Meg Cichon, Associate Editor, RenewableEnergyWorld.com
March 13, 2012 | 2 Comments
Geothermal resource hot spots: Nevada, Arizona, California, and…Pennsylvania? Yes, even the east coast looks like a viable location for geothermal energy. Why? Enhanced geothermal systems (EGS) are making it possible.
Widening the Door of Potential
Traditional geothermal energy harvesting involves drilling into natural hot pockets of steam and water. These pockets can be difficult to find and locations vary widely, while the power produced depends on their size and temperature. The U.S. currently produces more than 2,800 MW of geothermal energy, about 30 percent of the world’s geothermal energy capacity, which is more than 9,000 MW installed in 24 countries.
EGS technology significantly broadens U.S. geothermal potential to a whopping 2,980,295 MW, according to Google.org. This represents a near 40-fold increase compared to traditional geothermal technology potential because EGS taps into heat located under the Earth’s crust that was previously unreachable – it can create power anywhere there is rock that is more than 150 degrees Celsius.
Okay, So How Does it Work?
The exciting aspect about EGS is that it can create geothermal potential in locations that were previously thought to be too dry or cool. Creating this system requires improving the natural permeability of rock that is caused by fractures and pore spaces between mineral grains. Simply put, EGS is a loop-cycle system that pumps water into bedrock to re-open and create fractures. The naturally heated water is then pumped back to the surface, which creates steam that is then converted into energy.
“It is providing baseload continuous power with high availability. It’s essentially emission-free and therefore carbon neutral. It has a distributed indigenous nature, so it’s not just available in the southwestern parts of the U.S. – it is extendable and scalable on a national scale,” said Dr. Jefferson Tester, professor of chemical engineering at Massachusetts Institute of Technology in a video on Google.org.
Fracturing rock may sound like it can create some disturbance or damage, but according to the U.S. Department of Energy, induced microseismic activity helps identify the extent of the fracture network in the reservoir – and in almost all cases cannot be felt at the surface due to its extremely low magnitude.
The first step in creating a successful EGS system is to identify a viable site. This is done by using heat maps and conducting extensive field exploration. Exploratory wells are then drilled to determine the extent of the resource, and if successful, an injection well in panned at the site. Water is then pumped through the injection well to create and reopen fissures in the rock – essentially creating a viable reservoir. Production wells are then drilled at key intersecting points in the reservoir to pick up the now-hot water pumped from the injection well. Once the water reaches the surface again, it heats a fluid that creates vapor to drive turbine generators that create electricity. The now-cool injection water is then flowed back through the system again, creating a continuous loop and 24-hour energy production.
Though the technology potential sounds great, it can’t be done without significant investment. Fortunately, EGS is not being ignored.
Google has pioneered EGS advancement, and in 2008 invested more than $10 million in the technology. Funding went to two companies, AltaRock Energy and Potter Drilling, and two universities, Southern Methodist University’s Geothermal Lab and Stanford University. Investment went toward developing innovative EGS technology to reduce costs and expand range, and to create mapping to understand the size and extent of the energy resource.
“EGS could be the ‘killer app’ of the energy world. It has the potential to deliver vast quantities of power 24/7 and be captured nearly anywhere on the planet. And it would be a perfect complement to intermittent sources like solar and wind," said Dan Reicher, director of climate and energy initiatives for Google.org in a written statement.
Google isn’t the only one zeroing in on EGS; the U.S. government sees its potential, as well. The President recently released the U.S. FY2013 budget request, which included $65 million for geothermal and enhanced geothermal systems – a 71 percent increase. According to the DOE:
“By 2020, the Program seeks to demonstrate that Enhanced Geothermal Systems are technically feasible by advancing critical technologies in reservoir creation, reservoir monitoring, and sustainability of sub-surface geothermal reservoirs. The Program focus is establishing EGS field sites, user test facilities, and developing game-changing reservoir creation and management technologies to expand the geothermal capacity more than 10 times from the current geothermal installed capacity of 3 GWe. The program will also aim to pursue technological innovation in finding, accessing, and developing ‘blind’ geothermal resources.”
Investment will focus on EGS technology, resource location technology, and resource assessment mapping for all 50 sates.
Who’s First Place in the EGS Race?
While much of EGS is still in research and development, there have been several successful commercial projects. A 2.5-MW EGS plant in Landau, Germany went online in 2007. Despite some minor seismic activity in 2009, the plant has been running smoothly. Australia has committed to finding and developing its vast geothermal potential. According to Primary Industries and Resources SA (PIRSA), an Australian government agency, investments between 2002 and 2014 may reach $2.7 billion, with 72 percent focused on EGS. Geodynamics has been developing a 50-MW EGS system in the Cooper Basin for years, which recently secured an additional $16.8 million in funding to drill a fourth well with hopes to establish a constant, viable source of energy at the location.
In the U.S., AltaRock is preparing a demonstration project in the Deschutes National Forest, about 30 miles south of Bend, Oregon. And EGS is also improving current geothermal projects, like the Coso facility in southern California. The 260-MW plant was able to add another 20-MW of capacity by using EGS technology.
Said Karl Gawell, director of the Geothermal Energy Association, “You’ll see EGS technology being applied in conventional plants in the next few years. The ultimate goal will be to have a project where you can literally engineer geothermal in many different areas than you can today. But it’s going to take us 10-20 years to get there. All the tools developed for EGS technology will be applied to projects coming online in the next few decades to make them more efficient, more productive and lower risk.”
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