MIT researchers have just demonstrated that temperature is not the only energy driving water evaporation. The team discovered that visible light can create water evaporation. This fact was not previously known. The discovery could solve unanswered atmospheric questions and lead to new technology advances.

Although water is almost transparent to visible light, the team demonstrated that the air–water interface interacts strongly with visible light. The team used laser devices to show that visible light knocks water molecules free at the air-water surface. The process has been termed the “photomolecular effect.” This effect could better explain sunlight’s interactions with clouds, fog, oceans, and lakes, as well as the impacts on climate and weather. The photomolecular effect could also lead to new types of desalination plants using solar energy.

The team performed 14 verification experiments to prove the effect. The team also found:

• The strongest evaporative effects happened using light polarized with transverse magnetic polarization that hit the surface of the water at a 45° angle.
• It was also strongest with green light, which was counterintuitive because green light typically interacts least with water.

Manufacturers have been expressing interest in the research, include for drying paper at mills, and evaporating syrup. The study has been published in the journal PNAS.

Image: Bryce Vickmark. The laser-based device that induced evaporation from light alone.

David Shiller

David Shiller is the Publisher of LightNOW, and President of Lighting Solution Development, a North American consulting firm providing business development services to advanced lighting manufacturers. The ALA awarded David the Pillar of the Industry Award. David has co-chaired ALA’s Engineering Committee since 2010. David established MaxLite’s OEM component sales into a multi-million dollar division. He invented GU24 lamps while leading ENERGY STAR lighting programs for the US EPA. David has been published in leading lighting publications, including LD+A, enLIGHTenment Magazine, LEDs Magazine, and more.

See Full Bio