CAREER: Continuous atmospheric water harvesting through gels

With the lowest surface water levels in the Southwestern US in 1,200 years, there is an urgent need to tap into alternative water sources. One source is the water vapor in the atmosphere. Even in arid regions, there is a vast quantity of water that, if tapped, would represent an important new source. Potentially, a solar-panel-sized device could collect enough water to satisfy one’s daily drinking requirement. However, the challenge is that transforming water vapor into liquid form and purifying it requires a sizeable amount of energy and advanced materials. Additionally, the water production rates with state-of-the-art approaches are very low, especially in arid, low-humidity regions. The funding will support an investigation into a fundamentally different approach utilizing easily synthesized gel materials and natural solar energy that could provide substantially increased water production rates. Furthermore, this approach would be tested in the driest city in the US—Las Vegas, Nevada—a metropolitan area where alternative water sources are needed most. In addition, this project will involve the local educational community by distributing water harvesting stations to local high schools to provide valuable real-world data that will support the research effort. The objective of this project is to demonstrate how a flow-through atmospheric water harvesting approach with hydrogel membranes can provide advantageous water production through a focused study of transport and material science. Using the sun to distill captured water, the solar limit of water production is approximately 10 liters per day per square meter of device footprint. The proposed approach uses separate, specialized capture and distillation membranes as well as a storage basin to segregate tasks and improve performance. The central hypothesis is that gel membranes of high poroelastic diffusivity and tunable thermal conductivity are needed to maximize water flux. To test this hypothesis, the project will (1) study heat and mass transport around the membranes and develop new models to incorporate relevant physics, (2) uncover new polymer physics that dictate material transport bottlenecks within membranes, and (3) investigate system behavior in varying conditions and discover viable prototype designs. The work will include a mixture of heat and mass transfer experiments and material testing as well as computational modeling with the finite element method. The work will also involve local water quality experts and an effective demonstration of this harvesting approach will be communicated with the greater community to generate interest in alternative sourcing of water. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.