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Geophysics professor, Southern Methodist University
Academic/Researcher, Dallas, Texas
The dry heat found in the Earth's crust deep below the United States has the potential to supply our nation's power needs for thousands of years at current rates of consumption. Of course, not all of this energy is economically recoverable, but using enhanced geothermal systems to tap into even a small portion of this resource could provide a welcome addition to our national energy supply.
Geophysicist Dr. David D. Blackwell has studied plate tectonics and Earth's internal temperatures for 40 years. Over that time, he has seen interest in geothermal energy—using the Earth's internal heat to generate power—wax and wane based on the price of conventional fossil fuels. Today, he sees geothermal's star on the rise once again, thanks in part to rising fuel prices and growing concerns about global warming, but also to the technologies he has helped develop.
"Of all the renewables, geothermal is the most uniformly distributed, and probably the most cost-effective and potentially the cleanest," says Blackwell, 66, a professor at Southern Methodist University in Dallas. But in the very next breath, he concedes that currently geothermal energy is "the least understood and least talked about" renewable energy source. As a result, Blackwell says he spends a lot of time trying to familiarize energy companies and policymakers with geothermal power.
The first step for Blackwell is explaining that geothermal power is "a lot broader than most people think about. The conventional idea is that you drill a well in the ground and water comes out hot enough to create steam used to produce electric power." Though that is how it works for some regions where heat is near the surface—the Western United States, for example—other regions do not have that geological advantage.
Enter Blackwell and his SMU colleagues, who are focused on tapping the Earth's less accessible heat energy. For instance, Blackwell recently led the development of what is known as a binary system at an Alaskan hot springs that generates 250 kilowatts of power from 165 degree Fahrenheit water, which is cooler than the ideal 400 degrees Fahrenheit or hotter required for a steam system. The binary system method uses 150 to 350 degree F water to heat another fluid that has a lower boiling point. The system then uses that fluid to run a turbine and create electricity.
Blackwell and his SMU colleagues also have resurrected an idea originally explored in the aftermath of the energy crisis of the early 1970s. This method converts existing oil and gas wells in the Gulf Coast into geothermal wells. Companies could use the waste heat from these wells to generate electricity. Blackwell noted that from 1975 to 1990 the Department of Energy provided several hundred million dollars in grants for researching the concept in the Gulf Coast. The agency even ran a demonstration power plant for a year in the late 1980s before the price of natural gas fell so low that geothermal could no longer compete.
With oil and gas at record prices, geothermal technologies are once again in the spotlight. SMU has hosted several well-attended meetings for the energy industry to discuss this geothermal production method, says Blackwell. The downside of high oil and gas prices, however, is that energy companies are "making so much money, and they're so busy right now, that they don't even want to think about these other sorts of things."
Given the fact that the energy industry is distracted, Blackwell believes the government should offer subsidies for industry geothermal research and development. "What we really need are demonstration projects," he says. "I've talked to members of Congress [about funding]," but Congress failed to authorize funding for geothermal demonstrations in a recent energy bill.
A newer technology that excites Blackwell is enhanced geothermal systems or EGS, which can take advantage of underground heat when there is no water to turn to steam. When engineers drill a well deep enough to reach underground pockets that are 350 to 400 degrees F that do not have water in them, they then drill another well and pump in water to fracture the rock and connect to the first well. This creates an artificial reservoir and the necessary steam to generate electricity at the surface. Blackwell says that EGS could be applicable anywhere in the United States as long as engineers could drill deep enough to reach hot pockets. It's that flexibility that makes Blackwell optimistic about the future of geothermal energy.