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Harvesting Fresh Water With a Fog Catcher

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Abstract

Did you know that about 1 in 10 people worldwide do not have access to clean water? Collectively, girls and women worldwide spend an average of 200 million hours every day collecting the water they need from rivers, water holes, or lakes. What if there was a way to capture water from another source—like the air? In areas where there is a lot of fog, a device called a fog catcher makes this possible. Fog catchers use fine meshes to capture and collect water droplets from the foggy air. They have become popular in areas where water scarcity is a problem. In this science project, you will build your own fog catchers and investigate which mesh materials are best for collecting water from fog.

Summary

Areas of Science
Difficulty
 
Time Required
Short (2-5 days)
Prerequisites
None
Material Availability
Readily available
Cost
Low ($20 - $50)
Safety
No issues
Credits
Svenja Lohner, PhD, Science Buddies
This science project was inspired by a lesson from the Peace Corps on harvesting water from fog.

Objective

To investigate which mesh materials are best for collecting water from fog.

Introduction

A fog catcher device - a large rectangle of mesh material supported by a steel frame - stands on a mountain slope. Five people are standing next to the device. The fog catcher is two to three times the height of the people, and wider than it is tall.

We all need water—not only for drinking, but also for bathing, growing plants, washing clothes, and much more. In many regions of the world, though, clean water is scarce. In areas without adequate rainfall, people have had to get creative and find other ways to get the water they need. In some places, such as those prone to fog, the air itself can be a source of fresh water.

Several tree stems in a forest barely visible in the fog. Image Credit: Pixabay license. No attribution required.
Figure 1. The suspended water droplets make the fog visible.

The air around us contains moisture in the form of water vapor. Clouds form when the air temperature gets cool enough that the water in the air starts to condense, which means that the water vapor turns into tiny water droplets. All these tiny water droplets make a cloud visible to us. Fog is a low-hanging cloud that touches the ground. Fog can make it difficult to see very far, as shown in Figure 1.

Fog can be found in many different parts of the world, including coastal areas, mountains, and deserts. Coastal regions frequently get fog because the warm air of the land meets the cooler air from the ocean right around or just above ground level. When these air layers collide, the water vapor condenses, and fog is created. Thus, fog can be a valuable source of water for people living in these regions. While the collected water may need additional treatment steps to make it clean enough to drink, it can be used immediately for most other purposes.

But how can you get water out of the fog? With a fog catcher! A fog catcher is a device made of a mesh material that collects water droplets from the foggy air. Mesh screens are set up perpendicular to the path of the wind. As the wind carries the fog through the mesh, the water droplets get caught and accumulate on its surface. Once the droplets combine and become big enough, gravity pulls them down the mesh and into containers set up for water collection. Fog catchers are becoming more popular in areas where water scarcity is a problem, and they can provide a sustainable source of clean water. The two linked videos show some large-scale fog catchers set up in Peru and Morocco.

In this science project, you will build your own fog catchers and investigate which mesh materials are best for catching water droplets from fog. You will simulate fog by spraying water from a spray bottle to create a cloud of mist. By the end of this project, you will have a better understanding of fog catchers and how they can be used to address water scarcity in different parts of the world. So let's get started!

Terms and Concepts

Questions

Bibliography

For help creating graphs, try this website:

  • National Center for Education Statistics, (n.d.). Create a Graph. Retrieved June 25, 2020.

Materials and Equipment

Disclaimer: Science Buddies participates in affiliate programs with Home Science Tools, Amazon.com, Carolina Biological, and Jameco Electronics. Proceeds from the affiliate programs help support Science Buddies, a 501(c)(3) public charity, and keep our resources free for everyone. Our top priority is student learning. If you have any comments (positive or negative) related to purchases you've made for science projects from recommendations on our site, please let us know. Write to us at scibuddy@sciencebuddies.org.

Experimental Procedure

Building Your Fog Catchers

Follow the instructions below or watch this fog catcher video for instructions on how to build your fog catchers. In the video, a pantyhose is used as mesh material. In this science project, you will build several fog catchers with different mesh materials.

  1. Take the wire coat hangers and form each of them into a diamond shape by stretching them out as shown in Figure 2. You will need one hanger for each mesh material you are going to test.

    Diamond-shaped coat hangerImage Credit: Svenja Lohner, Science Buddies / Science Buddies

    Hands holding a wire coat hanger that is diamond-shaped.


