In recent years, scientists have discovered that water in certain conditions can evaporate at a higher rate than what could be explained by heat alone. A team of researchers at MIT has made a surprising conclusion: under specific conditions, light can cause water to evaporate directly at the water-air interface, even more efficiently than heat. This phenomenon has been named the “photomolecular effect.” The discovery could have implications for various applications, including solar-powered desalination, climate modeling, and evaporative cooling processes.
Evaporation is a common process that happens all around us, from sweat evaporating from our skin to morning dew evaporating in the sunlight. Researchers had found that water held in a hydrogel was evaporating at rates much higher than expected based on the heat it was receiving. The excess evaporation could double, triple, or more the theoretical maximum rate based on thermal energy. After conducting experiments, MIT researchers concluded that light at the interface where water meets air can cause evaporation directly without the need for heat.
The discovery has potential applications in solar-powered desalination, climate modeling, and evaporative cooling processes. In desalination, the researchers aim to improve the efficiency of the evaporation side of the process, which can lead to higher water production from solar desalination. This advancement could potentially make desalination cheaper.
The researchers found that the photomolecular effect works by light knocking bundles of water molecules loose from the water’s surface. They tested the effect with different colors of light and found that it peaked at a particular wavelength of green light, indicating that it was light itself, not heat, causing the evaporation. While water does not absorb much light on its own, it becomes a strong absorber when combined with a hydrogel, allowing it to harness the energy of solar photons efficiently and exceed the thermal limit.
The photomolecular effect could also have applications in evaporative cooling processes, offering a highly efficient solar cooling system. Overall, the discovery of this phenomenon could lead to significant advancements in various fields and technologies.
