Materials Research to Meet 21st-Century Defense Needs (2003) / Chapter Skim
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4 Energy and Power Materials
4 Energy and Power Materials
Pages 55-94
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From page 55... ...
Batteries for energy storage, from small portables to large shipboard units, Capacitors for storage and release of pulsed power, Fuel cells for efficient direct conversion of chemical to electrical energy for platform power, meet, vehicles (UAVs)
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To satisfy the broad-ranging charter given to this committee, a separate Panel on Energy and Power Materials was appointed to treat such subareas as batteries, fuel cells, and energetic materials. Other panels addressed specific energy and power areas that fell within their purviews.
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, photosynthesis - Biomimetic kinetic energy protection (armor) - Bioinspired battery and fuel cell devices Energy and power materials addressed by panels of the committee.
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The most important component in this category, for both small-scale and large-scale energy conversion systems, is the fuel cell. The panel also examined materials for inorganic photovoltaic (PV)
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; . Fuel cells (direct conversion of chemical to electrical energy across a range of applications)
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SPECIFIC AREAS OF OPPORTUNITY In the sections below, DoD needs for energy and power materials are exam i ned i n specific categories: Energy storage, Energy conversion, Electric power generation and transmission, Kinetic energy dissipation, and DoD reliance on energy sources. Additional information on materials for specific applications is provided in Appendix D
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From page 61... ...
These "energetic materials" will enable the lighter, more lethal force structure envisioned by the Army beginning now and continuing through 2020.4 A driving goal for much of the DoD-wide system transformation is a shift to smaller platforms with increased lethality.2 Higher-energy-density explosives and propellants combined with precision targeting systems translate into smaller warheads, enhanced penetration, longer range, and reduced ammunition logistics support.3 In addition, novel propellant materials may be able to reduce launch signature, thus increasing survivability by reducing detectability.4 This class of materials includes chemical fuels for platform mobility, which now account for some 70 percent of war tonnage shipped to combat locations Mandrels, M., "Army Vision and S&T: Accelerating the Pace of Transformation," paper presented to the Committee on Materials Research for Defense After Next, National Research Council, Washington, DC, February 15, 2000. 2Ullrich, G.W., "Advanced Energetic Materials: Introduction and Overview," paper presented to the Committee on Advanced Energetic Materials and Manufacturing Technologies, National Research Council, Washington, DC, July 31, 2001.
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From page 62... ...
Additional information is provided in Appendix D iquid fuel form for use in internal Electrochemical Energy Storage Background: Batteries and Electrochemical Capacitors Batteries and electrochemical capacitors are energy storage devices that convert chemical into electrical energy and are particularly suited to provide the energy to power electrical devices.
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From page 63... ...
DoD system energy and energy storage requirements vary enormously, ranging from tiny batteries to power man-portable communication systems to huge systems to power submarines. Diversity in capacity, physical size, weight and shape, drain rate capability, thermal performance, cycle life, shelf life, and cost make it impossible to define a single optimal battery.
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_ . _ C' An x FIGURE 4-2 Specific Energy, Wh/kg Ragone plot comparing nominal performance of batteries, electrochemical capacitors, and dielectric capacitors.
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Furthermore, commercial devices are not held to the same reliability standards as those required by the military. The reliability driver for commercial power sources is to minimize warranty expenses; the reliability driver for future DoD systems is mission success and soldiers' lives.
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and have extended the cycle life by over two orders of magnitude (Bates, 20001. Pulsed laser deposition of active materials holds promise (Singh et al., 2000)
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Of major interest to DoD applications would be improved performance at higher frequencies. Little work is now funded on interracial chemistry as it relates to power sources.
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While it can apply to nanostructured materials, it is a more general concept that may be used to tailor materials microstructure. Therefore, computational materials science should be an integral part of any systematic materials discovery effort.
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Compared to other forms of electrical energy storage, such capacitors are lower in energy density but higher in power density, and they are more readily cycled at high frequencies. Pulsed power applications for future DoD systems may require from 0.4 to 40 MJ/discharge, with an average instantaneous power of 0.5 to 7 Gwatt.5 Future ceramic-based power capacitors will require novel formulations and processing methods for tough, defect-free, low-loss ceramic and glasses for use in configurations that are scalable to different sizes to meet different application needs.
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From page 70... ...
Chemical Energy Storage "Energetic materials" is a collective term for military high explosives, propellants, and pyrotechnics; it is often used as a synonym for "military explosives" (DoD, 1 9991. In this chapter, this definition is expanded to include chemical fuels, such as diesel and jet fuel an important class of materials for powering military platforms.
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Polyatomic nitrogen compounds have the potential to yield propellant materials with double or triple the specific impulse Isp of hydrazine, and also have potential for enhanced explosives.8 These compounds include ~Danen, W.C., "Los Alamos Advanced Energetics Programs," paper presented to the Committee on Advanced Energetic Materials and Manufacturing Technologies, National Research Council, Washington, DC, August 1, 2001.
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From page 72... ...
However, any effort to examine nanocomposites for energetic materials will likely require sorting through the materials currently used in propellants at larger sizes as well as examining a myriad of alternatives for combination at the nanoscale. Such an effort could benefit greatly from computational materials science and combinatorial chemistry techniques.
