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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Figure 3. Ragone Plot. The graph illustrates the areas where ultracaps and batteries dominate in the power
density versus energy density relationship.
HISTORY
The concept of storing electrical energy in the electric double layer that is formed at the
interface between an electrolyte and a solid has been known since t he late 1800s. In
1966, Standard Oil Company of Ohio (SOHIO) invented the device in the format now
commonly used, which forms the basis for hundreds of patents and t housands of
journal articles. Figure 4 shows a drawi ng from the electrochemical double-layer device
invented by SOHIO. NEC introduced the SuperCapacitor™ in 1978 under license from
SOHIO.
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Figure 4. Electrolytic Capacitor as Designed and Patented by SOHIO.
From this point on, ultracaps have rapidly evolved through several generations of
designs. In the 1980s, Matsushita Electric Company developed a method of
manufacturing ultracapacitors with improved electrodes. Initially, they were used as
backup power devices for volati le clock chips and complementary metal-oxide
semiconductor (CMOS) computer memories . As the technology became more
understood, more and more applications were developed for ultracaps. Many other
applications have emerged over the past 30 years, including wireless communication,
power quality, and improved energy efficiency through regenerative energy capture
processes, as found in hybrid electric vehicles.10
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