I also found thet I "reinvent the wheel". It is heat pumps. Yes, in "energy of heated soil" is come from sun finaly. Earth surface is some kind of solar panel. The question is what the ariea of such solar panal depending on depth of of the evaporator end evaporator shape/size.
I found info about geothemal gradient. Geothemal gradient is about 2 Cel deg per 100 meters. Example: at the depth 1 km we have temperature 0+2*(1000/100)=20 cel deg for Siberia.
Another idea: Is it possible to bild power plant? The maximal posible coefficient of efficiency of the plant is (Th-Tc)/Th=7%. Coefficent is small so it is need to cool big volumes.
My page was moved to:
Heat energy efficient house for cold countries.