Physics: Contactless method to produce clean water

Clean water vapour can be generated from salty or dirty water using sunlight and a light-absorbing material that does not need to be in direct contact with contaminated water, reports a study in Nature Communications.

Using sunlight to heat thermally conductive materials floating on water provides a low cost and environmentally friendly way of heating salt water to generate steam, which can then condense into drinking water. However, the salt and impurities left behind during this process inevitably fouls the material, reducing the device’s performance over time.

Thomas Cooper, Gang Chen and colleagues created a device that uses a light-absorbing material, which does not need to be in physical contact with the water. Instead of heating water directly through thermal conduction, the material heats a black paint that emits infrared light. The water, lying someway below the device, absorbs the infrared light, heats and vaporizes.

The lack of contact avoids material contamination and allows clean water to be generated efficiently for longer operating times. Such solar-driven desalination systems could address the grand challenge of supplying the planet with drinking water in a sustainable way, the authors conclude.