Meeting the Energy Needs of Future Warriors (2004) / Chapter Skim
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3 Power System Design
3 Power System Design
Pages 27-36
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From page 27... ...
Real batteries and other real power sources capacity is to measure power demand in major operational do not have such idealized characteristics. Voltage outputs states (standby, idle, peak)
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From page 28... ...
100 80 Battery 60 Efficiency 40 Fuel Cell 20 0 0 20 40 60 80 100 120 Percent of Rated Power FIGURE 3-2 Power source efficiency variation with load. Typical efficiency for DMFC and battery.
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From page 29... ...
For continuous discharge, the There is a slight dependence on the duty cycle, as shown battery specific energy drops from approximately 138 Wh/kg by the family of curves representing intermittent loads with at a specific power of 75 W/kg (point B) to about 90 Wh/kg peaks of 100, 200, and 300 W and duty cycles of 25, 50, and at a specific power of 300 W/kg (point A)
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From page 30... ...
In terms of specific energy, the hybrid had 198 Wh/kg, compared with HYBRID CONCEPTS 126 Wh/kg in the Li ion battery and 177 Wh/kg in the Zn/air A hybrid power source usually combines a high-energy/ battery. low-power component with a low-energy/high-power com- Optimization of a hybrid power source is very complex, ponent.
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From page 31... ...
The direct methanol fuel cell is a device with a high HYBRID ANALYSIS FOR THE SOLDIER SYSTEM specific energy. This is a direct result of the fact that it is a The component electronics of the soldier system will fuel conversion device, and the energy stored in a typical operate on duty cycles that vary significantly in power needs, fuel is at least an order of magnitude higher than the specific so there are varying needs for high specific power and high energy available in batteries of even the most advanced specific energy.
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From page 32... ...
the battery energy for the full-load condition on fuel cell; for the 40 per+ battery hybrid (an extremely high specific energy and low cent load condition in the fuel cell-only case, efficiency specific power battery such as the lithium/(CF) x technology, degrades, so that fuel canisters yield 612.5 Wh (Figure 3-2)
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From page 33... ...
Some units are orientation significantly reduce specific energy of low temperatures significantly dependent. Minimal disposal problems.
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From page 34... ...
Data are based on Ball Aerospace 20-W DMFC and Li ion rechargeable battery and assume fuel cell system dry weight changes directly with peak power required and fuel packaging is the same for both large and small fuel cell. things as a stealth mode to evade detection; and they must be tem only if the energy battery is incapable of meeting the waterproof.
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From page 35... ...
Thus, for a hybrid power Hybrid systems have the ability to improve system source involving Zn/air as one of the components, low tem- power usage by limiting the voltage drops that are imposed peratures might necessitate a larger Zn/air cell in order to on the power supplies for higher current demand duty cycles. achieve the same performance as at room temperature.
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From page 36... ...
The mission includes a modeling effort that predicts power demand by requirements are especially critical when pulsed power is positing mission scenarios, estimating duty cycles, and using needed, in which case a battery + capacitor system might be power sink specification data for all components of the Land useful; also, the duty cycle of the pulsed power must be Warrior soldier system. In addition, the OFW Program plans known.
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