Abstract
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.
Date of this Version
9-13-2022
Recommended Citation
Rao, Akshay K.; Fix, Andrew J.; Yang, Yun Chi; and Warsinger, David M., "Thermodynamic limits of atmospheric water harvesting" (2022). School of Mechanical Engineering Faculty Publications. Paper 65.
https://docs.lib.purdue.edu/mepubs/65
Comments
This is the author-accepted manuscript ofA. K. Rao, A. J. Fix, Y. C. Yang, D. M. Warsinger, Thermodynamic Limits of Atmospheric Water Harvesting, Energy & Environmental Science, 15 (10), 4025-4037, 2022. Published by the Royal Society of Chemistry, the version of record can be found at DOI: 10.1039/D2EE01071B.