Feasibility Study on SOFC-Stirling Engine Combined System.

Takahashi, Sanyo; Kobayashi, Nariyoshi; Iki, Norihiko; Furutani, Hirohide; Yamashita, Ikuo

doi:10.1299/kikaib.70.192

Cited by 6 publications

(3 citation statements)

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“…In addition, oper ating temperature of a Stirling engine is near the exhaust tempera ture of an SOFC. Takahashi et al [1] investigated the performance of a combined SOFC-Stirling engine system fueled with methane by means of thermodynamic system modeling. The results showed a 10% higher efficiency for the combined system at low excess air ratio (<2.0), compared with SOFC systems alone.…”

Section: Developm Ent Of Anode Gas Recycle System Using Ejector For 1mentioning

confidence: 99%

Development of Anode Gas Recycle System Using Ejector for 1 kW Solid Oxide Fuel Cell

Baba

Kobayashi

Takahashi

et al. 2014

Journal of Engineering for Gas Turbines and Power

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An anode gas recycle (AGR) system using an ejector fo r 1 kW solid oxide fuel cells (SOFCs) was developed to increase the electrical efficiency o f combined power genera tion. We call this an AGR-SOFC. The effects o f recirculation ratio, externally steam feed rate, and fuel utilization were determined experimentally on the AGR-SOFC perform ance (i.e., output power, stack temperature, and gas composition) using a variable flow ejector and a recirculation ratio o f 0. 55-0.62, overall fuel utilization o f 0.720-84, and steam feed rate o f 0-1.5 glmin. A quadrupole mass spectrometer was used to identify the recirculation ratio, the gas composition o f reformed gas at the AGR-SOFC inlet, and that o f the recycle gas at the outlet. Compared to one-path SOFC systems, i.e., without an AGR, the AGR-SOFC was stable and generated about 15 W more electricity when the overall fuel utilization was 0.84 and the recirculation ratio was 0.622 with no steam sup ply. This improved performance was due to the reduced H20 concentration in the anodic gas. In addition, although the recirculation ratio did not affect the AGR-SOFC perform ance, a high recirculation ratio can provide steam produced via the electrochemical reaction to the injected fuel fo r the steam reforming process.In tro d u ctio n SOFCs applied to stationary power generation systems have two major advantages: (i) Highest efficiency among all fuel cells, (ii) lower cost by using nonplatinum catalysts. Furthermore, micro combined heat and power (mCHP) systems based on SOFCs are being actively researched to obtain an even higher efficiency by utilizing the high temperature exhaust gas (>700 °C) from the SOFC itself. Unlike gas turbine engines, Stirling engines are external combustion engines that can be combined with SOFCs at normal pressures with practical efficiencies of roughly 20% for small scale power generation about 1 kW class. In addition, oper ating temperature of a Stirling engine is near the exhaust tempera ture of an SOFC. Takahashi et al.[1] investigated the performance of a combined SOFC-Stirling engine system fueled with methane by means of thermodynamic system modeling. The results showed a 10% higher efficiency for the combined system at low excess air ratio (<2.0), compared with SOFC systems alone. They also stated the need to develop a steam reforming sys tem with an anode gas recirculation to improve the electrical effi ciency of combined power generation.Steam is required to convert hydrocarbon fuel to hydrogen and carbon monoxide. This method is called steam reforming process.Hydrogen and carbon monoxide are produced from methane under high temperature conditions via steam reforming reaction and water-gas shift reaction to prevent carbon deposition on the anode. Assuming that the inflow rate of the steam is 2.5 times higher than that of the fed methane fuel, 175kJ/mol of methane must be provided to convert water at 25 °C to steam at 800 °C. In other words, about 20% of the enthalpy of the methane combus tion (890kJ/mol) is consumed in the produc...

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Section: Developm Ent Of Anode Gas Recycle System Using Ejector For 1mentioning

confidence: 99%

Development of Anode Gas Recycle System Using Ejector for 1 kW Solid Oxide Fuel Cell

Baba

Kobayashi

Takahashi

et al. 2014

Journal of Engineering for Gas Turbines and Power

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“…Hybrid systems with SOFCs and SEs have also been investigated [7] [8]. The efficiency of SOFCs ranges between 40% and 60% for converting fuel energy into electricity; a conservative efficiency number reported by fuel cell agencies is 47% [9].…”

Section: Background and Motivationmentioning

confidence: 99%

Analysis of hybrid fuel-cell/stirling-engine systems for domestic combined heat and power

Smith¹,

Lee

Newman³

2012

2012 IEEE Energytech

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“…The presence of steam enables the carbon gasification reaction from carbon atoms to carbon monoxide to proceed rapidly. Takahashi et al (2004) reported that the overall efficiency of an SOFC hybrid system, including bottoming engines, can be improved with such an approach.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of solid oxide fuel cell performance with anode recirculation using variable flow ejector at rated conditions

Baba

Takahashi

Kobayashi

et al. 2015

Mechanical Engineering Journal

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An anode gas recycle (AGR) system that uses an ejector for a 1 kW solid oxide fuel cell (SOFC) was developed to increase the electrical efficiency of combined power generation. The effects of anodic recirculation on the SOFC performance were determined experimentally with a variable flow ejector at a fuel utilization of 0.80 to 0.87 and a steam feed rate of 0 to 1.5 g/min. A quadrupole mass spectrometer was used to identify the recirculation ratio, the gas composition of reformed gas at the SOFC inlet, and that of the recycle gas at the recycle plenum located downstream of the SOFC. The recirculation ratio could be changed from 0.67 to 0.71 by moving the needle inside the ejector nozzle, and thus the SOFC showed stable performance with no steam supply, due to the large recirculation ratio of steam produced via the electrochemical reaction that was supplied to the injected fuel for the steam reforming process. The results indicate a slight decline in output power with an increase in the recirculation ratio. In addition, the fuel utilization limitation for SOFC operation is estimated to be as much as that for a one-path SOFC system without AGR to avoid a local lack of hydrogen as fuel.

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Feasibility Study on SOFC-Stirling Engine Combined System.

Cited by 6 publications

References 0 publications

Development of Anode Gas Recycle System Using Ejector for 1 kW Solid Oxide Fuel Cell

Development of Anode Gas Recycle System Using Ejector for 1 kW Solid Oxide Fuel Cell

Analysis of hybrid fuel-cell/stirling-engine systems for domestic combined heat and power

Evaluation of solid oxide fuel cell performance with anode recirculation using variable flow ejector at rated conditions

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