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Research Paper

Development of a Hybrid System of Molten Carbonate Fuel Cell and Homogeneous Charge Compression Ignition Engine for Distributed Power Generation

[+] Author and Article Information
Han Ho Song

e-mail: hhsong@snu.ac.kr

Seung Jin Song

School of Mechanical and
Aerospace Engineering,
Seoul National University,
Gwanak-gu, Seoul, South Korea

Sang Gyu Kang

Korea Institute of Machinery and Materials,
104 Sinseongno,
Yuseong-Gu, Daejon, South Korea

One may consider re-equilibration of the mixture composition and accompanying temperature change by applying WGSR in the nonisothermal component, but the overall result would change little if the size of the segment is chosen to be sufficiently small.

The choice of fuel utilization factor of 0.7 is to ensure the maximum fuel utilization in the fuel cell without sacrificing the efficiency due to increased overvoltage from depletion of fuel concentration in the latter part of the fuel cell.

By omitting the pumping losses from gas exchange processes, it may lead to slight overestimation of work output and efficiency of the engine cycle, but the present results are still reflecting on general trends as can be found in typical HCCI engine operations.

The lean flammability limits for CO and H2 are equivalence ratios of 0.34 and 0.14, respectively. For instance, the equivalence ratios of CO and H2 for the engine inlet at design point operation (referring to state 8 in Table 6) are 0.31 and 0.04, respectively, both of which are under the flammability limit.

1Corresponding author.

Contributed by the Advanced Energy Systems Division of ASME for publication in the JOURNAL OF FUEL CELL SCIENCE AND TECHNOLOGY. Manuscript received November 19, 2012; final manuscript received July 10, 2013; published online September 13, 2013. Assoc. Editor: Umberto Desideri.

J. Fuel Cell Sci. Technol 10(6), 061002 (Sep 13, 2013) (11 pages) Paper No: FC-12-1116; doi: 10.1115/1.4025126 History: Received November 19, 2012; Revised July 10, 2013

A new hybrid system of molten carbonate fuel cell (MCFC) and homogenous charge compression ignition (HCCI) engine is suggested to improve the overall system efficiency and performance. In the proposed system, the catalytic burner in a standalone MCFC system is replaced with the HCCI engine. The HCCI engine is chosen over conventional spark-ignition or compression-ignition engines since it has been demonstrated to operate with highly diluted reactant mixture, which is suitable to run directly with the MCFC anode off-gas. A nonisothermal numerical model that incorporates major fuel cell losses is developed to predict the fuel cell performance. The fuel cell model assumes parallel anode and cathode flow configuration with LiNaCO3 as an electrolyte. It is integrated with an in-house HCCI engine model to investigate the hybrid system performance. At the selected design point operation around 300 kW power output, the maximum hybrid system efficiency is 21.2% (relative) higher than that of a standalone fuel cell system and, thus, achieving around 60% overall, which demonstrates the potential of the suggested hybrid system as a highly-efficient distributed power generation source in the near future.

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References

Figures

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Fig. 1

Species flows in MCFC stack (N2 and H2O omitted at cathode)

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Fig. 2

MCFC stack modeling schematic (a) parallel flows with 25 segments and (b) energy flows within each segment

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Fig. 3

(a) Standalone system (with catalytic burner), (b) hybrid system (with HCCI engine)

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Fig. 4

Change in temperature along fuel cell segments

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Fig. 5

Change in molar flow rates of anode species along fuel cell segments

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Fig. 6

Change in molar flow rates of cathode species along fuel cell segments

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Fig. 7

Temperature profile for HCCI engine at design point operation

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Fig. 8

Pressure profile for HCCI engine at design point operation

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