Just keep the mixture out of your eyes or your blind for life. It's a dangerous soup to be sure.

This process is easily contaminated by CO2 so it may be short lived unless it is filtered air and guess what makes the best CO2 filter?

What's the energy density of this system?

I've always felt that the world didn't have problems with heat or water - just a transport problem.
Whether you want heat, a heat sink, or water, it's always available - just maybe a long way away.

I wonder how this compares in overall energy use to a geothermal (well water or buried glycol tubes) combined with a heat pump. Perhaps with NaOH (commonly known as Caustic Soda or Lye) being highly reactive its intensity can overcome the cost of the raw material, stainless plumbing, pumps, and solar panels.

The old technique was called Passive Annual Heat Storage. It just used insulation, dirt and PVC pipe.

An even better heat source than solar to "recharge" the NaOH would be a heat pump, thus enabling the same system to both heat and cool.

" 50° C (122° F). Which, in a happy coincidence, makes it ideal for under floor heating???" Under floor heating at those temperatures is not likely to make anyone happy. Even wall mounted radiators run on a maximum of 35° C. The efficiency of underfloor heating lies in its substantially lower inlet temperatures.

So the 50 % solution is tricked along a pipe where it absorbs the water - to increase its temperature - so it then goes back to a tank - where it needs to be regenerated back to the 50% - with the water it absorbs being removed - so it then goes back into the pipe - where does the water come back from in the pipe?

Just use a ground source heat pump and forget about the caustic lye. If you need a hole in the ground, you might as well (pun intended) use it.