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Geothermal Energy: So Hot Right Now

If renewable energy sources were to have a popularity contest, wind and solar would win. But geothermal energy is edging in on their turf.

If renewable energy sources were to have a popularity contest, wind and solar would win. But geothermal energy, the same force of nature that gave humanity hot springs and Yellowstone’s Old Faithful, is edging in on their turf.

In the past few years, projects that would more than double the United States’ capacity for geothermal electricity production have gotten underway, and just last week, the Department of Energy just announced $70 million in new funding for geothermal research. In East Africa, Kenya is planning on generating a third of its country’s electricity using geothermal energy. Even Pippa Middleton, a trend-setter if there ever was one, is getting in on the ground-floor: She recently took a job at a geothermal firm in Britain.

Geothermal’s popularity is growing for a reason: It’s one of the cleanest energy sources out there. In geothermal plants, water or steam heated by the Earth’s core is brought to the surface to drive electricity-generating turbines. Depending on the technology used, after the plants are set up, some produce no emissions whatsoever, and others nearly none. Geothermal is also an infinitely renewable energy source, practically speaking. One day, the core will stop producing heat, but at that point, we’ll either be long gone or have bigger problems to deal with.

There are two ways to tap into geothermal power. On a small scale, it can heat or cool any building, through systems that run water through underground pipes. Iceland, for instance, heats almost all of its buildings this way. In cold weather, the water picks up heat from the ground and brings it to the surface; in hot weather, the reverse happens. These systems use some power to pump the water through the pipes, but since they’re not actively heating or cooling it, they’re far more energy efficient that other temperature-modifying systems.

But it’s on a large scale that geothermal energy could revolutionize the power system. In the past, geothermal plants have been built in places with naturally occurring hot water reservoirs, the sort of places where hot springs and geysers spring up. These areas tend to be at the edges of tectonic plates, where the planet’s crust is thinner; any place that’s known for volcanoes or seismic activity probably qualifies. California, for instance, accounts for more than two-thirds of geothermal electricity production in the United States, which has more geothermal capacity than any other country.

Natural reservoirs are not common enough to boost geothermal past wind, solar, or hydroelectric power as a renewable energy source. The earth’s crust, however, is hot all over the planet, and governments around the world are working on technology that would make geothermal energy accessible even to countries not known for their hot springs. These “Enhanced Geothermal Systems” essentially create water reservoirs by making cracks in a section of dry rock, pumping water into them, and bringing it back to the surface piping hot. Right now, these systems are too expensive to be commercially viable. The other big draw-back of geothermal energy is that drilling in the wrong place can induce earthquakes, and scientists are still working to figure out how to minimize those risks or avoid them altogether.

But funders such as the Department of Energy are hoping these problems can be overcome within the next decade, because the potential of geothermal is enormous. A 2008 report by the Massachusetts Institute of Technology estimated that the extractable energy from these systems would be 2,000 times the amount of primary energy consumed in the United States in 2005. And the investment needed to solve these problems is tiny compared to the investment needed to make other clean energy projects work: Professor Jeff Tester, who worked on the MIT study, has pegged the total cost at between $600 and $800 million, which is less than it would cost to build one clean-coal plant.

Photo courtesy of flickr user Chris Beckett

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