UNIVERSITY PARK, Pa. — A group of Penn State researchers is one of 18 teams selected to receive $1.1 million in funding from the U.S. Department of Energy (DOE) Advanced Research Projects Agency-Energy (ARPA-E). The two-year cooperative agreement supports early-stage research and development to advance low-cost, low-emissions production of geologic hydrogen, which is produced naturally in Earth’s subsurface and could contribute to a more sustainable, energy independent future.
The team, led by Shimin Liu, the George H., Jr. and Anne B. Deike Chair in Mining Engineering and professor of energy and mineral engineering at Penn State, will work to better understand how to explore and potentially extract geological hydrogen from its subsurface reservoirs. Engineering the production of subsurface hydrogen could potentially unlock substantial resources for clean energy and lead to the decarbonization of our most energy-intensive industries, according to the DOE.
Hydrogen is the most abundant element in the universe but is usually found in compound form. It can be extracted from a variety of sources, including water, fossil fuels and biomass but this requires energy and can release carbon dioxide into the atmosphere. Geologic hydrogen — or natural hydrogen — is pure hydrogen, generated through water-rock interactions deep in the Earth’s subsurface without active stimulation, the researchers said.
Hydrogen can be classified by color, defined by carbon emissions associated with its production process. Hydrogen extracted from subsurface sources is known as white or orange hydrogen. White hydrogen is produced through a passive extraction method that generates low volumes with low flow rates. Active extraction, using subsurface stimulation and reservoir creation and management, produces gas referred to as orange hydrogen, according to the researchers.
“Although orange hydrogen has a significant potential for hydrogen harvesting, our understanding and characterization of its production, its impact on in situ geochemical and geomechanical behaviors, and the resulting evolution of reservoir flow behavior and associated geo-environmental risks remain largely unknown,” Liu said.
These knowledge gaps hinder the future large-scale hydrogen production from subsurface formations, according to the researchers.
“Until now, hydrogen has never been treated as a primary energy resource,” Liu said. “Our intent to artificially engineer a geomechanical system that can sustain hydrogen production has never been done before. So, at each step, we will need to assess, evaluate and develop a new process or technology.”
Derek Elsworth, the G. Albert Shoemaker Chair and Professor of Energy and Mineral Engineering and Geosciences in the John and Willie Leone Family Department of Energy and Mineral Engineering and co-principal investigator (co-PI), summed up the project as “high risk, high reward.”
“Beyond being an energy source, hydrogen is also attractive for use as a grid leveler — integrating renewables into the electricity grid,” Elsworth said. “The second attraction is that hydrogen can use a lot of existing infrastructure. You can potentially transport it using existing natural gas pipelines that are already available.”
Geologic hydrogen is formed through a process called serpentinization — where iron-rich rocks, such as olivine, in the Earth’s crust react with water and release hydrogen as a byproduct of chemical reactions.
The researchers propose leveraging the serpentinization process in peridotite, a type of rock that contains olivine as its primary mineral. The team plan to use an inert gas dynamic fracturing technology to inject carbon dioxide into a peridotite formation to increase its permeability and reactive surface area. Then, they plan to stimulate the formation with a carbon-rich solution to induce — and sustain — serpentinization.
“It's similar to what’s done in developing geothermal reservoirs in that you're fracturing the rock, but this technique is slightly different and it's more localized,” Elsworth said. “The challenges will be to create a reactive surface area at the correct depth, with the right regents, to have the right reactions, and then recover a high yield of hydrogen in an environmentally safe way. It’s not being done now, and it hasn’t been done before.”
According to Liu, this approach would require novel technology.
“It will be continuously changing the geochemical equilibration to promote and maintain production at an acceptable level,” Liu said. “We want to make sure that we maximize hydrogen production while mitigating induced seismicity.”
Over the next two years, the team aims to develop their innovative technology using a multi-stage approach. The team will first identify potential reservoir sites by cataloging locations across the U.S. rich in olivine peridotite — they suspect to find the largest quantities in California and near the Midcontinent Rift.
Ang Liu, assistant teaching professor of energy and mineral engineering and co-PI, explained that identifying the ideal reservoir location is a complex evaluation.
“We will consider the safety and environmental impacts as well as determine if the area is market accessible and in close proximity to potential customers and the necessary infrastructure,” Ang Liu said.
The researchers will conduct additional tests and use models to characterize micro-seismicity, changes in permeability and how fractures propagate in core samples before moving to pilot-scale experiments at a local mine. According to the researchers, the goal is to provide as much foundational data as possible for analytical models to create a framework for sustained, field-scale reservoir management. The data could also help predict and prevent induced seismic events.
The last step will be a techno-economic analysis that calculates all the projected costs for a full-scale operation and assesses the feasibility of bringing the technology to market.
“The imagination and creativity and the skill sets of everyone contributing to this project make research like this possible,” Elsworth said. “This is blue-sky thinking. This hasn't been done before. But if it does work, then the reward is potentially quite high.”
The schedule is tight, according to Liu, but the team is ready.
“I think we have the right metrics to take on this challenge, contribute a significant body of knowledge, and, hopefully, add to the great geoscience, mineral and energy research legacy at Penn State that helped us receive this exciting project,” Liu said.
The project is funded through ARPA-E’s Exploratory Topic H: Subsurface Engineering for Hydrogen Reservoir Management, which focuses on technologies relevant to the extraction of geologic hydrogen.
“Using carbon dioxide to deliver reactants and engineer the subsurface for the recovery of hydrogen is an exciting prospect, potentially transforming our understanding of this critical energy resource,” said Doug Wicks, ARPA-E program director. “I look forward to following the team’s progress toward this goal.”