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Suggested Citation:"Executive Summary." National Research Council. 2002. Combat Hybrid Power System Component Technologies: Technical Challenges and Research Priorities. Washington, DC: The National Academies Press. doi: 10.17226/10595.
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Executive Summary

The U.S. Army envisions that many of its future combat vehicles will feature a hybrid electric power system containing a diesel or turbine generator that will supply electric power to operate the vehicle subsystems, including electric drive and weapons systems. In military hybrids, pulsed power and continuous power must operate together without interference. Pulsed power is required for high-power lasers, an electrothermal chemical (ETC) gun, high-power microwave weapons, electromagnetic armor, and other systems. Elements of the continuous power system include prime power (diesel or turbine), generator, motors, converters, power distribution systems, storage, fault protection, safety systems, and auxiliary power connections.

While some of the technologies required to support combat hybrid vehicle power systems are in hand, many technical challenges remain. In 1997, the Defense Advanced Research Projects Agency (DARPA) initiated the Combat Hybrid Power System (CHPS) program, whose goal is to develop and test a full-scale hybrid electric power system for advanced combat vehicles. To achieve that goal, the program has developed a 100 percent hardware-in-the-loop System Integration Laboratory (SIL)—a reconfigurable laboratory using state-of-the-art hardware and software.

In support of this effort, DARPA requested that the National Research Council (NRC) convene a committee of experts to undertake the following task:

Address the key issues for emerging technologies in the development of the combat hybrid power system components. The technologies to be addressed include permanent magnet technology for hub motors, Li-ion batteries, and high-temperature, wideband gap materials. Other such emerging technologies may also be addressed.

On August 26 and 27, 2002, the NRC Committee on Assessment of Combat Hybrid Power Systems convened a data-gathering workshop in San Jose, California. The committee targeted the three emerging technology areas specified in the statement of work:

  1. Advanced electric motor drives and power electronics,

  2. Battery technologies for military electric and hybrid vehicle applications, and

  3. High-temperature, wideband gap materials for high-power electrical systems.

In addition, the committee determined that three additional emerging technologies should also be addressed:

  1. High-power switching technologies,

  2. Capacitor technologies, and

  3. Computer simulation for storage system design and integration.

Suggested Citation:"Executive Summary." National Research Council. 2002. Combat Hybrid Power System Component Technologies: Technical Challenges and Research Priorities. Washington, DC: The National Academies Press. doi: 10.17226/10595.
×

Tables ES-1 through ES-6 summarize the results of the committee’s analysis of the technical challenges, performance metrics, and research priorities associated with these six areas.

TABLE ES-1 Advanced Electric Motor Drives and Power Electronics

System/Component

Technical Challenge

Performance Metric

R&D Priorities

Electric motors for traction

Simulation of drive cycles/mission profiles to establish torque-speed requirements of the electrical drive

Changes in component (e.g., motor) design parameters quantitatively linked to changes in overall system performance

Expansion of current research to validate models and link motor design programs with power electronics and drive simulation programs

 

Optimizing auxiliary power unit, battery, and other energy storage device characteristics to meet the torque-speed requirements of the drive

 

 

Motor and inverter technology development to meet wide constant horsepower speed range without impacting the size of inverters

 

 

Comparison of various power train configurations, e.g., wheel motors, axle motors with and without gearboxes and transmissions

 

 

”Apple to apple” comparison of internal permanent magnet motors and inverters with induction and other motors and inverters for traction drive

 

Suggested Citation:"Executive Summary." National Research Council. 2002. Combat Hybrid Power System Component Technologies: Technical Challenges and Research Priorities. Washington, DC: The National Academies Press. doi: 10.17226/10595.
×

Materials for electric motors

Electrical losses in copper windings and iron in magnetic materials

Low loss even at high frequencies

Low loss materials that can be readily manufactured in laminar form

 

Buried permanent magnet rotors for large machines

Retention of remnant flux density and energy product characteristics

Techniques for injecting magnetic materials into the rotors, and curing and magnetizing them on-site

