I am designing a compact home on a high elevation in Colorado. There will be a finished basement apartment on a concrete slab and I was thinking of spiraling PVC pipe through the slab to heat it. Instead of converting solar to electric and incurring transformation loss in the process, I was curious if some of my solar farm cells can be dedicated to directly heat the water in the tank before it is recirculated through the floor pipe as more efficient. What types of setups/equipment is available?
A common design in my area is a heat exchange tank upstream of a traditional gas or electric water heater. They use ethylene glycol (antifreeze) that circulates by thermosiphon action from a solar panel to the tank. The illustration below shows a more complicated (with pump and controller) version. So, you heat a tank of water with a coil full of antifreeze that is naturally heated and circulated.