ABSTRACT
Mineral extraction historically has been an economic activity for millennia. The principal techniques for mineral extraction from the subsurface, exclusive of oil and gas production, are: underground mining though mine shafts, surface mining using open pits, placer mining, in-situ mining and evaporation ponds. The geothermal exchange relies on the temperature difference between the heat in the pipes and the relatively constant temperature of the groundwater. Early historical groundwater use for manufacturing includes pumping brines for producing salt. In terms of environmental factors, geothermal exchange systems are the only heating and cooling system with a coefficient of performance greater than one. Most of the geothermal heat pumps in the United States utilize a heat exchange process in the ground that circulates the fluid media in a closed-loop system of wells. Direct use geothermal sources mine the heat from deeper heated aquifer zones.
