Geothermal energy beneath the Earth’s surface, literally below our feet, has enough potential to meet the demand for sustainable zero-carbon electricity in the coming decades and beyond.
How much energy is down there and for how long?
According to the U.S. Department of Energy’s ARPA-E geothermal project, AltaRock Energy, a mere 0.1 percent of the heat content of Earth could supply humanity’s total energy needs for 2 million years.
It seems, then, like a good idea to go get it.
The question is: what’s the most efficient way to do so?
Recently, a geothermal research team at the University of Oklahoma believes they found an answer.
It’s called SoonerDrill.
It is a 17-foot drilling rig, designed by Orkhan Khankishiyev, a master’s student at OU.
“The primary goal of this project is to test and validate many of the alternate technologies that can fit for deep hard rock drilling,” said Saeed Salehi, an associate professor of petroleum engineering who led the project.
Geothermal resources are reservoirs of hot water located at varying temperatures and depths below the Earth’s surface. In the United States, most geothermal reservoirs are in the western states.
SoonerDrill was constructed at the school’s Well Construction Technology Center and sponsored by DeepPower Inc, a new startup with the mission to bring geothermal energy from deep earth to market. New technologies are needed to find such energy because present drilling technologies are limited to certain depth and formation temperatures. SoonerDrill will help assess what materials and designs are best suited to access such challenging geological conditions.
DeepPower has invested more than $1 million in the project.
Specifically, the drill is a nondescript black box made of welded steel at the rig’s base. The chamber will contain large cubes of rock, such as granite, and Salehi said the rig will allow the team to manipulate heat and pressure inside the box to simulate the environment that drillers will encounter deep below ground.
Addressing Challenges of Geothermal
Energy from geothermal finds it way to the Earth’s surface in three ways: volcanoes, hot springs and geysers.
There are challenges, though, in procuring it all.
Geothermal plants need to be built in places where the energy is accessible, which means that some areas are not able to exploit this resource.
While geothermal energy does not typically release greenhouse gases, there are many of these gases stored under the Earth’s surface which are released into the atmosphere during digging.
Accessing geothermal energy runs the risk of triggering earthquakes, due to alterations in the Earth’s structure as a result of digging.
Geothermal energy is an expensive resource to tap into, with price tags ranging from around $2-7 million for a plant with a one-megawatt capacity.
Lastly, to keep geothermal energy sustainable, fluid needs to be pumped back into the underground reservoirs faster than it is depleted.
Salehi believes the project will lead to advantages such as faster drilling (rate of penetration), lower finished cost at total depth and supplying more geothermal energy from a pair of wellbores. Presently, SoonerDrill is semi-automatic, requiring some human control to operate. Future phases and development will make it fully automatic.
“Taking the human factor out of the operations, we will eliminate the risk of human errors and optimize the drilling operations,” he said.
As noted, one of the challenges faced in multiple attempts to tap geothermal energy is the need to drill through hard rock formations at elevated temperatures that can reach 800 degrees Fahrenheit.
“This presents unique challenges, including the need for specialized drilling equipment and techniques capable of maintaining stability and functionality at abrasive downhole conditions,” said Salehi.
Harnessing these super-hot underground resources holds immense potential for clean and sustainable power generation.
It isn’t just about the drill, though.
“Ongoing research focuses on identifying high-temperature geothermal reservoirs through advanced subsurface mapping techniques, and engineers are developing innovative drilling technologies to access deeper and hotter regions, while enhancing power plant designs and operation,” said Salehi.
Considering these extreme temperatures and pressures, corrosion-resistant materials and efficient heat transfer processes, there is still much work to do. Figuring it out in real dollars what the benefits will be in productivity through such new technology is difficult to calculate, Salehi said.
Nevertheless, the potential is there.
“The aim is to unlock the full potential of super-hot geothermal resources and establish geothermal energy as a reliable and sustainable power source for the future,” he said.
The modeling results of the technology so far indicate that significant increase can be achieved in rate-of-penetration and the speed of drilling – thus decreasing the drilling time and cost.
“By pushing the boundaries of drilling technology, we aim to develop innovative approaches that increase drilling speed, thereby optimizing the efficiency and feasibility of accessing these valuable geothermal resources,” he explained.
Part of a Larger Plan
As with all new technology and the quest for sustainable energy, there is no silver bullet in accessing geothermal. As promising as SoonerDrill is, it’s just one step toward a robust energy future.
“We must embrace all the options till we make new technologies such as geothermal ready in the market,” Salehi said.
The potential can catalyze a profound transformation.
“As the search for sustainable energy intensifies, the ability to tap into deep super-hot geothermal resources would provide a significant boost in our efforts toward achieving net-zero carbon emissions,” he added. “The widespread adoption of geothermal energy could reduce our dependence on fossil fuels, diminish greenhouse gas emissions, and accelerate the transition towards a cleaner, greener future.”