Conceptual Design of a Solar Powered Heat Pump for Lunar Base Thermal Control System

When permanent bases are established on the moon, various methods may be employed to reject the heat generated by the base. One proposed concept is the use of a heat pump operating with a vertical, flow-through thermal radiator which is mounted on a Space Station type habitation module. Since the temperature of the lunar surface varies over the lunar day, the sink temperature for heat pump heat rejection will vary. As a result, the heat pump power demand will also vary over the lunar day. This variable power requirement could be provided by a fixed horizontal solar photovoltaic (PV) array placed on the lunar surface, since its power production will vary sinusoidally with the time of day. Using a dedicated PV array to power the heat pump may represent a favorable mass trade-off compared to enlarging the size of the base's central power grid due to power system simplification and improvements in efficiency. To effectively evaluate the potential mass and performance of this integrated power and thermal system, an analytical study was conducted for an equatorial lunar base.

Conceptual designs and mass estimates were made for lunar base power systems for three cases: no heat pump, grid connected heat pump, and heat pump with a dedicated horizontal PV array. The heat pump with dedicated PV array was found to have a power mass penalty of only 20 kg/kW, 43% less than the grid connected system.