Three-dimensional (3D) geometries were 3D-printed to make unique geometries filled with activated carbon to improve water transport and photothermal conversion when used as solar evaporators. Evaporation was modelled to study the different aspects affecting the evaporation performance of five geometries. Low convection airflow, concave surface evaporation, light reflection and natural convection were investigated in a 2D flat surface and four 3D structures presenting a concave surface. It was revealed that the effect of surface-to-surface radiation has a limited impact on the evaporation rate (1%), which depends linearly on the evaporation area. We have undoubtedly shown that, both in forced and natural convection, concavity in the structure should be avoided as it leads to moisture-saturated air. On the contrary, the 3D structure should be as open as possible to allow the unsaturated air to escape.