Most green technologies gather energy above ground, but like Jules Verne, we want to take you on A Journey to the Center of the Earth. Alright, not even close to the center, but deep down nonetheless, where naturally occurring hot water can be turned into clean energy above ground.
It is estimated that the amount of heat within 30,000 feet below the earth’s surface holds potentially 50,000 times more energy than all global oil and natural gas resources combined. According to the Geothermal Energy Association, up to 6,400 megawatts of new capacity could be created from the geothermal projects under development in the U.S. But getting to that energy is proving to be a challenge.
Geothermal energy comes in a variety of forms, from residential fixtures to power a single home, to commercial plants that can power a city. Energy is usually harnessed from hot underground water or steam that naturally rises to the surface. Power plants drill holes into the rock to gain more direct access and use the hot water and steam to drive electric generators. After its use, the water can be pumped back underground to heat up anew. Power plants use different energy harnessing designs based on the type and temperature of the geothermal resource available.
Geothermal deals are heating up as it begins to prove itself as a viable energy source. For instance, Ormat Technologies recently bought Constellation Energy’s 50% share of the Mammoth Geothermal Plant in California for $72.5 million. The deal gives Ormat three power plants capable of generating 29 megawatts of power and rights to more than 10,000 acres of undeveloped federal lands.
Ormat’s home state of Nevada is a geothermal powerhouse. According to the Geothermal Energy Association, the state produces more geothermal energy than all but eight nations. Its geothermal capacity jumped from 200 to 400 megawatts during the last five years, and as many as 3,000 more megawatts are expected to be generated from developing projects. A typical coal-fired power plant can generate about 500 megawatts, though some are much larger. Nuclear power plants typically range from a 500 to 2000 megawatt capacity.
Unlike wind and solar, whose energy outputs fluctuate based on weather conditions, geothermal provides consistent base load electricity, which is the minimum amount a power utility’s customers need. It is also considered clean because it produces no greenhouse gas pollution, and renewable because the water can be reused. Last year, Obama gave $350 million in Recovery Act funding for geothermal projects.
Most geothermal plants have been located near the edges of tectonic plates, where there is a lot of geothermal activity, but companies like AltaRock Energy, which has received funding from Google, among others, are developing ways to generate steam in other geographic areas. The technology, known as Enhanced Geothermal Systems, drills into hot rocks miles below the surface and pumps cold water down to them to generate steam. The technology has been in development for a while, though there have been concerns that EGS might trigger seismic activity that could lead to earthquakes.
It’s been a very rocky road, to say the least. Last year, AltaRock abandoned its trials near a plant called The Geysers in northern California when instabilities in the rock caused the borehole to collapse. The company moved its tests to Oregon where it is working on a three-year EGS demo near Newberry National Volcanic National Monument. AltaRock’s competitor, Ram Power Corporation, purchased The Geysers in June. If the AltaRock’s Oregon demo is successful, a power generator will be placed next to the wells to test how much energy can be harnessed from them.
Photo credit: Flickr/Johann kr.