I've been kicking around this idea for some years. Just thought I'd publish it here, maybe generate some more ideas from it.
It consists of a solar collector that heats water and then stores it in an insulated box in the basement of a home.
The collector is made from coils of PEX tubing , painted black that is inside a glazed box outside, facing the sun.
The storage container is a styrofoam box with 6 inch thick walls, built in the corner of the basement. two sides being reinforced by the basement walls, the other two sides by 2x4 construction.
The sun would heat the water to about 140 degrees F, it would decend into the tank for night time storage, or used at once by being pumped through a heat exchanger coil that is in the forced-air duct work. At night the water could be allowed to drain out of the collector coils and stored in the tank.
My diagram>>>https://www.dropbox.com/s/8ylu10v4w1lpo0g/IMG_20210310_094647_563.jpg?dl=0 like this collector>>>