DIY Passive Solar Water Heater

A large rubber band secures the plastic to the lid.

Building a contraption that heats water using the sun's own power can be simple and done inexpensively. A passive solar water heater is a device that does not need or use electric or pump parts of any kind. Instead of being pumped out of the solar water heater, the water is siphoned with a hose or transported manually with buckets. Solar water heaters do not contribute to environmental pollution and when used to supplement a home's electrical hot water supply, can reduce the monthly costs of utility bills.

Things You'll Need

• Bucket, 5-gallon
• Spray paint, flat back
• Laminating plastic
• Rubber band, very large
• Windshield reflective cover
• 2 Binder clips, large

Instructions

1. Spray paint the entire outside of the 5-gallon bucket with flat black paint. Allow the bucket to fully dry.

2. Place the bucket on a flat surface in the sun. Fill it with water until it reaches one to two inches from the top.

3. Spread laminating plastic over the top of the bucket and secure it with a large rubber band, keeping the plastic tight.

4. Unfold the reflective windshield cover with the shiny side facing you. Place the reflective cover across the back of the bucket so that it encloses at least half of the bucket with the cover standing straight up. Secure the reflective cover to the lip of the edge of the bucket with two large binder clips. Wait approximately four hours before using the water.

Tips & Warnings

• You will see steam forming and water droplets collecting on the plastic as the water heats. Leave the plastic undisturbed until you are ready to use the water to keep the temperature as high as possible. To maximize exposure to the sun, move the bucket with the direction of the sun every hour.

• Do not try to lift the bucket alone if it is too heavy. Leave the plastic on to prevent spills and possible scalding while you or a helper pack the bucket to wherever you need the water to be. Some passive solar water heaters create very hot water over 100 degrees. If you are concerned the water is too hot after touching it, then mix part of the water with cooler water to obtain the desired temperature.

References

• Build It Solar: The Integral Passive Solar Water Heater Book
• United States Department of Energy: Solar Energy Technology

Resources

• Public Broadcasting System: Make a Solar Water Heater