How light can vaporize water without the need for heat – MIT research

Image credit: Robert A. Rohde @ Wikipedia

” data-image-caption=”" data-medium-file=”https://tallbloke.files.wordpress.com/2024/04/solar_spectrum.jpg?w=300″ data-large-file=”https://tallbloke.files.wordpress.com/2024/04/solar_spectrum.jpg?w=614″ src=”https://tallbloke.files.wordpress.com/2024/04/solar_spectrum.jpg?w=300&h=221″ alt=”" width=”300″ height=”221″ class=”alignright size-medium wp-image-66886″ srcset=”https://tallbloke.files.wordpress.com/2024/04/solar_spectrum.jpg?w=300 300w, https://tallbloke.files.wordpress.com/2024/04/solar_spectrum.jpg?w=600 600w, https://tallbloke.files.wordpress.com/2024/04/solar_spectrum.jpg?w=150 150w” sizes=”(max-width: 300px) 100vw, 300px” />
The researchers say the effect can be substantial and call it ‘a major part of the picture’. Under the optimum conditions of color, angle, and polarization “the evaporation rate is four times the thermal limit.” It was reported last year but the paper was only accepted last month. That report said: ‘The phenomenon might play a role in the formation and evolution of fog and clouds, and thus would be important to incorporate into climate models to improve their accuracy, the researchers say.’ The best incident angle for the light is 45°, according to the pre-print.
– – –
It’s the most fundamental of processes—the evaporation of water from the surfaces of oceans and lakes, the burning off of fog in the morning sun, and the drying of briny ponds that leaves solid salt behind, says Massachusetts Institute of Technology (MIT, via Phys.org).

Evaporation is all around us, and humans have been observing it and making use of it for as long as we have existed.

And yet, it turns out, we’ve been missing a major part of the picture all along.

In a series of painstakingly precise experiments, a team of researchers at MIT has demonstrated that heat isn’t alone in causing water to evaporate. Light, striking the water’s surface where air and water meet, can break water molecules away and float them into the air, causing evaporation in the absence of any source of heat.

The astonishing new discovery could have a wide range of significant implications. It could help explain mysterious measurements over the years of how sunlight affects clouds, and therefore affect calculations of the effects of climate change on cloud cover and precipitation.

It could also lead to new ways of designing industrial processes such as solar-powered desalination or drying of materials.

The findings, and the many different lines of evidence that demonstrate the reality of the phenomenon and the details of how it works, are described today in the Proceedings of the National Academy of Sciences, in a paper by Carl Richard Soderberg Professor of Power Engineering Gang Chen, postdocs Guangxin Lv and Yaodong Tu, and graduate student James Zhang.

Full article here.
– – –
Image credit: Robert A. Rohde @ Wikipedia