A solar water collector is composed 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 circulation from the collector to the tank is done through the use of a pump (forced circulation) or by natural circulation, taking advantage of the different densities between hot and cold water (thermosyphon).
Thermosyphon effect: the water heats up in the collector and becomes less dense going up the tank, the cold water is more dense and descends towards the collector.
To achieve the thermosyphon effect, the water tank must be above the solar collector.
Homemade solar collector materials.
- Expanded polystyrene box (also known as technopor, styrofoam, feather …).
- Clear plastic or glass plate the size of the mouth of the box.
- PVC tube preferably black. You can always spray paint the tubes with matte black.
- 5 liter can.
- Silicone for tubes.
- Diary paper.
Instructions for making a homemade solar collector.
Pierce the top and bottom of the can 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 close the joints.
Place the rack inside the styrofoam box. Make the holes in the box so that the tubes that will go to the can can come out. Cover the top with the glass, preventing air from escaping from within. (You can use silicone to seal the glass, but I recommend you seal the glass last when you check for water leaks.)
Use some support so that the collector is inclined (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 some support and connect the collector to the tank by means of tubes. Seal the joints with silicone.
Cover the tubes and the can with newspaper to avoid heat loss. Finally, fill the tank with water 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.