Fog harvesting refinement

0

An MIT graduate student is working to make water available for the world’s poor by refining the tools and techniques of fog harvesting. Engineer and aspiring entrepreneur, Shreerang Chhatre is researching devices that attract water droplets and corral the runoff, relieving the burden of finding and transporting water which traditionally falls to women and children.

In the arid Namib Desert on the west coast of Africa, one type of beetle has found a distinctive way of surviving. When the morning fog rolls in, the Stenocara gracilipes species (also known as the Namib Beetle) collects water droplets on its bumpy back then lets the moisture roll down into its mouth, allowing it to drink in an area devoid of flowing water.

What nature has developed, Shreerang Chhatre wants to refine to help the world’s poor. By harvesting fog, poor villagers could collect clean water near their homes instead of spending hours carrying water from distant wells or streams. In pursuing the technical and financial sides of his project, Chhatre is simultaneously a doctoral candidate in chemical engineering at MIT, an MBA student at the MIT Sloan School of Management and a fellow at MIT’s Legatum Center for Development and Entrepreneurship.

A fog-harvesting device consists of a fence-like mesh panel which attracts droplets and is connected to receptacles into which water drips. Chhatre has co-authored published papers on the materials used in these devices, and believes he has improved their efficacy. “The technical component of my research is done,” Chhatre says. He is pursuing his work at MIT Sloan and the Legatum Center in order to develop a workable business plan for implementing fog-harvesting devices.

Interest in fog harvesting dates to the 1990s, and increased when new research on Stenocara gracilipes made a splash in 2001. One Canadian charitable organization, FogQuest, has tested projects in Chile and Guatemala.

Chhatre’s training as a chemical engineer has focused on the wettability of materials, which is their tendency to either absorb or repel liquids (think of a duck’s feathers, which repel water). One basic principle of a good fog-harvesting device is that it must have a combination of surfaces that attract and repel water. For instance, the shell of Stenocara gracilipes has bumps that attract water and troughs that repel it; this way, drops collects on the bumps then run off through the troughs without being absorbed, so that the water reaches the beetle’s mouth.

To build fog-harvesting devices that work on a human scale, Chhatre says, “The idea is to use the design principles we developed and extend them to this problem.”

To build larger fog harvesters, researchers generally use mesh rather than a solid surface like a beetle’s shell, because a completely impermeable object creates wind currents that will drag water droplets away from it. In this sense, the beetle’s physiology is an inspiration for human fog harvesting, not a template. “We tried to replicate what the beetle has, but found this kind of open permeable surface is better,” Chhatre says. “The beetle only needs to drink a few micro-litres of water. We want to capture as large a quantity as possible.”

In some field tests, fog harvesters have captured one litre of water (roughly a quart) per one square meter of mesh, per day. Chhatre and his colleagues are conducting laboratory tests to improve the water collection ability of existing meshes.

FogQuest workers say there is more to fog harvesting than technology, however. “You have to get the local community to participate from the beginning,” says Melissa Rosato, who served as project manager for a FogQuest program that has installed 36 mesh nets in the mountaintop village of Tojquia, Guatemala, and supplies water for 150 people. “They’re the ones who are going to be managing and maintaining the equipment.” Because women usually collect water for households, Rosato adds, “If women are not involved, chances of a long-term sustainable project are slim.”

“We welcomed Shreerang as a Legatum fellow because it is an important problem to solve,” notes Iqbal Z. Quadir, director of the Legatum Center. “About one-third of the planet’s water that is not saline happens to be in the air. Collecting water from thin air solves several problems, including transportation. If people do not spend time fetching water, they can be productively employed in other things which gives rise to an ability to pay. Thus, if this technology is sufficiently advanced and a meaningful amount of water can be captured, it could be commercially viable some day.”

Customer comments

No comments were found for Fog harvesting refinement. Be the first to comment!