Power devices and inverters

Inverters that operate with high efficiency at higher power

High-current, high-voltage switching characteristics

Development of wideband gap materials such as SiC

 

Improving device cooling

 

Development of thermal management systems with phase transition and other materials to remove heat quickly from the power devices and inverters and improve transient performance

 

Reducing electromagnetic interference (EMI)

 

Integration of SiC diodes with insulated gate bipolar transistor hard switched inverters to reduce reverse recovery transients to yield low EMI and high efficiency comparable to soft switching inverters

DC bus capacitors

Keeping the voltage ripple within specified limits

Size, efficiency, operating temperature, and ripple current carrying capacity

Fundamental research on materials to meet these requirements

DC/DC converters

High ratio voltage conversion at high power

Performance at high power, EMI/electromagnetic compliance shielding, and packaging size

Design tools for optimizing the combination of devices required and other characteristics, e.g., switching frequency

Integrated thermal management systems

Adequate cooling for both motors and power electronics

Cooling efficiency, packaging size

Development of high thermal conductivity materials such as graphite foams and silicon carbide, in combination with phase transition fluids

Suggested Citation:"Executive Summary." National Research Council. 2002. Combat Hybrid Power System Component Technologies: Technical Challenges and Research Priorities. Washington, DC: The National Academies Press. doi: 10.17226/10595.
×

TABLE ES-2 Battery Technologies

System/Component

Technical Challenge

Performance Metric

R&D Priorities

Advanced battery concepts

Validation of batteries in vehicle applications

Specific power

Specific energy

Triple the power and energy with nanomaterials technology and new chemistries

 

Safety

 

Increased safety (eliminate flammable materials; better packing for isolation, containment, venting; thermally stable materials; diagnostics/ prognostics integrated in pack; eliminate ground fault and arcing; improved materials that reduce gassing)

 

Battery management (state of health, state of charge, power availability, life prediction, temperature management, diagnostics, and prognostics)

 

Electrode/electrolyte interface

Voltage drop caused by limited chemical reactivity at the interface

 

Advanced electrode/electrolyte materials with high surface reactivity

 

Increased electrode surface area by increased matrix porosity or perhaps application of nanomaterials

Electrolyte

Voltage drop caused by mass transfer overpotential

 

Electrolytes with high concentrations of reactant species and low ion transfer resistance

Connectors and terminals

Ohmic resistance of materials

Minimized resistance

Low-resistance materials

Suggested Citation:"Executive Summary." National Research Council. 2002. Combat Hybrid Power System Component Technologies: Technical Challenges and Research Priorities. Washington, DC: The National Academies Press. doi: 10.17226/10595.
×

TABLE ES-3 High-temperature, Wideband Gap (WBG) Materials

System/Component

Technical Challenge

Performance Metric

R&D Priorities

Bulk SiC

Improvement of material quality and substrate diameter

Low defect density

Processing to exploit advantages of 4H-SiC (1120) a-plane crystal orientation

Metal-semiconductor contacts

Improve ohmic contact fabrication processes

Contact stability under extreme conditions

Improvement of science and technology of implantation, implantation activation, and metal-semiconductor metallurgy in wideband gap devices and materials

Device packaging

Development of packaging that can accommodate the high-temperature, high-power characteristics of wideband gap devices while providing high rates of heat removal

Stability, heat removal rate

For SiC devices, development of processes for high-resistivity poly SiC with a matched coefficient of thermal expansion

Bulk GaN and AlN

Improvement of substrate material quality

Low defect density

Fundamental processing research to control defects in bulk GaN and AlN

Suggested Citation:"Executive Summary." National Research Council. 2002. Combat Hybrid Power System Component Technologies: Technical Challenges and Research Priorities. Washington, DC: The National Academies Press. doi: 10.17226/10595.
×

