The Department of Energy just tossed out $84 million to fund it. Google’s Clean Energy 2030 plan champions it. And an MIT report estimated it could fuel the country for centuries. Geothermal energy: It’s clean, renewable, and plentiful. Great. So, um, what is it exactly?
What geothermal is
First, it’s not a home heating and cooling system. Ground source heat pumps, which are an efficient and low-carbon way to heat and cool your home, are often referred to as “geothermal” systems. Technically, they do fall under the rubric of “geothermal” (as in heat (“therm”) from the ground (“geo”)). But for now, we’re going to focus on industrial systems and leave domestic ones until next week.
Industrial geothermal power plants take heat out of the ground and convert it into electricity, which then can be used like any other electricity. Traditionally, plants have used heat from sources close to the earth’s surface: geysers, underground hot water or volcano-heated rocks. Now, however, a new system, called “enhanced geothermal” plans to drill deep into the earth (four to ten kilometers) and extract heat from rocks warmed by the earth’s core. This video from Google.org offers a succinct explanation of how it works:
Where it’s being used
Traditional systems have only been located in places where heat is generated near the earth’s surface, namely places near the merging of continental plates: Iceland, Indonesia and the western United States. The U.S. is currently the world leader in such geothermal power plants, with 29 such systems in places like The Geysers north of San Francisco, the Salton Sea in southern California and assorted locations in Nevada generating enough power for 1.2 million homes.
Enhanced geothermal systems, however, aren’t dependent on surface heat. In theory, they could be located anywhere, which is why some scientists, including new Secretary of Energy (and former director of the clean energy-researching Lawrence Berkeley National Laboratory) Steven Chu, are excited about their potential as an alternative energy source.
Potential energy production
A 2006 MIT report says that, in return for a $1 billion, 15-year investment in research and development, geothermal could provide 100 Gigawatts of energy — or enough to power 100 million homes — within 50 years. In all, MIT estimated that the total available energy from geothermal is 2,000 times what the United States used in all of 2005.
Since it doesn’t use fossil fuels, geothermal energy is essentially carbon-free.
Why it hasn’t taken off yet
By now you’re probably wondering, if geothermal’s so great, if it can provide that much power, with almost no carbon emissions, how come we’re not using it already?
Good question. Geothermal has taken off in places where the heat is located near the surface. Enhanced geothermal systems, however, are still experimental. The private sector has naturally been reluctant to dive in without guarantees the thing is going to work. Which is why government funding is so important. The new money the Department of Energy has just allocated could be just the starter dough this industry needs.