Meeting the Energy Needs of Future Warriors (2004) / Chapter Skim
Currently Skimming:
Appendix D: Source Technologies
Appendix D: Source Technologies
Pages 88-114
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 88... ...
The military uses Li/SO2 batteries for many applications, specifically in the BA 5590, which is the workhorse of soldier electronics. BATTERIES These have a theoretical voltage of 3.1, a working voltage of Batteries are electrochemical devices that convert the 2.8, and a practical energy density of 170 Wh/kg.
|
From page 89... ...
workable systems. System-specific energy.
|
From page 90... ...
x has higher theoretical specific energy vs.
|
From page 91... ...
Polyplus 1 Ah cells aThe energy density and specific energy values are based on the power density and specific power values, respectively. high specific energy at low to medium powers.
|
From page 92... ...
Li polymer cells have performance similar to that of the Li ion cell, with 4M + nO2 + 2nH2O 4M(OH) n specific energy values up to about 150 Wh/kg and 300 Wh/L for 20°C to +60°C, and have been recently introduced to M + nO2 MO2n the commercial market.5 The nickel metal hydride, or MH/NiOOH, cell has where M is the metal and n depends on the valence change become very popular for many consumer applications, for the oxidation of the metal.
|
From page 93... ...
Li + H2O LiOH + /2 H2 1 Magnesium has a specific energy of 6,800 Wh/kg, assuming a theoretical cell voltage of 3.1 in Mg/air cells, Besides the undesirable high reactivity of Li with water, the although the actual cell voltage is about 1.6 in practice. In kinetics of oxygen diffusion through the cathode also limits alkaline electrolyte, the Mg is passivated by the formation of the Li/air cells, although recent efforts in Li/oxygen Mg(OH)
|
From page 94... ...
FUEL CELLS ELECTROCHEMICAL CAPACITORS Fuel cells are currently under intense research and There has been a surge of interest in electrochemical development as power sources for a range of applications, capacitors (supercapacitors or ultracapacitors, abbreviated including portable power, automobiles, and large-scale EC) , which produce one or two orders of magnitude more power plants.
|
From page 95... ...
Moderate or good energy density, depending on equivalent weights and electrode potentials of active materials. Good power density.
|
From page 96... ...
The specific energy and energy density of technology and a supporting industrial base. various fuels are listed in Table D-8.
|
From page 97... ...
and 1 atm. highest specific energy of all fuels, but it also has the lowest usually a perfluorosulfonic membrane (e.g., DuPont's energy density.
|
From page 98... ...
98 Air Inlet Cooling Air Cooling Exhaust Fan Cooling Cell Purge Vent 2 Stack H Fuel Aerospace. Ball Air/Water Vent SOURCE: Oxidant Module Purge Filter system.
|
From page 99... ...
are considered active heat must be applied to remove the hydrogen as boil-off gas. TABLE D-9 Dependence of Select Hydrogen Sources on Fuel Cell Resources Specific Energy Ideal (Wh/kg)
|
From page 100... ...
, the and must be inspected and recertified regularly. As in the thermal decomposition of light metal hydrides such as AlH3, case of compressed hydrogen, the actual weight percent of and the cracking of ammonia all require some energy from hydrogen stored will decrease with the size of the hydrogen either the fuel cell or the combustion of hydrogen.
|
From page 101... ...
Membranes that are stable in high methanol concen trations and exhibit lower crossover will also allow the Direct Methanol Fuel Cells system to be stored at lower temperature without concern for DMFC technology avoids problems with fuel storage, freezing of the fuel cell stack (a 5 molar solution of MeOH because the catalysts at the fuel cell anode can directly freezes at about 10°C, while an 8 molar solution freezes at oxidize liquid methanol, eliminating the need for compli- 21°C)
|
From page 102... ...
This DMFC-20 exhibits a specific energy yield approaching 10Polyfuel demonstrated a working prototype to committee member Jeff 2.0 Wh/g MeOH (0.33 (S)
|
From page 103... ...
. SOURCE: Ball Aerospace.
|
From page 104... ...
Hence the specific energy yield of the <5-W DMFCs is typically less than 1.2 Wh/g when pure 2CO = C(s) + CO2 methanol is the fuel and less than 0.6 Wh/g when premixed methanol is the fuel.
|
From page 105... ...
MEMS fuel-cell frame and traces of silicon from the fuel Metal dusting of stainless steels, or corrosion of Fe- and reformer. Ni-containing materials due to the formation of metal Several 20-W SOFC designs are under development for carbides, may also be a failure mechanism in compact the DARPA Palm Power program, and it is apparent that the SOFCs operating on logistics fuels, as it can occur in gas designs and beliefs that are upheld for large terrestrial sysstreams rich in carbon monoxide and hydrogen between tems apply differently to these mesoscale systems.
|
From page 106... ...
With improvements in the BOP and reduce the weight of the stack. A hydrocarbon-fueled 2-kW systems engineering, AMI expects to build stacks with a SOFC is commercially available from Acumentrics,14 but it rated specific energy of 1,000 Wh/kg for a 72-hr mission and has not been optimized for compactness.
|
From page 107... ...
weight aircraft alternators have specific power of about 200 W/kg for units in the 500-W class. Both types can be over 80 percent efficient in converting kinetic energy to electricity.
|
From page 108... ...
. According to the formulas ments in component efficiencies that are required to make at the end of Appendix C and Figure C-4, any 5 percent the microturbine generator a viable power source are likely efficient system will have a specific energy of less than 600 to be very expensive and to have a limited chance of success.
|
From page 109... ...
did not When coupled to a linear alternator, the device may use flex consider external combustion engines as viable candidates bearings or gas bearings, both of which allow the engine to for soldier power owing to their low specific power, and to be hermetically sealed into one compact unit with the fewest date, their primary commercial and military application is possible moving parts, none of which are in physical for cryogenic coolers. contact.
|
From page 110... ...
power systems not viable for soldier Figure D-9 shows a 1-kW Stirling engine recently pur power applications owing to their inherently low conversion chased by Auburn University as part of its hybrid electric efficiency and low specific power. TE devices utilize program for silent watch applications.
|
From page 111... ...
, as Thermophotovoltaics, TPV, was considered a potential reported by Nature, and is developing a small thermoelectric energy conversion mechanism for the soldier in Energysystem that uses JP-8 as a fuel under the DARPA Palm Efficient Technologies (NRC, 1997)
|
From page 112... ...
2004. Microtubule solid oxide fuel cells.
|
From page 113... ...
1993. Ceramic fuel cells.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.