Design of an underground compressed hydrogen gas storage

Hydrogen has received significant attention throughout the past decade as the United States focuses on diversifying its energy portfolio to include sources of energy beyond fossil fuels. In a hydrogen economy, the most common use for hydrogen is in fuel cell vehicles. Advancements in on-board storage devices, investment in hydrogen production facilities nation-wide, development of a hydrogen transmission infrastructure, and construction of hydrogen fueling stations are essential to a hydrogen economy. This research proposes a novel underground storage technique to be implemented at a hydrogen fueling station. Three boreholes are drilled into the subsurface, with each borehole consisting of an outer pipe and an inner pipe. Hydrogen gas (H2) is stored in the inner tube, while the outer pipe serves to protect the inner pipe and contain any leaked gas. Three boreholes of varying pressures are necessary to maintain adequate inventory and sufficient pressure while filling vehicles to full tank capacity. The estimated cost for this storage system is $2.58 million. This dollar amount includes drilling and completion costs, steel pipe costs, the cost of a heavy-duty hydrogen compressor, and miscellaneous equipment expenses. Although the proposed design makes use of decades’ worth of experience and technical expertise from the oil and gas industry, there are several challenges—technical, economic, and social—to implementing this storage system. The impact of hydrogen embrittlement and the lack of a hydrogen transmission infrastructure represent the main technical impediments. Borehole H2 storage, as part of a larger hydrogen economy, reveals significant expenses beyond those calculated in the amount above. Costs related to delivering H2 to the filling station, electricity, miscellaneous equipment, and maintenance associated with hydrogen systems must also be considered. Public demand for hydrogen is low for several reasons, and significant misperceptions exist concerning the safety of hydrogen storage. Although the overall life-cycle emissions assessment of hydrogen fuel reveals mediocre results, a hydrogen economy impacts air quality less than current fossil-fuel systems. If and when the U.S. transitions to a hydrogen economy, the borehole storage system described herein is a feasible solution for on-site compressed H2 storage.