobile platforms, alternative energy sources, such as electrochemical batteries or supercapacitors, must be used to backup smaller fossil fuel generators. The prime power source used in a pulsed power system must store high energy, to maximize the number of shots stored, and be able to source high power to recharge the intermediate store as fast as possible. Finding a single electrochemical energy storage device that has the right energy and power density for most applications is nearly impossible. Therefore, usage of batteries, which possess high energy density, along with electrochemical capacitors, which offer high power density, in a hybrid energy storage module (HESM) configuration is a promising way of combining both of these features into a single supply. Usage of this topology reduces the stress on the batteries, thereby prolonging their life, and also increases the instantaneous power capabilities of the system. This paper presents the design and validation of an actively controlled HESM built using commercial off the shelf power electronics and simple control strategies.

The Impact of Field Enhancements and Charge Injection on the Pulsed Breakdown Strength of Water

A unique theoretical model of the breakdown mechanism in water has been developed and further tested in both simulation software and experimentation. The conducted experiments test the degree to which electrode material, surface roughness, and surface area impact the dielectric strength of water. Voltage pulses with respective rise times of roughly 200 and 20 ns were applied to a water test gap producing electric fields in excess of 1.5 MV/cm. In experiments testing various electrode materials, thin film coatings of various metallic alloys and oxides were applied to Bruce-profiled stainless steel electrodes, with an effective area of 5 cm2, through ion beam deposition. Similar Bruceprofiled stainless steel electrodes with surface roughness ranging from 0.26 to 1.96 mum and effective areas ranging from 0.5 to 75 cm2 were used in the study of surface roughness and area. Additionally, shadowgraph images of a point plane geometry were taken to further understand the breakdown processes that occur

Evaluating the use of a MicroGrid as a power solution for Africa's rural areas

Energy availability and reliability is critical to the development of a region, especially for those still in the development phase. Africa, which is the largest and most populous continent after Asia, has only 2% of the worlds industrial capacity. Africas per capita income is roughly 15% of the world average and it consumes roughly 3% of worlds energy. Approximately one-third of the estimated 1.6 billion people worldwide that do not have access to electricity currently reside in Africa. Insufficient energy supply has been one of the main factors that have negatively impacted the development of Africa, especially in its rural areas. There are many options that exist for increasing the availability of electricity in this region of the world. The implementation of a MicroGrid is one such option. The intent of this paper is to evaluate the different MicroGrid concepts which could serve as an energy solution for Africas rural areas.

Pulsed Elevated Rate Discharge of Electrochemical Energy Storage Devices

A number of electrochemical energy storage devices have been developed and used widely to power portable applications. Lithium-ion batteries are extremely popular for use in portable devices as a result of their high energy density. Despite their high energy density, most commercial off-the-shelf cells are only modestly power dense, limiting them from being used to drive high power or pulsed power applications. Recently, new high power lithium-ion battery technologies such as the Saft VL5U cell have been developed, which are not readily available off the shelf, with power densities as high as 28.5 kW/kg [1] that are an attractive means for driving pulsed power systems. Additionally, advanced energy storage capacitors, such as electric double layer capacitors and lithium-ion capacitors, have been developed with high energy and power densities that also make them a suitable candidate for use in pulsed power applications. Previous research using these types of devices in applications other than as storage in hybrid electric vehicles and renewable energy platforms has been limited. The University of Texas at Arlington is currently engaged in research to understand the limitations of these types of devices and to understand their future potential for use in pulsed high current experiments. A test stand, similar to that of Chen [2], but with a higher electrical action capability, has been developed and used to further characterize the performance of these types of devices when they are discharged at rates 10s to 100s of times their rated C values in pulsed fashion. This paper describes the rationale behind the experiments, the experimental setup developed, and the research progress made thus far.

Capacity Fade of 26650 Lithium-Ion Phosphate Batteries Considered for Use Within a Pulsed-Power System’s Prime Power Supply

There is considerable need for a mobile, reliable, efficient, and compact prime power supply for use in a host of directed energy applications. Recent improvements in the energy and power density of electrochemical lithium-ion batteries have made them a very viable option for these types of applications where fast and rep-rate operation is of interest. Despite the proven ability of lithium-ion batteries to source high currents, it is still unclear how they age when they are used to repeatedly source high-rate currents in a pulsed manner, as they must when used in a repetitive rate prime power supply. Similarly, it is unclear how elevated rate recharge affects the life of the battery. Research has been performed at University of Texas at Arlington in which high-power, 2.6 Ah lithium-ion batteries have been repeatedly discharged and recharged at high pulsed rates. This paper will discuss the potential of lithium-ion batteries for use in these applications and will present experimental results performed when two 2.6 Ah cells were both discharged at 28 A (10.8C) and recharged at 9 A (3.5C) to 2.5 and 2.0 V, respectively.

An autonomous operation microgrid for rural electrification

Energy is one of the most critical economic, environmental, and developmental issues in the world. Developing countries in particular need access to a reliable, affordable, clean, and efficient energy service to elevate standards of living and to reduce poverty. As the largest and most populous continent after Asia, Africa has only 2% of the worlds industrial capacity. Its per capita income is only 15% of the world average and only consumes 3% of world energy. Approximately one-third of the estimated 1.5 billion people without access to electricity worldwide live in Africa. It is therefore urgent for these African countries, especially in rural areas, to find an accessible, reliable, efficient, and economically feasible way for electrification. This paper puts forward an intelligent microgrid as a solution for African rural electrification. Simulation verification and lab implementation are also presented in this paper.

Elevated Rate Cycling of High-Power Electrochemical Energy Storage Devices for Use as the Prime Power Source of an EM Launcher

In recent years, energy storage manufacturers such as GAIA Advanced Lithium Battery Systems, Saft America, JM Energy, and Maxwell Corporation, among others, have greatly increased the power density of their respective electrochemical energy storage cells. Among the many types of high-power cells produced by the manufactures just listed are lithium-ion batteries, lithium-ion capacitors, and electric double-layer capacitors, respectively. The increased power density has made these types of portable energy storage devices more appealing and feasible for use as the prime power source of pulsed-power supplies that are used to drive systems such as electromagnetic launchers (EMLs). It has been previously shown by both Sitzman at the Institute for Advanced Technology, The University of Texas, Austin, and Allen and Neri at the U.S. Naval Research Laboratories that the prime power for small EMLs is derived from different types of batteries. In these types of pulsed-power systems, the batteries must be able to source pulsed currents at rates much higher than their continuous

Fast Recharge of Electrochemical Energy Storage Devices at Pulsed Elevated Rates

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