    Figure 2. Wire coat hanger stretched into a diamond shape.
  2. Cover each diamond-shaped opening with a different mesh material. Use two layers of the material. If necessary, ask an adult to help you with this step.
    1. Use scissors to cut the mesh material into the right size and shape. It should be a little bigger than the area of the diamond-shaped coat hanger. Note: If you use pantyhose as a mesh material, you can slide it over the coat hanger and secure it with tape on both ends, as shown in Figure 3. This way it will already have two layers.
    2. Put hot glue along the wire of the coat hanger and glue the mesh material in place.
    3. Glue another layer of the material on the opposite side of the coat hanger. You should have two layers of mesh.
    Panty hose stretched over a coat hanger that has been bent into a diamond shape. Image Credit: Svenja Lohner, Science Buddies / Science Buddies
    Figure 3. Mesh material (pantyhose) secured on the diamond-shaped wire coat hanger.
  3. With a marker, label each of your containers with the name of a different mesh material. Then fill each one with sand. The sand will secure the wire coat hanger in place and make sure the container doesn't fall over.
  4. Straighten the hook of each wire coat hanger, then place the end into the container of sand labeled with the appropriate material. The diamond portion should stand upright and be stable. Your finished fog catchers should look like the one in Figure 4.
Assembled fog catcher placed upright in a jar of sand. Image Credit: Svenja Lohner, Science Buddies / Science Buddies
Figure 4. Fog catcher ready for testing.

Testing Your Fog Catchers

  1. Make two data tables like Table 1 and Table 2.

          Mesh Material             Weight in grams [g] before spraying      
    Trial 1 Trial 2 Trial 3 Average
         
         
         
    Table 1. Data table to record the fog catcher weight before spraying.


          Mesh Material             Weight in grams [g] after spraying      
    Trial 1 Trial 2 Trial 3 Average
         
         
         
    Table 2. Data table to record the fog catcher weight after spraying.
  2. Before you start testing, weigh each of your fog catchers.
    1. Zero the scale and place the whole device (including the container of sand and the diamond mesh part) on the scale.
    2. Record the weight of the fog catcher in your data table (Table 1).
  3. Fill the spray bottle with tap water.
  4. Point the spray bottle away from your fog catcher. Squeeze the trigger until it starts spraying. The mist coming out of the spray bottle will simulate the water droplets inside the fog moving through the air.
  5. Now hold the spray bottle about a foot away from the mesh of your first fog catcher. Aim the spray bottle at the fog catcher, as shown in Figure 5, and pump it 10 times. Note: Make sure to put your other fog catchers out of the way so they don't catch any mist from the spray bottle.
     Image Credit: Svenja Lohner, Science Buddies / Science Buddies
    Figure 5. Spraying at the fog catcher simulates fog moving through the mesh.
  6. Observe what you notice on the surface of the mesh material and record your observations in your lab notebook. Spray the mesh 10 more times and make another observation. Spray 10 more times (for a total of 30) and record a final observation in your lab notebook. Note: Try to keep the spraying consistent, so that approximately the same amount of water comes out of the bottle each time. You also need to spray from the same distance every time.
  7. After 30 sprays, let the fog catcher sit for about 5 minutes to let all the collected mist run off the mesh. Then weigh the fog catcher again.
    1. Zero the scale and carefully place the entire device (including the container of sand) on the scale.
    2. Record the weight of the fog catcher in Table 2. Note: Depending on the size of your spray bottle, 30 sprays might not be enough to collect a significant amount of water. If you don't see the weight of the fog catcher increase by more than 1 gram, increase the number of sprays. Keep track and make sure to use the same number of sprays for each fog catcher.
  8. Repeat steps 5–7 with all the other fog catchers. Do not forget to record all your data. Refill your spray bottle with tap water when necessary. You want to make sure every spray has a full load of water. Use the same number of sprays, and make sure you spray from the same distance every time.
  9. Let all your fog catchers dry. You can use paper towels to wipe off the mesh surfaces. Dry all the sand at room temperature or in the oven, or replace the sand in the containers with fresh, dry sand.
  10. Repeat steps 2–9 and test all the fog catchers again. Record your measurements in the Trial 2 columns of your Tables 1 and 2. Doing multiple measurements is good practice in science and helps to ensure that you can trust your data. Use the same number of sprays, and make sure you spray from the same distance every single time.
  11. Repeat steps 2–9 one more time. Record your results in the Trial 3 column of Tables 1 and 2.

Analyzing Your Data

  1. Use the data for each of your testing trials to calculate the average mass of each fog catcher before and after spraying it with water.
    1. In Table 1, for the first mesh material, add the masses of the dry fog catcher from trials 1–3, then divide the result by three to get the average dry measurement. Record your results in the table.
    2. Repeat step a for each mesh type.
    3. In Table 2, for the first mesh material, add the masses of the wet fog catcher from trials 1–3, then divide the result by three to get the average wet measurement. Record your results in the table.
    4. Repeat step c for each mesh material.
  2. Make a data table like Table 3 and calculate how much water each fog catcher collected.
    1. Using the calculated averages from step 1, subtract the average dry weight of the first catcher from its average wet weight. Record your results in Table 3.
    2. Repeat step a for each mesh material.

