Build a Simple Solar Water Heater
All you need is some black pond liner, plywood, a plexiglass sheet, a big bucket, and some hoses and clamps. In total it will cost around £30 assuming that you have to buy all of the materials you use (rather than recycling junk). For your efforts you will have a solar water heater which will heat up a 5 gallon bucket of water to well over 40 degrees celcius (the temperature of a hot bath).
The solar panel is made as pictured toward the top of this article. It is backed with black pond liner which is both waterproof and an excellent solar absorber. The panel is sealed with plexiglass and so it is water tight. A tube connects the bottom of the bucket to the bottom of the panel, and another tube connects the top of the panel to the top of the bucket.
As the sun shines on the panel water heats up and rises up the path until it reaches the top and passes over into the bucket thanks to thermosyphoning (click here for more details).
As the warm water leaves the panel, more water is sucked back into the bottom of the panel. This is colder water from the bucket, and so the cycle continues ad infinitum: hot water passing from the panel into the bucket, and cooler water being passed from the bucket into the panel to be heated further.
Ideally the bucket should be well insulated and kept sheltered from the wind so that heat is not wasted.
Details of a more advanced DIY Solar Water Heating Prototype are available here, or click here to view more details plans for the construction of the basic Solar Water Heater described in this article.