Geothermal Energy, Heat Pumps, Operation Philosophy, Technology, CostDirect Version (DX Expansion): In heating mode, a geothermal heat pump with a dirGeothermal Energy, Heat Pumps, Operation Philosophy, Technology, CostDirect Version (DX Expansion): In heating mode, a geothermal heat pump with a dirGeothermal Energy, Heat Pumps, Operation Philosophy, Technology, CostDirect Version (DX Expansion): In heating mode, a geothermal heat pump with a dir