In the past, researchers and scientists have been working on materials that would collect water from air. Often times, these would require materials in large sizes or quantities in order to produce a significant amount of water. These would also be effective in humid areas, for obvious reasons.
Recently, however, researchers from the University of California, Berkeley, have devised portable systems that would work the same principle, but operate at lower costs-that is, it would not require much space and high humidity.
The secret to the researchers' design underlies in the process of adsorption and desorption. This is a series of processes by which a small piece of solid retains gas or liquid onto its surface and later on releases the collected fluid.
Often, these solid materials are porous, which would account for high surface area to hold the gas or liquid.
The researchers have detailed their work in ACS Central Science. There, they described the technology as a microwave-sized device equipped with fans that would draw air over a cartridge, which contains a MOF. The MOF, or metal-organic framework, that they used has high porosity like other adsorbents. The MOF would then adsorb water from the air. Afterwards, the MOF would be heated to assist desorption and the fluid would then be sent to a condenser.
The MOF cartridge is compact at only about 10 inches square and 5 inches thick. Two sets of channeling systems are connected to the MOF cartridge; one set would be for delivering the water onto the adsorbent, and the other would be for delivering the water to the condenser.
Initially, the researchers claimed that one kilogram of adsorbent would be able to produce 1.3 liters of water per day. However, after testing it for three days in the Mojave Desert in California, an average of only 0.7 liter per day per kilogram of adsorbent was produced. This is still impressive though at more than 50 percent of the theoretical value.
Lead researcher of UC Berkeley chemistry professor Omar Yaghi discussed why this was the case. "It is well known that in order to condense water from air at a low humidity-less than 40 percent relative humidity-you need to cool down the air to below freezing, to zero degrees Celsius, which is impractical," he said.
"With our harvester, we are doing this at very low humidity without such cooling; there is no other material that can do that." He then talked about how important a seemingly small volume of water is. "This is not like a dehumidifier, which operates at high relative humidity. Some people say that 0.7 liters is not a lot of water. But it is a lot of water if you don't have water."
