Evaluation of a high rate hybrid energy storage module (HESM)

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 non-trivial 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 method proposed 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. At UTA, an actively controlled, high rate HESM has been constructed to evaluate its performance under the typical load condition of directed energy weapon operation. It has been assembled using lithium-ion batteries, EDLCs, and commercial off the shelf (COTS) 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.