Research Papers

System Architectures for Solid Oxide Fuel Cell-Based Auxiliary Power Units in Future Commercial Aircraft Applications

[+] Author and Article Information
R. J. Braun1

Division of Engineering, Colorado School of Mines, Golden, CO 80401rbraun@mines.edu

M. Gummalla, J. Yamanis

 United Technologies Research Center, E. Hartford, CT 06108


Corresponding author.

J. Fuel Cell Sci. Technol 6(3), 031015 (May 15, 2009) (10 pages) doi:10.1115/1.3008037 History: Received July 16, 2007; Revised May 20, 2008; Published May 15, 2009

Recent advancements in fuel cell technology through the auspices of the Department of Energy, the National Aeronautics and Space Administration, and industry partners have set the stage for the use of solid oxide fuel cell (SOFC) power generation systems in aircraft applications. Conventional gas turbine auxiliary power units (APUs) account for 20% of airport ground-based emissions. Alleviating airport ground emissions will continue to be a challenge with increased air travel unless new technology is introduced. Mission fuel burn and emissions can be significantly reduced through optimal systems integration of aircraft and SOFC subsystems. This study examines the potential total aircraft mission benefits of tightly integrating SOFC hybrids with aircraft subsystems using United Technologies Corporation Integrated Total Aircraft Power Systems proprietary methodologies. Several system concepts for optimal integration of the SOFC stack with aircraft subsystems are presented and analyzed in terms of mission fuel burn for technologies commensurate with 2015 entry into service. The performance of various hybrid SOFC-APU system architectures is compared against an advanced gas turbine-based APU system. In addition to the merits of different system architectures, optimal SOFC system parameter selection is discussed. The results of the study indicate that despite the lower power density of SOFC-based APU systems, significant aircraft fuel burn (5–7%) and emission reductions (up to 70%) are possible. The majority of the fuel burn savings are realized during aircraft ground operations rather than in-flight mission segments due to the greater efficiency difference between the SOFC system and the advanced APU technology.

Copyright © 2009 by American Society of Mechanical Engineers
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Figure 1

Schematic baseline engine and power system architecture

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Figure 2

Baseline APU electrical loads for ground operation

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Figure 3

Baseline electrical loads for climb/cruise/descent mission

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Figure 4

Schematic of aircraft systems with SOFC-APU Architecture A

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Figure 5

Process schematic of SOFC-APU

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Figure 6

2015 weight distribution goals of SOFC-APU system—Architecture A

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Figure 7

System efficiency and weight versus system operating pressure

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Figure 8

System efficiency and FB objective versus system pressure

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Figure 9

System efficiency and weight versus design cell voltage

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Figure 10

Effect of stack temperature on system efficiency and parasitic power

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Figure 11

System efficiency and parasitic power versus cathode air temperature rise

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Figure 12

System efficiency and weight versus fuel utilization

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Figure 13

Turbine power fraction and fuel burn objective versus fuel utilization

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Figure 14

Fuel savings for Architecture A during ground operations

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Figure 15

Architecture A fuel burn savings during climb-cruise-descent

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Figure 18

Year 2015 EIS SOFC system weight goals and break even points (no fuel burn savings)

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Figure 20

Total aircraft emissions for entire mission relative to baseline for (a) engine operations and (b) LTO cycle

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Figure 16

Architecture B: Benefits of included concepts achieve 6.7% overall fuel burn savings

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Figure 17

Financial impact of fuel burn savings of architectures investigated

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Figure 19

Emission/emission reductions for Architectures A and B during (a) ground operations and (b) flight operations



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