Posts Tagged fog harvesting

Biomimicry and Atmospheric Water Harvesting

Posted by on Saturday, 8 August, 2015

Dew harvesting is ancient, and researchers are currently working on ways to improve it. Fog could also provide an important water source in areas with limited freshwater access. In addition to the fog-basking beetle covered in my last article, researchers are studying plants such as cacti and moss to learn how they harvest water in arid regions. One project that has received attention recently uses a metal mesh screen to collect water from fog; the metal mesh is more effective than the plastics that many fog collectors currently use. Researchers are studying other nature-inspired fog and dew collection methods as well.

Spiderwebs are good at collecting dew because their silk threads can change shape when exposed to water. This causes droplets to pool at points along the web. Studying the silk could be very helpful, since it could result in materials that attract water but quickly release it. A fog collector is more efficient when the water it collects rapidly falls down into the collection tank, allowing the collector to pull in more water. While the wind could shake a light mesh and release the droplets, the collector might not always have access to wind.

Another website illustrates how several types of plants collect water, including moss, horsetail, and cacti. The moss had an interesting water collection technique. Like the threads in the spiderweb, part of the moss structure changes shape when it collects enough water, automatically dumping it out onto the main body of the plant. The moss grows thin stalks with water collecting heads that collapse after collecting water, which can then rebound to collect more.

The moss and spider silk dew harvesting methods are very interesting, since it may be possible to incorporate them into mesh designs. A mesh with small projections, or stalks, could release water more effectively. A mesh that changed shape after collecting water and then returned to its original form could also be very useful. It might even be possible to combine both techniques in a dew harvesting device.

Velcro, the material that helps keep things in place, is another example of biomimicry. It was inspired by prickly burrs that effectively stick to clothing. But Velcro, or a similar material, might have a role to play in dew collection as well. Velcro is a plastic surface with very thin plastic loops attached. The thin loops seem similar to the moss stalks. A similar manufacturing process could create a material like the moss, a surface with thin plastic stalks and water collecting heads. So far it doesn’t seem like anyone has tried this, as manufacturing structures like moss stalks cost-effectively might be challenging, although a company like Velcro might know how to do it. A 3-D printer might also be useful here. Making the stalks and the water collecting heads out of the plastic that was similar to spider silk might also be effective. Of course, I haven’t tested this and don’t know if it would be as effective as a metal mesh screen. Either way, further research into biomimicry could result in better ways to collect dew and water from fog.

Beetles Inspire Water Collection From Air

Posted by on Thursday, 6 August, 2015

It has been a long time since my last post, and in the meantime a severe drought is occurring in the Southwest. Solutions such as desalinization plants could provide some help, but these large-scale plants require energy to operate. They also require saltwater, which is available here but is not available in other places. So I looked into devices that can collect water from air. Consumer products exist, but some of them cost $1000 or more and many of them require electricity to operate or expensive filters. But a desert beetle could illustrate another way to harvest water from the atmosphere.

Several types of beetles in the Namib Desert harvest water from fog. The beetles have different ways to do this; some beetles dig holes to collect water, but other beetles harvest water with their own bodies. The latter method got public attention, inspiring inventors to develop products based on the beetles. The theory is that studying the beetles’ bodies will allow scientists to develop new materials that will make atmospheric harvesting devices more effective.

A journal article from 2010 raises some questions about the original theory. The researchers studied several types of beetles and determined how well they collected water from the air. Instead of discovering that one beetle had a body surface that was more effective at collecting water, the researchers found out that beetles that positioned their bodies to bathe themselves in the fog had the most success. But the original reports still inspired inventors, and the concept of surfaces that can harvest water from the air more effectively remains relevant as well.

In Australia, a drought was affecting farmers. Edward Linacre came up with an atmospheric water harvesting system called the Airdrop after hearing about the Namib Desert beetle. The device is installed underground, where the temperature is lower, helping create condensation. It also uses pipes filled with copper wool, increasing the surface area for condensation. The Airdrop won an Edward Dyson award in 2011. The beetle has also inspired another water harvesting project.

NBD (Namib Beetle Design) Nanotechnologies was founded on the concept illustrated by the beetle. The company’s first project was a water bottle that can condense water from the air overnight. This is a great low-cost and low-energy solution to droughts and water shortages. It was based on the surface of the desert beetle, using a combination of materials that attract water and materials that repel water. While original reports on the water bottle came out in 2012. NBD Nanotechnologies is continuing its work in atmospheric water harvesting and materials science with support from the federal government. In 2015 the company announced that it had received a $750,000 SBIR Phase II grant.

So it does look like certain surfaces and materials can make atmospheric water harvesting more effective, and research in this area appears to be ongoing. And solutions that don’t require an external power source appear possible as well.