Atmospheric water harvesting (AWH) is a rapidly emerging approach for decentralized water production, but current technology is limited by trade-offs between energy consumption and yield. The field lacks a common basis to compare different AWH technologies and a robust understanding of the performance impacts of water recovery, desorption humidity (for sorbent systems), and realistic component-level efficiencies. By devising a set of unifying assumptions and consistent parameters across technologies, we provide the first fair thermodynamic comparison over a broad range of environmental conditions. Using 2nd law analysis, or least work, we study the maximum efficiency for common open system AWH methods – fog nets, dew plates, membrane-systems, and sorption processes – to identify the process performance limits. We find that the thermodynamic minimum for any AWH process is anywhere from 0× (relative humidity (RH) ≥ 100%) to upwards of 250× (RH < 10%) the minimum energy requirement of seawater desalination. Sorbents have a particular niche in colder (T < 310 K), arid regions (<6 g kg⁻¹). Membrane-systems are best at low relative humidity and the region of applicability is strongly affected by vacuum pumping efficiency. Dew harvesting is best at higher humidity (RH > 40%) and fog harvesting is optimal when super-saturated conditions exist. Increasing efficiency at the component-level, particularly for vacuum pumps and condensers, may be the most promising avenue for improvement. Enabled by peta-scale computing, our findings use geographical and parametric mapping to provide a framework for technology deployment and energy-optimization.

Wetting of saline water through membrane distillation pores can be reversed with either drying out the membrane, or more effectively, by backwashing with pressurized air to force out wetting feed water.