The “sun beneath our feet” is looking more viable as companies and investors take up the challenge.
A possible solution to the clean energy crisis may be at our fingertips, or more accurately, under our feet. The molten core of the Earth is roughly as hot as the surface of the sun, over 10,800°F (6,000°C). This “sun beneath our feet” is continuously replenished by the decay of naturally occurring radioactive elements at a flow rate of roughly 30 terawatts, almost double that of all human energy consumption.
The process is expected to continue for billions of years and the Advanced Research Projects Agency-Energy (ARPA-E) estimates that “just 0.1% of the heat content of Earth could supply humanity’s total energy needs for 2 million years.” In other words, the center of the Earth could supply enough energy for many generations of humans.
Geothermal energy is older than the ancient cultures of the world
Unlike other clean energy options, geothermal energy can provide a constant supply of electricity whether the sun is shining or the wind is blowing. Also, geothermal energy is relatively low-carbon and has a smaller land footprint than many other renewable energy sources.
Geothermal energy is as old as the ancient cultures of Aboriginal Australia, China, Japan, and Rome. It is energy that occurs naturally when heat breaks the Earth’s surface in the form of hot springs, geysers, and steam vents near volcanic activity. That’s one type of geothermal energy. Another type is Enhanced Geothermal Systems (EGS), which are human-made versions of hot springs with wells on average 4.3 miles (6.9 kilometers) deep. EGS involves creating fractures in hot rock formations to allow for water circulation and heat extraction.
Unlike other clean energy options, geothermal energy can provide a constant supply of electricity whether the sun is shining or the wind is blowing.
While EGS sounds like a dream come true, there are challenges still to work out. J. Gary McDaniel, CEO of Geothermal Technologies, Inc. writes in the winter edition of Energy Global magazine that EGS may be unsuccessful for the following reasons:
- The water pumped into the injection well sometimes finds its way into the hot dry rock’s (HDR’s) natural fracture system and disappears;
- The water that does make its way to the production well leaches minerals from the rock, corroding pipes and causing numerous maintenance and operational problems;
- The basement rock is very dense and cannot be adequately imaged using existing technologies so drillers are hoping to hit a suitable fracture system;
- Rock is an insulator, not a conductor, so the geothermal resource is quickly exhausted as the rate of heat extraction exceeds the rate of natural heat recharge (conduction through the rock).
See our related interview with Fervo Energy’s Gabe Malek
Drilling can also be a challenge. Some drills melt due to the high temperatures, but that can be overcome, as evidenced by Houston-based Fervo Energy. The company recently announced that it is the first to use newer oil and gas techniques such as fracking and horizontal drilling to generate electrical power. Fervo says it is using horizontal drilling, multistage completions, and fiber-optic sensing to reduce costs and increase its reservoirs’ reliability.
Other companies have abandoned EGS and opted for closed-loop designs. The approaches differ but the basic premise involves circulating a heat-exchange fluid in an underground closed-loop system to harvest the heat from the geothermal resource. There is no loss of water, no leaching or corrosion, and imaging is unnecessary. Closed-loop system companies include Eavor Technologies, GreenFire Energy, and Sage Geosystem.
One other type of geothermal energy currently in use involves mining heat from hot sedimentary aquifers (HSAs), which are globally abundant, unlike naturally occurring sources that are limited. HSAs solve the loss of water problem evident in EGS because water doesn’t disappear. McDaniel said the fractures help with the circulation of water within the aquifer and thus bring water/heat to the system.
Many geothermal energy companies are focused on state initiatives because the permitting process is easier. In the U.S., drilling on federal land is subject to extensive environmental regulations and requires in-depth review.
“The water in the aquifer is at chemical equilibrium with the surrounding sandstone — eliminating the water leaching/corrosion problem,” McDaniel said. “The composition of the water is constant and predictable, allowing for proper metallurgy selection in the facility’s design.”
Because these reservoirs consist of sandstones, they can be imaged with 3D seismic, passive seismic, and electromagnetic imaging technologies. Lastly, HSAs allow for both convective and conductive heat transfer.
A few companies such as Geothermal Technologies, Inc. and DEEP are focusing on HSAs and fine-tuning the technology.
Earlier this year, Geothermal Technologies, Inc. filed for drilling permits with the Division of Water Resources in the State of Colorado to generate utility-scale electricity in the Denver-Julesburg (D-J) Basin in Colorado.
“Our GenaSys technology promises to make geothermal baseload power both low in cost and truly scalable – locally, regionally, and globally,” said Geothermal Technologies, Inc. President and COO Jim Hollis. “We plan to begin by constructing a small 5 MW power plant in the D-J basin and then scale from there.”
Slow permitting is one reason geothermal energy hasn’t taken off
Many geothermal energy companies are focused on state initiatives because the permitting process is easier. In the U.S., drilling on federal land is subject to extensive environmental regulations and requires in-depth review. The permitting timeline could be 10 years and it’s extremely difficult to get funded under that scenario, according to Jamie Beard, founder of the Geothermal Entrepreneurship Organization as well as the founder and editorial director of Project Innerspace, a nonprofit that aims to make the production of clean, geothermal energy possible anywhere in the world by 2030.
Geothermal energy is “substantially underfunded,” according to Beard. For geothermal to accelerate, it needs a government office and big investments.
Beard said in a recent Volts podcast it’s better to use state and private land because permitting in those places, especially those that are already friendly to the oil and gas industry, could take 12 months or less. One project in Texas was permitted in a matter of months. The slow permitting process is one reason geothermal energy hasn’t taken off the way other clean energy industries. Another is money.
At this stage, the geothermal industry doesn’t have hundreds of millions that the oil and gas sector has to develop best-in-class drills. Geothermal energy is “substantially underfunded,” according to Beard. For geothermal to accelerate, it needs a government office and big investments. Right now, federal allocations are to the tune of $200 million, not $2 billion, and that’s the sort of money geothermal needs, Beard added.
“Geothermal is no longer a niche play. It’s scalable…”
From Beard’s perspective, the way to scale geothermal is to leverage the oil and gas industry because these companies already have the equipment and the labor. The skills are “100% transferable” from oil and gas because drilling is drilling, she said. In fact, all the oil and gas major companies have a geothermal energy team. The motivation is that oil and gas is a dying industry, but also geothermal could be a real moneymaker.
“Geothermal is no longer a niche play,” said Vik Rao, former chief technology officer at Halliburton, in the geothermal blog Heartbeat. “It’s scalable, potentially in a highly material way. Scalability gets the attention of the [oil services] industry.”
If the oil and gas industry looks at geothermal as an exciting future business model, the industry could finally get the inspiration and funding it needs to truly transition from polluting to clean energy. That’s something that can’t happen fast enough.
Featured photo: GreenFire Energy