TABLE ES-4 High-power Switching Technologies

System/Component

Technical Challenge

Performance Metrics

R&D Priorities

Power converters

Higher power densities, switching frequencies, and greater reliability

High power density

Manufacturing simplicity

Processes for integration of distributed components with active devices

 

Reduced design and verification cycle times

Design tools for three-dimensional thermal management, packaging, system design, and manufacturability

Power electronics for pulse energy storage

Effective decoupling of pulse loads from the power distribution system

High current density

High level of decoupling

Development of storage system interfaces with bimodal (slow and fast) power transfer capability

 

Development of interfaces with flexibility to tailor output voltage/current waveforms to requirements of weapons systems

Power distribution network

Mission-critical systems that degrade gracefully under fault conditions

Level of functionality under unplanned faults and component failures

Fundamental understanding of factors affecting system stability

 

Dynamic models of power converter interactions at the DC bus

 

Controls that mitigate instabilities on the DC bus

Suggested Citation:"Executive Summary." National Research Council. 2002. Combat Hybrid Power System Component Technologies: Technical Challenges and Research Priorities. Washington, DC: The National Academies Press. doi: 10.17226/10595.
×

TABLE ES-5 Capacitor Technologies

Component/System

Technical Challenges

Performance Metrics

R&D Priorities

Polymer film capacitors

Films with improved dielectric properties

Dielectric constant

Dielectric withstand

New polymer films with increased dielectric constant and dielectric withstand similar to biaxially oriented polypropylene

 

Filled polymer films: either inorganic filler to improve dielectric strength, high dielectric constant filler to increase dielectric constant, or high dielectric polymer filler to reduce volume within the film, resulting in a combination of increased operating field and increased dielectric constant

Ceramic capacitors

Lack of understanding of aging/failure mechanisms

 

Research on aging/failure mechanisms under high-temperature, high-field conditions

 

Dielectrics with improved properties

Dielectric constant

Dielectric withstand

Research to improve high energy density, high-temperature ceramic dielectrics

 

Improved operating electric field

Operating field

Ceramic-polymer composites or other technologies that reduce the free volume within the ceramic

Double layer capacitors

Lack of understanding of aging and degradation processes at high temperature

 

Investigate role of impurities in the carbon electrodes and interactions among the electrodes, electrolyte, and separator

 

Improvement of properties of electrolytes, increase in cell voltage, and reduction of equivalent series resistance

Cell voltage equivalent series resistance

 

 

Predictability of performance over time

Stability of properties

Materials and processes that achieve reproducible cell characteristics that are stable over time, or age uniformly

Suggested Citation:"Executive Summary." National Research Council. 2002. Combat Hybrid Power System Component Technologies: Technical Challenges and Research Priorities. Washington, DC: The National Academies Press. doi: 10.17226/10595.
×

 

over time

 

Reduction of current densities

Effective electrode surface area

Research into materials and manufacturing processes that increase the effective surface area of electrodes

TABLE ES-6 Computer Simulation for the Design of Storage Systems and Components

Component/System

Technical Challenges

Performance Metrics

R&D Priorities

CHPSET tool set

Validation against available hardware

Accurate simulation of hardware performance

Validation using data from the Systems Integration Laboratory and possibly hybrid HMMWV and Scout vehicles

Cooling airflow

Modeling cooling effectiveness and cooling airflow, especially through combat grillwork

Resemblance of emulation hardware to notional, demonstrator-level hardware

Emulation of environmental factors

Emulation using grillwork hardware

Linkage of CHPSET codes

Effective information transfer between system designers and component designers

Fidelity of vendor-supplied models

Development of a common, expanded solid model database

 

Difficulty of modeling hardware provided by vendors

Compatibility of models with CHPSET tools

Vendors encouraged to provide solid models of their hardware, validated at the numeric, component, and system levels

Incorporation of CHPSET tools in a virtual battlefield environment

Understanding of power management during the various modes of operation

Successful integration of a CHPSET model into a higher-level simulation

Integration of CHPSET models into the Joint Modeling and Simulation System (JMASS)

