Search

Ultracapacitors (UCs) are of increasing interest in different application areas, such as microgrids and transportation, which demand high transient power and are growing in capability every day. New power system architectures have been proposed that may be well suited to reliably and efficiently supply power to these previously unseen applications. Among the architectures that hold a great deal of promise are hybrid energy storage modules that integrate energy dense batteries with power dense UCs into a single power supply that augments traditional generation technologies. Within such architecture, the UC is the element that may be utilized to sink and source power quickly, at the leading or falling edge of a transient event. Considerable advances have been made to increase both the power and energy density, respectively, of UCs. Significant reduction of the internal impedance has resulted in an increased power capability that makes UCs well suited for use in these applications. Hybrid UC technologies, such as lithium-ion capacitors, have been developed, which have much higher energy density with nearly the same power density. In an effort to better understand and validate the capabilities of new UC technologies, a series of experiments has been performed on cells from four different manufacturers. Novel experimental testbeds and methods have been used to measure each technology’s internal impedance and power density. The experimental testbed utilized, along with the results collected to date, will be presented. [ABSTRACT FROM AUTHOR]

Hybrid Energy Storage Modules (HESM) have emerged as a possible energy storage device for naval pulsed power applications [1–6]. A HESM combines energy dense and power dense devices to offer a holistic solution for repetitive loads that are highly transient in nature. Actively controlled power electronic converters are used to regulate the power that flows from each energy storage or generation source to a point of common coupling. In these types of naval applications, it is likely that the system will be comprised of components that are available as commercially off the shelf (COTS) components, though some may be custom designed as well. Combining COTS components in a HESM can be challenging because system-level control must be imposed on top of individual device control. Previous work at the University of Texas at Arlington (UTA) has demonstrated a basic model of a HESM and a fuzzy logic systemlevel controller through software simulation. Building on the work by UTA, this paper will validate a model of a Hybrid Energy Storage Module with fuzzy logic system-level control under the effects of a transient pulsed power load. [ABSTRACT FROM AUTHOR]

There is considerable need for a mobile, reliable, efficient, and compact prime power supply for a host of applications, including directed energy and electrical grid backup among others. Electrochemical energy storage devices, which possess either high-power density or high-energy density, have been developed recently and are very applicable for use in these applications. The need for both high energy and high power, however, makes the design and implementation of such a prime power supply a nontrivial task. While lithium-ion batteries (LIBs) are available, which possess both high power and energy density, operation at high power reduces their cycle life, decreasing the reliability and increasing the cost of the system when replacement becomes necessary more frequently. One proposed method involves optimally combining high-energy batteries with high-power electric double layer capacitors (EDLCs) using actively controlled power electronics to regulate the current to and from each respective device. In such a scheme, energy can be slowly sourced to and from the batteries, while the capacitors are used to supply or accept the bulk of the current when the demand is high, especially during fast transients. This type of scheme should not only maximize the batteries’ cycle life and ensure that both the energy and power required of the load(s) is always available, but will also increase the instantaneous power capabilities of the system, offering a well-rounded solution to sourcing steady and/or transient loads. When augmenting a fossil fuel generator with a hybrid energy storage module (HESM), the HESM has the ability to act as a high-energy reservoir that can harvest energy from the generator when the loads are in short periods of inactivity. This enables the generator to be continuously base loaded, thereby maintaining a high level of efficiency at all times, while theoretically maintaining the required power quality of the main ac bus. At the University of Texas at Arlington (UTA), an actively controlled, high-rate HESM has been constructed to evaluate its performance under the typical load condition presented by directed energy weapons. It has been assembled using LIBs, EDLCs, and commercial off-the-shelf power electronic converters. A discussion about the future of HESMs, the experimental setup at UTA, and the results obtained thus far will be presented here. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM PUBLISHER]

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 C rating. While this mode of operation has been shown to be possible, the elevated rate limitations of these types of devices are not well published, and it is unclear how the fundamental aging phenomena that occur inside these types of devices will be affected. Researchers at the University of Texas, Arlington, have ongoing experiments which are testing the limitations of these types of electrochemical cells for use in pulsed high-current applications. Experiments are also being performed to understand the aging characteristics when they are operated at elevated rates that are tens to hundreds of their rated C values. This paper describes the rationale behind the experiments, the experimental setup, and the research progress made thus far. [ABSTRACT FROM PUBLISHER]