In a groundbreaking discovery that upends long-standing views on the evaporation process, MIT researchers have uncovered that light alone can trigger the evaporation of water, a departure from the widely held belief that heat is the sole driver. This newfound "photomolecular effect" could have profound implications, potentially altering climate change calculations and heralding advances in solar-powered desalination and drying technologies, according to MIT News.
Mistakenly believing that evaporating water was a straightforward process, the MIT scientists meticulously demonstrated through a series of experiments that not only heat but also light plays a pivotal role. With experiments showing water molecules breaking away from the surface and into the air due solely to light exposure, the team provided convincing evidence that challenges the heat-centric paradigm of evaporation.
The study, detailed in the journal PNAS, was carried out by Carl Richard Soderberg Professor of Power Engineering Gang Chen, along with postdocs Guangxin Lv and Yaodong Tu, and graduate student James Zhang. Employing 14 distinct tests and measurements, they meticulously established that under visible light, evaporation ensued without the aid of thermal energy—a fact consistent across multiple experimental setups.
One of the hallmarks of the discovery, MIT researchers say, lies in the cooling and stabilizing air temperature above the water's surface as it starts evaporating under light – a phenomenon signaling that the underlying force driving the evaporation is not thermal. Amid these findings, the researchers grappled with an unexpected twist: an evaporation effect that peaks with green light, which is odd considering that water's transparency is highest at this color and should minimally absorb light.
The photomolecular effect's potential applications are vast, as noted by Gang Chen in an interview captured by MIT News. "I think this has a lot of applications," Chen said, revealing the interest already shown by industries including solar desalination and industrial drying, where evaporation is a critical process. This research stands to revolutionize methods in water treatment and material processing that occupy a significant chunk of industrial energy consumption.
The discovery could also explain a lingering question in climate science – the mysterious extra absorption of sunlight by clouds, a discrepancy debated for decades. With the photomolecular effect, Chen and his colleagues believe they might have an explanation that could reconcile these measurements, which have puzzled researchers due to the complexity of cloud behavior and the challenging nature of atmospheric data collection.
The significance of this finding extends beyond academia, with implications for practical applications that benefit from the enhanced evaporation rates this effect enables. Georgia Tech's Shannon Yee, not involved with the study, praised the MIT team's rigorous work, saying, "Who would have thought that we are still learning about something as quotidian as water evaporating?" as reported by MIT News.
Funded in part by an MIT Bose Award, this study represents just the beginning of a new line of scientific inquiry, one that not only reshapes our understanding of fundamental processes but also holds promise for technological innovations rooted in the very nature of water and light.
