Passive Solar Water Heater

I live in the north. I wanted a passive solar water heater that could warm water that could be used to warm soils for growing more productively. I was able to make this passive solar water heater that was efficient, low cost, low tech and fairly easy to make. This solar water heater was able to warm the water in the 45 gallon plastic barrel 15 degrees Celsius in about two hours.

Step 1: Materials

double wall polycarbonate sheet

1 ½ PVC pipe

2 end caps

2 reducer caps

5’ of ¾ poly pipe

2 barrel bungs for ¾ poly pipe\PVC solvent

4 1” pipe clamps

Silicon bath sealer

Flat black spray paint

45 gal plastic barrel

Step 2: The General Design

For the overall design, I used the double wall polycarbonate as the channel that water moved through. As it moved up the channels, the thin tubes of water are heated, creating a convection action. The water in the 45 gallon plastic barrel is filled to match the top of the polycarbonate panel. The back of the polycarbonate panel is painted flat black to increase heat absorption. The panel is angled at about 40 degrees from the horizontal and faces south to maximize the solar gain.

Step 3: Preparing the Barrel

The plastic 45 gallon barrel is fixed with two bungs positioned so one is even with the bottom of the solar panel and the other even with the top of the solar panel. Water will be filled above the level of the top bung. This will mean there is on difference in water pressure are even

Step 4: Preparing the Panel

The panel is made from double wall polycarbonate. This 1/4" material has channels that allow water to flow upward, moved by convection, from the bottom to the top of the barrel. The panel is heated by sunlight as it passes through the front of the panel but is absorbed by the black coating on the back of the panel. The water moves through the bottom and top PVC pipes that are fitted to the panel.

Step 5: The Top and Bottom Pipes Linking the Polycarbonate Panel

I cut two pieces of polycarbonate to lengths that were about 2” longer than the panel is wide. I then ripped a ¼ slot down one side of each of these pipes. Slide the panel down the slots in the PVC pipes. I then dry fit the end caps and reducer caps to the PVC pipe with the panel installed. This will then determine the length of the PVC pipes. Cut the pipes so that both ends fit snugly against the panel. Run a bead of silicon along the edge of polycarbonate so that it will seal the PVC pipe when it is pulled into the silicon bead. Once the panel is sealed with the PVC, the end sections are cemented in place and attached to the 1/2" poly tubing. The poly tubing is then attached to the bung fittings on the barrel.