Hydrogen is emerging as an environmentally sound alternative to fossil fuels, but transport and storage infrastructure challenges remain to be resolved. Here is where coal might play a helpful role, according to University of Pennsylvania researchers, who have studied the feasibility of large-scale hydrogen storage in coalbed formations.

Depleted coalbed methane reservoirs may be the best candidates. Similarly, injecting hydrogen into coal would cause the gas to absorb or stick to the coal. These formations often have a layer of shale or mudstone on top that keeps methane, or in this case hydrogen, sealed until it is needed and pumped back out.

Eight types of coals from U.S. coalfields were evaluated to gauge their hydrogen sorption and diffusion potential. All samples displayed considerable sorption properties, with low-volatile bituminous coal from eastern Virginia and anthracite coal from eastern Pennsylvania performing the best in laboratory tests. As reported in Applied Energy, anthracite and semi-anthracite coals were judged good candidates for hydrogen storage in depleted coal seams, and low-volatile bituminous coal are better suited for storage in gassy coal seams.

The researchers will next focus on the dynamic diffusivity and dynamic permeability of coal, features which determine how quickly hydrogen can be injected and pumped back out.