Portable Solar Water Distiller Project

In emergency situations, access to clean drinking water quickly becomes a critical concern. This portable solar water distiller provides a reliable method for purifying contaminated water using only the power of the sun. Unlike a basic solar still dug into the ground, this design can be transported easily and set up anywhere with sun exposure, making it versatile for emergency preparedness or off-grid scenarios.

Overview

This project creates a lightweight, collapsible solar water distiller that uses solar energy to evaporate water, leaving contaminants behind, and then captures the clean condensed water for drinking. The design is based on the scientific principle of the water cycle—evaporation and condensation—and can render many types of contaminated water safe to drink, including saltwater.

Tools Required

• Utility knife or scissors
• Measuring tape
• Marker or pencil
• Hole punch or nail (for making small holes)
• Pliers (optional, for bending wire)
• Sewing needle and thread (or safety pins as alternative)

Materials List

• 2 clear plastic sheets (36" × 36" minimum), preferably greenhouse-grade UV-resistant polyethylene
• 1 dark-colored thin plastic sheet (24" × 24")
• 2-4 plastic bottles (clean, with caps)
• 10 feet of flexible clear plastic tubing (⅜" diameter)
• 4-8 feet of rigid wire (coat hangers work well)
• 8-10 feet of thin cordage or strong string
• Duct tape (preferably black or UV-resistant)
• Optional: silicone caulk (for more permanent seals)
• Optional: small activated charcoal filter (for final water polishing)

Steps

Step 1: Prepare the Frame

1. Create a frame by bending the rigid wire into a square or rectangular shape approximately 24" × 30".
2. Form additional wire segments to create cross-supports and a center ridge that will peak at about a 30° angle.
3. Secure the wire frame pieces together using cordage or duct tape at all junction points.
4. Test the stability of your frame—it should maintain its shape but be collapsible for transport.

Scientific Explanation: A proper frame angle maximizes solar exposure while allowing condensation to flow efficiently downward. The 30° angle optimizes these factors for most latitudes.

Step 2: Prepare the Basin

1. Take the dark-colored plastic sheet and form it into a shallow basin shape by folding up the edges about 2" all around.
2. Secure the corners with duct tape to maintain the basin shape.
3. Test the basin by adding a small amount of water to check for leaks; seal any leaks with duct tape.
4. Attach the basin to the bottom portion of your wire frame using small pieces of cordage or duct tape.

Scientific Explanation: The dark color absorbs solar radiation more efficiently, maximizing heating. The shallow design provides adequate surface area for evaporation while maintaining a suitable water depth.

Step 3: Create the Condensation Surface

1. Take one clear plastic sheet and attach it to the top of the frame, creating an angled surface above the basin.
2. Ensure this sheet is pulled tight and secure it to the frame with cordage or tape.
3. The sheet should be positioned with a slight angle for condensation to run downward.
4. Create a small channel along the lower edge by folding the plastic or adding a thin strip of plastic secured with tape.

Scientific Explanation: The clear plastic allows solar radiation to enter while trapping heat inside (greenhouse effect). Water vapor rises, contacts the cooler surface, and condenses into liquid water that runs down the angled plastic.

Step 4: Construct the Collection System

1. Cut the plastic tubing into appropriate lengths for directing water from the condensation channel to your collection bottles.
2. Create small holes in the collection channel at the lowest point.
3. Insert one end of the tubing into these holes and secure with tape or silicone caulk.
4. Direct the other end of the tubing into your collection bottles.
5. Create a secure seal around the bottle openings using tape or caulk.
6. Make sure to create a small air vent in each bottle cap to prevent vacuum lock.

Scientific Explanation: The collection system works via gravity flow. Proper seals prevent evaporative losses, and venting prevents pressure differentials that could stop water flow.

Step 5: Add the Outer Cover

1. Take the second clear plastic sheet and create a complete outer cover for the entire still.
2. This layer should have minimal contact with the inner condensation surface.
3. Secure it to the frame, creating an air gap between the two plastic layers.
4. Ensure all edges are sealed to create a closed system, except for designated input and output points.

Scientific Explanation: The second layer creates insulation through the trapped air gap, reducing heat loss and increasing internal temperature. This dual-layer approach significantly improves efficiency similar to double-pane windows.

Step 6: Create Water Input and Ventilation System

1. Create a small funnel from plastic and attach it to a section of tubing.
2. Insert this through the outer layer into the basin for adding contaminated water without opening the still.
3. Secure with tape or caulk to prevent vapor loss.
4. Add a small ventilation tube with a loop (to prevent rain entry) to allow pressure equalization while minimizing heat loss.

Scientific Explanation: Pressure equalization prevents deformation of the structure during temperature changes. The input system allows replenishment without disrupting the thermal environment inside the still.

Step 7: Create a Transport Configuration

1. Design a folding pattern that allows the frame to collapse flat.
2. Create a simple storage pouch from excess plastic material.
3. Include written operating instructions on the storage pouch using permanent marker.
4. Practice assembling and disassembling the still to ensure familiarity with the process.

