Assessment of lunar base energy system with lunar limited resources as variable-composition mixed working fluids: Working fluid Selection, component variation law, and full-cycle operational characteristics

A sufficient supply of energy is a prerequisite for lunar base construction. The Moon’s extreme day-night thermal fluctuations (90–400 K) and low gravity (which weakens two-phase flow efficiency) directly make traditional thermodynamic cycles impractical. Coupled with limited in-situ resources, these constraints create an urgent need for sustainable lunar energy solutions, this is the core motivation for our research. Therefore, this paper proposes to construct a combined cooling, heating, and power generation supercritical thermodynamic cycle system for the lunar base using the limited lunar resources and mixed working fluids. By establishing a mathematical model, the day − night operation rules of the lunar base are analyzed. During lunar daytime, the thermal efficiency ( η _th) varies with time and the split ratio, reaching up to 14.09 %, with a maximum net power of 80.14 kW. An optimal cooling load of 3 kW was identified for peak performance. During lunar nighttime, η _th gradually decreases as the thermal storage unit temperature drops, with a maximum of 56.21 %, while the required radiator area increases with higher heat loads. The study further demonstrates through dynamic optimization of the mixed working fluid composition that, for lunar daytime, targeting high η _th requires a high CO₂ concentration, whereas minimizing the radiator area necessitates a high H₂ proportion. For the lunar nighttime, a composition of 0.1:0.1:0.8 was found to simultaneously achieve high thermal efficiency and a minimum radiator area.