MIT Scientists Discover Light-Induced Evaporation, Opening Doors for Desalination and Climate Modeling
November 4, 2023
Researchers at the Massachusetts Institute of Technology (MIT) have made a groundbreaking discovery that light can cause evaporation at a higher rate than heat alone. This finding could have significant implications for various industries, particularly in desalination and climate modeling.
Scientists at MIT were perplexed when they found that water held in a hydrogel material was evaporating at a rate higher than expected based on the amount of heat it was receiving. In some cases, the evaporation rate doubled or even tripled the theoretical maximum rate achievable with thermal energy alone.
After conducting new experiments and simulations, the researchers concluded that, under certain conditions, light can directly induce evaporation at the interface of water and air. This phenomenon, known as the “photomolecular effect,” occurs more efficiently than heat-induced evaporation. The team suggests that this effect may occur in other conditions beyond hydrogel-bound water.
The implications of this research extend beyond desalination. The findings could shed light on the formation and evolution of fog and clouds, leading to improved climate models. Furthermore, this discovery may eliminate the need to convert sunlight to heat in solar-powered desalination processes, potentially tripling water production.
The researchers were initially skeptical but confirmed the phenomenon when they replicated experiments conducted by another group. They found that photons of light were knocking water molecules loose from the water’s surface, causing the excess evaporation. This effect specifically occurs at the boundary layer between water and air.
To measure the evaporation rate, the team exposed the water surface to different colors of light and precisely controlled wavelengths. They found that the effect was color-dependent and peaked at a particular wavelength of green light. When they tried to replicate the evaporation rate using electricity to heat the material, water evaporation never exceeded the thermal limit.
The researchers have named this effect the “photomolecular effect” and are now exploring its potential applications. They have received grants to study the use of this phenomenon in solar-powered desalination and climate change modeling. The team believes that this discovery could significantly improve the efficiency of desalination and potentially lead to cheap and accessible water production.
In collaboration with other research groups, the MIT team is actively working to replicate their findings and address any skepticism surrounding this unexpected discovery. The researchers hope that their work will pave the way for innovative solutions in desalination and other industrial processes.
The findings were published in the Proceedings of the National Academy of Sciences. The research team includes postdoc Yaodong Tu, professor of mechanical engineering Gang Chen, and their colleagues at MIT’s Department of Mechanical Engineering.