Adobe bricks as zero-material-cost solar evaporators for water-scarce regions

Consistent access to clean water is amongst the most pressing of global crises, particularly in less developed and off-grid communities. We present a high-efficiency solar evaporation device perfectly suited to address this crisis. Composed solely of soil, the adobe brick is a material that is easy to fabricate, and whose raw constituents are widely available at no cost. Once prepared, these bricks exhibit superb water absorption properties, excellent solar absorption, and efficient photothermal conversion, all of which contribute to a pure water evaporation rate of 2.52 kg m- 2 h-1 (77 % evaporation efficiency) and a salt water evaporation rate of 2.16 kg m- 2 h-1 under an irradiance of one sun. Suitable pore sizes allow salt water to be converted to fresh water with only minimal salt buildup over 6 h and rapid rejection of particulates to the reservoir below. Variations in soil makeup and inclusion materials are characterized in detail, and evaporation rates are compared. This enables recommendations for the composition of an ideal adobe brick evaporator and important conclusions for the study of solar evaporation materials. While soil composition may be optimized for performance, the high evaporation rates of all samples indicate opportunities for adobe brick desalination across all biomes.