Archive, Nov. 15: Hot Rocks

Geothermal electric generation, long an underperformer in global energy, could get a boost from new deep drilling technology, according to an article this week (Nov. 13) in the Wall Street Journal. Energy analysts have been talking about the promise of tapping the hot depths of the planet to make power.

The key to maximizing hot rocks? Dig deeper.

The WSJ article reports, “A group of startups and researchers are developing technologies to expand the output of geothermal energy.” Geothermal electric generation is carbon free, using steam from water injected into underground hot, porous rocks to turn a turbine generator. It’s not a new technology but limited to where the Earth’s crust is relatively thin. The article observes, “Although the energy is virtually free of carbon emissions, its adoption has been limited because drilling gets more expensive and more difficult as it goes deeper.” Geothermal wells are generally limited to a mile or two deep.”

According to the Department of Energy’s Energy Information Administration, U.S. geothermal energy capacity is only about 2.5GW, mostly located in California and Nevada and mostly brought into service in the 198s. “Deep geothermal means hotter geothermal, and more consistently being able to distrib0ute it around on the planet,” says Dennis Whyte, the director of the Plasma Science and Fusion Center at the Massachusetts Institute of Technology.

A report this month from the Boston-based Clean Air Task Force — Superhot Rock Energy: A Vision for Firm, Global Zero-Carbon Energy – finds, “Superhot rock energy is poised for a breakthrough as a high-energy-density, zero-carbon, alwaysavailable energy source that could be commercialized worldwide in the 2030s.”

While limited today to global generating capacity of about 16 GW, a geographically confined to areas such as the U.S. Great Basin, Iceland, and East Africa, digging deeper into the hotter (400 degrees C or hotter) rocks can unlock capacities competing with conventional generation, says the report. “Several research and development (R&D) projects around the world have already drilled into superhot rock and have begun developing methods for operating in these extreme heat and pressure conditions.” The report notes.

Iceland’s Orkustofnun, the government’s energy agency, along with the country’s power companies, has drilled a deep geothermal well, suggesting that 36-MW of power could be produced from one well. The Clean Air Task Force says, “If this substantial amount of energy can be produced in dry rock at reasonable development costs, based on a preliminary analysis for CATF, superhot rock could be competitive with today’s natural gas plants at $20-35 per megawatt/hour (MWh).”

It’s not a certainty at this point. The task force report advises, “Significant engineering innovations will be required to realize the full potential of superhot rock, such as rapid ultra-deep drilling methods, heatresistant well materials and tools, and deep heat reservoir development in hot dry rock. But these are engineering challenges, not needed scientific breakthroughs.”