MIT engineers have bettered their solar-powered, Atmospheric Water Harvesting (AWH) system to extract drinkable water from dry air.
Led by Professor Evelyn Wang and graduate student Alina LaPotin, the scientists haven’t just made their initial design more practical, but also scalable and efficient.
Instead of using costly and hard to access Metal Organic Frameworks (MOFs), the new MIT design uses an adsorbent material called a ‘zeolite’ composed of a microporous iron aluminophosphate.
Zeolite is widely available, stable, and has the right adsorbent properties to provide an efficient water production system based just on typical day-night temperature fluctuations and heating with sunlight.
The two-stage design developed by LaPotin makes clever use of the heat that is generated whenever water changes phase.
The sun’s heat is collected by a solar absorber plate at the top of the box-like system and warms the zeolite, releasing the moisture the material has captured overnight.
That vapor condenses on a collector plate – a process that releases heat as well. The collector plate is a copper sheet directly above and in contact with the second zeolite layer, where the heat of condensation is used to release the vapor from that subsequent layer.
Droplets of water collected from each of the two layers can be funneled together into a collecting tank.
According to the scientists, the overall productivity of the system in terms of its potential liters per day per square meter of solar collecting area (LMD), is approximately doubled compared to the earlier version.
Moreover, it can work at humidity levels as low as 20% and requires no energy input other than sunlight or any other available source of low-grade heat.
Wang’s team will continue to work on refining the materials and design of the device. What they have in mind is creating a portable version for military field operations.
Image and content: Alina LaPotin/MIT News