Texas, USA — The case for a low-carbon economy grows stronger with each new extreme weather event that threatens the global food supply.
But the world is still searching for the next-generation resources that can generate electricity at high efficiencies with little CO2 emissions and no nuclear waste. Fugitive methane leakers need not apply for this elusive panacea.
The Obama Administration hopes enhanced geothermal systems (EGS) will play a major role in the president’s goal for 80% clean energy by 2035. EGS also has the potential to bridge the divide between renewable energy and fossil fuels by employing the same hydraulic fracturing technology that has been controversial in extracting oil and gas from shale formations.
Obama requested $61.5 million – or 60% of all geothermal program funds in the U.S. Department of Energy – for EGS research in fiscal year 2012.
“The U.S. Department of Energy believes that enhanced geothermal systems have enormous potential to provide renewable baseload energy to heat and power homes and businesses,” said DOE spokesman Tom Welch.
Australia’s government and geothermal industry have already spent hundreds of millions in EGS proof-of-concept projects. Brisbane-based Geodynamics plans to begin producing power at a 50-MW EGS plant next year.
Overcoming the Earthquake Issue
EGS entails drilling thousands of meters underground into hot, dry rock and hydraulically fracturing the formations to engineer fluid reservoirs into which millions of gallons of water can be pumped. This creates steam that powers turbines.
EGS has been on shaky ground in recent years because it comes with a major caveat: Fracturing hot rock can trigger small earthquakes, which industry and government refer to as “induced seismicity.” EGS showed promise during the last decade, but research hit a snag as projects caused small earthquakes in Europe, including a 3.4-magnitude tremor near Basel, Switzerland, in 2006.
“It took the industry years to finally acknowledge that it causes seismicity,” said Hamilton Hess, an environmental activist who has opposed EGS development near the Geysers geothermal field in California.
International leaders have renewed their interest in EGS and its low-carbon output as global warming appears to worsen. A 2006 MIT study estimated EGS could provide about 100,000 MW of electricity capacity, about 5% of the U.S. power supply, over the next 50 years. The National Renewable Energy Laboratory says EGS could provide up to 16,000 GW of capacity in the U.S.
“You could literally do hundreds or thousands of megawatts, but the limiting factors are availability of water and (the pace of the) public permitting process,” said Don O’Shei, chief executive officer of AltaRock Energy, a key player in the DOE’s EGS research.
AltaRock’s project at Newberry Caldera in Oregon is the largest of at least four EGS proof-of-concept efforts the DOE is funding in the Western United States.
Australia’s Great Hope
The Australian Geothermal Energy Association (AGEA) expects that country will build up to 2,400 MW of installed EGS capacity by 2020.
Australia has no major volcanic regions, yet the country has made a major investment in EGS by drilling into hot, dry granite formations up to 4 km underground. The AGEA and World Wildlife Fund (WWF) have said EGS could meet the country’s energy needs and dramatically reduce carbon emissions.
Geodynamics’s 50-MW EGS power plant, located in the Cooper Basin of South Australia, will use four injection wells and five production wells. Geodynamics’ exchangers will transfer heat from a high-temperature well to a binary fluid in a closed loop. The binary fluid will flash steam to power turbines.
The company says on its website that it can scale the project to 500-MW by installing ten 50-MW modules by 2016. The government permitted the project in spite of a magnitude 2.7 earthquake that occurred during early-phase drilling in 2003, according to industry experts.
Newberry Caldera Demonstration
The DOE awarded AltaRock Energy and Davenport Energy LLC a $21.45 million to develop an EGS demonstration project outside the Newberry Caldera near Bend, Oregon. AltaRock could begin fracturing rock this fall on a series of dry wells.
“On the surface, enhanced geothermal shows incredible potential but, like everything else, details determine whether it’s good enough or green enough,” said David Stowe of the Sierra Club’s Juniper Group.
Stowe’s group is primarily concerned with preserving the integrity and quantity of water resources in the dry region.
“Our water resources are pretty much spoken for,” Stowe said.
O’Shei said the companies have negotiated water rights with a regional water bank. An independent hydrologist review estimates the demonstration project will use up to 142 million gallons of groundwater from the shallow aquifer beneath the western flank of Newberry volcano.
For now, most of the international concerns about EGS are focused on induced seismicity. O’Shei said AltaRock’s technology will use smaller fractures away from fault lines to minimize seismic activity. The DOE and International Energy Agency (IEA) have developed a protocol to mitigate seismicity and public concerns. In the latest protocol, published in May 2011, the agencies argue that low-magnitude seismicity is a small price to pay for the carbon-reducing benefits of EGS.
“It is written from a risk-based perspective as opposed to hazard,” DOE Press Secretary Stephanie Mueller said via e-mail. “It is based on accepted ground vibration standards used in the civil and structural engineering community rather than earthquake magnitude.”
EGS supporters say those earthquakes (usually less than magnitude 3.0) are rarely perceptible to people who live in rural areas within 10 km of the production sites.
“I won’t make light of seismicity, but tornadoes are a greater threat than these micro-seismic events,” said Curt Robinson, executive director of the Geothermal Resources Council.
“It’s more than a nuisance,” Hess said. “Earthquakes are a constant problem here.”
He said about 2,800 residents in the mountain communities of Cobb and Anderson Springs experience several earthquakes of 2.0 or greater every week. Calpine Energy and other companies maintain geothermal reservoir levels by importing municipal wastewater through a 29-mile pipeline. A Calpine spokeswoman did not return calls or e-mails seeking comment.
While the process does not technically qualify as EGS, Hess said, the related seismic activity demonstrates the potential impacts of pumping vast amounts of water onto subsurface rock with temperatures exceeding 400 degrees F. Calpine uses at least 8 million gallons of water daily at its Geysers sites, Hess said. The Geysers generates enough electricity to power a city the size of San Francisco.
Even if the industry does overcome objections to seismicity, it remains to be seen whether EGS can be developed economically in North America. O’Shei said AltaRock ended its Geysers project when the company was unable to deepen an existing well because the fibrous geology was “the consistency of oatmeal.”
Newberry could be the ideal location for EGS, however. For decades, the government and geothermal developers have been unable to tap into a conventional geothermal resource near the dormant Newberry volcano in spite of the plentiful heat. AltaRock will fracture a set of dry exploration wells that Davenport Energy drilled searching for a conventional reservoir in 2009.
“It helps that these wells are already drilled,” O’Shei said. “We just have to fracture them now.”
If permits are approved this summer, AltaRock could begin fracturing the site by September or October.