Atmospheric Water Harvesting and Yield Tracking

ISEF Category: Environmental Engineering

Subcategory: Water Resources Management  ·  Difficulty: Intermediate  ·  Setup: Home Setup  ·  Time: 1 to 2 Months

The Hook

Air can hold water even when it feels dry. Your project asks a simple question, how much water can you pull from that air when the weather changes? A small cone with salt-treated cotton can turn invisible humidity into measurable droplets. That makes this a real engineering test, not just a demo.

What Is It?

Atmospheric water harvesting means taking water vapor from air and turning it into liquid water. Your cone works like a moisture trap. The hygroscopic salt in the cotton wick pulls in water vapor from the air because hygroscopic materials attract water. Then the cone shape and cooler surfaces help that water collect and drip.

Think of the system like a sponge that keeps reaching for moisture, even when the air only has a little. The DHT22 sensor gives you two numbers, relative humidity and temperature. Relative humidity tells you how full the air is with water vapor compared with its maximum at that temperature. Temperature matters because warm air can hold more water than cool air, so the same humidity reading can mean different real water amounts at different times of day.

Why This Is a Good Topic

This is a strong science fair topic because you can measure a real output, water yield, and connect it to environmental conditions you can log yourself. You do not need a university lab to start, and you can build a clear engineering question around design, materials, and weather. The project also links to water scarcity, off-grid water collection, and climate adaptation. You can learn sensor logging, data cleaning, graphs, and how to test whether a design works better under certain conditions.

Research Questions

• How does relative humidity affect the daily water yield of a salt-wick atmospheric water collector?
• How does ambient temperature affect water yield when relative humidity stays in the same range?
• Does changing the salt used in the cotton wick change the amount of water collected over a day?
• To what extent does cone angle change condensation and dripping efficiency?
• Which wick thickness gives the best balance between moisture uptake and water release?
• How does morning, afternoon, and night humidity change the collector's yield pattern?

Basic Materials

• Plastic or lightweight metal cone structure for the collector
• Cotton rope or cotton fabric strips for wicks
• Hygroscopic salt such as calcium chloride or magnesium chloride
• Digital kitchen scale with 0.1 g accuracy
• DHT22 temperature and humidity sensor
• Microcontroller such as Arduino Uno or ESP32
• Jumper wires and breadboard
• Small container or cup for collecting water
• Notebook or spreadsheet for recording readings
• Tape, glue, scissors, and ruler

Advanced Materials

• 3D-printed or machined cone with adjustable angle
• Precision balance with at least 0.01 g resolution
• Calibrated RH and temperature logger
• Data acquisition board or microcontroller with SD card module
• Interchangeable wick materials such as cotton, rayon, or cellulose rope
• Controlled environmental chamber or sealed test box
• Chemical-grade salts with known hygroscopic behavior
• Thermocouples or surface temperature probes
• Image capture setup for droplet tracking
• Desiccator or drying oven for material conditioning

Software & Tools

• Arduino IDE: Programs the microcontroller that reads the DHT22 sensor and logs environmental data.
• Google Sheets: Organizes daily yield data and helps you make quick graphs.
• Python: Lets you clean time-series data, compare groups, and run basic statistics.
• ImageJ: Measures droplet size or wet area from photos if you track surface condensation.
• RStudio: Supports deeper statistical testing and plots for comparing design variants.

Experiment Steps

1. Define the exact design variable you will test first, such as salt type, wick thickness, or cone angle.
2. Set up one consistent way to measure water yield, then decide whether you will weigh collected water, count droplets, or both.
3. Plan your sensor logging so humidity and temperature readings stay tied to each yield measurement.
4. Build control groups that let you separate the effect of weather from the effect of your collector design.
5. Create a data table before testing, so every run records the same fields in the same order.
6. Decide how you will compare day, night, and overall yield, then choose one statistical test before you start collecting data.

Common Pitfalls

• Using a sensor placed too close to the wet collector, which can read local moisture instead of ambient air.
• Weighing the collector while salt is still absorbing water from the air, which blurs the true yield measurement.
• Letting the wick length or packing density change between trials, which mixes design effects with material inconsistency.
• Ignoring the start and end times of each cycle, which makes daily yield numbers impossible to compare.
• Comparing raw water output without adjusting for humidity and temperature, which hides whether the collector really improved.

What Makes This Competitive

A stronger project goes beyond simple before-and-after testing. You can earn that strength by using a clear control group, tracking both yield and weather, and comparing more than one design variable. Good analysis matters too, especially if you model yield against humidity and temperature together instead of looking at one factor at a time. A novel material choice, a better cone geometry, or a cleaner way to separate dew from absorbed water can push the work much farther.

Project Variations

• Test different hygroscopic salts in the same cone design to compare which one gives the best water yield.
• Compare cotton wicks with other porous materials such as rayon, cellulose rope, or paper-based fibers.
• Add a surface temperature sensor and analyze whether cooler collectors produce more water at the same humidity.

Learn More

• NOAA Climate Data Online: Search for local humidity and temperature records to compare with your own sensor data.
• NASA Earthdata: Find background on atmospheric moisture, dew point, and water cycle measurements.
• PubMed: Search for review articles on atmospheric water harvesting, hygroscopic salts, and moisture capture materials.
• USGS Water Science School: Read plain-language explanations of the water cycle, humidity, and evaporation.
• MIT OpenCourseWare: Look for environmental engineering and fluid or heat transfer course materials that help with design thinking.