Activated-carbon hydrogen storage offers a promising pathway for near-ambient, safe hydrogen storage without high-pressure vessels or cryogenic equipment. However, adsorption is highly exothermic, and desorption is endothermic, creating severe thermal challenges that reduce usable storage capacity and charging rates. This study addresses that bottleneck through detailed transient modeling of coupled heat and mass transfer in a vertical steel reactor packed with activated carbon and surrounded by an external heat-transfer fluid (HTF) jacket.
Researchers developed a comprehensive numerical model solving mass, momentum, and energy balances across three domains: the porous carbon bed, the steel wall, and the circulating HTF. Four heat-transfer fluids were tested during adsorption (water, thermal oil, air, and helium) under identical operating conditions. Water emerged as the most effective cooler, holding peak bed temperature to 376.5 K while achieving hydrogen uptake of 22.5 mmol/g—an 18.4% gain over air cooling. Thermal oil delivered a 10.5% improvement. Gaseous HTFs (air and helium) proved inferior, generating peak temperatures around 395–397 K and yielding only 19.0 mmol/g with air.
During desorption, thermal oil supplied heat most efficiently to the bed, whereas gaseous fluids created pronounced cold cores due to low sensible heat capacity. The findings reveal that liquid HTFs—with their superior thermal conductivity and heat capacity—fundamentally outperform gases in managing the energy swings inherent to adsorption-based hydrogen storage.
These results provide quantitative guidance for equipment designers selecting HTFs and configuring external jacket systems. For near-ambient hydrogen storage to compete commercially with compression or cryogenic alternatives, thermal management cannot be an afterthought. The study demonstrates that intelligent fluid selection and jacket geometry can unlock significantly higher storage density, directly improving the economics and practicality of activated-carbon systems for industrial, mobility, and grid-scale applications.
