Can You Really DIY An Effective Solar Water Heater With The Help Of Aluminum Foil?
There are a lot of DIY solar water heater designs out there, but you'd be hard-pressed to find one simpler, cheaper, and easier than YouTuber @sergiyyurko2110's aluminum foil water heater. With a bit of foil and some black paint attached to a frame made of reclaimed wood, he manages to heat a small flow of water by about 20°F instantly by simply running it through some foil tubes that he has painted black. The contraption is fed by gravity and requires no power of any sort, outside of whatever energy was used to lift the water to the top of the mechanism ... most likely municipal water pressure. These sorts of water heaters are useful for many purposes, from energy savings indoors to making your backyard pool more sustainable.
The water heater was an experiment, and @sergiyyurko2110 acknowledges in another video that the foil isn't durable enough to be useful (he recommends thicker sheets of aluminum or steel for a more permanent installation). But the foil method is useful for building a proof-of-concept model, and would certainly survive a few real-world uses if you desperately needed slightly warmer water. The final temperature of the water is about 97.5°F ... far less than the 140°F recommended for electric water heaters. But @sergiyyurko2110, who has built a number of different solar water heaters, has some other ideas about how to improve the basic design.
Making the prototype even better
The series of aluminum foil tubes basically acts like an evaporator coil you'd find in a modern HVAC system. It exchanges heat from the environment, warming the tubes and their contents. Aluminum is a good thermal conductor, but even painted black, the foil won't collect much heat, so he suggests a couple of ways of improving the design. One is to add mirrors that reflect sunlight onto the foil tubes, which he found doubled the resulting water temperature. Another is to enclose the tubes in a frame and cover it with transparent plastic to trap heat inside with the tubes, basically creating a little greenhouse.
These suggestions bring to mind another solar water heater design that works on the same principle, as shown by another YouTuber, @desertsun02. This design uses the greenhouse enclosure idea, but instead of aluminum foil it uses a coil of pex water pipe painted black to absorb as much heat as possible. On a 45° day, @desertsun02 shows the heater producing water that ranges from 130° to 150°. So aluminum foil is a good material for prototyping because it's inexpensive and easy to work with, but there are apparently advantages to making the final product of a more durable, better-insulated tubing. As an upgrade project that promises to make your home more sustainable, a DIY solar water heater like this is a great investment.