Cooling
Because industrial, residential, or agricultural activities use energy, they will produce heat. This heat eventually needs to be dissipated into the environment, or the temperature will continue to rise. Heat can be transported via convection, conduction, and radiation.
Convection
Convection on Mars is minimal due to its very thin atmosphere, with even fan-assisted convection appearing to be less mass efficient than radiative cooling[1].
Conduction
Conduction into Mars regolith or megaregolith (soil or bedrock) may be feasible, since the ground's average temperature is around -60C. On Earth ground-source heat pumps are feasible for cooling. On Mars, depending on the ground conditions, sufficient cooling may be available via the building's foundation alone, or this could be augmented with cooling channels, which could be combined with existing utility trenches used for power or materials.
Challenges include the low temperature of the ground requiring a careful choice of working fluid, and interior humidity may deposit frost on cooling panels.
Some regolith, such as dry dust or loose rock, may have poor thermal conductivity, requiring either additional conduction area such as drilled cooling pipes or channels, or a soil treatment such as water injection to increase thermal conductivity by filling the soil pore voids with ice.
Radiation
Radiative cooling is a standard solution for spacecraft, since the large temperature difference between outer space (around 3K) and human habitable areas (around 300K) gives substantial radiative cooling from high emissivity surfaces.
The Stefan-Boltzmann law describes the thermal emission of a black body radiator as j=e σ T4, where the radiated power in watts j is equal to the surface emissivity e (between 0 and 1), a constant σ, and the fourth power of thermodynamic temperature T. For a surface at 293K (about 20C) with emissivity 0.8, the black body radiative cooling is 334 W/m2 when facing the cold dark of space.
On Mars, during the nighttime a structure's roof could be used for radiative cooling, which could be as simple as a high-emissivity coating applied to the existing roof.
One challenge with radiative cooling is keeping sunlight from warming the radiator panels. A possible mitigation is a careful arrangement of mirrors[2] to reflect sunlight away, or a paint with high visible reflectance but high thermal emittance.
- ↑ von Arx and Delgado, "Convective heat transfer on Mars", AIP Conference 1991 https://aip.scitation.org/doi/abs/10.1063/1.40133?journalCode=apc
- ↑ Lunarpedia Lunar Radiator https://lunarpedia.org/w/Lunar_Radiator
