Check out a GSHP.
A GSHP still uses a refrigerant. Coolant is the issue here.
r410 is double the pressure so leaks are more frequent than with r22 systems. It seems the environuts are ok with r410 escaping to the atmosphere cause to them its safer than r22 escaping. I read that the escape concerns from r22 were about chlorine leaking out. What a joke.
In the end the cost of running and maintaining r410 system are higher and the gear starts being troublesome much sooner.
I have 4 systems, three are r22 and they are all older then my one r410 system. The r22 have never leaked or needed coolant added.