Hydrogen is among the most abundant elements present in the universe. It consists of only one proton and one electron and can be used to store and deliver energy for large-scale applications.
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The Office of Energy Efficiency & Renewable Energy classifies hydrogen as an energy carrier rather than a source, capable of storing and delivering a substantial amount of energy. It can be utilized in fuel cells to produce electricity, as well as to provide power and heat. The naturally occurring hydrogen can serve as the main asset in battling climate change and global warming.
Natural Hydrogen: An Important Resource in Its Early Days
Natural hydrogen may not only be clean but also renewable. Unlike the millions of years required for organic deposits to transform into oil and gas, natural hydrogen is continually generated when underground water reacts with iron minerals under high temperatures and pressures.
However, it is still in the early stages of exploration as scientists work to comprehend its formation, migration, and the key question of whether it accumulates in a commercially viable manner.
Limitations of Natural Hydrogen
Despite being carbon-free, hydrogen faces challenges as an energy source. A kilogram of hydrogen holds as much energy as a gallon of gasoline but occupies more space at ambient pressures. Pressurized tanks increase capacity but add weight and costs.
Liquefying hydrogen is expensive. These storage challenges, coupled with the lack of infrastructure, contribute to the dominance of batteries over fuel cells in the electrification of cars.
Similarly, for heating, electric heat pumps are considered more practical than hydrogen furnaces. However, a significant portion of the world's energy demand remains challenging to decarbonize with electricity, emphasizing the need for investment in natural hydrogen exploration.
Reserves of Hydrogen
Hydrogen constitutes 0.14 % of the Earth's crust and approximately 10 % of the human body by mass. Recent discoveries have revealed substantial deposits of natural hydrogen in the Earth's mantle.
Ongoing exploration and drilling worldwide suggest the potential for a significant supply of clean hydrogen. Different colors, such as gold and white, are used to categorize this natural hydrogen, distinguishing it from other sources based on carbon emission intensity, like brown or green hydrogen.
Earth generates natural hydrogen at a significantly faster rate than it produces hydrocarbon fuels. The continuous regeneration of gas extracted from deposits through serpentinization processes challenges the notion that the size of an in-ground reservoir limits the amount of available natural hydrogen for sustaining the future hydrogen economy.
Efforts of the United States Geological Survey (USGS) for Extracting Geologic Hydrogen
To comprehend the potential for hydrogen accumulation, scientists require an improved geologic model, focusing on how hydrogen forms, its origin within rock layers, and its distribution.
The petroleum system, a well-established conceptual model employed by petroleum geologists, has proven effective in guiding oil and gas exploration and providing accurate assessments of undiscovered petroleum resources. This model can serve as a foundation for developing a similar understanding of natural hydrogen occurrence.
The USGS has a dedicated team focused on mapping out the regions of the U.S. that have the highest probability of containing natural hydrogen. Utilizing a hydrogen system model, the team maps the distribution of various components within the hydrogen system and evaluates their alignment. This enables the team to generate an initial estimate of the potential for geologic hydrogen across the nation.
Two key regions in the United States exhibit favorable geology for the generation of substantial hydrogen volumes. The first area extends along the Atlantic coastal plain, characterized by a band of iron-rich rock layers beneath the ocean floor. The second region in the central U.S. is linked to rock formations from an ancient rift event, the Midcontinent Rift, which occurred around 1.1 billion years ago.
Exploration Techniques for Natural Hydrogen
The exploration of geologic hydrogen resources is expected to utilize similar strategies and technologies employed in petroleum exploration, with additional elements borrowed from mineral and geothermal resource exploration.
Due to the potential of hydrogen to induce brittleness in steel, the production of hydrogen trapped in reservoirs may necessitate the use of slightly different materials. However, existing drilling and completion equipment used in natural gas development can still be applied.
Unlike natural gas fields, certain gases in natural hydrogen fields could be renewable due to the rapid rate of hydrogen generation through water reduction. Some experts even propose that traditional reservoirs, traps, and seals may not be required for geologic hydrogen production.
Instead, they suggest tapping into rocks that are actively generating hydrogen or have hydrogen migrating through them, extracting the gas as it is being generated. There are even suggestions for injecting hot water into iron-rich rocks to stimulate hydrogen generation, similar to enhanced geothermal energy production.
Artificial Intelligence and Hydrogen Exploration
Modern emerging science fields, such as Artificial Intelligence (AI), are revolutionizing every sector, including the exploration of natural hydrogen. Researchers working at Ohio State University have been working on a deep-learning algorithm capable of scanning the Earth's surface and subsurface areas to detect the presence of natural hydrogen.
Scientists utilized the algorithm to assist in identifying potential locations of ovoids or semicircular depressions in the ground, commonly found near areas associated with natural or 'gold hydrogen' deposits.
Despite these circular patterns often being present in low-elevation regions and concealed by agriculture or vegetation, recent discoveries in the United States, Mali, Namibia, Brazil, France, and Russia have revealed a higher abundance of these circles than previously believed.
The project discovered that AI exhibits a 'unique ability' to map surface indications of potential subsurface hydrogen reservoirs internationally and establish a foundation for further exploration of hydrogen-associated sites.
The cost of producing natural hydrogen from the ground is expected to be less than $1 per kilogram. This is significantly lower than the cost of producing green hydrogen derived from water by electrolysis, which is around $5 per kilogram.
In the modern world and in efforts to promote sustainability, cost is a major factor. The sustainable cost of extracting natural hydrogen and its emission-free availability make it a top contender for future energy needs.
References and Further Reading
Coy, P. (2023). A Gold Mine of Clean Energy May Be Hiding Under Our Feet. [Online] The New York Times. Available at: https://www.nytimes.com/2023/02/27/opinion/hydrogen-natural-climate-change.html [Accessed 18 December 2023].
Hand, E. (2023). Hidden Hydrogen. [Online] Science. Available at: https://www.science.org/content/article/hidden-hydrogen-earth-may-hold-vast-stores-renewable-carbon-free-fuel [Accessed 15 December 2023].
Office of Energy Efficiency & Renewable Energy. (2017). Hydrogen: A Clean, Flexible Energy Carrier. [Online] U.S. Department of Energy Available at: https://www.energy.gov/eere/articles/hydrogen-clean-flexible-energy-carrier [Accessed 19 December 2023].
Ozin, G. (2023). Uncovering Hidden Reserves of Natural Hydrogen. [Online] Advanced Science News. Available at: https://www.advancedsciencenews.com/uncovering-hidden-reserves-of-natural-hydrogen/ [Accessed 16 December 2023].
The Engineer. (2023). AI helps pinpoint hidden sources of underground 'gold hydrogen'. [Online] The Engineer. Available at: https://www.theengineer.co.uk/content/news/ai-helps-pinpoint-hidden-sources-of-underground-gold-hydrogen [Accessed 14 December 2023].
U.S. Geological Survey. (2023). The Potential for Geologic Hydrogen for Next-Generation Energy. [Online] U.S. Geological Survey. Available at: https://www.usgs.gov/news/featured-story/potential-geologic-hydrogen-next-generation-energy [Accessed 17 December 2023].
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