7

Power Oulput

263 kW (D.C.)

improved 25kW stack in 1994 [1], The D.C. output of the unit stack is 263kW. The two stacks are connected in series to an inverter, and the A.C. output from the inverter is planned to be 500k\V.

Fig. 1 shows the planning structure of the 250kW stack. The stack will consist of six modules and use bellows to compress the modules. Each module will be heated and checked separately at the work shop in Hitachi, and it will be transported after storage. The modules will be stacked to the full height at the testing site.

The l.OOOkW plant is planned to be operated for 5,000 hours, and Hitachi is preparing additional 25kW stack test to confirm the specification and to demonstrate the performance under the equivalent operating condition to that of the plant.

Development for long life stacks

Hitachi has adopted cross flow configuration from the view points of its structural simplicity and reliability of gas scaling between the anode and cathode gas, and Hitachi has developed Multiple Large Capacity Type to disperse hot spot which tends to yield in large stacks [2], Since it was confirmed that the stack operating temperature and ccll voltage drop rate had very close relation after the lOOkVV stack test, research and development to improve the stack temperature distribution are conducted. Fig. 2 shows a basic configuration of an improved flow pattern to moderate the hot spot in cell plane. The structure sets flow distribution in the cathode gas flow path, and introduce more flow at the anode gas inlet side where the current density is high in cross flow type. By this structure, the temperature distribution changes to a linear one in cross flow type, and the original hot spot vanishes.

In the actual application, as shown in Fig. 3, a suitable corrugatcd plate was selected and arranged to achieve an appropriate flow pattern. Fig. 4 shows test results of a stack with the flow regulated type structure. In the figure, the test results are compared to the calculated results at the same condition. The measured values are close to the calculated temperature distribution, and they show that the cathode gas temperature at anode inlet side is lower than that at the anode outlet side. This result shows that the flow pattern is effective for moderating the temperature distributions in cross flow type and a promising structure for longer life slack.

Fig. 1 250kVV Stack Planning Structure

Conclusion

Hitachi, Ltd. is developing 250kW stacks and will complete the installation in 1998. Hitachi, Ltd. is also conducting research and development for long endurance MCFC stacks, and developed effective flow pattern in the field of stack cooling research.

Hitachi, Ltd. will continue to endeavor to develop large MCFC stacks and extend the MCFC stack endurance.

Acknowledgment

This work has conducted under a contract from NEDO (New Energy and Industrial Technology Development Organization) and MCFC Research Association (Technology Research Association for Molten Carbonate Fuel Cell Power Generation System). We appreciate their advice and support.

References

1. T. Kahara et al. "Status of MCFC Cell and Stack Technology at Hitachi", 1994 Fuel Cell Seminar, pp. 222-225, Nov. 1994.

2. T. Kahaia et al. "Status of MCFC Cell and Stack Technology Development at Hitachi", The 2nd International Fuel Cell Conference, pp. 123-126, Feb. 1996.

Cathode gas flow pattern

Cathode gas flow pattern

Fig. 2 Temperature distribution improvement by flow pattern regulated type structure

< Cross Flow Type > < Flow Pattern Regulated Type >

Fig. 2 Temperature distribution improvement by flow pattern regulated type structure

Cathode gas flow pattern (Regulated)

Cathode gas flow pattern (Regulated)

Uniform distribution ^ Anode 9as

JTTTTTTfTTTI

Uniform distribution ^ Anode 9as

Rg. 3 Stmcturc of cathode flow path for flow pattern regulated type

Points :Measured results Lines : Calculated results

Condition

Current density: 90mA/sq. cm

Cathode gas

Cathode gas

^ Anode gas

Temperature distribution in cell plane

0.0 0.2 0.4 0.6 0.8 1.0 Distance from inlet (-)

Temperature rise along the cathode flow

Fig.'4 Test results of the stack test with cathode patten regulated type

BALANCE OF PLANT FOR SOFC EXPERIENCES WITH THE PLANNING, ENGINEERING, CONSTRUCTION AND TESTING OF A 10 kW PLANAR SOFC PILOT PLANT

Kâre Kl0v, Statoil Research Centre, Trondheim / Norway and

Per Sundal, Tor Monsen and Arild Vik, Prototech AS, Bergen / Norway.

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