Consideration of environmental factors in CHPSET

Need for realistic mission-related resistance data

Successful incorporation of NATO Reference Mobility Model (NRMM) data into CHPSET

Explore use of NRMM and related software tools such as a route analysis tool kit to generate input data for CHPSET

User options in CHPSET code

Need for comparative analysis capability involving other vehicle options

Executable code user friendliness

Expand executable CHPSET code to include additional user options such as parallel hybrid and conventional vehicles, with appropriate user documentation

Suggested Citation:"Executive Summary." National Research Council. 2002. Combat Hybrid Power System Component Technologies: Technical Challenges and Research Priorities. Washington, DC: The National Academies Press. doi: 10.17226/10595.
×

Incorporation of CHPSET codes into failure modes and effects analysis (FMEA)

Enhancement of system reliability and mitigation of effect of component failures

Risk priority numbers

Identification of potential failure modes

Design-specific, skid-mounted hardware emulators of Future Combat System

Enhancement of emulator fidelity

Resemblance of emulation hardware to notional, demonstrator-level hardware

Development of design specifics for notional, demonstrator-level systems

Suggested Citation:"Executive Summary." National Research Council. 2002. Combat Hybrid Power System Component Technologies: Technical Challenges and Research Priorities. Washington, DC: The National Academies Press. doi: 10.17226/10595.
×
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Suggested Citation:"Executive Summary." National Research Council. 2002. Combat Hybrid Power System Component Technologies: Technical Challenges and Research Priorities. Washington, DC: The National Academies Press. doi: 10.17226/10595.
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Suggested Citation:"Executive Summary." National Research Council. 2002. Combat Hybrid Power System Component Technologies: Technical Challenges and Research Priorities. Washington, DC: The National Academies Press. doi: 10.17226/10595.
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Suggested Citation:"Executive Summary." National Research Council. 2002. Combat Hybrid Power System Component Technologies: Technical Challenges and Research Priorities. Washington, DC: The National Academies Press. doi: 10.17226/10595.
×
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Suggested Citation:"Executive Summary." National Research Council. 2002. Combat Hybrid Power System Component Technologies: Technical Challenges and Research Priorities. Washington, DC: The National Academies Press. doi: 10.17226/10595.
×
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Suggested Citation:"Executive Summary." National Research Council. 2002. Combat Hybrid Power System Component Technologies: Technical Challenges and Research Priorities. Washington, DC: The National Academies Press. doi: 10.17226/10595.
×
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Suggested Citation:"Executive Summary." National Research Council. 2002. Combat Hybrid Power System Component Technologies: Technical Challenges and Research Priorities. Washington, DC: The National Academies Press. doi: 10.17226/10595.
×
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Suggested Citation:"Executive Summary." National Research Council. 2002. Combat Hybrid Power System Component Technologies: Technical Challenges and Research Priorities. Washington, DC: The National Academies Press. doi: 10.17226/10595.
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Suggested Citation:"Executive Summary." National Research Council. 2002. Combat Hybrid Power System Component Technologies: Technical Challenges and Research Priorities. Washington, DC: The National Academies Press. doi: 10.17226/10595.
×
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Suggested Citation:"Executive Summary." National Research Council. 2002. Combat Hybrid Power System Component Technologies: Technical Challenges and Research Priorities. Washington, DC: The National Academies Press. doi: 10.17226/10595.
×
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Suggested Citation:"Executive Summary." National Research Council. 2002. Combat Hybrid Power System Component Technologies: Technical Challenges and Research Priorities. Washington, DC: The National Academies Press. doi: 10.17226/10595.
×
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This book provides the detail from the NRC Committee on Assessment of Combat Hybrid Power Systems. This committee targeted three emerging technology areas: advanced electric motor drives and power electronics, battery technologies for military electric and hybrid vehicle applications, and high temperature wideband gap materials for high-power electrical systems. This committee also addressed three additional emerging technologies: high power switching technologies, capacitor technologies and computer simulation for storage system design and integration.

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