Meeting the Energy Needs of Future Warriors (2004) / Chapter Skim
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Appendix C: Measures of Performance
Appendix C: Measures of Performance
Pages 80-87
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From page 80... ...
The efficiency of product of current, I, in amperes multiplied by the potential batteries and fuel cells varies with current, so higher current drop across the load, V, in volts: (higher power) from a portable power source results in lower voltages.
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From page 81... ...
for the full packaged system, and that for fuel cells and batteries includes the conversion system, plus the fuel and fuel tank, Efficiency and relevant auxiliary components. Note that a fuel cell or engine with no fuel has no energy, so to accurately estimate The efficiency, , of an energy conversion or storage these terms the amount of fuel consumed over a period of device is a function of both thermodynamics and engineertime must be known.
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From page 82... ...
Of course, G, is 237.1 kJ/mol, so the thermal efficiency of an ideal practical fuel cells do not usually consume all of the fuel fuel cell operating reversibly on pure hydrogen and oxygen supplied, and some leaves the system unreacted. This at standard conditions would be unreacted fuel needs to be taken into account in the effi
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From page 83... ...
The BOP efficiency includes the electrical and thermal Small Engines penalties for the system, among them the electrical power needed to run air and fuel pumps and the thermal losses or For engines, thermal efficiency is the ratio of the net cooling requirements. For low-temperature hydrogen PEM work done, Wnet, to the heat absorbed during a cycle.
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From page 84... ...
For a low-temperature PEM fuel which a power source model or prototype has been demoncell system that produces liquid water, that is run at 0.8 V, strated in a relevant environment. and that has a 95 percent efficient BOP, the overall thermo- Once new power systems such as fuel cells and engines dynamic system efficiency can approach 49 percent.
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From page 85... ...
The basic technological components are in relevant environment integrated with reasonably realistic supporting elements so that the technology can be tested in a simulated environment. Examples include high-fidelity laboratory integration of components.
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From page 86... ...
Device Device Device Device Device 2 144 0.72 0.24 0.144 0.072 0.048 20 1,440 7.2 2.4 1.44 0.72 0.48 100 7,200 36 12 7.2 3.6 2.4 3,000 216,000 1,080 360 216 108 72 NOTE: Calculated weights of devices having specific energies of 200, 600, 1,000, 2,000, and 3,000 Wh/kg at power levels of 2, 20, 100, and 3,000 W aSystem weight includes dry system plus fuel.
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From page 87... ...
(W/kg) Energy Energy Specific Specific System System Maximum Maximum Total System Electrical Efficiency, el Total System Electrical Efficiency, el FIGURE C-5 The maximum allowable system specific energy calculated for (a)
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