Geothermal Heating

Perhaps one of the most potentially radical emergent technologies associated with geothermal energy is the recently developed use of enhanced geothermal systems. The US Department of Energy has been testing sites out in the western United States to use this technique.

Much of the water that was once in the ground has been pumped out, used and evaporated, mostly falling in the seas where its inclusion has been minimal. That leaves a great many sites in arid, western North America that have geothermal potential, without actually having water to generate the energetic steam that is so useful in producing electricity and in actually bringing the heat of the so-called "hot, dry rocks" below. Sometimes these are called "basement rocks."

So that's generally what Enhanced Geothermal Systems are, pumping water into areas that are found to be currently heated by submerged magma but, have long since lost their water to evaporation or never had any water to begin with. The water functions as the delivery system, bringing steam to the surface that can do work, which is technically what electrical power is.

These sites are most commonly those used for power generation, so there is certainly a correlation between the amount of water used and the amount of steam produced. Usually the steam is captured, condensed and re-injected, otherwise the amount of water required would be staggering. When there is no more water to pump in, the site dries up and can no longer be used for this purpose. For this reason, salt water is often used at sites that are anywhere near ocean areas.

Often the cavern of hot rocks is pumped with water for quite some time before. This process creates fractures in the rocks (like ice cubes you pour boiling water on) that expand the area that can be filled with water into a large lagoon.

Holes are then drilled to release the steam in a process called the "doublet." This gives the super heated steam, sometimes as hot as 700F (320C) as it leaves the rock surface, an outlet to reach the surface at the sort of velocities (energies) that are required to reliably turn even a very large turbine for electric production.

Areas of the desert southwest that have such dry caves are the current areas of interest from US government and private investors, Many of whom are active in oil trading circles. It is possible that the geothermal output of the US could increase exponentially in the next few years if suitable water sources are found for the many hot and dry caverns available, many in easily accessible places, decreasing the cost of geothermal electric to historically low levels. Enhanced Geothermal Systems could be what makes geothermal energy useful to the masses.

Geothermal Heating |