Evaporative cooling promotion using macroporous hydrogels with stable water transport and evaporation path

Abstract Evaporative cooling is being re‐evaluated in the context of eco‐systems and environmental friendliness to improve the efficiency of thermoelectric and photovoltaic power generation. One of the essential tasks to improve evaporative cooling performance is the development of materials that can maintain the evaporation path and supply the lost water. Here, we synthesized a macroporous hydrogel by freeze casting at a slow cooling rate. A series of open spaces was designed between the aligned columns of the hydrogel, and water is stably supplied by extensive capillary channels. In a cooling test, it was shown to be effective in reducing the target's equilibrium temperature. As the heat input increased, the cooling effect (that is, the temperature reduction by the hydrogels) tended to increase. In addition, under airflow, the effect was stable, and further enhanced. These results extend design strategies for hydrogel‐based evaporative cooling and offer opportunities to maximize cooling performance by searching for optimal surface shape and exploiting airflow conditions.