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Wanted: A Geothermal Pump That Can Handle the Heat

Aug 27, 2009 - Phil Taylor - Scientific American
geothermal pumps

IN HOT WATER: Temperatures can reach 430 degrees Fahrenheit at the depths geothermal pumps are submersed.

What will it take to develop a geothermal pump that can operate miles underground in 430-degree-Fahrenheit fluids while maintaining a steady 750 horsepower?

A pair of West Coast foundations hope they have the answer: lots of cash.

The Oregon-based Foundation for Geothermal Innovation and the California-based Lemelson Foundation last week released design criteria for a race to build the next generation of "temperature hardened" electric submersible pumps (ESP), one of a number of technologies crucial to the advancement of geothermal energy on a commercial scale. The groups are prepared to offer millions of dollars to the first firm to develop an ESP that can withstand extreme subterranean heat and pressure.

"Energy from geothermal resources is affordable and abundant," said Patrick Maloney, senior program officer at Lemelson. "But the problem to date has been harnessing it. This report will hopefully provide companies and individual innovators the parameters needed to solve a key part of that problem."

The report is a result of a meeting held earlier this year at Stanford University that brought together 20 top experts in the field, including representatives from government, academia and the private sector, to look for ways to reduce fossil fuel use through an expanded adoption of geothermal.

Pump companies, universities and inventors are being asked to compete for a $5 million prize purse to be awarded in 2015. The winning firm will also receive an advance market commitment for 100 pumps, a $75 million order designed to serve as the chief incentive to innovators.

"It is rare to find a key technical challenge that can be so clearly defined for innovators to work on," said Lawrence Molloy of FGI, which is seeking support from the Department of Energy in building an incentive package to be finalized in early 2010. "We hope that this prize can help revitalize the industry."

Similar targets for geothermal pump development have been set by the Energy Department's Geothermal Technologies Program, which has found current pump models unable to sustain flow rates under advanced geothermal conditions. While geothermal resources can reach 660 degrees, pumps capable of delivering heat from below ground are designed to operate at just 375 degrees.

Enhanced geothermal systems

The new pumps are critical for "enhanced geothermal systems," in which energy is produced by fracturing dry rock at the bottom of a deep hole and then circulating water through the cracks to generate steam. In contrast, today's geothermal projects use hydrothermal systems that tap naturally occurring water deposits to provide geothermal heat.

While hydrothermal potential is estimated to be about 30,000 megawatts, the potential for EGS is greater than 500,000 megawatts, or about half of the current generating capacity of the entire United States, according to a 2008 report from the U.S. Geological Survey.

A seminal 2007 study from the Massachusetts Institute of Technology found that wide-scale commercial deployment of EGS reserves could power more than half of American homes by midcentury. And unlike intermittent wind and solar power, geothermal is available around the clock and requires much less real estate to develop.

"Geothermal energy from EGS represents a large, indigenous resource that can provide base-load electric power and heat at a level that can have a major impact on the United States while incurring minimal environmental impacts," according to the MIT study. "Further, EGS provides a secure source of power for the long term that would help protect America against economic instabilities resulting from fuel price fluctuations or supply disruptions."
Along with better drilling techniques and heat transfer liquids, companies hoping to develop EGS will need a pump that can reliably and affordably bring subterranean heat to the surface.

"Electric submersible pumps have been used for decades by people who have wells, but most people's drinking water isn't hot," said Maria Richards, program coordinator for Southern Methodist University's Geothermal Lab in Texas.

Surface pumps are capable of pumping liquids to geothermal depths, but they lack much of the power of submersible pumps and are less efficient to operate. And since geothermal efficiency is tied to both temperature and flow rate, it pays to have submersible pumps that can be installed in the well itself, nature's so-called pressure cooker.

"It's not that there's not the pump technology out there, it's just too expensive," Richards said. A viable ESP would need to have the right types of steel, lubricants and glues that can hold up long-term in changing temperatures and pH levels.

The Lemelson report notes three companies that currently offer electric submersible pumps -- Baker Hughes, Schlumberger and the Woods Group -- but none of the models is robust enough to handle the extreme temperatures and pressures of EGS, said Karl Gawell, executive director of the Geothermal Energy Association, a Washington, D.C., trade group.

"I'm sure all the people building geothermal power plants are very interested in equipment like this," Gawell said, noting that electric submersible pumps are just as useful in hydrothermal applications.

But the availability of hydrothermal reserves -- the low-hanging fruit of the geothermal world -- has been greatly reduced as companies have been snapping up prime exploration rights in Nevada and California. Gawell said successful deployment of the electric submersible pump could greatly expand opportunities for EGS.

"The idea of offering a prize is great," he said. "You're talking about human ingenuity. The heat is there; what we need to do is apply the human brain."

Reviving geothermal innovation

Until recently, energy companies have looked to places like the High Plains for wind and the sun-scorched Southwest for solar, while paying less attention to the geothermal energy simmering thousands of feet below the Earth.

Geothermal today accounts for just over 3,000 megawatts of U.S. generation, compared with 28,200 megawatts of capacity for wind-generated power and 9,183 megawatts of capacity for solar.

But that trend could change after major cash infusions from the federal government and the private sector to spur geothermal production.

President Obama's economic recovery package offered $400 million to help the geothermal industry overcome the biggest technical barriers to harnessing hotter and deeper geothermal reserves. That figure comes on top of $50 million in fiscal 2010 funding the White House requested for DOE's geothermal research and development office, a program that was nearly eliminated under the Bush administration., the Internet search engine's philanthropic arm, last year gave just under $11 million to universities and private drilling companies looking to develop the next generation of geothermal projects.

One such project is already under way. In Northern California, AltaRock Energy hopes to become the first of many developments to produce geothermal energy by fracturing rock at the bottom of a deep hole and then circulating water through the cracks to generate steam.

The AltaRock project received $6.25 million in financing late last year, but has experienced technical difficulties drilling to its target depth of 12,000 feet.

Complicating matters, DOE and the Bureau of Land Management told the company that it would not be allowed to fracture rock until the department finishes safety reviews to ensure the project will not cause earthquakes like similar projects in Basel, Switzerland.

Other companies seem undaunted by AltaRock's trouble. Last month's competitive auction of lease parcels for geothermal energy in California, Nevada and Utah generated about $9.1 million in revenue for the Bureau of Land Management, the agency reported.

A 2008 environmental impact statement estimated a potential for 5,540 megawatts of new electric generation capacity from geothermal on BLM lands in Western states and Alaska by 2015 through 111 new geothermal power plants, with an additional 6,600 megawatts from another 133 plants by 2025.

Reprinted from Greenwire with permission from Environment & Energy Publishing, LLC., 202-628-6500


Updated: 2016/06/30

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