I don’t know if the output of the desalination is what we actually need or how much refinement it would need, but the salt output would probably still outpace our ability to use it. Sodium is just 1 factor of building these newer batteries.
e.g Tesla has a factory with a 40gwh storage output when fully scaled, and it’s taken years to get there. Cells weren’t the only factor in that.
Ya, if you have a miner at home, it will reduce your heating bill. You just gotta find a good use for it when it’s not cold outside, so something like supplementing your water heater as you mentioned would work ya.
I think there’s merit in the idea. Someone makes an electric water heater purpose built for this and they build a miner card you can swap in/out as technology improves the the current one becomes obsolete. Uses the miner for primary heat, and when it’s not enough uses regular electricity to make the heat.