Guha Roy, Debanjan

The underground hydrogen storage represents a promising long-term, large-volume solution for hydrogen and hydrogen-methane blends, which is crucial for the anticipated “hydrogen economy” in South Asia. The suitability of any storage location hinges on its capacity and the associated costs of storage. This study provides a comparative analysis of the storage capacities for green hydrogen across fifty-nine porous geological reservoirs in India, Bangladesh, Pakistan, and Sri Lanka— the four major South Asian economies. The levelized cost of hydrogen storage (LCHS) was calculated for pure hydrogen storage in these basins. Additionally, the storage capacities of the five largest basins from India, Bangladesh, and Pakistan were evaluated for hydrogen-methane blends at 25%, 50%, and 75% concentrations. The findings indicate that South Asia's total pure hydrogen storage capacity is 29,799.43 TWh, with India contributing over 75%. Furthermore, hydrogen-methane blends were found to store more energy than pure hydrogen, with a 75% hydrogen blend storing over 65% more energy in the same basin. The primary cost factors for hydrogen storage in South Asia are compressor costs, followed by the costs of working gas and well construction. Under the parameters considered, the LCHS in India, Bangladesh, Pakistan, and Sri Lanka are $2.01, $1.28, $1.2, and $2 per kilogram of injected hydrogen.

Molecular simulations are efficient tools in differentiating individual effects of fluid-fluid interactions and pore-fluid interactions on thermophysical properties of confined fluids; e.g. the molecular packing, adsorption mechanics and availability of accessible pore volume for confined fluids and therefore, indicate the rock fracturing phenomena as a function of geological conditions, fracking fluids nature, its composition and rock mineralogy. Presently, we have deployed the classical GCMC molecular simulations to quantify the adsorption of pure nitrogen and N2–H2O mixture (50%–50% and 30%–70%) inside porous silica rocks. While we found that adsorption and molecular packing of pure nitrogen inside silica slit pores are only a function of pore height, which quantifies the pore-fluid interactions; however, for N2–H2O mixture adsorption and molecular packing of N2 inside silica slit pores has been additionally affected by the water content in the equilibrium bulk mixture that as well describes fluid-fluid interactions inside pores. It is interestingly noted that water in N2–H2O mixture results in water-assisted nitrogen adsorption inside hydrophilic silica slit pores, which has been further proven through the radial distribution function data calculations inside each slit pore. Also, the hydrophilic nature of silica increases water adsorption and hence reduces N2 adsorption inside the smallest pore of H = 20 Å. Such a reduction in N2 adsorption density below its bulk density without layering effect, inside 20 Å pore, further initiates the possibility of negative excess adsorption density.