Homemade 40 Gallons Solar Hot Water Collector. We have been using this 5 years. Easy to build and alot of fun. this is made out of pcv pipe. through a collector — where it’s heated by the sun — and then back to the tank. This continues as long as there’s sun on the collector. An off-the-shelf controller monitors the temperatures of the collector and the tank, and it turns the pump on only if the collector is hotter than the tank. When the pump is off, water drains from the collector back to the tank. This type of “drainback” system is especially useful in cold climates because it keeps the water from freezing inside the collectors.
Water is preheated in a single pass through a large coil of PEX pipe immersed in the solar storage tank. The preheated water then goes to your regular hot water tank. This simple one-pass system works well because the PEX pipe coil is large enough to hold quite a bit of preheated water right in the coil, and it has so much surface area that it acts as a good heat exchanger after the initial hot water from the coil has been exhausted. The water in the tank is used strictly to store heat — it is not part of the potable water system.
The floor heating system pumps water from near the top of the tank through the radiant floor loops, and then back to the bottom of the tank. The control system monitors the room temperature and the tank temperature, and it turns the pump on only if the room is cold and the tank is hot. The control system is made from two standard thermostats.
A key feature of this design is that the storage tank is non-pressurized. This gives you a lot of storage volume at a low cost and also eliminates the need for a separate drainback tank and heat exchanger. he system uses a unique heat exchanger consisting of a large pipe coil that is immersed in the heat storage tank. The pipe coil preheats water headed for your conventional hot water heater. There is enough hot water stored right in the immersed pipe coil to support a 15 minute shower — after the hot water in the pipe coil is exhausted, the pipe coil acts as a conventional heat exchanger, picking up heat from the heat storage tank.