Who actually understands how geothermal heating works?

Yes , as a simple exercise , put some alcohol , or nail polish remover on the back of your hand , as the liquid evaporates it uses the heat from your hand to evaporate , in geo heating the liquid use the heat from the earth like your hand , to bring it back up to its liquid state temperature , it is passed into a compressor which pressurises it causing it to "boil " this then passes over a heat exchanger which the water from your heating system passes through , the fluid has now lost all its heat and returns to the earth to warm up again , the heat pump uses electricity but with the help of the natural heat from the earth you can get up to 3 times a return on the energy used

like a backwards fridge, if you mean heat pumps.