I am interested in getting some general guidance in making a solar water heater for my domestic residence using mostly all home-made components (i.e. Solar collector, piping but probably will purchase the heat-exchanger tank and other components beyond my ability and patience).
So I envision making a solar collector using simple, sweat-soldered copper piping, with this feeding a heat-exchanger tank, to pre-heat the potable water going to my conventional, (tank) heater. So the heat exchange fluid (distilled water or maybe a non-toxic fluid) is separate from the water being consumed.
Beyond having two temperature sensors (one at the collector, to measure when the collectors become warm enough and one at the exchange tank, to measure when the water in the exchanger needs to be heated, i can think of a few other circumstances that I don’t know how to address. 1) How do I handle the circumstance when there is no usage (i.e. As when on vacation) and the hot water accumulates and the tank gets too hot. (I envision a collector that is ~eight ft by eight ft with one-half inch copper pipe that is sweat-soldered “serpentine fashion” over the entire 8x8 area). The heat exchanger would take the form of an old, jury-rigged 50 gallon tank with a home-made, coiled copper tubing exchanger inside. I suppose I could rig a simple overheat pump that would dump the overheated water outside, or maybe some kind of cover that could be moved in front of the solar collector if it got too hot. Any ideas are appreciated…I want this to be relatively simple but not unsafe.
Of course an Arduino Uno would be my controller and I intend to communicate with the sensors with a digital I/O because the wire runs to the sensors might get pretty long.
Any suggestions and constructive criticism is appreciated.