Unmanned Systems Integrated Roadmap FY2011-2036 - Defense ...

9.4.2 Power
Unmanned Systems Integrated Roadmap FY2011-2036
Figure 20. Fuel Cell Efficiency.
Power sources are critical enablers for all of the desired unmanned systems capabilities.
Improved power sources will have to be compact, lightweight, and reliable; provide enough
power for the desired mission; and satisfy a full range of environmental and safety requirements.
Design of power sources must be optimized for specific platforms and use profiles. Depending
on the platform and mission requirements, applicable technologies may include energy
harvesting (e.g., photovoltaic), electrical energy storage devices, fuel cells, and generators. It
may be attractive to hybridize two or more of these technologies depending on the expected use
profile. To implement these hybrid systems, the development of the proper control schemes must
also be conducted. Recently, there has been a lot of effort invested to improve the power density
of power generation systems with very good progress, but work is still needed to improve other
power systems critical metrics. Some of these needed metrics and improvements are life,
reliability, efficiency, optimized performance over varying engine speed, wide temperature
range, production variability, control strategy, and parameters that capture the fact that
unmanned subsystems typically do not have the redundancy of manned systems. Early scrutiny
of the vehicle design will lead to improved power management. Form factor, materials,
autonomy in sensor usage and route planning, and consideration of the undersea physical
environment will minimize the energy demands and give back energy to extend the endurance or
meet other mission goals.
Advances in mission equipment are providing much greater capabilities, but at a cost of
greater demand for electric power, which results in greater power extraction from the engine.
Power-sharing architectures allow for tailoring the source of power generation to minimize the
cost in fuel burn. For example, if low-pressure (LP) power extraction is more economical than
high-pressure (HP) power extraction, then the SSPCs can be turned on to power the bus that was
previously powered by the HP-driven generator. Engine power extraction technologies related to
power sharing between the HP spool and LP spool promise to provide significant benefit to
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