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This project develops tools to assess powering options for soldier system equipment and to evaluate some of those options, yielding quantitative performance measures. Power options that will be evaluated include battery types such as Zn-air, lithium-ion, Li-SO2, Li-MnO, fuel cell types such as PEM and direct methanol, and combinations of any of these power sources with ultracapacitors.
This project encompasses six major tasks, which are detailed as follows.
Develop models of components and systems
This task will develop models of batteries that are widely used by Marine Expeditionary Forces, such as Li-SO2, Li-MnO2, zinc-air, and alkaline. The research will focus on searching the latest developments of related experimental and theoretical results, and characterizing the behaviors of batteries so that models can be built that are accurate over a wide operating range.
Battery model library.
This task will also develop models of fuel cells including Proton Exchange
Membrane (PEM) fuel cells and Direct Methanol Fuel Cells (DMFCs) and models of
the following fuel storage types: hydrogen in metal hydrides, hydrogen as a
compressed gas, and aqueous solution of methanol.
An example of multidisciplinary fuel cell models.
Develop reference mission scenarios and test beds
This task will define standard missions for assessing the powering requirements
of particular equipment sets. These missions will be used to study the
effectiveness of power sharing between devices in ways that will maximize the
utilization of energy carried by the personnel. The significant effort under
this task will be to define particular suites of equipment and usage scenarios
for those equipment suites, in order to form the baseline loads for power source
evaluation.
An example of reference mission scenarios.
Assess effectiveness of hybridization schemes
The objective in making a hybrid power source is to
achieve a source that appears to have only the very best properties of each of
its individual components, and none of the detrimental properties. This task is
to characterize the performance of hybrid power sources as a function of the
duty cycle of the equipment power demand, such as those comprising a zinc-air
battery and an electrochemical double layer capacitor (super capacitor), a
zinc-air battery and a lithium-ion battery, etc.
Examples of hybrid power sources.
Experimental platform for hybrid power sources.
Perform an exergy minimization analysis
Exergy is the latent energy lost from a process by lack
of full process integration or energy recovery. An objective of this task is to
identify specific schemes for energy utilization that maximize the value of
every watt-hour of energy carried while minimizing the risk of being caught
without power when it is needed. Two approaches will be investigated:
intelligently scheduling the usage of specific batteries in specific equipment,
and using secondary cells as temporary energy repositories.
Use secondary cells as temporary energy repositories.
Design an automatic energy optimization capability
This task will design and construct an automatic energy
optimization system. The system will allow a soldier to connect any combination
of primary and secondary batteries together and it will recover (at appropriate
rates, considering urgency and energy efficiency) the energy from partially
depleted primary batteries and consolidate it into one or more secondary
batteries. An objective will be to make this process fully automatic so that no
knowledge is required on the part of the user. (But it may be desirable to allow
the user to select options regarding urgency or how to allocate the recovered
energy.) The energy optimization system will also be capable of acting as a
substitute power source for any one (or possible more) items of equipment,
aggregating the power available from several partially depleted batteries so
that it becomes sufficient to power any item of equipment in the soldier
inventory.
Automatic energy recovery system for partially-drained batteries.
Study the efficacy of fuel-cell powered battery chargers
As mission durations increase, fuel cells begin to make
more sense as main power sources compared to primary batteries. The purpose of
this study is to determine the crossover point in mission characteristics where
it makes sense to carry a fuel cell as a power source for battery recharging.
This work will rely on analytic work, the standard mission scenarios, and
simulation models.
Fuel-cell powered battery charger.
