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

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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Ultracapacitors as Energy and Power Storage Devices for
Commercial and Military Applications
Summary
Ultracapacitors (ultracaps) are energy storage devices capable of extremely
rapid charge and discharge rates with the ability to be cycled hundreds of
thousands of times. These unique capabilities make ultracaps attractive for a
number of applications. The advantages over lithium ion batteries are
somewhat mitigated by the fact that they have less than 10% of the specific
energy (Wh/kg) and require a power converter to regulate their voltage. The
high capacitance is achieved by the enormously high surface area of the
carbon electrodes compared to planar electrolytic capacitors. Ultracapacitors
are commonly used to provide voltage stabilization of power converters and to
supplement peak-power loading of electrical systems. Their application has
expanded from electronics and telecommunications to industrial load leveling
and transportation. Due to their durability, their use in aerospace has been for
munitions fusing and missile power load leveling. Ultimately, application will
be pulsed power storage and delivery for electric propulsion and directed
energy weapons.
Recent developments in ultracapacitors have focused on different active
materials and electrode designs. By using advanced carbons, polymers, and
metal oxides, increased power density and energy density can be achieved.
Oxide-based thin-film ultracaps have demonstrated high-performance energy
and power density, approaching theoretical limits. Carbon nanotubes and
advanced carbons have been used as additives to and solely as electrode
materials. Nanostructured materials and thin-film manufacturing process
improvements will generate breakthroughs in mass production. Magnetic
capacitors are a recent development, manufactured using semiconductor
processes on silicon wafers. They possess a different storage mechanism and
will transform energy storage and pulsed-power applications. Ultracapacitors
are reaching widespread adoption and they are now available to support
electronics through transportation. New advancements in materials will enable
high-energy density devices with exceptional power capabilities.
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