Scientific Explanation: A properly designed transport configuration protects components from damage and ensures all pieces remain together for deployment when needed.

Operating Instructions

1. Setup: Choose a location with maximum sun exposure. Assemble the still and ensure all connections are secure.

2. Fill with Source Water: Pour contaminated water into the basin through the input tube, filling to about 1" deep (approximately 1-2 liters depending on your still size).

3. Position Collection Bottles: Place collection bottles below the still, ensuring proper tube alignment for water collection.

4. Operating Time: Allow the still to operate for a full day of sunlight. Efficiency will vary with sunlight intensity, ambient temperature, and humidity levels.

5. Collection and Maintenance: Remove collection bottles as they fill and replace with empty ones. Periodically check water level in the basin and replenish as needed.

6. Cleaning: After several uses or when changing water sources, rinse the basin with clean water to remove accumulated contaminants.

Expected Performance

• Under ideal conditions (full sun, warm day), expect approximately 0.5-1 liter of purified water per day from a still of the dimensions described.
• Higher ambient temperatures and lower humidity improve performance.
• Production is lower on cloudy days but still continues at a reduced rate.

Scientific Explanation

This solar water distiller works through several simultaneous physical processes:

1. Solar Radiation Absorption: The dark basin absorbs solar energy, converting it to heat.

2. Heat Transfer: The trapped air space inside the still prevents convective cooling while the water in the basin heats up.

3. Evaporation: As water temperature increases, the rate of evaporation increases, converting liquid water to vapor.

4. Fractional Distillation: During evaporation, water molecules convert to gas phase leaving behind:

5. Salt and minerals
6. Heavy metals
7. Most bacteria and viruses

8. Chemical contaminants with higher boiling points than water

9. Condensation: Water vapor contacts the cooler condensing surface and returns to liquid state as pure water.

10. Gravity Collection: Condensed water droplets join together and flow downward due to gravity into the collection system.

The effectiveness of solar distillation is based on the significant energy requirement for phase change (latent heat of vaporization). This physical property allows separation of water from contaminants without requiring complex filtration materials.

Alternative Methods and Variations

Basic Alternative: Plastic Sheet Ground Still

For a simpler emergency option: 1. Dig a hole approximately 3 feet wide and 2 feet deep 2. Place a container in the center 3. Cover the hole with plastic sheet 4. Weigh down edges with rocks or soil 5. Place a small weight in the center directly above the container 6. Water evaporates from soil moisture and condenses on the underside of the plastic

This alternative produces less water but requires minimal materials.

High-Efficiency Variation: Multi-Tray Design

For improved output: 1. Create multiple evaporation trays stacked vertically 2. Separate trays with transparent dividers 3. Allow condensation from each level to flow to the next 4. This design increases surface area and evaporation efficiency

Winter Variation: Insulated Design

For operation in cooler conditions: 1. Add reflective material around outer edges 2. Use black-colored glass or metal for the basin 3. Add insulation below the basin 4. Position to maximize winter sun angle

Safety Information

Water Testing and Treatment

While solar distillation is effective against many contaminants, observe these safety guidelines:

1. Biological Safety: Solar distillation kills most microorganisms but consider adding a final UV exposure step (6 hours in clear bottles in direct sunlight) for certainty.

2. Chemical Contaminants: Distillation is highly effective against most chemical contaminants, but some volatile organic compounds with boiling points lower than water may carry over. In highly contaminated environments, combining with activated charcoal filtration is recommended.

3. Water Testing: If possible, use simple water testing strips to verify quality after distillation.

4. Remineralization: Distilled water lacks minerals that contribute to electrolyte balance. For long-term use, add a pinch of sea salt per liter to remineralize.

Construction Safety

1. Cutting Tools: Exercise caution when cutting plastic and wire materials.
2. Material Selection: Ensure all plastics used are food-safe and do not contain BPA or other harmful chemicals that could leach into water.
3. Sun Exposure: During testing, be aware of potential magnification effects that could create fire hazards.

Troubleshooting Guide

Skills Developed Through This Project

• Understanding of water purification principles
• Basic thermodynamics knowledge
• Improvisation with limited materials
• Critical emergency preparedness skills
• Assessment of water quality and safety

Conclusion

This portable solar water distiller represents a lightweight, effective emergency water purification method that requires no fuel, electricity, or consumable filters. While the production rate is lower than commercial filters, the ability to create safe drinking water from nearly any water source—including seawater—makes this a valuable addition to any emergency preparedness kit, especially in regions where water contamination is a concern.

The principles learned in this project also scale to larger implementations that could provide water for small groups or families in extended emergency situations. By understanding the science behind solar distillation, you gain valuable knowledge that extends beyond this specific design to numerous other water purification techniques.

Disclaimer: This distiller is intended for emergency use. While solar distillation is an effective purification method, no homemade system can guarantee complete removal of all contaminants. Always exercise caution when consuming water from unfamiliar sources, especially in areas with industrial pollution.