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.

Groundwater contamination with fluoride poses a significant global health challenge, critically affecting over one-third of the population in the north western state of Rajasthan, India. This study investigates the possibility of using magnesite, a readily available mineral in the area, as a cost-effective and locally producible option for removing fluoride. We investigated the fluoride adsorption capabilities of magnesite samples, subjected to various treatments including heat treatment at 600 °C, cold-plasma treatment, and coating with aluminium hydroxide to enhance their adsorption efficiency. The results showed that both heat-treated and cold-plasma treated magnesite had excellent abilities to remove fluoride. The cold-plasma treated samples had the highest adsorbent capacity, reaching a maximum of 9.92 mg/g at pH 9. The adsorption effectiveness of both untreated and modified magnesite was continuously high within the pH range of 5–10. It is discovered that at pH values lower than or equivalent to the point of zero charge, the capacity to remove fluoride remains mostly unchanged. This implies that the primary aspect contributing to fluoride removal is mainly due to non-specific adsorption mechanisms including columbic forces. These favorable results suggest that, while the modified magnesite demonstrates marginally improved performance, the raw magnesite powder may offer greater cost-effectiveness. © 2024 The Authors

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.

Fracture-mechanical properties of the sedimentary rocks at elevated temperature strongly control hydraulic fracturing in rocks, geothermal energy extraction, deep tunnelling, and spent fuel disposal in geological medium. This paper investigates the relationship between the strength properties (e.g. tensile strength, brittleness index and Young’s modulus) and the pure-mode and mixed-mode fracture toughness of Dholpur sandstone at temperatures ranging from room temperature to 500 °C. A suitable brittleness index definition was identified to quantify the deformational changes. Additionally, evolution of the stress–strain behaviour, change in the degradation degree (DD), peak strain, and evolution in porosity values were closely studied to comment on the potential brittle–ductile transition of the rock. The fracture toughness remained unchanged between 25–150 °C, sharply increased 3%–28% between 150–200 °C, and followed by a 75%–80% decrease from 200–500 °C. All the pure- and mixed-mode fracture toughness were found to maintain an exponential relationship with the Young’s modulus, tensile strength, and brittleness index of the heat-treated rocks across all the temperatures. A potential brittle to quasi-brittle/semi-ductile transition temperature of 225 °C was identified for Dholpur sandstone. Additionally, mixed mode fracture behaviour of the heat-treated rock was investigated using generalized maximum tangential stress (GMTS) criterion. It was noticed that GMTS is far better at predicting the ratio of mode-II fractures than the conventional maximum tangential stress (MTS) criterion. Statistical analysis of the test data indicate that a 3-parameter Weibull function can be successfully employed to predict the mode-II fracture toughness of heat-treated sandstone in terms of the mode-I data.

This study evaluates large-scale solar-powered green hydrogen production in Rajasthan, India, leveraging its strong solar resources and supportive policy framework. Two electricity supply pathways—Concentrating Solar Power (CSP) and a Detailed Photovoltaic Model (DPVM)—were assessed in combination with Proton Exchange Membrane Electrolyzers (PEMEL) and Alkaline Water Electrolyzers (AWEL) for a 600 tonnes-per-day (TPD) facility. System designs were optimized using the System Advisor Model (SAM). Results indicate that the DPVM-AWEL configuration achieves the lowest Levelized Cost of Hydrogen (LCOH) at USD 5.96/kg, outperforming CSP-based configurations. Sensitivity analysis identifies electrolyzer efficiency and battery storage as key cost drivers. Despite favorable conditions, current LCOH remains above India's break-even target of USD 2/kg, indicating a need for technological innovation and policy support. A 600 TPD plant could abate approximately 2.53 million tonnes of CO2 annually by displacing gray hydrogen and natural gas, highlighting Rajasthan's strong potential as a green hydrogen production hub. © 2025 Elsevier B.V., All rights reserved.