How to Build a Simple Passive Solar Water Heater

Enjoy a naturally heated shower with a passive solar system.

Energy conservation is important, whether you're concerned about your carbon footprint or just want to save some money on utility bills. Relying on alternative energy sources, such as wind or solar, is a great way to reduce your dependence on expensive electricity and fossil fuels. With some simple materials and a little time, you can build a solar water heater that will provide you with plenty of hot water.

Difficulty:

Moderately Challenging

Instructions

Things You'll Need

• Water
• Several buckets
• Drill
• Drill and Screw Bits
• Scissors
• Hand Saw
• Wood
• Back of a small refrigerator
• A pane of glass (same size as refrigerator backing)
• 12 feet of air pump hose
• Backing material
• Wood screws
• Aluminum Foil
• Duct Tape
• Angle Cutter or Hack Saw

Collect Materials

1. Visit junk yards, thrift stores and construction recycling sites to find the materials that you need for this project. If your local dump has a coolant collection program that removes freon from old refrigerators and air conditioners, it's likely they'll have plenty of old fridges lying around, and you can get the heat dispersal system located on the back for a low cost or even free. Scrap wood and possibly the air pump hose can also be found at the landfill. Other materials can be found around the house or at building supply store for a low cost.

2. Assemble all your materials in a garage or workspace before starting to make sure you have everything you need, and possibly extra materials in case a wrong cut is made or an errant hole is drilled.

3. Gather the tools you'll need including saws, drills, wood nails, drill bits, safety goggles and gloves.

Prepare for Construction

1. Remove the heating coil from the back of the used fridge, leaving the two end tubes intact and making sure you leave ample leads on the end for attaching the water hoses later on.

2. Cut your backing material to the relative size of the pane of glass that you're using. An old commercial sized doormat can be perfect for this backing, but it might take you a while to cut to size. Dark colored felt will also work well.

3. Prepare a large piece or pieces of aluminum foil to create an additional reflective layer, the same size as the backing.

Make the Frame

1. Construct a set of two wooden frames about the same size as the backing you've cut. Assemble the pieces of wood into a rectangle, lay the backing and aluminum foil on the frame, and lock them into place by building a similar frame on the back.

2. Drive large wood screws through the front frame, the backing and into the back frame to hold everything in place.

3. Use duct tape or caulk to seal any cracks on the inside of the frame.

Attach Heat Collector To Frame

1. Cut some notches using the saw or drill for the entry and return ports to the collector, and fit the entire collector coil inside the wooden frame, on top of the foil and backing. Use duct tape to seal any cracks or gaps.

2. Attached the collector to the backing securely, using the mounting brackets that came on the fridge and some duct tape.

3. You can also use some screws and wood if you have extra in your materials collection and you want to be especially sure that nothing slips.

Attach Hoses and Glass

1. Attach the air pump hose (available at any local aquarium supply store) to the end of the entry and return ports that were left intact when you collected the heating coil from the old fridge.

2. Attach the pane of glass to the front of the frame box using brackets, or duct tape. The glass will trap all the infrared radiation from the sun inside the panel where the collector will then absorb it. The resulting heat will be trapped inside the unit and used to heat the water.

3. Duct tape could start to loosen and slide after a few days in the sun or rain, so if you used it to attach the glass, be sure to cover the unit when it's not in use.

Just Add Water

1. Set the panel up at an angle where it will catch the most sun throughout the day. Using traditional siphoning techniques, place one of the air pump hoses at the bottom of a bucket of cold water, and suck on the other piece of hose until water comes all the way through the heating coil (try not to get any in your mouth!).

2. Set your cold water bucket (source) on a shelf or ledge above the warm water bucket (return), and gravity will continue the siphoning process.

3. The glass will trap all the infrared radiation from the sun inside the panel where the collector will then absorb it. The resulting heat will be trapped inside the unit, and used to heat the water.

Tips & Warnings

• Be careful! The sun is very hot, and these types of passive solar water heaters can be very efficient, meaning that the water coming into your return bucket might be hot enough to burn you. Keep a small water thermometer on hand when you use the heater, so that you'll know when the water is a safe temperature for showering and cleaning (around 110 degrees F).

References

• Solar Water Heating Basics

Resources

• 7 Solar Water Heating Designs