Ironically, our pursuit of fossil fuels has brought us closer and closer to a much larger, more sustainable source of energy. The interior of our planet is a giant nuclear power plant. The solid rock and soil on which we live our lives is essentially a thin skin of cool solids on top of a big ball of extremely hot rock. On the continents, the Earth’s solid “crust” is less than 20 miles deep. At the bottom edge of the crust the temperature of the rock is at least 1,000 degrees, Fahrenheit. Deeper, it just gets hotter. As we drill for oil and gas, we come closer and closer to an energy source that makes our tiny reservoir of fossil fuels seems pathetic in comparison.
Most of that heat is generated by the decay of radioactive elements, and they are scheduled to keep on generating heat for billions of years.
Twenty miles is not far to drive in a car, but it’s a long way to drill through solid rock. The crust of the Earth is not so thick everywhere, however. The floors of our deepest oceans may be only a couple of miles from the outer mantle of 1,000-degree rock. Oil and gas wells are often that deep. And in places between the tectonic plates the crust is much thinner, or even breached. Molten rock flows out on the surface from volcanoes. Scalding steam shoots from geysers where cool surface water makes contact with the planet’s hot interior.
The total heat stored in the Earth’s interior is hundreds of thousands of times greater than our most aggressive projections of our power needs. The energy under our feet dwarfs our wildest notions for power consumption. If we could efficiently harness geothermal energy to heat steam and drive turbines, every building, vehicle and machine on Earth could be powered by geothermally generated electricity forever.
Simple applications of geothermal power are already in use in millions of buildings around the world. A few of them can draw hot air or steam directly from the Earth. Where very hot geothermal energy is near the surface — Iceland, for instance — hot groundwater can be piped into radiators and swimming pools. Reykjavik is warmed by hot groundwater pumped through radiators throughout the city, then circulated below the streets and sidewalks to keep them free of ice and snow.
Of course that sort of obvious geothermal resource isn’t available in most locales. “Ground-source” geothermal pumps are useful everywhere. They push air or liquid through underground pipes to warm or cool a building from season to season. Because the underground temperature is stable year-round — warmer than the external temperature in winter and cooler in summer — ground-source heat pumps save some of the energy that furnaces and air conditioners would use in heating or cooling. Any place in the world where you might want the inside of your home to be warmer or cooler than the outside, ground-source geothermal works. In the most conducive locations, it can reduce the consumption of energy for heating and cooling by 75 percent. Chances are there’s someone in your neighborhood already reducing their energy bill with a ground-source system.
The bigger opportunity in geothermal involves tapping high-energy geothermal sources to heat steam that drives electric turbines. Iceland, El Salvador, Kenya, the Philippines and Costa Rica — all nations with active volcanoes — already get more than 15 percent of their electricity from geothermal generating stations. The largest geothermal power plant in the world is also one of the oldest. Pacific Gas and Electric built The Geysers power field in Northern California in 1960. The network of 18 active generators has a total capacity of about 1,500 megawatts and supplies electricity to five surrounding counties, supplying about 60 percent of the power needed in the coastal region between the Golden Gate Bridge and the Oregon border.
The development of geothermal electric generation — or the lack of development — precisely illustrates our lack of vision when it comes to energy policy. Geothermal energy is virtually limitless. It is very clean in most locations. Massive amounts of power can be generated from a central plant with minimal disruption to the surrounding environment, and it easily and efficiently converts to electricity, the most portable and convenient of our energy options.
It is, in the vernacular of today’s energy policy, “capital intensive.” That means it requires a larger investment to build a geothermal generator than it does to put in another coal-fired power plant.
But isn’t that comparison based purely on how we define value? Geothermal, once tapped, is almost infinitely abundant. The generation machinery may need to be replaced, but the planetary furnace just keeps on burning. The costs associated with cleaning up the environmental consequences of extracting and burning fossil fuels or nuclear fuels are completely irrelevant to geothermal power. As we contemplate the potential costs of reclaiming defunct strip mines or reversing dangerous climate change we generally don’t go back and apply those costs to the fossil-fuel economy, but that’s where they belong. Geothermal allows many nations of the world to generate their own power without imposing the environmental costs on other nations or shipping fossil fuels around the globe.
Yes, it costs a lot more to build a geothermal electric plant than it does to build one that burns coal. But have we really measured the costs and benefits? Or do we need a new way of evaluating the choice?
Geothermal is more fair than other sources of power because it doesn’t impose the environmental damage caused by one nation’s power needs on another nation. It is almost infinitely repeatable, since once we tap into the mantle’s big, permanent fireplace, it will keep providing energy virtually forever, and it’s practically accessible from every continent.
And some would say it’s beautiful in its simple efficiency.
It’s time to recalculate its value.
Photo by Bryan Welch
 T. H. Jordan. Structural Geology of the Earth's Interior. Proceedings National Academy of Science 76 (9): 4192–4200. 1979. doi:10.1073/pnas.76.9.4192. PMID 16592703. http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=411539. Sourced November 9, 2009.
 J. Louie. "Earth's Interior". University of Nevada, Reno. 1996. http://www.seismo.unr.edu/ftp/pub/louie/class/100/interior.html. Sourced November 9, 2009.
 Ingvar B. Fridleifsson; Ruggero Bertani; Ernst Huenges; John W. Lund; Arni Ragnarsson; Ladislaus Rybach, (2008-02-11). O. Hohmeyer and T. Trittin. ed (pdf). The possible role and contribution of geothermal energy to the mitigation of climate change. Luebeck, Germany. pp. 59-80. February 11, 2008. http://iga.igg.cnr.it/documenti/IGA/Fridleifsson_et_al_IPCC_Geothermal_paper_2008.pdf. Sourced November 11, 2009.