Arizona has been in a megadrought for nearly 30 years, with many other states following.  Today, many members of our community have decreasing access to water as it becomes more scarce due to this ongoing megadrought.  How can we create an affordable solution that allows our community to have access to water?  Our solution was to design a Star Wars-inspired moisture harvester that can collect water from the air year-round and help members of our community and communities around the world, in places such as Africa and the Middle East, have better access to clean water. Our design shows the potential for up to 10,000 liters of water collection per year from a small, affordable portable unit even in the near-zero humidities of the Sonoran Desert, with zero carbon footprint.

At the core of our moisture harvester is the hygroscopic material we use to collect moisture from the air, MOF-801, a metal-organic framework with a zirconium base.  MOF-801 has the highest water adsorption rate in the low relative humidities of the desert reported in literature.  As a hygroscopic material, it captures water molecules at ambient temperature, but releases them when heated to 100 C.  The MOF-801 used in our design is created through the “green” synthesis method.

We divide operation into cycles, first adsorption (60-180 min.) and then dehydration (~60 min.).  In a cycle, fans usher air through the MOF-801, hydrating it, before Peltier plates (devices that become hot on one side and cold on the other when current is applied) evaporate the water out of the material and condense it into a container.  The entire system is powered by a solar panel, resulting in a net carbon footprint of zero.  Cycles are automated and run continuously, meaning the device can operate indefinitely without human intervention. The entire prototype was built for less than $200.

Using historic meteorological data from the monitoring station at Desert Mountain High School, and established adsorption rates of the material, we predicted sufficient daily water production given continuous back-to-back cycles to support a human (>1 L), with the exception of less than half a dozen days with relative humidities near 0%.

The revised design includes four self-contained, yet externally air-exposed, sections of 2 kilograms of MOF-801.  This rotates every hour (the time of a dehydration cycle; motor operated), placing one of the sections in the condensing apparatus.  This system allows one section to be hermetically sealed  from the rest of the material, before being heated from the inner-facing surface by the hot side of Peltier plates.  A tube above the section redirects resultant water vapor through a pipe down the center of the material, where it comes into contact with the other, cold side of the Peltier plates, condensing it into potable water for collection.  This system would allow for continuous operation, instead of alternating adsorption and dehydration cycles.

Other new features include the built-in battery, and charge controller, to allow for voltage control and safety, as well as around-the-clock operation; as well as wall-embedded fans for a streamlined profile and less risk of detachment.

Our modeling and calculations indicate an improved efficiency of 22%, allowing for an average collection of up to 27 liters of water per day, and a yearly collection of nearly 10,000 liters.

Going Forward

The combination of successful tests of each component shows that, after further refinement, our moisture harvester should be a viable option for cost-effective water production in drought-affected areas using green energy.

Additional development, including the integration of MOF-801, would allow a fully-developed prototype to become easily accessible and start saving lives, and present an easily affordable and mass-producible device (our entire original construction process sans MOF-801 cost less than $200).

We are encouraged by increasing interest in atmospheric water harvesting as a sustainable solution to the worldwide drought crisis. We continue to work towards developing a cheap, mass-producible moisture harvester, turning science fiction into science fact.