           Mesh Material             Collected water [g]     
      
      
      
    Table 3. Data table to record how much water each fog catcher collected.
  3. Make a bar graph to visualize your data.
    1. Label the x-axis (horizontal axis) "Mesh material" and the y-axis (vertical axis) "Collected water in grams." Plot the collected water you calculated for each fog catcher in your graph. The height of the bar should represent how much water each fog catcher collected. Note: You can make your bar graph by hand or online. If you need help creating your graph, you can use the Create a Graph resource.
  4. Optional: Calculate how efficient your fog catchers were in collecting water.
    1. Determine how much water you sprayed onto each fog catcher.
      1. Weigh an empty container on the scale. Write down its mass in your lab notebook.
      2. Spray 30 times directly into the empty container with your spray bottle, just as you did with the fog catchers.
      3. Weigh the container with the collected water on the scale again and record its mass in your lab notebook.
      4. Discard the water, dry the container, and repeat steps i–iii two more times. Each time, record the weight of the empty container and the container with water.
    2. Calculate the average weight of the container before and after spraying, as you did for the fog catchers in step 1.
    3. Calculate how much water you collected inside the container, as you did for the fog catchers in step 2.
    4. Now you know how much water you sprayed onto each fog catcher. Calculate the percentage of water the fog catcher collected. This will tell you the efficiency of your fog catcher.
      1. Make a data table like Table 4 and fill out columns 1–3 with the data you already have.
      2. Use the following equation to calculate the fog catcher efficiency:
      3. Record the result in your data table.
           Mesh material      Water collected by the fog catcher [g] Water collected in the empty container [g] Fog catcher efficiency [%]
          
          
          
      Table 4. Data table to record the fog catcher efficiency for each mesh material.
    5. Use your data in Table 4 to make a bar graph.
      1. Label the x-axis (horizontal axis) "Mesh material" and the y-axis (vertical axis) "Fog catcher efficiency [%]". Plot the calculated fog catcher efficiencies in your graph. Note: You can make your bar graph by hand or online. If you need help creating your graph, you can use the Create a Graph resource.
  5. Look at your tables and graphs. Use your results to answer the following questions:
    1. How well does each of your mesh materials perform?
    2. Which mesh material performed the best?
    3. Which mesh material performed the worst?
    4. How do the results for each mesh material differ?
    5. Did you expect these results?
    6. Can you explain your results?
    7. What other factors besides the mesh material could have affected your results?
icon scientific method

Ask an Expert

Do you have specific questions about your science project? Our team of volunteer scientists can help. Our Experts won't do the work for you, but they will make suggestions, offer guidance, and help you troubleshoot.

Global Connections

The United Nations Sustainable Development Goals (UNSDGs) are a blueprint to achieve a better and more sustainable future for all.

This project explores topics key to Clean Water and Sanitation: Ensure access to water and sanitation for all.

Variations

  • In this science project, you weighed your whole fog catcher—the sand-filled container and the fog catcher—to determine how much water the fog catcher collected. However, strictly speaking, the water that had accumulated on the mesh material of the fog catcher had not been collected in the container yet. It could still evaporate, and thus would be lost again. If you want to calculate how much water your fog catcher truly collected, repeat the experiment, but only weigh the sand-filled container before and after spraying. Be careful not to lose any water from the mesh while moving the fog catcher.
  • Improve the water-collecting efficiency of your fog catcher even more! Use the same procedure to investigate how other parameters, such as the mesh thickness or the mesh size (the number of openings in one square inch of mesh), affect the water-collection performance of a fog catcher.
  • Find other ways to simulate fog or water droplets suspended in the air. Instead of using a spray bottle, place the fog catcher close to a humidifier or use it while it is foggy outside. How does this change your results?
  • Repeat the experiment with even more mesh materials. Which one performs best?
  • Does it matter how you hold the spray bottle in front of the fog catcher? Investigate how the distance or angle at which you are directing the mist toward the mesh affects the efficiency of the fog catcher.
  • The amount of water you can collect with a fog catcher is not only dependent on the mesh material, but also on the surface area of the mesh. Can you find a way to scale up your fog catcher to collect even more water? You might need to scale up your mist generator as well.
  • In this science project, the water that each fog catcher collected was caught in the sand inside the container. Can you design a fog catcher that collects the water in a different way—for example, in pipes or in another collection container—so you can use it again?

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General citation information is provided here. Be sure to check the formatting, including capitalization, for the method you are using and update your citation, as needed.

MLA Style

Lohner, Svenja. "Harvesting Fresh Water With a Fog Catcher." Science Buddies, 8 May 2023, https://www.sciencebuddies.org/science-fair-projects/project-ideas/EnvSci_p068/environmental-science/fog-catcher-mesh-material. Accessed 21 Apr. 2024.

APA Style

Lohner, S. (2023, May 8). Harvesting Fresh Water With a Fog Catcher. Retrieved from https://www.sciencebuddies.org/science-fair-projects/project-ideas/EnvSci_p068/environmental-science/fog-catcher-mesh-material


Last edit date: 2023-05-08
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