Enhanced Geothermal Systems
Traditional, or conventional, geothermal power production relies on the availability of heat, the natural permeability of rock and the presence of naturally-occurring hot water and steam systems below the surface. Only a finite number of these sites exist and drilling exploratory geothermal wells to find these systems comes with significant risk of failure. Geothermal reservoirs can also decline in temperature, pressure and steam availability over time, decreasing the efficiency of power production. Engineered or Enhanced Geothermal Systems (EGS) technology utilizes improved methods to safely and economically improve conditions at existing power plants, or generate new geothermal systems from the hot dry rock that underlies most of the American west as well as many areas around the world.
A revolutionary new technology makes multi-zone EGS reservoirs possible, lowering the cost of geothermal power. One way to think about it is stacking reservoirs on top of each other like a high rise building stacks office space. Just as the multiple floors in a high-rise office building allow dramatic increases in density on a single piece of real estate, multi-zone stimulation increases the amount of rock (and heat) that can be accessed from a single well. Multi-zone stimulation increases the size of the reservoir and the amount of energy that can be produced from the well by a factor of three or more.
EGS involves environmentally friendly methods to both extract the earth’s heat and convert it to energy. Creating artificial geothermal reservoirs for an EGS involves using hydraulic pressure to create a network of small, interconnected fractures in the rock that act as a radiator, transferring the heat in the rock to water circulating through the system. Hydraulic pressure is applied to “stimulate” existing cracks in the rock to slip, opening slightly and increasing rock permeability. The slip is caused by the tectonic forces that exist in the earth’s crust and are enabled by the lubrication from the water in the opened crack. This stimulation process is called hydroshearing.
The transition of coal to geothermal takes advantage of existing infrastructure, means zero emissions with very low cost to operate, and saves jobs in moving to a more sustainable future. Existing coal plant or mine workers, engineers, and geologists would be slowly transitioned as the geothermal project is developed and operation increases, while the coal plant operation decreases.