Tap that hot crack!

Watch out... we may be in hot water soon. At least, we can hope. It seems one of our most pressing issues is sustainability. We need a source for energy which is clean, renewable, and has very little impact on the surrounding environment. Without it, we will continue to use up limited amounts of fossil fuels, polluting and affecting our ecosystem along the way. So, what if the ideal source rests right under our feet?

Down there? What's down there, you might ask. Dirt, rock, and more rock. Ah, but at some level, we find water permeating the rock. That's it. Oh, yes, and heat too. You can go just about anywhere in the United States and find naturally boiling water... it's just several miles down. But not everywhere. In some places, it is much closer.

Throughout much of the west, geologic turbulence has crumpled and cracked the land. Here, glowing how magma rises in burps and bubbles, relatively close to the surface. In places like this the water isn't just boiling hot... it's super hot.

Under the pressure of the ground above, the hot water remains in liquid form. Remove the pressure, and the hot water will immediately flash into steam. Steam? Wait... we were using steam power, like, 150 years ago. That's not 21st century tech... or is it?

The last time steam power was popular, smog was a significant problem. The actual steam was clean and efficient, but the production of it was not. Most steam for engines or machines was produced by firing coal underneath a boiler. In order to get steam, you also got smoke. It is no wonder that steam power went out of fashion along with child labor and the monocle.

Of course, some places are poised to take advantage of geothermal steam--no smoke is needed. In some unusually thin or otherwise volcanically active spots, this naturally heated water conveniently bubbles up to the surface--hot springs. In the glory days of steam power, insightful entrepreneurs took advantage of these springs, not only providing exotic soaking retreats, but naturally heated rooms. The Indian Springs Resort in Idaho Springs, CO still uses geothermal-fed radiators in their Victorian-age rooms.

Folks in the Rockies are still coming up with insightful ways to take advantage of Mother Nature's hot spots. In Mosca, CO, near the Great Sand Dunes, alligators withstand sub-alpine winters by bathing in geothermal waters. Across the valley, tilapia fish are grown in naturally heated water for land-locked seafood lovers. Elsewhere, tomatoes thrive in geothermal-fed hydroponic greenhouses.

Wait... how do we get from bathing alligators to reducing fossil fuel dependency? It isn't as if we all have a convenient hot spring in our backyard. Yet, throughout almost the entire United States, we have naturally boiling water, just a few miles away. Down, that is. At the mere depth of 6 kilometers, water is held at boiling point... or even hotter:

Since 1960, when the first geothermal power plant opened in California, geologists and engineers have been working to tap this vast reservoir of power. Already, a significant portion of our power comes from below. Here's a statement from the Geothermal Energy Association:

The United States has nearly 2800 megawatts of electricity connected to the grid. As the world's largest producer of geothermal energy, The U.S. generates a yearly average of 15 billion kilowatt hours of power, comparable to burning about 25 million barrels of oil or 6 million short tons of coal per year. Geothermal energy is used for electrical power production in 21 countries, and supplies significant amounts of electricity to countries such as the Philippines, where 27 percent of electricity derives from geothermal sources. Even so, this worldwide use represents only a fraction of the potential power that could be generated from geothermal resources.

Colorado sits on top of many of the prime geothermal resources, but has yet to open a geothermal plant. An article in last week's Cherry Creek News suggests that Governor Ritter hopes to change that:

"Geothermal energy presents an opportunity to expand renewable resources in Colorado that is often overlooked. This opportunity fits perfectly with Governor Ritter's promise to add a full mix of renewable energies for our state," said Tom Plant, OEMC director, while delivering the conference opening address. "Our hope is to have geothermal energy take a seat at Colorado's renewable energy table alongside solar and wind power."

So, how does a geothermal power plant work? Must it be near a hot spring? Does it pollute? Does it use up the water? (In Colorado, the last thing you'd want to do would be to use up the water.) The system is actually quite simple and efficient. The plant may be located near a familiar "hot spot" such as a geyser or a hot spring, but not necessarily. It isn't practical to build the plant on top of the feature itself--nature's treasures, in this sense, are preserved.

After a suitable location (preferably flat) is chosen, two wells are dug. First, the injection well is drilled into the hot depths. Water is then poured in, which widens small cracks and fissures, freeing space for the water to flow in an underground reservoir. A second well is dug nearby, which is used to extract water from the reservoir, using natural pressure created by the heat.

As the water rises to the surface, the pressure is reduced, causing the fluid to "flash" into steam. This steam then flows into a turbine, which is used to generate electricity. The steam and water exiting the turbine is condensed to water, and returned via the injection well. Alternatively, in binary plants, the water remains in a closed loop, running parallel to a second pipe full of surface water. The surface water is heated by its proximity to the geothermal pipe. This page from the NREL explains the differences between the two types of plants, along with corresponding images.

For the best demonstration of a geothermal power plant, click the diagram above to check out a nifty animation (from CalEnergy, owner of the Geysers Power Plant.)

Image notes: Map, "Geothermal, the energy under our feet" via the EERE, Alligator pictures via the NREL, "How a geothermal power plant works" via CalEnergy. Steam car picture via PatentlyO. Photo of clouds, reflected on Meadow Hot Spring, Utah, taken by the author.