Measures For Accommodating Load Changes

The rates of load change occasioned on the envisaged ship by the conditions referred to above proved to be: +4.3%/s for bow thruster actuation, - 42.5%/s for crash stop astern maneuver, and + 10.5%/s for propeller racing.

TIME [sec]

Fig. 2 Load fluctuations estimated to crash stop astern maneuver

Fig. 2 Load fluctuations estimated to crash stop astern maneuver

TIME [sec]

occur upon

Fig. 3 Load fluctuations estimated to occur upon propeller racing

Fig. 3 Load fluctuations estimated to occur upon propeller racing

The present analysis proved the load-following performance of the PEFC system constituents to be as follows:-

(1) The PEFC itself responds extremely rapidly to load changes, which can be followed with almost no time lag.

(2) Air supply to cell is expected to respond with some delay-of the order of several seconds-but this should not cause any problem in actual practice.

(3) Fuel supply can be expected to create some difficulty. As countermeasure, in the case of the maneuvering pattern of Fig. 1:-

For bow thruster actuation during maneuvers of berthing/unberthing and of entering/leaving port, the fuel supply rate would be set to equal the base load plus command power output of bow thrusters or propulsion motors. Abrupt load increases at rates beyond the response characteristics of the fuel supply system would be accommodated by battery discharge; abrupt load decreases would be absorbed by a gas reservoir to be installed on the reformate gas supply line of the fuel cell. Examination is further under way of a means of burning the unutilized anode off-gas in a catalytic combuster and recovering the effluent heat.

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