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

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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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