They say a picture is worth a thousand words.
Right now all I have is these two pictures to illustrate a low cost method of transferring
heat into or out of a cement slab. There are many ways to transfer and transport
the sun's energy. This is one of those methods. I use water to store heat and
cement to transfer that heat into a pressurized DHW system.
Notice the plastic tubes (good up to 160 PSI) are in parallel. This means that one side of the slab will be hotter than the other. This method of transferring heat lends itself to solar applications by efficiently extracting heat and by returning cold water to a collector through heat stratification. There are many ways to accomplish this.
These eight 1/4" tubes are 2" apart and occupy a total surface area of about 500 sq inches inches over a span of about six feet. when imbedded in cement. Drums of water will be later be placed on this cement slab to transfer DHW heat into the hot water system of a house.