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AAWSAP DIRD, Ultracapacitors as Energy and Power Storage Devices, November 2010

U.S. Department of War · 2010-11-01 · 34 pages · text from the file's own layer

This Defense Intelligence Reference Document was prepared by the Defense Intelligence Agency's Defense Warning Office and dated 1 November 2010. It is one of a series of advanced technology reports produced under the Advanced Aerospace Weapons System Applications Program. The report reviews how ultracapacitors work, how they compare with batteries, their history and materials, and their commercial, military and aerospace uses. It concludes that new materials and cell designs will raise energy density and that the U.S. government must understand the devices' spectral signatures.

From the source: Release of 2026-09-18 Incident: 11/1/10, Las Vegas, Nevada. Released with redactions. This document is a Defense Intelligence Reference Document (DIRD), a technical reference format used by the Defense Intelligence Agency (DIA) to capture baseline knowledge on a specific topic for later analytic use. DIRDs are best understood as reference and synthesis products rather than as original research. It is one of 38 DIRDs produced under the Advanced Aerospace Weapon System Applications Program (AAWSAP) between 2009 and 2011. Because AAWSAP’s scope permitted a broad range of supporting topics, not every DIRD in the series directly concerns aerospace systems or future threat assessment. The following summary reflects the DIRD’s scope and framing at the time of writing and should not be read as implying current validation of the concepts discussed. This DIRD surveys ultracapacitors as high-power energy-storage devices and argues that their main value lies in extremely rapid charge and discharge, very long cycle life, and usefulness in systems that need short bursts of power rather than sustained energy delivery. The report explains how ultracapacitors differ from batteries, reviews the materials and cell designs that determine their performance, and emphasizes that they are especially useful for power stabilization, backup power, load leveling, regenerative braking, and other applications where fast energy transfer matters more than total stored energy. It also notes their drawbacks, including lower energy density, self-discharge, and voltage-management requirements that limit their usefulness as stand-alone replacements for batteries in many applications. The document presents ultracapacitors as a maturing and increasingly important technology whose most credible aerospace and military uses lie in pulsed-power, missile and munitions systems, electric propulsion support, and other hybrid power architectures rather than in long-duration primary energy storage.

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Initial ultracaps used aqueous electrolytes made with Ab(SO4)3 (aluminum sulfate),
H2SO4 (sulfuric acid), or KOH (potassium hydroxide) . While these electrolytes have
excellent ionic conductivity, the operating voltage is limited to 1.2 volts using carbon
electrodes. Organic electrolytes have lower ionic conductivity, but the higher dielectric
constant increases the nominal cell voltage up to as high as 3 volts. Carbon has been
used as a high-surface-area electrode material since the inception of the
electrochemical capacitor. It is still the material of choice for many ultracapacitors; one
of the primary reasons is the low cost of carbon materials. However, there are many
types of carbon that are available for use as an electrode material. In addition to
carbonaceous electrodes, metal oxides and conductive polymers are find ing increasing
use in ultracap design. Advancements in the understanding of the electric double-layer
and ultracapacitor behavior have led to better materials utilization and, consequently,
improved devices.
Early electrochemical capacitors were rated at a few volts and had capacitance values
measured from less than one farad up to several farads. Today cells range in size from
small devices with exceptional pulse-power performance in the millifarad range up to
devices rated at several kilofarads. There are even some specialized ultracapacitor cells
now in production that have ratings of more than 100 kF. The technology is
experiencing increasingly broader use, replacing batteries in some cases and in others
complementing their performance. Ultracap technology has grown into an industry with
sales of several hundred million dollars per year that is poised for rapid growth in the
near term due to expansion of power quality needs and the emerging energy
management/conservation applications. 11
Advancements in ultracapacitors have led to numerous devices from an array of
manufacturers. Table 2 compares the various products on the market, showing voltage,
capacity, power density, and additional energy-storage characteristics. Ultracaps have
moved away from aqueous electrolytes and are typically organic electrolytes due to the
increased voltage performance. Electrodes vary from carbon/carbon systems to hybrid
systems using metal oxides or conductive polymers paired with a carbon electrode.
Packaging and sizes of ultracapacitors covers a large range as these are now used from
cellular communications and small electronics to power delivery and management for
seaport cranes. Ultracapacitor technology development is focusing on delivering better
energy density, and this is being approached by improved carbon electrodes, better
electrolytes, and alternative electrodes that provide pseudocapacitive behavior,
including battery-like electrodes. 12
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Official release, from the pursue collection. The PDF is mirrored here; the original link is above. 34 pages are in the text index: search them above, or from the library's search.