Device uses cotton threads to capture water

Two-thirds of the world’s population experiences water scarcity at least one month a year, according to the United Nations. Cooling towers in thermoelectric power plants are major consumers of fresh water. Pairing these towers with water vapor–capture systems could lessen industrial freshwater use, leaving more of the essential resource for people to drink. But these systems are too costly or use too much energy to be competitive.

Now, researchers at the University of California, Los Angeles, led by Yongho Sungtaek Ju have improved the efficiency of one such system, called humidification-dehumidification (HDH) desalination. Like previous versions of the technology, the approach collects condensed water from humidified air. With the help of some cotton strings, Ju’s team built a device with a condensation rate per volume up to three times as high as that of previous designs (Sci. Adv. 2019, DOI: 10.1126/sciadv.aav7662). In the new device, cold water beads traveling down cotton threads trap water vapor from hot, humidified air being blown upward. The cotton string–based device is lighter than similar devices made of metal and glass, Ju says.

The device’s simplicity is impressive and may minimize the loss of water vapor to diffusion in the air that is typical of HDH systems, says Massachusetts Institute of Technology engineer Evelyn Wang.