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This Defense Intelligence Reference Document from the Defense Intelligence Agency, dated 1 November 2010, was one of a series of advanced technology reports produced in FY 2010 under the Advanced Aerospace Weapons System Applications (AAWSA) Program. It reviews ultracapacitors as energy and power storage devices. It covers how they work, their materials, their commercial and military uses, and new developments such as carbon nanotubes, thin films and magnetic capacitors. It concludes that the U.S. government must understand and adopt advanced ultracapacitors.
UNCLASSIFIED//F8A 8FFHil.l1k WE&i a••k>/ Table 1: Contrasting Properties of Batteries and Ultracapacitors9 Characteristic State of the Art Lithium Ion Battery Ultracapacitor Charge time ~3-5 minutes ~1 second Discharge time ~3-5 minutes ~1 second Cycle life 500,000 Specific Energy (Wh/kg) 100-200 5 Specific power (kW/kg) 0.5 -1 5-10 Cycle efficiency(%) 90% 95% Cost/Wh $1-2/Wh $10-20/Wh Cost/kW $75-150/kW $25-50/kW The voltage curve for an ultracapacitor is proportional to the depth of discharge, whereas batteries deliver a relatively constant voltage over a long discharge period. The sloping voltage curve of an ultracap can be advantageous for state-of-charge determinations. However, this is also responsible for the decreased energy density available in an ultracapacitor. For applications requiring energy to be delivered over a longer time scale or delivered at a constant voltage, the relatively flat voltage curve found in most batteries would be the preferred option. In instances where power is to be delivered or received quickly, or where many cycles are required, an ultracap is ideal. To better understand the differences between batteries and ultracaps, it helps to think of batteries as storing watt-hours of energy and ultra caps as storing watts of power. A Ragone plot illustrates the distinctions by plotting power versus energy in a logarithmic scale. As can be seen in Figure 3, ultracaps make an excellent option where high power density is required. The times shown are rough estimates for a full charge or discharge, which are estimates to help understand the relationship between energy density and power density. Batteries have made significant improvements to power delivery recently, but batteries remain the high-energy-density solution. Ultracapacitors are often thought of as a stop-gap between conventional capacitors and batteries. Recent developments of hybrid capacitors have led to considerable progress toward higher energy density. However, there is a tradeoff between high energy density and high- power devices, and the distinctions between the two require consideration of application requirements when choosing the energy storage platform for a system. The differences between ultracaps and batteries do not make the two mutually exclusive. There are applications where either a battery or an ultracap is the preferred energy storage platform. Quite often, these two can be used together in systems to perform complementary roles. 4 UNCLASSIFIED/ ,'1'81l 8fl'Uil,t.l, Wli&i lil'llolf
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Report, from the dia 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.