Analyzing Adsorptive Atmospheric Water Harvesting Methods with a Modular Low-Cost Testbed
Independent research project conducted in Princeton which involved designing, building, testing, and analyzing a desiccant-based atmospheric water harvesting device.
Preliminary Sketch
Challenge
In this project, I developed a versatile and portable source of fresh water by harvesting water directly from the air. Atmospheric water harvesting can provide water security in locations that lack traditional water sources, such as regions with little rainfall. Desiccant-based atmospheric water harvesting functions in low-humidity environments by first trapping (adsorbing) moisture in a desiccant and then releasing (desorbing) and condensing the water. My objectives for this project were to develop a low-cost, functional, and modular testbed that can be iterated upon to study the efficiency of desiccant-based atmospheric water harvesting.
Action
I designed the modular testbed in Fusion 360. The design functions in two stages. The first functions by flowing cool air over silica gel beads, permitting them to adsorb its water. The second stage flows hot air by the silica, forcing it to release its water, producing warm, humid air that can subsequently be cooled to condense the water. In order to permit rapid prototyping and modification, I designed a modular interface between components of a stacked duct design. This promoted an iterative design process. When testing indicated that the copper tubing heat exchanger was insufficient for desorbing the water from the silica desiccant, the modular design permitted me to quickly replace the heat exchanger with a much more effective fin-tube heat exchanger.
In order to monitor, test, and evaluate the design, I mounted 2 SHT31X humidity and temperature sensors in each chamber of the duct. For calculating the efficiency of the design, I stationed a flow meter in the water inlet of the heat exchangers and two thermistors at each inlet and outlet. I collected this data using an Arduino and displayed the results in real time using Python.
Atmospheric Water Harvester CAD
Live measurement display
Results
The atmospheric water harvester successfully harvested 97 grams of water in 4.5 hours, achieving an efficiency of 4.7 kWh per kg of water harvested. The prototype cost under $600, and fit within a 250 x 250 mm footprint for ease of additive manufacturing. As a culmination of the independent work project, I wrote a 46-page paper outlining the engineering design process, which can be viewed here.
