A solar water collector is made up of a surface that captures solar radiation and a thermal circuit (tubes) through which the fluid passes. In order to reach a higher temperature, it is necessary to have a transparent cover that allows the creation of a greenhouse effect and a generally insulated box.
The resulting heat is stored in a tank. The water is circulated from the collector to the tank by using a pump (forced circulation) or by natural circulation, taking advantage of the different densities between hot and cold water (thermosyphon).
Thermosiphon effect: the water heats up in the collector and becomes less dense when moving up the tank, the cold water is more dense and goes down towards the collector.
To obtain the thermosiphon effect, the water tank must be above the solar collector.
Homemade solar collector materials.
- Expanded polystyrene box (also called technopor, polystyrene, feather …).
- Clear plastic or glass plate the size of the mouth of the box.
- Preferably black PVC tube. You can still paint the tubes with matte black.
- 5 liter can.
- Silicone for tubes.
Instructions for making a homemade solar collector.
Drill the top and bottom of the box to create the cold water inlet and the hot water outlet. The size of the hole should be the same diameter as the tube.
Depending on the size of the box, cut the tubes and make a grid. This grid of tubes will be our solar radiation capture surface. Use silicone to seal the joints.
Place the holder inside the polystyrene box. Make the holes in the box so that the tubes that will go to the box can come out. Cover the top with the glass, preventing air from escaping from the inside. (You can use silicone to seal the glass, but I recommend you seal the glass last when checking for water leaks.)
Use a bracket so that the collector is tilted (more or less at an angle equal to the latitude of your city. If you don’t know it, use this online tool. You don’t need an exact measurement, but an approximate value.
Place the water tank above the collector using a support and attach the collector to the tank by means of tubes. Seal the joints with silicone.
Cover the tubes and box with newspaper to prevent heat loss. Finally, fill the water tank and you can put the collector in the sun.
Full instructions: Solar guide
If your budget is higher, you can use a copper tube like the one seen in the video. But I recommend that the tube have an S shape and not a knot, because the important thing is to increase the area of the tube exposed to the sun.