For the 250 kWe system, the drying and liquefaction subsystem radiators were sized based on heat loads derived from the data presented in Ref. [4], In order to size the 20 kWe system radiators, the heat load from the drying system was scaled down on total wet gas-mass flow through the driers, while the liquefaction heat loads were scaled based on the mass flows of hydrogen and oxygen to the respective liquefaction units. The radiators were then sized for these heat loads. The fuel cell radiator for both power levels was sized based on the fuel cell heat load calculated in the RFC code. Cryogen-to-Gas Conversion Subsystem The cryogenic reactants must be vaporized and heated prior to being fed to the fuel cell. Approximately 25 kW of heat are required for reactant conversion for the 250 kWe system, while approximately 2 kW of heat are required for the 20 kWe system. Although a detailed analysis of this subsystem has not been carried out to date, it is envisaged that the subsystem would utilize waste heat from the fuel cell to accomplish the conversion. One additional heat exchanger loop would be required which would not contribute significantly to the total system mass. Photovoltaic Array A GaAs sun-tracking array was chosen for use in this system. The specific power of the array is 123 W/kg at 22.512% efficiency and 383 K. The specific mass is 2.48 kg/m2 [8-10]. These numbers include the array blanket, support frame, pivots, tracking mount and wiring harness. The solar array was sized to provide power to the cryogen plant as well as to the lunar installation during the day. The breakdown of the power requirements for both the 250 and 20 kWe systems is given in Table IV. The final array area required to provide this amount of power was 2780 and 221 m2 for the 250 and 20 kWe systems, respectively. For comparison, the baseline gaseous systems required 2134 m2 and 170 m2 of array area. Power Conditioning During the lunar 'day, power flows from the PV array to: (a) the electrolyzer, (b) the reactant driers and liquefaction units, and (c) the user. During the lunar night, power
RkJQdWJsaXNoZXIy MTU5NjU0Mg==