Superthermal Solar Interfacial Evaporation is not due to Reduced Latent Heat of Water
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D4EE05591H.pdf
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Author(s)
Zhang, James H.
Mittapally, Rohith
Lva, Guangxin
Chen, Gang
Date Issued
January 13, 2025
Journal
Energy & Environmental Science
Publisher
Royal Society of Chemistry
Citation
Zhang, James H., Mittapally, Rohith, Lva, Guangxin and Chen, Gang. 2025. "Superthermal Solar Interfacial Evaporation is not due to Reduced Latent Heat of Water." Energy & Environmental Science, 18 (4).
Version
Final published version
Abstract
To explain reported solar interfacial-evaporation rates from porous materials beyond an apparent 100% efficiency using the thermal evaporation mechanism, many publications hypothesize that intermediate water inside porous materials has a reduced latent heat. Key supporting evidence is that water-only surfaces have lower natural evaporation rates than porous evaporators, with the ratio of the two rates taken as the latent heat reduction. Through simulations and experiments, we study natural evaporation of water and show that reported differences in evaporation rates between porous materials and water are likely due to experimental error from recessed evaporating surfaces. A few millimeter recession of the water surface relative to the container lip can drop evaporation rates by over 50% due to a stagnant air layer, suggesting that the comparative experiments are prone to error. Furthermore, in the reduced latent heat picture, interfacial cooling must occur at the porous sample–water interface due to the enthalpy difference between bulk water and intermediate water. Our transport modeling shows that reduced latent heat cannot explain superthermal evaporation and that new mechanistic directions need to be pursued.
MIT Department
Massachusetts Institute of Technology. Department of Mechanical Engineering
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Creative Commons Attribution-Noncommercial
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DOI of Published Version
https://doi.org/10.1039/D4EE05591H