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From page 73... ...
Program," paper presented at 221 st ACS National Meeting, San Diego, CA, 2001. Carroll, J.J., "Nuclear Isomers and X-ray Driven Gamma Emission," paper presented to the Committee on Advanced Energetic Materials and Manufacturing Technologies, National Research Council, Washington, DC, October 25, 2001.
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For the sake of brevity, discussion of these latter areas is limited to Annendix D, which also contains an expanded section addressing fuel cells. · , , The panel notes that materials for energy storage and conversion in this chapter are discussed without regard to the specific hardware configuration adopted.
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, military applications place unique demands on fuel cells. For shipboard applications, the fuel cell must be highly tolerant of saline and humid environments and possess high shock resistance; in submarines, fuel cells must be equipped not only with a fuel supply but also with an oxidant supply; for large-scale power needs, military fuel cells would ideally be compatible with diesel fuels such as JP8 and JP-3, whereas for small-scale, single-soldier applications, rapid startup and high energy and power densities are of paramount importance.
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From page 76... ...
they can be operated in a closedcycle system that uses as input solar or nuclear energy and uses fuel cell waste products to generate chemical fuels for reuse in the fuel cell (see Figure 4-~. This latter mode of operation may be particularly advantageous in future military operations, in which shipboard-based nuclear energy and high-efficiency photovoltaic devices could be used to reduce DoD reliance on increasingly scarce fossil fuels.
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From page 77... ...
Research Required to Meet DoD Needs The panel addressed the breakthroughs needed in fuel cell research to meet DoD needs within the context of three topical areas: electrolytes, electrodes and electrocatalysis, and fuels and fuel cell system design. It should be noted, however, that advances in one component or aspect will dramatically affect the others.
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From page 78... ...
, which can result in uncontrolled combustion. Zero methanol crossover electrolytes would reduce the amount of unnecessary water carried by the soldier or a supporting robot by a factor of about four while increasing the power density of the fuel cell by at least a factor of two.
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new synthetic methodologies that allow for architectural control of fuel cell electrodes at the nanoscale, potentially enhancing reaction kinetics by dramatically increasing electrode surface area and restricting reactions to confined regions. Though the fuel cell community has yet to take advantage of such advances, it is at the interface between these fields and traditional electrochemistry that the most significant breakthroughs can be anticipated.
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MEMS micropower sources (gas turbines, fuel cells) and microchemical processing plants for fuel reforming are the two MEMS technologies that are most relevant to the work of the Energy and Power Panel.
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MEMS microturbines can also be used for power for the individual soldier and auxiliary power sources. Wafer-level integration of multiple microturbines may enable modular power sources in increments of 40 to 50 W (the power level of one microturbine)
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16-18, 1999; Tang, W., "MEMS Program at DARPA: Past, Current, and Future," paper presented to the Panel on Energy and Power Materials of the Committee on Materials Research for Defense After Next, National Research Council, Irvine, CA, October 1 1, 2001. Cones, E., "Sub-Watt Power Using an Integrated Fuel Processor and Fuel Cell," paper presented at IMRET 5 2001, International Conference on Microreaction Technology, Strasbourg, France, May 2001.
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While the panel did not have sufficient resources to explore this class of nuclear power sources, it did review earlier studies (NRC, 1997, 1999) and other information that suggests that this area should be explored.
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Because major improvements in armor materials and designs may be classified, highly promising existing and developmental materials and designs may have been omitted in this study, which is limited to unclassified sources. Lightweight Armor Three classes of nonstructural armor were considered by the panel: soft (fabric)
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Energy and Power Materials low-velocity ball rounds is the best understood from a theoretical basis. Cunniff (1 999a)
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. Armor Materials Research Needs: Summary Progress in fibers will lead to sizable improvements in soft armor only if DoD takes the initiative to fund new fiber development.
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The committee's conclusion was that, although new approaches to energy harvesting (e.g., photovoltaics) will be combined with increasing use of fuel cells, existing infrastructure makes it likely that current fuels (e.g., JP-8, diesel)
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New synthetic methodologies that allow for architectural control of fuel cell electrodes at the nanoscale could enhance reaction kinetics by dramatically increasing electrode surface area and restrict) ng reactions to confi ned regions.
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The largest subarea that can potentially benefit is materials for electrochemical energy storage and conversion for use in batteries, electrochemical capacitors, fuel cells, and fuel reforming. As an example, high-surface-area battery electrodes made using a one-step process may allow full exploitation of the material's possibilities.
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From page 90... ...
The latter is particularly important in those cases where there are few signposts to promising materials, such as fuel cell electrocatalysts, or where it appears desirable to map out possible limits on the material properties of a family of compounds. DoD is already using these tools effectively.
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For example, a system (e.g., a fuel cell) is a collection of interdependent components (e.g., anode, cathode, electrolyte)
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From page 92... ...
P 137 in Proceedings of New Materials for Batteries and Fuel Cells, San Francisco, CA, D.H.
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From page 93... ...
P 1 in Proceedings of Materials for Electrochemical Energy Storage and Conversion IIBatteries, Capacitors and Fuel Cells, Boston, MA, D.S.
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