Cincinnatus BLOG *** Political Commentary - Social Commentary

Heat from the Earth, or geothermal - Geo (Earth) + thermal (heat) - energy can be readily accessed by drilling water or steam wells in a process similar to drilling for oil. Domestic geothermal energy is an enormous, and underused heat and power resource that emits little or no greenhouse gases. Mile-or-more-deep wells can be drilled into underground reservoirs to tap steam and very hot water that can be brought to the surface for use in a variety of applications. In the U.S most geothermal reservoirs are located in the western states, Alaska, and Hawaii.  About 8,000 megawatts of electricity are currently produced globally including about 3,000 megawatts of capacity in the United States. The US Department of Energy believes that an additional 15,000 megawatts of geothermal electricity will come on line in the next decade. To put this in perspective, geothermal currently accounts for 5% of the 7% of the US energy supply that is renewable or 0.35% of total US energy. Even if we increase its use fivefold, as the Department of Energy projects, that still would only represent 1.5% of future US energy requirements.

Steam and hot water reservoirs are just a small part of our geothermal resource. In the future, the Earth’s magma and hot dry rock will provide cheap, clean, and almost unlimited energy. For the moment however, safely tapping the magma core for unlimited energy may more appropriately belongs in the realm of science fiction than a near-term energy plan.

Two basic types of power plants are in use today:

•       Steam plants use very hot (more than 360^oF) steam like the Geysers plants of northern California. The steam either comes directly from the source, or the very hot, high-pressure water is depressurized, “flashed” to produce steam. The steam then turns turbines, which drive generators that create electricity. Minute amounts of carbon dioxide, nitric oxide and sulfur are emitted but this is approximately one fiftieth of the amounts produced by a traditional fossil fuel power plants.

•       Binary Plants use lower temperature hot water (100^oF - 300^oF).  The hot water is passed though a heat exchanger in conjunction with a secondary (binary) fluid with a lower boiling point (often isobutene or isopentane). The secondary fluid vaporizes which turns the turbines that ultimately drive the generator. Because binary plants use a self-contained cycle there are no emissions.     

Geothermal plants can be cost effective if the sites are selected with care. Although an interesting growing source of clean electricity, geothermal will probably not make a major impact on US energy supplies in the next two decades. Recently, however, Google one of the world’s largest consumer of energy has been investing in new geothermal technology. It may be counterintuitive, but it is clean industries such as communications that have become the largest consumers of electricity. The electricity is needed to support 24/7 temperature control for endlessly multiplying data centers.

It will take some time before we know if Google’s investment pays dividends. The future may hold many wonders. Stay Tuned!