Hot Water Storage Tank as Cheap Passive Solar Thermal Energy Storage Unit for your Home.
You can easily build your own DIY thermal reservoir and place it in your living room. Water storage tank (or so called “heat storage tube”) can range from 4 to 10 feet (1-3 m) in height with 12 to 18 inches (30-45 cm) diameter. That kind of tube holds a lot of water inside, which equals to a lot of free heat. If you plan to construct the tubes yourself, also have in mind that the structure needs to hold and sustain huge amount of water with all the weight and pressure that comes along with such volumes.