Here is the floor heat system
http://thesmartestheat.com/earth-thermal-storage-electric-radiant-heating-systems/
This system is supposed to be more efficient than hydronic. If one area of sand is below set point then only a few pads will heat instead of the entire floor or zone. I have worked on these and talked to several farmers who have them and they are very satisfied and no issues (yet).
Must have off peak metering though otherwise too expensive. Like any electric heat.
ok i see now i thought it was still the hydronic systems that are installed in sand. I can see what you mean off peak being pretty important. I see they are out of aberdeen might have to check out the stuff when i am there.