flows from the fuel cell unit to the user. The electrical loads associated with each subsystem have been estimated, but, since a detailed design has not yet been developed, the actual power conditioning requirements are not known. Therefore, a specific mass of 10 kg/kW was used to characterize the power conditioning subsystem. Results A schematic layout of the complete RFC system with cryogenic storage, including radiators and PV array, is shown in Fig. 8. The mass breakdowns for the 250 kWe baseline and cryogenic systems are presented in Table V. A comparison of the cryogenic system with the baseline system shows that the cryogen plant (drying and liquefaction equipment and associated radiators) accounts for an additional 7218 kg not present in the baseline system. The PV array mass is increased by 1601 kg over the baseline system, reflecting the additional power required to operate the cryogen plant. Similarly, the power conditioning mass is also increased by 1968 kg. Although the cryogen plant and augmented PV array and power conditioning requirements result in the addition of 10 787 kg to the baseline system, the total cryogenic system mass found to be less than half of the mass of the gaseous system. The primary reason for the significant decrease in total system mass lies in the hydrogen and oxygen reactant tank mass. A saving of 81072 kg is realized by replacing the pressurized gas storage tanks with cryogen storage tanks. This is due to the decrease in tank volume when storing the reactants as cryogens as opposed to pressurized gases. As shown graphically in Fig. 9, the additional mass associated with
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