Accessing the Earth’s internal heat requires a medium to carry that energy to the surface where it can be harvested and used in geothermal power plants. The most abundant and common medium used to bring geothermal heat up to surface is groundwater or, when at a sufficiently high temperatures, steam. Groundwater is very common in the geology of the Earth and it occurs almost everywhere below the surface. Geological faults and fractures occur within the structure of the Earth which create conduits for water the move within the ground. This groundwater will accumulate in reservoirs below surface within the pore spaces between rocks.
As we know, the Earth continues to get hotter with depth, and by accessing this groundwater at sufficient depths we find high temperature geothermal resources. Alternatively, areas of higher heat flow within the ground (such as in areas of tectonic or volcanic activity) allow us to access high temperature reservoirs at shallower depths. By drilling water wells into these reservoirs we can pump water to surface to be used in our geothermal power plants.
Geothermal power plants are systems which harvest the earth heat within these natural geo-fluids. Once harvested, that heat energy is converted into electricity through geothermal turbine technology.
The most common systems are: